UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

SR isotopic study of ultramafic nodules from Neogene alkaline lavas of British Columbia, Canada and Josephine… Sun, Min 1985

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1985_A6_7 S85.pdf [ 7.86MB ]
Metadata
JSON: 831-1.0052429.json
JSON-LD: 831-1.0052429-ld.json
RDF/XML (Pretty): 831-1.0052429-rdf.xml
RDF/JSON: 831-1.0052429-rdf.json
Turtle: 831-1.0052429-turtle.txt
N-Triples: 831-1.0052429-rdf-ntriples.txt
Original Record: 831-1.0052429-source.json
Full Text
831-1.0052429-fulltext.txt
Citation
831-1.0052429.ris

Full Text

SR ISOTOPIC STUDY OF ULTRAMAFIC NODULES FROM NEOGENE ALKALINE LAVAS OF BRITISH COLUMBIA, CANADA AND JOSEPHINE PERIDOTITE, SOUTHWESTERN OREGON, U.S.A. B. Sc. Peking U n i v e r s i t y , 1982 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF in THE FACULTY OF GRADUATE STUDIES Department of G e o l o g i c a l Sciences We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA August 1985 © Min Sun, 1985 by MIN /SUN MASTER OF SCIENCE In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the The U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree that permission f o r e x t e n s i v e copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department of G e o l o g i c a l S c i e n c e s The U n i v e r s i t y of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date: 29 August 1985 ABSTRACT Twelve u l t r a m a f i c n o d u l e s from Neogene a l k a l i n e l a v a s o f B r i t i s h C o l u m b i a a r e C r - d i o p s i d e s e r i e s p e r i d o t i t e . N o d u l e s a r e d e p l e t e d o r u n d e p l e t e d w i t h r e s p e c t t o C r , A l , T i and Na abundance p e r d i o p s i d e or e n s t a t i t e f o r m u l a u n i t , and e i t h e r T i - m e t a s o m a t i s e d o r u n m e t a s o m a t i s e d . F o u r samples f r o m t h e J o s e p h i n e P e r i d o t i t e a r e even more d e p l e t e d t h a n t h e d e p l e t e d n o d u l e s and l a c k T i - m e t a s o m a t i s m . P y r o x e n e g e o t h e r m o b a r o m e t r y ( M e r c i e r , 1980) was m o d i f i e d and u s e d f o r c l i n o - and o r t h o - p y r o x e n e e q u i l i b r i u m t e m p e r a t u r e , p r e s s u r e and d e p t h c a l c u l a t i o n s . N o d u l e s came from a m a n t l e d e p t h of 30-50 km ( 9 3 6 - l 0 0 8 ° C , 9-15.5 k b ) . J o s e p h i n e P e r i d o t i t e came from a m a n t l e d e p t h o f 30-65 km ( 1003-1042°C, 10-20 kb) A f t e r e s t a b l i s h i n g an a v e r a g e t o t a l Rb b l a n k of 0.26 ng a n d Sr b l a n k o f 3.3 ng, Rb and Sr c o n t e n t s and Sr i s o t o p i c c o m p o s i t i o n s o f whole r o c k , a c i d - l e a c h e d m i n e r a l s e p a r a t e s ( o l , cpx and opx) and a c i d l e a c h a t e from t h e n o d u l e s , e l e v e n h o s t and a s s o c i a t e d whole r o c k " b a s a l t s , and a c i d l e a c h e d m i n e r a l s e p a r a t e s ( o l , cpx and opx) from t h e J o s e p h i n e P e r i d o t i t e have been a n a l y s e d . The h o s t b a s a l t s have 8 7 S r / 8 6 S r (0.70238-0.70289) s i m i l a r t o MORB, bu t v e r y much h i g h e r Rb, Sr and 8 7 R b / 8 7 S r r a t i o s '(12.7-62.1 ppm, 702-1514 ppm and 0.028-0.138, r e s p e c t i v e l y ) . T h i s i s a t t r i b u t e d t o a low 8 7 S r / 8 6 S r m a n t l e w i t h s m a l l d e g r e e o f m e l t i n g o r m e l t i n g a