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The mineralogy and major element geochemistry of ferromanganese crusts and nodules from the northeastern… Wade, Lowell 1991

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THE MINERALOGY AND MAJOR ELEMENT GEOCHEMISTRY OF FERROMANGANESE CRUSTS AND NODULES FROM THE NORTHEASTERN EQUATORIAL PACIFIC OCEAN By LOWELL W A D E A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF T H E REQUIREMENTS FOR T H E D E G R E E OF MASTER OF SCIENCE in T H E F A C U L T Y OF G R A D U A T E STUDIES (Department of Oceanography) We accept this thesis as conforming to the required standard T H E UNIVERSITY OF BRITISH COLUMBIA April 1991 © Lowell Wade, 1991 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of ^ y ^ t P ^ ^ f ^ The University of British Columbia Vancouver, Canada DE-6 (2/88) i i ABSTRACT A study of the mineralogy and major element geochemistry of ferromanganese crusts and nodules from the northeastern equatorial Pacific Ocean involved three inter-related projects: ft) the major element geochemistry of crusts and nodules from two study areas, (2) the development of a selective sequential extraction scheme (SSES) and a differential X-ray diffraction technique (DXRD) for the study of the mineralogy of the deposits, and (3) the application of the SSES and D X R D to a small population of crusts and nodules from the two study areas. The objectives of the first project were to relate the composition of the crust and nodule samples to the environment of formation as well as to the mineralogy which could be identified from a bulk powdered sample. The SSES was developed to determine the partitioning of Cu, Ni, and Co concentrations between the Mn and Fe oxides present in crusts and nodules. In developing a SSES, two goals had to be attained: (1) since crust and nodule samples are finite in size and numerous different analyses are to be preformed on a single sample, a SSES should be developed which uses as small amount of sample as feasible, and (2) develop a SSES which is as time efficient as possible. The development of the DXRD in conjuction with the SSES identified which Mn and Fe oxide mineral phase was responsible for hosting Cu, Ni, and Co. In developing the DXRD procedure two other goals had to be attained: (1) use of small leached samples, and (2) recovery of the sample aafter X R D analysis. The purpose of the third project was to test the two analytical procedures on a group of crust and nodule samples which have a wide range in compositions and oxide phase mineralogies. One group of hydrothermal nodules, from Survey Region B, was found to be enriched in Mn and depleted in Fe and Si. The Mn-rich mineral phases were identified as todorokite and birnessite. The second group of hydrothermal nodules, from Survey Region B, was found to be enriched in Fe and Si and depleted in Mn. The Fe-Si rich mineral phase was identified as iron-rich nontronite. Both groups of hydrothermal nodules were depleted in Co, Cu, and Ni. Dymond et al. (1984) and Chen & Owen (1989) identified one group of hydrothermal nodules located close to the East Pacific Rise (EPR) as being enriched in Fe but depleted in Mn, Cu, Ni, and Co. This composition agrees with the Fe-Si rich hydrothermal nodules identified in Survey Region B. Both Dymond et al. (1984) and Chen & Owen (1989), however, interpreted a second group of nodules, close to the EPR, which were enriched in Mn but depleted in Cu, Ni, and Co as suboxic diagenetic deposits. This group of nodules is the Mn-rich end-member composition of hydrothermal nodules identifed in this study. The composition of nodules from Survey Region B indicates there is a correlation between Co abundance and the proximity of the nodules to the hydrothermal discharge from theJEPR. Nodules that are Co-enriched are found farthest away from hydrothermal activity. In contrast, cobalt-depleted nodules coincide with known areas of hydrothermal activity. The SSES and DXRD was applied to a small population of crusts and nodules from the two Survey Regions. The DXRD patterns from the second stage of leaching on the crusts and nodules showed that the iron phase mineralogy in marine crusts and nodules is either akaganeite or ferrihydrite. The D X R D patterns from the second stage of leaching on the Mn-rich hydrothermal crusts and nodules, from Survey Region B, identified the Mn-bearing mineral hausmannite. i i i T A B L E OF CONTENTS Page Title Page i Abstract ii Table of Contents iii List of Figures x Lists of Tables xx CHAPTER 1 THE GEOCHEMISTRY OF FERROMANGANESE CRUSTS AND NODULES FROM THE CENTRAL AND EASTERN NORTH EQUATORIAL PACIFIC 1 1.1 INTRODUCTION 2 1.1.1 PREVIOUS WORK 2 1.1.2 STATEMENT OF T H E PROBLEM 4 1.2 SELECTION OF STUDY AREAS 5 1.2.1 SELECTION OF SAMPLES 5 1.2.2 REGIONAL SETTING 10 1.2.2.1 Line Island Arichipelago 10 1.2.2.2 East Pacific Rise 14 1.2.2.3 Abyssal Seafloor Between the CCFZ 14 1.2.3 M O R P H O L O G Y AND T E X T U R E 16 1.3 A N A L Y T I C A L METHODS 18 1.3.1 GEOCHEMISTRY 18 1.3.1.1 Sample Preparation 18 1.3.1.2 Calibration 20 1.3.1.3 Experimental Conditions 20 1.3.1.4 Precision and Accuracy 21 1.3.2 MINERALOGY 26 1.3.2.1 Sample Preparation 26 i v 1.3.2.2 Experimental Conditions 27 1.3.2.3 Precision 28 1.4 RESULTS AND DISCUSSION 30 1.4.1 SURVEY REGION A 30 1.4.1.1 Crusts 30 1.4.1.1.1 Mineralogy 30 1.4.1.1.2 Bulk Composition 33 1.4.1.1.3 Interelement Associations 33 1.4.1.1.3.1 Correlations with Aluminium 33 1.4.1.1.3.2 Phosphorite 38 1.4.1.1.3.3 Correlations with Manganese and Iron 41 1.4.1.1.4 Variations with Depth 48 1.4.1.1.4.1 Correlations with Manganese and Iron 48 1.4.1.1.4.2 Correlations with Manganese Phase Mineralogy 58 1.4.1.1.5 Correlations with Latitude 61 1.4.1.2 Nodules 62 1.4.1.2.1 Mineralogy 62 1.4.1.2.2 Bulk Compostion 62 1.4.1.2.3 Interelement Associations 66 1.4.1.2.3.1 Correlations with Aluminium 66 1.4.1.2.3.2 Phosphorite 70 1.4.1.2.3.3 Correlations with Manganese and Iron 75 1.4.1.2.3.3.1 Complex Correlations Between Cobalt with Manganese and Iron 86 1.4.1.2.3.3.2 Correlations of Copper with Nickel 89 1.4.2 SURVEY REGION B 92 1.4.2.1 Crusts 92 1.4.2.1.1 Mineralogy 92 1.4.2.1.2 Bulk Compostion 92 1.4.2.1.3 Interelement Associations 96 1.4.2.1.3.1 Correlations with Aluminium 96 1.4.2.1.3.2 Correlations with Calcium 100 1.4.2.1.3.3 Correlations with Manganese 107 1.4.2.1.3.4 Correlations with Iron 113 1.4.2.1.4 Correlation Between Cobalt Abundance and Distance from the EPR 113 1.4.2.2 Nodules 117 1.4.2.2.1 Mineralogy 117 1.4.2.2.2 Bulk Compostion ." 120 1.4.2.2.3 Interelement Associations 122 1.4.2.2.3.1 Correlations with Aluminium 122 1.4.2.2.3.2 Phosphorite 127 1.4.2.2.3.3 Correlations with Manganese 127 1.4.2.2.3.4 Correlations with Iron 136 1.4.2.2.3.5 Identification of the Two Groups of Hydrothermal Nodules 145 1.4.2.2.4 Variations with Depth 147 1.4.2.2.4.1 Behaviour of Manganese and Iron 147 1.4.2.2.4.2 Behaviour of Cobalt 154 1.5 REFERENCES 156 1.6 APPENDIX A THE LOCATION OF CRUST AND NODULE SAMPLES FROM SURVEY REGION A 166 1.7 APPENDIX B THE LOCATION OF CRUST AND NODULE SAMPLES FROM SURVEY REGION B 170 1.8 APPENDIX C THE CONCENTRATIONS OF THE MAJOR ELEMENTS AND THE TODOROKITE/5Mn02 RATIOS FOR CRUST AND NODULE SAMPLES FROM SURVEY REGION A 175 v i 1.9 APPENDIX D THE CONCENTRATIONS OF THE MAJOR ELEMENTS AND THE TODOROKITE/5Mn02 RATIOS FOR CRUST AND NODULE SAMPLES FROM SURVEY REGION B 186 CHAPTER 2 DEVELOPMENT OF A SELECTIVE SEQUENTIAL EXTRACTION SCHEME AND A DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE TO DETERMINE THE CHEMICAL PARTITIONING OF Mn, Fe, Cu, Ni, AND Co BETWEEN THE MANGANESE AND IRON OXIDE PHASE MINERALOGY IN FERROMANGANESE CRUSTS AND NODULES 201 2.1 INTRODUCTION 202 2.1.1 REVIEW OF PREVIOUS WORK 202 2.1.1.1 Selective Dissolution of Manganese and Iron Oxides in Soils and Sediments 202 2.1.1.2 Selective Sequential Extraction Schemes for Soils and Sediments 203 2.1.1.3 Selective Dissolution of Manganese and Iron Oxides in Crusts and Nodules 204 2.1.1.4 Differential X-Ray Diffraction 209 2.1.2 STATEMENT OF PROBLEM 211 2.2 A N A L Y T I C A L METHODS AND RESULTS 212 2.2.1 EFFECTIVENESS OF SELECTED REAGENTS 212 2.2.1.1 Reagents Used 212 2.2.1.2 Experimental Conditions 213 2.2.2 ANALYSIS OF T H E LEACHATES 216 2.2.2.1 Calibration 216 2.2.2.2 Sample Preparation 216 2.2.2.3 Determining the Effectiveness of Each Reagent 222 2.2.3 D E V E L O P M E N T OF T H E TWO STAGE LEACHING P R O C E D U R E 223 2.2.3.1 First Stage of the Selective Sequential Extraction Scheme 223 v i i 2.2.3.2 Second Stage of the Selective Sequential Extraction Scheme 226 2.2.3.3 Analysis of the Leachates 226 2.2.3.4 Precision and Accuracy 228 2.2.4 D E V E L O P M E N T OF DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE 233 2.2.4.1 Sample Preparation 233 2.2.4.2 Eperimental Conditions 234 2.2.4.3 Production of a D X R D Diffractogram 235 2.2.4.3.1 Smoothing the Data 235 2.2.4.3.2 Equation of DXRD Pattern 236 2.2.4.3.3 Plotting the Tracing 239 2.2.4.4 Description of the D X R D Results 239 2.3 DISSCUSION AND CONCLUSIONS 262 P R E F E R E N C E S 264 2.5 APPENDIX A THE WEIGHT PERCENT Mn, Fe, Cu, Ni, AND Co IN THE LABORATORY STANDARD CRUST AS DETERMINED FROM THE LEACHATES 268 2.6 APPENDIX B PERCENT Mn, Fe, Cu, Ni, AND Co REMOVED FROM THE LABORATORY STANDARD CRUST 273 2.7 APPENDIX C THE SAVITZKY & GOLAY (1964) SMOOTHING PROGRAM TRANSLATED INTO GW BASIC 278 CHAPTER 3 THE APPLICATION OF THE SELECTIVE SEQUENTIAL EXTRACTION SCHEME AND THE DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE TO A SMALL POPULATION OF CRUSTS AND NODULES FROM THE NORTHEAST EQUATORIAL PACIFIC OCEAN 282 3.1 INTRODUCTION 283 3.1.1 PREVIEW 283 3.1.2 STATEMENT OF T H E PROBLEM 283 v i i i 3.2 SELECTION OF SAMPLES 284 3.3 ANALYTICAL METHODS 287 3.4 RESULTS 287 3.4.1 BACKGROUND GEOCHEMISTRY AND MINERALOGY 287 3.4.1.1 Survey Region A 290 3.4.1.1.1 Crusts 290 3.4.1.1.2 Nodules 290 3.4.1.2 Survey Region B 302 3.4.1.2.1 Crusts 302 3.4.1.2.2 Nodules 323 3.4.2 SELECTIVE SEQUENTIAL EXTRACTION AND DXRD : 333 3.4.2.1 Survey Region A 333 3.4.2.1.1 First Stage of the Selective Sequential Extraction Scheme and DXRD 339 3.4.2.1.2 Second Stage of the Selective Sequential Extraction Scheme and DXRD 352 3.4.2.2 Survey Region B 365 3.4.2.2.1 First Stage of the Selective Sequential Extraction Scheme and DXRD 365 3.4.2.2.2 Second Stage of the Selective Sequential Extraction Scheme and DXRD 376 3.5 DISCUSSION 401 3.5.1 MANGANESE OXIDES IDENTIFIED IN CRUSTS AND NODULES 401 3.5.1.1 Todorokite 408 3.5.1.2 Birnessite 409 3.5.1.3 SMn0 2 412 3.5.1.4 Hausmannite 417 i x 3.5.2 IRON OXIDES IDENTIFIED IN CRUSTS AND NODULES 420 3.5.2.1 Akaganeite 421 3.5.2.2 Ferrihydrite 424 3.6 REFERENCES 428 CHAPTER 4 SUMMARY OF PRINCIPAL RESULTS 432 4.1 RESULTS FROM CHAPTER 1 433 4.1.1 REGIONAL VARIATIONS IN THE GEOCHEMISTRY OF CRUSTS AND NODULES 433 4.1.1.1 Survey Region A 433 4.1.1.2 Survey Region B 439 4.2 RESULTS FROM CHAPTER 2 442 4.2.1 SELECTIVE SEQUENTIAL EXTRACTION SCHEME 442 4.2.2 DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE 444 4.3 RESULTS FROM CHAPTER 3 448 4.4 REFERENCES 451 X L I S T O F F I G U R E S P a g e F i g u r e 1-1. T h e l o c a t i o n o f the t w o S u r v e y R e g i o n s w i t h i n t h e n o r t h e a s t e r n e q u a t o r i a l P a c i f i c O c e a n ( m o d i f i e d f r o m G l a s b y etal, 1987) 6 F i g u r e 1-2. L o c a t i o n o f c r u s t a n d n o d u l e s a m p l e s f r o m w i t h i n S u r v e y R e g i o n A ( m o d i f i e d f r o m C h a s e et al, 1970) 8 F i g u r e 1-3. L o c a t i o n o f c r u s t a n d n o d u l e s a m p l e s f r o m w i t h i n S u r v e y R e g i o n B ( m o d i f i e d f r o m C h a s e et al, 1970) 11 F i g u r e 1-4. A t y p i c a l X R D p a t t e r n o f a cru s t f r o m S u r v e y R e g i o n A 31 F i g u r e 1-5. T h e r e l a t i o n s h i p b e t w e e n A l a n d o t h e r m a j o r e l e m e n t s . T h e o p e n c i r c l e s = s a m p l e s f r o m the H a w a i i a n I s l a n d A r c h i p e l a g o , t h e f i l l e d c i r c l e s = s a m p l e s f r o m t h e L i n e I s l a n d A r c h i p e l a g o 35 F i g u r e 1-6. T h e c o r r e l a t i o n b e t w e e n C a a n d P. T h e o p e n c i r c l e s = s a m p l e s f r o m the H a w a i i a n I s l a n d A r c h i p e l a g o , the f i l l e d c i r c l e s = s a m p l e s f r o m t h e L i n e I s l a n d A r c h i p e l a g o 3 9 F i g u r e 1-7. T h e a s s o c i a t i o n o f m a j o r e l e m e n t s w i t h M n / F e . T h e o p e n c i r c l e s = s a m p l e s f r o m the H a w a i i a n I s l a n d A r c h i p e l a g o , t h e f i l l e d c i r c l e s = s a m p l e s f r o m the L i n e I s l a n d A r c h i p e l a g o 42 F i g u r e 1-8. T h e c o r r e l a t i o n b e t w e e n M n a n d those e l e m e n t s t h a t a r e a s s o c i a t e d w i t h M n a n d w a t e r d e p t h . T h e o p e n c i r c l e s = s a m p l e s f r o m the H a w a i i a n I s l a n d A r c h i p e l a g o , t h e f i l l e d c i r c l e s = s a m p l e s f r o m the L i n e I s l a n d A r c h i p e l a g o 49 x i Figure 1-9. The correlation between Fe and those elements that are associated with Fe and water depth. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago 53 Figure 1-10. The profile of the 0 2 concentration in seawater at Geosecs Station 235 56 Figure 1-11. Correlation between manganese phase mineralogy and water depth. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago 59 Figure 1-12. A typical XRD pattern of a nodule from Survey Region A ; 63 Figure 1-13. The relationship between Al and other major elements. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 67 Figure 1-14. The correlation between Ca and P. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 71 Figure 1-15. An XRD pattern of a nodule with high Ca and P concentraions 73 Figure 1-16. The association of major elements with Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 76 Figure 1-17. Correlation between manganese phase mineralogy and Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 80 Figure 1-18. The crystal structure of todorokite. (Turner etal, 1982) 83 Figure 1-19. Complex association of Co with Mn and Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 87 X l l Figure 1-20. Correlation between Cu/Ni and Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 90 Figure 1-21. A typical XRD pattern of a crust from Survey Region B 93 Figure 1-22. The relationship between Al and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts 97 Figure 1-23. An XRD pattern of a crust with high concentrations of Fe and Si and low concentrations of trace elements 101 Figure 1-24. The relationship between Ca and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts 103 Figure 1-25. A typical XRD pattern of a crust with high concentrations of Ca, Si, and Mg 105 Figure 1-26. The relationship between Mn and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts 108 Figure 1-27. An XRD pattern of a crust which is enriched in Mn ( > 30 weight per cent) I l l Figure 1-28. The relationship between Fe and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts 114 Figure 1-29. A typical XRD pattern of a nodule from Survey Region B 118 x i i i Figure 1-30. The relationship between Al and other major elements. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules 123 Figure 1-31. The correlation between Ca and P. The open circles = hydrogenous and diagenetic nodules, the filled . circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules 128 Figure 1-32. An X R D pattern of a nodule with high Ca and P concentraions 130 Figure 1-33. The relationship between Mn and other major elements. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules 132 Figure 1-34. An X R D pattern of a nodule which is enriched in Mn ( > 30 weight per cent) 137 Figure 1-35. The relationship between Fe and other major elements. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules 139 Figure 1-36. An X R D pattern of a nodule with high concentrations of Fe and Si and low concentrations of trace elements 143 Figure 1-37. The correlation between Mn and those elements that are associated with Mn and water depth. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules 148 xiv Figure 1-38. The profile of the 0 2 concentration in seawater at Geosecs Station 343 152 Figure 2-1. Calibration curves of the elements Mn, Fe, Cu, Ni, and Co in various reagents. The open circles = Mn, the filled circles = Fe, the open triangles = Cu, the filled triangles = Ni, the open squares = Co 218 Figure 2-2. The XRD diffraction pattern of the laboratory standard crust DODO 14 DZ 240 Figure 2-3. The XRD diffraction pattern of the laboratory standard nodule Mn 191 6-8 242 Figure 2-4. The XRD diffraction pattern of the laboratory standard crust DODO 14 D Z after the first stage of the sequential extraction scheme 244 Figure 2-5. The XRD diffraction pattern of the laboratory standard nodule Mn 191 6-8 after the first stage of the sequential extraction scheme 246 Figure 2-6. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the laboratory standard crust DODO 14 DZ 248 Figure 2-7. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the laboratory standard nodule Mn 191 6-8 251 Figure 2-8. The XRD diffraction pattern of the laboratory standard crust DODO 14 D Z after the second stage of the sequential extraction scheme 253 Figure 2-9. The XRD diffraction pattern of the laboratory standard nodule Mn 191 6-8 after the second stage of the sequential extraction scheme 255 X V Figure 2-10. The D X R D pattern obtained after the second stage of leaching of the sequential extraction scheme on the laboratory standard crust DODO 14 D Z 257 Figure 2-11. The D X R D pattern obtained after the second stage of leaching of the sequential extraction scheme on the laboratory standard nodule Mn 191 6-8 259 Figure 3-1. The association of Cu, Ni, and Co with Mn/Fe in hydrogenetic crusts from Survey Region A 291 Figure 3-2. The XRD patterns of hydrogenetic crusts selected for the two stage selective sequential extraction scheme 294 Figure 3-3. The association of Cu, Ni with Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 297 Figure 3-4. The complex association of Co with Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules 300 Figure 3-5. The X R D patterns of hydrogenous nodules selected for the two stage selective sequential extraction scheme 303 Figure 3-6. The XRD patterns of diagenetic nodules selected for the two stage selective sequential extraction scheme 306 Figure 3-7. The relationship between Mn with Cu, Ni, and Co. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts 309 Figure 3-8. The XRD patterns of hydrogenetic crusts selected for the two stage selective sequential extraction scheme 312 x v i Figure 3-9. The XRD patterns of Mn-enriched hydrothermal crusts selected for the two stage selective sequential extraction scheme 316 Figure 3-10. The X R D pattern of a Mn-depleted hydrothermal crust enriched in Fe and Si 319 Figure 3-11. The relationship between Fe and Co. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts 321 Figure 3-12. The relationship between Mn with Cu, Ni, and Co. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules 324 Figure 3-13. The X R D patterns of the hydrogenous and diagenetic nodules selected for the two stage selective sequential extraction scheme 327 Figure 3-14. The X R D patterns of the Mn-enriched hydrothermal nodules selected for the two stage selective sequential extraction scheme 330 Figure 3-15. The X R D patterns of the Mn-depleted hydrothermal nodules selected for the two stage selective sequential extraction scheme 334 Figure 3-16. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the manganese phase mineralogy which was removed during the first stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = hydrogenous nodules, the open triangles = diagenetic nodules 340 Figure 3-17. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenetic crusts 343 x v i i Figure 3-18. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenous nodules 346 Figure 3-19. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the diagenetic nodules 349 Figure 3-20. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the iron phase mineralogy which was removed during the second stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = hydrogenous nodules, the open triangles = diagenetic nodules 353 Figure 3-21. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenetic crusts 356 Figure 3-22. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenous nodules 359 Figure 3-23. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the diagenetic nodules 362 Figure 3-24. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the manganese phase mineralogy which was removed during the first stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the open triangles = hydrogenous and diagenetic nodules, the filled triangles = Mn-enriched hydrothermal nodules, the open squares = Mn depleted hydrothemal nodules 370 Figure 3-25. The DXRD pattern obtained after the the filled first stage of leaching of the sequential extraction scheme on the hydrogenetic crusts 373 x v i i i Figure 3-26. The D X R D pattern obtained after the first stage of leaching of the the sequential extraction scheme on the Mn-enriched hydrothermal crusts 377 Figure 3-27. The D X R D pattern obtained after the first stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal nodules 380 Figure 3-28. The D X R D pattern obtained after the first stage of leaching of the sequential extraction scheme on the Mn-depleted hydrothermal nodules 383 Figure 3-29. The D X R D pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenous and diagenetic nodules 386 Figure 3-30. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the iron phase mineralogy which was removed during the second stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the open triangles = hydrogenous and diagenetic nodules, the filled triangles = Mn-enriched hydrothermal nodules, the open squares = Mn depleted hydrothemal nodules 389 Figure 3-31. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenetic crusts 392 Figure 3-32. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal crusts 395 xix Figure 3-33. The D X R D pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenous and diagenetic nodules 398 Figure 3-34. The D X R D pattern obtained after the second stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal nodules 402 Figure 3-35. The D X R D pattern obtained after the second stage of leaching of the sequential extraction scheme on the Mn-depleted hydrothermal nodules 405 Figure 3-36. The crystal structure of todorokite (Turner etal., 1982) 410 Figure 3-37. The crystal structure of birnessite (Giovanoli & Briitsch, 1979) 413 Figure 3-38. The crystal structure of 5Mn02 (modified from Giovanoli et al., 1965) 415 ) Figure 3-39. The crystal structure of hausmannite (Murray, 1979) 418 Figure 3-40. The crystal structure of akaganeite. 1 = Mn, 2 = oxygen, 3 = Ba, K, Pb, Na, or H 2 0 (Murray, 1979) 422 Figure 3-41. The crystal structure of ferrihydrite (modified from Eggleton & Fitzpatrick, 1988) 425 XX LIST OF TABLES Page Table 1-la. Precision of the method of analysis between samples 22 Table M b . Precision of the XRF 23 Table 1-2. Comparison of analytical results with best estimates of two ferromanganese nodule reference standards. Results are given as weight percentages 25 Table l-3a. Precision of the method of analysis between sample 29 Table l-3b. Precision of the XRD 29 Table 1-4. Mean concentrations of major elements in crusts from Survey Region A. Concentrations are given in weight per cent 34 Table 1-5. Comparison of the composition of aluminosilicates in crusts to Average Pacific Pelagic Clay and Tholeiitic Lavas from the Hawaiian Islands 37 Table 1-6. Mean concentrations of major elements in nodules from Survey Region A. Concentrations are given in weight per cent 65 Table 1-7. Comparison of the composition of aluminosilicates in nodules to Average Pacific Pelagic Clay and Tholeiitic Lavas from the Hawaiian Islands 69 Table 1-8. Mean concentrations of major elements in crusts from Survey Region B. Concentrations are given in weight per cent 95 Table 1-9. Comparison of the composition of aluminosilicates in crusts to Average Pacific Pelagic Clay and Mid-Ocean Ridge Basalts 99 Table 1-10. Mean concentrations of major elements in nodules from Survey Region B. Concentrations are given in weight per cent Table 1-11. Comparison of the composition of aluminosilicates in nodules to Average Pacific Pelagic Clay and Mid-Ocean Ridge Basalts The mean composition of the laboratory standard crust DODO 14DZ. Mean concentrations are given as weight per cents Instrumental setting for analysis of the five metals on the atomic absorption spectrophotometer The effectivness of 0.25M N H o O H H C l in 0.01M H N O 3 and 0.175M Ammonium Oxalate in 0.1M Oxalic Acid. Results are listed as the per cent of Mn and Fe removed from the laboratory standard crust DOD014DZ. The mean composition of the laboratory standard nodule Mnl91 6-8. Mean concentraions are given as weight per cents Table 2-5a. Concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the first stage of the two stage selective sequential extraction scheme. Results are given as weight per cents Table 2-5b. Concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the second stage of the two stage selective sequential extraction scheme. Results are given as weight per cents and have been adjusted to be comparable to the first stage of leaching Table 2-6a. Precision of the method of analysis for the first stage of the two stage selective sequential extraction scheme. Replicate samples are from the laboratory standard crust DODO 14DZ. Concentrations are given as weight per cents Table 2-1. Table 2-2. Table 2-3. Table 2-4. x x i i Table 2-6b. Precision of the method of analysis for the second stage of the two stage selective sequential extraction scheme. Replicate samples are from the laboratory standard crust DODO 14DZ. Concentrations are given as weight per cents Table 2-6c. Precision of the Atomic Absorbtion Spectrometer as determined by the absorbances of the standard 5ppm... 229 230 Table 2-7. Comparison of the total amount of Mn, Fe, Cu, Ni, and Co removed from the laboratory standard crust and nodule by the two stage selective sequential extraction scheme compared to the XRF results used to determine precision of the XRF. Results are given as weight per cents 232 Table 2-8. Comparison of the d-spacings (A) of the two iron oxides identified in this study to those listed in the JCPDS card index 261 Table 3-la. Location and depth of crust and nodule samples selected from Survey Region A for analysis. The location and depth of these samples are also shown in Figure 1-2 in Chapter 1 285 Table 3-lb. Location and depth of crust and nodule samples selected from Survey Region B for analysis. The location and depth of these samples are also shown in Figure 1-3 in Chapter 1 286 Table 3-2a. The major element compostion of the bulk crust and nodule samples selected from Survey Region A. Results are listed as weight per cent 288 X X 1 1 1 Table 3-2b. The major element compostion of the bulk crust and nodule samples selected from Survey Region B. Results are listed as weight per cent 289 Table 3-3a. The concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the first stage of leaching for samples from Survey Region A. Results are listed as weight per cent 337 Table 3-3b. The mineral phase(s) removed during the first stage of the selective sequential extraction scheme and identified by DXRD. 337 Table 3-4a. The concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the second stage of leaching for samples from Survey Region A. Results are listed as weight per cent 338 Table 3-4b. The mineral phase(s) removed during the second stage of the selective sequential extraction scheme and identified by DXRD. 338 Table 3-5a. The concentrations of Mn, Fe, Cu, Ni and Co in the leachates from the first stage of leaching for samples from Survey Region B. Results are listed as weight per cent 366 Table 3-5b. The mineral phase(s) removed during the first stage of the selective sequential extraction scheme and identified by DXRD. 367 Table 3-6a. The concentrations of Mn, Fe, Cu, Ni and Co in the leachates from the second stage of leaching for samples from Survey Region B. Results are listed as weight per cent 368 Table 3-6b. The mineral phase(s) removed during the second stage of the selective sequential extraction scheme and identified by DXRD. 369 CHAPTER 1 THE GEOCHEMISTRY OF FERROMANGANESE CRUSTS AND NODULES FROM THE CENTRAL AND EASTERN NORTH EQUATORIAL PACIFIC 2 1.1 INTRODUCTION 1.1.1 PREVIOUS WORK Ferromanganese crusts and nodules from the Central and Eastern North Equatorial Pacific have been studied to a greater extent than those from any other ocean. Initial interests within this area were focused on abyssal ferromanganese nodules (hereafter called nodules) from the Eastern Equatorial Pacific. The first systematic study of nodules from this area were recovered from the WAHINE Survey Region (1965) (Moore & Heath, 1966). This was later followed by the International Decade of Ocean Exploration (IDOE) during which three projects were conducted. These are the MANOP (1974-1975) (Margolis & Burns, 1976), DOMES (1975-1976), (Sorem et al, 1979), and the International Cooperative Investigations of Manganese Nodule Environments (I.C.M.E) Project (1978) (Friedrich et al, 1983). Also during this time West Germany investigated a number of small survey regions within this area. These survey regions include: P (1971), VA-04 (1972) (Roonwal & Friedrich, 1980), VA-05/1 (1973), VA-08/1 (1974) (Friedrich et al, 1977), VA-13/1 and VA-13/2 (1976) (Marchig & Gundlach, 1979; Glasby et al, 1982), and VA-18 (1978) (von Stackelberg, 1982). The first ferromanganese crusts (hereafter called crusts) sampled from the Central North Equatorial Pacific were recovered from the Hawaiian Archelago by Moore (1965). Attention was later drawn to these crusts as potential resources of strategic metals, specifically cobalt, when in 1978 the Shaba Province of Zaire (formerly Katanga in the Belgian Congo) was invaded by Angola and Zambia. This caused the price of cobalt to peak and reflects the fact that Zaire (Shaba province) is the world's largest producer of cobalt. Unlike the mining of abyssal nodules, which is complicated by their location in international waters, most of the cobalt-rich crusts 3 occur within the exclusive economic zone of the United States and other nations (Manheim, 1986). Since then a number of cruises have collected crusts from the Hawaiian Archipelago, the Line Island Archipelago, and the Mid Pacific Mountains. The first detailed and systematic study was that of the German MIDPAC-1 Expedition (1981) (Halbach & Manheim, 1984). This was followed by the U.S. Geological Survey R/V "S.P. LEE" Expedition (1983) (Hein et al, 1985a) and again by the German MIDPAC-2 Expedition (1984) (Mangini et al, 1987). A number of shorter cruises have also examined crusts from this region. These include cruises by the U.S Geological Survey to Johnston Island (1986) and by the University of Hawaii to the Hawaiian Archipelago (1984) and to the Line Island Archipelago (1986 and 1987) (Hein et al, in press a). Examination of the results of these cruises shows that crusts and nodules have wide compositional variations throughout the Central and Eastern North Equatorial Pacific. This variable geochemistry is related to a combination of factors which include the availability and chemical behaviour of elements in the marine environment, the adsorptive and crystallo-chemical properties of the authigenic mineral phases, and their rate of formation (Cronan, 1980). Environmental parameters also control crust and nodule geochemistry. These environmental parameters are: 1) The form of the deposit, either as a crust or nodule; 2) The environment of deposition, either on top of a seamount or on the abyssal sea floor; 3) The lithology of the substrate; and 4) The water depth. It should be noted that these environmental parameters do not act independently of one another (Frazer & Fisk, 1981). Three sources of metals contribute to the formation of crusts and nodules. This means that there is a continuous range in composition from an hydrogenetic end member to a diagenetic end member. Crusts located on the tops of seamounts and other topographic highs grow only in contact with ambient seawater. Crusts, 4 therefore, form by the direct precipitation of ferromanganese oxyhydroxide colloids from seawater (Lyle et al., 1977). They, therefore, represent the purely hydrogenetic end member (Apbn & Cronan, 1985a). In basin regions, at a distinct distance from seamounts, two types of nodules coexist. Smaller nodules that are embedded in the uppermost "peneliquid" layer of the sediment. These nodules are formed by diagenetic remobilization of elements within the sediment column. They represent the purely diagenetic end member (Aplin & Cronan, 1985b). Larger nodules, with a distinct equatorial zone which divides the nodules into two distinct sections, are formed by hydrogenetic and diagenetic processes (Halbach et al., 1980; 1981a,b). These nodules have been termed hydrogenous by Hein et al. (In Press b). As noted by Moore & Vogt (1976) and by Elderfield & Greaves (1981), the rate of formation of crusts and nodules associated with mid-ocean ridge crests is too rapid to be explained by hydrogenetic precipitation. Since ridge crest sediments are oxidizing throughout the sedimentary column, it is also unlikely that they are formed by diagenetic processes (Lyle, 1976). Crusts and nodules closely associated with mid-ocean ridge crests therefore represent the purely hydrothermal end member (Bonatti etal., 1972). 1.1.2 STATEMENT OF THE PROBLEM In this paper we examine a suite of crust and nodule samples recovered form the Central and North Equatorial Pacific Ocean. Calvert & Price (1977a) and Halbach et al. (1981b) have shown that crusts and nodules from different topographic provinces within the Central and Eastern Equatorial Pacific Ocean have varied and distinct compositions. This varied and distinct geochemistry is probably controlled by different mechanisms of formation, availability of constituent elements, and the adsorptive and crystallo-chemical properties of the authigenic mineral 5 phases. It is also probably controlled by the environmental parameters. The major element geochemistry and manganese phase mineralogy the suite of crust and nodule samples has been determined and will be compared and contrasted with work previously done within this region of the Pacific Ocean. Although the two survey regions discussed here are much larger than those of other authors, a comparison between this work and similar studies within the same survey regions will be attempted. 1.2 SELECTION OF STUDY AREAS 1.2.1 SELECTION OF SAMPLES The crust and nodule samples used in this study were obtained from the collections at the Scripps Institution of Oceanography (SIO). From this collection, 167 samples were selected. Based on sample density, the Central and Equatorial North Pacific Ocean was divided into two survey regions (Figure 1-1). Survey Region A extends from the Hawaiian Island Archipelago at 21°N to the Equator and from the Line Island Archipelago at 170°W to 140°W. Samples from this region include nodules recovered from the abyssal sea floor located between the CCFZ and crusts from the Line Island Archipelago. The bathymetry and the location of crust and nodule samples within Survey Region A are shown in Figure 1-2. The precise location and depth of samples recovered from this area are listed in Appendix A. Survey Region B is the larger of the two survey areas. It extends from 26°N to 5°N and from the eastern edge of Survey Region A at 140°W to the crest of the East Pacific Rise at 100°W. Samples from this region include nodules recovered from the abyssal seafloor North and South of the Clarion Fracture Zone as well as crusts 6 Figure 1-1. The location of the two Survey Regions within the northeastern equatorial Pacific Ocean (modified from Glasby et al., 1987). 8 Figure 1-2. Location of crust and nodule samples from within Survey Region A (modified from Chase et al., 1970). 9 10 recovered from the East Pacific Rise, Henderson Seamount, and the Suitcase Seamounts. The bathymetry and the location of crust and nodule samples within Survey Region B are shown in Figure 1-3. The precise location and depth of samples recovered from this area are listed in Appendix B. 1.2.2 REGIONAL SETTING 1.2.2.1 Line Island Archipelago The origin of the Line Island Archipelapo and the Mid Pacific Mountains is genetically related to basaltic volcanism during the Late Cretaceous (Halbach & Puteanus, 1984a). Clague (1981) stated that the first basaltic eruption in this area probably occurred 100 to 106Ma. Jackson & Schlanger (1976) proposed that the entire region underwent synchronous volcanism which uplifted the pre-existing shields into shallow water prior to 80 to 85Ma. The islands were covered by shallow water carbonate sediments before about 70 to 80Ma. Between 50 to 60Ma the islands probably began to submerge and the epoch of intense volcanism ended (Halbach & Puteanus, 1984a). The former islands continued to subside through the remainder of the Cretaceous and Tertiary with the deposition of pelagic calcareous ooze. From the Middle Miocene to the Late Pliocene (about 12Ma), a period of non-deposition or erosion took place as a result of increased bottom current activity (Nishimura, 1981). This event is related to the development of a large ice cap on Antarctic and the resulting flow of Antarctic bottom water (AABW) (van Andel et al, 1975). From the Late Pliocene onwards, siliceous clay sediments were deposited within the Central Equatorial North Pacific Basin along with calcareous ooze on seamounts above the CCD (Halbach et al, 1982). 11 Figure 1-3. Location of crust and nodule samples from within Survey Region B (modified from Chase et al., 1970). 12 13 The bathymetry of the Line Island Archipelago is characterized by high relief seamounts and seamount chains (Mangini et al., 1987). The water depth varies between 1100 to 4900m and the CCD varies from 4700m in the south to 4200m in the north (Halbach & Puteanus, 1984b). The tops of the seamounts are often flat (guyots), which resulted from subsiding post-volcanic marine or subaerial conditions. Typical cliff-and-terrace structures exist on the flanks of the seamounts. Crusts are common on seamount slopes and summit plateaus between 3000 to 1000m water depth. Crusts accumulate on unsedimented surfaces of seamount regions of the Line Island Archipelago and the Hawaiian Archipelago. Crusts precipitate primarily on nuclei or substrates of alkali basalt and it's alteration products which consist of montmorillonite and phillipsite; hyaloclastites with fragments of highly vesicular basaltic rock; yellowish-green smectitic rocks; indurated phosphorite, formed by replacement of calcareous ooze; and occasionally claystone. Other clay minerals such as illite or kaolinite often make up a significant fraction of the substrate. While basaltic volcanics contribute minor amounts of olivine, magnetite and/or maghemite, ilmenite (?), and hematite (?) to the bulk composition of crusts, quartz is probably contributed by eolian transport from continental land masses (Frank et al., 1976). On plateaus and flat terraces, nodules lie on top of partly consolidated calcareous sediments. Broken crusts and rock fragments in these regions provide nucleii for the formation of nodules. The AABW or other deep-water currents are sufficiently strong to prevent accumulation of pelagic material and promote hydrogenetic nucleation of crusts on substrate rocks. 14 1.2.2.2 East Pacific Rise The East Pacific Rise (EPR) stands about 2 to 4km above the adjacent ocean bottom and varies from 2000 to 4000km in width. The EPR shows less bathymetric relief than other spreading ridges and has no prominant median valley along its crest, due to its rapid spreading rate of 6 to 10cm per year (Kennett, 1982). Hydrothermal solutions resulting from the convective circulation of seawater through newly emplaced basaltic crust (Corliss, 1971) supply dissolved metals to bottom seawater (Bostrom & Peterson, 1966). Upon mixing with cold oxygenated seawater the F e ^ + and M n ^ + present in the hydrothermal fluids oxidize and precipitate to form the Mn-Fe-rich sediments associated with mid-ocean spreading ridges (Skornyakova, 1964; Bostrom & Peterson, 1966; Bonatti et al., 1972). The sediments associated with the EPR have been described as brown, X-ray amorphous metal oxide precipitates. Rather than being coatings or impregnations of other mineral grains, they are separate, very finely-disseminated or loosely aggregated materials (Bostrom & Peterson, 1966). 1.2.2.3 Abyssal Seafloor Between the CCFZ The tectonic history and bathymetric relief of the abyssal seafloor between the C C F Z is directly related to seafloor spreading from the EPR (Craig, 1979). The age of the oceanic crust increases from the EPR to 20Ma at 115°W and to 75Ma at 150°W. A shift of the spreading centre from the Mathematicians Ridge to the EPR appears to have occurred sometime between 14 to 3Ma (van Andel & Heath, 1973). The bathymetry of this region is dominated by abyssal hills which are 50 to 200m in height (Andrews & Friedrich, 1979). These small scale features are generally elongated parallel to the crest of the EPR (Andrews et al., 1977). The formation of 15 these features is a result of a combination of tensional, block faulting, and volcanic activity during the generation of oceanic crust at the EPR (Luyendyk, 1970). Andrews (1971) and van Andel et al. (1973) recognized variations in structural alignment and microtopographic relief on these abyssal hills and suggested that tectonic activity continues to modify these features at distances away from the EPR. The C C F Z originated as transform faults offsetting the EPR and are typically complex zones of ridges, basins, and seamounts on the order of 100km in width (Craig & Andrews, 1978). Subsidence of the cooling oceanic crust, formed at the EPR, has led to generally increasing regional water depths from 4000m at the western flank of the Mathematicians Ridge to about 5000m in the western part of the C C F Z (von Stackelberg, 1988). The CCD within the C C F Z ranges in depth from 4800m in the south to 4400m in the north (Berger et al, 1976; Heath et al, 1977; Piper et al, 1979). From the Cretaceous to the Early Oligocene, sedimentation within the CCFZ was governed mainly by the circumequatorial circulation through both the Atlantic and Pacific Oceans (Keller & Barron, 1983). The opening of the Drake Passage towards the end of the Oligocene to Early Miocene (25-20Ma) and the closing of the passage of Central America near the Early Middle Miocene (16-15Ma) resulted in the interruption of the circumequatorial circulation and the introdution of AABW. This caused a switch in deposition of silica from the Atlantic to the Pacific Ocean and in stronger deep sea erosion (von Stackelberg, 1988). Various factors influence the distribution of sediment facies within the CCFZ. These have been listed by von Stackelberg (1988) as being: 1) the biogenic productivity zone parallel to the equator; 2) the C C F Z downthrown to the north; 3) the overall inclination of the seafloor to the west and the N-S orientation of the abyssal hills; and 4) the deflection to the south of the AABW by these abyssal hills. The distance of the CCFZ from the equatorial productivity zone and its increasing 16 water depth, which lies below the CCD, causes increasing dissolution of calcareous tests and results in a decreasing biogenic input to the sediments within the CCFZ (von Stackelberg, 1988). This, combined with the intensified AABW which passes northeastwards through the Line Island Archipelago and spreads over the abyssal seafloor within the CCFZ (Gordon & Gerard, 1970) has resulted in low sedimentation rates of l-4mm/Ka (Theyer, 1977; Meyer, 1977). The main sediment facies of the CCFZ is, therefore, older outcropping siliceous oozes interfingered with pelagic clays. These sediment facies sometimes underlie a thin veneer of Pliocene-Quaternary sediments (von Stackelberg, 1988). 