f t e r r e c e n t i i metasomatism by a low 8 7 S r / 8 6 S r f l u i d . N o d u l e s o c c u r o n l y i n ne n o r m a t i v e a l k a l i b a s a l t s and b a s a n i t e s . D i o p s i d e i s t h e main c a r r i e r of Rb and Sr (Rb = 0.125-3.47 ppm i n n o d u l e s and 0.023-0.076 ppm i n J o s e p h i n e P e r i d o t i t e , Sr = 9.3-239 ppm i n n o d u l e s and 0.256-0.582 ppm i n J o s e p h i n e P e r i d o t i t e ) , w i t h low 8 7 S r / 8 6 S r r a t i o (0.7022-0.7041 i n n o d u l e s and 0.7054-0.7063 i n J o s e p h i n e P e r i d o t i t e ) and 8 7 R b / 8 6 S r r a t i o (0.004-0.1 i n n o d u l e s and 0.23-0.38 i n J o s e p h i n e P e r i d o t i t e ) . O l i v i n e s c o n t a i n t h e l e a s t Rb and Sr (Rb = 0.055-0.27 ppm i n n o d u l e s and 0.084-0.102 ppm i n J o s e p h i n e P e r i d o t i t e , Sr = 0.11-3.5 ppm i n n o d u l e s and 0.153-0.305 ppm i n J o s e p h i n e P e r i d o t i t e ) and g i v e t h e h i g h e s t 8 7 S r / 8 6 S r r a t i o s (0.7036-0.7 197 i n n o d u l e s and 0.7089-0.7133 i n J o s e p h i n e P e r i d o t i t e ) and 8 7 R b / 8 6 S r r a t i o s (0.19-2.06 i n n o d u l e s and 0.8-1.73 i n J o s e p h i n e Per i d o t i t e ) . N o d u l e s from J a c q u e s L a k e , d e p l e t e d i n Sr and u n d e p l e t e d i n majo r e l e m e n t s , c o u l d be a MORB-source-type m a n t l e . O t h e r n o d u l e s r e p r e s e n t somewhat l e s s S r - d e p l e t e d m a n t l e . Whole r o c k n o d u l e d a t a f a l l on or o f f t h e c o r r e s p o n d i n g m i n e r a l i s o c h r o n s . The l a t t e r phenomenon i s due t o r e l a t i v e l y r e c e n t c o n t a m i n a t i o n w i t h i n t e r s t i t i a l m a t e r i a l h a v i n g a h i g h Rb/Sr r a t i o . " S y n t h e t i c " whole r o c k s , c a l c u l a t e d f r o m l e a c h e d - m i n e r a l d a t a , have h i g h e r 8 7 S r / 8 6 S r r a t i o s t h a n h o s t b a s a l t s . T o g e t h e r w i t h t h e w e l l d e f i n e d m i n e r a l i s o c h r o n s , t h i s s u p p o r t s t h e c o n c l u s i o n t h a t t h e n o d u l e s and h o s t b a s a l t s a r e not c o g n a t e . E q u i g r a n u l a r n o d u l e s g i v e a m i d - P r o t e r o z o i c m i n e r a l i s o c h r o n d a t e (1518-1537 Ma and ( 8 7 S r / 8 6 S r ) 0 = 0.70185). P r o t o g r a n u l a r n o d u l e s g i v e l a t e P r e c a m b r i a n (645 Ma and ( 8 7 S r / 8 6 S r ) 0 = 0.7037. e a r l y - m i d P a l e o z o i c (276-576 Ma and ( 8 7 S r / 8 6 S r ) 0 = 0.7024-0.7032) and M e s o z o i c (104 Ma and ( B 7 S r / 8 6 S r ) 0 = 0.7029) i s o c h r o n d a t e s . P o r p h y r o c l a s t i c n o d u l e s do not d e f i n e r e l i a b l e m i n e r a l i s o c h r o n s , but a l s o show e v i d e n c e of o l d age ( a t l e a s t 560-790 Ma and ( 8 7 S r / 8 6 S r ) 0 = 0.7028-0.7030). D e p l e t e d J o s e p h i n e P e r i d o t i t e g i v e s m i d d l e P a l e o z o i c m i n e r a l i s o c h r o n d a t e s (366-441 Ma and ( 8 7 S r / 8 6 S r ) 0 = 0.7038-0.7041), i n c o n f l i c t w i t h t h e g e n e r a l view t h a t t h e J o s e p h i n e P e r i d o t i t e was g e n e r a t e d i n L a t e J u r a s s i c t i m e . T h i s i m p l i e s t h a t t h e o p h i o l i t e base does n o t n e c e s s a r i l y have t h e same age as o v e r l y i n g v o l c a n i c r o c k s and d y k e s . i v Table of Contents ABSTRACT i i LIST OF FIGURES v i i LIST OF TABLES v i i i ACKOWLEDGEMENTS ix I. INTRODUCTION 1 General Statement 1 U l t r a m a f i c Nodules ...2 A l p i n e Orogenic and O p h i o l i t e P e r i d o t i t e 9 11 . GENERAL GEOLOGY 12 11 — 1. U l t r a m a f i c Nodules in B r i t i s h Columbia 12 G e o l o g i c a l and T e c t o n i c S e t t i n g 12 Previous Work 15 Samples St u d i e d 20 (1) . Jacques Lake 20 (2) . Big Timothy Mountain 21 (3) . K e t t l e R i v er 24 ( 4 ) . L a s s i e Lake 26 11-2. Josephine P e r i d o t i t e of Southern Oregon 27 I I I . CHEMICAL MINERALOGY 30 01 i v i n e 32 Clinopyroxene and Orthopyroxene 32 S p i n e l 39 Pressure and Temperature Estimates 39 IV. RB-SR ISOTOPE ANALYTICAL METHOD 46 IV-1. Sample P r e p a r a t i o n . . 46 (1) . Nodules 46 (2) . Josephine P e r i d o t i t e 47 IV- 2. Chemical Procedures 48 (1) . Laminar Flow Hood 48 (2) . Reagents 49 (3) . Rb and Sr Spikes 52 (4) . Sample D i s s o l u t i o n 53 (5) . Chemical Separation 54 (6) . Mass Spectrometry 57 (7) . Blanks 60 (8) . Data r e d u c t i o n 65 (9) . N.B.S. Standard SRM987 Measurements 67 ( 1 0 ).. I sochron C a l c u l a t i o n and P l o t 67 V. Rb-Sr ISOTOPE RESULTS 69 V- 1. Nodules and Host B a s a l t s 69 V-2. Josephine P e r i d o o t i t e 70 VI. DISCUSSION 90 General C o n s i d e r a t i o n s 90 B a s a l t s 91 v U l t r a m a f i c N o d u l e s 93 ( 1 ) . J a c q u e s Lake 94 ( 2 ) . B i g T i m o t h y M o u n t a i n 95 ( 3 ) . K e t t l e R i v e r 95 ( 4 ) . L a s s i e Lake 97 J o s e p h i n e P e r i d o t i t e 98 M a n t l e Growth C u r v e 99 Summary 100 REFERENCES 102 APPENDIX 1. PROBE ANALYTICAL DATA OF NODULE MINERALS 116 APPENDIX 2. Fe + + and Fe + + + IN SPINEL CALCULATION 119 APPENDIX 3. PROBE ANALYTICAL DATA FOR JOSEPHINE PERIDOTITE PYROXENES 120 APPENDIX 4. CALCULATED TEMPERATURE, PRESSURE, DEPTH FROM J.V.ROSS 121 APPENDIX 5. PROGRAM "RBSR" 122 APPENDIX 6. (a) PROGRAM "YORK" 127 (b) PROGRAM "PLRBSR" 131 APPENDIX 7. DUPLICATED RB-SR DATA 133 LIST OF FIGURES F i g u r e Page 2-1. L o c a t i o n map of the Juan de Fuca P l a t e System 13 2-2. C r u s t a l S t r u c t u r e of the s o u t h e r n Canadian C o r d i l l e r a . . ' 14 2-3. L o c a l i t i e s of u l t r a m a f i c n odules i n B r i t i s h Columbia 16 2-4. Sample c l a s s i f i c a t i o n based on modal m i n e r a l o g y 22 2-5. C o m p o s i t i o n of c l i n o p y r o x e n e and o r t h o p y r o x e n e i n u l t r a m a f i c n o d u l e s from B r i t i s h Columbia 23 2- 6. G e n e r a l i z e d t e c t o n i c s k e t c h map of the J o s e p h i n e P e r i d o t i t e 28 3- 1. T i - C r p l o t s of d i o p s i d e s and e n s t a t i t e s .34 3-2. (a) C r / ( C r + A l ) x l O O v s . A l p l o t of e n s t a t i t e s .36 (b) C r / ( C r + A l )x 1 00 v s . A l p l o t of d i o p s i d e s 37 3-3. C r / ( C r + A l ) x 1 0 0 v s . Mg/(Mg+Fe)x100 p l o t of d i o p s i d e s and e n s t a t i t e s ......38 3-4. (a) Mg/(Mg+Fe)x100 v s . C r / T i p l o t of e n s t a t i t e s 40 (b) Mg/(Mg+Fe)x100 v s . C r / T i p l o t of d i o p s i d e s 41 3- 5. Mg/(Mg+Fe++)xl00 v s . Cr/(Cr+A1)x100 p l o t of s p i n e l s . 