1.2.3 M O R P H O L O G Y AND T E X T U R E The samples used in this study were classified as either crusts or nodules based on their morphology, location, and depth. When the samples were selected from the SIO collections, a description of the sample's morphology was briefly noted. The morphological classification follows that of Raab & Meylan (1977) which divides ferromanganese deposits into four categories. These categories are: 1) stains, 2) agglutinations, 3) nodules, and 4) crusts. Stains are very thin deposits on some solid object such as a volcanic rock fragment or outcropping rock. Aggultinations are clusters of discrete nuclie united by a thin encrustation, generally less than 1mm thick. Nodules are thicker encrustations surrounding a single or multiple discrete nuclei. Crusts are relatively thick deposits on submarine rock outcrops or large boulders or volcanic slabs. There is one problem with this classification. No accepted distinction between objects that are stained or very thinly encrusted and objects that may be called nodules has been defined. Samples selected from the SIO collections were chosen so that there would be no doubt as to their being either a crust or a nodule. Nodules were further classified based on their surface texture as 17 described by Raab (1972), namely, smooth, gritty, "goose bumps", and pisolitic or knobby. Nodules with a smooth surface texture show essentially no visible pattern. Often these smooth surfaces develop black lustrous patches. Nodules with a gritty surface texture appear to be composed of sand-sized and finer particles which are loosely cemented to the nodule. These particles are often associated with a surface texture which is best described as being composed of "goose bumps". A surface which can be described as being composed of "goose bumps" is characterized by many small welts. These welts may represent internal growth structures. Pisolitic or knobby nodules have developed a distinct equatorial zone characterized by a knobby surface texture. This zone appears to be composed of fused grains larger than 2mm, hence the name pisolitic. Further refinement of the classification was based on their location and water depth. Crusts occur on hard substrates on the flanks of seamounts, islands, plateaus, and other topographically positive areas in the Pacific (Hein et al., 1987). The distribution of crusts within the Central and Eastern Equatorial North Pacific can, therefore, be related to two tectonic settings: they can occur on the flanks of seamounts, plateaus, and islands (mid-plate volcanic chains) such as those of the Line Island Archipelago, at depths less than 2500m and along oceanic spreading axes such as the East Pacific Rise (Hein et al., 1987; Hein et al., in press a). Nodules occur on unconsolidated sediments in abyssal water depths from 4000-5000m (Calvert, 1978; Exon, 1983). The distribution of nodules within the Central and Eastern Equatorial North Pacific is, therefore, confined to an east-west belt on the abyssal seafloor confined by the CCFZ (Halbach et al., 1981b). 18 1.3 ANALYTICAL METHODS 1.3.1 GEOCHEMISTRY The wide range in compositional variability of crusts and nodules makes routine analysis far from straightforward. In addition, in order to understand the mechanisms leading to the formation of crusts and nodules, multielement analysis of a relatively large number of samples is required. Thus X-ray fluorescence spectrometry (XRF) was selected as the analytical method to determine the major element geochemistry of the crust and nodule samples. X-Ray fluorescence is capable of routinely and precisely determining a wide range of elements in a large number of samples in relatively short time periods (Calvert et al., 1985). 1.3.1.1 Sample Preparation As demonstrated by Harvey et al. (1973), sample preparation of geological materials using fusion methods involving a relatively high dilution and addition of a heavy absorber as a means of matrix correction offer the best means of achieving a high degree of accuracy and precision in XRF analyses. Samples prepared by this method, unlike undiluted powdered samples, do not suffer the problems of absorption and enhancement effects that require empirical matrix corrections. To determine the major element geochemisty of crusts and nodules, Calvert et al. (1985) describes a modification of the method developed by Harvey et al. (1973). The powdered samples are diluted with a flux, having the following composition L i 2 B 4 0 7 47.03%, L i C 0 3 36.63%, L a 2 0 3 16.34%. The lanthanum, in the flux, is used as a heavy adsorber of X-rays and as a means of matrix correction (Norrish & Hutton, 1969). The flux used is commercially available as Spectroflux® 19 105 (Johnson and Matthey, Ltd). Crusts and nodules contain low concentrations of silica and alumina, which prevents a stable glass being formed on fusion. The addition of a known weight of Specpure® SiC»2 (Johnson and Matthey, Ltd) to the crust and nodule samples results in the production of stable glass beads. The powdered sample (0.3000g), Specpure® S i 0 2 (O.lOOOg), and Spectroflux® 105 (3.6000g) are sequentially weighed into a Pt-Au crucible and heated in an electric muffle furnace at 1100°C for 15 minutes. After the crucible has been removed from the furnace, it is allowed to cool to room temperature in an aluminum cooling block. The weight loss on fusion is made up by adding dried Li2B4C»7 (Spectroflux® 100). This compensates for the variable weight loss of individual samples and maintains the same degree of dilution of the sample and the same ratio to La to the major elements in the sample. After reweighing, the crucible containing the cooled glass and added tetraborate is placed over a Meeker® burner in a fume hood and the mixture remelted. The melt is quickly poured into an aluminium platten on a hot-plate maintained at 250°C and a brass plunger, at the same temperature, is brought down over the melt for a few seconds to form a flat bead. After removing the plunger, the platten with its bead is moved to the side of the hot-plate, covered with an inverted evaporating dish and the bead allowed to anneal for at least 10 minutes. The bead is finally cooled by moving the platten to a heat-resistant surface, after which it readily comes away from the platten. The bead is labelled on the bottom surface and stored in a plastic bag together with the excess glass fragments which are trimmed from the edges using a cleaned pair of needle-nose pliers. The fragments are retained for re-casting should the bead crack or break. 20 1.3.1.2 Calibration The use of well-analyzed standards for the analysis of crusts and nodules is not possible because no such samples are available. Abbey (1983) has listed a few oxide ore and laterite standards but none has been analyzed for a full range of elements. A trustworthy consensus of values for their constituent elements, therefore, has not been obtained. This problem with the lack of standards which can be used for the analysis of crusts and nodules was solved by Calvert et al. (1985). They developed a series of synthetic calibration standards for the XRF. The standards were made by preparing mixtures of Specpure® oxides, or appropriate salts, and a well-characterized aluminosilicate. The aluminosilicate selected as the diluent was the standard granite NIM-G which is listed in Abbey (1983). A 50:50 mixture of M n 0 2 and Fe2C>3 was first prepared. Half of this mixture was then doped with accurately weighed amounts of all other elements of interest and the mixture homogenized by shaking with methyl acrylate mixing balls on a mechanical blender. Thirteen standards were then produced by mixing weighed portions of the Mn02-Fe2C>3 mixture and NIM-G with the doped oxide mixture. Sub-samples of the standards were then made into glass beads for major element calibration of the XRF. The compositions of the standards are listed in Calvert et al. (1985). 1.3.1.3 Experimental Conditions The crust and nodule samples along with the thirteen standards were analyzed by a Philips® PW 1400 wavelength-dispersive sequential automatic spectrometer. The operating conditions and relevant count-rate data are listed in Calvert et al. (1985). A Rh-target X-ray tube was used for analysis of all major elements. The 21 measurement of backgrounds in samples having high dilution and an added heavy adsorber is commonly not done (Norrish & Hutton, 1969). There was, however, sufficient variations in the background over the full range of compositions measured to make background measurements necessary for all major elements. Fixed time counting and the ratio method were also employed. The ratio method uses a sample of intermediate composition (one of the calibration standards) as a reference against which all measurements are ratioed to correct for instrument drift. The choice of crystals was made with regard to convenience and speed of the analytical program, problems of interferences, crystal fluorescence, and peak resolution. Finally, the appropriate pulse-analyzer settings were determined for each element determined. The spectrometer was controlled by a DEC® PDT-11 microcomputer and up to 72 samples loaded at a time on an automatic sample changer. After setting up all measurement and control parameters in the PW 1400 microprocessor through the PDT-11 microcomputer, element calibrations were determined on the calibration standards and stored on floppy disc. Major element intensities and final concentrations were then available immediately after an individual sample was run. 1.3.1.4 Precision and Accuracy The precision of the methods for the determination of the major elements was obtained by analyzing the laboratory crust and nodule standards DODO 14DZ and Mn 191 6-8. Five sub-samples were prepared from each well mixed bulk sample. The sample precision includes errors due to the inherent inhomogeneity of the samples, sample handling and weighing, and the manufacture of the glass beads. In addition one of the calibration standards, chosen randomly, was analyzed five times in order to determine an estimate of the instrumental precision. The results are shown in Table 1-la and b. The sample precision was found to vary from 0.00% up Table 1-la. Precision of the method of analysis between samples. Laboratory Standard Crust DODO 14DZ Element Replicate No. 1 2 3 4 5 Mean S.D. CV. (%) Si 9.46 6.24 6.10 5.22 5.25 6.54 1.75 27.13 Ti 1.13 1.17 1.17 1.17 1.15 1.16 0.02 1.72 Al 1.77 1.92 1.84 1.86 1.83 1.84 0.05 2.72 Fe 15.23 15.91 15.47 15.66 15.49 15.55 0.25 1.61 Mn 12.27 13.08 12.47 12.60 12.22 12.53 0.34 2.71 Mg 0.95 1.00 1.06 1.02 0.96 1.00 0.05 5.00 Ca 2.72 2.83 2.78 2.82 2.72 2.77 0.06 2.17 Na 1.55 1.72 1.36 1.65 1.54 1.56 0.14 8.97 K 0.76 0.76 0.76 0.73 0.74 0.75 0.01 1.33 P 0.65 0.68 0.67 0.68 0.65 0.67 0.02 2.99 Co 0.30 0.30 0.30 0.30 0.30 0.30 0.00 0.00 Ni 0.15 0.15 0.15 0.15 0.16 0.15 0.00 0.00 Cu 0.06 0.07 0.05 0.06 0.04 0.06 0.01 16.67 Zn 0.03 0.03 0.04 0.04 0.04 0.04 0.01 25.00 Ba 0.13 0.13 0.12 0.13 0.13 0.13 0.00 0.00 Laboratory Standard Nodule Mn 191 6-8 Element Replicate No. 1 2 3 4 5 Mean S.D. CV. (%) Si 7.07 7.39 6.55 7.40 7.57 7.20 0.40 5.55 Ti 0.35 0.36 0.36 0.35 0.35 0.35 0.00 0.00 Al 2.96 2.85 2.98 2.94 2.95 2.94 0.05 1.70 Fe 5.35 5.36 5.36 5.34 5.37 5.36 0.01 0.19 Mn 28.19 28.07 28.42 28.18 28.42 28.26 0.16 0.57 Mg 3.34 3.18 3.76 3.48 3.91 3.53 0.30 8.50 Ca 1.42 1.41 1.40 1.41 1.41 1.41 0.01 0.71 Na 0.10 0.50 0.26 0.06 0.12 0.21 0.18 85.71 K 0.94 0.92 0.88 0.91 0.89 0.91 0.02 2.20 P 0.21 0.21 0.21 0.20 0.21 0.21 0.00 0.00 Co 0.18 0.17 0.19 0.18 0.18 0.18 0.01 5.55 Ni 1.50 1.40 1.31 1.44 1.48 1.43 0.07 4.89 Cu 1.46 1.34 1.23 1.45 1.45 1.37 0.10 7.30 Zn 0.14 0.12 0.11 0.13 0.13 0.13 0.01 7.69 Ba 0.30 0.29 0.29 0.29 0.29 0.29 0.00 0.00 Table 1-lb. Precision of the XRF. XRF Standard #1 (See Calvert et al., 1985) Element Repeat Analysis. 1 2 3 4 5 Mean S.D. CV. (%) Si 5.90 5.77 5.96 5.91 5.74 5.86 0.01 1.70 Ti 0.70 0.70 0.71 0.70 0.69 0.70 0.01 1.43 Al 2.24 2.24 2.29 2.26 2.27 2.26 0.02 1.43 Fe 22.15 22.24 22.24 22.15 22.15 22.19 0.05 0.23 Mn 21.74 21.66 21.74 21.81 22.05 21.80 0.15 0.69 Mg 1.32 1.34 1.31 1.30 1.23 1.30 0.04 3.08 Ca 2.21 2.18 2.16 2.17 2.06 2.16 0.06 2.78 Na 0.55 0.42 0.55 0.60 0.50 0.52 0.07 13.46 K 0.73 0.75 0.72 0.70 0.68 0.72 0.03 4.17 P 0.09 0.09 0.09 0.09 0.10 0.09 0.00 0.00 Co 1.06 1.09 1.15 1.16 1.26 1.16 0.06 5.17 Ni 1.12 1.09 1.15 1.16 1.26 1.16 0.06 5.17 Cu 0.88 0.83 0.85 0.90 0.97 0.89 0.05 5.62 Zn 0.11 0.10 0.09 0.11 0.11 0.10 0.01 10.00 Ba 0.29 0.31 0.27 0.27 0.31 0.29 0.02 6.89 2 4 to 85.17% (coefficient of variation). In most cases the sample precision is greater than the instrumental precision. The coefficient of variation (CV.) is a measure of the standard deviation which is independant of the sample mean. This allows for the comparison of the same element between sample and instrumental precision or to compare the precision between different elements (Snedecor & Cochran, 1956; Zar, 1974). Those elements with poorer precision are the result of the inherently lower count rates of the long-wavelength radiations or because of the relatively low concentrations of the particular analytes (Calvert et al., 1985). This can be demonstrated by comparing the C V . for the same element between the two laboratory standards. In the laboratory nodule standard the abundance of Cu is much higher than in the laboratory crust standard. Even though the standard deviation (S.D.) for the standard crust is significantly lower than for the standard nodule the C V . for the standard crust (C.V.=16.67) is much higher than for the standard nodule (C.V.=7.30). As noted by Calvert et al. (1985) despite the wide ranging calibrations, no further matrix corrections were attempted. The accuracy of the methods used in determining the major element composition was checked by comparing the analytical results with the best estimates of the composition of two nodule reference standards (Table 1-2). The values of best estimates have been adjusted by the amount of F^O" reported in Tables 30 and 31 of Flanagan & Gottfried (1980) in order to make them directly comparable with the procedure used here. This comparison does show that the calibrations obtained here provide reasonable values over a wide range of compositions. Table 1-2. Comparison of analytical results with best estimates of two ferromanganese nodule reference standards. Results are given as weight percentages. Nod--A-l Nod--P-1 XRF Flanagan XRF Flanagan and and Gottfried G o t t f r i e d ELEMENT (1980) (1980) S i 2.31 1.53 6.34 6.07 T i 0.23 0.28 0.25 0.28 A l 1.77 1.77 2.25 2.38 Fe 10.15 9.43 5.62 5.38 Mn 16.32 15.99 27.16 27.17 Mg 2.73 2.47 1.86 1.85 Ca 9.88 9.51 2.03 2.04 Na 0.54 0.66 1.27 1.53 K 0.40 0.43 0.91 0.98 P 0.48 0.52 0.19 0.19 Co 0.26 0.27 0.19 0.21 Ni 0.57 0.55 1.26 1.25 Cu 0.09 0.09 1.06 1.07 Zn 0.05 0.05 0.16 0.15 Ba 0.12 0.14 0.24 0.32 26 1.3.2 MINERALOGY The mineralogy of crusts and nodules determines most of their physical and chemical properties. The constituent minerals not only control the authigenesis, growth, and structure of the nodule but they also influence the uptake of certain elements. Crusts and nodules consist of a complex mixture of different mineral crystallites both detrital and authigenic, organic and colloidal matter, and altered igneous and metamorphic rock fragments (Burns & Burns, 1977). The mineralogy of crusts and nodules is difficult to determine because of the small size of the crystallites, intimate intergrowth of authigenic phases, and the presence of amorphous material (Calvert, 1978). 1.3.2.1 Sample Preparation Sample preparation for mineral analysis is not as involved as that for geochemical analysis. The only prerequisite is that the prepared sample consist ideally of crystalline particles in completely random orientation. When the orientation of the crystalline particles in the prepared sample is truly random, all possible diffractions take place simultaneously (Hurlbut & Klein, 1977). The powdered sample is pressed into a rigid disc which is held in an aluminum sample holder. The sample is then ready for analysis by powder X-ray diffraction (XRD), after which the sample is recovered. 2 7 1.3.2.2 Experimental Conditions The prepared samples were loaded into a Philips® PW 1775 sample changer to be analyzed by a Philips X-ray diffractometer powered by a Philips® PW 1729 constant potential generator. Diffraction data were obtained using Cu Ka radiation (40kV, 20mA) with a graphite monochromator and a Philips® PW 1050/70 vertical goniometer equipped with a diffracted beam graphite monochromator, an automated divergence slit, 0.1mm receiving slit, 1° scatter slit, and a gas proportional counter. Although identification of low intensity peaks is made difficult by the high background due to the fluorescent Mn and Fe radiation, Glasby (1972) found that an iron tube was only slightly superior to the copper tube. Work was therefore completed using a copper tube. The diffractometer was controlled by a Philips® PW 1710/00 diffraction control unit. Measurement and control parameters were set up in the PW 1710/00 microprocessor through a Zenith® Z-150 personal computer using MS-DOS Kermit (Gianone et al, 1988). The XRD was used for complete scans of some samples to correlate the sample geochemistry with mineralogy as well as to determine the relative abundances of todorokite to 8Mn0 2 in all samples. Samples selected for mineral analysis were step scanned from 5° to 71°20 in 0.005°2f? increments, using a counting time of 5 seconds per increment. Diffractograms were recorded using a rate full scale of 100 counts per second, a rate time constant of 5 seconds, and a chart speed of 5rnrn/°2t9. The relative abundances of todorokite to 5Mn0 2 was estimated by measuring the net intensity of the 9.80A peak for todorokite and the 1.40A peak for 5Mn0 2 . The value obtained for todorokite was then divided by the value obtained for SMn0 2 . The net intensity of a peak was determined by collecting the total number of counts under a peak profile, in a scan. This value is divided by the total time and 28 the resulting total intensity is given in counts per second. The background is then measured at one point on each side of the peak for a preset time. This value for the background is then subtracted from the total intensity to give the net intensity of the peak. Since all calculations are done on an intensity scale, the resulting net intensity can be taken as the area of a peak above the line connecting the two background points. For todorokite, the net intensity of the 9.80A peak was determined by step scanning from 8° to 1O.6°20 in O.OO5°20 increments. The background was measured at 8° and 1O.6°20 respectively for 10 seconds each. For SMnO^ the net intensity of the 1.40A peak was determined by step scanning from 63.4° to 69°20 in O.OO5°20 increments. The background was measured at 63.4° and 69°20 respectively for 10 seconds each. 1.3.2.3 Precision The precision of the methods for the determination of the todorokite/SMnO^ ratio was obtained by analyzing a laboratory nodule standard. Ten sub-samples were prepared from a well mixed bulk sample. In addition, one of the replicates, chosen randomly, was analyzed ten times in order to provide an estimate of instrumental precision. The sample precision includes errors due to the inherent inhomogeneity of the sample, sample handling, manufacture of the pressed powder discs, poor crystallinity of the manganese mineral phases, and fortuitous orientation of the mineral crystallites. The sample precision was found to be 6.98% (coefficient of variation). The instrument precision was found to be similar to the sample precision (6.87% coefficient of variation). The results are listed in Table l-3a and b. Table l-3a. Precision of the method of analysis between sample Replicate No. Todorokite/6MnO 1 1.65 2 1.76 3 1.87 4 1.73 5 1.74 6 1.80 7 1.48 8 1.67 9 1.88 10 1.62 Sample Mean 1.72 Standard Deviation 0.12 Co e f f i c i e n t of Var i a t i o n 6.98 Table l-3b. Precision of the XRD. Repeat Analysis Todorokite/6MnO 1 1.71 2 1.72 3 1.49 4 1.57 5 1.60 6 1.54 7 1.43 8 1.58 9 1.60 10 1.80 Samlple Mean 1.60 Standard Deviation 0.11 Co e f f i c i e n t of Varia t i o n 6.87 30 1.4 RESULTS AND DISCUSSION 1.4.1 S U R V E Y REGION A 1.4.1.1 Crusts 1.4.1.1.1 Mineralogy A general idea of the average mineralogical composition of crusts from this region can be obtained by examining an XRD diffractogram of a randomly selected crust (Figure 1-4). As shown by Figure 1-4, crusts from this region are composed of 8Mn02, alunimosilicates, mostly quartz and feldspar, and carbonate fluorapatite. The todorokite to SMn02 ratio for crusts from this region varies from 0.00 to 0.91 with a mean of 0.09. This further supports the XRD evidence that the dominant manganese oxide in these crusts is 8Mn02- The X-ray powder diffractogram, shown in Figure 1-4 shows the presence of a fine-grained, poorly crystalline material, which contributes a considerable amount of background noise on which are superimposed the sharp peaks of the aluminosilicates and carbonate fluorapatite. The poorly crystalline material has been identified as being cryptocrystalline or amorphous hydrated iron oxides (Glasby, 1972; Crerar & Barns,1974). Mossbauer spectroscopic studies by Herzenberg & Riley (1969), Gager (1968), Johnson & Glasby (1969), and Carpenter & Wakeman (1973) have also led to the suggestion that the iron-bearing phase can be regarded as an amorphous ferric hydroxide or oxide-hydroxide gel ( F e O O H x H 2 0 ) with a particle size less than 200A. The identity of this phase is discussed in greater detail in chapters 2 and 3. Figure 1-4. A typical XRD pattern of a crust from Survey Region A. DODO 7 D-2 100 Carbonate Fluorapatite h 80 6MnO. Carbonate Fluorapatite h 60 Carbonate Fluorapatite 40 h 20 —i m z co o o c z H CO 05 m o O z D 80 60 I 40 DEGREES 2© 20 to 33 1.4.1.1.2 Bulk Composition The major element composition and manganese phase mineralogy data for crusts recovered from Survey Region A are listed in Appendix C. This compositional data can be used to estimate the relative proportions of the iron and manganese oxides and other phases in the crusts and help interpret inter-element associations which will be discussed later. The mean composition of crusts from this region is listed in Table 1-4 together with the average compositions of crusts from two other studies within the same area. Except for Mn and Fe, the mean composition of crusts from Survey Region A is similar to those of the other two studies. The concentrations of Mn and Fe, however, are considerably lower than those reported by Hein et al, (1987) and by Hablach & Manheim (1984). The Mn/Fe ratio of the crusts from Survey Region A is also lower than those reported for the two other studies. 1.4.1.1.3 Interelement Associations 1.4.1.1.3.1 Correlations with Aluminium The nature of the aluminosilicates in the crusts is shown by the relationships between Al and other major elements (Figure 1-5). From the X R D diffractogram, these correlations with Al could be explained by the presence of quartz and feldspar. By using Si/Al and K/Al element ratios, the origin of the aluminosilicate fraction of the crusts can be identified. The average Si/Al and K/Al ratios of crusts from this region are found to be 3.18 and 0.38, respectively (Table 1-5). Both element ratios are consistently higher than those for "Average Pacific Pelagic Clay" (Bischoff et al., 1979) and for "Average Tholeiitic Lavas from the Hawaian Islands" (Best, 1982). Table 1-4. Mean concentrations of major elements in crusts from Survey Region A. Concentrations are given in weight per cent. Mean Composition Average c e n t r a l Mean composition of Crusts from P a c i f i c crusts of a l l seamount Survey Region A (Hein et al., 1987) oxide samples (Halbach & Manheim, 1984) Element Concen. Element Concen. Element Concen. S i 5.15 S i 3.69 T i 0.89 T i 1.10 T i 0.96 A l 1.62 Fe 11.20 Fe 15.00 Fe 14.50 Mn 14.95 Mn 22.00 Mn 24.60 Mg 1.26 Ca 5.06 Ca 4.24 Na 1.55 K 0.61 P 1.40 P 0.65 P 1.24 Co 0.46 Co 0.78 Co 0.79 Ni 0.36 Ni 0.44 Ni 0.49 Cu 0.07 Cu 0.08 Cu 0.07 Zn 0.04 Zn 0.07 Ba 0.18 Mn/Fe 1.33 Mn/Fe 1.47 Mn/Fe 1.70 35 Figure 1-5. The relationship between Al and other major elements. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago. 25.00 20.00 + 15.00 + 10.00 + O 5.00-- A 0 . 0 0 ^ * ° 0.00 2.00 4.00 6.00 Al (%) O 8.00 10.00 2.50 2.00 + 8.00 10.00 Table 1-5. Comparison of the composition of aluminosilicates in crusts to Average Pacific Pelagic Clay and Tholeiitic Lavas from the Hawaiian Islands. Element Ratios S i / A l K/Al Crusts from 3.18 0.38 Survey Region A (This Study) Average P a c i f i c 2.92 0.25 Pelagic Clay (Bischoff et a l . , 1979) Average T h o l e i i t i c Lavas 3.13 0.04 from the Hawaiian Islands (Best, 1982) 38 This seems to indicate that there are several sources contributing to the aluminosilicate fraction in the crusts. Quartz and some of the plagioclase and K-feldspar are eolian in origin and reflect the position of the crust-coated seamount relative to atmospheric wind belts (Hein et al., 1985). The rest of the plagioclase, as well as K-feldspar and other aluminosilicates, are derived from the substrate, probably by resuspension of weathered material (Hein et al., 1987). Calvert & Price (1977a) estimated the total amount of aluminosilicate impurity in their nodules from the Al contents, assuming that this fraction had the same composition as that in the associated sediments. Due to the lack of a sediment substrate and the multiple sources contributing to the aluminosilicate fraction in crusts, determining the aluminosilicate content of crusts from Survey Region A is not possible. 1.4.1.1.3.2 Phosphorite Some of the crusts have high concentrations of Ca and P, and for all crusts there is a strong positive correlation between these two elements (Figure 1-6). This is a due to the presence of carbonate fluorapatite {(Ca,Mg,Na,K)^Q[(P,C)04]5(F,OH)2}. The presence of carbonate fluorapatite is shown in the X R D diffractogram of the randomly selected crust (Figure 1-4). As discussed in Halbach & Puteanus (1984a), crusts from the Line Island and the Hawaiian Archipelagoes are characterized by two generations of growth. Between the two crust generations is a period of phosphorite deposition during which formation of massive carbonate fluorapatite and impregnation of the older crust generation has taken place. Based on the results of age determinations by Halbach et al. (1983), the younger crust layer should not be older than lOMa. The period of formation of the younger crust generation corresponds with the increasing 39 F i g u r e 1-6. T h e c o r r e l a t i o n b e t w e e n C a a n d P. T h e o p e n c i r c l e s = s a m p l e s f r o m the H a w a i i a n I s l a n d A r c h i p e l a g o , t h e f i l l e d c i r c l e s = s a m p l e s f r o m t h e L i n e I s l a n d A r c h i p e l a g o . 40 1 0 . 0 0 8 .00 6.00 + 4 . 0 0 2 . 0 0 0 . 0 0 0 . 0 0 1 0 . 0 0 2 0 . 0 0 3 0 . 0 0 Ca (%) 41 current activity of the AABW initiated by a major global cooling since the middle Miocene (Kennett et al., 1975). The period of formation the older crust layer might have been during the Eocene to early Oligocene, when the first development of Antarctic glaciation at sea level and a marked stratification in the deep water, causing enhanced deep-sea erosion, took place (van Andel et al., 1975). The massive phosphorite is thought to have formed mainly by carbonate replacement between the two periods of crust growth. From Oligocene to early Miocene, sedimentation in the central Pacific was characterized by carbonate deposition (van Andel et al., 1975). The phosphorite formation probably took place between the periods of carbonate accumulation and the younger period of crust growth (Halbachetal., 1983; Halbach & Puteanus, 1984b). 1.4.1.1.3.3 Correlations with Manganese and Iron To examine the regional compositional variations with respect to Mn and Fe, the effects of the dilutant aluminosilicates and carbonate fluorapatite material must be removed (Calvert, 1978). Price & Calvert (1970) solved the problem by using element ratios instead of absolute abundances of elements to represent geochemical variations. Using the elemental ratio of Mn/Fe, the association of the major elements with either of the major oxide phases will become more apparent. Elements correlated with the manganese phase mineralogy will show a positive linear correlation with the Mn/Fe ratio. In the present case, these include Ba, Ni, Zn, and Co. Elements associated with the unidentified iron phase mineralogy show a negative correlation with the Mn/Fe ratio; these elements include Ti and Na (Figure 1-7). Hein et al. (in press a) identified the same correlations in crusts from the central Pacific. They noted that the degree of the correlations vary from area to 42 Figure 1-7. The association of major elements with Mn/Fe. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago. 0.40 0.30 + 0.20 0 . 1 0 + 0.00-0.00 1.00 2.00 3.00 4.00 1.50 0.00 1.00 2.00 3.00 4.00 Mn/Fe 1.00 0.75 * 0.50+ o o 0.25 + 0.00 0.00 4.00 u.ou - o 0.60-S 0.40- o • o CD 0.20-0.00-•o 1 1 1 o 0.00 1.00 2.00 Mn/Fe 3.00 4.00 0.15 0.10 + c IN 0.05 + 0.00 o • • o • O • • • cm 4 00 • € GD O — i _1 1 0.00 1.00 2.00 3.00 +.00 M n / F e 4.00 3.00- O 2.00+ O • ^ is. 1.00+ _ • o o.oo 0.00 •+-1.00 2.00 Mn/Fe 3.00 4.00 2.00 .50 1.00 + 0.50 + 0.00 o * 3 * ^ o 1 — : • — i 1 • 0.00 1.00 2.00 3.00 4.00 Mn/Fe 4 7 area, but three correlations remained consistent. These were Mn with Co, Si with Al, and Ca with P. The association of Si with Al and Ca with P has been explained previously. The reason for the association of Mn with Co has yet to be identified. Cobalt along with Ba, Ni, and Zn are fixed by lattice substitution for M n ^ + in the MnO^ or by coprecipitation of C 0 O 2 with manganese oxide (Hem, 1978). The reason that Co is enriched in 5MnC»2 to a greater degree than are Ni, Zn, and Ba is because C o ^ + is oxidized to C o ^ + on the surface of the MnO^. Cobalt (III) is less soluble and therefore more stable in the marine environment (Goldberg, 1954; Dillard et al., 1982; Halbach et al, 1983; Aplin & Cronan, 1985a). As noted by Aplin & Cronan (1985a) in their work on crusts from the Line Island Archipelago, the chemical composition of crusts makes it unlikely that halmyrolytic, hydrothermal, or diagenetic processes influence the composition of the crusts. First, halmyrolysis is considered to be unimportant in supplying metals to the deposits in view of the lack of compositional similarity between the crusts and the substrate type. Secondly, the deposits exhibit none of the characteristics of hydrothermal crusts as described by Toth (1980). These characteristics include: low concentrations of Cu, Ni, and Co; extreme fractionation of Mn from Fe; and the presence of birnessite in Mn-rich hydrothermal crusts and amorphous hydrated iron oxides and silica in Fe-rich hydrothermal crusts. Thirdly, the compositional and mineralogical similarity of crusts of varying thickness indicates that both these parameters are fixed at the point of oxide accretion and that subsequent diagenesis is unimportant. Crusts derive most of their metal content from dissolved and particulate matter in ambient bottom water, in proportions modified by the variable scavenging efficiency of the manganese and iron oxide phase mineralogy for susceptible ions (Manheim & Lane-Bostwick, 1988). This model is supported by the striking 48 resemblance between the crust/seawater trace metal enrichment sequence and laboratory determined oxide-trace metal selectivity sequences (Aplin & Cronan, 1985a). 1.4.1.1.4 Variations with Depth 1.4.1.1.4.1 Correlations with Manganese and Iron Not only does there exist interelement associations in crusts from this region, but for crusts from the Hawaiian Archipelago there also exists a correlation between the major element contents and water depth. Manganese and those minor metals that are correlated with manganese (Zn, Ba, Co, Ni, and Cu) all show a decrease in concentration with increasing water depth (Figure 1-8), while those elements that show a correlation with iron (Na, and Ti) all show an increase in concentration with increasing water depth (Figure 1-9). To understand the correlation between crust geochemistry and water depth, the source of constituent elements must be identified. Halbach & Puteanus (1984b) have proposed that the main Fe source for hydrogenetic crusts of this region is colloidal Fe-hydroxide particles that are released in the water column from the dissolution of carbonate plankton skeletons. On the other hand, the source of Mn to hydrogenetic crusts evidently cannot be derived souly from this same source. They concluded that a further source of Mn enrichment following carbonate dissolution is necessary, and this is supplied via the Oxygen Minimum Zone (OMZ). The extent of the OMZ in the central equatorial Pacific and the depletion of oxygen within this zone are, shown in Figure 1-10. Geosecs Station 235 is located within Survey Region A between the Hawaiian and Line Island Archipelagoes at 16°47.3'N and 161°22.9'W. Based on the oxygen profile at this site, the O M Z within 49 Figure 1-8. The correlation between Mn and those elements that are associated with Mn and water depth. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago. Mn (%) 0.00 0-10.00 20.00 30.00 O 0 0 O M Z 1 --O <3DA 3 -O O o 0 0 o o o Co (%) 0.00 0.50 1.00 4 1 GO o OMZ * o # *w o ••••• • o o o ° o GO o DEPTH (km) ho -+-O O © o o o o o o DEPTH (km) o o b o O b o o o M © » 1 1—1 1 1 • ° o • O o _^ Si. M DEPTH (km) DEPTH (km) 53 Figure 1-9. The correlation between Fe and those elements that are associated with Fe and water depth. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago. DEPTH (km) DEPTH (km) Ti (%) 55 0.00 0-0.50 1.00 1.50 2.00 5 C L Q 2-O O O O O 3 - o o o o oo o o OMZ 56 Figure 1-10. The profile of the 0 2 concentration in seawater at Geosecs Station 235. 5 8 Survey Region A lies at water depths of between 503 and 2296m, and the minimum dissolved oxygen concentration is 26/u,mole/kg. Within the OMZ there is a high concentration of dissolved Mn as a result of the in situ decomposition of organic matter along with the in situ reduction of Mn-bearing solid phases (Klinkhammer & Bender, 1980; Landing & Bruland, 1980). This zone of maximum concentration of M n ^ + produces a flux of M n ^ + by diffusion and turbulent mixing into shallower and deeper waters which have an increased ?-t-oxygen content. This causes oxidation of the Mn^"1" and results in the formation of hydrated M n 0 2 particles which are incorporated into the crusts (Halbach et al., 1988). As noted by Halbach et al. (1983), an increasing supply of Fe and its associated trace metals from the dissolution of calcite skeletons has a diluting effect on the concentration of Mn and its associated trace metals, that is the concentration of Mn and its associated trace metals should decrease with increasing water depth down to the CCD. This trend has also been observed by Halbach et al. (1983), Aplin & Cronan, (1985a), and by Hein et al. (in press b). 1.4.1.1.4.2 Correlations with Manganese Phase Mineralogy The XRD diffractogram shown in Figure 1-4 indicates that the manganese phase mineralogy in crusts from this region is dominated by SMn0 2 . Although this is the most common manganese mineral present, todorokite also occurs in low abundances. The relative abundances of todorokite and S M n 0 2 in crusts from this region also appear to show a variation with water depth (Figure 1-11). Todorokite is more abundant in crusts located within the OMZ. As discussed by Glasby (1972), the redox potential in the environment of formation of ferromanganese deposits controls the manganese phase mineralogy. The depletion of oxygen in the O M Z to values of around 26ttmole/kg results in an environment with a lower redox potential. These 59 Figure 1-11. Correlation between manganese phase mineralogy and water depth. The open circles = samples from the Hawaiian Island Archipelago, the filled circles = samples from the Line Island Archipelago. T o d / aMn0 2 0.00 0.50 1.00 0 lower redox potentials combined with the high M n z + concentrations will result in manganese oxyhydroxides being precipitated as todorokite, where the Mn^+(OH)2X2H20 layers bind sucessive [Mn^+Og] octahedra together. Below the OMZ, oxygen is,more plentiful, this results in higher redox potentials, and combined with the low concentration of Mn^ + the layers of linked [Mn^+Og] octahedra are randomly oriented and constitute the SMnC>2 phase (Burns & Burns, 1979). 1.4.1.1.5 Correlations with Latitude Although there appears to be a general correlation between crust geochemistry and water depth, crusts from the Line Island Archipelago show a very wide range in composition over a very small range in water depth (Figures 1-8 and 1-9). This variability is related to location; the concentrations of Mn, Ni, Zn, Cu, Co, and Ba decrease from the Equator towards the northwest along the Line Island Archipelago, while the concentrations of Fe, Ti, and Na increase with distance away from the Equator in the same direction. This variation in the regional geochemistry of crusts from the Line Island Archipelago has also been observed by Halbach et al. (1982) and by Halbach & Puteanus (1984b). They proposed that although this correlation is not well understood, the processes likely to control these regional trends include deep and intermediate-depth current systems, biological productivity, differences in the position of the CCD, and the degree of depletion of oxygen in and the vertical extent of the OMZ zone. 62 1.4.1.2 Nodules 1.4.1.2.1 Mineralogy In contrast to the crusts, nodules from region A are composed mainly of todorokite and aluminosilicates, mostly quartz and feldspar (Figure 1-12). The todorokite to SMnC»2 ratio for nodules from this region varies from 0.00 to 2.45 with a mean of 0.74 (Appendix C). This further supports the XRD evidence that the dominant manganese oxide in these nodules is todorokite. The XRD pattern also shows the presence of a fine-grained, poorly crystalline material, which contributes a considerable amount of background noise. Once again, the poorly crystalline material has been identified as being cryptocrystalline or amorphous hydrated iron oxides (Glasby, 1972; Crerar & Barnes, 1974). The identity of this phase will be discussed in greater detail in chapters 2 and 3. 1.4.1.2.2 Bulk Composition The major element data for nodules recovered from Survey Region A are listed in Appendix C. Again, these compositional data will be used to estimate the relative proportions of the iron and manganese oxides and other phases in the nodules and help interpret inter-element associations which will be discussed later. The mean composition of nodules from this region is listed in Table 1-6 together with the average compositions of nodules from two other studies from within the same area. Except for Fe, the average composition of nodules from Survey Region A is similar to the average composition of nodules from the other two studies. The concentration of Fe, however, is considerably lower than those reported by Cronan & Tooms (1969) and Usui & Moritani (in press). Thus, the average Figure 1-12. A typical XRD pattern of a nodule from Survey Region MN 39 100 65 Table 1-6. Mean concentrations of major elements in nodules from Survey Region A. Concentrations are given in weight per cent. Mean Composition Average c e n t r a l of Nodules from P a c i f i c nodules Survey Region A (Cronan & Tooms, 1969) Mean composition of a l l nodule samples from the Central P a c i f i c (Usui & Moritani, i n press) Element Concen. Element Concen. Element Concen. S i 7.21 S i 6.91 T i 0.63 T i 0.81 A l 2.45 A l 2.59 Fe 8.78 Fe 13.30 Fe 11.60 Mn 19.45 Mn 16.87 Mn 22.50 Mg 1.72 Ca 2.03 Na 1.52 K 0.86 P 0.32 Co 0.22 Co 0.40 Co 0.25 Ni 0.74 Ni 0.56 Ni 0.89 Cu 0.60 Cu 0.39 Cu 0.75 Zn 0.08 Zn 0.09 Ba 0.15 Ba 0.15 Mn/Fe 2.22 Mn/Fe 1.27 Mn/Fe 1.94 66 Mn/Fe ratio of nodules from this region is higher than those reported for the other two studies. 1.4.1.2.3 Interelement Associations 1.4.1.2.3.1 Correlations with Aluminium As shown by the crusts, the nature of the aluminosilicates in the nodules is shown by the relationship between Al and other major elements. For the nodules, aluminum shows a strong positive correlation with Si and K (Figure 1-13). From the X-ray diffractogram (Figure 1-12), these correlations with Al could be explained by the presence of quartz and feldspar. By using the Si/Al and K/Al element ratios, the origin of the aluminosilicate fraction of the nodules can be identified. As shown in Table 1-7, the Si/Al and K/Al ratios are 2.94 and 0.35, respectively. The Si/Al of the nodules is closely similar to that of Average Pacific Pelagic Clay as determined by Bischoff et al. (1979), rather than Average Tholeittic Lavas from the Hawaiian Islands as determined by Best (1982). The K/Al ratio, however, is much greater than either of the ratios determined by Bischoff et al. (1979) and Best (1982). This seems to indicate, just like the crusts, that there are several sources contributing to the aluminosilicate fraction in the nodules. Due to the proximity of the nodules to the crusts, the sources of aluminosilicates to the nodules should be the same as those contributing to the crusts. Almost all of the quartz and a minor proportion of the feldspars are incorporated into the nodules from the associated sediments as indicated by the Si/Al ratio of the nodules being almost identical to Average Pacific Pelagic Clay. The feldspars and the rest of the quartz are eolian in origin, and their abundance reflects the position of the nodules relative to the atmospheric wind belts (Hein etal, 1985). 6 7 Figure 1-13. The relationship between Al and other major elements. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 20.00 15.00 + 10.00 + 5.00 + 0.00 0.00 1.00 2.00 3.00 4.00 Al (%) 5.00 6.00 2.50 2.00 + 1.50 1.00 + 0.50 + 0.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 Al (%) 6 9 Table 1-7. Comparison of the composition of aluminosilicates in nodules to Average Pacific Pelagic Clay and Tholeiitic Lavas from the Hawaiian Islands. Element Ratios S i / A l K/Al Nodules from 2.94 0.35 Survey Region A (This Study) Average P a c i f i c 2.92 0.25 Pelagic Clay (Bischoff et al., 1979) Average T h o l e i i t i c Lavas 3.13 0.04 from the Hawaiian Islands (Best, 1982) 70 Calvert & Price (1977a) estimated the total amount of aluminosilicate impurity in their nodules based on the Al contents, assuming that this fraction had the same composition as that in the associated sediments. Even though there are associated sediments, they only contribute a portion of the total amount of the aluminosilicate fraction in nodules. Eolian deposition of quartz and feldspar into the ocean contributes the rest of the aluminosilicate fraction to the nodules. Because of these multiple sources of aluminosilicates in nodules, determining the aluminosilicate content of the nodules is not possible. 