4 2 4- 1. E l u t i o n c u r v e s f o r Mg, Rb, Ca, Sr and Sm on l a r g e column 56 4-2. E l u t i o n c u r v e s f o r Rb, Ca and Sr on s m a l l columns...58 4- 3. (a) T o t a l Rb b l a n k s .63 (b) T o t a l Sr b l a n k s ..64 5- 1. JL1 m i n e r a l i s o c h r o n 75 5-2. JL14 m i n e r a l i s o c h r o n ...76 5-3. JL15 m i n e r a l i s o c h r o n 77 5-4. JL18 m i n e r a l i s o c h r o n 78 5-5. BM1 1 m i n e r a l i s o c h r o n 79 5-6. BM16 m i n e r a l i s o c h r o n ..80 5-7. BM55 m i n e r a l i s o c h r o n 81 5-8. KR1 m i n e r a l i s o c h r o n ..82 5-9. KR2 m i n e r a l i s o c h r o n 83 5-10. KR35 m i n e r a l i s o c h r o n 84 5-11. LL1 m i n e r a l i s o c h r o n 85 5-12. LL14 m i n e r a l i s o c h r o n 86 5-13. JM5 m i n e r a l i s o c h r o n 87 5-14. JM14 m i n e r a l i s o c h r o n 88 5- 15. JM15 m i n e r a l i s o c h r o n . . . 89 6- 1. E a r t h e v o l u t i o n c u r v e s 101 L I S T OF TABLES T a b l e Page 2-1. V i s u a l e s t i m a t e d modal m i n e r a l o g y of t h e samples 22 2-2. C h e m i c a l c o m p o s i t i o n s of t h e h o s t and a s s o c i a t e d b a s a l t s 25 2- 3. C o n c e n t r a t i o n s of t r a c e e l e m e n t s i n h o s t and a s s o c i a t e d b a s a l t s 26 3- 1. N o d u l e m i n e r a l c o m p o s i t i o n s 31 3-2. J o s e p h i n e P e r i d o t i t e p y r o x e n e c o m p o s i t i o n s 33 3-3. C o m p a r a t i o n of p y r o x e n e s of d e p l e t e d and u n d e p l e t e d n o d u l e s and J o s e p h i n e P e r i d o t i t e 33 3- 4. C a l c u l a t e d T, P, D e p t h .44 4- 1. Reagent B l a n k s 51 4-2. I s o t o p i c c o m p o s i t i o n of N.B.S. Sr s p i k e SRM-988 53 4-3. T o t a l b l a n k s 62 4-4. C o m p a r a t i o n of t o t a l b l a n k s w i t h o t h e r l a b s 65 4- 5. 8 7 S r / 8 6 S r r a t i o s of N.B.S. SRM-987 68 5- 1. Rb-Sr d a t a of h o s t b a s a l t s 71 5-2. Rb-Sr i s o t o p e d a t a of J a c q u e s Lake n o d u l e s 71 5-3. Rb-Sr i s o t o p e d a t a of B i g T i m o t h y M o u n t a i n 72 5-4. Rb-Sr i s o t o p e d a t a of West K e t t l e R i v e r 72 5-5. Rb-Sr i s o t o p e d a t a of L a s s i e Lake 73 5-6. Rb-Sr i s o t o p e d a t a of J o s e p h i n e P e r i d o t i t e 73 5-7. Summary of m i n e r a l i s o c h r o n s 74 v i i i Acknowledgements I w i s h t o e x p r e s s s i n c e r e a p p r e c i a t i o n t o D r . R i c h a r d L e e A r m s t r o n g , t h e s i s s u p e r v i s o r , f o r h i s s u p p o r t , s u p e r v i s i o n , a d v i c e a n d e n c o u r a g e m e n t t h r o u g h o u t t h e s t u d y . M a n y s a m p l e s w e r e o b t a i n e d t h r o u g h t h e c o u r t e s y o f D r . J . V . R o s s . T h a n k s a r e a l s o d u e h i m f o r v a l u a b l e d i s c u s s i o n . I w o u l d a l s o l i k e t o t h a n k K . S c o t t , S . H o r s k y , J . K n i g h t a n d D r . J . R i c e , f o r a s s i s t a n c e a n d g u i d a n c e i n t h e l a b o r a t o r y . I am a l s o g r a t e f u l f o r h e l p a n d d i s c u s s i o n s w i t h D r . R . L . C h a s e , D r . P . M i c h a e l , D r . J . M o r t e n s o n , P r o f . R . G . S u n a n d o t h e r f a c u l t y m e m b e r s a n d s t u d e n t s . F i n a l l y , t h e i n s p i r a t i o n f r o m I n s t i t u t e o f G e o l o g y , A c a d e m i a S i n i c a , n o t a b l y P r o f . M o l a n E , P r o f . X i n h u a Z h o u , Y a n g Y u a n d J u a n j u a n X i a , i s a l s o a c k n o w l e d g e d . F i n a n c i a l s u p p o r t w a s p r o v i d e d b y a C a n a d i a n N a t u r a l S c i e n c e s a n d E n g i n e e r i n g R e s e a r