1.4.1.2.3.2 Phosphorite Some of the nodules are found to have high concentrations of Ca and P. Furthermore, there is a strong positive correlation between these two elements in all nodules (Figure 1-14). An XRD tracing of a nodule with high Ca and P concentrations shows that this correlation is due to the presence of carbonate fluorapatite {(Ca,Mg,Na,K)1 0[(P,C)O4]6(F,OH)2} (Figure 1-15). The formation of carbonate fluorapatite has already been discussed to explain the correlation of P with Ca in crusts from this same region. The presence of carbonate fluorapatite in nodules is possibly due to the erosion of carbonate fluorapatite from the neighbouring seamounts and its incorporation into the nodules as nuclei. 71 Figure 1-14. The correlation between Ca and P. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 4.00 3.00 2.00 + 1.00 + 0.00 + -+-0.00 2.00 4.00 6.00 Ca (%) 8.00 10.00 12.00 Figure 1-15. An XRD pattern of a nodule with high Ca and P concentraions. Mn 86 75 1.4.1.2.3.3 Correlations with Manganese and Iron Although not the first, Halbach & Ozkara (1979) used the Mn/Fe ratio as a criterion for distinguishing between different types of nodules from a small study area located within Survey Region A. They suggested that nodules with an Mn/Fe ratio less than 2.5 were predominantly hydrogenous in origin, while nodules with an Mn/Fe ratio above 2.5 were mainly diagenetic in origin. Nodules from Survey Region A can also be divided into these two groups, and there is a marked compositional distinction between them. As shown in Figure 1-16, hydrogenous nodules are depleted in Mn, Cu, Ni, Zn, Mg, and Ba compared to the diagenetic nodules whereas hydrogenous nodules are enriched in Fe and Ti compared to the diagenetic nodules. It can therefore be stated that the abundances of Cu, Ni, Zn, Mg, and Ba are correlated with Mn and that the abundance of Ti is correlated with Fe. It is interesting to note in Figure 1-16 that there is a sharp break in slope of a first order regression line drawn through the hydrogenous nodules compared to one drawn through the diagenetic nodules. For those elements that are associated with Mn (apart from Co and Zn), the slope of the regression line for the hydrogenous nodules is greater than that of the diagenetic nodules. Since inter-element correlations with manganese are related to the manganese oxides present in the nodule, a similar association should be apparent when the todorokite to 5MnC>2 ratios are plotted against the Mn/Fe ratios (Figure 1-17). This shows that todorokite is more abundant than 5Mn0 2 in diagenetic nodules compared to hydrogenous nodules. Even though the same change in the slopes of the first order regression lines is seen, almost all of the nodules contain some todorokite as indicated by the non zero values of the todorokite/5Mn02 ratios. In order to understand why there is 7 6 Figure 1-16. The association of major elements with Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. Mn/Fe 0.40 8.00 3.00 2.00 1.00 0.00 0.00 2.00 4.00 6.00 8.00 Mn/Fe 1.50 8.00 0.00 2.00 4.00 6.00 8.00 Mn/Fe 80 Figure 1-17. Correlation between manganese phase mineralogy and Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 82 a change in the slopes of a first order regression lines shown in Figure 1-17 a better understanding of the crystal structure of todorokite is needed. Todorokite is a tecktomanganate possessing a tunnel structure running parallel to the b axis. The tunnels are composed of "walls" of triple chains of edge-shared [MnO^] octahedra containing M n ^ + ions in the M l positions and M n 2 + ions in the M2 positions. "Floors" and "ceilings" of these tunnels consist of edge-shared [MnO^] octahedra, most commonly three octahedra wide with M n ^ + ions in the M3 and M4 positions (Figure 1-18) (Burns et al, 1983). These prodominant [3x3] tunnels are often intergrown with other tunnels ranging in dimension from [3x2] to [3x8] and higher (Burns et al., 1985). The very wide tunnels, obtaining dimensions of [3x oo], produce the layered structure postulated for buserite (Burns et al., 1983). In the "ceilings" of the todorokite tunnels are cation vacancies within the bands of edge-shared [Mn^+Og] octahedra which become more prevalent with wider "ceiling" dimensions. These cation vacancies not only nucleate faults, kinks, and twinning observed in the H R T E M micrographs of todorokite fibres (Turner et al., 1982), but they also influence the crystal chemistry and site occupancy of the tunnels. As a result, three types of atomic substitution contribute to the crystal chemistry of todorokite: (1) substitution of M n ^ + cations by other cations of smaller ionic radii in the "ceilings", such as low spin Cc?+ ions (Burns, 1976); (2) substitution of divalent M n 2 + ions in the "walls" by M g 2 + , N i 2 + , C u 2 + , Z n 2 + , and other cations; and (3) constituents of the tunnels (Tl and T2 positions) consist of large cations such as K + , B a 2 + , A g 2 + , C a 2 + , P b 2 + , N a 2 + , and H 2 0 molecules (Burns et al, 1983). A non-linear correlation between Ni and Cu versus the Mn/Fe ratio has also been observed by Halbach et al (1981b) in nodules from the Northeast Pacific nodule belt and by Usui & Mita (1987) in nodules from the three survey areas of SONNE Cruise SO-25 in the Northeast equatorial Pacific. Halbach et al (1981b) Figure 1-18. The crystal structure of todorokite. (Turner et al., 1982). 84 O • Manganese O • Oxygen Tunnel cations or water molecules 85 concluded that their non-linear regressions describe the natural saturation of divalent cations in the lattice of todorokite. The decrease in the slope of the first order regression lines from the hydrogenous nodules to the diagenetic nodules recovered from Survey Region A can therefore be attributed to the saturation of the todorokite crystal lattice by manganese and associated divalent cations. The relationship between Zn and Mn/Fe does not show the same behaviour as the other elements associated with manganese. The reason for this is probably because of the low concentration of zinc in the nodules from this region compared to the other elements. Zinc, therefore, does not become saturated in the todorokite lattice structure. It has already been shown that the abundance of Ti is correlated with the presence of Fe. When Ti is plotted against Mn/Fe there is a sharp break in the slope of the first order regression line drawn through the hydrogenous nodules compared to one drawn through the diagenetic nodules, the slope for the hydrogenous nodules being greater than that for the diagenetic nodules. Since Ti is correlated with Fe, this change in the slope of the first order regression lines is the inverse of that displayed by those elements (except Co and Zn) that correlate with Mn. Just like the saturation of the todorokite crystal lattice with Mn and its associated divalent cations, the change in the slopes of the first order regression lines from the hydrogenous nodules to the diagenetic nodules can be interpreted as the saturation of the crystal lattice of the unidentified iron oxyhydroxide with Ti. These interelement associations and the coexistence of hydrogenous and diagenetic nodules within the same survey area have also been observed in samples collected from smaller survey areas located within Survey Region A. These include: DOMES Site A (Calvert & Piper, 1984), WAHINE (Calvert et al, 1978), Valdivia Sites V A 08-1 A l and A2 (Friedrich & Pliiger, 1974; Friedrich et al, 1977), Valdivia Site 13/1 (Glasby et al, 1982), and Valdivia Site 13/2 (Halbach & Ozkara, 1979). 86 1.4.1.2.3.3.1 Complex Correlations Between Cobalt with Manganese and Iron Cobalt shows a complex association with Mn and Fe, which is unlike that of the other minor elements (Figure 1-19). In hydrogenous nodules, Co is positively correlated with Mn, whereas in diagenetic nodules Co is positively correlated with Fe. The complex association of Co with the manganese and iron oxide phases have been previously observed by Cronan & Tooms (1969), Price & Calvert (1970) and by Halbach et al. (1983). Price & Calvert (1970) suggested that this observed complex behaviour of Co in nodules is due to Co^ + substituting for M n 4 + in nodules condaining 8Mn0 2 as well as F e 3 + in the iron oxyhydroxide phases. Cobalt (III) (d^ ) is stable when in the low spin state with octahedral coordination and has an ionic radius almost identical to that of F e 3 + or M n 4 + . Cobalt (III) will therefore preferentially substitute for both F e 3 + in the FeOOHxnH 20 phase (Burns, 1965) and M n 4 + in the 5Mn0 2 phase (Glasby & Thijessen, 1982a; Halbach et al., 1981a). As noted previously, C o 3 + will also substitute for M n 4 + in the "ceilings" of todorokite (Burns, 1976). Since hydrogenous nodules contain both 8Mn0 2 and todorokite, this would explain the positive association of Co with Mn. Diagenetic nodules, on the other hand, contain mostly todorokite. Although the substitution of C o 3 + for M n 4 + in the "ceilings" of todorokite probably occurs, the substitution of C o 3 + for F e 3 + in the FeOOHxnH 20 phase appears to be more dominant as seen by the correlation of Co with Fe in these nodules. 87 Figure 1-19. Complex association of Co with Mn and Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 88 0.60 0.00 2.00 4.00 6.00 8.00 Mn/Fe 89 1.4.1.2.3.3.2 Correlation of Copper with Nickel The Cu/Ni ratio shows a strong positive correlation with the Mn/Fe ratio (Figure 1-20). Hydrogenous nodules are found to have generally lower Cu/Ni ratios than diagenetic nodules. This relationship has also been observed by Raab (1972), Calvert & Price (1977a), and Calvert et al. (1978). As noted by Seigel (1981) and Calvert & Piper (1984), nodules with higher Cu/Ni ratios contain more crystalline todorokite rather than SMnG^. This trend is also seen for the nodules recovered from Survey Region A when comparing figure 1-20 with Figure 1-17. The reason for this correlation can be explained by examining the behaviour of Cu and Ni during diagenesis. Work on the trace metal geochemisty of pelagic sediment pore waters by Klinkhammer (1980), Callender & Bowser (1980), and by Klinkhammer et al. (1982) has shown that Cu and Ni behave quite differently during diagenesis in marine sediments. During diagenesis, Ni follows Mn, apparently being taken up by solid Mn phases close to the sediment surface and is released to the pore water along with Mn at depth. In contrast, Cu is released to the pore water very close to the sediment surface were it can diffuse both into the bottom water and into the sediment. These different behaviours are consistent with the Cu-enrichment in the most markedly diagenetic nodules at Survey Region A. 90 Figure 1-20. Correlation between Cu/Ni and Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 1.50 0.00 4- 1 1 1 1 0.00 2.00 4.00 6.00 8.00 Mn/Fe 92 1.4.2 S U R V E Y REGION B 1.4.2.1 Crusts 1.4.2.1.1 Mineralogy A typical XRD pattern of a crust from Survey Region B, shows that the mineralogy of crusts from this region is dominated by todorokite, birnessite, and minor amounts of 5Mn0 2 (Figure 1-21). The todorokite to 8 M n 0 2 ratios range from 0.00 to 2.82 with an mean of 0.45. Also shown in Figure 1-21 is the presence of calcite. Once again the XRD pattern shows the presence of a fine-grained, poorly crystalline material which has been previously identified as being cryptocrystalline or amorphous hydrated iron oxides (Glasby, 1972; Crerar & Barnes, 1974). A more detailed study on the iron oxide phase mineralogy of crusts and nodules will be discussed in Chapter 2 and Chapter 3. 1.4.2.1.2 Bulk Composition The major element data for crusts recovered from Survey Region B are listed in Appendix D. As for samples recovered from Survey Region A, this compositional data will be used to estimate the relative proportions of the iron and manganese oxides and other phases in the crusts, and help interpret inter-element assocations which will be discussed later. The mean composition of crusts from this region is listed in Table 1-8, together with the average compositions of crusts and nodules from four other studies from within the same area. From Table 1-8, the two average compositions of the crusts show a very wide range in Mn, Fe, Cu, Ni, and Co concentrations while the two 93 Figure 1-21. A typical XRD pattern of a crust from Survey Region B. RISE III 3 D-1 1 0 0 Table 1-8. Mean concentrations of major elements in crusts from Survey Region B. Concentrations are given in weight per cent. Mean Composition Average of two Representative of Crusts from Eastern P a c i f i c hydrothermal c r u s t Survey Region B crusts (Lonsdale from the E.P.R. et a l . , 1980) (Bonatti et al., 1972) Element Concen. Element Concen. Element Concen. S i 9.44 S i 5.80 T i 0.42 A l 2.51 A l <0.5 Fe 14.02 Fe 4.40 Fe 31.10 Mn 12.67 Mn 39.28 Mn 0.58 Mg 1.71 Ca 2.63 Na 1.84 K 0.65 P 0.27 Co 0.06 Co 0.10 Co 0.00 Ni 0.19 Ni 0.24 Ni 0.01 Cu 0.08 Cu 0.08 Cu 0.01 Zn 0.04 Zn 0.11 Ba 0.22 Mn/Fe 0.90 Mn/Fe 8.93 Mn/Fe 0.02 96 average compositions of the nodules are similar. The mean concentrations of Mn, Cu, Ni, and Co in crusts from this study are significantly lower than the concentration of these elements in the average compositions of the nodules reported by Cronan & Tooms (1969) and by Skornyakova (1979), while the mean concentration of Fe in crusts from this study is significantly higher than the consentration of this element reported in the nodules. The average composition of the crusts from this study is also significantly different from the average composition of the crusts reported by Lonsdale et al. (1980) and by Bonatti et al. (1972). The average concentrations of Mn, Fe, Cu, Ni, and Co in the crusts from this study fall between the two extreme concentrations of these elements found by Lonsdale et al. (1980) and by Bonatti et al. (1972). The same is true for the average Mn/Fe ratios. The mean Mn/Fe ratio for the crusts from this study is 0.90. This this significantly lower than the mean Mn/Fe ratios of the nodules and between the two extreme Mn/Fe ratios of the crusts. 1.4.2.1.3 Interelement Associations 1.4.2.1.3.1 Correlations with Aluminium Aluminium shows a strong positive correlation with Si and a weak correlation with Ti (Figure 1-22). An explanation for these correlations is not apparent when examining the XRD diffractogram shown in Figure 1-21, since this XRD pattern does not show the presence of alunimosilicates. Furthermore, when comparing the Si/Al and Ti/Al ratios of the crusts with those for the Average Pacific Pelagic Clay and for the Mid-Ocean-Ridge-Basalts (MORB) from the EPR, the Si/Al ratio for the crusts is considerably higher while the Ti/Al ratio for the crusts is relatively close to that of the Average Pacific Pelagic Clay (Table 1-9). Just like the crusts and nodules from Survey Region A, this suggests that several sources of Si contribute to the crusts Figure 1-22. The relationship between Al and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts. 25.00 20.00 + 15.00 + 10.00 + 5.00 + 0.00 0.00 8.00 2.00 1.50 + 0.00 0.00 2.00 4.00 6.00 8.00 A\ (%) 99 Table 1-9. Comparison of the composition of aluminosilicates in crusts to Average Pacific Pelagic Clay and Mid-Ocean Ridge Basalts. Element Ratios S i / A l T i / A l Crusts from 3.76 0.17 Survey Region B (This Study) Average P a c i f i c 2.92 0.06 Pelagic Clay (Bischoff et a l . , 1979) Average Mid-Ocean-Ridge Basalts from the E.P.R. (Melson et a l . , 1976) 2.99 0.13 100 from this region. In crusts located close to the EPR, the abundance of silicon is determined by two sources: (1) incorporation of detrital aluminosilicates which are composed of eolian debris and volcanogenic debris eroded from submarine outcrops by bottom currents (Hein et al., in press a); (2) an additional source of Si precipitated from hydrothermal sources (Toth, 1980). According to Toth (1980), iron- and silica-rich hydrothermal crusts are composed of iron-rich nontronite pr amorphous hydrated iron oxides and silica, with very low trace-metal contents. An X-ray diffractogram of a crust with high concentrations of Fe and Si and low concentrations of trace elements (Figure 1-23) shows that an amorphous material is the dominant phase present. Some sharp diffraction peaks also occur in the diffractogram, but they are few in number and of such low intensity that it is impossible to identify which mineral(s) these peaks belong to. 1.4.2.1.3.2 Correlations with Calcium Calcium shows positive correlations with Si and Mg (Figure 1-24). The presence of Ca in crusts from this region can partly be attributed to the presence of calcite, as shown in Figure 1-21. However, the correlation of Ca with Si and Mg can not be so easily explained. In samples containing high concentrations of Ca, Si, and Mg, X R D analysis shows that the dominant mineral phase is the clinopyroxene manganoan diopside (Figure 1-25). The presence of this mineral would explain the correlation of Ca to Si and Mg since it has the chemical formula (Ca,Mn)(Mg,Fe,Mn)Si206. 101 Figure 1-23. An XRD pattern of a crust with high concentrations of Fe and Si and low concentrations of trace elements. SOTW 9 32 D-1 100 103 Figure 1-24. The relationship between Ca and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts. 104 GO 25.00 20.00 + 15.00 + 10.00 5.00 + 0.00 0.00 8.00 6.00 4.00 + 2.00 + 0.00 • °/ A o o P o # o 1 0.00 2.00 4.00 6.00 8.00 Ca {%) 105 Figure 1-25. A typical XRD pattern of a crust with high concentrations of Ca, Si, and Mg. 106 INTENSITY (COUNTS/SECOND) o 03 107 1.4.2.1.3.3 Correlations with Manganese Although the crusts from Survey Region B have an average Mn/Fe ratio of 0.90 (Table 1-8), the range is extremely wide (0.06 to 222.68). Consequently, there is a high degree of fractionation of these two major elements in the crusts from this region. The relationships between Mn and the minor elements indicate that there are three distinct groups of crusts that can be distinguished within Survey Region B. The largest group of crusts has Mn concentrations ranging from 7 to 20 weight per cent, Mn/Fe ratios ranging from 0.41 to 1.56, and show strong positive linear correlations between Mn and Co, Cu, and Ni (Figure 1-26). Like the crusts from Survey Region A, this group of crusts is of hydrogenetic origin, since the Mn/Fe ratios are less than 2.5. The two remaining groups of crusts are characterized by their distinctively different concentrations of Mn. One group is highly enriched in Mn ( > 30 weight per cent) and has Mn/Fe ratios ranging from 7.04 to 222.68. XRD analysis shows that birnessite together with a minor amount of todorokite, is present (Figure 1-27). As noted by Toth (1980), hydrothermal crusts consist of nearly pure, well-crystallized birnessite, identified by its intense peaks at 7.0-7.2A, and 3.5-3.6A, and todorokite with its most intense peaks at 9.65A, 4.82A (Burns & Burns, 1977). The second group is depleted in Mn ( < 3 weight per cent), and has Mn/Fe ratios ranging from 0.06 to 0.21. Both groups of crusts are depleted Co, Cu, and Ni compared to the hydrogenetic crusts. These two groups of crusts show the same fractionation of Mn and Fe and low concentrations of trace elements as the two groups of hydrothermal crusts identified by Toth (1980) 108 Figure 1-26. The relationship between Mn and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts. 0 . 3 0 o 0 . 2 0 + 0.10 + • A 0 . 0 0 -0 . 0 0 - e — © -1 5 . 0 0 O 3 0 . 0 0 4 5 . 0 0 Mn (%) 0 . 5 0 0 . 4 0 + 0 . 3 0 + 0 . 2 0 + 0.10 + 0 . 0 0 0 . 0 0 1 5 . 0 0 3 0 . 0 0 4 5 . 0 0 Mn (%) 110 o o 0.30 0.20 + 0.10 + 0.00 0.00 15.00 30.00 45.00 Mn (%) Figure 1-27. An XRD pattern of a crust which is enriched in Mn ( > 30 weight per cent). H 113 1.4.2.1.3.4 Correlations with Iron The concentrations of the elements that correlate positively with Fe (Ba, Co, P, and Zn) do not show the same marked difference between the three groups of crusts from this region (Figure 1-28). The high degree of correlation between P and Fe has not been observed previously in oceanic ferromanganese crusts. A correlation between Fe and P was first noted in oceanic ferromanganese nodules by Calvert & Price (1977a). A marked enrichment of P in the Fe phase of many shallow marine and lacustrine nodules has also been described by Sevast'yanov & Volkov (1966), Winterhalter (1966), Winterhalter & Siivola (1967), and Calvert & Price (1970; 1977b). This association has been attributed to the adsorption of P by hydrous ferric oxides (Winterhalter & Siivola, 1967) or to the formation of a ferric phosphate phase (Sevast'yanov & Volkov, 1966). The enrichment of P in the iron-rich sediments accumulating on the EPR has been explained in a similar way by Berner (1973). Since the P concentrations at equivalent Fe concentrations in hydrothermal crusts are consistent with those from the hydrogenous crusts, it is possible that either the adsorption of P by hydrous ferric oxides or the formation of a ferric phosphate phase can explain this observed association. 1.4.2.1.4 Correlation Between Cobalt Abundance and Distance from the EPR The concentration of Co in the hydrogenetic crusts from this region is significantly lower than that in the hydrogenetic crusts from Survey Region A. This trend in the depletion of Co in crusts with increasing proximity to the EPR is in agreement with the results of Manheim & Lane-Bostwick (1988). They concluded Figure 1-28. The relationship between Fe and other major elements. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts. 0.80 0.60 + 0.40 + 0.20 0.00 O O O & OQ + 0.00 5.00 10.00 15.00 Fe (%) 20.00 25.00 0.30 0.20 0.10 + 0.00 0.00 5.00 10.00 15.00 - 20.00 25 Fe (%) 1.00 0 . 8 0 - -0 . 6 0 - -0 . 4 0 0 . 2 0 - -0 . 0 0 £ 0 . 0 0 5 .00 10 .00 15 .00 Fe (%) 2 0 . 0 0 2 5 . 0 0 0 . 0 7 - p 0 . 0 6 - -0 . 0 5 - -0 . 0 4 - -0 . 0 3 -0 . 0 2 - -0.01 0 . 0 0 ' 0 . 0 0 O O o o O O O OGEXODOO C O GOD OGSD O o o < n o O A O O A) 5 .00 . 10 .00 15 .00 Fe (%) 2 0 . 0 0 2 5 . 0 0 117 that the depletion of Co in crusts is a reflection of the location and intensity of submarine hydrothermal discharge. Hydrothermal vent waters are greatly enriched in Fe and Mn with respect to normal waters, but Co:Mn and Co:Mn+Fe ratios for both vent fluids and marine hydrothermal oxides are two orders of magnitude lower than in normal ocean waters. Cobalt in crusts, therefore, is concentrated in inverse proportion to the regional influence of discharging hydrothermal fluids. The largest depletion of Co will be found in crusts recovered from the EPR. Higher Co concentrations are found in crusts farther removed from the hydrothermal discharge of the EPR with the highest Co concentrations found in the central parts of the Pacific Ocean. Although the concentrations of Cu, Ni, and Zn are also depleted in hydrothermal crusts compared to hydrogenetic crusts recovered from Survey Region B, these elements do not show the same increase in concentration in crusts which are far removed from the hydrothermal influence of the EPR. It appears that no other major element shows such a trend in concentration with proximity to the EPR in this study. 1.4.2.2 Nodules 1.4.2.2.1 Mineralogy A typical XRD pattern of a nodule from Survey Region B, shows that the mineralogy of nodules from this region is dominated by todorokite, with minor amounts of birnessite and 5Mn02 (Figure 1-29). The todorokite/5Mn02 ratios range from 0.00 to 2.68 with an mean of 1.12. Also shown in Figure 1-29 is the presence of quartz and feldspar. Once again, the XRD pattern shows the presence of a fine-grained, poorly crystalline material which has been previously identified as 118 Figure 1-29. A typical XRD pattern of a nodule from Survey Region B. 120 being cryptocrystalline or amorphous hydrated iron oxides (Glasby, 1972; Crerar & Barnes, 1974). A more detailed study on the iron oxide phase mineralogy of crusts and nodules will be discussed in Chapter 2 and Chapter 3. 1.4.2.2.2 Bulk Composition The major element data for nodules recovered from Survey Region B are listed in Appendix D. As for samples recovered from Survey Region A, this compositional data will be used to estimate the relative proportions of the iron and manganese oxides and other phases in the crusts, and help interpret inter-element assocations which will be discussed later. The mean composition of nodules from this region is listed in Table 1-10, together with the average compositions of crusts and nodules from four other studies from within the same area. From Table 1-10, the compositions of the crusts show a very wide range in Mn, Fe, Cu, Ni, and Co concentrations, while the two average compositions of the nodules are similar. The mean concentrations of Cu, Ni, and Co in nodules from this study are significantly lower than the averages of the nodules reported by Cronan & Tooms (1969) and Skornyakova (1979), but are consistently higher than the average compostion of the crusts reported by Lonsdale et al. (1980) and Bonatti et al. (1972). The mean concentration of Mn and Fe in nodules from this study is similar to those reported by Cronan & Tooms (1969) and Skornyakova (1979), but falls between the two extreme concentrations in the crusts. The average Mn/Fe ratio for the nodules from this study is 2.74 which is similar to the Mn/Fe ratio of the average composition of the nodules studied by Cronan & Tooms (1969) and by Skornyakova (1979) but falls between the two extreme Mn/Fe ratios of the crusts. Table 1-10. Mean concentrations of major elements in nodules from Survey Region B. Concentrations are given in weight per cent. Mean Composition Average composition Average composition of nodules from of nodules from the of nodules from the Survey region B. N.E. P a c i f i c Ocean equatorial P a c i f i c (Cronan & Tooms, (Skornyakova, 1979) 1969) Element Concen. Element Concen. Element Concen. S i 7.55 T i 0.30 T i 0.43 T i 0.60 A l 2.23 Fe 7.97 Fe 9.44 Fe 7.98 Mn 21.81 Mn 22.33 Mn 23.10 Mg 1.74 Ca 1.79 Na 1.61 K 0.91 P 0.31 Co 0.12 Co 0.19 Co 0.18 Ni 0.71 Ni 1.08 Ni 1.10 Cu 0.46 Cu 0.63 Cu 0.89 Zn 0.09 Zn 0.11 Zn 0.11 Ba 0.24 Ba 0.38 Mn/Fe 2.74 Mn/Fe 2.37 Mn/Fe 2.89 122 1.4.2.2.3 Interelement Associations 1.4.2.2.3.1 Correlations with Aluminium The nature of the aluminosilicates in the nodules is shown by the relationship between Al and other major elements. For the nodules, aluminium shows a strong positive correlation with Si, Ti, and K (Figure 1-30). From the X-ray diffractogram (Figure 1-29), these correlations with Al could be explained by the presence of quartz and feldspar. By using the Si/Al, Ti/Al, and K/Al element ratios, the origin of the aluminosilicate fraction of the nodules can be identified. As shown in Table 1-11, the Si/Al, Ti/Al, and K/Al ratios are 3.39, 0.13, and 0.09 respectively. The Si/Al ratio for the nodules is considerably higher than those for the Average Pacific Pelagic Clay and for the MORB from the EPR, while the Ti/Al and the K/Al ratios for the nodules are relatively close to that of the MORB. Although the Ti/Al and K/Al ratios may indicate that the aluminosilicate fraction of the nodules originates from MORB from the EPR, the Si/Al ratio suggests that several sources of Si contribute to the nodules from this region. In nodules located close to the EPR, the abundance of silicon is determined by two sources: (1) incorporation of detrital aluminosilicates which are composed of eolian debris and volcanogenic debris eroded from submarine outcrops by bottom currents (Hein et al., in press a); (2) an additional source of Si precipitated from hydrothermal sources (Toth, 1980). According to Toth (1980), iron- and silica rich hydrothermal crusts are composed of iron-rich nontronite or amorphous hydrated iron oxides and silica, with very low trace-metal contents. 123 Figure 1-30. The relationship between Al and other major elements. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules. 125 0.50 • • c9 o • o o ° o A o o o 1 I 0.00 2.00 4.00 6.00 Al (X) Table 1-11. Comparison of the composition of aluminosilicates in nodules to Average Pacific Pelagic Clay and Mid-Ocean Ridge Basalts. Nodules from Survey Region B (This Study) Average P a c i f i c Pelagic Clay (Bischoff et al., 1979) Average Mid-Ocean-Ridge Basalts from the E.P.R. (Melson et al., 1976) Element Ratios S i / A l T i / A l K/Al 3.39 0.13 0.09 2.92 0.06 0.25 2.99 0.13 0.02 1.4.2.2.3.2 Phosphorite Although the concentrations of Ca and P in the nodules from this region are considerably lower than those in the nodules from Survey Region A, they do show a positive correlation (Figure 1-31). An X R D tracing of a nodule with high Ca and P concentrations shows that this correlation is due to the presence of carbonate fluorapatite {(Ca,Mg,Na,K)1 0[(P,C)O4]6(F,OH)2} (Figure 1-32). The presence of carbonate fluorapatite has already been used to explain the correlation of P with Ca in crusts from this same region. The presence of carbonate fluorapatite in nodules is possibly due to the erosion of carbonate fluorapatite from the neighbouring seamounts and its incorporation into the nodules as a nuclei. 1.4.2.2.3.3 Correlations with Manganese Although the nodules from Survey Region B have an average Mn/Fe ratio of 2.74 (Table 1-10), the range is extremely wide (0.63 to 23.93). Consequently, there is a high degree of fractionation of these two major elements in the nodules from this region. Although the range of Mn/Fe ratios for the nodules is not as extreme as for the crusts (0.06 < Mn/Fe > 222.68), element correlations will be considered with respect to Mn concentrations to provide a comparison with the crusts from this same region. The relationships between Mn and the minor elements indicate that three distinct groups of nodules can be distinguished within Survey Region B. The largest group of nodules has Mn concentrations ranging from 10 to 30 weight per cent, Mn/Fe ratios between 0.75 and 7.70, and show strong positive linear correlations between Mn and Co, Cu, Ni, Zn, Mg, and Ba (Figure 1-33). Unlike nodules from Survey Region A, this group of nodules does not show a distinct division between 128 Figure 1-31. The correlation between Ca and P. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules. 129 Ca (%) Figure 1-32. An XRD pattern of a nodule with high Ca and P concentraions. Mn26 DEGREES 2© H 132 Figure 1-33. The relationship between Mn and other major elements. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules. 0 . 6 0 0 . 4 0 + 0 . 2 0 0 . 0 0 O 4 * 0 . 0 0 '8 SL 10 .00 2 0 . 0 0 Mn (%) 3 0 . 0 0 4 0 . 0 0 1.25 1.00 + 0 . 7 5 + 4 0 . 0 0 0 . 2 5 0 . 2 0 + 0 . 1 5 + 0 . 1 0 + 0 . 0 5 + 0 . 0 0 o • o °8 C O < o J. i • 1 i . 0 . 0 0 10 .00 2 0 . 0 0 3 0 . 0 0 4 0 . 0 0 Mn {%) 0.00 10.00 20.00 30.00 40.00 Mn (58) 1.50 1.00 + 0.50 + 0.00 0.00 10.00 20.00 30.00 40.00 Mn (%) 136 hydrogenous nodules (Mn/Fe < 2.5) and diagenetic nodules (Mn/Fe > 2.5). Although the range of Mn/Fe ratios shows that these two types of nodules are present, the two groups do not show the same variation in interelement correlations as seen in Survey Region A. For identification purposes, this large group of nodules will be called hydrogenous nodules. The two remaining groups of nodules are characterized by their distinctively different concentrations of Mn. One group is highly enriched in Mn ( > 30 weight per cent), has Mn/Fe ratios ranging from 4.96 to 23.93 and low concentrations of Cu, Ni, and Co compared with the hydrogenous group. X R D analysis shows that todorokite, together with minor birnessite, is present (Figure 1-34). As noted by Toth (1980), hydrothermal crusts consist of nearly pure, well-crystallized birnessite, identified by its intense peaks at 7.0-7.2A, and 3.5-3.6A, and todorokite, with its most intense peaks at 9.65A, 4.82A (Burns & Burns, 1977). The second group of nodules is depleted in Mn ( < 10 weight per cent), and has Mn/Fe ratios ranging from 0.06 to 0.96. This group also has low concentrations of Cu, Ni, Co and Zn, as would be explained for the low Mn and todorokite contents. 1.4.2.2.3.4 Correlations with Iron The concentrations of the elements that correlate positively with Fe, (P, Ti and Si), do not show the same marked difference between the three groups of nodules from this region (Figure 1-35). A correlation between Fe and P was also noted in oceanic ferromanganese nodules by Calvert & Price (1977a). A marked enrichment of P in the Fe phase of many shallow marine and lacustrine nodules has also been described by Sevast'yanov & Volkov (1966), Winterhalter (1966), Winterhalter & Siivola (1967), and Calvert & Price (1970; 1977b). This association has been attributed to the adsorption of P by hydrous ferric oxides (Winterhalter & 137 Figure 1-34. An XRD pattern of a nodule which is enriched in Mn ( > 30 weight per cent). CERS 21 D-3 100 139 Figure 1-35. The relationship between Fe and other major elements. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules. 140 1.50 Fe {%) 141 3 0 . 0 0 2 0 . 0 0 + 1 0 . 0 0 + 0 . 0 0 0 .00 5 .00 10 .00 15 .00 2 0 . 0 0 Fe (SK) 142 Siivola, 1967) or to the formation of a ferric phosphate phase (Sevast'yanov & Volkov, 1966). The enrichment of P in the iron rich sediments accumulating on the EPR has been explained in a similar way by Berner (1973). Except for three of the Fe-rich hydrothermal nodules, the P concentrations at equivalent Fe concentrations in hydrothermal crusts are similar to those from the hydrogenous crusts, it is possible that either the adsorption of P by hydrous ferric oxides or the formation of a ferric phosphate phase can explain this observed association. For nodules located close to the EPR, the abundance of silicon is determined by two sources: (1) incorporation of detrital aluminosilicates which are composed of eolian debris and volcanogenic debris eroded from submarine outcrops by bottom currents (Hein et al., in press a); (2) an additional source of Si precipitated from hydrothermal sources (Toth, 1980). According to Toth (1980), iron- and silica rich hydrothermal crusts are composed of iron-rich nontronite or amorphous hydrated iron oxides and silica, with very low trace-metal contents. An X-ray diffractogram of a nodule with high concentrations of Fe and Si and low concentrations of trace elements (Figure 1-36) shows that nontronite and quartz are the dominant iron- and silica rich phases present. The correlation between Fe and Ti has also been noted in the crusts studied by Manheim & Lane-Bostwick (1989) and in nodules studied by Goldberg (1954), Burns & Fuerstenau (1966), Cronan (1967), and by Arrhenius et al. (1979). Manheim & Lane-Bostwick (1989) reported that the behavior of the Fe-Ti relationship is still poorly understood and much of the scatter is probably due to admixture in the detrital component. 143 Figure 1-36. An XRD pattern of a nodule with high concentrations of Fe and Si and low concentrations of trace elements. DEGREES 20 145 1.4.2.2.3.5 Identification of the Two Groups of Hydrothermal Nodules Because of the different geochemical behavior of Fe and Mn, fractionation of the two elements is common in hydrothermal solutions (Lyle, 1981). This results in the formation of two distinct end member deposits: (1) Well-crystallized birnessite and todorokite crusts with generally very low trace metal content, and (2) Iron- and silica-rich crusts composed of iron-rich nontronite or amorphous hydrated iron oxides and silica, also with very low trace metal contents. The fractionation of Fe and Mn occurs as a result of the lower solubility of iron species as both Fe and Mn undergo oxidation (Krauskopf, 1957) by mixing of the reduced hydrothermal fluid with oxygenated bottom water. The association of Si with Fe may result from coprecipitation or adsorption of dissolved SiC>2 onto hydrated iron-oxide colloids. The low content of minor elements in these deposits results from: (1) the low concentrations of these elements relative to Fe and Mn in hydrothermal solutions, and (2) the rapid depostion of the deposits which minimizes adsorption of elements from seawater (Toth, 1980). These two groups of crusts with distinct end-member compositions and mineralogy were identified in the crusts from Survey Region B. One group of hydrothermal crusts was found to be enriched in Mn and depleted in Fe and Si. The Mn-rich mineral phase was identified to be todorokite and birnessite. The second group of hydrothermal crusts was found to be enriched in Fe and Si and depleted in Mn. The Fe-Si rich mineral phase was identified as amorphous hydrated iron oxides and silica. Both groups of hydrothermal crusts were depleted in Co, Cu, and Ni. Unlike crusts, nodules do not form by the direct precipitation of hydrothermal fluids, however, two groups of nodules, from Survey Region B, showed identical trends in composition and mineralogy as the two groups of hydrothermal crusts. One 146 group of hydrothermal nodules were found to be enriched in Mn and depleted in Fe and Si. The Mn-rich mineral phase was identified to be todorokite and birnessite. The second group of hydrothermal nodules was found to be enriched in Fe and Si and depleted in Mn. The Fe-Si rich mineral phase was identified as iron-rich nontronite. Both groups of hydrothermal nodules were depleted in Co, Cu, and Ni. The two groups of hydrothermal nodules with this distinct end-member compositions and mineralogy have also been identified by Dymond et al. (1984) and by Chen & Owen (1989) in nodules from the eastern equatorial Pacific. In their study of nodules from the north equatorial Pacific, Dymond et al. (1984) proposed that the chemical composition of nodules from the three nodule-bearing MANOP sites in the Pacific can be accounted for in a qualitative way by variable contributions of distinct accretionary processes. They proposed that these accretionary modes are: (1) hydrogenous, the direct precipitation or accumulation of colloidal metal oxides in seawater; (2) oxic diagenesis, the variety of ferromanganese accretion processes occuring in oxic sediments; and (3) suboxic diagenesis, the redultion of M n ^ + by oxidation of organic matter in the sediments. They concluded that processes (1) and (2) occur at all three MANOP nodule bearing sites and process (3) occurs only at site H. Chen & Owen (1989) used these results to interpret the factor analyses of geochemical data from nodules representing a broad area of the southeast Pacific Ocean. They concluded that nodule compositions are controlled by four factors: (1) suboxic diagenesis; (2) oxic diagenesis; (3) hydrogenous precipitation; and (4) hydrothermal precipation. Three of these four factors are identical to those identified by Dymond et al. (1984) (Chen & Owen, 1989). In the study by Chen & Owen (1989), they identified the hydrothermal nodules as being enriched in Fe but depleted in Mn, Co, Cu, and Ni. This composition agrees with the Fe-Si rich hydrothermal crusts and nodules identified in Survey Region B and the Fe-Si rich hydrothermal crusts studied by Toth (1980). 147 Both Dymond et al. (1984) and Chen & Owen (1989), however, misinterpreted the Mn-rich end-member composition of hydrothermal nodules. Dymond et al. (1984) stated that suboxic diagenesis results in accretion of material which is Mn-rich but depleted in other transition metals. They further stated that suboxic diagenesis results in an unstable todorokite which transforms to a 7A phase (birnessite) upon dehydration. From their limited growth rate data for nodules from MANOP site H, they also concluded that suboxic accretion is the fastest of the three processes with rates at least 200mm/10^yr. The compositions of the suboxic diagenetic nodules described by Dymond et al. (1984) and by Chen & Owen (1989) are identical to both the Mn-rich hydrothermal crusts and nodules from Survey Region B and the Mn-rich crusts studied by Toth (1980). Although no growth rates have been determined for nodules that have been identified as being hydrothermal, rapid growth rates of greater than lOOmm/Myr for hydrothermal crusts located near the EPR have been proposed by Manheim & Lane-Bostwick (1988), Toth (1980), and Moore & Vogt (1976). 1.4.2.2.4 Variations with Depth 1.4.2.2.4.1 Behaviour of Manganese and Iron Unlike the nodules from Survey Region A, the composition of nodules from Survey Region B, appears to be related to water depth. Of those elements that show an association with Mn, Co, Cu, Ni, and Ba increase in concentration with increasing depth (Figure 1-37). To understand the correlation between nodule composition and water depth, the source of constituent elements must be identified. Halbach & Puteanus (1984b) have proposed that for hydrogenetic crusts from the central Pacific Ocean which 148 Figure 1-37. The correlation between Mn and those elements that are associated with Mn and water depth. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules. Co (%) 0.00 0 0.20 0.40 0.60 1 1 1 -- OMZ e # O Q> gg> eft o CCD T X T O O 6^ 0.00 0 Cu (%) 0.25 0.50 0.75 1.00 1.25 1 --2 3 4 5 6 OMZ P O O # O o c^o o CCD O e—o- T T O " o o o 0 Depth (km) Depth (km) 151 show a change in composition with depth, the main sources of Mn and its associated trace metals is colloidal Mn-hydroxide particles that are released in the water column from the dissolution of carbonate plankton skeletons and a further source of Mn and its associated trace metals supplied via the OMZ. Within the OMZ there is a high concentration of dissolved Mn as a result of the in situ decomposition of organic matter along with the insitu reduction of Mn-bearing solid phases (Klinkhammer & Bender, 1980; Landing & Bruland, 1980). This zone of maximum concentration of M n 2 + produces a flux of M n 2 + by diffusion and turbulent mixing into shallower and deeper waters which have an increased oxygen content. This causes oxidation of the M n 2 + and results in the formation of hydrated M n 0 2 particles which are incorporated into the hydrogenetic crusts (Halbach et al., 1988). The extent of the O M Z in the eastern equatorial Pacific and the depletion of oxygen within this zone, are shown in Figure 1-38. Geosecs Station 343 is located within Survey Region B at 16°31.1'N and 122°59.3'W. Based on this profile at this site, the OMZ within Survey Region B lies at water depths of between 171 and 1675m; the minimum dissolved oxygen concentration is O^mole/kg. The metal concentrations in the nodules continue to increase below the CCD which is found between the water depths 4400 and 4800m (Berger et al., 1976; Heath et al., 1977; Piper et al., 1979). The abyssal seafloor between the CCFZ lies below a zone of high biological productivity and is characterized by the presence of siliceous ooze with low sedimentation rates due to the erosional influence of the bottom waters. Biological production at the sea surface is considered to be the principal means of concentration of trace metals in the marine environment (Friedrich et al., 1983). Trace metals are incorporated in the soft parts or tests of plankton, or perhaps are adsorbed to test surfaces (Lyle, 1978). After the organism dies, these metals are then transported to the seafloor where in situ dissolution is the principal mechanism making these metals available to the formation of manganese nodules 152 Figure 1-38. The profile of the 0 2 concentration in seawater at Geosecs Station 343. O 2 ( / ^ m o l e / k g ) 0 100 200 300 O X Y G E N MINIMUM Z O N E 154 (Andrews et al, 1983; Glasby & Thijessen, 1982b). As proposed by Staffers et al (1981), the enhanced supply of Ni, Cu, and Ba to the nodules in the equatorial high productivity zone is due to the dissolution of tests within the sediment column. Unlike Stoffers et al (1981), significant correlations were found between the composition of nodules from Survey Region B and depth. When describing the regional setting of the abyssal seafloor between the CCFZ, it was stated that the CCD within the CCFZ ranges in depth from 4800m in the south to 4400m in the north (Berger et al, 1976; Heath et al, 1977; Piper et al, 1979). The increase in concentrations of the elements Cu, Ni, and Ba with increasing depth can possibly be attributed to the biological productivity at the sea surface and the in situ dissolution at depth due to the CCD where diagenetic processes make these elements available for the formation of nodules. The increase in the concentrations of Co, Cu, Ni, and Ba in nodules with increasing depth below the CCD is possibly caused by the continued supply of these elements due to the dissolution of siliceous tests during early diagenesis (Halbach et al, 1981b; Stoffers et al, 1981). L4.2.2.4.2 Behaviour of Cobalt The positive linear correlation between Co and depth in nodules from Survey Region B, can also be explained by examining the regional bathymetry of the abyssal seafloor between the CCFZ. Subsidence of the cooling oceanic crust, formed at the EPR, has led to generally increasing regional water depths from the EPR to the west. The depth of the seafloor in Survey Region B is therefore an indicator of its distance from the EPR. As proposed by Manheim & Lane-Bostwick (1988), the depletion of Co in Pacific crusts indicates the location and intensity of submarine hydrothermal discharge. They found that Co-enriched crusts are found where water masses are 155 most isolated from hydrothermal activity. In contrast, cobalt-depleted crusts coincide with known areas of hydrothermal activity. This same association between the depletion of Co and the location and intensity of hydrothermal discharge seems to apply to the nodules recovered from Survey Region B. Those nodules that are located close to the EPR occur in water depths of about 3000m (Figure 1-3). These nodules are found to have Co below 0.05 weight per cent (Figure 1-37). Those nodules located farthest away from the EPR occur in deeper water (Figure 1-3) and are enriched in Co ( > 0.20 weight percent) (Figure 1-37). This is the first time that the depletion of Co due to the hydrothermal influence of the EPR has been noted in oceanic ferromanganese nodules from the Eastern Equatorial Pacific. 