c h C o u n c i l O p e r a t i n g G r a n t ( 6 7 - 8 8 4 1 ) t o R . L . A r m s t r o n g . i x I . INTRODUCTION T h i s t h e s i s examines Rb and Sr c o n c e n t r a t i o n s and Sr isotope composition of s p i n e l p e r i d o t i t e from two d i f f e r e n t s e t t i n g s : nodules from Neogene a l k a l i b a s a l t s of B r i t i s h Columbia and samples from the Mesozoic a l p i n e o p h i o l i t i c Josephine P e r i d o t i t e , southwestern Oregon. General statement P l a t e t e c t o n i c s theory d i v i d e s the l i t h o s p h e r e of the e a r t h i n t o s e v e r a l p l a t e s that o v e r l i e and move over the asthenosphere. Understanding p l a t e t e c t o n i c s and the e a r t h ' s e v o l u t i o n depends to l a r g e degree on our knowledge of mantle chemistry, p h y s i c a l p r o p e r t i e s , h i s t o r y , and c u r r e n t temperature, p r e s s u r e , and v e l o c i t y s t r u c t u r e . Present knowledge i s based on g e o p h y s i c a l data, the r e s u l t s of experiments on i n f e r r e d mantle compositions under high temperature and high p r e s s u r e (e.g. Kennedy and I t o , 1972; Ringwood, 1975), s t u d i e s of lunar and m e t e o r i t i c samples (e.g. Macdonald, 1959; Ringwood, 1962, 1975; Larimer, 1971; Gast, 1972), p e t r o l o g i c a l , geochemical, i s o t o p i c , and experimental s t u d i e s on b a s a l t s , and p e t r o l o g i c a l , s t r u c t u r a l , geochemical, i s o t o p i c and experimental s t u d i e s on n a t u r a l mantle samples ( a l p i n e p e r i d o t i t e and o p h i o l i t e , nodules in k i m b e r l i t e p i p e s , and nodules in a l k a l i b a s a l t s ) . These s t u d i e s r e v e a l that the mantle i s t y p i c a l l y a l h e r z o l i t e (ol-opx-cpx±plagioclase, s p i n e l , or garnet) 1 2 (Ringwood, 1975). U l t r a m a f i c nodules E a r l y s t u d i e s of u l t r a m a f i c nodules from k i m b e r l i t e s l e d to the c o n c l u s i o n that they come from the mantle (Wagner, 1928). E a r l y work on nodules i n a l k a l i b a s a l t s i s reviewed by Ross et a l . ( l 9 5 4 ) , Forbes and Kuno (1965,1967,), W y l l i e (1967) and Kuno (1969). Since the i n t r o d u c t i o n of p l a t e t e c t o n i c s i n the 1960's, numerous papers on nodules have been p u b l i s h e d . The study f i e l d s are d i v e r s e -i n c l u d i n g p e t r o l o g y and thermodynamics (e.g. Boyd, 1973; MacGregor, 1974; Wood, 1975; M e r c i e r , 1976, 1980); rheology (e.g. Ross, 1983); t r a c e elements (e.g. G r i f f i n and Murthy, 1968; Basu and Murthy, 1977; Basu, 1978; Jagoutz et a l . , 1979) and Sr, Nd and Pb i s o t o p e geochemistry (e.g. Paul, 1971; Stueber and Ikramuddin, 1974; Burwell, 1975; O'Nions et a l . , 1977; Kramers, 1977; Menzies and Murthy, 1980; Stosch et a l . , 1980; Jagoutz et a l . , 1980; Cohen et a l . , 1984; Mengel et a l . , 1984; Betton and G i v e t t a , 1984; B i e l s k i - Z y s k i n d et a l . , 1984). The u l t r a m a f i c nodules i n k i m b e r l i t e p i p e s are mainly garnet l h e r z o l i t e and e c l o g i t e and those i n a l k a l i b a s a l t s are dominantly s p i n e l l h e r z o l i t e (Ringwood, 1975). The nodules of a l k a l i b a s a l t s S p i n e l l h e r z o l i t e nodules have a simple mineralogy of o l i v i n e , orthopyroxene, c l i n o p y r o x e n e and s p i n e l . Some workers are i n favour of a cognate r e l a t i o n s h i p of the 3 nodules with t h e i r host rock (e.g. O'Hara, 1967, 1968), i . e . they are cumulates from the ascending magma. Many others (Ross et a l . , 1954; W i l s h i r e and Binns, 1961; H a r r i s et a l . , 1967) agree that the nodules are samples of the mantle, a c c i d e n t l y caught up i n the ascending b a s a l t i c magma. P a r t i a l m e l t i n g of s p i n e l l h e r z o l i t e i n the mantle may produce a s i l i c a u n d e r s a t u r a t e d b a s a l t and leave a more magnesian l h e r z o l i t e , h a r z b u r g i t e or du n i t e as res i d u e (Kushiro, 1969). D i f f e r e n c e s i n the chemistry of l h e r z o l i t e nodules may be due to o r i g i n a l h e t e r o g e n e i t y as w e l l as d i f f e r e n t degrees or c o n d i t i o n s of p a r t i a l m e l t i n g . Both cognate and a c c i d e n t a l u l t r a m a f i c nodules may c o e x i s t at the same l o c a l i t y . Ross et a l . ( l 9 5 4 ) emphasized the u n i f o r m i t y i n mineralogy and chemistry of u l t r a m a f i c nodules and suggested that these nodules were d e r i v e d from a uniform mantle. Work by White (1966), Jackson (1968) and Kuno (1969) has shown that there are two main types of nodules in a l k a l i b a s a l t , a l h e r z o l i t e s e r i e s and a d u n i t e - w e h r l i t e - py r o x e n i t e s e r i e s , accompanied by a m i n o r i t y of e c l o g i t e and gabbro nodules. The second s e r i e s was a l s o named as black c l i n o p y r o x e n e type, b l a c k type, pyroxene s u i t e and other l e s s d e s c r i p t i v e names ( W i l s h i r e and S h e r v a i s , 1975). The dunite - w e h r l i t e - p y r o x e n i t e and gabbro s u i t e s are thought to be of cumulate o r i g i n and the s p i n e l l h e r z o l i t e s u i t e s and e c l o g i t e are thought t o be mantle fragments (White, 1966). 4 From m i n e r a l chemistry, two s o r t s of u l t r a m a f i c nodules, A l - a u g i t e and C r - d i o p s i d e , were d i s t i n g u i s h e d . The A l - a u g i t e group i s c h a r a c t e r e d by A l and T i - r i c h a u g i t e , c o m p a r a t i v e l y F e - r i c h o l i v i n e and orthopyroxene, and A l - r i c h s p i n e l , dominanted by a u g i t e - r i c h v a r i e t i e s . The C r - d i o p s i d e group i s c h a r a c t e r i z e d by C r - r i c h c l i n o p y r o x e n e and s p i n e l and by Mg-rich o l i v i n e and orthopyroxene, dominated by o l i v i n e - r i c h l h e r z o l i t e s ( W i l s h i r e and S h e r v a i s , 1975). The A l - a u g i t e group was a s c r i b e d by most workers to a cumulus p r o c e s s . N e v e r t h e l e s s metamorphic t e x t u r e s of o l i v i n e - r i c h members of t h i s group were recog n i z e d by Jackson (1968), Trask (1969) and Fus t e r et a l . (1970). These d u n i t e s were c o n s i d e r e d to be r e s i d u e s of p a r t i a l melt that produced t h o l e i i t i c l avas (Jackson and Wright, 1970) or i n t e r p r e t e d as C r - d i o p s i d e p e r i d o t i t e m o d i f i e d by p a r t i a l m e l ting and r e a c t i o n ( W i l s h i r e and Sh e r v a i s , 1975). On the other hand, the C r - d i o p s i d e group was c o n s i d e r e d by most workers to represent mantle m a t e r i a l from which v a r i a b l e amounts of b a s a l t i c l i q u i d have been removed. Within