156 1.5 REFERENCES Abbey, S., 1983. Studies in "standard samples" of silicate rocks and minerals 1969-1982. Geol. Surv. 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Prentice-Hall, Inc., Englewood Cliffs, N.J., U.S.A., pp. 34,103-105. 1.6 APPENDIX A THE LOCATION OF CRUST AND NODULE SAMPLES FROM SURVEY REGION A FERROMRNGRNESE CRUSTS LRB NUMBER CRUISE NUMBER LATITUDE LONGITUDE DEPTH DEGREES MINUTES DEGREES MINUTES <m> DODO 6 19 6.0 N 158 14.0 W 3400 DODO 7 18 43.0 N 158 17.0 U 750 DODO 8 18 21.0 N 158 27.0 W 1317 DODO 9-1 18 18.0 N 161 46.0 W 3720 DODO 9-2 18 18.0 N 161 46.0 W 3350 DODO 13 18 47.0 N 162 3.0 W 3148 DODO 14 19 22.0 N 162 19.0 W 4868 MIDPRC 25-F1 19 7.0 N 169 44.0 W 1740 MIDPRC 25-F2 19 7.0 N 169 44.0 W 1740 STYX 2 19 35.0 N 168 52.5 W 1805 7T0W 123 5 52.3 N 160 50.9 U 1604 7T0W 129 9 19.0 N 163 16.9 U 1563 7T0W 130 8 20.0 N 164 21.7 N 1519 7T0H 133 12 4.2 N 165 50.3 W 14B8 7T0W 137 14 27.5 N 168 58.7 W 1750 7T0W 142 18 8.1 N 169 4.0 W 2139 7T0W 143 19 30.7 N 168 52.5 W 1805 7T0W 144 21 32.1 N 167 55.8 W 1690 FERROMRNGRNESE NODULES LRB NUMBER CRUISE NUMBER LATITUDE LONGITUDE DEPTH DEGREES MINUTES DEGREES MINUTES <m> 82-MN-D-24 DODO 27P 9 0.0 N 169 0.0 W 5170 82-MN-D-25 DODO 27PG 9 0.0 N 169 0.0 W 5170 82-MN-D-26 DODO 31PG 9 11.0 N 168 48.0 W 5220 DODO 11 18 47.0 N 162 3.0 W 4630 DODO 12 18 38.0 N 162 8.0 W 5040 DODO 15 19 21.0 N 162 10.0 W 5032 DODO 15-3 19 21.0 N 162 10.0 W 5032 82-MN-S-41 STYX I 10FF 9 54.0 N 149 57.0 W 5304 B2-MN-S-76 STYX 9FFGB 12 2.0 N 145 46.0 W 5330 82-MN-W-BO WRHINE 13FF-4 8 22.6 N 152 59.0 W 5127 82-MN-W-81 WRHINE 18FF-3 8 16.3 N 152 58.0 W 5133 82-MN-W-82 WflHINE 18FF-6 8 16.3 N 152 58.0 W 5023 82-MN-W-83 WRHINE 2P 11 51.0 N 152 57.0 W 5221 B2-MN-W-86 WHHINE 2PG 11 51.0 N 152 57.0 W 5221 82-MN-W-87 WRHINE 4P 8 57.0 N 152 52.0 W 4839 82-MN-W-88 WRHINE 4PG 8 57.0 N 152 52.0 W 4839 82-MN-W-89 WRHINE 7PG 3 58.0 N 153 2.0 W 4992 B3-MN-J-118 JYN V 14G 9 20.0 N 150 35.0 W 4813 83-MN-J-119 JYN V 15PG 8 2.0 N 149 54.0 W 5073 B3-MN-J-120 JYN V 17PG 6 5.0 N 148 52.0 W 5036 B3-MN-J-121 JYN V 29G 13 32.0 N 146 1.8 W 5285 83-MN-J-122 JYN y 31PG 11 55.0 N 144 54.0 W 5539 MN 32 SUMMR 44DB 19 58.7 N 166 5.0 W 4941 MN 33 SUMMR 51DB 6 51.4 N 166 51.5 W 4762 MN 34 SUMMR 52DB 6 49.6 N 167 1.2 W 4682 MN 35 SUMMR 53DB 6 47.0 N 166 53.0 w 4674 MN 36 SUMMR 57DB 7 48.0 N 159 19.0 w 5128 MN 37 SUMMR 59DB 8 5.7 N 153 54.9 w 5003 MN 38 SUMMR 60DB 8 5.9 N 152 36.2 w 5036 MN 39 SUMMR 63DB 8 16.4 N 150 59.6 w 4833 MN 40 SUMMR 65DB 8 44.4 N 147 31.9 w 5126 MN 41 SUMMfl 66DB 8 43.6 N 147 35.4 W 5062 MN 42 SUMMR 68DB 8 34.5 N 147 46.7 W 5128 MN 43 SUMMR 69DB 8 57.9 N 146 40.1 W 5104 MN 44 SUMMfl 70DB 8 57.3 N 145 48.4 W 5033 MN 45 SUMMR 72DB 8 58.8 N 145 6.6 W 4943 MN 46 SUMMR 74DB 9 39.4 N 146 19.9 W 5036 MN 47 SUMMR 79DB 11 7.9 N 148 4.3 U 512B MN 48 SUMMR 80DB 10 58.7 N 148 19.5 W 5124 MN 49 SUMMR 83DB 11 1.1 N 148 29.9 W 5344 MN 50 SUMMR 84DB 11 56.0 N 146 26.9 W 5314 MN 51 SUMMfl 85DB 11 48.2 N 148 39.7 W 5503 MN 52 SUMMR 86DB 12 1.4 N 149 18.0 W 5311 MN 53 SUMMfl 87DB 11 58.2 N 150 IB.5 w 5003 MN 54 SUMMR B8DB 11 58.2 N 150 IB.5 1*1 5003 MN 55 SUMMR 89DB 11 29.2 N 149 11.0 W 5303 MN 56 SUMMfl 90DB 11 30.8 N 148 34.7 W 512B MN 86 SUMMfl 158DB 7 49.8 N 154 49.3 14 4908 MN 89 RPB0C75 47-12 9 3.5 N 151 11.1 W 5005 MN 90 RP80C75 47-13 9 2.3 N 151 11.2 W 5039 MN 91 RP80C75 50-29 8 43.8 N 150 18.7 W 5033 MN 92 RP80C75 50-30 8 41.1 N 150 15.1 W 4928 PLDS 8D-1 11 1.0 N 140 8.5 W . 4500 1.7 APPENDIX B THE LOCATION OF CRUST AND NODULE SAMPLES FROM SURVEY REGION B FERROMRNGRNESE CRUSTS LRB NUMBER CRUISE 83-MN-B-106 BNFC CflRR II CERES CERES CERES DPSOND DPSOND DPSOND HENDSMT QBR QBR QBR QBR QBR RISE II RISE II RISE II RISE II RISE II SIQR SOTW IX TRIPOD TRIPOD TRIPOD NUMBER LATITUDE DEGREES MINUTES 25P 10 22.5 N 6 9 57.0 N 1 13 26.4 N 5 12 44.2 N 6 12 44.3 N 3 9 8.4 N 4 9 7.8 N 5 9 12.7 N D-1-3 25 15.0 N 1 12 47.0 N 2 12 47.0 N 7<R> 10 22.0 N 7<B> 10 22.0 N 22 9 55.2 N 3 8 49.5 N 6 11 30.0 N 7 11 31.0 N B 11 30.0 N 13 12 32.0 N 4 8 9.4 N 32 14 5.3 N 2 20 45.0 N 3 21 18.0 N 9 21 5.0 N LONGITUDE DEGREES MINUTES DEPTH <m> 10B 38.4 W 2693 108 48.0 U 1228 102 36.3 W 3424 102 34.3 U 2700 102 33.6 U 1950 105 10.9 W 3240 105 0.6 1*1 2957 105 12.2 W 3124 119 40.0 w 64 110 25.0 u 2550 110 25.0 w 2550 108 23.0 w 3000 108 23.0 w 3000 104 29.0 w 1680 103 55.0 u 2095 103 17.5 w 2703 103 13.0 w 2183 103 13.5 w 2450 103 17.0 w 2251 104 27.4 u 3325 110 48.9 W 3400 112 47.0 w 1711 112 42.0 u 2496 119 22.0 N 2984 FERROMRNGRNESE NODULES LRB NUMBER CRUISE NUMBER LRTITUDE LONGITUDE DEPTH DEGREES MINUTES DEGREES MINUTES <m> B3-MN-R-90 RMPH 3P 15 4.0 N 125 5.0 W 4459 82-MN-B-4 BNFC 19 10 43.6 N 108 32.5 W 3172 82-MN-B-5 BNFC 54 11 51.6 N 110 0.1 W 3886 82-MN-B-6 BNFC 56 13 22.1 N 114 5.0 W 4105 83-MN-B-102 BNFC 5G 13 38.5 N 106 18.9 W 3220 83-MN-B-103 BNFC 14PG 10 42.0 N 109 6.0 W 5118 83-MN-B-104 BNFC 17P 11 10.6 N 109 36.3 W 3522 83-MN-B-105 BNFC 18PG 10 42.0 N 108 32.5 W 3551 83-MN-B-10? BNFC 58PG 13 32.1 N 114 20.7 W 4003 83-MN-B-109 BNFC 7DFF 14 31.8 N 117 19.6 W 3988 83-MN-B-110 BNFC 71FF 14 31.9 N 117 19.0 W 3964 B3-MN-B-111 BNFC 77FF 14 36.7 N 117 26. 1 W 4087 83-MN-B-112 BNFC 81G 14 35.1 N 118 33.3 W 4169 83-MN-B-113 BNFC 84P 15 5.6 N 120 44.9 W 4207 83-MN-B-114 BNFC 86P 14 35.1 N 121 3.7 W 4295 CRRR II 9 10 39 N 108 45 W 5276 CERES 9 13 0.0 N 100 50.0 W 2300 CERES 11 12 14.9 N 100 31.4 W 2850 CERES 10 12 57.7 N 100 53.9 N 3478 CERES 13 12 34.0 N 100 22.2 W 3317 CERES 14 12 1.4 N 101 35.6 W 3070 CERES 15 11 26.1 N 101 37.4 W 2940 CERES 16 12 4.4 N 101 34.5 W 3250 CERES 17 12 3.0 N 101 33.9 U 1920 CERES 18 11 57.4 N 101 37.2 U 2860 CERES 19 11 16.0 N 101 3.9 W 2930 CERES 20 11 14.3 N 101 7.6 U 2975 CERES 21 10 52.3 N 101 31.6 W 30B0 DWBD 1 21 27.0 N 126 43.0 W 4300 83-MN-J-123 JYN V 46PG 13 24.0 N 136 11.0 w 4822 83-MN-J-124 JYN V 47PG 14 39.0 N 135 4.0 W 4813 83-MN-J-125 JYN V 48PG 83-MN-J-126 JYN V 49PG 83-MN-J-127 JYN V 50PG MERO 29-52 MN 1 SUMMfl 2DB MN 2 SUMMR 3DB MN 3 SUMMR 4DB MN 4 SUMMR 5DB MN 5 SUMMR 6DB MN 6 SUMMfl 7DB MN 7 SUMMR 8DB MN 8 SUMMfl 9DB MN 9 SUMMR 10DB MN 10 SUMMR 12DB MN 11 SUMMfl 13DB MN 12 SUMMR 16DB MN 13 SUMMfl 17DB MN 15 SUMMfl 20DB MN 16 SUMMfl 21DB MN 17 SUMMfl 22DB MN 18 SUMMfl 23DB MN 19 SUMMfl 24DB MN 20 SUMMfl 25DB MN 21 SUMMfl 26DB MN 22 SUMMfl 27DB MN 24 SUMMfl 29DB MN 25 SUMMfl 30DB MN 26 SUMMfl 31DB MN 27 .SUMMfl 32DB MN 28 SUMMfl 33DB MN 29 SUMMfl 36DB MN 30 SUMMfl 37CC MN 31 SUMMfl 41DB MN 93 RP80C75 58-61 QBR • 8<C> RISE III 19 RISE III 20 15 54.0 N 133 57.0 Ul 4606 17 10.0 N 132 50.0 Ul 5188 18 16.0 N 131 46.0 Ul 5210 9 56.4 N 137 48.1 Ul 4930 14 58.2 N 116 13.7 Ul 3980 14 26.3 N 119 9.1 Ul 4072 14 12.4 N 118 52.5 1*1 3980 13 54.3 N 120 48.8 Ul 4255 13 40.4 N 122 18.4 Ul 4255 14 14.8 N 123 42. 1 Ul 4438 15 6.0 N 125 10.0 W 4392 15 7.9 N 125 7.0 Ul 4300 15 9.0 N 125 8.5 Ul 4392 15 8.9 N 125 9.7 W 4002 15 2.6 N 125 8.3 Ul 4302 13 15.4 N 126 48.0 Ul 4758 13 8.5 N 128 36.1 N 4712 20 55.8 N 113 57. 1 Ul 3568 20 54.5 N 113 57.5 Ul 3614 20 57.3 N 113 57.5 N 3660 20 56.6 N 113 55.9 N 3568 20 52.9 N 113 58. 1 Ul 3660 20 57. 1 N 113 59.3 Ul 3660 20 56.1 N 113 58.3 Ul 3660 20 56.3 N 113 58.3 Ul 3660 20 58.3 N 113 59.5 Ul 3642 20 54.8 N 113 58.2 Ul 3623 20 57.8 N 113 56.0 Ul 3861 20 55.0 N 113 55.9 Ul 3697 20 57.0 N 113 57.6 Ul 3687 19 36.5 N 115 18.3 Ul 3770 19 39.8 N 115 18.3 Ul 3770 12 31.8 N 122 27.5 Ul 4483 15 20.6 N 125 26.8 Ul 4414 10 24.0 N 108 26.0 Ul 3700 14 43.0 N 102 33.5 Ul 2260 14 43.5 N 102 34.5 Ul 1843 RISE III 24 13 1.3 N 100 49.0 W 2308 RISE III 28 13 46.0 N 101 52.3 W 1693 82-MN-S-74 STYX 2FFGB 23 43.0 N 124 6.0 W 3787 82-MN-S-75 STYX 3FFGB 20 4.0 N 130 5.0 W 4959 TRIPOD 4 20 45.0 N 114 27.0 W 3840 1.8 APPENDIX C THE CONCENTRATIONS OF THE MAJOR ELEMENTS AND THE TODOROKITE/8Mn02 RATIOS FOR CRUST AND NODULE SAMPLES FROM SURVEY REGION A The abundance of each of the major elements present in the crusts and nodule samples are given as weight percents. The abundances of todorokite to 8Mn0 2 is given as a ratio and therefore has no units. FERROMANGANESE CRUSTS LAB DODO DODO DODO DODO DODO DODO DODO DODO DODO DODO DODO NUMBER 6 D-1 7 D-1 7 D-2 7 D-3 8 D-1 8 D-2 8 D-3 9-1 D-1 9-1 D-2 9-1 D-3 9-2 D-1 DEPTH <m> 3400 750 750 750 1317 1317 1317 3720 3720 3720 3350 Si 9.24 1.11 1.14 0.92 3.30 3.21 5.31 15.09 15.66 3.43 14.05 Ti 1.21 0.62 0.75 0.86 0.85 0.97 0.85 1.09 0.97 0.89 0.94 RI 2.09 0.86 0.20 0.15 0.94 0.72 1.92 5.73 5.60 0.42 5.67 Fe 15.46 5.95 8.71 10.03 11.93 12.15 11.83 10. 13 9.96 17.12 10.59 Mn 9.13 21.56 18.71 20.91 17.85 17.38 14.52 5.92 5. 15 15.03 5.17 Mg 1.98 2.04 1.01 1.11 1.02 0.97 0.98 1.39 1.21 0.81 1. 19 Ca 2.35 8.46 8.21 4.64 2.42 2.02 3.63 2.52 4. 15 1.88 5. 15 Na 1.81 0.72 1.43 1.44 2.42 2.07 2.51 2.07 1.80 1.40 1.77 K 0.72 0.42 0.32 0.38 0.78 0.53 1.00 1.31 2.03 0.27 1.01 P 0.26 2.72 2.55 1.21 0.43 0.36 0.90 0.38 0.98 0.37 1. 15 Co 0.18 0.39 0.41 0.61 0.45 0.63 0.28 0. 17 0. 15 0.37 0. 12 Ni 0.11 1.23 0.48 0.49 0.36 0.35 0.31 0.08 0.07 0.17 0.05 Cu 0.01 0.22 0.05 0.04 0.09 0.06 0.11 0.05 0.05 0.02 0.02 Zn 0.03 0.11 0.04 0.04 0.04 0.04 0.05 0.02 0.02 0.04 0.03 Ba 0.09 0.21 0. 16 0. 14 0.19 0.77 0.40 0.09 0.08 0. 14 0.08 TOD/DEL 0.00 0.74 0.00 0.00 0.09 0.00 0.09 0.00 0.00 0.00 0.00 LHB DODO DODO DODO MP MP STYX STYX STYX 7T0W 7T0W 7T0W NUMBER 9-2 D-2 13 D-l 13 D-2 25-F1 25-F2 2 D-l 2 D-2 2 D-3 123 D-l 129 D-l 129 D-2 DEPTH <m> 3350 3148 3148 1740 1740 1B05 1805 1805 1604 1563 1563 Si 21.28 7.84 3.57 5.58 3.73 3.07 2.02 2.17 15.57 1.33 1.05 Ti 0.82 1.57 1.07 0.95 0.89 0.92 0.96 1.00 1.36 0.61 0.99 HI 8.9? 2.34 0.69 1.66 1.07 0.58 0.21 0.24 5. 15 0.40 0. 1? Fe 6.47 16.04 16.31 13.22 12.43 13.41 12.31 12.94 8.38 7.71 11.72 Mn 1.71 10.60 15.43 14.31 17.76 18.00 20.16 19.30 1.02 17.52 20.80 Mg 1.43 1.21 0.90 1.02 1.28 1.00 0.88 0.91 4.95 1.19 1.10 Ca 4.83 1.99 1.80 2.75 2.25 2.05 2. 11 2.07 10.69 9.90 2.32 Na 3.03 1.80 1.51 2.32 1.89 1.55 1.27 1.43 1.54 0.84 0.69 K 1.70 0.80 0.38 0.54 0.49 0.43 0.35 0.32 1.13 0.35 0.35 P 0.53 0.36 0.31 0.64 0.36 0.32 0.30 0.31 2.80 3.23 0.34 Co 0.03 0.24 0.38 0.50 0.78 0.60 0.82 0.78 0.06 0.52 0.87 Ni 0.01 0.20 0.20 0.23 0.33 0.31 0.36 0.32 0.06 0.60 0.42 Cu 0.00 0. 11 0.08 0.03 0.03 0.02 0.04 0.02 0.00 0.06 0.05 Zn 0.01 0.05 0.04 0.03 0.04 0.03 0.03 0.03 0.04 0.07 0.05 Ba 0.05 0.15 0.16 0.11 0.10 0.13 0.12 0.13 0.05 0.17 0. 17 TOD/DEL 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.14 0.01 LHB 7T0U 7T0W 7T0W 7T0N 7T0W NUMBER 129 D-3 130 133 D-1 133 D-2 137 D-1 DEPTH <m> 1563 1519 1488 1488 1750 Si 0.52 1.16 1.14 0.90 5.30 Ti 0.92 0.79 0.35 0.23 0.90 Bl 0.01 0.14 0.53 0.47 1.64 Fe 10.32 10.22 5.26 4.00 11.81 Mn 22.47 23.76 18.76 9.79 12.97 Mg 1.00 1.17 1.59 1.28 1.07 Ca 2.67 2.29 14.34 24.88 7.12 Na 0.9B 1.60 1.10 1.04 1.25 K 0.34 0.42 0.41 0.18 0.69 P 0.42 0.34 5.02 9.33 2.34 Co 0.98 0.92 0.34 0.31 0.44 Ni 0.46 0.63 0.82 0.58 0.32 Cu 0.30 0.02 0.08 0.04 0.06 Zn 0.07 0.06 0.0B 0.07 0.05 Ba 0.17 0. 17 0.43 0.32 0.28 TOD/DEL 0.00 0.00 0.43 0.52 0.03 7T0W 7T0W 7T0W 7T0N 7T0W 7T0W 17 D-2 137 D-3 142 D-1 143 D-1 143 D-2 144 D-1 1750 1750 2139 1805 1805 1690 1.81 2.45 3.09 2.43 3.38 6.34 0.79 0.59 0.90 0.87 0.87 1.17 0.38 0.67 0.66 0.56 0.63 1.61 10.85 7.59 12.76 11.71 13.27 14.42 15.59 13.39 17.19 17.47 17.90 13.67 0.90 0.79 0.85 1.04 1.05 1.15 9.18 13.80 2.78 4.65 2.00 1.92 0.84 1.20 1.66 1.51 1.32 1.35 0.34 0.41 0.40 0.41 0.38 0.60 2.96 4.70 0.60 1.31 0.37 0.36 0.47 0.42 0.64 0.50 0.64 0.43 0.37 0.34 0.31 0.39 0.36 0.25 0.04 0.05 0.04 0.09 0.04 0.02 0.04 0.03 0.03 0.05 0.04 0.04 0.24 0.12 0.16 0.21 0.13 0.13 0.06 0.00 0.00 0.00 0.00 0.00 LRB 7T0W 7T0W NUMBER 144 D-2 144 D-3 DEPTH <m> 1690 1690 S i 4 .52 7 .53 T i 1.08 0 .65 R l 1.01 2 .77 Fe 14.93 9 .99 Mn 15.37 17.03 Mg 1.04 1.63 Ca 1.97 1.40 Na 1.17 1.79 K 0 .43 0 .83 P 0 .37 0 .17 Co 0 .53 0 .23 N i 0 .25 0 .62 Cu 0 .03 0 .34 Zn 0 .04 0 .04 Ba 0 .15 0 .15 TOD/DEL 0 .07 0.91 FERROMRNGRNESE NODULES LRB D D D DODO DODO DODO DODO DODO DODO DODO DODO NUMBER 24 25 26 11 D-1 11 D-2 12-2 D-1 12-2 D-2 14-2 D-1 14-2 D-2 14-2 D-3 15 D-1 DEPTH <m> 5170 5170 5220 4630 4630 5040 5040 4868 4868 4868 5032 Si 7.45 4.09 7.63 8.32 8.89 8.23 7.59 2.30 6.42 2.73 6. 16 Ti 0.67 1.03 0.65 1.20 0.88 1.09 1.31 1.03 1.16 0.99 1. 13 RI 1.99 1.24 2.38 2.5B 3.28 2.77 2.24 0.36 1.82 0.58 1.79 Fe 14.19 14.13 9.83 14.32 12.18 13.19 16.06 15.44 15.34 15. 10 15.08 Mn 13.64 17.63 18.86 10.87 11.50 11.69 10.65 17.31 11.41 17. 19 13.65 Mg 1.07 1.15 1.64 1.08 1.00 1.05 1.09 0.84 0.97 0.92 0.98 Ca 1.98 1.85 1.67 2.59 2.34 2.04 1.B6 1.98 3.08 2.04 1.95 Na 1.65 1.74 1.03 2.67 1.75 2.66 2.51 1.32 1.3B 1.31 1.49 K 1.06 0.49 0.78 0.83 0.82 0.99 0.84 0.32 0.75 0.39 0.68 P 0.34 0.26 0.17 0.57 0.41 0.34 0.33 0.29 0.84 0.31 0.32 Co 0.14 0.37 0.22 0.30 0.24 0.28 0.29 0.40 0.29 0.39 0.29 Ni 0.20 0.33 0.55 0. 15 0.17 0.15 0. 10 0.23 0.14 0.25 0. 18 Cu 0.23 0.20 0.43 0.06 0.09 0.06 0.04 0.08 0.07 0.09 0.10 Zn 0.04 0.04 0.05 0.03 0.03 0.03 0.03 0.04 0.03 0.03 0.03 Ba 0.17 0.13 0.16 0. 12 0.12 0.11 0. 13 0.17 0.13 0.19 0. 15 TOD/DEL 0.00 0.12 0.85 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 LRB DODO DODO NUMBER 15 D-2 15 D-3 DEPTH <n>> 5032 5032 S i 3 .80 2 .39 T i 1.13 1-21 R l 0 .95 0 .57 Fe 13.46 12.13 Mn 18.24 18.04 Mg 1.07 0 .96 Ca 1.93 2 .03 Na 1.65 1.41 K 0 .53 0 .43 P 0.24 0 .26 Co 0 .39 0 .53 Ni 0 .28 0 .33 Cu 0 .07 0 .06 Zn 0.04 0 .03 Ba 0 .15 0 .16 TOD/DEL 0 .00 0 .00 DODO DODO DODO 3 D - l 15-3 D-2 15-3 D-3 5032 5032 5032 9 .84 13.08 9 .52 0.41 0.56 1.02 3 .46 5.22 3 .50 6 .78 7.78 10.63 7.84 9 .49 11.69 0 .85 1.31 1.35 10.44 1.76 2 .88 1.83 2 .05 1.37 1.54 1.85 1.14 3 .73 0.38 0 .62 0 .15 0. 14 0 .25 0 .18 0 .25 0 .23 0 .09 0 .15 0 .12 0 .02 0 .03 0 .03 0 .08 0 .09 0 .12 0 .00 0 .00 0 .00 S S N 41 76 80 5304 5330 5127 5 .68 8 .62 6 .95 0 .83 0 .47 0 .35 1.75 3 .06 2 . 4 9 10.80 6 .83 5 .05 18.67 19.94 24 .14 1.45 1.86 1.98 1.64 1.59 1.55 1.25 1.87 2.01 0 .57 1.25 0 .85 0.21 0. 18 0 .16 0 .27 0 .23 0. 14 0 .56 0 .88 1.04 0 .30 0 .67 1.02 0.04 0 .07 0 .09 0. 15 0 .10 0 .23 0 .59 0 .95 1.48 W N U 81 82 83 5133 5123 5221 6 .66 6 .99 6.66 0 . 4 ? 0 .46 0.88 2 . 5 0 2 .52 2 .27 6 .84 6 .53 10.15 2 2 . 5 0 24 .54 18.30 2 . 0 3 2 .17 1.61 1.61 1.58 1.99 2 . 2 2 2 . 1 3 1.98 0 .83 0 .84 0 .79 0 . 17 0. 16 0.34 0 . 18 0. 19 0.28 0 . 9 9 1.07 0.5B 0 .76 0.91 0.34 0 .08 0 .09 0 .05 0 . 16 0 .15 0 .17 1.00 0 .52 0 .45 LRB L4 14 14 14 J J J J J MN MN NUMBER 86 87 88 89 118 119 120 121 122 32 33 DEPTH <m> 5221 4B39 4839 4992 4813 5073 5036 5285 5539 4941 4762 S i 6 .12 6.34 5.34 19.26 8 .47 4 .33 5 .06 10.14 8. 19 14.37 4 .87 T i 0.91 0.72 0.74 0 .39 0.51 0.42 0 .69 0 .34 0 .64 1.24 0 .83 RI 2 .08 2 .09 1.80 3 .80 2.56 1.77 1.47 3 .45 2 .48 4 .88 1.49 Fe 11.50 9.62 9 .42 11.32 6.56 5 .83 10.52 5 .90 8 .28 12.77 11.53 Mn 20 .57 20.50 21 .49 0.46 15.23 25.34 19.17 19.51 17.66 7 .47 20 .38 Mg 1.81 1.85 1.72 2 .06 2.04 2 .22 1.68 2.01 1.67 1.73 1.36 Ca 1.70 2.18 1.87 6 .40 3.67 1.50 2 .17 1.50 1.55 1.33 2.21 Na 1.23 1.61 1.91 1.46 3.10 4 .48 2 .82 4 .44 2 .98 2 .44 0 .77 K 0 .66 0.74 0 .69 2 .06 0.86 0.92 0 .5B 1.58 1. 10 1.49 0 .52 P 0 .23 0.19 0 .18 1.88 0.18 0 .15 0 .32 0. 17 0 .20 0 .17 0 .20 Co 0.31 0.25 0 .25 0.01 0.17 0 .17 0 .23 0. 19 0 .23 0 .13 0 .29 Ni 0 .64 0.77 0 .74 0 .06 0.64 1.01 0 .63 0 .83 0 .66 0 .23 0 .53 Cu 0 .36 0 .45 0 .44 0 .06 0.40 0 .89 0 .39 0 .69 0 .35 0 .15 0 .38 Zn 0 .06 0.07 0 .06 0 .02 0.05 0 .09 0 .05 0 .07 0 .05 0 .03 0 .05 Ba 0 .18 0.19 0 .18 0 .03 0.21 0.22 0 .14 0. 16 0. 18 0.08 0 .16 TOD/DEL 0.51 0.33 0.11 0 .00 0.86 1.44 0 .32 1.30 0 .00 0.54 0 .35 LRB MN MN MN MN MN MN MN MN MN MN MN NUMBER 34 35 36 37 38 39 40 41 42 43 44 DEPTH <m> 4682 4674 5128 5003 5036 4833 5126 5062 5128 5104 5033 Si 4.84 5.57 6.76 7.42 7.55 6.38 5.28 5.40 16.44 4.79 6.83 Ti 0.85 0.70 0.39 0.38 0.72 0.44 0.36 0.37 0.35 0.3? 0.26 Rl 1.60 2.35 2.76 2.81 2.56 2.54 2.24 2.24 4.36 2.09 2.87 Fe 12.50 10.16 6.56 5.81 10.78 6.39 5.34 4.99 9.57 5.16 4.01 Mn 19.83 21.07 23.47 24. 12 18.84 23.97 27.65 27.51 9.04 28.08 26.46 Mg 1.35 1.65 2.08 2.21 1.73 2. 17 2.28 2.26 1.32 2.08 2.25 Ca 1.B2 1.61 1.52 1.57 1.50 1.56 1.52 1.37 1.58 1.40 1.54 Na 0.96 1.62 1.30 0.71 0.71 0.71 0.38 0.65 3.14 0.80 0.82 K 0.53 0.73 0.72 0.77 0.90 0.81 0.71 0.75 1.15 0.73 0.73 P 0.22 0.19 0.14 0.14 0.20 0. 15 0.13 0. 13 0.16 0.14 0.14 Co 0.28 0.25 0.17 0. 17 0.26 0.19 0.17 0. 16 0.10 0.19 0.14 Ni 0.49 0.72 1.14 1.24 0.70 1. 14 1.32 1.36 0.24 1.21 1.45 Cu 0.34 0.52 1.15 1.22 0.47 1.02 1.04 1.06 0.16 1.09 1.25 Zn 0.05 0.06 0.09 0. 11 0.06 0.11 0.14 0.13 0.03 0.10 0.12 Ba 0.14 0.14 0.13 0. 14 0.14 0.15 0.15 0.16 0.09 0.22 0.22 TOD/DEL 0.26 0.58 1.34 1.01 0.64 1.45 1.17 1.42 0.00 1.40 1.48 LRB MN MN MN MN MN NUMBER 45 46 47 48 49 DEPTH <m> 4943 5036 5128 5124 5344 S i 5. 57 7 . 65 6. 09 6. 63 5. 29 T i 0. 42 0. 3? 0. 38 0. 39 0. 34 R l 2 . 15 2 . 84 2. 34 2. 51 2 . 23 Fe 6. 10 5. 63 5. 49 5. 89 5. 26 Mn 27. 37 23 . 15 25 . 91 25. 19 26. 22 Mg 2 . 12 2 . 20 2. 14 2. 32 2 . OB Ca 1. 60 1. 90 1. 44 1. 54 1. 43 Na 0. 13 0. 89 0. 45 0. 80 0. 64 K 0. 70 0. 82 0. 70 0. 74 0. 68 P 0. 15 0. 27 0. 12 0. 15 0. 12 Co 0. 21 0. 16 0. 21 0. 24 0. 21 Ni 1. 19 1. 19 1. 25 1. 20 1. 15 Cu 0. 85 0. 84 0. 97 0. 99 1. 02 Zn • . 11 0. 10 0. 11 0. 10 0. 11 Ba 0. 18 0. 21 0. 16 0. 14 0. 19 TOD/DEL 1. 04 1. 01 1. 50 1. 32 1. 55 MN MN MN MN MN MN 50 51 52 53 54 55 5314 5503 5311 5003 5003 5303 6 .09 6 .92 7 .33 9 .18 6 .70 5 .84 0.41 0 .40 0 .42 0 .33 0 .32 0 .45 2 .50 2 .70 2 . 7 9 2 .43 2 . 6 5 2 .48 5.66 5.71 6.31 4 .75 4 .48 6 .47 24.66 24 .20 2 3 . 3 5 23 .17 25 .85 2 2 . 4 9 2.31 2 .27 2 .04 1.79 2 .25 1.97 1.60 1.73 1.54 1.71 1 .5? 1.49 0 .45 0.51 0 .65 2 .04 0 .59 0 .60 0 .76 0 .80 0 .84 0.74 0 .75 0 .66 0.14 0 .20 0 .17 0 .12 0 .14 0. 15 0 .23 0.21 0 .18 0 .17 0 .15 0 .24 1.13 1. 14 1.04 1.07 1.35 1.05 0 .99 1.02 0 .97 1.11 1.18 0 .84 0 .13 0 .12 0 .12 0 .12 0 .12 0. 11 0 .13 0. IB 0. 18 0.11 0 .20 0 . 16 1.26 1.23 1. 12 1.15 1.30 1.27 LflB MN MN MN MN MN MN PLDS NUMBER 56 86 89 90 91 92 8 D-1 DEPTH <m> 5128 4908 5005 5039 5033 4928 4500 S i 5 . 12 10. 54 5. 60 6. 08 12. 82 5. 72 8. 25 T i • . 32 0. 54 0. 26 0. 26 0. 53 0. 86 0. 39 RI 2 . 13 3. 53 2. 47 2. 52 4 . 19 1. 51 2. 46 Fe 5 . 00 9 . 11 3. 99 4. 08 7. 43 10. 53 6. 11 Mn 26. 53 14. 13 27. 06 26. 60 13. 01 19. 85 21. 73 Mg 1. 98 1. 53 2. 26 2. 34 1. 37 1. 37 2 . 01 Ca 1. 52 4 . 40 1. 49 1. 54 1. 14 1. 60 1. 43 Na • . 61 1. 47 0. 55 1. 71 0. 88 0. 91 1. 78 K , 0. 63 0. 74 0. 70 0. 80 2 . 15 0. 59 1. 24 P 0. 13 1. 19 0. 13 0. 15 0. 18 0. 18 0. 18 Co • . 18 0. 18 0. 14 0. 14 0. 19 0. 30 0. 20 Ni 1. 11 0. 59 1. 37 1. 42 0. 57 0. 72 0. 95 Cu 1. 11 0. 50 1. 41 1. 74 0. 43 0. 46 0. 73 Zn 0. 12 0. 08 0. 14 0. 38 0. 08 0. 07 0. 10 Ba 0. IB 0. 10 0. 18 0. 20 0. 12 0. 17 0. 17 TOD/DEL 1. 33 0. 78 1. 59 1. 51 2 . 45 0. 61 1. 55 1.9 A P P E N D I X D THE CONCENTRATIONS OF THE MAJOR ELEMENTS AND THE TODOROKrrE/5Mn02 RATIOS FOR CRUST AND NODULE SAMPLES FROM SURVEY REGION B The abundance of each of the major elements present in the crusts and nodule samples are given as weight percents. The abundances of todorokite to 5Mn0 2 is given as a ratio and therefore has no units. FERROMRNGRNESE CRUSTS LRB B CHRR CERS CERS CERS CERS CERS CERS CERS CERS DPSN NUMBER 106 6 D- l 1 D - l 1 D-2 1 D-3 1 D-4 5 D - l 5 D-2 5 D-3 6 D - l 3 D - l DEPTH <m> 2693 1228 3424 3424 3424 3424 2700 2700 2700 1950 3240 S i 8.41 12.56 7 .40 8 .89 8 .67 8 .36 9 .98 7 .46 9 . 17 5 .76 12.01 T i 0 .34 0.98 0 .20 0 .27 0 .22 0.21 0 .28 0 .24 0 .27 0 .47 0 .49 Rl 2 .06 4 .30 1.68 2 .35 2.11 1.92 2 .28 1.71 2 .12 1.41 3 .39 Fe 15.23 8.30 17.54 16.06 17.25 17.30 19.36 18.51 18.54 16.54 13. 16 Mn 8 .78 11.79 11.30 11.82 10.57 11.40 7 .88 10.36 8 .56 13.26 11.31 Mg 1.07 2.05 1.09 1.38 0 .92 1.12 0 .99 1.08 1.13 1.02 2.01 Ca 7 .67 2.51 1.38 1.76 1.35 1.37 1.48 1.48 1.63 2 .08 2 .90 Na 1.43 2.87 1.29 1.42 1.87 1.46 2 .06 1.90 1.45 1.79 2 .42 K 0 .59 1.81 0.51 0 .60 0 .66 0.61 0 .58 0 .52 0 .53 0 .49 0 .57 P 0 .22 0.94 0.34 0 .29 0 .35 0.32 0 .33 0 .34 0 .32 0 .39 0 .20 Co 0 .10 0.00 0 .03 0 .03 0 .03 0 .03 0 .04 0 .05 0 .05 0 .16 0 .04 Ni 0 .17 0.00 0 .23 0 .33 0. 19 0 .26 0 .10 0 .18 0. 12 0 .18 0 .26 Cu 0 .19 0.00 0 .10 0 .17 0 .09 0 .13 0 .04 0 . 0 7 0 .05 0.04 0 .14 Zn 0 .05 0.02 0 .05 0 .05 0.04 0 .05 0 .05 0 .06 0 .05 0 .04 0 .04 Ba 0 .19 0 .13 0 .12 0. 12 0 .13 0.12 0. 14 0 . 14 0. 13 0 .14 0.21 TOD/DEL 0 .24 2.82 0 .14 0 .65 0 .09 0 .33 0 .00 0. 13 0. 16 0 .00 1.17 LRB DPSN DPSN DPSN DPSN DPSN NUMBER 3 D-1 3 D-2 3 D-2 3 D-3 3 D-3 DEPTH <m> 3240 3240 3240 3240 3240 S i 13.15 6 .92 13.10 13.16 13.63 T i 0 .59 0. 19 0 .58 0.31 0 .33 HI 3 .75 1.68 3 .85 4 .59 4 .49 Fe 11.56 15.08 13.10 10.96 12.70 Mn 10.14 14.42 8 .70 9 .03 7 .33 Mg 2 .27 1.04 2 .04 3.32 3.11 Ca 3 .80 1.72 3 .58 4 .69 4 .18 Na 1.92 1.54 1.90 1.56 1.82 K 0 .44 0 .50 0 .50 0 .35 0 .43 P 0 .19 0 .26 0.21 0 .16 0.17 Co 0 .02 0.04 0 .04 0 .03 0.04 Ni 0 .27 0 .35 0 .19 0.22 0 .17 Cu 0 .14 0 .16 0 .10 0.08 0.09 Zn 0:04 0.06 0 .03 0.04 0.04 Ba 0 .13 0 .19 0 .15 0 .10 0 .13 TOD/DEL 0 .86 0.42 0 .63 0.51 0 .46 DPSN DPSN DPSN DPSN DPSN HEN SMT 3 D-4 4 D-1 5 D-1 5 D-2 5 D-3 D-3 3240 2957 3124 3124 3124 64 8 .58 10.89 7 .27 8 .14 9 .38 10.52 0.31 0 .42 0 .23 0 .27 0 . 3 5 0. 11 2 .34 2 .88 1.86 2 .04 2 . 17 0 .88 13.21 15.06 14.90 16.50 13 .79 12.67 14.89 10.12 13.32 12.02 14 .37 19.72 1.50 1.64 1.11 1. 12 1.81 2 .18 2 .24 2 . 6 8 1.87 1.81 2 . 3 8 0.68 1.77 1.66 2 .39 1.28 1.88 1.12 0 .58 0 .54 0 .58 0 .50 0 .56 2.34 0 .24 0 . 2 3 0 .27 0 .26 0 .24 0 .15 0 .03 0 .03 0 .04 0 .04 0 . 0 3 0.06 0.34 0 .23 0 .30 0 .24 0 . 2 9 0.20 0.21 0 .10 0. 13 0. 12 0 . 1 5 0.01 0 .05 0 .05 0 .05 0 .05 0 .06 0.02 0 .23 0. 15 0 .16 0. 18 0 . 2 3 0 .65 1.04 0.51 0 .17 0 .63 1.17 0.41 LRB QBR QBR QBR QBR QBR QBR RISE 3 RISE 3 RISE 3 RISE 3 RISE 3 NUMBER 1 D - l 2 D - l 7 D - l 7<B) D - l 7<B) D-2 22 D- l 3 D - l 3 D-2 6 D - l 6 D-2 6 D-3 DEPTH <m> 2550 2550 3000 3000 3000 1680 2095 2095 2703 2703 2703 S i 12.78 11.36 10.95 12.68 20.64 1.25 0 .03 0 .00 13.83 8 .45 8.5B T i 0.71 0 .70 0.84 0 .30 1.37 0.04 0 .04 0 .02 0.41 0 .23 0.22 R l 4 .16 3 .27 2 .99 1.14 5 .78 0 .07 0 .00 0 .00 4 .33 1.92 2 .06 Fe 11.84 13.79 13.75 13.58 11.64 4 .77 0 .23 0 . 1 9 11.83 18.05 17.65 Mn 8 .73 8 .43 9 .87 13.89 2 .08 33.60 42.34 42.31 8.71 10.37 10. 18 Mg 2 .38 1.86 2 .06 2 .25 3.54 1.98 1.68 1.19 2 .80 0.91 0.90 Ca 4 .47 2 .62 3 .30 1.50 7 .09 1.53 2 .94 2 . 5 5 4 .36 1.64 1.61 Na 1.59 1.97 2.51 1.59 2 .32 2.31 2 .08 3 .88 2 .48 1.54 1.85 K 0 .46 0 .95 0.41 1.72 0 .32 0 .90 0 .72 0 .50 0 .45 0 .50 0 .53 P 0 .18 0 .23 0.22 0 .10 0 .12 0.12 0 .02 0 .02 0 .20 0 .35 0.36 Co 0 .07 0.12 0.08 0 .02 0 .02 0.00 0 .00 0.01 0 .05 0 .04 0 .03 Ni 0 .15 0.12 0.21 0 .12 0 .04 0 .12 0 .03 0.01 0.21 0 .13 0.14 Cu 0 .10 0 .02 0. 12 0 .05 0 .02 0.01 0 .00 0 .00 0.11 0 .06 0 .07 Zn 0.01 0 .02 0.04 0.04 0.01 0.06 0.01 0 .00 0 .03 0 .04 0.04 Ba 0 .07 0 .09 0. 13 0 .08 0 .07 0 .09 0 .33 0 . 11 0 .15 0 .15 0.14 TOD/DEL 0 .00 0 .00 0 .56 0 .00 0 .08 0.19 1 .6? 1.33 0 .87 0 .05 0 .07 LRB RISE 3 RISE 3 RISE 3 SIQR SIQR SIQR SIQR SOTW 9 TRIPOD TRIPOD TRIPOD NUMBER 7 D-1 B D-1 13 D-1 4 D-1 4 D-2 4 D-3 4 D-4 32 D-1 2 D-1 2 D-2 3 D-1 DEPTH <m> 2183 2450 2251 3325 3325 3325 3325 3400 1711 1711 2496 S i 5 .37 11.32 8 .67 7.61 6 .83 6 .90 6 .68 22 .79 3 .67 3 .16 10.66 T i 0 .29 0 .37 0 .42 0.29 0 .27 0 .25 0 .27 0.81 0 .45 0 .48 0 .32 fll 1.15 3 .23 2 .35 1.78 1.66 1.59 1.61 7.41 0 .55 0.34 2 .90 Fe 20.66 16.97 16.03 17.61 17.34 17.96 17.21 8 .22 17.19 17.91 10.37 Mn 11.11 7 .15 10.46 11.54 12.89 12.71 13.45 0 .53 15.50 15.88 13.33 Mg 0.87 1.81 1.53 1.11 1.05 1.02 1.02 5 .77 0 .85 0 .85 2.11 Ca 1.74 2 .93 2 .79 1.77 1.67 1.60 1.68 7 .79 1.88 1.88 1. 19 Na 1.13 1.56 1.43 1.35 1.43 1.23 1.02 1.91 2 .44 2 .54 1.64 K 0 .39 0 .50 0 .53 0.48 0 .48 0 .47 0 .48 0. 19 0 .52 0 .42 0 .99 P 0.41 0 .30 0 .33 0.27 0 .29 0 .27 0 .28 0 .05 0 .50 0 .50 0. 17 Co 0.06 0.04 0 .06 0.05 0.04 0.04 0 .04 0 .02 0 .26 0 .28 0 .18 Ni 0 .14 0 .07 0 .15 0 .23 0 .27 0 .29 0 .27 0.01 0 . 18 0. 18 0 .44 Cu 0 .03 0 .02 0 .03 0.11 0 .13 0 .15 0. 12 0 .00 0 .00 0 .00 0. 11 Zn 0.04 0 .03 0 .05 0.04 0 .05 0 .05 0 .06 0 .00 0 .03 0 .03 0 .05 Ba 0 .13 0.11 0. 11 0 .15 0 .15 0. 18 0. 15 0 .02 0 . 14 0 .16 3. 10 TOD/DEL 0.00 0 .00 0 .00 0.03 0 .20 0.24 0 .16 0 .00 0 .00 0 .00 2 .13 LRB TRIPOD TRIPOD TRIPOD NUMBER 3 D-2 9 D-1 9 D-2 DEPTH <m> 2496 2984 2984 S i 7 .60 19.42 8 .93 T i 0 .42 1.58 0 .77 RI 1.61 7.37 2.71 Fe 15.95 9 . 14 11.76 Mn 14.44 1.94 12.95 Mg 1.21 3 .09 1.47 Ca 1.46 4 .53 1.74 Na 1.33 2 .58 1.83 K 0 .62 1.48 0.92 P 0 .32 0 .25 0 .20 Co 0 .22 0.04 0.21 Ni 0 .33 0 .06 0 .40 Cu 0 .04 0.04 0.24 Zn 0 .05 0.02 0 .05 Ba 0.21 0 .08 0.34 TOD/DEL 0 .55 0 .00 0.52 FERROMRNGRNESE NODULES LRB fl B B NUMBER 90 4 5 DEPTH <m> 4459 3172 3886 S i 6 .04 5 .85 5 .32 T i 0 .23 0 .36 0 .35 Rl 1.95 1.77 1.75 Fe 4 .60 11.21 8 .90 Mn 26 .79 21 .14 22. 14 Mg 1.97 1.43 1.58 Ca 1.47 2 .08 1.88 Na 2 . OB 2 .02 1.79 K 1.18 0 .57 0 .67 P 0 .13 0.24 0 .19 Co 0 .15 0 .07 0 .09 Ni 1.01 0 .82 0 .82 Cu 0 .85 0 .38 0 .52 Zn 0 .16 0 .09 0 .10 Ba 0 .25 0 .16 0.21 TOD/DEL 1.43 0 .57 0 .88 B B B B 6 102 103 104 4105 3220 5118 3522 5 .23 9 .70 20 .39 4 . 9 9 0 .29 0 .39 1.11 0 .28 1.81 2.28 4 .15 1.54 6 .97 14.85 11.10 7 .24 25.36 12.54 1.12 23.81 1.77 1.07 1.99 1.40 1.54 3.72 0 .83 1.59 1.92 1.77 2 .59 1.98 0 .80 0 .73 1.48 0 .67 0 .16 0.25 0 .07 0 .16 0 .10 0.09 0.02 0 .07 1.04 0 .15 0.02 0 .88 0.71 0 .15 0.08 0 .66 0 .10 0.04 0.02 0 .12 0 .26 0.17 0 .27 0 .26 1.21 0 .45 0 .00 0 .95 B B B B 105 107 109 110 3551 4003 3988 3964 10.07 7 .58 7 . 4 5 6 .37 0 .16 0.31 0 .30 0 .33 2 .76 2 .72 2 .50 2 .18 5.11 6.91 6 .64 7 . 7 ? 4.91 21 .83 2 4 . 0 5 23 . 16 1.23 2.11 1.97 1.81 13.04 1.36 1.46 1.57 2 .44 2 .35 2 . 2 2 1.93 1.22 1.01 1.02 0 .89 4.71 0 .16 0 .16 0 .17 0 .03 0. 10 0 . 15 0 .15 0.21 0 .93 0 . 8 9 0.91 0 .17 0 .54 0 . 6 0 0 . 5 ? 0 .04 0 .09 0 . 0 9 0 .08 1.28 0 .34 0 . 2 5 0 .34 0 .00 1. 12 1 .0? 0 .94 LRB B B B B CRRR CRRR CERS CERS CERS CERS CERS NUMBER 111 112 113 114 9 D-1 9 D-2 9 D-1 9 D-2 10 D-1 10 D-2 10 D-3 DEPTH <m> 408? 4169 4207 4295 5276 5276 2300 2300 3478 3478 3478 S i 5 .85 13.72 11.00 6 .67 6 .48 7 .22 7.24 14.46 4 .73 6.21 6 .74 T i 0 .30 0 .25 0.21 0 .30 0 .60 0 .49 0 .36 0 .47 0 . 15 0 .17 0. 19 RI 1.98 3 .87 3.28 2 .39 2 .20 2 .33 1.82 4 . 6 2 1.7B 2 .16 2 .34 Fe 7 .34 7 .64 5.72 5.29 10.44 9 .94 14.39 10.40 4 . 3 0 6 .70 8 .43 Mn 25 .04 14.31 19. B3 25 .75 19.12 20 .47 16.03 10.40 30 .65 26 .03 23 .39 Mg 1.73 1.96 1.90 1.97 1.37 1.53 1.67 3 .33 1.73 1.70 1.79 Ca 1.54 0 .99 1.15 1.44 1.52 1.36 1.36 4 .74 1.22 1.26 1.21 Na 2 .39 2 . 0 3 2 .30 1.60 1.88 1.91 1.55 1.58 1.55 2 .23 1.84 K 0 .89 1.89 1.54 1.07 0.71 0 .79 0 .58 0 .50 0 .74 0 .75 0.84 P 0. 17 0 .13 0.13 0 .13 0 .22 0 .19 0 .25 0 . 12 0 . 12 0 .16 0 .18 Co 0. 17 0. 11 0.11 0 .15 0 .07 0 .07 .0.13 0 .09 0.01 0.01 0 .02 Ni 1.05 0 .59 0 .75 1.12 0 .55 0 .60 0.61 0 .38 0 .44 0 .49 0 .45 Cu 0 .64 0.41 0.64 0 .76 0 .50 0 .65 0 .16 0. 10 0 .22 0.31 0 .29 Zn 0. 17 0.D7 0.21 0.11 0 .06 0 .07 0 .07 0 .04 0 .14 0.11 0 .09 Ba 0 .26 0 . 2 3 0 .36 0 .23 0 .20 0 .25 0 .22 0 . 19 0 . 12 0 .20 0 .29 TOD/DEL 0 .79 0 .88 1.47 1.11 1.19 1.25 1.19 1.25 0 .88 1.41 1.54 LHB CERS NUMBER 11 D - l DEPTH <m> 2850 S i 6 .45 T i 0 .20 Rl 1.88 Fe 9 .12 Mn 23 .12 Mg 2 .07 Ca 1.25 Na 0 .70 K 0 .78 P 0 . 1 ? Co 0 .03 Ni 0 .58 Cu 0 .32 Zn 0.11 Ba 0 .27 TOD/DEL 1.23 CERS CERS 13 D - l 13 D-2 3317 3317 4 .65 6.51 0 .16 0 .22 1.45 1.95 5.72 11.72 30.27 18.31 1.47 1.26 1.31 1.53 1.87 1.61 0 .59 0 .56 0 .13 0 .23 0.01 0 .03 0 .43 0 .53 0 .17 0 .18 0 .10 0 .12 0.12 0 .13 1.20 0.51 CERS CERS 14 D - l 15 D - l 3070 2940 2 .23 7.61 0 .09 0 .22 0.91 2 .24 1.65 10.41 39 .48 21 .37 1.68 1.99 1.29 1. 18 2 .15 1.52 0 .82 0 .77 0 .07 0 .17 0 .00 0 .07 0 .26 0 . 4 ? 0. 11 0 .27 0 .08 0 .07 0 .24 0.42 2 .36 1.50 CERS CERS 15 D-2 15 D-3 2940 2940 9 .26 9 .68 0 .20 0 .22 2 .66 2 . 6 9 12.70 9 . 0 9 15.91 19.98 1.92 1.87 1.36 1.26 1.92 1.40 0 .72 0 .80 0 .17 0 .15 0.04 0 .03 0 .43 0 .49 0 .18 0 .20 0 .07 0 .08 0 .22 0 .26 1.27 1.66 CERS CERS 16 D - l 16 D-2 3250 3250 5 .90 8 .35 0 .19 0 .17 1.78 1.92 12.66 13.31 18.58 15.77 1.54 1.43 1.42 1.27 1.60 1.58 0 .56 0 .77 0 . 2 3 0.21 0 .04 0 .02 0 .60 0 .38 0 .36 0 .17 0 .10 0 .08 0 .19 0 .15 1.16 0 .68 CERS CERS 16 D-3 17 D - l 3250 1920 6 .60 26 .84 0 .19 0 .13 1.93 0 .56 12.07 16.89 19.45 1.07 1.41 1.31 1.49 0 .18 1.84 0 .53 0 .57 1.63 0 .23 0 .10 0 .02 0 .03 0 .60 0 .04 0 .29 0 .00 0 .12 0.01 0 .14 0 .05 0 .82 0 .00 LRB CERS CER5 CERS CERS CERS CERS CERS CERS CERS CERS DNBD NUMBER 18 D-1 19 D-1 19 D-2 19 D-3 20 D-1 20 D-2 20 D-3 21 D-1 21 D-2 21 D-3 1-1 DEPTH <m> 2860 2930 2930 2930 2975 2975 2975 3080 3080 3080 4300 S i 6 .16 4 .56 3.24 5.42 6 .02 4. 14 4 .60 5 .24 4 .58 2 .38 14.42 T i 0 .18 0 .15 0 .13 0.21 0.21 0 .14 0 .17 0 .34 0 .17 0 .09 0 .55 RI 1.75 1.57 1.33 1.67 1.97 1.63 1.54 1.22 1.76 1. 14 5. 12 Fe 9 . 17 4 .24 2 .88 7.44 6 .68 3 .57 5 .89 15.90 4 . 5 3 1.82 8 .89 Mn 22 .52 31 .36 34 .25 25.31 26 .08 33 .45 29 .23 13.98 31 .07 37 .22 7 .82 Mg 1.33 1.54 1.51 1.61 1.92 2 .28 1.70 0 . 8 9 1.95 2. 13 0 .80 Ca 1.61 1.34 1.27 1.56 1.34 1.19 1.42 1.65 1.22 1. 15 1.49 Na 1.99 2 . 5 9 2 .93 1.94 1.02 1.27 1.60 1.58 1.45 1.37 2 .82 K 0 .63 0 .62 0.71 0 .67 0 .69 0 .83 0 .77 0 .46 0 .76 0 .84 2 .40 P 0 .20 0.11 0 .10 0.17 0.14 0. 10 0 .13 0 .32 0. 13 0 .08 0 .23 Co 0 .03 0 .02 0.01 0.03 0 .03 0 .00 0 .02 O.OB 0.01 0.01 0 .16 Ni 0 .69 0 .50 0 .45 0.76 0 .65 0 .63 0 .60 0 .23 0 .69 0 .56 0 .12 Cu 0 .28 0 .23 0 .13 0.32 0.31 0 .30 0 .23 0 .04 0 .32 0 .25 0.11 Zn 0 .12 0 .12 0.14 0 .19 0.11 0 .14 0 .12 0 . 0 3 0 . 12 0 .22 0 .02 Ba 0 .15 0 .19 0. 10 0 .16 0 .20 0.31 0 .23 0 .14 0 . 2 8 0 .29 0.31 TOD/DEL 1.08 2 .00 0 .39 1.11 1.57 2 .22 1.39 0 .00 2 . 2 3 2 .68 0 .00 LRB DWBD J J J J J MERO MERO MERO MN MN NUMBER 1-2 123 124 125 126 12? 2P-52-1 2 P - 5 2 - 2 2 P - 5 2 - 3 1 2 DEPTH <m> 4300 4822 4813 4606 5188 5210 4930 4930 4930 3980 4072 S i 27.51 10.42 6 .10 7 .65 6 .90 11.92 4 .37 10.65 7 . 0 5 5 .58 5 .03 T i 0 .26 0 .33 0 .45 0 .66 0 .52 0.41 0 .25 0 .38 0.21 0.21 0 .26 RI 1.58 3.57 2 .17 2 .53 2 .55 4 .30 1.70 3 .13 2 . 17 2 .04 1.89 Fe 8 .17 5.19 6 .36 9 .22 8 .03 8 .76 3 .90 6 .03 3 . 2 5 5 .72 5 .50 Mn 6.01 19.36 2 3 . 5 ? 16.70 21 .30 13.90 29.01 18.81 2 5 . 6 9 26 .13 27 .94 Mg 1.15 2.16 2. 16 1.56 2.01 1.71 2 .16 2 .03 1.69 1.84 1.76 Ca 0 .37 1.51 1.55 1.61 1.47 0 .96 1.35 1.38 1.62 1.50 1.40 Na 0.84 1.57 2 .58 3 .99 1.99 2 .54 1.48 1.92 2 . 0 2 1.31 0 .98 K 0 .98 1.40 1. 15 1.45 0 .88 1.96 0 .90 1.11 0 . 8 5 0 .70 0.71 P 0 .06 0.18 0 .20 0 .23 0. 1? 0. 1? 0 .13 0 .19 0 .12 0.14 0. 14 Co 0 .09 0.21 0 .23 0 .29 0 .27 0.21 0 .16 0.21 0 .14 0 .12 0 .12 Ni 0.31 0.91 0 .94 0.51 0 .87 0 .55 1.25 0 .87 1.31 1.08 1.07 Cu 0.14 0 .67 0 .60 0 .25 0 .59 0 .35 0 .96 0 .58 1.03 0 .89 0.74 Zn 0 .02 0.07 0 .07 0 .04 0 .06 0.04 0 .12 0 .07 0.11 0.11 0. 13 Ba 0 .56 0 .20 0 .29 0 .14 0.14 0 .20 0 .30 0 .27 0 . 2 5 0 .45 0 .27 TOD/DEL 0.11 0 .95 1.01 0 .44 0.91 0.91 1.77 1.43 1.39 1.35 1.19 LRB MN MN MN MN MN MN MN MN MN MN MN NUMBER 3 4 5 6 7 8 9 10 11 12 13 DEPTH <m> 3980 4255 4255 4438 4392 4300 4392 4002 4302 4758 4712 S i 12.20 8 .04 10.01 6.78 6 .63 6 .42 5 .50 5 .34 5 .99 7 .56 5.00 T i 0 .25 0 .28 0 .23 0 .37 0 .32 0 .35 0 .29 0.61 0 .32 0 .37 0 .29 R l 3.91 2 .69 2.91 2 .28 2 .22 2 .30 2 .12 1.77 2 .14 2 . 6 3 1.98 Fe 5 .70 6 .13 5.24 6 .15 6 .59 6 .39 5 .97 10.24 6 .34 5 .65 5.10 Mn 16.17 23 .76 21 .78 24.06 25 .49 25.04 26 .70 21 .82 26 .14 2 2 . 5 5 27 .56 Mg 1.67 2.11 2 .12 1.77 1.95 1.94 1.89 1.56 2 .10 1.83 1.80 Ca 1.08 1.39 1.16 1.48 1.48 1.46 1.38 1.60 1.40 1.54 1.49 Na 2 .38 0 .67 1.77 2.11 1.52 0 .76 0 .79 0 .93 0 .75 0.71 0 .67 K 2.01 1.06 1.38 0 .99 0 .95 0 .89 0 .67 0 .58 0 .77 0 . 8 7 0.61 P 0 .13 0.14 0 .16 0 .15 0 .16 0.14 0 .13 0 .20 0. 14 0 . 1 5 0.13 Co 0 .10 0 .19 0 .16 0.18 0 .25 0.21 0 .25 0.31 0 .26 0.21 0.23 Ni 0 .80 1.09 0 .77 0 .96 1.08 1.07 1.12 0 .79 1. 10 1. 12 1.23 Cu 0 .48 0.81 0 .76 0 .75 0 .76 0 .76 0 .78 v 0.41 0 .79 0 . 7 9 0.87 Zn 0 .08 0 .08 0 .07 0.08 0 .09 0 .10 0 .10 0 .06 0 .09 0 .08 0.10 Ba 0 .39 0 .22 0 .85 0 .25 0.21 0 .17 0 .23 0 .13 0 .22 0 .27 0.22 TOD/DEL 2 .49 1.40 1.81 1.01 1.33 1.35 1.27 0 .70 1.38 1.02 1.56 I LRB MN MN MN MN MN MN MN MN MN MN MN NUMBER 15 16 17 18 19 20 21 22 24 25 26 DEPTH <m> 3568 3614 3660 356B 3660 3660 3660 3660 3642 3623 3861 S i 6 .08 6 .67 7.12 6 .70 7 .10 6.12 7 .20 6 .62 6 .42 7 .24 3 .64 T i 0 .25 0 .26 0.21 0 .26 0 .24 0 .25 0 .25 0 .28 0 .26 0 .28 0.11 RI 1.89 1.99 2 .32 1.92 2 .18 1.78 2 .19 1.98 1.87 2 . 1 3 1.15 Fe 9 .18 8.82 7.08 9 .36 8.11 9 .35 8 .63 9 . 9 0 8 .64 10.31 2 . 0 7 Mn 23 .77 23.82 24 .57 23.14 24.01 24.68 23 .18 2 3 . 8 8 22 .79 21.51 12.44 Mg 1.63 1.7? 1.70 1.79 1.79 1.69 1.65 1.78 1.73 1.74 1.13 Ca 1.40 1.40 1.46 1.45 1.42 1.45 1.44 1.49 1.42 1.30 20 .62 Na 0.B2 0 .65 0 .87 0 .79 0.51 1.35 0 .87 0 . 8 5 0 .94 0 .87 1.19 K 0 .73 0 .80 0 .82 0.B2 0.81 0.73 0 .78 0 . 7 7 0 .76 0 .83 0.41 P 0 .17 0 .18 0 .15 0 .19 0 .17 0.18 0 .17 0 . 1 9 0 . 1 7 0 .19 8 . 13 Co 0.12 0 .10 0.08 0. 11 0. 10 0.12 0. 12 0 . 13 0. 11 0 .12 0 .06 Ni 0 .88 0.81 0 .89 0.82 0 .86 0 .86 0 .89 0 .80 0 .87 0 .68 0 . 5 ? Cu 0.51 0 .49 0.51 0 .52 0 .55 0.51 0 .53 0 .42 0 .50 0 .49 0 .53 Zn 0.11 0 .10 0 .10 0 .10 0 .10 0.11 0 .10 0 . 0 9 0.11 0 .07 0 .06 Ba 0 .16 0 .17 0 .20 0.18 0 .18 0.18 0 .19 0 .18 0. 16 0 .22 0 .07 TOD/DEL 1.07 1.16 0 .90 1.10 1.11 0.97 0 .96 0 .82 1.00 1.11 1.94 ID CO LRB MN MN MN MN MN MN QBR QBR RISE 3 RISE 3 RISE 3 NUMBER 27 28 29 30 31 93 8<C> D-1 8<C) D-2 19 D-1 20 D-1 24 D-1 DEPTH <m> 3697 36B7 3770 3770 4483 4414 3700 3700 2260 1843 230B S i 6.51 6 .28 6 .68 6.27 5 .24 5 .89 7 .42 6 .64 8 .72 9 .06 4.21 T i 0 .26 0 .24 0 .28 0.22 0 .32 0 .23 0 .46 0 .50 0 .56 0 .69 0 .12 RI 1.98 1.91 2 .10 2 .05 2.01 2 .16 2 .58 2 .22 2 .68 2 . 9 7 1.56 Fe 8.91 8 .78 B.55 7.67 5 .89 5 .10 8 .57 8 .66 14.32 12.57 5 .35 Mn 23.90 23 .55 23.41 24.87 27 .47 27.24 20 .24 21 .73 10.74 12.48 32 .26 Mg 1.73 1.64 1.58 1.63 1.60 1.91 1.81 1.55 1.52 2 .17 2 .37 Ca 1.37 1.38 1.44 1.46 1.45 1.49 1.52 1.46 2 .58 2 .13 0 .95 Na 0.94 0 .85 0 .99 1.25 0 .67 0 .93 1.85 2 .88 1.69 1.51 1.76 K 0 .60 0 .73 0 .75 0 .80 0 .62 0 .86 0 .77 0 .76 0 .59 0.81 1.00 P 0 .19 0. 18 0 .17 0 .16 0 .13 0 .14 0 .18 0 .18 0.31 0 . 2 ? 0 .13 Co 0.11 0.11 0 .15 0.14 0 .20 0 .20 0 .08 0 .08 0 .12 0 .20 0 .03 Ni 0 .77 0 .87 0 .96 0.91 1.28 1.11 0 .62 0 .54 0 .19 0. 19 0 .50 Cu 0 .49 0 .48 0 .60 0 .60 0.91 1.03 0 .62 0 .59 0 .02 0.01 0 .33 Zn 0 .09 0 .10 0 .10 0.11 0 .10 0 .17 0 .06 0 .06 0 .03 0 .04 0 .08 Ba 0 .20 0 .19 0 .18 0.18 0 .22 0.21 0 .27 0 .32 0 .10 0 .10 0 .63 TOD/DEL 1.07 1.06 1.00 1.20 1.25 1.29 1.52 1.25 0 .00 0 .65 2 .27 LRB RISE 3 S S TRIPOD TRIPOD NUMBER 28 D - l 74 75 4 D - l 4 D-2 DEPTH <m> 1693 3787 4959 3840 3840 S i 3 .53 18.93 7 .22 6.01 5 .82 T i 0 . 65 0 .43 0 .38 0 .27 0.21 R l 0 .83 5 .13 2 .58 1.85 1.88 Fe 14.54 10.00 6 .20 8.94 7 .67 Mn 16.38 4 .67 23 .99 21 .27 23 .14 Mg 1.06 1.41 2 . 2 ? 1.58 1.66 Ca 1.84 0 .90 1.20 1.36 1.47 Na 1.61 2 .72 1.63 1.55 2 .09 K 0 .39 2 .97 1.17 0.84 0 .96 P 0.41 0 .18 0 .12 0 .19 0 .16 Co 0.51 0 .10 0 .26 0.11 0 .12 Ni 0 .33 0 .20 0 .99 0 .82 0.84 Cu 0 .00 0 .08 0 .63 0 .53 0.51 Zn 0 .04 0 .02 0 .08 0 .09 0 .12 Ba 0. 14 0 .14 0 .25 0.18 0.21 TOD/DEL 0 .10 0 .03 1.41 1.06 1.16 CHAPTER 2 DEVELOPMENT OF A SELECTIVE SEQUENTIAL EXTRACTION SCHEME AND A DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE TO DETERMINE THE CHEMICAL PARTITIONING OF Mn, Fe, Cu, Ni, AND Co BETWEEN THE MANGANESE AND IRON OXIDE PHASE MINERALOGY IN FERROMANGANESE CRUSTS AND NODULES 2.1 INTRODUCTION 202 2.1.1 REVIEW OF PEVIOUS WORK 2.1.1.1 Selective Dissolution of Manganese and Iron Oxides in Soils and Sediments Several reagents have been employed over the past several years for the selected removal of Fe or Mn oxides in soils and sediments, the most widely used being sodium dithionite. Deb (1949) found this reagent to be superior to several others in terms of the efficient removal of Fe oxides and less destructive effects on clay minerals. Different versions of the sodium-dithionite method have been published since then (Aguilera & Jackson, 1953; Mitchell & Mackenzie, 1954; Mehra & Jackson, 1960; Kilmer, 1960; Coffin, 1963; Holmgren, 1967). The major variations involved in this reduction step are: (1) pH and temperature of the reaction medium, (2) presence of chelating and buffering agents, (3) single or multiple treatments, (4) length of reaction, and (5) the form (solution vs. solid) and amounts of sodium-dithionite added. Another variation employs sodium dithionite for the reduction, sodium bicarbonate as a buffer, and sodium citrate as a chelating agent for ferrous and ferric iron. The citrate-dithionite-bicarbonate (CDB) method was developed by Mehra & Jackson (1960) and Coffin (1963). Acid ammonium oxalate (Tamm's reagent) is another reagent that has been widely used in soil studies. Le Riche & Weir (1963) and de Endredy (1963) used ammonium oxalate for the extraction of free iron oxides in soils under ultraviolet irradiation. They found that both hematite and goethite were dissolved. The same procedure was carried out in darkness by McKeague & Day (1966) and by 203 McKeague et al. (1971). They found that the oxalate extraction dissolved much of the Fe from the amorphous oxides and very little from the crystalline oxides. Potassium or sodium pyrophosphate has been suggested for the extraction of organically-complexed Fe (Aleksandrova,1960; Bascomb, 1968). McKeague (1967) and McKeague et al. (1971) showed that sodium pyrophosphate is reasonably specific for the removal of organically-complexed Fe. Oxalic acid has been used as an extractant in studies of soil weathering (Alminas & Mosier, 1976), and for studies of the classification and interpretation of the course of podsolization in soils (Ball & Beaumont, 1972). Gallagher & Walsh (1943) used boiling oxalic acid to dissolve weathering products for characterizing different soils. On the basis of the differential response of Mn oxides and Fe oxides to chemical reduction and solution in an acid medium, Chao (1972) developed a method for the selective dissolution of Mn oxides from soils and sediments using acidified hydroxylamine hydrochloride. He found that the hydroxylamine solution was effective in dissolving Mn oxide minerals but did not dissolve Fe oxides. 2.1.1.2 Selective Sequential Extraction Schemes for Soils and Sediments Selective chemical extraction schemes are widely employed to obtain information about the "solid speciation" of metals in soils, sediments, and other natural particulate phases (Salomons & Forstner, 1983). In a sequential extraction scheme, each successive chemical treatment is more drastic than the previous one (Chao & Theobald, 1976). Several selective sequential extraction schemes have been proposed over the last several years. An example of some of these sequential extraction schemes can be found in Chao & Theobald (1976), Hoffman & Fletcher 204 (1979), Tipping et al. (1985). All of the extraction schemes have used chemical reduction as the initial step for removing Mn and Fe oxides (Oades, 1963). Most of the proposed schemes have used hydroxylamine hydrochloride in nitric acid to remove the Mn oxides and ammonium oxalate in oxalic acid to remove the Fe oxides. 2.1.1.3 Selective Dissolution of Manganese and Iron Oxides in Crusts and Nodules Selective dissolution studies of Mn and Fe oxides in marine ferromanganese crusts and nodules has not been as intense as for soils and sediments. The first attempts at the selective dissolution of Mn oxides in nodules were by Buser & Griitter (1956) and by Arrhenius & Korkish (1959). They showed that nodules contain a reduceable fraction of Mn oxides which can be separated by using a solution of hydroxalymine hydrochloride. Arrhenius (1963) then investigated selective dissolution in nodules by using hydrochloric acid and hydroxylamine hydrochloride. Chester & Hughes (1967) later confirmed the findings of Buser & Griitter (1956) and Arrhenius & Korkish (1959), and found that a combined acid-reducing solution of hydroxalymine hydrochloride in acetic acid will effectively dissolve almost all the iron and manganese oxide phases from nodules. During the 1970's, interest in the selective extraction of Mn and Fe oxides in nodules was directed towards extractive metallurgy. Nodules are an oxidized ferromanganese matrix containing about 3% combined content of the highly valued metals cobalt, copper, and nickel. These metals are disseminated throughout the oxide phases as well as being a part of the matrix minerals. The valued metals are therefore not present in nodules as discrete minerals and cannot be concentrated by conventional methods. Most of the extractive metallurgical processes are based upon destruction of the manganese oxide crystal lattice to liberate the contained 205 metals, usually by chemical reduction. Such hydrometallurgical processes can be classified according to those that solubilize the manganese, such as a hydrochloric acid leach or a sulphuric acid leach, and those that specifically dissolve only the highly valued metals, such as an ammonia leach process (Hubred, 1980). The principal hydrometallurgical processes have evolved from the work of companies grouped together in four major consortia and they have been reviewed by Hubred (1980). The process used by Kennecott is a reductive ammonia leach. An ammonia leach is well suited to manganese nodules because the Co, Cu, and Ni all form soluble amine complexes with ammonia; but the iron, manganese, silica, and carbonates are nearly insoluble during the overall reaction. Manganese is reacted with carbon monoxide and precipitated as manganese carbonate: M n 0 2 + CO -» M n C 0 3 Iron is not attacked, but Cu, Ni, and Co released during the matrix attack are solubilized by ammonia. The process is called the Curion process, because cuprous ion is a "catalyst" necessary for the reduction of the manganese: M n 0 2 + 2 C u ( N H 3 ) 2 + + 2NH 3 + (NH4) 2 C0 3 M n C 0 2 + 2 C u ( N H 3 ) 4 2 + + 20H" 2 C u ( N H 3 ) 4 2 + + CO + 20H 2 C u ( N H 3 ) 2 + + 2NH 3 + ( N H 4 ) 2 C 0 3 Nickel, copper, and cobalt are then recovered by fluid ion exchange. The metals are coextracted and then selectively stripped. 