the C r - d i o p s i d e group, l e s s deformed p y r o x e n e - r i c h members are thought t o represent s e g r e g a t i o n of melts l i k e those of the A l - a u g i t e group. From s t r u c t u r a l - f a b r i c s t u d i e s , three important t e x t u r a l groups have been r e c o g n i z e d (Mercier and Ni c o l a s , 1 9 7 5 ) : ( a ) . P r o t o g r a n u l a r : c h a r a c t e r i z e d by a coarse g r a i n s i z e (5-10 mm), with the c u r v i l i n e a r boundaries between the 5 p r i n c i p a l m i n e r a l s , o l i v i n e and orthopyroxene. The c r y s t a l s have almost no e l o n g a t i o n and the nodules seem to be devoid of any f o l i a t i o n or l i n e a t i o n . The d i o p s i d e and s p i n e l are much sm a l l e r (1mm) and the r e l a t i o n s h i p s between them are such that both m i n e r a l s are always i n d i r e c t c o n t a c t with l a r g e e n s t a t i t e g r a i n s . T h i s t e x t u r e i s b e l i e v e d to r e p r e s e n t minor m o d i f i c a t i o n of o r i g i n a l magmatic t e x t u r e by p a r t i a l m e l t i n g . The s y m p l e c t i t i c s p i n e l r e s u l t s from e x s o l u t i o n of more aluminous pyroxene. T h i s c o u l d take place by the lowering of p r e s s u r e d u r i n g the upward m i g r a t i o n of p e r i d o t i t e through the g a r n e t / s p i n e l f a c i e s boundary (Green, 1976). The nodules with t h i s t e x t u r e are i n t e r p r e t e d as coming from a s t a t i c p a r t of the mantle (Ross, 1983). (b) . P o r p h y r o c l a s t i c : c h a r a c t e r i z e d by l a r g e and e l o n g a t e d s t r a i n e d p o r p h y r o c l a s t s of and small g e n e r a l l y p o l y g o n a l s t r a i n - f r e e n e o b l a s t s of o l i v i n e and orthopyroxene. Hand specimens are marked by a f o l i a t i o n o u t l i n e d by o l i v i n e and e n s t a t i t e together with a s p i n e l l i n e a t i o n . T h i s t e x t u r e i s i n t e r p r e t e d as c h a r a c t e r i s t i c of deformed mantle. (Ross, 1983). (c) . E q u i g r a n u l a r : c h a r a c t e r i z e d by a l l the phases having almost the same shape and small s i z e (l-2mm). The g r a i n boundaries are t y p i c a l l y s t r a i g h t and converge at 120° in t r i p l e p o i n t s . T h i s t e x t u r e r e s u l t s from high temperature r e c r y s t a l l i z a t i o n and i s i n t e r p r e t e d to have formed in mantle l e v e l s that are both deformed and e x c e p t i o n a l l y hot. (Ross, 1983). 6 Since the 1970's, many s t u d i e s of t r a c e and rare e a r t h elements and of Sr, Pb and Nd i s o t o p e s have been c a r r i e d out on the u l t r a m a f i c nodules.. The work confirms that most A l - a u g i t e w e h r l i t i c nodules r e p r e s e n t cumulates, mostly cognate (a few represent a c c i d e n t a l l y a c q u i r e d cumulates from an e a r l i e r magmatic event) and that most C r - d i o p s i d e l h e r z o l i t e nodules are fragments of the upper mantle. The l h e r z o l i t e nodule whole-rock i s g e n e r a l l y not i n e q u i l i b r i u m with the host b a s a l t and the 8 7 S r / 8 6 S r r a t i o s are g e n e r a l l y n e i t h e r c o r r e l a t e d with Sr c o n c e n t r a t i o n s nor with Rb/Sr r a t i o s (e.g. Paul,1971; Burwell, 1975; Mengel et a l . , 1984). The a c i d l e a c h m a t e r i a l has proven to