206 The Ocean Mining Associates have developed an acid-chloride leaching process, which is characterized by total dissolution of the manganese oxides. Manganese is reduced with hydrochloric acid: M n 0 2 + 4HC1 -» M n C l 2 + C l 2 + 2 H 2 0 All the other metals are solubilized as chloride complexes. Chlorine gas is generated as a by-product. Iron is removed from solution by anion exchange solvent extraction and copper by cation exchange. Increasing the pH allows for the removal of nickel and cobalt as hydroxides. In the late 1970's and into the 1980's, the exploitive use of selective dissolution of Mn and Fe oxides from crusts and nodules diminished. Arrhenius et al., (1979), Bowser et al. (1979), Takematsu (1979), and Blery-Oustriere (1980), using a variety of chemical leaches have all examined the selective dissolution of Mn, Fe and associated metals from manganese nodules. These studies, however, were all carried out on a very limited number of deep-sea nodules. Several studies still explored extractive metallurgy. The use of a sulphuric acid leaching procedure under moderate conditions was proposed by Itoh et al. (1980) in the metallurgical processing of nodules by Japan, while Han & Fuerstenau (1980) examined a sulphur dioxide leaching procedure. The sulphuric acid leaching procedure was found to be the most effective and economical procedure for the extraction of Cu, Ni and Co from nodules without dissolving any Mn or Fe oxides. The sulphur dioxide leaching procedure, however, was found to be just as effective as hydroxalymine hydrochloride. Sulphur dioxide quickly attacks the Mn oxides and releases the metals: M n 0 2 + S 0 2 — M n S 0 4 207 Moorby & Cronan (1981) used several selective leaching procedures to extract the principal chemical phases from nodules. They proposed the following leaching procedure. An acidic acid leach which dissolves any calcium carbonate present and will attack absorbed ions. An hydroxylamine-hydrochloride in acidic acid leach dissolves the reducible Mn and Fe oxides and oxyhydroxides. Finally an hydrochloric acid leach which dissolves the iron oxyhydroxides which are not soluble in the hydroxalymine-hydrochloride. By using these progressively more vigorous chemical attacks, the principal phases of the nodules were selectively removed in sequential order (Moorby & Cronan, 1981). Although they proposed this selective sequential extraction scheme, each step of the leaching procedure was preformed on a new sample instead of sequentially removing each principal chemical phase from the same sample. This procedure can not be truely considered a selective sequential extraction scheme aimed at specifically removing the Mn oxyhydroxides first then removing the Fe oxyhydroxides from a crust or nodule. Extractive metallurgy of crusts was first attemped by Haynes et al. (1987). They examined two hydrometallurgical processes. The first process is called the Cuprion Ammoniacal Leach Process involves a low-temperature hydrometallurgical reduction of manganese IV to manganese II by an aqueous ammonia solution containing an excess of cuprous ions. The metals are solubilized from the reduced crusts with a strong aqueous solution of ammonia and carbon dioxide at low temperature and pressure. The metal-bearing solution is treated to remove copper, followed by nickel recovery using liquid ion exchange methods. The cobalt can then be recovered by selective precipitation with hydrogen sufide, pressure leached with sulphuric acid, and selective reduction with hydrogen to precipitate cobalt as a powder. The second process is called the High-Temperature and High-Pressure Sulphuric Acid Leach Process involves a sulphuric acid leaching of the crusts under 208 high temperature and pressure. Copper, nickel, and cobalt are dissolved while manganese and iron are not solubilized. After cooling, the metal-bearing sulfuric solution is treated similarly to the ammoniacal solution. Murad & Schwertmann (1988) first attempted to identify the Fe oxide mineralogy of some deep-sea crusts by using a selective sequential extraction scheme. They selectively dissolved the Mn oxides using ammonium oxalate in the dark (Schwertmann, 1964). This method is widely used in soils studies and dissolves all M n 4 + oxides, but only the poorly crystalline F e 3 + oxides such as feroxyhite and ferrihydrite. To concentrate the iron oxides, the samples were then treated to eight successive treatments with hydroxylamine hydrochloride. This treatment reduces the M n 4 + oxides and not the F e 3 + oxides. They concluded that the extraction of Mn oxides from the crusts using hydroxylamine-hydrochloride treatment causes the iron oxide mineralogy to change and recommended that this reagent not be used for the selective enrichment of iron oxides in deep-sea crusts. Acharya et al. (1989) studied the ammonia leaching of ocean nodules using various reductants. The leaching of nodules with ammonia has several advantages. These are the non-dissolution of iron, and aluminosilicate and the selective dissolution of Cu, Ni, and Co. For the effective and rapid dissolution of Cu, Ni, and Co from Mn oxides, the presence of of a reductant is necessary. The various reductants used by these authors include FeSO^, MnSO^, H2SO3, FeS, and glucose. They concluded that most of the Cu, Ni, and Co could be leached using FeSO^ MnSC^, (NH^SO^, and FeS as reductants. The complete chemical equations for the reductant processes can be found in Acharya et al. (1989). 2.1.1.4 Differential X-Ray Diffraction As in the case of ferromanganese crusts and nodules, the identification and quantitative determination of Fe oxides in soils by routine X-ray diffraction (XRD) procedures is often difficult or impossible. The reasons are similar to those plaguing the identification of Fe oxides in crusts and nodules: (1) the Fe oxides often make up only a small percentage of the sample and/or (2) as in the case of ferrihydrite, the Fe oxide peaks are so broad that they are difficult to recognize when peaks due to other mineral components area also present (Schulze, 1981). Schulze (1981) first described a method for identifying the Fe phase mineralogy in soils. An XRD pattern of a sample containing Fe oxides can be considered as being made up of two components: (1) the pattern of the Fe oxide minerals and (2) the pattern of the other minerals present. If an X-ray pattern of a sample is obtained before any treatment and a second pattern is obtained for the sample after selective dissolution of all or part of the Fe oxides, this second pattern should be identical to the first, except that the peaks due to the components dissolved by the selective dissolution procedure will be absent. Subtraction of this pattern from the pattern of the untreated sample should therefore yield the pattern of the Fe oxides. This pattern is reffered to as a differential X-ray diffraction pattern (DXRD). In some cases, this simple subtraction of the two patterns may be all that is necessary, but normally an additional step is needed. Because of the removal of the Fe oxides, the remaining minerals are concentrated, and the mass adsorption coefficient of the sample may be changed. The result is that the XRD pattern from the treated sample generally has a greater overall intensity that that of the untreated sample. However, relative intensities within the two patterns should remain essentially the same. To subtract the two patterns from one another, the peaks common to both must have the same height or 2 1 0 intensity. To accomplish this, all of the points in the pattern from the treated sample must be multiplied by a factor that is less than unity, i.e., a scale factor. Subtraction of this scaled pattern from the pattern of the untreated sample then produces the correct differential diagram. The technique can be described as differential X-ray diffraction (DXRD) because the Fe oxide pattern obtained is the difference between the two X R D patterns. This can be expressed mathematically as: where A}, Bj-, and Cf- are the number of counts at angle / in the untreated, treated, and subtracted spectra, respectively, and k is the scale factor. In the method described by Schulze (1981), a scale factor is determined by trial and error. This approach relies on the assumption that the intensities of the silicate peaks are not affected by the selective dissolution treatment. Bryant et al. (1983) solved this problem by incorporating an internal standard, into the sample which is not affected by the dissolution treatment and therefore allows for an objective calculation of the scale factor k. The internal standard can also be used to correct for errors in alignment or sample positioning in the X-ray beam, so that the positions of Fe oxide peaks may be more accurately determined. Bryant et al. (1983) selected an internal standard using the following criteria: (1) the shape and intensity of the diffraction peaks from the internal standard should not be affected by the dissolution treatment; (2) the material should have diffraction peaks within the range of spacings diagnostic for the iron minerals being studied; and (3) diffraction peaks from the internal standard should not overlap the broad diffraction peaks of the iron oxide minerals. Based on these criteria, they selected a-alumina as an internal standard. Since then DXRD has been used extensive in the study of Fe oxides in soils and sediments. Examples can be found in Cambell & Schwertmann (1984) and Brown & Wood (1985). The examination of Fe oxides in a lake environment was conducted by Schwertmann et al. (1987). To date the use of DXRD has not been attempted on marine crusts and nodules 2.1.2 STATEMENT OF PROBLEM Although there exists numerous methods to extract Mn, Fe, Cu, Ni, and Co from crusts and nodules, all of the above mentioned methods are not selective sequential extraction schemes. Some of these methods may be economic for processing crusts and nodules to extract valuable metals; however, they do not take into consideration the relationship between these metals and the specific mineral phase in which they reside; while other methods do attempt to determine the principal chemical phases. A selective sequential extraction scheme must therefore be devised so as to discover which Mn and Fe oxide mineral phases are hosting the economically important metals Cu, Ni, and Co. In developing a selective sequential extraction scheme, two goals had to be attained. These goals are: (1) since crust and nodule samples are finite in size and numerous different analyses are to be preformed on a single sample, a selective sequential extraction scheme should be developed which uses as small amount of sample as feasable; and (2) develop a selective sequential extraction scheme which is as time efficient as possible. Borrowing the methods used in the study of Mn and Fe oxides in the soils, a selective sequential extraction scheme was developed to determine the partitioning between Mn, Fe, Cu, Ni, and Co. The application of DXRD in conjuction with the selective sequential extraction scheme allowed determination of the Mn and Fe oxide mineral phases 212 which are responsible for hosting Cu, Ni, and Co. In developing the D X R D procedure two other goals had to be attained. These are: (1) use as small amount of leached sample as possible, and (2) prepare the sample for X R D analysis so that it is recoverable. 2.2 ANALYTICAL METHODS AND RESULTS 2.2.1 EFFECTIVENESS OF SELECTED REAGENTS 2.2.1.1 Reagents Used A total of five reagents were tested to determine their effectivness in the selective removal of Mn or Fe oxides in a laboratory standard ferromanganese crust. The following reagents were selected based in their reported ability to quickly and effectively remove Mn and Fe oxides: (1) 0.25M NH 2 OH-HCl in 0.25M HC1 (Chao & Zhou, 1983), (2) 0.25M NH 2 OH-HCl in 0.25M HAc (Chao & Zhou, 1983), (3) 0.10M NH 2 OH-HCl in 0.01M H N O 3 (Chao, & Sanzalone, 1973), (4) 0.175M Ammonium Oxalate in 0.10M Oxalic Acid (de Endredy, 1963; Chao & Zhou, 1983), (5) 1 part H 2 N N H 2 , 6 parts concentrated N H 4 O H , and 3 parts 0.30M Citric Acid in 7N N H 4 O H (Shen & Boyle, 1988). The reagents numbered 1 to 4 are commonly used in soil studies to selectively remove either Mn or Fe oxyhydroxides from soil samples. Reagent number 5 is used in the reductive cleaning of corals to remove any oxide coatings. None of these 213 reagents has ever been used to selectively dissolve the Mn or Fe oxyhydroxides in crusts and nodules. A modification of reagent number 2 has been used by Chester & Hughes (1967) to remove almost all of the Mn and Fe oxides from nodules. 2.2.1.2 Experimental Conditions Each reagent was tested on a ferromanganese crust lab standard (DODO 14DZ). A crust was used to determine the effectiveness of each reagent since it contains high concentrations of both Mn and Fe as compared to a ferromanganese nodule. The composition of the crust lab standard is known quite accurately since it was used to determine the precision of the XRF (Table 2-1). With the choice of so many reagents to use in the selective removal of Mn and Fe oxides, a series of experiments were developed to determine: (1) which reagents would be best suited for the selective removal of Mn and Fe oxides, and (2) what are the optimum conditions (i.e. sample to solution ratio and the duration of leaching) for the selected reagents to remove most or all of the targeted oxyhydroxide phases. To meet the above conditions, five samples of the laboratory standard crust were leached at consecutive times of V2, 1, 2, 4, and 8 hours at a fixed sample to solution ratio. This experiment was then repeated for a different sample to solution ratio. The sample to solution ratios chosen for these experiments were 1:250, 2:250, 3:250, 4:250, and 5:250. Bearing in mind the first goal of developing a selective sequential extraction scheme, a sample to solution ratio of 5:250 used lg of crust leached in 50mL of reagent. For a sample to solution ratio of 1:250, 0.2g of crust was leached in 50mL of reagent. The whole procedure was repeated for each of the different reagents. The sample and reagent were measured into a 125mL Erlenmeyer flask and were allowed to equilibrate for the fixed times on an orbital shaker set at 85rpm. Table 2-1. The mean composition of the laboratory standard crust DODO 14DZ. Mean concentrations are given as weight per cents. Element Replicate 1 2 Si 9.46 6.24 Ti 1.13 1.17 Al 1.77 1.92 Fe 15.23 15.91 Mn 12.27 13.08 Ca 0.95 1.00 Na 1.55 1.72 K 0.76 0.76 P 0.65 0.68 Co 0.30 0.30 Ni 0.15 0.15 Cu 0.06 0.07 Zn 0.03 0.03 Ba 0.13 0.13 3 4 5 6.10 5.22 5.25 1.17 1.17 1.15 1.84 1.86 1.83 15.47 15.66 15.49 12.47 12.60 12.22 1.06 1.02 0.96 1.36 1.65 1.54 0.76 0.73 0.74 0.67 0.68 0.65 0.30 0.30 0.30 0.15 0.15 0.16 0.05 0.06 0.04 0.04 0.04 0.04 0.12 0.13 0.13 Mean S .D. CV. (%) 6.45 1 .75 27.13 1.16 0 .02 1.72 1.84 0 .05 2.72 15.55 0 .25 1.61 12.53 0 .34 2.71 1.00 0 .05 5.00 1.56 0 .14 8.97 0.75 0 .01 1.33 0.67 0 .02 2.99 0.30 0 .00 0.00 0.15 0 .00 0.00 0.06 0 .01 16.67 0.04 0 .01 25.00 0.13 0 .00 0.00 215 The solution was then transferee! to a 50mL centrifuge tube and centrifuged for 20min at 3000rpm. The leachate was decanted into a lOOmL volumetric flask. The residue was washed three times with reagent and centrifuged again for 20min. The wash solutions were combined with the leachate in the lOOmL volumetric flask. The leachate was then made up to volume with further reagent and stored in an acid washed 125mL Nalgene® polyethylene bottles until it could be analysed for Mn, Fe, Cu, Ni, and Co. The residue was then washed and centrifuged three times with distilled deionized water and freeze dried. Although only five reagents were selected to determine their effectiveness in the selective removal of Mn or Fe oxides, a total of six experiments using the reagents mentioned in the previous section were conducted. Two experiments were preformed using 0.175M Ammonium Oxalate in 0.10M Oxalic Acid (Tamm's Reagent). The first experiment using Tamm's reagent used a modification of the method described by McKeague & Day (1966) and by Chao & Zhou (1983). The same experimental procedure was followed as for all other reagents, except that the reagent and the sample were allowed to equilibrate in the dark. The 125mL Erlenmeyer flasks were wrapped with black electrician's tape and the oribital shaker was also covered with a black plastic sheet to ensure that no light would reach the samples. The samples were processed as before. The second experiment used a modification of the photolytic method described be de Endredy (1963). A total of five samples each consisting of the laboratory standard crust and Tamm's reagent at one of the sample to solution ratios were measured into 125mL Erlenmeyer flasks. These were then placed at the base of a 450W, medium pressure Hanovia lamp on a heater/stirring plate and agitated for one hour with magnetic stirring beans. After one hour the samples were removed from the base of the Hanovia lamp and processed as before. 216 2.2.2 ANALYSIS OF LEACHATES The concentrations of Mn, Fe, Cu, Ni, and Co in the leachates were determined by atomic adsorption spectometry using a Perkin-Elmer 560® spectrometer with a four inch one slot burner head, lean air-acetylene flame, and single-element hollow cathode lamps. The instrument was operated under the conditions shown in Table 2-2. 2.2.2.1 Calibration A series of five standards were used in the calibration of the atomic absorbtion spectrometer. Each standard was pepared by pipetting carefully measured amounts of Baker Analyzed Reagent® (lOOOppm) Mn, Fe, Cu, Ni, and Co into a 50mL volumetric flask in a laminar flow hood using a digital Eppendorf® pipette. The elements were then diluted by making up to volume with the appropriate leaching reagent. A series of standards consisted of Oppm, 2.5ppm, 5ppm, 7ppm, and lOppm of each of the above elements. Since five different reagents were used in the selective extraction experiments, five sets of standards were prepared. Calibration curves for the elements Mn, Fe, Cu, Ni, and Co are shown in Figure 2-1. All calibration curves are linear over the concentration ranges used. 2.2.2.2 Sample Preparation By measuring the absorbance of Mn, Fe, Cu, Ni, and Co in the leachates, the concentrations of these elements were found to exceed the range of concentrations of those in the standards. The leachate samples, therefore, had to be diluted so that the measured absorbance values of the elements of interest can be plotted onto the Table 2-2. Instrumental setting for analysis of the five metals on the atomic absorption spectrophotometer. Element Wavelenth Lamp Current S l i t A i r Flow Fuel Flow (nm) (mA) (nm) (L/min) (L/min) Mn 279.5 15 0.2 19.5 0.6 Fe 248.3 15 0.2 19.5 0.6 Cu 324.8 7 0.2 19.5 0.6 Ni 232.0 15 0.2 19.5 0.6 Co 240.7 15 0.2 19.5 0.6 218 Figure 2-1. Calibration curves of the elements Mn, Fe, Cu, Ni, and Co in various reagents. The open circles = Mn, the filled circles = Fe, the open triangles = Cu, the filled triangles = Ni, the open squares = Co. 219 0 .25M NH 2 OH-HCI in 0 . 2 5 M HCI o 0 . 9 0 0 - 1 o 0 2 4 6 8 10 C o n c e n t r a t i o n (ppm) of Mn, Fe , C u , N i , and Co 0 .25M N H 2 0 H - H C I in 0 . 2 5 M HAc o 0 . 9 0 0 1 C o n c e n t r a t i o n (ppm) of Mn , Fe , C u , N i , a n d C o 220 o 0 . 9 0 0 C O 3 o c o o < o Li-as U c o -O o OT < 0 . 6 0 0 + o 0 . 3 0 0 + 0 . 0 0 0 o 0 . 9 0 0 C 0 . 6 0 0 + o 0 . 3 0 0 + 0 . 0 0 0 0 . 25M NH 2 0H -HC I in 0.01 M HNO3 2 4 6 8 10 Concen t ra t i on (ppm) of Mn, Fe, C u , Ni, and Co 0.1 7 5 M A m m o n i u m Oxalate in 0 .1M Oxal ic Ac id Concen t ra t i on (ppm) of Mn, Fe, C u , N i , and Co 221 1 par t Hydraz ine , 6 par ts concen t ra ted N H ^ O H , and 3 par ts 0 .3M Ci t r ic Ac id 'in 7N NHLOH o 0.900 0 2 4 6 8 10 Concen t ra t i on (ppm) of Mn, Fe, C u , Ni , and Co 222 calibration lines. An aliquot of the leachate was diluted 500 times by measuring 10/xL of leachate and 4.99mL of the same reagent used in the experiment into an acid washed 5mL test tube. The test tube was capped and shaken vigorously to ensure sample homogeneity. The concentration of Mn, Fe, Cu, Ni, and Co in the leachate was then determined by plotting their measured absorbance values onto calibration curves. The resits of these analysis are given in Appendix A. 2.2.2.3 Determining the Effectiveness of Each Reagent The relative effectiveness of each reagent in selectively removing either Mn or Fe and the associated Cu, Ni, and Co from the laboratory standard crust are shown in Appendix B. The results show that none of the reagents tested removed 100% of the manganese or iron present in the crust. This may be due to the fact that some of the iron present in the laboratory standard crust may be associated with the manganese phase mineralogy and present as iron bearing aluminosilicates. Two reagents were found to be most effective in developing a two stage sequential extraction scheme for crusts and nodules. First, using 0.1M NJr^OH-HCl in 0.01M H N O 3 as the leaching reagent, a sample to solution ratio of 3:250, and an extraction time of eight hours, was found to be the most effective in removing almost all of the manganese but only a minor amount of iron in the laboratory standard crust. Second, to selectively remove all of the iron, 0.175M Ammonium Oxalate in 0.1M Oxalic Acid, a sample to solution ratio of 1:250, and an extraction time of eight hours was found to be the most effective, however, this reagent also removed a large portion of the manganese as well. This is of little consequence since almost all of the manganese will have been previously removed in the first stage of the sequential selective extraction scheme. The effectiveness of these two reagents in selectively 223 removing Mn and Fe from the laboratory standard crust are indicated in Table 2-3 by the arrow-head. 2.2.3 D E V E L O P M E N T OF T H E TWO STAGE LEACHING P R O C E D U R E Using the results of the above leaching experiments, a two stage selective sequential extraction scheme was devised and tested on a laboratory standard crust and a nodule. Since both laboratory standards were used to determine the precision of the XRF, the concentrations of Mn, Fe, Cu, Ni, and Co in these laboratory standards is known quite precisely. The composition of the crust lab standard has been listed in Table 2-1 while the composition of the nodule lab standard is listed in Table 2-4. A total of eleven samples were subjected to the two stage selective sequential extraction scheme. Ten samples were replicates of the laboratory standard crust and one sample of the laboratory standard nodule. The ten replicates of the crust were analysed to determine the precision and accuracy of the method of analysis. 2.2.3.1 First Stage of the Selective Sequential Extraction Scheme One gram of sample and 83mL of reagent were sequentially measured into an acid washed 125mL Nalgene® polyethylene bottle and capped. The sample was then placed onto an orbital shaker set at 85rpm and allowed to equilibrate for eight hours, after which the residue and leachate were separated by centrifugation for 20min at 3000rpm. The leachate was decanted into a lOOmL volumetric flask and the residue was washed three times with 0.1M NH 2 OH-HCl in 0.01M H N O 3 and centrifuged Table 2-3. The effectiveness of 0.25M N H 2 O H H C l in 0.01M H N O 3 and 0.175M Ammonium Oxalate in 0.1M Oxalic Acid. Results are listed as the per cent of Mn and Fe removed from the laboratory standard crust DOD014DZ. 0.25M NH 2OH«HCl i n 0.01M HNO3 Sample:Solution = 3:250 Time Mn Fe (hr) (Percent) 0.5 84.60 6.11 1.0 89.04 7.98 2.0 85.24 4.23 4.0 84.73 1.18 • 8.0 99.28 3.54 0.175M Ammonium Oxalate i n 0.1M Oxalic Acid Sample:Solution = 1:250 Time Mn Fe (hr) (Percent) 0.5 84.79 89.17 1.0 80.41 87.40 2.0 78.52 106.29 4.0 73.96 110.50 • 8.0 83.00 104.82 Table 2-4. The mean composition of the laboratory standard nodule Mnl91 6-8. Mean concentrations are given as weight per cents. Element Replicate 1 2 Si 7.07 7.39 Ti 0.35 0.36 Al 2.96 2.85 Fe 5.35 5.36 Mn 28.19 28.07 Mg 3.34 3.18 Ca 1.42 1.41 Na 0.10 0.50 K 0.94 0.92 P 0.21 0.21 Co 0.18 0.17 Ni 1.50 1.40 Cu 1.46 1.34 Zn 0.14 0.12 Ba 0.30 0.29 3 4 5 6 .55 7 .40 7 .57 0 .36 0 .35 0 .35 2 .98 2 .94 2 .95 5 .36 5 .34 5 .37 28 .42 28 .18 28 .42 3 .76 3 .48 3 .91 1 .40 1 .41 1 .41 0 .26 0 .06 0 .12 0 .88 0 .91 0 .89 0 .21 0 .20 0 .21 0 .19 0 .18 0 .18 1 .31 1 .44 1 .48 1 .23 1 .45 1 .45 0 .11 0 .13 0 .13 0 .29 0 .29 0 .29 Mean S. D. CV. (%) 7.20 0. 40 5.55 0.35 0. 00 0.00 2.94 0. 05 1.70 5.36 0. 01 0.19 28.26 0. 16 0.57 3.53 0. 30 8.50 1.41 0. 01 0.71 0.21 0. 18 85.71 0.91 0. 02 2.20 0.21 0. 00 0.00 0.18 0. 01 5.55 1.43 0. 07 4.89 1.37 0. 10 7.30 0.13 0. 01 7.69 0.29 0. 00 0.00 226 a g a i n f o r 2 0 m i n at 3 0 0 0 r p m . E a c h w a s h was c o m b i n e d w i t h t h e l e a c h a t e , m a d e u p t o v o l u m e w i t h 0.1M N H 2 O H - H C l i n 0.01M H N O 3 a n d s t r o r e d i n a n a c i d w a s h e d 1 2 5 m L Nalgene® p o l y e t h y l e n e b o t t l e . T h e r e s i d u e was w a s h e d t h r e e t i m e s w i t h d i s t i l l e d d e i o n i z e d water, c e n t r i f u g e d f o r 2 0 m i n at 3 0 0 0 r p m a n d f r e e z e d r i e d . 2.2.3.2 S e c o n d S t a g e o f t h e S e l e c t i v e S e q u e n t i a l E x t r a c t i o n S c h e m e D e p e n d i n g o n h o w m u c h r e s i d u e r e m a i n e d a f t e r t he f i r s t stage o f t h e e x t r a c t i o n scheme, a n a p p r o p r i a t e a m o u n t o f 0.175M A m m o n i u m O x a l a t e i n 0.1M O x a l i c A c i d was a d d e d t o t h e r e s i d u e i n t he p l a s t i c b o t t l e t o m a i n t a i n a s a m p l e t o s o l u t i o n r a t i o o f 1:250. T h e c a p p e d b o t t l e was t h e n s h a k e n at 8 5 r p m f o r e i g h t h o u r s i n t h e da r k . T h e r e s i d u e was t h e n s e p a r a t e d f r o m the l e a c h a t e u s i n g t h e m e t h o d s d e c r i b e d above. 2.2.3.3 A n a l y s i s o f t h e L e a c h a t e s A n a l y s i s o f t h e l e a c h a t e s f r o m t h e t w o stage s e q u e n t i a l s e l e c t i v e e x t r a c t i o n s c h e m e w e r e a g a i n c a r r i e d o u t as d e s c r i b e d i n s e c t i o n 2.2.2. T h e resu l t s f r o m t h e t w o stage s e l e c t i v e s e q u e n t i a l e x t r a c t i o n s c h e m e a r e g i v e n i n T a b l e 2-5. T a b l e 2-5a li s t s t h e w e i g h t p e r c e n t o f M n , F e , C u , N i , a n d C o r e m o v e d d u r i n g t h e f i r s t stage o f l e a c h i n g . F o r t h e t e n r e p l i c a t e s o f t h e l a b o r a t o r y s t a n d a r d crust, t h e a v e r a g e w e i g h t p e r c e n t o f e a c h e l e m e n t r e m o v e d is given. T h e i n d i v i d u a l r e s u l t s w i l l b e l a t e r e x p l a i n e d t o d e t e r m i n e t h e p r e c i s i o n o f t h e m e t h o d s o f analysis. T a b l e 2-5b li s t s t h e w e i g h t p e r c e n t o f M n , F e , C u , N i , a n d C o r e m o v e d d u r i n g t h e s e c o n d stage o f l e a c h i n g . A g a i n , f o r t h e t e n r e p l i c a t e s o f t h e l a b o r a t o r y s t a n d a r d crust, t h e a v e r a g e w e i g h t p e r c e n t o f e a c h e l e m e n t r e m o v e d is g i v e n . S o m e p a r t i t i o n i n g o f M n , F e , C u , Table 2-5a. Concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the first stage of the two stage selective sequential extraction scheme. Results are given as weight per cents. Sample Element Mn Fe Cu N i Co C r u s t Nodule 12.55 27.50 0.75 0.63 0.02 1.03 0.14 0.87 0.29 0.14 Table 2-5b. Concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the second stage of the two stage selective sequential extraction scheme. Results are given as weight per cents and have been adjusted to be comparable to the first stage of leaching. Sample Element C r u s t Nodule Mn 0.47 0.32 Fe 11.91 2.50 Cu 0.07 0.44 N i 0.07 0.55 Co 0.11 0.15 228 Ni, and Co in the laboratory standard crust and nodule is evident from these results. For both the crust and nodule, the leachates from the first stage of leaching both contain a large concentration of Mn, with only minor amounts of Fe, while the leachates from the second stage of leaching contain a higher concentration of Fe with only minor amounts of Mn. The behaviour of Cu, Ni, and Co in the leachates from the two stages of the extraction scheme are distinctively different for the crust and nodule. For the crust, the leachates from the first stage contain higher concentrations of Ni and Co when compared to the leachates from the second stage, whereas Cu is higher in the second stage leachates. For the the nodule, the leachate from the first stage contains a higher concentration of Cu when compared to the leachate from the second stage. The same is observed for Ni except not to the same extreme. For Co, however, equal amounts of Co are extracted from both the first and second stage of leaching. 2.2.3.4 Precision and Accuracy The precision of the methods involved for determination of Mn, Fe, Cu, Ni, and Co was obtained by analysing ten replicates of the laboratory standard crust DODO 14DZ. Ten sub-samples from a well mixed bulk sample were subjected to the two stage selective sequential extraction scheme and analysed by atomic absorbtion spectrophotometer. The sample precision includes errors due to the inherent inhomogeneity of the samples, sample handling and weighing during the extraction procedures, and preparation of the leachates for analysis. In addition, one of the calibration standards, chosen randomly, was analyzed eight times in order to determine the instrumental precision of the atomic absorption spectrophotometer. The sample precision results are shown in Table 2-6. Table 2-6a lists the mean, standard deviation, and coefficient of variation (CV.) for Mn, Fe, Cu, Ni, and Co Table 2-6a. Precision of the method of analysis for the first stage of the two stage selective sequential extraction scheme. Replicate samples are from the laboratory standard crust DODO 14DZ. Concentrations are given as weight per cents. Replicate Element Mn Fe Cu Ni Co 1-1 12.11 0.62 0.02 0.14 0.30 1-2 12.36 0.69 0.02 0.14 0.27 1-3 12.29 0.69 0.02 0.14 0.28 1-4 12.70 0.67 0.02 0.14 0.30 1-5 12.81 0.77 0.02 0.14 0.29 1-6 12.94 0.80 0.02 0.14 0.29 1-7 12.29 0.79 0.02 0.14 0.30 1-8 12.72 0.80 0.02 0.15 0.30 1-9 12.59 0.81 0.03 0.15 0.29 1-10 12.71 0.82 0.02 0.15 0.30 Mean 12.55 0.75 0.02 0.14 0.29 S.D. 0.27 0.07 0.00 0.00 0.01 C V . (%) 2.15 9.33 0.00 0.00 3.45 Table 2-6b. Precision of the method of analysis for the second stage of the two stage selective sequential extraction scheme. Replicate samples are from the laboratory standard crust DODO 14DZ. Concentrations are given as weight per cents. Replicate Element Mn Fe Cu Ni Co 2-1 0.46 12.00 0.07 0.06 0.11 2-2 0.46 12.10 0.07 0.09 0.10 2-3 0.49 11.40 0.09 0.09 0.11 2-4 0.45 12.00 0.07 0.11 0.10 2-5 0.48 12.20 0.07 0.05 0.17 2-6 0.48 12.00 0.06 0.08 0.12 2-7 0.47 12.40 0.07 0.05 0.09 2-8 0.48 12.40 0.07 0.06 0.10 2-9 0.49 12.70 0.05 0.06 0.10 2-10 0.48 12.90 0.07 0.08 0.07 Mean 0.47 11.91 0.07 0.07 0.11 S.D. 0.01 0.32 0.01 0.02 0.02 C V . (%) 2.12 2.67 14.28 28.57 18.18 230 Table 2-6c. Precision of the Atomic Absorbtion Spectrometer as determined by the absorbances of the standard 5ppm. First Stage of the Two Stage Extraction Scheme Repeat Analysis Element Mn Fe Cu Ni Co 1 0.226 0.206 0.349 0 .172 0. 125 2 0.223 0.204 0.349 0 .167 0. 126 3 0.225 0.206 0.346 0 .170 0. 128 4 0.226 0.209 0.349 0 .169 0. 129 5 0.227 0.202 0.342 0 .168 0. 126 6 0.227 0.203 0.349 0 .170 0. 127 7 0.224 0.204 0.346 0 .168 0. 127 8 0.225 0.203 0.348 0 .170 0. 124 Mean 0.225 0.205 0.347 0 .169 0. 127 S.D. 0.001 0.002 0.002 0 .001 0. 002 CV. (%) 0.44 0.97 0.57 0 .59 1. 57 Second Stage of the Two Stage Extraction Scheme Repeat Analysis Element Mn Fe Cu Ni Co 1 0.255 0.294 0.195 0.067 0.072 2 0.256 0.295 0.190 0.068 0.068 3 0.257 0.299 0.190 0.067 0.069 4 • 0.259 0.298 0.193 0.068 0.071 5 0.258 0.298 0.191 0.067 0.067 6 0.261 0.295 0.194 0.068 0.072 7 0.259 0.297 0.194 0.067 0.073 8 0.259 /0.197 0.067 0.070 Mean 0.258 0.297 0.193 0.067 0.070 S.D. 0.002 0.002 0.002 0.000 0.002 CV. (%) 0.78 0.67 1.04 0.00 2.86 231 from the first stage of the two stage selective sequential extraction scheme. The sample precision for the first stage of leaching was found to vary from 0.00% (Cu and Ni) up to 9.33% (Fe) (C.V.). Table 2-6b lists the mean, standard deviation, and C V . for Mn, Fe, Cu, Ni, and Co from the second stage of the two stage selective sequential extraction scheme. The sample precision for the second stage of leaching was found to vary from 2.12 (Mn) up to 28.57% (Ni) (C.V.). In most cases the C V . for the second stage of leaching was found to be greater than for the first stage of leaching. Table 2-6c lists the instrumental precision when using each reagent to prepare the standards used to determine the concentrations of Mn, Fe, Cu, Ni, and Co in the leachates. When using 0.1M N H 2 O H H C l in 0.01M H N 0 3 to prepare the standards for the atomic absorbtion spectrometer, the instrumental precision was found to vary between 0.44 (Mn) and 1.57% (Co) (C.V.). When using 0.175M Ammonium Oxalate in 0.1M Oxalic Acid to prepare the standards for the atomic absorbtion spectrometer, the instrumental precision was found to vary between 0.00 (Ni) and 2.86% (Co) (C.V.). The C V . for the instrumental precision for both reagents was found to be far smaller than sample precision for both stages of the selective sequential extraction scheme. The accuracy of the methods used to determine the concentrations of Mn, Fe, Cu, Ni, and Co in the leachates was checked by comparing the analytical results of the sum of the two stages of leaching to the known concentrations of these elements in the crust and nodule as determined by XRF (Table 2-7). Table 2-7 shows that the selective extractions remove all of the Mn, Cu, Ni, and Co from both crusts and nodules. The concentration of Fe is lower in the leachates because the XRF results include Fe in the aluminosilicate fraction. 232 Table 2-7. Comparison of the total amount of Mn, Fe, Cu, Ni, and Co removed from the laboratory standard crust and nodule by the two stage selective sequential extraction scheme compared to the XRF results used to determine precision of the XRF. Results are given as weight per cents. Element AA Results XRF Results Crust Nodule Crust Nodule Mn 13.02 27.82 12.53 28.26 Fe 12.66 3.13 15.55 5.36 Cu 0.09 1.47 0.06 1.37 Ni 0.21 1.42 0.15 1.43 Co 0.40 0.29 0.30 0.18 233 2.2.4 D E V E L O P M E N T OF DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE The development of the DXRD procedure for the identification of manganese and iron oxyhydroxides in crusts and nodules was carried out in conjunction with the development of the two stage selective sequential extraction scheme. The same laboratory standard crust and nodule samples used in the two stage selective sequential extraction scheme were also used in the development of D X R D procedure. The development of the D X R D procedure was a simple process of modifying the existing XRD equipment to suit the specific needs required to produce a DXRD diffractogram. 2.2.4.1 Sample Preparation As already pointed out, two goals had to be obtained during sample preparation for DXRD. These are: (1) to use as small amount of residue as possible, and (2) to prepare the sample for DXRD analysis so that it is recoverable. A small amount of residue was ground in a mortar and pestle and placed onto the centre of a ground quartz glass disc. The sample was then suspended with distilled deionized water mixed into a slurry with a clean stainless steel spatula and dried in a laminar flow hood. The ground quartz glass disc contributes less background noise to the X R D pattern as compared to a conventional glass disc. Suspension of the sample with distilled deionized water allows the sample to settle in a random orientation. The samples are dried in a laminar flow hood to prevent sample contamination; allow the sample to dry slowly; and to prevent desiccation cracks which result from the sample drying too quickly. The quartz glass disc and the dried sample was then placed into an aluminium XRD sample holder. 234 After analysis the sample is scraped off the quartz glass disc with a clean stainless steel spatula and mixed with the rest of the residue. The quartz glass disc is then cleaned in an ultra-sonic bath for five minutes, rinsed with isopropyl alcohol and allowed to dry. 2.2.4.2 Experimental Conditions The prepared samples were loaded into a Philips® PW 1775 sample changer to be analyzed by a Philips X-ray diffractometer powered by a Philips® PW 1729 constant potential generator. Diffraction data were obtained using Cu Ka radiation (40kV, 20mA) and a Philips® PW 1050/70 vertical goniometer equipped with a diffracted beam graphite monochromator, an automated divergence slit, 0.1mm receiving slit, 1° scatter slit, and a gas proportional counter. Although identification of low intensity peaks is made difficult by the high background due to the fluorescent Mn and Fe radiation, Glasby (1972) found that an iron tube was only slightly superior to the copper tube. Work was therefore completed using a copper tube. The diffractometor was controlled by a Philips® PW 1710/00 diffraction control unit. Measurement and control parameters were set up in the PW 1710/00 microprocessor through a Zenith® Z-150 personal computer using MS-DOS Kermit version 2.31 (Gianone et al., 1988). The laboratory standard crust and nodule samples were step scanned from 5° to 71°20 in O.O1°20 increments, using a counting time of one second per increment. The number of counts measured at each O.O1°20 were therefore a measure of the intensity (counts/second) at each O.O1°20 increment. Instead of sending the intensity along with the degrees 20 to the ratemeter to produce a diffractogram, they were sent to the computer and stored in an ASCII file to be later processed. Thus, an 235 analog X R D diffractogram has been digitized which allows for the data to be further manipulated and used to produce a DXRD diffractogram by computer. 2.2.4.3 Production of a DXRD Diffractogram 2.2.4.3.1 Smoothing the Data Superimposed upon and indistinguishable from the digitized X R D spectrum are random errors which regardless of their source, are characteristically described as noise. Before the digitized XRD spectrum can be plotted or used to produce a D X R D tracing, as much of the noise must be removed as possible without, at the same time, unduly degrading the underlying information (Savitzky & Golay, 1964). Following the computational methods described by Savitzky & Golay (1964), the removal of random noise from the XRD spectra involved the convolution methods of a moving average and that of least squares. Savitzky & Golay (1964) wrote two computer programs, in FORTRAN, to perform the removal of random noise from a digitized spectra using the two convolution methods described above. These two subroutines have been combined into one program and translated into GW BASIC (Appendix C). The digitized XRD spectra stored in an ASCII file was subjected to a 17 point smoothing using this modified program. The new XRD spectra, devoid of excess noise, was stored in a new ASCII file and could now be plotted, by computer, to produce an XRD diffractogram or used to produce a DXRD diffractogram. 2.2.4.3.2 Equation of DXRD Pattern As previously discussed in greater detail, if an X-ray pattern of a sample is obtained before and after selective dissolution of all or part of the targeted mineral phases, the pattern obtained after selective dissolution should be identical to the one before, except that the peaks due to the components dissolved by the selective dissolution procedure will be absent. Subtraction of the treated pattern from the pattern of the untreated sample should therefore yield the pattern of the removed mineral phases. Because of the removal of the targeted mineral phases, the remaining minerals are concentrated, and the mass adsorption coefficient of the sample may be changed. The result is that the XRD pattern from the treated sample generally has a greater overall intensity than that of the untreated sample. However, relative intensities within the two patterns should remain essentially the same. To subtract the two patterns from one another, the peaks common to both must have the same height or intensity. To accomplish this, all of the points in the pattern from the treated sample must be multiplied by a scale factor. Subtration of this scaled pattern from the pattern of the untreated sample then produces the D X R D diffractogram. The most effective way of determining the scale factor is by using an internal standard as proposed by Bryant et al. (1983). The internal standard can also be used to correct for errors in alignment or sample positioning in the X-ray beam, so that the positions of the peaks of the removed mineral phases may be more accurately determined. Since almost all crusts and nodules contain quartz, it is appropriate to use this mineral as an internal standard to determine the scale factor needed to subtract the treated X R D pattern from the untreated XRD pattern. The 3.34A quartz peak is almost always present and can be easily identified in X R D patterns of crusts and nodules. This quartz peak meets the criteria for use as an internal standard as put forward by Bryant et al. (1983): (1) the shape and intensity of the 3.34A diffraction peak is not affected by the dissolution treatments; (2) the 3.34A peak is within the range of d-spacings diagnostic for the manganese and iron minerals being studied; and (3) the 3.34A diffraction peak for quartz does not overlap the broad diffraction peaks of the manganese and iron oxide minerals. The 3.34A quartz peak was selected as the internal standard instead of the 3.18A feldspar peak because feldspar is a group of minerals consisting of two solid solution series. The positive identification of a feldspar requires a knowledge not only of the chemical composition but also the structural state of the species (Hurlbut & Klein, 1977). Since several species of feldspar are present in crusts and nodules, the 3.18A feldspar peak is broader and consists of a combination of several peaks due to the presence several species of feldspars. Quartz, on the other hand, has a constant composition with no solid solution effects; moreover the 3.34A peak is narrower than the 3.18A peak and consists of only one peak. This makes the 3.34A quartz peak ideal for use an an internal standard. Bryant et al. (1983) noted that their procedure for the selective dissolution of iron oxides in soils would also attack the silicates. They proposed that instead of using the silicates present in their samples as an internal standard, one should be added to the sample which is resistant to chemical attack. The same considerations were applied to the DXRD diffractograms of the laboratory standard crust and nodule produced during the two stage selective sequential extraction scheme. The quartz present in crusts and nodules is an adequate internal standard since the methods used in the two stage selective sequential extraction scheme are not as distructive as those of Bryant et al. (1983). Quartz is composed essentially of Si02 and is therefore electrically neutral. Furthermore, low quartz, the most common polymorph of Si02 found at the earth's surface, has the most compact structure of all the polymorphs of Si02- This is indicated by its low amount of crystal symmetry 2 3 8 (Hurlbut & Klein, 1977). This makes quartz essentially unreactive and immune to chemical attack during the leaching procedures of the two stage selective sequential extraction scheme. To determine the value of the scale factor k, it must be remembered that the goal of subtracting the treated from the untreated XRD pattern is to remove the presence of the aluminosilicates and any other mineral phases not affected by the chemical dissolution. This goal is simple to acheive with the use of the 3.34A quartz peak used as an internal standard and a simple modification of the equation of the D X R D pattern. To remove the presence of the aluminosilicates the following situation must exist. ArkBt = 0 It is now a simple procedure of dividing the intensity of the 3.34A quartz peak from the untreated XRD pattern by the 3.34A quartz peak from the treated XRD pattern. = * The intensities of the treated XRD pattern (Bj) must now be multiplied by the value of k and subtracted from the intensities of the untreated XRD pattern (A-) to produce the intensities of the DXRD pattern (Cj). This was a simple procedure when both smoothed ASCII files for the untreated and treated XRD patterns are imported into LOTUS 123® and the repetitious calculations are performed by the program. 2.2.4.3.3 Plotting the Tracing The graphs of the untreated, treated, and DXRD diffractograms were initially plotted using LOTUS 123®. These graphs were then imported into LOTUS F R E E L A N C E PLUS® where they were horizontally rotated to fill an entire page in landscape mode. An added advantage of using LOTUS F R E E L A N C E PLUS® was the ability to label the identified peaks on the pattern before being printed. It is also worth noting that even though the data needed to produce the D X R D pattern are subjected to several computer manipulations and printed on a laser printer, the d-spacings of the DXRD pattern are not distorted. 2.2.4.4 Description of the DXRD Results Figures 2-2 and 2-3 show the XRD diffraction patterns of the laboratory standard crust and nodule, respectively, before being subjected to the two stage selective sequential extraction scheme. The predominant mineralogy of the untreated crust is 5Mn02 with minor quartz and feldspar. The predominant mineralogy of the untreated nodule is todorokite and possibly some S M n 0 2 together with quartz and feldspar. Figures 2-4 and 2-5 show the X R D diffraction patterns of the crust and nodule after the first stage of the sequential extraction scheme. For the crust, there does not appear to be a significant change between the two diffraction patterns Figures 2-2 and 2-4. However, the difference between these two patterns becomes apparent when examining the DXRD pattern from these two X R D diffractograms (Figure 2-6), which shows that the manganese oxide mineral removed during the first stage of leaching is 5Mn02. Like the crust, there also does not appear to be a significant change in the XRD diffractograms after the first stage of leaching on the nodule. Again, the difference between Figures 2-3 and 2-5 become Figure 2-2. The XRD diffraction pattern of the laboratory standard crust DODO 14 DZ. DEGREES 20 242 Figure 2-3. The XRD diffraction pattern of the laboratory standard nodule Mn 191 6-8. 100 DEGREES 20 244 Figure 2-4. The XRD diffraction pattern of the laboratory standard crust DODO 14 D Z after the first stage of the sequential extraction scheme. INTENSITY (COUNTS/SECOND) o o (0 Tj" 246 Figure 2-5. The XRD diffraction pattern of the laboratory standard nodule Mn 191 6-8 after the first stage of the sequential extraction scheme. 100 2 4 8 Figure 2-6. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the laboratory standard crust DODO 14 DZ. D E G R E E S 20 2 5 0 apparent in the D X R D pattern from these two X R D patterns (Figure 2-7), which shows that the manganese oxide mineral removed during the first stage of leaching is todorokite and SMnO^. Present in both D X R D patterns for the crust and nodule is the 3.18A peak of feldspar. The presence of this peak in both DXRD patterns is due to: (1) feldspar is partially dissolved by the 0.1M N H 2 0 H - H C 1 in 0.01M H N O 3 used in the first stage of the extraction scheme; (2) the 3.18A peak for feldspar is broad due to the fact several feldspars are present in the crust and nodule; therefore, the subrtraction of the scaled treated XRD diffractogram from the untreated XRD diffractogram will not totally remove the presence of this peak; and (3) due to the random orientation of the sample when it is prepared for X-ray diffraction the fortuitous orientation of the mineral crystallites will change the relative intensities of the diffraction peaks from one XRD diffractogram to another. -The XRD diffractograms of the crust and nodule after the second stage of leaching are shown in Figures 2-8 and 2-9, respectively. Subtraction of these XRD diffractograms from the XRD diffractograms obtained after the first stage of leaching will produce the DXRD patterns of the mineral phases removed during the second stage of leaching with 0.175M Ammonium Oxalate in 0.1M Oxalic Acid. The D X R D pattern for the crust shows the broad peaks of the poorly crystalline iron oxide ferrihydrite (Figure 2-10). The D X R D pattern for the nodule shows the broad peaks of another poorly crystalline iron oxide akaganeite (Figure 2-11). Also present in the D X R D pattern of the nodule is two narrow aluminosilicate peaks probably belonging to feldspar. These are present in the D X R D pattern of the nodule for the same reasons as the 3.18A feldspar peak was present in both DXRD patterns of the crust and nodule from the first stage of leaching. Table 2-8 gives a comparison of the d-spacings of the two iron oxides identified in this study to those listed in the JCPDS card index. 251 Figure 2-7. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the laboratory standard nodule Mn 191 6-8. 253 Figure 2-8. The XRD diffraction pattern of the laboratory standard crust DODO 14 DZ after the second stage of the sequential extraction 1 scheme. 254 INTENSITY (COUNTS/SECOND) o CO 255 Figure 2-9. The XRD diffraction pattern of the laboratory standard nodule Mn 191 6-8 after the second stage of the sequential extraction scheme. 256 INTENSITY (COUNTS/SECOND) o o o o CO (D CM O 257 Figure 2-10. The DXRD pattern, obtained after the second stage of leaching of the sequential extraction scheme on the laboratory standard crust DODO 14 DZ. DEGREES 2© 259 Figure 2-11. The D X R D pattern obtained after the second stage of leaching of the sequential extraction scheme on the laboratory standard nodule Mn 191 6-8. 100 Table 2-8. Comparison of the d-spacings (A) of the two iron oxides identified in this study to those listed in the JCPDS card index. F e r r i h y d r i t e This Study JCPDS Card No. 29-713 2 . 5 2 2 .50 2 . 2 5 2 .21 1 .96 1.96 1 .70 1.72 1 .50 1.51 1.46 1.48 Akaganeite This Study JCPDS Card No. 13-157 7 .49 7 .40 5 . 2 5 3 .65 3 .70 3 .311 2 . 6 1 6 2 .51 2 . 5 4 3 2 .343 2 . 2 8 5 2 .097 2 .064 1.944 1.854 1.746 1.71 1 .719 1.64 1.635 1.51 1 .515 1.497 1.480 1 .459 1 .438 1.374 2.3 DISCUSSION AND CONCLUSIONS In the crust samples, the majority of the Mn, Ni, and Co are associated with the manganese oxide mineral 5Mn02, while most of the Fe and Cu are probably associated in the iron oxide mineral ferrihydrite. Both SMn0 2 and ferrihydrite consist of a randomly disordered array of octahedra of Mn and Fe, respectively. In the nodule sample, most of the Mn and Cu and half of the Ni and Co are associated with the manganese oxide mineral todorokite, while most of the Fe and the remaining Ni and Co are contained by the iron oxide mineral akaganeite. Both todorokite and akaganeite are characterized by their well ordered tunnel structures. Most of the proposed selective sequential extraction schemes directed towards the study of manganese and iron oxides in soils have also used hydroxylamine hydrochloride in nitric acid to remove the Mn oxide minerals and ammonium oxalate in oxalic acid to remove the Fe oxide minerals. Murad & Schwertmann (1988) proposed that the extraction of manganese oxides from crusts and nodules by hydroxylamine hydrochoride causes an alteration in the iron oxide mineralogy. Hence, there is some doubt on the validity of the results from the D X R D patterns obtained after the second stage of the extraction procedure. Is the presence of ferrihydrite and akagneite in the DXRD patterns an artifact due to changes in the iron oxide mineralogy caused by the chemical leaching with 0.10M M-TjOHHCl in 0.01M HNO3 during the first stage of the sequential extraction procedure, or are they truely oxyhydroxides originally present in the crust and nodule? Although it can not be proven conclusively that the two stage selective sequential extraction scheme proposed above does not significantly change the iron oxide mineralogy, several pieces of evidence suggests that the iron oxides identified in the D X R D patterns are the authentic iron mineral phases and not artifacts caused, by the chemical leaching. Firstly, the observed iron oxides have D X R D patterns 2 6 3 characterized by broad peaks. If the chemical leaching with 0.10M NH20HHC1 in 0.01M HN03 changed the iron oxide mineralogy they most likely would invert to goethite which is the polymorph most other FeOOH phases revert to (Murray, 1979). Goethite was observed in the XRD patterns of the hydroxylamine-treated crusts studied by Murad & Schwertmann (1988). Secondly, although Murad & Schwertmann (1988) also identified feroxyhite in the X R D patterns of the hydroxylamine-treated crusts, they concluded that Mossbauer spectra of the untreated crusts indicates that most of the Fe is bound to a ferrihydrite-like phase that is intimately intergrown with the Mn oxides not feroxyhite. The presence of ferrihydrite was indeed identified in the crust sample studied here. 264 2.4 REFERENCES Acharya, S., Anand, S., Das, S.C., Das, R.P., & Jena, P.K., 1989. Ammonia leaching of ocean nodules using various reductants. Erzmetall, 42(2):66-73. Aguilera, N.H., & Jackson, M.L., 1953. Iron oxide removal from soils and clays. Soil Sci. Soc. Amer. Proc, 17:359-364. Aleksandrova, L.N., 1960. The use of sodium pyrophosaphate for isolating free humic substances and their organic-mineral compounds from soil. Soviet Soil Sci., 2:190-197. 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Uber die natur der manganknollen. Schweiz. Miner. Petrogr. Mitt., 36:49-62. 265 Cambell, A.S., & Schwertmann, U.S., 1984. Iron Oxide mineralogy of placic horizons. Jour, of Soil Sci., 35:569-582. Chao, T.T., 1972. Selective dissolution of manganese oxides from soils and sediments with acidified hydroxylamine hydrochloride. Soil Sci. Soc. Amer. Proc, 36:764-768. Chao, T.T., & Sanzolone, R.F., 1973. Atomic absorbtion spectrophotometric determination of microgram levels of Co, Ni, Cu, Pb, and Zn in soil and sediment extracts containing large amounts of Mn and Fe. Journ. Res. U.S. Geol. Surv., l(6):681-685. Chao, T.T., & Theobald Jr., P.K., 1976. The significance of secondary iron and manganese oxides in geochemical exploration. Econ. Geol., 71:1560-1569. Chao, T.T., & Zhou, L., 1983. Extraction techniques for selective dissolution of amorphous iron oxides from soils and sediments. Soil Sci. Soc. Amer. J., 47:225-232. Chester, R., & Hughes, M.J., 1967. A chemical technique for the separation of ferromanganese minerals, carbonate, minerals and adsorbed trace elements from pelagic sediments. Chem. Geol., 2:249-262. Coffin, D.E., 1963. A method for the detrmination of free iron in soils and clays. Canadian Jour, of Soil Sci., 43:7-17. de Endredy, A.S., 1963. Estimation of free iron oxides in soils and clays by a photolytic method. Clay Minerals, 5:218-226. Deb, B.C., 1949. The estimation of free iron oxides in soils and clays and their removal. J. Soil Sci., 1:212-220. Gallagher, P.H., & Walsh, T., 1943. The solubility of soil components in oxalic acid as an index to the effects of weathering. Royal Irish Acad. Proc, 498:1-26. Gianone, C , da Cruz, F., & Doupnik, J.R., 1988. MS-DOS Kermit User Guide for the IBM Family, Compatibles, and Other MS-DOS Systems, unpublished, 100 pp. Glasby, G.P., 1972. The mineralogy of manganese nodules from a range of marine environments. Mar. Geol., 13:57-72. Han, K.N., & Fuerstenau, D.W., 1980. Extraction behavior of metal elements from deep-sea manganese nodules in reducing media. Mar. Min., 2(3): 155-169. Haynes, B.W., Magyar, M.J., & Goolay, F.E., 1987. Extractive metallurgy of ferromanganese crusts from the Necker Ridge Area, Hawaiian Exclusive Economic Zone. Mar. Mining, 6:23-36. Hoffman, S.J., & Fletcher, W.K., 1979. Selective sequential extraction of Cu, Zn, Fe, Mn, and Mo from soils and sediments. Int. Geochem. Explor. Symp. Proc, 7:289-299. 2 6 6 Holmgren, G.G.S., 1967. A rapid citrate-dithonite extractable iron procedure. Soil Sci. Soc. Amer. Proc, 31:210-211. Hubred, G., 1980. Manganese nodule extractive metallurgy review 1973-1978. Mar. Mining, 2(3):191-212. Hurlbut Jr, C.S., & Klein, C., 1977. Manual of Mineralogy (after James D. Dana), John Wiley & Sons, New York, 532 pp. Itoh, H., Okuwaki, A., & Okabe, T., 1980. Processing of Pacific Ocean manganese nodules. 12th. Annual Offshore Technology Conference, Proceedings, Vol. 3, pp. 359-368. Kilmer, V.J., 1960. The estimation of free iron oxides in soils. Soil Sci. Soc. Amer. Proc, 24:420-421. Le Riche, H.H. & Weir, A.H., 1963. A method of studying trace elements in soil fractions. Jour. Soil Sci., 14:225-235. McKeague, J.A., 1967. An evaluation of 0.1M pyrophosphate and pyrophosphate-dithionite in comparison with oxalate as extractants of the accumulation products on Podsols and some other soils. Canadian Jour. Soil Sci., 47:95-99. McKeague, J.A, Brydon, J.E., & Miles, N.M., 1971. Differentiation of iforms of extractable iron and aluminium in soils. Soil Sci. Soc. Amer. Proc, 35:33-38. McKeague, J.A., & Day, J.H., 1966. Dithionite and oxalate-extractable Fe and Al as aide in differentiating various classes of soils. Canadian Jour. Soil Sci., 46:13-22. Mehra, O.P., & Jackson, M.L., 1960. Iron oxide removal from soils and clays by a dithionite-citrate system buffered with sodium bicarbonate. 7th Natl., Conf., on Clays and Clay Minerals, pp. 317-327. Mitchell. B.D., & Mackenzie, R . C , 1954. Removal of free-iron oxide from clays. Soil Sci., 77:173-184. Moorby, S.A., & Cronan, D.S., 1981. The distribution of elements between co-existing phases in some marine ferromangese-oxide deposits. Geochim. Cosmochim. Acta, 45:1855-1877. Murad, E. , & Schwertmann, U., 1988. Iron oxide mineralogy of some deep-sea ferromanganese crusts. Amer. Mineral., 73:1395-1400. Murray, J.W., 1979. Iron-oxides. In Mineralogical Society of America Short Course Notes, Marine Minerals fed. by R.G. Burns), Vol. 6. LithoCrafters Inc., Chelsea, Michigan, pp. 47-98. Oades, J.M., 1963. The nature and distribution of iron compounds in soils. Soils Fert., 26:69-80. Salomons, W., Forstner, U., 1983. "Metals in the Hydrocycle". Springer-Verlag. Berlin. 267 Savitzky, A., & Golay, M.J., 1964. Smoothing and differentiation of data by simplified least squares procedures. Anal. Chem., 36(8): 1627-1639. Schulze, D.G., 1981. Identification of soil iron oxide minerals by differential X-ray diffraction. Soil Sci. Soc. Amer. J., 45:437-440. Schwertmann, U., 1964. Differenzierung der eisenoxide des Bodens durch extraktion mit ammoniumoxalat-losung. Zietschrift fur Pflanzenernahrung, Dungung und Bodenkunde, 105:194-202. Schwertmann, U., Carlson, L., & Murad, E., 1987. Properties of iron oxides in two Finnish lakes in relation to the environment of their formation. Clays and Clay Minerals, 35(4):297-304. Shen, G.T., & Boyle, E.A., 1988. Determination of lead, cadmium and other trace metals in annually-banded corals. Chem Geol., 67:47-62. Takematsu, N., 1979. The incorporation of minor transition metals into marine manganese nodules. J. Oceanogr. Soc. Jpn., 35:191-198. Tipping, E. , Hetherington, N.B., Hilton, J., Thompson, D.W., Bowls, E. , & Taylor, J.H., 1985. Artifacts in the use of selective chemical extraction to determine distributions of metals between oxides of manganese and iron. Anal. Chem., 57:1944-1946. 2.5 APPENDIX A THE WEIGHT PERCENT Mn, Fe, Cu, Ni, AND Co IN THE LABORATORY STANDARD CRUST AS DETERMINED FROM THE LEACHATES The results in this Appendix are listed under the experimental order inwhich they were tested. The reagent used in each experiment are listed below. Experiment 1: 0.25M NH 2 OH-HCl in 0.25M HC1 Experiment 2: 0.25M N H 2 O H H C l in 0.25M HAc Experiment 3: 0.1M NH 20H-HC1 in 0.01M HN03 Experiment 4: 0.175M Ammonium Oxalate in 0.1M Oxalic Acid (Dark Method) Experiment 5: 0.175M Ammonium Oxalate in 0.1M Oxalic Acid (Photolytic Method) Experiment 6: 1 part H 2 N N H 2 , 6 parts concentrated N H 4 O H , and 3 parts 0.3M Citric Acid in 7N N H 4 O H 269 EXPERIMENT NO. TIME Mn (hr) EXPERIMENT 1 0 .5 12 .66 Sample:Solution 1 13 .93 1:250 2 15 .12 4 13 .83 8 14 .51 EXPERIMENT 1 0 .5 14 .06 Sample:Solution 1 13 .61 2:250 2 12 .52 4 12 .76 • 8 13 .51 EXPERIMENT 1 0 .5 12 .32 Sample:Solution 1 13 .58 3:250 2 12 .69 4 8 .21 8 12 .79 EXPERIMENT 1 0 .5 12 .62 Sample:Solution 1 11 .92 4:250 2 12 .23 4 12 .45 8 11 .95 EXPERIMENT 1 0 .5 11 .69 Sample:Solution 1 12 .41 5:250 2 12 .07 4 13 .26 8 12 .95 EXPERIMENT 2 0 .5 10 .98 Sample:Solution 1 10 .84 1:250 2 12 .62 4 11 .16 8 13 .38 EXPERIMENT 2 0 .5 12 .13 Sample:Solution 1 11 .98 2:250 2 11 .53 4 11 .30 8 12 .14 16 12 .03 EXPERIMENT 2 0 .5 11 .07 Sample:Solution 1 11 .24 3:250 2 11 .93 4 11 .18 8 11 .22 Fe Cu Ni Co (Weight Percent) 10.43 0.09 0. 21 0.29 10.25 0.09 0. 21 0.28 12.59 0.09 0. 21 0.29 7.43 0.09 0. 21 0.29 6.79 0.08 0. 20 0.30 11.78 0.09 0. 19 0.26 11.81 0.09 0. 19 0.30 12.66 0.09 0. 18 0.31 13.61 0.09 0. 18 0.31 12.99 0.09 0. 18 0.31 13.54 0.08 0. 17 0.25 11.91 0.09 0. 18 0.24 12.71 0.09 0. 18 0.24 7.72 0.09 0. 18 0.24 13.31 0.09 0. 17 0.24 11.74 0.09 0. 16 0.21 11.68 0.08 0. 15 0.20 12.34 0.09 0. 15 0.21 11.94 0.09 0. 15 0.21 11.47 0.09 0. 15 0.20 10.89 0.07 0. 13 0.18 11.42 0.08 0. 13 0.18 11.54 0.08 0. 14 0.17 11.66 0.08 0. 14 0.17 11.89 0.08 0. 14 0.17 3.93 0.07 0. 17 0.36 4.69 0.08 0. 18 0.36 4.19 0.08 0. 18 0.35 5.12 0.08 0. 18 0.35 8.58 0.08 0. 18 0.35 5.67 0.07 0. 15 0.29 7.31 0.07 0. 15 0.30 8.78 0.07 0. 15 0.30 9.61 0.07 0. 14 0.30 9.88 0.08 0. 15 0.29 7.19 0.07 0. 15 0.28 4.91 0.06 0. 15 0.25 5.85 0.06 0. 16 0.25 7.28 0.06 0. 16 0.24 7.65 0.06 0. 16 0.24 7.65 0.06 0. 16 0.24 EXPERIMENT 2 0 .5 11.02 3.86 0.05 0.11 0.20 Sample:Solution 1 11.48 4.31 0.05 0.14 0.20 4:250 2 10.73 4.67 0.05 0.14 0.20 4 10.68 5.03 0.05 0.15 0.20 8 11.06 5.71 0.05 0.15 0.20 EXPERIMENT 2 0 .5 10.76 4.19 0.04 0.14 0.17 Sample:Solution 1 11.37 3.99 0.04 0.14 0.17 5:250 2 11.03 4.03 0.04 0.13 0.17 4 12.79 4.45 0.05 0.13 0.17 8 12.09 5.02 0.05 0.13 0.17 EXPERIMENT 3 0 .5 11.09 2.12 0.02 0.19 0.30 Sample:Solution 1 10.25 1.62 0.02 0.19 0.32 1:250 2 9.73 1.80 0.02 0.19 0.32 4 10.79 0.17 0.03 0.20 0.33 8 9.59 3.62 0.03 0.20 0.33 EXPERIMENT 3 0 .5 10.19 2.09 0.01 0.16 0.24 Sample:Solution 1 9.81 1.92 0.01 0.16 0.27 2:250 2 10.35 2.81 0.00 0.17 0.26 4 11.73 0.00 0.01 0.17 0.28 8 10.35 3.71 0.02 0.17 0.27 EXPERIMENT 3 0 .5 10.60 0.95 0.00 0.10 0.16 Sample:Solution 1 11.16 1.24 0.00 0.11 0.18 3:250 2 10.68 0.66 0.01 0.10 0.18 4 10.62 0.18 0.01 0.10 0.18 8 12.44 0.55 0.01 0.12 0.22 EXPERIMENT 3 0 .5 9.56 0.49 0.00 0.07 0.08 Sample:Solution 1 10.08 0.06 0.00 0.09 0.11 4:250 2 9.61 0.06 0.00 0.09 0.10 4 9.98 0.04 0.00 0.08 0.10 8 10.25 0.06 0.01 0.09 0.15 EXPERIMENT 3 0 .5 8.40 0.48 0.00 0.03 0.04 Sample:Solution 1 8.11 1.13 0.00 0.04 0.05 5:250 2 8.45 0.30 0.00 0.04 0.06 4 9.48 0.66 0.00 0.04 0.07 8 9.40 0.00 0.00 0.05 0.09 EXPERIMENT 4 0 .5 10.63 13.95 0.06 0.20 0.35 Sample:Solution 1 10.08 13.60 0.06 0.18 0.38 1:250 2 9.84 16.53 0.07 0.21 0.37 4 9.27 17.18 0.07 0.21 0.35 8 10.40 16.30 0.06 0.20 0.34 EXPERIMENT 4 0 .5 9.63 11.41 0.07 0.19 0.29 Sample:Solution 1 10.85 11.54 0.08 0.11 0.31 2:250 2 12.45 12.53 0.09 0.20 0.31 4 11.00 10.71 0.08 0.20 0.32 8 10.58 9.20 0.08 0.20 0.31 EXPERIMENT 4 0 .5 8 .86 8 .76 0.07 0. 14 0.24 Sample:Solution 1 9 .87 8 .30 0.07 0. 15 0.25 3:250 2 10 .05 13 .10 0.07 0. 16 0.27 4 10 .38 11 .90 0.06 0. 15 0.26 8 10 .24 11 .39 0.08 0. 16 0.28 EXPERIMENT 4 0 .5 8 .73 7 .09 0.07 0. 12 0.20 Sample:Solution 1 8 .53 7 .71 0.07 0. 12 0.20 4:250 2 8 .10 5 .51 0.06 0. 11 0.19 4 8 .28 5 .72 0.07 0. 11 0.19 8 8 .80 8 .59 0.07 0. 12 0.20 EXPERIMENT 4 0 .5 6 .60 4 .54 0.05 0. 11 0.18 Sample:Solution 1 6 .87 3 .87 0.04 0. 11 0.18 5:250 2 6 .38 4 .36 0.05 0. 11 0.18 4 6 .72 4 .23 0.05 0. 11 0.20 8 6 .83 6 .21 0.05 0. 11 0.20 EXPERIMENT 5 1 11 .30 9 .45 0.08 0. 18 0.33 Sample:Solution 1:250 EXPERIMENT 5 1 9 .91 9 .02 0.08 0. 16 0.32 Sample:Solution 2:250 EXPERIMENT 5 1 8 .10 9 .01 0.07 0. 14 0.27 Sample:Solution 3:250 EXPERIMENT 5 1 7 .28 5 .98 0.07 0. 12 0.21 Sample:Solution 4:250 EXPERIMENT 5 1 5 .42 4 .84 0.06 0. 09 0.17 Sample:Solution 5:250 EXPERIMENT 6 0 .5 1 .98 0 .00 0.08 0. 16 0.22 Sample:Solution 1 6 .48 1 .43 0.08 0. 18 0.23 1:250 2 5 .93 0 .00 0.07 0. 14 0.22 4 5 .47 3 .05 0.07 0. 13 0.21 8 7 .20 0 .00 0.07 0. 15 0.22 EXPERIMENT 6 0 .5 6 .24 0 .42 0.06 0. 11 0.20 Sample:Solution 1 5 .11 3 .24 0.06 0. 12 0.20 2:250 2 8 .72 0 .43 0.05 0. 12 0.19 4 10 .05 2 .92 0.06 0. 12 0.20 8 8 .80 2 .61 0.05 0. ,13 0.20 EXPERIMENT 6 0 .5 9.36 2.88 0.05 0.10 0. 19 Sample:Solution 1 9.66 4.03 0.05 0.11 0. 19 3:250 2 9.92 4.46 0.05 0.12 0. 18 4 10.06 3.82 0.05 0.11 0. 19 8 10.15 3.18 0.04 0.10 0. 19 EXPERIMENT 6 0 .5 9.47 2.68 0.04 0.08 0. 18 Sample:Solution 1 9.98 3.09 0.04 0.08 0. 18 4:250 2 10.27 1.92 0.04 0.08 0. 19 4 9.57 2.68 0.05 0.07 0. 19 8 9.95. 2.46 0.05 0.08 0. 19 EXPERIMENT 6 0 .5 8.87 0.47 0.04 0.09 0. 18 Sample:Solution 1 8.91 1.35 0.04 0.09 0. 17 5:250 2 9.25 1.66 0.04 0.08 0. 18 4 9.54 1.89 0.04 0.08 0. 18 8 9.39 1.91 0.04 0.07 0. 18 273 2.6 APPENDIX B PERCENT Mn, Fe, Cu, Ni, AND Co REMOVED FROM THE LABORATORY STANDARD CRUST The results in this Appendix are listed under the experimental order inwhich they were tested. The reagent used in each experiment are listed below. Experiment 1: 0.25M NH 2OH-HCl in 0.25M HC1 Experiment 2: 0.25M NH 2OH-HCl in 0.25M HAc Experiment 3: 0.1M NH 2OH-HCl in 0.01M HN03 Experiment 4: 0.175M Ammonium Oxalate in 0.1M Oxalic Acid (Dark Method) Experiment 5: 0.175M Ammonium Oxalate in 0.1M Oxalic Acid (Photolytic Method) Experiment 6: 1 part H 2 NNH 2 , 6 parts concentrated N H 4 O H , and 3 parts 0.3M Citric Acid in 7N N H 4 O H \ EXPERIMENT NO. TIME Mn (hr) EXPERIMENT 1 0 .5 101. 07 Sample:Solution 1 111. 13 1:250 2 120. 66 4 110. 29 8 115. 83 EXPERIMENT 1 0 .5 112. 19 Sample:Solution 1 108. 59 2:250 2 99. 94 4 101. 81 8 107. 80 EXPERIMENT 1 0 .5 98. 35 Sample:Solution 1 108. 34 3:250 2 101. 28 4 65. 50 8 102. 14 EXPERIMENT 1 0 .5 100. 71 Sample:Solution 1 95. 12 4:250 2 97. 57 4 99. 34 8 95. 41 EXPERIMENT 1 0 .5 93. 31 Sample:Solution 1 99. 07 5:250 2 96. 32 4 105. 85 8 103. 31 EXPERIMENT 2 0 .5 87. 59 Sample:Solution 1 86. 52 1:250 2 100. 72 4 89. 08 8 106. 74 EXPERIMENT 2 0 .5 96. 83 Sample:Solution 1 95. 65 2:250 2 92. 04 4 90. 18 8 96. 93 16 96. 05 EXPERIMENT 2 0 .5 88. 38 Sample:Solution 1 89. 75 3:250 2 95. 22 4 89. 22 8 89. 52 Fe Cu Ni Co (Percent) 67 .12 144 .00 137 .63 95 .82 65 .92 144 .00 138 .67 94 .73 81 .00 142 .83 139 .20 98 .02 47 .75 142 .00 137 .63 96 .92 43 .69 140 .58 134 .47 99 .12 75 .77 148 .08 126 .13 85 .75 75 .93 143 .83 123 .77 101 .67 81 .42 142 .96 119 .82 103 .49 87 .49 146 .37 118 .63 103 .86 83 .56 154 .92 119 .02 104 .41 87 .08 136 .94 114 .10 82 .98 76 .58 144 .72 117 .08 81 .56 81 .77 114 .17 117 .68 81 .56 49 .62 150 .81 117 .38 81 .56 85 .63 153 .03 113 .81 81 .32 75 .52 142 .81 104 .09 68 .71 75 .08 138 .10 103 .20 68 .09 79 .38 142 .25 102 .98 68 .80 76 .79 144 .33 102 .53 68 .45 73 .79 146 .00 97 .85 68 .00 70 .05 125 .22 86 .63 36 .49 73 .44 129 .60 89 .82 36 .54 74 .24 131 .78 91 .10 36 .04 75 .00 135 .55 90 .73 36 .13 76 .43 135 .87 91 .10 35 .59 25 .24 125 .75 114 .40 118 .67 30 .19 129 .83 119 .60 119 .82 27 .00 127 .08 120 .33 117 .53 32 .92 131 .17 118 .87 117 .53 55 .14 138 .00 117 .37 118 .28 36 .48 111 .75 99 .83 96 .58 47 .02 115 .79 99 .10 99 .99 56 .48 118 .54 100 .58 100 .57 61 .82 121 .92 96 .87 99 .23 63 .55 129 .38 102 .80 97 .53 46 .29 125 .33 100 .58 94 .67 31 .56 98 .83 102 .88 82 .26 37 .60 99 .25 106 .50 81 .99 46 .83 101 .86 105 .77 81 .56 49 .23 104 .47 105 .29 81 .32 49 .25 105 .78 107 .23 80 .52 275 EXPERIMENT 2 0 .5 87 .99 24 .80 81 .94 76 .25 66 .91 Sample:Solution 1 91 .58 27 .77 85 .52 96 .20 66 .31 4:250 2 85 .64 30 .06 86 .19 94 .38 66 .20 4 85 .25 32 .32 91 .40 97 .83 66 .20 8 88 .27 36 .73 90 .08 98 .93 66 .61 EXPERIMENT 2 0 .5 85 .85 26 .94 74 .02 91 .25 56 .57 Sample:Solution 1 90 .77 25 .69 73 .77 91 .11 56 .16 5:250 2 88 .02 25 .91 74 .02 89 .01 55 .01 4 102 .10 28 .64 80 .32 89 .61 55 .67 8 96 .49 32 .25 82 .15 88 .56 56 .24 EXPERIMENT'3 0 .5 88 .52 13 .65 40 .33 125 .07 101 .58 Sample:Solution 1 81 .77 10 .45 35 .00 129 .80 107 .82 1:250 2 77 .61 11 .58 37 .67 125 .07 106 .35 4 86 .16 11 .25 50 .92 132 .63 110 .37 8 76 .59 23 .30 52 .25 132 .63 110 .00 EXPERIMENT 3 0 .5 81 .36 13 .49 16 .17 105 .55 106 .03 Sample:Solution 1 72 .28 12 .37 10 .21 107 .90 118 .72 2:250 2 82 .60 18 .09 8 .25 110 .75 116 .60 4 93 .57 0 .00 23 .46 114 .07 122 .62 8 82 .60 23 .87 34 .04 113 .12 121 .89 EXPERIMENT 3 0 .5 84 .60 6 .11 3 .83 65 .58 80 .88 Sample:Solution 1 89 .04 7 .98 6 .36 72 .99 92 .09 3:250 2 85 .24 4 .23 11 .05 68 .88 89 .15 4 84 .73 1 .18 15 .31 69 .97 91 .91 8 99 .28 3 .54 15 .31 80 .69 109 .38 EXPERIMENT 3 0 .5 76 .31 3 .17 2 .55 35 .80 26 .64 Sample:Solution 1 80 .46 0 .40 1 .69 46 .93 37 .95 4:250 2 76 .67 0 .40 3 .83 43 .42 34 .92 4 79 .61 0 .24 5 .11 39 .51 34 .18 8 81 .78 0 .40 14 .42 58 .46 49 .73 EXPERIMENT 3 0 .5 67 .07 3 .12 4 .43 21 .63 13 .21 Sample:Solution 1 64 .75 7 .30 1 .42 25 .79 17 .68 5:250 2 67 .46 1 .96 3 .68 25 .96 19 .47 4 75 .65 4 .24 3 .18 28 .46 23 .86 8 75 .02 0 .00 5 .45 33 .31 29 .67 EXPERIMENT 4 0 .5 84 .79 89 .71 105 .67 133 .93 118 .40 Sample:Solution 1 80 .41 87 .46 100 .67 119 .07 126 .43 1:250 2 78 .52 106 .29 123 .00 137 .00 124 .00 4 73 .96 110 .50 120 .50 137 .00 117 .60 8 83 .00 104 .82 105 .67 135 .47 114 .40 EXPERIMENT 4 0 .5 76 .88 73 .36 125 .08 125 .09 127 .04 Sample:Solution 1 86 .64 74 .23 130 .00 128 .17 139 .33 2:250 2 99 .40 80 .58 148 .75 134 .87 136 .13 4 87 .79 68 .89 138 .75 136 .67 143 .62 8 84 .40 59 .16 133 .75 135 .60 137 .20 276 EXPERIMENT 4 0 .5 70. 74 56 .31 121 .22 93 .13 118 .23 S a m p l e : S o l u t i o n 1 70. 74 53 .75 125 .72 97 .04 126 .30 3:250 2 80. 19 84 .27 118 .17 104 .38 133 .93 4 82. 85 76 .56 128 .78 102 .42 132 .58 8 81. 74 73 .26 148 .39 107 .31 140 .20 EXPERIMENT 4 0 .5 69. 67 45 .65 111 .29 82 .68 66 .07 Sampl e : S o l u t i o n 1 68. 04 49 .56 111 .29 82 .68 65 .39 4:250 2 64. 64 35 .41 106 .75 76 .82 64 .28 4 66. 04 36 .78 113 .00 76 .45 65 .17 8 70. 27 55 .29 113 .00 80 .85 65 .39 EXPERIMENT 4 0 .5 52. 71 29 .23 79 .57 71 .96 59 .52 Sampl e : S o l u t i o n 1 58. 83 24 .89 75 .30 75 .92 58 .89 5:250 2 58. 88 28 .04 77 .43 74 .51 60 .15 4 53. 66 27 .23 79 .13 74 .51 66 .68 8 54. 54 39 .96 84 .67 76 .20 65 .83 EXPERIMENT 5 1 90. 18 60 .77 141 .00 117 .60 108 .53 S a m p l e : S o l u t i o n 1:250 EXPERIMENT 5 1 79. 09 58 .03 129 .92 105 .53 144 .38 Sampl e : S o l u t i o n 2:250 EXPERIMENT 5 1 64. 64 57 .93 120 .56 91 .60 133 .55 S a m p l e : S o l u t i o n 3:250 EXPERIMENT 5 1 58. 11 38 .50 117 .50 78 .97 71 .24 Sampl e : S o l u t i o n 4:250 EXPERIMENT 5 1 43. 25 31 .12 105 .03 62 .61 58 .47 Sample:Solution 5:250 EXPERIMENT 6 0 .5 15. 76 0 .00 128 .50 109 .97 73 .55 Sample:Solution 1 51. 68 9 .16 126 .92 120 .63 76 .43 1:250 2 47. 29 0 .00 114 .50 92 .27 73 .55 4 43. 69 19 .61 120 .75 85 .90 70 .65 8 57. 46 0 .00 114 .50 99 .27 73 .55 EXPERIMENT 6 0 .5 49. 77 2 .73 106 .29 73 .68 88 .73 S a m p l e : S o l u t i o n 1 40. 79 20 .82 103 .17 81 .70 88 .73 2:250 2 69. 62 2 .75 92 .29 80 .37 86 .18 4 80. 19 18 .81 93 .08 81 .70 88 .10 8 70. 23 16 .80 89 .17 84 .37 88 .10 277 EXPERIMENT 6 0 .5 74 .69 18 .54 84 .67 68 .72 95 .35 S a m p l e : S o l u t i o n 1 77 .08 25 .94 85 .17 76 .49 93 .83 3:250 2 79 .20 28 .72 78 .67 78 .21 92 .31 4 80 .33 24 .59 76 .64 72 .18 93 .33 8 80 .99 20 .47 66 .64 66 .13 94 .84 EXPERIMENT 6 0 .5 75 .61 17 .24 74 .00 53 .48 60 .83 S a m p l e : S o l u t i o n 1 79 .71 19 .86 72 .88 51 .54 61 .34 4:250 2 81 .95 12 .34 68 .00 50 .89 62 .61 4 76 .41 17 .24 78 .13 48 .30 61 .85 8 79 .41 15 .84 79 .25 50 .89 61 .85 EXPERIMENT 6 0 .5 70 .82 3 .05 67 .37 62 .22 58 .55 S a m p l e : S o l u t i o n 1 71 .11 8 .65 60 .82 60 .09 57 .94 5:250 2 73 .82 10 .67 61 .72 50 .51 59 .35 4 76 .09 12 .19 64 .68 51 .04 60 .15 8 74 .98 12 .28 66 .17 46 .25 59 .55 2.7 APPENDIX C THE SAVTTZKY & GOLAY (1964) SMOOTHING PROGAM TRANSLATED INTO GW BASIC Total% = 15000 ADYNAMIC DIM D(Total%), Array % (Total %), SG%(34) DIM B(Total%) CLS INPUT "file name (no extension)"; Filenames OPEN Filenames + ".prn" FOR INPUT AS #1 OPEN Filenames + ".out" FOR OUTPUT AS #2 PRINT "Wait file crunching" DO WHILE NOT EOF(l) Count = Count + 1 INPUT #1, D(Count), Array%(Count) LOOP PRINT "Total count = "; Count tl = 1: t2 = Count GOSUB smooth GOSUB Outfile END smooth: ' Savitsky-Golay smoothing INPUT \ 17, or 23 point smooth...9,17,23 "; PR IF PR = 0THENPR = 9 IF PR = 9 THEN PO = 1 PT = 9: OF = 4 RESTORE 5090 FOR I = 1 TO PT READ SG%(I) NEXT I END IF IF PR = 17 THEN PO = 2 PT = 17: OF = 8 RESTORE 5100 FOR I = 1 TO PT to READ SG%(I) NEXT I END IF IF PR = 23 THEN P0 = 3 PT = 23: OF = 12 RESTORE 5110 FOR I = 1 TO PT READ SG%(I) NEXT I END IF CLS LOCATE 1,1: PRINT "wait, smoothing data" FOR I = tl TO t2 B(I) = 0: DF% = 0 FOR J =-OF TO OF IF NOT (I + J<10RI + J> Count) THEN 'put integer point into larger number class Cast = Array%(I + J) B(I) = B(I) + Cast * SG%(J + OF + 1) DF% = DF% + SG%(J + OF + 1) END IF NEXT J B(I) = B(I)/DF% 'PRINT Array%(I), B(I) NEXT I RETURN Outfile: FOR I = tl TO t2 'PRINT USING "###.##"; D(I), B(I) PRINT #2, USING "####.##"; D(I), B(I) NEXT I RETURN ' quadratic,cubic 5090 DATA -21,14,39,54,59,54,39,14,-21:' 9 point 5100 DATA -21,-6,7,18,27,34,39,42,43,42,39,34,27,18,7,-6,-21:' 17 point 5110 DATA -42,-21,-2,15,30,43,54,63,70,75,78,79,78,75,70,63,54,43,30,15,-2,-21,-42: '23 point 282 CHAPTER 3 THE APPLICATION OF THE SELECTIVE SEQUENTIAL EXTRACTION SCHEME AND THE DIFFERENTIAL X-RAY DIFFRATION TECHNIQUE TO A SMALL POPULATION OF CRUSTS AND NODULES FROM THE NORTHEAST EQUATORIAL PACIFIC OCEAN 283 3.1 INTRODUCTION 3.1.1 PREVIEW In Chapter 1, a large population of crusts and nodules from the northeastern equatorial Pacific Ocean were analysed for their major element composition. From the major element compositions, different groups of crusts and nodules could be identified by their distinctive compositons and inter-element correlations. The distinctive compositions were related to the environment of formation while the inter-element correlations were related to the mineralogy identified from a bulk powdered sample. In Chapter 2, a two stage selective sequential extraction scheme as well as a D X R D technique was developed for selectively removing and identifying first the manganese and then the iron oxyhydroxides present in crusts and nodules. The concentrations of Mn, Fe, Cu, Ni, and Co associated with the manganese phase(s) and the iron phase(s) could then be determined. The selective sequential extraction scheme and the DXRD technique were developed on laboratory standard crust and nodule samples to determine the precission and accuracy of the methods of analysis. In this chapter the two stage selective sequential extraction scheme and the D X R D technique will be used on a small number of samples selected from the large population of crusts and nodules studied in Chapter 1. 3.1.2 STATEMENT OF T H E PROBLEM Although Chapter 1 showed that inter-element correlations existed between Mn and Fe and other elements in crusts and nodules, only the correlations with Mn could be attributed to manganese oxide phase(s) identified in a bulk powdered sample. Examination of the compositional data showed that inter-element 2 8 4 correlations with Fe did exist, but how those elements associated with Fe were hosted within the crusts and nodules remained unkown. The application of the two stage selective sequential extration scheme and the D X R D technique on a small population of crusts and nodules from the northeastern equatorial Pacific Ocean was studied for two purposes: (1) to separate the manganese oxides from the iron oxyhydroxides and to identify the iron oxyhydroxide phase(s) present in crusts and nodules; and (2) to identify the paritioning of the Cu, Ni, and Co concentrations between the manganese and iron oxides in crusts and nodules. 3.2 SELECTION OF SAMPLES In Chapter 1 a large number of crusts and nodules from the northeast equatorial Pacific Ocean were divided into two study areas and the crusts and nodules from each study area could be classified into different groups based on their distinctive compositions. To achieve the two purposes set out in this chapter, two samples from each group of crusts and nodules from the two study areas was selected for analysis. The Fe-rich hydrothermal crusts from Survey Region B were not analyzed because such crusts contain little or no manganese so there is no manganese oxide(s) present in these samples, amorphous hydrated iron oxides and silica are the dominant iron- and silica rich mineral phase present and these crusts contain low concentrations of Cu, Ni and Co. Because the manganese phase mineralogy does not exist and the iron phase mineralogy has already been identified and is found to contain little or no Cu, Ni, and Co, there is no need to study Fe-rich hydrothermal crusts from Survey Region B. The location and depth of the samples selected for analysis in this chapter are listed in Table 3-1. Table 3-la lists the samples selected from Survey Region A while Table 3-lb lists the samples selected from Survey Region B. 285 Table 3-la. Location and depth of crust and nodule samples selected from Survey Region A for analysis. The location and depth of these samples are also shown in Figure 1-2 in Chapter 1. Sample L a t i t u d e Longitude Depth Degrees Minutes Degrees Minutes (m) Hydrog e n e t i c C r u s t s 7T0W 130 D-FRAG 8 20.0 N 164 21.7 W 1519 7TOW 142 D - l 18 8.1 N 169 4.0 W 2139 Hydrogenous Nodules DODO 12-2 D - l 18 38.0 N 162 8.0 W 5040 DODO 14-2 D-2 19 22.0 N 162 19.0 W 4868 D i a g e n e t i c Nodules Mn 39 8 16.4 N 150 59.6 W 4833 Mn 56 11 30.8 N 148 34.7 W 5128 286 T a b l e 3 - l b . L o c a t i o n a n d d e p t h o f crust a n d n o d u l e s a m p l e s s e l e c t e d f r o m S u r v e y R e g i o n B f o r analysis. T h e l o c a t i o n a n d d e p t h o f these s a m p l e s a r e a l s o s h o w n i n F i g u r e 1-3 i n C h a p t e r 1. Sample Latitude Degrees Minutes Hydrogenetic Crusts Henderson Smt 25 RISE III 28 D-1 13 15.0 N 46.0 N Mn-rich Hydrothermal Crusts QBR 22 D-1 9 55.2 N RISE III 3 D-1 8 49.5 N Longitude Degrees Minutes 119 101 104 103 40.0 W 52.3 W 29.0 W 55.0 W Depth (m) 64 1693 1680 2095 Hydrogenous and Diagenetic Nodules B 104 11 10.6 N 109 36.3 W 3522 B 114 14 35.1 N 121 3.7 W 4295 Mn-rich Hydrothermal Nodules CERS 20 D-2 11 14.3 N CERS 21 D-3 10 52.3 N 101 101 7.6 W 31.6 W 2975 3080 Fe-rich Hydrothermal Nodules DWBD 1-2 21 27.0 N S 74 23 43.0 N 126 124 43.0 W 6.0 W 4300 3787 287 3.3 ANALYTICAL METHODS A complete description of the XRF analysis has been given in Chapter 1 while a complete description of the selective sequential extraction scheme, and the differential X-ray diffraction technique has been given in Chapter 2. 3.4 RESULTS 3.4.1 BACKGROUND GEOCHEMISTRY AND MINERALOGY A complete discussion about the major element compostion and its relation to the mineralogy of crusts and nodules from Northeast Pacific Ocean is given in Chapter 1. In this section only a breif review about the behavour of Mn, Fe, Cu, Ni, and Co will be provided. The major element compostion of the untreated crust and nodule samples are listed in Table 3-2. Table 3-2a gives the major element compostion of those crusts and nodule samples from Survey Region A while Table 3-2b gives the major element compostion of those crusts and nodule samples from Survey Region B. The mineralogy of the untreated samples selected for the selective sequential extraction scheme and differential X-ray diffraction technique is also described. 288 Table 3-2a. The major element compostion of the bulk crust and nodule samples selected from Survey Region A. Results are listed as weight per cent. Element Samples Hydrogenetic C r u s t s 7 TOW 7 TOW 130 142 D-S i 1.16 3.09 T i 0.79 0.90 A l 0.14 0.66 Fe 10.22 12.76 Mn 23.76 17.19 Mg 1.17 0.85 Ca 2.29 2.78 Na 1.60 1.66 K 0.42 0.40 P 0.34 0.60 Co 0.92 0.64 N i 0.63 0.31 Cu 0.02 0.04 Zn 0.06 0.03 Ba 0.17 0.16 Element Samples Hydrogenous Nodules D i a g e n e t i c Nodules DODO DODO Mn 39 Mn 56 12-2 D - l 14-2 D-2 S i 8.23 6.42 6.38 5.12 T i 1.09 1.16 0.44 0.32 A l 2.77 1.82 2.54 2.13 Fe 13.19 15.34 6.39 5.00 Mn 11.69 11.41 23.97 26.53 Mg 1.05 0.97 2.17 1.98 Ca 2.04 3.08 1.56 1.52 Na 2.66 1.38 0.71 0.61 K 0.99 0.75 0.81 0.63 P 0.34 0.84 0.15 0.13 Co 0.28 0.29 0.19 0.18 N i 0.15 0.14 1.14 1.11 Cu 0.06 0.07 1.02 1.11 Zn 0.03 0.03 0.11 0.12 Ba 0.11 0.13 0.15 0.18 Table 3-2b. The major element compostion of the bulk crust and nodule samples selected from Survey Region B. Results are listed as weight per cent. Element Samples Hydrogenetic Crusts Mn-rich Hydrothermal Crusts HEN SMT RISE III QBR RISE III 28 D-1 22 D-1 3 D-1 Si 10.52 3.53 1. 25 0 .03 Ti 0.11 0.65 0. 04 0 .04 Al 0.88 0.83 0. 07 0 .00 Fe 12.67 14.54 4. 77 0 .23 Mn 19.72 16.38 33. 60 42 .34 Mg 2.18 1.06 1. 98 1 .68 Ca 0.68 1.84 1. 53 2 .94 Na 1.12 1.61 2. 31 2 .08 • K 2.34 0.39 0. 90 0 .72 P 0.15 0.41 0. 12 0 .02 Co 0.06 0.51 0. 00 0 .00 Ni 0.20 0.33 0. 12 0 .03 Cu 0.01 0.00 0. 01 0 .00 Zn 0.02 0.04 0. 06 0 .01 Ba 0.65 0.14 0. 09 0 .33 Element Samples Hydrogenous and Mn-rich Fe-rich Diagenetic Hydrothermal Hydrothermal Nodules Nodules Nodules B 104 B 114 CERS CERS DWBD -S 74 20 D-2 21 D-3 1-2 Si 4.99 6.67 4.14 2 .38 27.51 18.93 Ti 0.28 0.30 0.14 0 .09 0.26 0.43 Al 1.54 2.39 1.63 1 .14 1.58 5.13 Fe 7.24 5.29 3.57 1 .82 8.17 10.00 Mn 23.81 25.75 33.45 37 .22 6.01 4.67 Mg 1.40 1.97 2.28 2 .13 1.15 1.41 Ca 1.59 1.44 1.19 1 .15 0.37 0.90 Na 1.98 1.60 1.27 1 .37 0.84 2.72 K 0.67 1.07 0.83 0 .84 0.98 2.97 P 0.16 0.13 0.10 0 .08 0.06 0.18 Co 0.07 0.15 0.00 0 .01 0.09 0.10 Ni 0.88 1.12 0.63 0 .56 0.31 0.20 Cu 0.66 0.76 0.30 0 .25 0.14 0.08 Zn 0.12 0.11 0.14 0 .22 0.02 0.02 Ba 0.26 0.23 0.31 0 .29 0.56 0.14 290 3.4.1.1 Survey Region A 3.4.1.1.1 Crusts To examine the regional compositional variations with respect to Mn and Fe, the effects of the dilutent aluminosilicates and carbonate fluorapatite material must be removed (Calvert, 1978). Price & Calvert (1970) solved the problem by using element ratios instead of absolute abundances of elements to represent geochemical variations. Using the elemental ratio of Mn/Fe, the association of the major elements with either of the major oxide phases will become more apparent. Elements correlated with the manganese phase mineralogy will show a positive linear correlation with the Mn/Fe ratio. For Cu, Ni and Co, only Ni and Co show a strong correlation with Mn while Cu shows a very weak correlation (Figure 3-1). The X R D patterns of the hydrogenetic crusts selected for analysis shows that the dominant oxide phase present in these crusts is 5MnC*2 (Figure 3-2). 3.4.1.1.2 Nodules Although not the first, Halbach & Ozkara (1979) used the Mn/Fe ratio as a criterion for distinguishing between different types of nodules from a small study area located within Survey Region A. They descided that nodules with an Mn/Fe ratio less than 2.5 were hydrogenous in origin while nodules with an Mn/Fe ratio above 2.5 were diagenetic in origin. Nodules from Survey Region A can also be divided into these two groups and show a marked compositional distinction between them. As shown in Figure 3-3, hydrogenous nodules are depleted in Mn, Cu, and Ni compared to the diagenetic nodules which are enriched in these elements. Figure 3-1. The association of Cu, Ni with Mn/Fe in hydrogenetic crusts from Survey Region A. 0 . 4 0 o 0 . 3 0 - O 0 . 2 0 + o 0.10- o o o o O 0 . 0 0 - •ee-0 .00 .00 0 ° <9°o 2 .00 M n / F e 3 .00 O 4 . 0 0 1.50 1.00 + 0 .00 1.00 2 .00 3 .00 4 . 0 0 M n / F e 293 1.00 0 . 7 5 + *L 0 . 50 o a 0 . 2 5 + 0 .00 o o <3D° P o o ^ O o o - o ° o o o ° o _J I 0 .00 1.00 2 .00 M n / F e 3 .00 4 . 0 0 294 Figure 3-2. The XRD patterns of hydrogenetic crusts selected for the two stage selective sequential extraction scheme. 7T0W 130 D-FRAG 296 o co 297 Figure 3-3. The association of Cu, Ni with Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 2 9 9 It is interesting to note in Figure 3-3 that there is a sharp break in slope of a first order regression line drawn through the hydrogenous nodules compared to one drawn through the diagenetic nodules. For Cu and Ni, the slope of the regression line for the hydrogenous nodules is greater than that of the diagenetic nodules. A non-linear correlation between Ni and Cu versus the Mn/Fe ratio has also been observed by Halbach et al. (1981b) in nodules from the Northeast Pacific nodule belt and by Usui & Mita (1987) in nodules from the three survey areas of SONNE Cruise SO-25 in the Northeast equatorial Pacific. Halbach et al. (1981b) concluded that their non-linear regressions describe the natural saturation of divalent cations in the lattice of todorokite. The decrease in the slope of the first order regression lines from the hydrogenous nodules to the diagenetic nodules recovered from Survey Region A can therefore be attributed to the saturation of the todorokite crystal lattice by manganese and associated divalent cations. Cobalt shows a complex association with Mn and Fe, which is unlike that of Cu and Ni (Figure 3-4). In hydrogenous nodules, Co is positively correlated with Mn, whereas in diagenetic nodules Co is positively correlated with Fe. The complex association of Co with the manganese and iron oxide phases have been previously observed by Cronan & Tooms (1969), Price & Calvert (1970) and by Halbach et al. (1983). Price & Calvert (1970) suggested that this observed complex behavior of Co in nodules is due to C o ^ + substituting for M n 4 + in nodules containing S M n 0 2 as well as F e ^ + in the iron oxyhydroxide phases. Cobalt (III) (d )^ is stable when in the low spin state with octahedral coordination and has an ionic radius almost identical to that of F e 3 + or M n 4 + . Cobalt (III) will therefore preferentially sustitute for both F e 3 + in the F e O O H x n H 2 0 phase (Burns, 1965) and M n 4 + in the 5 M n 0 2 phase (Glasby & Thijessen, 1982a; Halbach et al, 1981a). Cobalt (III) will also substitute for M n 4 + in the "ceilings" of todorokite (Burns, 1976). 300 Figure 3-4. The complex association of Co with Mn/Fe. The open circles = diagenetic nodules, the filled circles = hydrogenous nodules. 0.60 0.00 2.00 4.00 6.00 8.00 Mn/Fe 3 0 2 The XRD patterns of the hydrogenous nodules selected for analysis shows that the dominant oxide phase present in these nodules is 5MnC»2 (Figure 3-5) while the diagentic nodules selected for analysis shows that the dominant oxide phases present these nodules is both todorokite and SMnG^ (Figure 3-6). Since hydrogenous nodules contain both SMnO ,^ this would explain the positive association of Co with Mn. Diagenetic nodules, on the other hand, contain mostly todorokite. Although the substitution of C o 3 + for M n 4 + in the "ceilings" of todorokite probably occurs, the substitution of C o 3 + for F e 3 + in the FeOOHxnFJ^O phase appears to be more dominant as seen by the correlation of Co with Fe in these nodules. 3.4.1.2 Survey Region B 3.4.1.2.1 Crusts Crusts from Survey Region B have an extremely wide range Mn/Fe ratios (0.06 < Mn/Fe > 222.68). Consequently, there is a high degree of fractionation of these two elements in the crusts from this region. The concentrations of Mn indicate that there are three distinct groups of crusts within Survey Region B. The largest group of crusts within Survey Region B have Mn concentrations ranging from 7 to 20 weight per cent. This group of hydrogenetic crusts show a strong positive linear correlations with Mn to Co, Cu, and Ni (Figure 3-7). The XRD patterns of the two hydrogenetic crusts selected for analysis are not consistant as to the dominant oxide phases present in these crusts (Figure 3-8). If the two hydrogenetic crusts selected for analysis are representative of hydrogentic crusts from this region, then the dominant oxide phases that can be present are birnessite, todorokite, and SMnC^. 303 Figure 3-5. The XRD patterns of hydrogenous nodules selected for the two stage selective sequential extraction scheme. DODO 12-2 D-1 DEGREES 20 DODO 14-2 D-2 100 CO o cn Figure 3-6. The XRD patterns of diagenetic nodules selected for the two stage selective sequential extraction scheme. MN 39 100 o MN 56 CO o CO Figure 3-7. The relationship between Mn with Cu, Ni, and Co. The open circles hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts. 0.30 O o 0.20 + 0.10 + 0.00 4Ar-0.00 O 15.00 + 30.00 45.00 Mn (%) 0.50 0.40 + 0.30 + 0.20 + 0.10 0.00 0.00 15.00 30.00 45.00 Mn {%) 0.30 0.20 + 0.10 + 0.00 0.00 15.00 30.00 45.00 Mn (%) 312 Figure 3-8. The XRD patterns of hydrogenetic crusts selected for the two stage selective sequential extraction scheme. Henderson Seamount 100 H OJ 315 Because of the different geochemical behavior of Fe and Mn, fractionation of the two elements is common in hydrothermal solutions (Lyle, 1981). This results in the formation of two distinct end member deposits: (1) Mn-enriched hydrothermal crusts, characterized by Mn concentrations above 30 weight per cent and generally very low Cu, Ni and Co contents with well-crystallized birnessite and todorokite (Figure 3-9), and (2) Mn-depleted hydrothermal crusts, characterized by Mn concentrations below 3 weight per cent also with very low Cu, Ni, and Co contents but are iron- and silica-rich and composed of amorphous hydrated iron oxides and silica, (Figure 3-10). The fractionation of Fe and Mn occurs as a result of the lower solubility of iron species as both Fe and Mn undergo oxidation (Krauskopf, 1957) by mixing of the reduced hydrothermal fluid with oxygenated bottom water. The geochemical association of Si with Fe may result from coprecipitation or adsorption of dissolved SiC»2 onto hydrated iron-oxide colloids. The low content of minor elements in these deposits results from: (1) the low concentrations of these elements relative to Fe and Mn in hydrothermal solutions, and (2) the rapid depostion of the deposits which minimizes adsorption of elements from seawater (Toth, 1980). In hydrogenetic crusts from this region, Co also shows an association with Fe, which is unlike that Cu and Ni (Figure 3-11). In the Mn-rich and Mn-depleted hydrothermal crusts, Co is so depleted the correlation with Fe is not observed. Price & Calvert (1970) suggested that this observed complex behavior of Co is due to C o 3 + substituting for M n 4 + in SMnG^ as well as F e 3 + in the iron oxyhydroxide phases. Cobalt (III) (d )^ is stable when in the low spin state with octahedral coordination and has an ionic radius almost identical to that of F e 3 + or M n 4 + . Cobalt (III) will therefore preferentially sustitute for both Fe^ "1" in the F e O O H x n H 2 0 phase (Burns, 1965) and M n 4 + in the 5 M n 0 2 phase (Glasby & Thijessen, 1982a; Halbach et al, 1981a). Cobalt (III) will also substitute for M n 4 + in the "ceilings" of todorokite (Burns, 1976). Since hydrogenetic crusts contain 316 Figure 3-9. The X R D patterns of Mn-enriched hydrothermal crusts selected for the two stage selective sequential extraction scheme. H RISE III 3 D-1 319 Figure 3-10. The XRD pattern of a Mn-depleted hydrothermal crust enriched in Fe and Si. 321 Figure 3-11. The relationship between Fe and Co. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the filled triangles = Mn-depleted hydrothermal crusts. 322 o o 0 . 3 0 0 .20 + 0 .10 0 .00 0 . 0 0 5 .00 10 .00 15 .00 2 0 . 0 0 2 5 . 0 0 Fe (%) 323 FeOOHxnH^O, SMnC^, and todorokite, this would explain the positive association of Co with Mn and Co with Fe. 3.4.1.2.2 Nodules The Mn/Fe ratios for nodules from Survey Region B are found to vary from 0.63 up to 23.93. Although the Mn/Fe ratios for the nodules is not as extreme as for the crusts (0.06 < Mn/Fe > 222.68), the concentrations of Cu, Ni, and Co will be considered with respect to Mn concentrations. The relationship of Mn with Cu, Ni, and Co indicate that three distinct groups of nodules can be distinguished within Survey Region B. The largest group of nodules has Mn concentrations ranging from 10 to 30 weight per cent, Mn/Fe ratios between 0.75 and 7.70, and show strong positive linear correlations between Mn and Cu, Ni, and Co (Figure 3-12). Unlike nodules from Survey Region A, this group of nodules does not show a distinct division between hydrogenous nodules (Mn/Fe < 2.5) and diagenetic nodules (Mn/Fe > 2.5). Although the range of Mn/Fe ratios shows that these two types of nodules are present, the two groups do not show the same variation in interelement correlations as seen in Survey Region A. For identification purposes, this large group of nodules will be called hydrogenous nodules. The XRD patterns of the hydrogenous nodules selected for analysis shows that the dominant oxide phase present in these nodules is todorokite and 5MnC>2 along with minor amounts of birnessite (Figure 3-13). The two remaining groups of nodules are characterized by their distinctively different concentrations of Mn. One group is highly enriched in Mn ( > 30 weight per cent) and has low conentrations of Cu, Ni, and Co compared with the hydrogenous group. XRD analysis shows that well-crystallized todorokite, together with minor birnessite, is present (Figure 3-14). The second group of nodules is 324 Figure 3-12. The relationship between Mn with Cu, Ni, and Co. The open circles = hydrogenous and diagenetic nodules, the filled circles = Mn-enriched hydrothermal nodules, the filled triangles = Mn-depleted hydrothermal nodules. 325 o 1.25 1.00 0.75 + 0.50 + 0.25 + 40.00 1.50 1.00 + 0.50 + 0.00 0.00 40.00 327 Figure 3-13. The XRD patterns of the hydrogenous and diagenetic nodules selected for the two stage selective sequential extraction scheme. B 104 100 co to 03 B 114 330 Figure 3-14. The XRD patterns of the Mn-enriched hydrothermal nodules selected for the two stage selective sequential extraction scheme. CERS 20 D-2 100 co co N) 333 depleted in Mn ( < 10 weight per cent) but are iron- and silica-rich and composed of nontronite (Figure 3-15). This group also has low concentrations of Cu, Ni, Co. 3.4.2 SELECTIVE SEQUENTIAL EXTRACTION AND DXRD 3.4.2.1 Survey Region A In order to better understand the partitioning of Mn, Fe, Cu, Ni, and Co between the manganese and iron oxide phase(s) identified in the crusts and nodules selected from Survey Region A, the results from the two stage selective sequential extraction scheme and the DXRD technique will be considered together. The weight per cent of Mn, Fe, Cu, Ni, and Co in the leachates from the first stage of the selective sequential extraction scheme are listed in Table 3-3a. These results represent the concentrations of Mn, Fe, Cu, Ni, and Co present in the manganese oxides of the crusts and nodules. The mineral phase(s) removed during the first stage of leaching and identified by DXRD are listed in Table 3-3b. The weight per cent of Mn, Fe, Cu, Ni, and Co in the leachates from the second stage of the selective sequential extraction scheme are listed in Table 3-4a. These results represent the concentrations of Mn, Fe, Cu, Ni, and Co present in the iron oxides of the crusts and nodules. The mineral phase(s) removed during the second stage of leaching and identified by DXRD are listed in Table 3-4b. 334 Figure 3-15. The XRD patterns of the Mn-depleted hydrothermal nodules selected for the two stage selective sequential extraction scheme. DWBD 1 -2 CO CO Ul S74 Table 3-3a. The concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the first stage of leaching samples from Survey Region A. Results are listed as weight per cent. Element Samples Hydrogenetic Crusts 7 TOW 7 TOW 130 142 D-Fe 0.23 0.56 Mn 21.79 17.55 Co 0.30 0.55 Ni 0.15 0.21 Cu 0.01 0.01 Element Samples Hydrogenous Nodules Diagenetic Nodules DODO DODO Mn 39 Mn 56 12-2 D-1 14-2 D-2 Fe 1.00 0.74 0.43 0.41 Mn 11.83 11.64 22.04 24.53 Co 0.36 0.33 0.12 0.12 Ni 0.16 0.14 0.56 0.58 Cu 0.04 0.02 0.31 0.42 Table 3-3b. The mineral phase(s) removed during the first stage of the selective sequential extraction scheme and identified by DXRD. Sample Mineral Phase(s) Indentified by DXRD Hydrogenetic Crusts 7TOW 130 D-FRAG 6Mn02 7TOW 142 D-1 6Mn0o Hydrogenous Nodules DODO 12-2 D-1 6MnO-DODO 14-2 D-2 6MnO' Diagenetic Nodules Mn 39 Mn 56 Todorokite/6Mn02 Todorokite/5Mn02 338 Table 3-4a. The concentrations of Mn, Fe, Cu, Ni, and Co in the leachates from the second stage of leaching for samples from Survey Region A. Results are listed as weight per cent. Element Samples Hydrogenetic Crusts 7TOW 7TOW 130 142 D-l Fe 8.79 9.70 Mn 0.83 0.38 Co 0.55 0.10 Ni 0.49 0.09 Cu 0.04 0.06 Element Samples Hydrogenous Nodules Diagenetic Nodules DODO DODO Mn 39 Mn 56 12-2 D-l 14-2 D-2 Fe 8.10 10.00 2.30 1.70 Mn 0.41 0.48 0.44 1.01 Co 0.02 0.02 0.06 0.07 Ni 0.01 0.02 0.41 0.52 Cu 0.05 0.07 0.54 0.52 Table 3-4b. The mineral phase(s) removed during the second stage of the selective sequential extraction scheme and identified by DXRD. Sample Mineral Phase(s) Indentified by DXRD Hydrogenetic Crusts 7TOW 130 D-FRAG Fe r r i h y d r i t e 7TOW 142 D-l Fer r i h y d r i t e Hydrogenous Nodules DODO 12-2 D-l Fe r r i h y d r i t e DODO 14-2 D-2 Fe r r i h y d r i t e Diagenetic Nodules Mn 39 Mn 56 Fer r i h y d r i t e F e r r i h y d r i t e 339 3.4.2.1.1 First Stage of the Selective Sequential Extraction Scheme and DXRD Since the manganese oxides are removed during the first stage of the selective sequential extractiuon scheme, plotting the concentrations of Fe, Cu, Ni, and Co agianst the concentration of Mn will give a better indication of the association of these elements to Mn and the manganese oxide phase(s) in the crust and nodule samples. The results from the first stage of the sequential extraction scheme indictates that the manganese oxides present in hydrogenetic crusts and hydrogenous nodules contain similar concentrations of Cu, Ni, and Co (Figure 3-16). The manganese oxide phase present in hydrogenetic crusts and hydrogenous nodules is 5 M n 0 2 (Figure 3-17, 3-18), which has very low concentrations of Cu and Ni but relatively high concentrations of Co. The 5Mn0 2 in the hydrogenous nodules are found to contain a lower concentration of Mn and a higher concentration of Fe than the 5Mn0 2 in hydrogenetic crusts. The diagenetic nodules are found to contain similar concentations of Fe, consistantly higher concentrations of Mn, Cu, and Ni, and the lowest concentration of Co compared to the hydrogenetic crusts and the hydrogenous nodules. The results from D X R D indictate that todorokite and possibly a minor amount of 5 M n 0 2 is present in the diagenetic nodules and is responsible for these observed compositional trends (Figure 3-19). Figure 3-16. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the manganese phase mineralogy which was removed during the first stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = hydrogenous nodules, the open triangles = diagenetic nodules. 1.00 0.75 + 0.50 + 0.25 0.00 0.00 5.00 10.00 15.00 Mn (%) 20.00 25.00 0.50 0.40 + 0.30 + 0.20 + 0.10 + 0.00 0.00 5.00 10.00 15.00 Mn (%) 20.00 25.00 0.60 0.40 + 0.20 + 0.00 A A $ I-o -1 o -1 0.00 5.00 10.00 15.00 20.00 25.00 Mn {%) . 0.60 0.40 + 0.20 0.00 0.00 5.00 10.00 15.00 20.00 25.00 Mn ( * ) 3 4 3 Figure 3-17. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenetic crusts. 7T0W 130 D-FRAG 100 DEGREES 20 346 Figure 3-18. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenous nodules. DODO 12-2 D-1 100 DEGREES 2© 3 4 9 Figure 3-19. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the diagenetic nodules. 350 INTENSITY (COUNTS/SECOND) Mn 56 CO i-> 352 3.4.2.1.2 Second Stage of the Selective Sequential Extraction Scheme and DXRD Since the iron oxides are removed during the second stage of the selective sequential extraction scheme, plotting the concentrations of Mn, Cu, Ni, and Co against the concentration of Fe will give a better indication of the association of Mn, Cu, Ni, and Co to Fe and the iron oxide phase(s) in the selected crusts and nodules. The results from the second stage of the sequential extraction scheme indicate that the iron oxide present in crust and nodule samples from this region show considerable variations in Fe, Cu, Ni, and Co concentrations (Figure 3-20). DXRD identified the iron oxide present in hydrogenetic crusts, hydrogenous nodules and diagenetic nodules as ferrihydrite which is shown in Figures 3-21, 3-22, and 3-23 respectively. The ferrihydrite present in all three groups of crusts and nodules contains relatively consistent concentrations of Mn, while the ferrihydrite in both hydrogenetic crusts and hydrogenous nodules contains higher concentrations of Fe. In the hydrogenetic crusts, the ferrihydrite has a low concentration of Cu and displays a wide range in Ni and Co concentrations while in the hydrogenous nodules, the ferrihydrite also has a low Cu, Ni, and Co concentrations compared to the hydrogenetic crusts and diagenetic nodules. In the diagenetic nodules, the ferrihydrite contains consistently higher concentrations of Cu and Ni than that present in the hydrogenous nodules and the hydrogenetic crusts but low concentrations of Co similar to the hydrogenous nodules. 353 Figure 3-20. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the iron phase mineralogy which was removed during the second stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = hydrogenous nodules, the open triangles = diagenetic nodules. 1.25 1.00+ A 0.75 + O 0.50 + A O 0.25 + 0.00- -+-0.00 2.00 4.00 6.00 8.00 10.00 Fe {%) 0.60 0.40 + 0.20 + 0.00 0.00 2.00 4.00 6.00 8.00 10.00 Fe (%) 0 . 6 0 0 . 4 0 + 0 . 2 0 + 0 . 0 0 0 . 0 0 2 . 0 0 4 . 0 0 6 .00 8 .00 1 0 . 0 0 Fe (%) 0 . 6 0 0 . 4 0 0 . 2 0 + 0 . 0 0 0 . 0 0 2 . 0 0 4 . 0 0 6 .00 8 .00 1 0 . 0 0 Fe (SK) 356 Figure 3-21. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenetic crusts. 357 o 00 358 INTENSITY (COUNTS/SECOND) o oo 359 Figure 3-22. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenous nodules. 360 INTENSITY (COUNTS/SECOND) o co 362 Figure 3-23. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the diagenetic nodules. CD O (QNO03S/SlNnO0) A1ISN31NI Z9Z v9£ 365 3.4.2.2 Survey Region B In order to better understand the partitioning of Mn, Fe, Cu, Ni, and Co between the manganese and iron oxide phase(s) identified in the crusts and nodules selected from Survey Region B, the results from the two stage selective sequential extraction scheme and the DXRD technique will be considered together. The weight per cent of Mn, Fe, Cu, Ni, and Co in the leachates from the first stage of the selective sequential extraction scheme are listed in Table 3-5a. These results represent the concentrations of Mn, Fe, Cu, Ni, and Co present in the manganese oxides of the crusts and nodules. The mineral phase(s) removed during the first stage of leaching and identified by DXRD are listed in Table 3-5b. The weight per cent of Mn, Fe, Cu, Ni, and Co in the leachates from the second stage of the selective sequential extraction scheme are listed in Table 3-6a. These results represent the concentrations of Mn, Fe, Cu, Ni, and Co present in the iron oxides of the crusts and nodules. The mineral phase(s) removed during the second stage of leaching and identified by DXRD are listed in Table 3-6b. 3.4.2.2.1 First Stage of the Selective Sequential Extraction Scheme and DXRD The results from the first stage of the sequential extraction scheme indicate that the manganese oxides present in the crust and nodule samples from this region show considerable variation in their concentrations of Mn, Fe, Cu, Ni, and Co (Figure 3-24). The manganese oxide phase mineralogy of the hydrogenetic crusts showed the most variation of all the different groups of crusts and nodules selected from this region (Figure 3-25). Despite this the concentrations of Mn, Fe, Cu, and Ni were relatively consistent in the SMnG^, todorokite, and birnessite present. In the Table 3-5a. The concentrations of Mn, Fe, Cu, Ni and Co in the leachates from the first stage of leaching for samples from Survey Region B. Results are listed as weight per cent. Element Samples Hydrogenetic Crusts Mn-rich Hydrothermal Crusts HEN SMT RISE III QBR RISE III 28 D-1 22 D-1 3 D-1 Fe 0.40 0.75 0.05 0.00 Mn 19.24 16.12 22.78 24.65 Co 0.07 0.40 0.00 0.00 Ni 0.21 0.23 0.03 0.02 Cu 0.02 0.00 0.00 0.00 Element Samples Hydrogenous and Mn-rich Fe - r i c h Diagenetic Hydrothermal Hydrothermal Nodules Nodules Nodules B 104 B 114 CERS CERS DWBD S 74 20 D-2 21 D-3 1-2 Fe 0.18 0.15 0.31 0.10 1.21 1.13 Mn 21.29 21.66 23.47 25.40 5.48 4.42 Co 0.03 0.05 0.00 0.00 0.11 0.12 Ni 0.38 0.38 0.09 0.20 0.37 0.20 Cu 0.16 0.20 0.05 0.06 0.12 0.06 Table 3-5b. The mineral phase(s) removed during the first stage of the selective sequential extraction scheme and identified by DXRD. Sample Mineral Phase(s) I n d e n t i f i e d by DXRD Hydrogenetic Crusts Henderson Smt Todorokite/Birnessite RISE III 28 D-l 6Mn02 Mn-rich Hydrothermal Crusts QBR 22 D-l Birnessite/minor amounts of Todorokite RISE III 3 D-l Todorokite/Birnessite Hydrogenous and Diagenetic Nodules B 104 Todorokite/minor amounts of Bir n e s s i t e B 114 Todorokite/minor amounts of Bi r n e s s i t e Mn-rich Hydrothermal Nodules CERS 20 D-2 Todorokite/minor amounts of Bir n e s s i t e CERS 21 D-3 Todorokite/minor amounts of Bir n e s s i t e F e - r i c h Hydrothermal Nodules DWBD 1-2 Todorokite/6Mn0 2 S 74 Todorokite/6Mn0 2 Table 3-6a. The concentrations of Mn, Fe, Cu, Ni and Co in the leachates from the second stage of leaching for samples from Survey Region B. Results are listed as weight per cent. Element Samples Hydrogenetic Crusts HEN SMT RISE III 28 D-1 Fe 1.20 11.40 Mn 0.11 0.52 Co 0.00 0.10 Ni 0.00 0.10 Cu 0.01 0.03 Element Samples Hydrogenous and Diagenetic Nodules B 104 B 114 Fe 4.30 3.20 Mn 1.15 1.58 Co 0.03 0.11 Ni 0.50 0.98 Cu 0.43 0.64 Mn-rich Hydrothermal Crusts QBR RISE III 22 D-1 3 D-1 2. 60 0 .00 9. 29 14 .79 0. 00 0 .00 0. 05 0 .00 0. 02 0 .00 Mn-rich Fe-rich Hydrothermal Hydrothermal Nodules Nodules CERS CERS DWBD S 74 20 D-2 21 D-3 1-2 1.50 0.70 1.50 3.40 , 5.69 8.79 0.04 0.10 0.01 0.00 0.00 0.00 0.47 0.38 0.00 0.00 0.21 0.21 0.03 0.02 Table 3-6b. The mineral phase(s) removed during the second stage of the selective sequential extraction scheme and identified by DXRD. Sample Mineral Phase(s) Indentified by DXRD Hydrogenetic Crusts Henderson Smt Fer r i h y d r i t e RISE III 28 D-l Fer r i h y d r i t e Mn-rich Hydrothermal Crusts QBR 22 D-l Haussmanite RISE III 3 D-l Haussmanite Hydrogenous and Diagenetic Nodules B 104 Fe r r i h y d r i t e B 114 Fer r i h y d r i t e Mn-rich Hydrothermal Nodules CERS 20 D-2 Akaganeite CERS 21 D-3 Haussmanite Fe- r i c h Hydrothermal Nodules DWBD 1-2 Fer r i h y d r i t e S 74 Fe r r i h y d r i t e Figure 3-24. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the manganese phase mineralogy which was removed during the first stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the open triangles = hydrogenous and diagenetic nodules, the filled triangles = Mn-enriched hydrothermal nodules, the open squares = Mn depleted hydrothemal nodules. 1.50 28.00 0.20 0.15 0.10 0.05 0.00 0.00 7.00 14.00 21.00 28.00 Mn (%) 0.40 0.30 0.20 0 .10 + 0.00 • /A O • A i.... • • : — 1 1 0.00 7.00 14.00 Mn (%) 21.00 28.00 0.40 0.30 + 0.20 + 0.10 0.00 0.00 28.00 373 Figure 3-25. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenetic crusts. INTENSITY (COUNTS/SECOND) RISE III 28 D-2 100 DEGREES 20 376 hydrogenetic crusts, the Mn-bearing minerals contained moderate amounts of Fe and Ni and were depleted in Cu. Only Co showed a preferential enrichment in the S M n 0 2 bearing hydrogenetic crust and was depleted in the todorokite/birnessite bearing hydrogenetic crust. In the Mn-rich hydrothermal crusts and nodules, todorokite and birnessite were identified by D X R D (Figure 3-26 and 3-27). Both crusts and nodules were depleted in their concentrations of Fe, Cu, Ni, and Co but were enriched in Mn. It is interesting to note, however, that the Mn-rich hydrothermal nodules did contain slightly higher concentrations of Fe, Cu, and Ni compared to the Mn-rich hydrothermal crusts. In the Fe-rich hydrothermal nodules, todorokite and 5Mn0 2 were identified by D X R D (Figure 3-28) and these samples were found to contain high concentrations of Fe, moderate concentrations of Cu, and Ni, and low concentrations of Mn and Co. In the hydrogenous and diagenetic nodules, todorokite and birnessite were identified by DXRD (Figure 3-29). These phases were found to contain low concentrations of Fe and Co and the highest concentrations of Mn, Cu, and Ni compared to the other samples. 3.4.2.2.2 Second Stage of the Selective Sequential Extraction Scheme and DXRD The results from the second stage of the sequential extraction scheme indicate that the oxyhydroxide phases removed during the the second stage of leaching are relatively depleted in Mn, Fe, Cu, Ni, and Co (Figure 3-30). D X R D results shows that the oxyhydroxide phases were identified as several oxides of iron and one oxide of manganese. Hydrogenetic crusts were found to be contain ferrihydrite (Figure 3-31), while the Mn-rich hydrothermal crusts were found to contain the manganese oxide hausmannite (Figure 3-32). Like the hydrogenetic crusts, the hydrogenous and diagenetic nodules were also found to contain ferrihydrite (Figure 3-33). The two 377 Figure 3-26. The D X R D pattern obtained after the first stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal crusts. QBR 22 D-1 RISE III 3 D-1 3 8 0 Figure 3-27. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal nodules. CERS 20 D-2 100 CO co CERS 21 D-3 383 Figure 3-28. The D X R D pattern obtained after the first stage of leaching of the sequential extraction scheme on the Mn-depleted hydrothermal nodules. DWBD 1-2 DEGREES 20 385 INTENSITY (COUNTS/SECOND) (0 o CM © CM CO LU LU DC CD LU O o CO 0 u W 9 / e ? P I 0 J 0 P 0 l Figure 3-29. The DXRD pattern obtained after the first stage of leaching of the sequential extraction scheme on the hydrogenous and diagenetic nodules. B 104 r- 100 B 114 100 389 Figure 3-30. The weight per cent of Mn, Fe, Cu, Ni, and Co associated with the iron phase mineralogy which was removed during the second stage of the selective extraction scheme. The open circles = hydrogenetic crusts, the filled circles = Mn-enriched hydrothermal crusts, the open triangles = hydrogenous and diagenetic nodules, the filled triangles = Mn-enriched hydrothermal nodules, the open squares = Mn depleted hydrothemal nodules. 390 15.00 A 10.00 c 5.00 + 0.00 0.00 4.00- 8.00 12.00 Fe (SK) 3 o 0.80 0.60 + 0.40 0.20 + 0.00 0.00 4.00 8.00 12.00 Fe (SK) 391 1.00 0.75 + 0.00 4.00 8.00 12.00 Fe (%) o O 0.12 0.00 4.00 8.00 12.00 Fe (%) 3 9 2 Figure 3-31. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenetic crusts. Henderson Seamount 394 3 9 5 Figure 3-32. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal crusts. QBR 22 D-1 DEGREES 20 CO vo RISE III 3 D-1 Hausmannite Hausmannite DEGREES 20 398 Figure 3-33. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the hydrogenous and diagenetic nodules CD O (QNO03S/SlNnO0) A1ISN31NI 66E CD O a m O m m co ro © CD ro o o o o co o o o (QN003S/SlNnOO) A1ISN31NI OOv 4 0 1 groups of hydrothermal nodules displayed the most varied oxyhydroxide phase mineralogy of all the crust and nodule samples from this region. Mn-rich hydrothermal nodules were found to contain hausmannite and akaganeite (Figure 3-34) while the Fe-rich hydrothermal nodules were found to contain ferrihydrite (Figure 3-35). The ferrihydrite identified in the crust and nodule samples shows a considerable variation in composition. In the hydrogenetic crusts, the ferrihydrite is found to have low concentrations of Mn, Cu, and Ni but has a wide range in Fe and Co concentrations, while in the hydrogenous and diagenetic nodules, the ferrihydrite is found to have the highest Cu, Ni, and Co concentrations but low concentrations of Mn and Fe. In the Mn-rich hydrothermal crusts and nodules, hausmannite and akaganeite is found to contain low concentrations of Fe, Cu, Ni, and Co but have the highest concentrations of Mn. It should be pointed out that the hausmannite present in the Mn-rich hydrothermal crusts has consistently higher concentrations of Mn and consistently lower concentrations of Cu, Ni, and Co compared with the hausmannite and akaganeite present in the Mn-rich hydrothermal nodules. 3.5 DISCUSSION 3.5.1 MANGANESE OXIDES IDENTIFIED IN CRUSTS A N D NODULES The marine manganese oxide phases in crusts and nodules are often metastable, intimately intergrown with other materials, and poorly crystalline. The crystallography of manganese oxides found in the marine environment is characterized by numerous structural defects, essential vacancies in the crystal lattice which may or may not be ordered, domain intergrowths, extensive solid solution, and cation exchange properties. These phenomena not only lead to nonstoichiometry 402 Figure 3-34. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the Mn-enriched hydrothermal nodules. 403 INTENSITY (COUNTS/SECOND) o oo (QNOoas/siNnoo) A I I S N B I N I 405 Figure 3-35. The DXRD pattern obtained after the second stage of leaching of the sequential extraction scheme on the Mn-depleted hydrothermal nodules. 406 INTENSITY (COUNTS/SECOND) 408 but detract from internal periodic long-range ordering. This makes crystal structure determination difficult and as a result has led to confusion over classification and nomenclature (Burns & Burns, 1979). Much confusion still exists about the nomenclature and structure of these minerals (Burns & Burns, 1977). Those manganese-bearing minerals that have been identified by DXRD in the crust and nodule samples selected for this study will be described. 3.5.1.1 Todorokite The marine lOA-manganate group was first described by Buser (1959) and was termed "IGA manganite" on the basis of the similarities in X-ray diffraction patterns with synthetic 10A "manganite". The lOA-manganate minerals in deep-sea nodules have also been referred to as todorokite which was originally reported from a non-marine environment (Yoshimura, 1934). This dual nomenclature pervaded the literature during the 1960's (Burns & Burns, 1977) despite the complaints by Burns & Fuerstenau (1966) that the term "10A manganite" led to confusion with the mineral manganite (-yMn3+OOH). Turner & Buseck (1981) showed by lattice images, obtained by high resolution transmission electron microscopy (HRTEM), that known todorokites from terrestrial deposits have well-ordered tunnel structures. The tunnel widths vary randomly between three and seven octahedral units. Turner et al. (1982) and Siegel & Turner (1983) then reported the same type of tunnel structure in a 10A-manganate from a marine ferromanganese nodule. Todorokite is a tecktomanganate possessing a tunnel structure running parallel to the b-axis. The tunnels are composed of Vails" of triple chains of edge-shared [MnOg] octahedra containing M n 4 + ions in the M l positions and M n 2 + in the M2 positions. "Floors" and "ceilings" of these tunnels consist of edge-shared [MnOg] octahedra, most commonly three octahedra wide with Mn + ions in the M3 and M4 positions (Figure 3-36) (Burns et al, 1983). These predominant [3x3] tunnels are often intergrown with other tunnels ranging in dimensions from [3x2] to [3x8] and higher (Burns et al, 1985). The very wide tunnels, obtaining dimensions of [3x8] and higher, tend towards the [3x oo] layered structure postulated for buserite (Burns et al., 1983). In the "ceilings" of the todorokite tunnels are cation vacancies within the bands of edge-shared [Mn^+Og] octahedra which become more prevalent with wider "ceiling" dimensions. These cation vacancies not only nucleate faults, kinks, and twinning observed in the HRTEM micrographs of todorokite fibers (Turner et al., 1982), but they also influence the crystal chemistry and site occupancy of the tunnels. As a result, three types of atomic substitution contribute to the crystal chemistry of todorokite. First, substitution of Mn^ + cations by anions of smaller ionic radii in the "ceilings" such as low spin Co^ + ions (Burns, 1976). Secondly, substitution of divalent Mn^ + ions in the "walls" by Mg^ + , Ni^ + , Cu^ + , Zn^ + , and other cations. Third, constituents of the tunnels (Tl and T2 positions) consist of large cations such as K + , Ba^ +, A g + , Ca^ + , Pb^+, Na + , and molecules (Burns et al, 1983). 3.5.1.2 Birnessite Another manganese oxide phase found in marine manganese crusts and nodules is birnessite. This manganese-bearing mineral phase is commonly confused with phillipsite and clay mineral groups, by X-ray diffraction, because all have d-spacings around 7A (Burns & Burns, 1979). It has been postulated that birnessite is a phyllomanganate similar in structure to the phyllomangnaate buserite (Chukhrov et al, 1987). Birnessite is a double-layered compound consisting of sheets of water molecules and hydroxyl groups Figure 3-36. The crystal structure of todorokite (Turner et al, 1982). 411 O • Manganese O • Oxygen Tunnel cations or water molecules located between layers of edge-shared [MnOg] octahedra separated by about 7A along the c-axis. One out of every six octahedral sites in the layer of the linked [MnOg] octahedra is unoccupied and Mn ions are considered to lie above and below these vacancies. These low valence manganese ions are coordinated to oxygens in both the [Mn0 6] layer and the (H 2 0 , OH") sheet (Figure 3-37) (Burns & Burns, 1977). Birnessite formation will occur in areas where the local conditions are moderately oxidizing and the supply of 10A stabilizing cations is low. Toth (1980) proposed that well-crystallized birnessite would be observed in hydrothermal crusts and nodules because of the low concentrations of Co, Ni, Cu, Pb, and Ba relative to Fe and Mn in the hydrothermal solutions and because of the rapid deposition of these deposits which minimizes adsorption of elements from sea-water. Birnessite has been identified in hydrothermal crusts and nodules studied by Toth (1980) Lonsdale et al. (1980) and in the DXRD patterns obtained after the first stage of leaching on the hydrothermal crusts and nodules examined in this study. 3.5.1.3 5MnQ 2 Under strongly oxidizing conditions, like those found on exposed rock surfaces in the ocean, the M n 2 + no longer exists in the M n 2 + ( O H ) 2 x 2 H 2 0 layers to bind successive [Mn 4 + 0^] layers together as it does in todorokite and birnessite; instead, the layers of linked [Mn 4 + Og] octahedra are randomly oriented and constitute the 5Mn0 2 phase which does not give basal X-ray reflections (Figure 3-38) (Burns & Burns, 1979). Furthermore, it has been suggested that the poorly crystalline S M n 0 2 and not the more ordered birnessite plays an essential role in the nucleation and authigenesis of nodules through its ability to form epitaxial intergrowths with an isostructural iron (III) oxyhydroxide phase (FeOOHxnH 2 0) (Burns & Burns, 1975). Figure 3-37. The crystal structure of birnessite (Giovanoli & Brutsch, 1979). 414 415 Figure 3-38. The crystal structure of 5MnC«2 (modified from Giovanoli et al, 1965). 416 417 Burns & Burns (1977) regarded 8Mn0 2 to be structurally-disordered birnessite. Since 8Mn0 2 is characterized by a very high specific surface area and by significant Co concentrations, SMn0 2 is regarded as a separate Mn-bearing mineral phase in the marine environment (Burns & Burns, 1979). The 8Mn0 2 identified in the D X R D patterns obtained after the first stage of leaching on the crust and nodule samples in the present study contained the highest concentrations of Co compared to the concentrations of this element measured in the other Mn phase mineralogy (todorkite, birnessite, and hausmannite) and the Fe phase mineralogy (akaganeite and ferrihydrite) which was identified by DXRD. 3.5.1.4 Hausmannite The crystal structure of hausmannite is defined as a distorted spinel structure (Bricker, 1965; Giovanoli, 1985). The spinel crystal structure is characterized by a unit cell which is face-centred cubic and contains 32 oxygen ions, which forms a nearly cubic close-packed framework as viewed along the cubic diagonals [111] and manganese cations which occupy some of the intersticies within the oxygen framework (Figure 3-39). By convention, there is a set of compatible tetrahedral and octahedral sites which divalent and trivalent manganese cations can occupy. These are defined as 16d (octahedral) and 8a (tetrahedral) vacancies. In a distorted spinel structure, 1/9 of the metal cation sites of the spinel structure are vacant. These vacant sites are distributed in one of two ways, either randomly distributed throughout the tetrahedral (8a) and octahedral (16d) sites or confined only to the octahedral (16d) sites. The crystal structure is not exactly that of a spinel structure because the vacancies are ordered along a particular [100] axis, the repeat distance being three times the cubic cell edge. The crystal structure is, therefore, tetragonal due to the vacancy superlattice. Figure 3-39. The crystal structure of hausmannite (Murray, 1979). 420 Hausmannite has never been identified in marine manganese nodules (Burns & Burns, 1977; Murray & Dillard, 1979). von Heimendahl et al. (1976) did, however, identify hydrohausmannite in a nodule from the eastern equatorial Pacific. Evidence for the possible origin of hausmannite in marine manganese crusts and nodules is provided by the experimental work of Bricker (1965). Bricker (1965) was able to form synthetic hausmannite at 25°C and one atmospheric pressure. It was found that with the proper control of Eh and pH hausmannite could be preserved indefinitely. Suitable Eh and pH values were 0.5 and 6.5, respectively. Except for the low pH, the laboratory solutions were similar in temperature, acidity, and redox potential to fluids in bottom sediments in an open circulation marine environment (Krumbein & Garrels, 1952). Given this evidence, hausmannite could indeed form on the sea floor, given the requisite chemical constituents (Sorem & Gunn, 1967). 3.5.2 IRON OXIDES IDENTIFIED IN CRUSTS AND NODULES The iron-bearing phases in crusts and nodules have usually been described as being cryptocrystalline or amorphous hydrated iron oxides (Glasby, 1972; Crerar & Barns, 1974). Mossbauer spectroscopic studies by Herzenberg & Riley (1969), Gager (1968), Johnson & Glasby (1969), and Carpenter & Wakeman (1973) have also led to the suggestion that the iron-bearing phase can be regarded as an amorphous ferric hydroxide or oxide-hydroxide gel ( F e O O H x ^ O ) with a particle size less than 200A. Various authors have reported several crystalline iron-bearing phases in crusts and nodules. These phases are: goethite (Buser, 1959), akaganeite (Johnston & Glasby, 1978), lepidocrocite (Glasby, 1972), feroxyhyte (Chukhrov et al., 1976), maghemite (von Heimendahl et al., 1976), and ferrihydrite (Murad & Schwertmann, 1988). 421 The lack of any definitive understanding of the iron phase mineralogy of crusts and nodules stems from two factors: (1) the fine grain size (cryptocrystallinity) of the iron oxide/oxyhydroxide minerals; and (2) the fact that the iron is present in the octahedrally coordinated, high spin ferric state. As a result of the fine grain size, X-ray diffraction patterns have rarely been recorded for these mineral phases. Because of the symmetry of the d^ electron shell in the ferric ion, it has not yet proved possible to identify definitively the major ferric oxide/oxyhydroxide minerals present in crusts and nodules using mossbauer spectroscopy. The mineralogy and crystallography of the iron-bearing minerals that have been identified in crusts and nodules has been reviewed by Burns & Burns (1977) and by Murray (1979). Those iron-bearing minerals that have been identified by D X R D in the crust and nodule samples selected for this study will be described. 3.5.2.1 Akaganeite Akaganeite ( /3FeOOH) is characterized by tunnels that run parallel to the c-axis. In many respects akaganeite is similar in structure to the manganese mineral todorokite (Burn & Burn, 1979). [FeO^] octahedra share edges and form double chains along the c-axis. The octahedra of the double chains share corners with adjacent double chains to form a three-dimentional framework with a body-centred trigonal unit cell (Figure 3-40). The tunnels accommodate H 2 O , and OH", CI", F~, S 0 4 ^ - , and N 0 3 " ions. These large ions (especially CI") are essential for the formation of this tunnelled structure (Ellis et al., 1976). The first reported occurrence of akaganeite in marine nodules was by Goncharov et al. (1973). The presence of this mineral in marine nodules was discounted by Burns & Burns (1977). Since then the presence of akaganeite in 422 Figure 3-40. The crystal structure of akaganeite. 1 = Mn, 2 = oxygen, 3 = Ba, K, Pb, Na, or H 2 0 (Murray, 1979). 423 • o 424 marine crusts and nodules has been reported by Johnston & Glasby (1978), Thijs et al. (1981), and in one Mn-rich hydrothermal crust in this study. 3.5.2.2 Ferrihydrite The name ferrihydrite was first proposed for the mineral of composition 5Fe2C»3-9H20 by Chukhrov et al. (1973). The name was later accepted by the International Mineralogical Association. Eggleton & Fitzpatrick (1988) proposed that the ferrihydrite structure is based on the double-hexagonal close-packing of oxygens in an ABAC sequence. Two sheets of octahedrally coordinated iron are connected by two sheets of mixed tetrahedral and octahedral iron in the ratio 5 tetrahedral: 2 octahedral. This arrangement is similar to that of the spinels. Along the 3-fold axes of spinel, planes of oxygens in cubic close packing alternately host all octahedral iron or mixed tetrahedral and octahedral iron (Figure 3-41). Eggleton & Fitzpatrick (1988) observed the probable presence of tetrahedrally coordinated Fe^ + in ferrihydrite and hypothesized that tetrahedral Si may substitute for the tetrahedral Fe^ + . Vempati et al. (in press) provided further evidence, through photoelectron spectroscopy, that tetrahedrally coordinated F e ^ + does exist in ferrihydrite and of tetrahedrally coordinated Si in Si-containing ferrihydrite having Si/Fe molar ratios greater than 0.10. Vempati & Loeppert (1989) studied the effect of structrual and adsorbed Si in prohibiting synthetic ferrihydrite to transform into goethite and/or hemitite. They noted that synthetic ferrihydrite with Si/Fe molar ratios greater than 0.10 did not transform to geothtite and/or hemitite. They concluded that in natural systems ferrihydrite containing adsorbed and/or coprecipitated silicate is probably influenced by the Si concentration, mechanism of silicate bonding, pH, and temperature. Siliceous ferrihydrite (Si/Fe molar ratios > 0.10), formed during the coprecipitation of Fe oxides with silicate, would probably be 425 Figure 3-41. The crystal structure of ferrihydrite (modified from Eggleton & Fitzpatrick, 1988). TETRAHEDRA OCTAHEDRA 4 2 7 stable for extended periods of time at pH > 7, even at elevated temperatures. This evidence supports the fact that the ferrihydrite identified in the DXRD patterns obtained after the second stage of leaching on the crusts and nodule samples in the present study is an authentic iron oxide and not an artifact caused by the chemical leaching. 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Origin and classification of chemical sediments in terms of pH and oxidation-reduction potential. Jour. Geol., 60:1-33. Lonsdale, P., Burns, V.M., & Fisk, M., 1980. Nodules of hydrothermal birnessite in the caldera of a young seamount. Journ. Geol., 88:611-618. Lyle, M., 1981. Formation and growth of ferromanganese oxides on the Nazca plate. Geol. Soc. of Amer. Mem., 154, pp. 269-293. Murad, E., & Schwertmann, U., 1988. Iron oxide mineralogy of some deep-sea ferromanganese crusts. American Mineralogist, 73:1395-1400. Murray, J.W., 1979. Iron Oxides. In Mineralogical Society of America Short Course Notes, Marine Minerals (ed. by R.G. Burns), Vol. 6. LithoCrafters Inc., Chelsea, Michigan, pp. 47-98. Murray, J.W., & Dillard, J.G., 1979. The oxidation of cobalt (II) adsorbed on manganese dioxide. Geochim. Cosmochim. Acta, 43:781-787. Price, N.B., & Calvert, S.E., 1970. Compositional variation in Pacific Ocean ferromanganese nodules and its relationship to sediment accumulation rates. Mar. Geol., 9:145-171. Siegel, M.D., & Turner, S., 1983. Crystalline todorokite association with biogenic debris in manganese nodules. Science, 219:172-174. Sorem, R.K., & Gunn, D.W., 1967. Mineralogy of manganese deposits, Olympic Peninsula, Washington. Econ. Geol., 62:22-56. Thijs, A., De Roy, G., Vansant, E.F., Glasby, G.P., & Thijssen, T., 1981. Mossbauer effect studies of iron in manganese nodules and associated marine sediments in five areas in the equatorial and S.W. Pacific. Geochem. Jour., 15:25-37. 431 Toth, J.R., 1980. Deposition of submarine crusts rich in manganese and iron. Geol. Soc. of Amer. Bull., Part 1,91:44-54. Turner, S., & Buseck, P.R., 1981. Todorokite: A new family of naturally occurring manganese oxides. Science, 212(29):1624-1626. Turner, S., Siegel, M.D., & Buseck, P.R., 1982. Structural features of todorokite intergrowths in manganese nodules. Nature, 296:841-842. Usui, A., & Mita, N., 1987. Comparison of manganese nodules from the northeast equatorial Pacific (cruise SO 25) with nodules from the central Pacific basin. Geol. Jb., D87:287-313. Vempati, R.K., Loeppert, R.H., 1989. Influence of structural and adsorbed Si on the transformation of synthetic ferrihydrite. Clays and Clay Minerals, 37(3):273-279. Vempati, R.K., Loeppert, R.H., & Cocke, D.L., in press. Mineralogy and reactivity of Si-ferrihydrite. Solid State Ionics. von Heimandahl, M., Hubred, G.L., Fuerstenau, D.W., & Thomas, G., 1976. A transmission electron microscope study of deep-sea manganese nodules. Deep-Sea Research, 23:69-79. Yoshimura, T., 1934. Todorokite, a new manganese mineral from the Todoroki Mine, Hokkaido, Japan. J. Fac. Sci., Hokkaido Univ. Sapporo, Ser. 4, 2:289-297. CHAPTER 4 SUMMARY OF PRINCIPAL RESULTS 433 4.1 RESULTS F R O M CHAPTER 1 4.1.1 REGIONAL VARIATIONS IN T H E GEOCHEMISTRY OF CRUSTS AND NODULES 4.1.1.1 Survey Region A Using the elemental ratio of Mn/Fe, the association of the major elements with either of the major oxide phases in the crusts from Survey Region A became more apparent. Elements correlated with the manganese phase mineralogy show a positive linear correlation with the Mn/Fe ratio. In the present case, these include Ba, Ni, Zn, and Co. Elements associated with the unidentified iron phase mineralogy show a negative correlation with the Mn/Fe ratio; these elements include Ti and Na. Hein et al. (in press a) identified the same correlations in crusts from the central Pacific. They noted however that the degree of the correlations vary from area to area. Crusts derive most of their metal content from dissolved and particulate matter in ambient bottom water, in proportions modified by the variable scavenging efficiency of the manganese and iron oxide phase mineralogy for susceptible ions (Manheim & Lane-Bostwick, 1988). This model is supported by the striking resemblance between the crust/seawater trace metal enrichment sequence and laboratory determined oxide-trace metal selectivity sequences (Aplin & Cronan, 1985). Cobalt along with Ba, Ni, and Zn are fixed by lattice substitution for M n ^ + in the M n 0 2 or by coprecipitation of C o 0 2 with manganese oxide (Hem, 1978). The reason that Co is enriched in 5Mn0 2 to a greater degree than are Ni, Zn, and Ba is because C o ^ + is oxidized to C o ^ + on the surface of the M n 0 2 . Cobalt (III) is less 434 soluble and therefore more stable in the marine environment (Goldberg, 1954; Dillard et al, 1982; Halbach et al, 1983; Aplin & Cronan, 1985). Not only does there exist interelement associations in crusts from this region, but for crusts from the Hawaiian Archipelago there also exists a correlation between the major element contents and water depth. Manganese and those minor metals that are correlated with manganese (Zn, Ba, Co, Ni, and Cu) all show a decrease in concentration with increasing water depth, while those elements that show a correlation with iron (Na, and Ti) all show an increase in concentration with increasing water depth. To understand the correlation between crust geochemistry and water depth, the source of constituent elements must be identified. Halbach & Puteanus (1984) have proposed that the main Fe source for hydrogenetic crusts of this region is colloidal Fe-hydroxide particles that are released in the water column from the dissolution of carbonate plankton skeletons. On the other hand, the source of Mn to hydrogenetic crusts evidently cannot be derived soley from this same source. They concluded that a further source of Mn enrichment following carbonate dissolution is necessary, and this is supplied via the Oxygen Minimum Zone (OMZ). The extent of the OMZ in the central equatorial Pacific lies at water depths of between 503 and 2296m, and the minimum dissolved oxygen concentration is 26/imole/kg. Within the O M Z there is a high concentration of dissolved Mn as a result of the in situ decomposition of organic matter along with the in situ reduction of Mn-bearing solid phases (Klinkhammer & Bender, 1980; Landing & Bruland, 1980). This zone of maximum concentration of M n ^ + produces a flux of M n ^ + by diffusion and turbulent mixing into shallower and deeper waters which have an increased oxygen content. This causes oxidation of the M n ^ + and results in the formation of hydrated M n 0 2 particles which are incorporated into the crusts (Halbach et al, 1988). As noted by Halbach et al (1983), an increasing supply of Fe 435 and its associated trace metals from the dissolution of calcite skeletons has a diluting effect on the concentration of Mn and its associated trace metals, that is the concentration of Mn and its associated trace metals should decrease with increasing water depth down to the CCD. This trend has also been observed by Halbach et al. (1983), Aplin & Cronan, (1985), and by Hein et al. (in press b). Although 5Mn02 is the most common manganese mineral present, todorokite also occurs in low abundances. The relative abundances of todorokite and SMnC>2 in crusts from this region also appear to show a variation with water depth. Todorokite is more abundant in crusts located within the OMZ. As discussed by Glasby (1972), the redox potential in the environment of formation of ferromanganese deposits controls the manganese phase mineralogy. The depletion of oxygen in the OMZ to values of around 26/imole/kg results in an environment with a lower redox potential. These lower redox potentials combined with the high M n ^ + concentrations will result in manganese oxyhydroxides being precipitated as todorokite, where the Mn^ +(0H)2X2H20 layers bind sucessive [Mn^+0^] octahedra together. Below the OMZ, oxygen is more plentiful, this results in higher redox potentials, and combined with the low concentration of M n ^ + the layers of linked [Mn^+Og] octahedra are randomly oriented and constitute the 5Mn02 phase (Burns & Burns, 1979). Although there appears to be a general correlation between crust geochemistry and water depth for crusts from the Hawaiian Archipelago, crusts from the Line Island Archipelago show a very wide range in composition over a very small range in water depth. This variability is related to location; the concentrations of Mn, Ni, Zn, Cu, Co, and Ba decrease from the Equator towards the northwest along the Line Island Archipelago, while the concentrations of Fe, Ti, and Na increase with distance away from the Equator in the same direction. 4 3 6 This variation in the regional geochemistry of crusts from the Line Island Archipelago has also been observed by Halbach et al. (1982) and by Halbach & Puteanus (1984). They proposed that although this correlation is not well understood, the processes likely to control these regional trends include deep and intermediate-depth current systems, biological productivity, differences in the position of the CCD, and the degree of depletion of oxygen in and the vertical extent of the O M Z zone. Although not the first, Halbach & Ozkara (1979) used the Mn/Fe ratio as a criterion for distinguishing between different types of nodules. They suggested that nodules with an Mn/Fe ratio less than 2.5 were predominantly hydrogenous in origin, while nodules with an Mn/Fe ratio above 2.5 were mainly diagenetic in origin. Nodules from Survey Region A can also be divided into these two groups, and there is a marked compositional distinction between them. Hydrogenous nodules are depleted in Mn, Cu, Ni, Zn, Mg, and Ba compared to the diagenetic nodules whereas hydrogenous nodules are enriched in Fe and Ti compared to the diagenetic nodules. It can therefore be stated that the abundances of Cu, Ni, Zn, Mg, and Ba are correlated with Mn and that the abundance of Ti is correlated with Fe. Apart from Co and Zn, there is a non-linear correlation between those elements that are associated with Mn. The slope of the regression line for the hydrogenous nodules is greater than that of the diagenetic nodules. A non-linear correlation between Ni and Cu versus the Mn/Fe ratio has also been observed by Halbach et al. (1981b) in nodules from the Northeast Pacific nodule belt and by Usui & Mita (1987) in nodules from the three survey areas of SONNE Cruise SO-25 in the Northeast equatorial Pacific. Halbach et al. (1981b) concluded that their non-linear regressions describe the natural saturation of divalent cations in the lattice of todorokite. The decrease in the slope of the first order regression lines from the hydrogenous nodules to the diagenetic nodules recovered from Survey Region A can therefore be attributed to the saturation of the todorokite crystal lattice by manganese and associated divalent cations. The relationship between Zn and Mn/Fe does not show the same behaviour as the other elements associated with manganese. The reason for this is probably because of the low concentration of zinc in the nodules from this region compared to the other elements. Zinc, therefore, does not become saturated in the todorokite lattice structure. The Cu/Ni ratio shows a strong positive correlation with the Mn/Fe ratio. Hydrogenous nodules are found to have generally lower Cu/Ni ratios when compared to diagenetic nodules. This relationship has also been observed by Raab (1972), Calvert & Price (1977), and Calvert et al. (1978). The reason for this correlation can be explained by examining the behaviour of Cu and Ni during diagenesis. Work on the trace metal geochemisty of pelagic sediment pore waters by Klinkhammer (1980), Callender & Bowser (1980), and by Klinkhammer et al. (1982) has shown that Cu and Ni behave quite differently during diagenesis in marine sediments. During diagenesis, Ni follows Mn, apparently being taken up by solid Mn phases close to the sediment surface and is released to the pore water along with Mn at depth. In contrast, Cu is released to the pore water very close to the sediment surface were it can diffuse both into the bottom water and into the sediment. These different behaviours are consistent with the Cu-enrichment in the most markedly diagenetic nodules at Survey Region A. It has already been shown that the abundance of Ti is correlated with the presence of Fe. When Ti is plotted against Mn/Fe there is a sharp break in the slope of the first order regression line drawn through the hydrogenous nodules compared to one drawn through the diagenetic nodules, the slope for the hydrogenous nodules being greater than that for the diagenetic nodules. Since Ti is correlated with Fe, this change in the slope of the first order regression lines is the inverse of that displayed by those elements (except Co and Zn) that correlate with Mn. Just like the 4 3 8 saturation of the todorokite crystal lattice with Mn and its associated divalent cations, the change in the slopes of the first order regression lines from the hydrogenous nodules to the diagenetic nodules can be interpreted as the saturation of the crystal lattice of the unidentified iron oxyhydroxide with Ti. Cobalt shows a complex association with Mn and Fe, which is unlike that of the other minor elements. In hydrogenous nodules, Co is positively correlated with Mn, whereas in diagenetic nodules Co is positively correlated with Fe. The complex association of Co with the manganese and iron oxide phases have been previously observed by Cronan & Tooms (1969), Price & Calvert (1970) and by Halbach et al. (1983). Price & Calvert (1970) suggested that this observed complex behaviour of Co in nodules is due to C o 3 + substituting for M n 4 + in nodules condaining SMn0 2 as well as F e 3 + in the iron oxyhydroxide phases. Cobalt (III) (d )^ is stable when in the low spin state with octahedral coordination and has an ionic radius almost identical to that of F e 3 + or M n 4 + . Cobalt (III) will therefore preferentially substitute for both F e 3 + in the FeOOHxnH 2 0 phase (Burns, 1965) and M n 4 + in the 5 M n 0 2 phase (Glasby & Thijessen, 1982; Halbach et al., 1981a). As noted previously, C o 3 + will also substitute for M n 4 + in the "ceilings" of todorokite (Burns, 1976). Since hydrogenous nodules contain both 5Mn0 2 and todorokite, this would explain the positive association of Co with Mn. Diagenetic nodules, on the other hand, contain mostly todorokite. Although the substitution of C o 3 + for M n 4 + in the "ceilings" of todorokite probably occurs, the substitution of C o 3 + for F e 3 + in the F e O O H x n H 2 0 phase appears to be more dominant as seen by the correlation of Co with Fe in these nodules. 439 4.1.1.2 Survey Region B Two groups of crusts with distinct end-member compositions and mineralogy were identified in the crusts from Survey Region B. One group of crusts was found to be enriched in Mn and depleted in Fe and Si. The Mn-rich mineral phase was identified to be todorokite and birnessite. The second group of crusts was found to be enriched in Fe and Si and depleted in Mn. The Fe-Si rich mineral phase was identified as amorphous hydrated iron oxides and silica. Both groups of hydrothermal crusts were depleted in Co, Cu, and Ni. Because of the different geochemical behaviours of Fe and Mn, fractionation of the two elements is common in hydrothermal solutions (Lyle, 1981). This results in the formation of two distinct end member deposits: (1) Manganese-rich well-crystallized birnessite and todorokite crusts with generally very low trace metal content, and (2) Iron- and silica-rich crusts composed of iron-rich nontronite or amorphous hydrated iron oxides and silica, also with very low trace metal contents. The fractionation of Fe and Mn occurs as a result of the lower solubility of iron species as both Fe and Mn undergo oxidation (Krauskopf, 1957) by mixing of the reduced hydrothermal fluid with oxygenated bottom water. The association of Si with Fe may result from coprecipitation or adsorption of dissolved Si02 onto hydrated iron-oxide colloids during this process. The low content of minor elements in these deposits results from: (1) the low concentrations of these elements relative to Fe and Mn in hydrothermal solutions, and (2) the rapid deposition of the deposits which minimizes adsorption of elements from seawater (Toth, 1980). Unlike crusts, nodules do not form by the direct precipitation of hydrothermal fluids; however, two groups of nodules from Survey Region B showed identical trends in composition and mineralogy to those shown by the two groups of hydrothermal crusts. One group of hydrothermal nodules was found to be enriched 440 in Mn and depleted in Fe and Si. The Mn-rich mineral phase was identified as todorokite and birnessite. The second group of hydrothermal nodules was found to be enriched in Fe and Si and depleted in Mn. The Fe-Si rich mineral phase was identified as iron-rich nontronite. Both groups of hydrothermal nodules were depleted in Co, Cu, and Ni. The two types of hydrothermal nodules with these distinct end-member compositions and mineralogies have also been identified by Dymond et al. (1984) and by Chen & Owen (1989) in nodules from the eastern equatorial Pacific. Dymond et al. (1984) proposed that the chemical composition of nodules from the three MANOP sites can be accounted for in a qualitative way by variable contributions of distinct accretionary processes. They proposed that these accretionary modes are: (1) hydrogenous, the direct precipitation or accumulation of colloidal metal oxides from seawater; (2) oxic diagenesis, the variety of ferromanganese accretion processes occurring in oxic sediments; and (3) suboxic diagenesis, the redultion of M n 4 + by oxidation of organic matter in the sediments. They concluded that processes (1) and (2) occurred at all three MANOP sites and process (3) occurs only at site H, the hemipelagic site. Chen & Owen (1989) used these results to interpret the factor analysis of geochemical data from nodules representing a broad area of the southeast Pacific Ocean. They concluded that nodule compositions are controlled by four processes. Three of the four processes are discussed by Dymond et al. (1984) while the fourth process is hydrothermal precipitation. Chen & Owen (1989) identified hydrothermal nodules as those enriched in Fe but depleted in Mn, Co, Cu, and Ni. These are the same criteria used by Toth (1980) and correspond with the Fe-Si rich hydrothermal crusts and nodules identified in Survey Region B in this thesis. Both Dymond et al. (1984) and Chen & Owen (1989), however, misidentified the Mn-rich hydrothermal nodules. Dymond et al. (1984) stated that suboxic diagenesis results in the accretion of material which is Mn-rich but 441 depleted in other transition metals. They further stated that suboxic diagenesis results in an unstable todorokite that transforms to a 7A phase (birnessite) upon dehydration. From their limited growth rate data for nodules from MANOP site H, they also concluded that suboxic accretion is the fastest of the three processes with rates of at least 200mm/10^yr. The compositions of the suboxic diagenetic nodules described by Dymond et al. (1984) and by Chen & Owen (1989) are identical in composition and mineralogy to both the Mn-rich hydrothermal crusts and nodules from Survey Region B and the Mn-rich crusts studied by Toth (1980). Although no growth rates have been determined for nodules that have been identified as being hydrothermal, rapid growth rates of greater than lOOmm/Myr for hydrothermal crusts located near the EPR have been proposed by Manheim & Lane-Bostwick (1988), Toth (1980), and Moore & Vogt (1976). The composition of the nodules from Survey Region B also indicates that there is a negative correlation between the concentration of Co in nodules from Survey Region B and their proximity to the hydrothermal discharge from the EPR. As proposed by Manheim & Lane-Bostwick (1988), the depletion of Co in Pacific crusts corresponds to the location and intensity of submarine hydrothermal discharge. They found that Co-enriched crusts are found where water masses are most isolated from hydrothermal activity. In contrast, cobalt-depleted crusts coincide with known areas of hydrothermal activity. This same association between the depletion of Co and the location and intensity of hydrothermal discharge seems to apply to the nodules recovered from Survey Region B. Those nodules that are located close to the EPR in water depths of about 3000m and have Co concentrations below 0.05 weight per cent. Those nodules located farthest away from the EPR in deeper water are enriched in Co ( > 0.20 weight per cent). This is the first time that the depletion of Co due to the hydrothermal influence of the EPR 442 has been noted in oceanic ferromanganese nodules from the Eastern Equatorial Pacific. 4.2 RESULTS FROM CHAPTER 2 4.2.1 SELECTIVE SEQUENTIAL EXTRACTION SCHEME A two stage selective sequential extraction scheme was developed to first remove the manganese then the iron phase mineralogy in marine crusts and nodules. For the first stage of the selective sequential extraction scheme, one gram of sample and 83mL of reagent were sequentially measured into an acid washed 125mL Nalgene® polyethylene bottle and capped. The sample was then placed onto an orbital shaker set at 85rpm and allowed to equilibrate for eight hours, after which the residue and leachate were separated by centrifugation for 20min at 3000rpm. The leachate was decanted into a lOOmL volumetric flask and the residue was washed three times with 0.1M NH2OH-HCl in 0.01M H N O 3 and centrifuged again for 20min at 3000rpm. Each wash was combined with the leachate, made up to volume with 0.1M NH 2OH-HCl in 0.01M H N O 3 and stored in an acid washed 125mL Nalgene® polyethylene bottle. The residue was washed three times with distilled deionized water, centrifuged for 20min at 3000rpm and freeze dried. Depending on how much residue remained after the first stage of the extraction scheme, an appropriate amount of 0.175M Ammonium Oxalate in 0.1M Oxalic Acid was added to the residue in the plastic bottle to maintain a sample to solution ratio of 1:250 for the second stage of the selective sequential extraction scheme. The capped bottle was then shaken at 85rpm for eight hours in the dark. The residue was then separated from the leachate using the methods decribed above. T h e c o n c e n t r a t i o n s o f M n , F e , C u , N i , a n d C o i n t h e l e a c h a t e s w e r e d e t e r m i n e d b y a t o m i c a d s o r p t i o n s p e c t o m e t r y u s i n g a P e r k i n - E l m e r 560® s p e c t r o m e t e r . T h e c o n c e n t r a t i o n s o f M n , F e , C u , N i , a n d C o i n t h e l e a c h a t e was t h e n d e t e r m i n e d by p l o t t i n g t h e i r m e a s u r e d a b s o r b a n c e v a l u e s o n t o t h e c a l i b r a t i o n c u r v e s . S o m e p a r t i t i o n i n g o f M n , Fe , C u , N i , a n d C o i n t h e l a b o r a t o r y s t a n d a r d c r u s t a n d n o d u l e is e v i d e n t f r o m t h e r e s u l t s o f the s e l e c t i v e s e q u e n t i a l e x t r a c t i o n scheme. F o r b o t h t h e l a b o r a t o r y s t a n d a r d c r u s t a n d n o d u l e , the l e a c h a t e s f r o m t h e f i r s t stage o f l e a c h i n g b o t h c o n t a i n a l a r g e c o n c e n t r a t i o n o f M n , w i t h o n l y m i n o r a m o u n t s o f F e , w h i l e t h e l e a c h a t e s f r o m the s e c o n d stage o f l e a c h i n g c o n t a i n a h i g h e r c o n c e n t r a t i o n o f F e w i t h o n l y m i n o r a m o u n t s o f M n . T h e b e h a v i o u r o f C u , N i , a n d C o i n t h e l e a c h a t e s f r o m the t w o stages o f the e x t r a c t i o n s c h e m e a r e d i s t i n c t i v e l y d i f f e r e n t f o r the l a b o r a t o r y s t a n d a r d c r u s t a n d n o d u l e . F o r t h e crust, t h e l e a c h a t e s f r o m t h e f i r s t s tage c o n t a i n h i g h e r c o n c e n t r a t i o n s o f N i a n d C o w h e n c o m p a r e d t o t h e l e a c h a t e s f r o m t h e s e c o n d stage, w h e r e a s C u is h i g h e r i n t h e s e c o n d stage l e a c h a t e s . F o r t h e t h e n o d u l e , t h e l e a c h a t e f r o m the f i r s t stage c o n t a i n s a h i g h e r c o n c e n t r a t i o n o f C u w h e n c o m p a r e d to t h e l e a c h a t e f r o m t h e s e c o n d stage. T h e s a m e is o b s e r v e d f o r N i e x c e p t n o t t o the s a m e extreme. F o r C o , h o w e v e r , e q u a l a m o u n t s o f C o a r e e x t r a c t e d f r o m b o t h t h e f i r s t a n d s e c o n d stage o f l e a c h i n g . T h e s a m p l e p r e c i s i o n f o r t h e f i r s t stage o f l e a c h i n g w a s f o u n d t o v a r y f r o m 0 . 0 0 % ( C u a n d N i ) u p t o 9 . 3 3 % ( F e ) (C.V.). T h e s a m p l e p r e c i s i o n f o r t h e s e c o n d stage o f l e a c h i n g was f o u n d t o v a r y f r o m 2.12 ( M n ) u p t o 2 8 . 5 7 % ( N i ) (C.V.). I n m o s t cases t h e C V . f o r t h e s e c o n d stage o f l e a c h i n g was f o u n d t o b e g r e a t e r t h a n f o r t h e f i r s t stage o f l e a c h i n g . W h e n u s i n g 0.1M N H 2 O H - H C l i n 0.01M HNO3 t o p r e p a r e t h e s t a n d a r d s f o r t h e a t o m i c a b s o r b t i o n s p e c t r o m e t e r , t h e i n s t r u m e n t a l p r e c i s i o n was f o u n d t o v a r y b e t w e e n 0.44 ( M n ) a n d 1 . 5 7 % ( C o ) (C.V.). W h e n u s i n g 0.175M A m m o n i u m O x a l a t e i n 0.1M O x a l i c A c i d t o p r e p a r e t h e s t a n d a r d s f o r t h e atomic absorbtion spectrometer, the instrumental precision was found to vary between 0.00 (Ni) and 2.86% (Co) (C.V.). The CV. for the instrumental precision for both reagents was found to be far smaller than sample precision for both stages of the selective sequential extraction scheme. The accuracy of the methods used to determine the concentrations of Mn, Fe, Cu, Ni, and Co in the leachates was checked by comparing the analytical results of the sum of the two stages of leaching to the known concentrations of these elements in the crust and nodule as determined by XRF. The selective extractions remove all of the Mn, Cu, Ni, and Co from both crusts and nodules. The concentration of Fe is lower in the leachates because the XRF results include Fe in the aluminosilicate fraction. 4.2.2 DIFFERENTIAL X-RAY DIFFRACTION TECHNIQUE A differential X-ray diffraction technique was also developed to identify the manganese and iron phase mineralogy in marine crusts and nodules removed during the selective sequential extraction scheme. Samples were analyzed by a Philips® X-ray diffractometer. The samples were step scanned from 5° to 71°20 in O.O1°20 increments, using a counting time of one second per increment. The number of counts measured at each O.O1°20 were therefore a measure of the intensity (counts/second) at each O.O1°20 increment. Instead of sending the intensity along with the degrees 20 to the ratemeter to produce a diffractogram, they were sent to the computer and stored in an ASCII file. The digitized XRD spectra, stored in an ASCII file, was subjected to a 17 point smoothing using a computer program written by Savitzky & Golay (1964). The new XRD spectra, devoid of excess noise, was stored in a new ASCII file. Because of the removal of the targeted mineral phases, the remaining minerals are concentrated, and the mass adsorption coefficient of the sample may be changed. The result is that the XRD pattern from the treated sample generally has a greater overall intensity than that of the untreated sample. However, relative intensities within the two patterns should remain essentially the same. To subtract the XRD pattern of the treated sample from the XRD of the untreated sample, the peaks common to both must have the same height or intensity. To accomplish this, all of the points in the pattern from the treated sample must be multiplied by a scale factor. Subtration of this scaled pattern from the pattern of the untreated sample then produces the DXRD diffractogram. This can be expressed mathematically as: V f c B f = q where Aj, Bj, and Cj are the number of counts at angle / in the untreated, treated, and subtracted spectra, respectively, and k is the scale factor. The most effective way of determining the scale factor is by using an internal standard as proposed by Bryant et al. (1983). The internal standard can also be used to correct for errors in alignment or sample positioning in the X-ray beam, so that the positions of the peaks of the removed mineral phases may be more accurately determined. Since almost all crusts and nodules contain quartz, it is appropriate to use this mineral as an internal standard. To determine the value of the scale factor k, it must be remembered that the goal of subtracting the treated from the untreated XRD pattern is to remove the presence of the aluminosilicates and any other mineral phases not affected by the chemical dissolution. To remove the presence of the aluminosilicates the following situation must exist. 4 4 6 ArkBt = 0 It is now a simple procedure of dividing the intensity of the 3.34A quartz peak from the untreated XRD pattern by the 3.34A quartz peak from the treated X R D pattern. A;/B / = = fc The intensities of the treated XRD pattern (B^ -) must now be multiplied by the value of k and subtracted from the intensities of the untreated X R D pattern (A )^ to produce the intensities of the DXRD pattern (Cj). This was a simple procedure when both smoothed ASCII files for the untreated and treated X R D patterns are imported into LOTUS 123® and the repetitious calculations are preformed by the program. The graphs of the untreated, treated, and DXRD diffractograms were initially plotted by using LOTUS 123®. These graphs were then imported into LOTUS F R E E L A N C E PLUS® where they were horizontally rotated to fill an entire page in landscape mode. An added advantage of using LOTUS F R E E L A N C E PLUS® was the ability to lable the identified peaks on the pattern before being printed. It is also worth noting that even though the data needed to produce the D X R D pattern is subjected to several computer manipulations and printed on a laser printer, the d-spacings of the D X R D pattern are not distorted. For the laboratory standard crust, the DXRD pattern obtained after the first stage of leaching show that the manganese oxide present is 5Mn02 while the D X R D pattern for the laboratory standard nodule show that the manganese oxide present is todorokite and 8Mn02- The DXRD pattern obtained after the second stage of leaching show that the iron oxide present in the laboratory standard crust is ferrihydrite while the DXRD pattern for the laboratory standard nodule show that 447 the iron oxide present is akaganeite. In the laboratory standard crust the majority of the Mn, Ni, and Co are associated with the manganese oxide mineral 8MnC>2, while most of the Fe and Cu are associated in the iron oxide mineral ferrihydrite. Both 5MnC»2 and ferrihydrite consist of a randomly dissordered array of octahedra of Mn and Fe, respectively. In the laboratory standard nodule most of the Mn and Cu and half of the Ni and Co are associated with the manganese oxide minerals todorokite and 8MnC>2, while most of the Fe and the remaining Ni and Co are contained by the iron oxide mineral akaganeite. Both todorokite and akaganeite are characterized by their well ordered tunnel structures. Most of the proposed selective sequential extraction schemes directed towards the study of manganese and iron oxides in soils have also used hydroxylamine hydrochloride in nitric acid to remove the Mn oxide minerals and ammonium oxalate in oxalic acid to remove the Fe oxide minerals. Murad & Schwertmann (1988) proposed that the extraction of manganese oxides from crusts and nodules by hydroxylamine hydrochoride causes an alteration in the iron oxide mineralogy. Hence, there is some doubt on the validity of the results from the DXRD patterns obtained after the second stage of the extraction procedure. Although it can not be proven conclusively that the two stage selective sequential extraction scheme proposed above does not signaificantly change the iron oxide mineralogy, several pieces of evidence suggests that the iron oxides identified in the DXRD patterns are authentic iron mineral phases and not artifacts caused by the chemical leaching. Firstly, the observed iron oxides have DXRD patterns characterized by broad peaks. If the chemical leaching with 0.10M NH20H-HC1 in 0.01M HN03 changed the iron oxide mineralogy they most likely would invert to goethite which is the polymorph most other FeOOH phases revert to (Murray, 1979). Goethite was observed in the XRD patterns of the hydroxylamine-treated crusts studied by Murad & Schwertmann (1988). Secondly, although Murad & 448 Schwertmann (1988) also identified feroxyhite in the XRD patterns of the hydroxylamine-treated crusts, they concluded that Mossbauer spectra of the untreated crusts indicates that most of the Fe is bound to a ferrihydrite-like phase that is intimately intergrown with the Mn oxides not feroxyhite. The presence of ferrihydrite was indeed identified in the crust sample studied here. 4.3 RESULTS FROM CHAPTER 3 The selective sequential extraction scheme and differential X-ray diffraction technique were applied to a small population of crusts and nodules from the two Survey Regions in order to identify the manganese and iron phase mineralogies and their compositions. While the Mn-phase mineralogy of crusts and nodules is easily identified and reasonably well understood, the iron-bearing phases in crusts and nodules have usually been described as being cryptocrystalline or amorphous hydrated iron oxides (Glasby, 1972; Crerar & Barns, 1974). Mossbauer spectroscopic studies by Herzenberg & Riley (1969), Gager (1968), Johnson & Glasby (1969), and Carpenter & Wakeman (1973) have also led to the suggestion that the iron-bearing phase can be regarded as a amorphous ferric hydroxide or oxide-hydroxide gel (FeOOHx^O) with a particle size less than 20G\A. The DXRD patterns from the second stage of leaching on the crusts and nodules showed that the iron phase mineralogy in marine crusts and nodules is either akaganeite or ferrihydrite. The first reported presence of akaganeite in marine nodules was by Goncharov et al. (1973), although the presence of this mineral in marine nodules was discounted by Burns & Burns (1977). Since then the presence of akaganeite in marine crusts and nodules has been reported by Johnston & Glasby (1978)and by Thijs et al. (1981). This phase was identified in one Mn-rich hydrothermal crust in this study. 4 4 9 An experimental study by Vempati & Loeppert (1989) showed that in natural systems ferrihydrite, containing adsorbed and/or coprecipitated silicate, is probably influenced by the Si concentration, mechanism of silicate bonding, pH, and temperature of the environment of formation. Siliceous ferrihydrite formed during the coprecipitation of Fe oxides with silicate, would probably be stable for extended periods of time at pH > 7, even at elevated temperatures (Vempati & Loeppert, 1989). This result is significant since the average pH of sea water is 8 as reported by Glasby (1972), Burns (1965), and Defant (1961). This evidence supports the identification of ferrihydrite identified in the DXRD patterns obtained after the second stage of leaching on the crusts and nodule samples in the present study as an authentic iron oxide and not an artifact caused by the chemical leaching. This evidence is further supported the by mossbauer spectroscopic studies on untreated crusts and nodules by Murad & Schwertmann (1988). They concluded that Fe is bound to a ferrihydrite like phase that is intimately intergrown with the Mn oxides in crusts and nodules. The DXRD patterns from the second stage of leaching on the Mn-rich hydrothermal crusts and nodules, from Survey Region B, identified the manganese-bearing mineral hausmannite. Hausmannite has never been identified in marine manganese nodules (Burns & Burns, 1977; Murray & Dillard, 1979). von Heimendahl et al. (1976) did, however, identify hydrohausmannite in a nodule from the eastern equatorial Pacific. Evidence for the possible origin of hausmannite in marine manganese crusts and nodules is provided by the experimental work of Bricker (1965). Bricker (1965) was able to form synthetic hausmannite at 25°C and one atmospheric pressure. It was found that with the proper control of Eh and pH (4-0.5mV and 6.5 respectively) hausmannite could be preserved indefinitely. Except for the low pH, the laboratory solutions used by Bricker (1965) were similar in temperature and redox potential to fluids in bottom sediments in an open circulation 450 marine environment (Kumbein & Garrels, 1952). Given this evidence, hausmannite could indeed form on the sea floor, given the requisite chemical constituents (Sorem & Gunn, 1967). 451 4.4 REFERENCES Aplin, A.C., & Cronan, D.S., 1985. Ferromanganese oxide deposits from the central Pacific Ocean, I. Encrustations from the Line Islands Archipelago. Geochim. Cosmochim. Acta, 49:427-436. Bricker, O., 1965. Some stability relations in the system Mn-O^-H^O at 25° and one atmosphere total pressure. American Mineralogist, 50:1269-1354. Bryant, R.B., Curi, N., Roth, C.B., & Franzmeir, D.P., 1983. Use of an internal standard with differential X-ray diffraction analysis for iron oxides. Soil Sci. Soc. Amer. J., 47:168-173. Burns, R.G., 1965. Formation of cobalt (III) in the amorphous FeOOH-nF^O phase of manganese nodules. Nature, 203(4975):999. Burns. R.G., 1976. The uptake of colbalt into ferromanganese nodules, soils, and synthetic manganese (IV) oxides. Geochim. Cosmochim. Acta, 40:95-102. Burns, R.G., & Burns, V.M., 1977. Mineralogy. In Marine Manganese Deposits (ed. by G.P. Glasby). Elsevier Scientific Publishing Company, Amsterdam, pp.185-248. Burns, R.G., & Burns, V.M., 1979. Manganese Oxides. In Mineralogical Society of America Short Course Notes, Marine Minerals (ed. by R.G. Burns), Vol. 6. Lithocrafters Inc., Chelsea, Michigan, pp. 1-46. Callender, E., & Bowser, C.J., 1980. Manganese and copper geochemistry of interstitial fluids from manganese-nodule-rich pelagic sediments of the northeastern equatorial Pacific Ocean. Amer. J. Sci., 280:1063-1069. Calvert, S.E., & Price, N.B., 1977. Geochemical variation in ferromanganese nodules and associated sediments from the Pacific Ocean. Mar. Chem., 5:43-74. Calvert, S.E., Price, N.B., Heath, G.R., & Moore, T.C. Jr., 1978. Relationship between ferromanganese nodule compositions and sedimentation in a small survey area of the equatorial Pacific. J. Mar. Res., 36:161-183. Carpenter, R., & Wakeman, S., 1973. Mossbauer studies of marine and fresh water manganese nodules. Chem. Geol., 11:109-116. Chen, J.C, & Owen, R.M., 1989. The hydrothermal component in ferromanganese nodules from the southeast Pacific Ocean. Geochim. Cosmochim. Acta, 53:1299-1305. Crerar, D.A., & Barnes, H.L., 1974. Deposition of deep-sea manganese nodules. Geochim. Cosmochim. Acta, 38:279-300. Cronan, D.S., & Tooms, J.S., 1969. The geochemistry of manganese nodules and associated pelagic deposits from the Pacific and Indian Oceans. Deep-Sea Research, 16:335-359. 452 Dillard, J.G., Crowther, D.L., & Murray, J.W., 1982. The oxidation states of cobalt and selected metals in Pacific ferromanganese nodules. Geochim. Cosmochim Acta, 46:755-759. Dymond, J., Lyle M., Finney, B., Piper, D., Murphy, K., Conard, R., & Pisias, N., 1984. Ferromanganese nodules from MANOP sites H, S, and R - control of mineralogical and chemical composition by multiple accretionary processes. Geochim. Cosmochim. Acta, 48:931-949. Gager, H.M., 1968. Mossbauer spectra of deep-sea iron-manganese nodules. Nature, 220:1021-1023. Glasby, G.P., 1972. The mineralogy of manganese nodules from a range of marine environments. Mar. Geol., 13:57-72. Glasby, G.P., & Thijessen, T., 1982. Control of the mineralogy and composition of marine manganese nodules by the supply of divalent transition metal ions. N. Jb. Miner. Abh., 145:291-307. Goldberg, E.D., 1954. Marine chemistry, I. Chemical scavengers of the sea. J. Geol., 62:249-265. Goncharov, G.N., Kalyamin, A.V., & Lur'e, B.G., 1973. Iron-manganese concretions from the Pacific Ocean studied by a nuclear 7-resonance method. Dokl. Akad. Nauk. S.S.S.R., 212:720-723. Halbach, P., Friedrich, G., & von Stackelberg, U., 1988. The Manganese Nodule Belt of the Pacific Ocean: Geological Environment, Nodule Formation, and Mining Aspects. Ferdinand Enke Verlag, Stuttgart, 254 pp. Halbach, P., Hebisch, U., & Scherhag, C , 1981a. Geochemical variations of ferromanganese nodules and crusts from different provinces of the Pacific Ocean and their genetic control. Chem. Geol., 34:3-17. Halbach, P., Manheim, F.T., & Otten, P., 1982. Co-rich ferromanganese deposits in the marginal seamount regions of the central Pacific Basin - results of the Midpac *81. Erzmetall, 35(9):447-453. Halbach, P., & Ozkara, M., 1979. Morphological and geochemical classification of deep-sea ferromanganese nodules and its genetical interpretation. In La genese des nodules de manganese, Colloques Internationaux, C.N.R.S. No 289, pp. 77-88. Halbach, P., & Puteanus, D., 1984. The influence of the carbonate dissolution rate on the growth and composition of Co-rich ferromanganese crusts from central Pacific seamount areas. Earth Plant. Sci. Lett., 68:73-87. Halbach, P., Scherhag, C , Hebish, U., & Marchig, V., 1981b. Geochemical and mineralogical control of different genetic types of deep-sea nodules from the Pacific Ocean. Mineral. Deposita, 16:59-84. Halbach, P., Segl, M., Puteanus, D., & Mangini, A., 1983. Co-fluxes and growth rates in ferromanganese deposits from central Pacific seamount areas. Nature, 304:716-719. 4 5 3 Hein, J.R., Schulz, M.S., & Gein, L.M., in Press a. Central Pacific Cobalt-Rich Ferromanganses Crusts: Historical Perspective and Regional Variability. In Geology and Offshore Mineral Resources of the Central Pacific Region (ed. by B. Keating, & B. Bolton), Circum-Pacific Council for Energy and Mineral Resources, Earth Science Series, Houston, Texas, 23 pp. Hein, J.L., Schulz, M.S., & Kang, J.K., in Press b. Insular and Submarine Ferromanganese Mineralization of the Tonga-Lau Region. In Geology of the Tonga-Lau Regions of the Southwest Pacific (ed. by P.F Ballance, R.H. Herzer, & T.L. Vallier), Circum-Pacific Council for Energy and Mineral Resources, Earth Science Series, Houston, Texas, 46 pp. Hem, J.D., 1978. Redox processes at surfaces of manganese oxide and their effects on apueous metal ions. Chem. Geol., 21:199-218. Herzenberg, C.L., & Riley, D.L., 1969. Interpretation of the mossbauer spectra of marine iron-manganese nodules. Nature, 224:259-260. Johnson, C.E., & Glasby, G.P., 1969. Mossbauer affect determination of partical size in microcrystalline iron-manganese nodules. Nature, 222:376-377. Johnston, J.H., & Glasby, G.P., 1978. The secondary iron oxdhydroxide mineralogy of some deep-sea and fossil manganese nodules: A mossbauer and X-ray study. Geochim. Jour., 12:153-164. Klinkhammer, G.P., 1980. Early diagenesis in sediments from the eastern equatorial Pacific. II. Pore water metal results. Earth Planet. Sci. Lett., 49,81-101. Klinkhammer, G.P., & Bender, M.L., 1980. The distribution of manganese in the Pacific Ocean. Earth Plant. Sci. Lett., 49:81-101. Klinkhammer, G.P., Heggie, D.T., & Graham, D.W., 1982. Metal diagenesis in oxic marine sediments. Earth Planet. Sci. Lett., 61:211-219. Krauskopf, K.B., 1957. Separation of manganese from iron in sedimentary processes. Geochim. Cosmochim. Acta, 12:61-84. Kumbein, W.C., & Garrels, R.M., 1952. Origin and classification of chemical sediments in terms of pH and oxidation-reduction potential. Jour. Geol., 60:1-33. Landing, W.M., & Bruland, K.W., 1980. Manganese in the North Pacific. Earth Plant. Sci. Lett., 49:45-56. Lyle, M., 1981. Formation and growth of ferromanganese oxieds on the Nazca plate. Geological Society of America, Memoir 154, pp. 269-293. Manheim, FT. , & Lane-Bostwick, CM., 1988. Colbalt in ferromanganese crusts as a monitor of hydrothermal discharge on the Pacific sea floor. Nature, 335(l):59-62. Moore, W.S., & Vogt, P.R., 1976. Hydrothermal manganese crusts from two sites near the Galapagos Spreading Axis. Earth Planet. Sci. Lett., 29:349-356. 454 Murad, E. , & Schwertmann, U., 1988. Iron oxide mineralogy of some deep-sea ferromanganese crusts. American Mineralogist, 73:1395-1400. Murray, J.W., 1979. Iron-oxides. In Mineralogical Society of America Short Course Notes, Marine Minerals (ed. by R.G. Burns), Vol. 6. LithoCrafters Inc., Chelsea, Michigan, pp. 47-98. Murray, J.W., & Dillard, J.G., 1979. The oxidation of cobalt (II) adsorbed on manganese dioxide. Geochim. Cosmochim. Acta, 43:781-787. Price, N.B., & Calvert, S.E., 1970. Compositional variation in Pacific Ocean ferromanganese nodules and its relationship to sediment accumulation rates. Mar. Geol., 9:145-171. Raab, W., 1972. Physical and chemical features of Pacific deep sea manganese nodules and their implications to the genesis of nodules. In Ferromanganese Deposits on the Ocean Floor (ed. by D.R Horn), National Science Foundation, Washington, D.C., pp. 31-50. Savitzky, A., & Golay, M.J., 1964. Smoothing and differentiation of data by simplified least squares procedures. Anal. Chem., 36(8):1627-1639. Sorem, R.K., & Gunn, D.W., 1967. Mineralogy of manganese deposits, Olympic Peninsula, Washington. Econ. Geol., 62:22-56. Thijs, A., De Roy, G., Vansant, E.F., Glasby, G.P., & Thijssen, T., 1981. Mossbauer effect studies of iron in manganese nodules and associated marine sediments in five areas in the equatorial and S.W. Pacific. Geochem. Jour., 15:25-37. Toth, J.R., 1980. Deposition of submarine crusts rich in manganese and iron. Geol. Soc. Amer. Bull., Part 1,91:44-54. Usui, A., & Mita, N., 1987. Comparison of manganese nodules from the northeast equatorial Pacific (cruise SO 25) with nodules from the central Pacific basin. Geol. Jb., D87:287-313. Vempati, R.K., Loeppert, R.H., 1989. Influence of structural and adsorbed Si on the transformation of synthetic ferrihydrite. Clays and Clay Minerals, 37(3):273-279. von Heimandahl, M. , Hurbred, G.L., Fuerstenau, D.W., & Thomas, G., 1976. A transmission electron microscope study of deep-sea manganese nodules. Deep-Sea Research, 23:69-79. 

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