be e n r i c h e d i n Rb and Sr and not i n e q u i l i b r i u m with the nodule, (e.g. G r i f f i n and Murthy, 1968; Basu and Murthy, 1977). A c i d washed mineral s e p a r a t e s , c l i n o p y r o x e n e , orthopyroxene and o l i v i n e , have been analysed by s e v e r a l authors. The minerals are not i n e q u i l i b r i u m with the host b a s a l t and some mineral i s o c h r o n s have been ob t a i n e d . For example, Stueber et a l . (1974) d e r i v e d a mineral i s o c h r o n , from Mt. A l d a z , A n c t a r c t i c a , g i v i n g a date of 610 ± 110 Ma with ( 8 7 S r / 8 6 S r ) 0 = 0.7020 ± 0.0002 and one from Kilbourne Hole, New Mexico, g i v i n g a date of 1270 ± 230 Ma with ( 8 7 S r / 8 6 S r ) 0 = 0.7024 ± 0.0002. In those cases the isochron ages are s i m i l a r to the age of the u n d e r l y i n g c r u s t a l basement and are c o n s i s t e n t with the idea that c o n t i n e n t a l l i t h o s p h e r e i s being sampled. Basu and Murthy (1977) d e r i v e d 7 a m i n e r a l i s o c h r o n , from Baja C a l i f o r n i a , g i v i n g a date of 3400 ± 300 Ma with ( 8 7 S r / 8 6 S r ) 0 = 0.70057 ± 0.00004, which i s much o l d e r than any nearby c r u s t a l r o c k s . I t i s a l s o r e p o r t e d some mineral separates do not d e f i n e an isochron (e.g. Stuber et a l . , 1974; Polve and A l l e g r e , 1980). The d i s t i n c t i o n between " d e p l e t e d " and "undepleted" mantle i s an important achievement i n s t u d i e s of the mantle. Incompatible elements w i l l be e n r i c h e d i n the melts and de p l e t e d i n the r e s i d u e s of p a r t i a l m e l t i n g . The "undepleted mantle" i s the mantle that geochemically c o n s i s t e n t with the Sm-Nd e v o l u t i o n of c h o n d r i t i c m e t e o r i t e s , and c l o s e to presumed "bulk e a r t h " chemical and i s o t o p e composition f o r Rb-Sr and U-Pb and c l o s e to c h o n d r i t i c i n many n o n v o l a t i l e t r a c e element abundances and r a t i o s . The " d e p l e t e d mantle" has r e l a t i v e l y low c o n c e n t r a t i o n s of incompatible elements, compared to the "bulk e a r t h " . D i f f e r e n t elements have been s e l e c t e d as deplet i o n / e n r i c h m e n t i n d i c a t o r s by d i f f e r e n t a uthors. Ross (1983) adopted the M e r c i e r (1976) chemical d e p l e t i o n c r i t e r i a (evident on a Cr vs. T i p l o t ) . Many authors use rare e a r t h elements or i s o t o p i c r a t i o s , i . e . undepleted mantle has undepleted r a r e e a r t h p a t t e r n , eNd = 0 and eSr = 0 ( i . e . 1 f t 3Nd/ 1""Nd = 0.51187 and B 7 S r / 8 6 S r = 0.7045, today, r e s p e c t i v e l y ) . The d e p l e t e d mantle has low c o n c e n t r a t i o n of LREE, eNd = +10 ( Jacobson et a l . , 1984) and low 8 7 S r / B 6 S r (<0.7030). 8 A few s p i n e l l h e r z o l i t e nodules have undepleted c h a r a c t e r (e.g. " p r i m i t i v e nodules" of Jagoutz, 1979). Most l h e r z o l i t e nodules have a d e p l e t e d c h a r a c t e r . The mantle d e p l e t i o n process i s i n t e r p r e t e d to occur by continuous or e p i s o d i c a c c r e t i o n of the c o n t i n e n t a l l i t h o s p h e r e ( A l l e g r e et a l . , 1982), or in terms of a m u l t i p l e stage e x t r a c t i o n of melt f r a c t i o n (Jacobsen et a l . , 1984). The "undepleted mantle" can be i n t e r p r e t e d as r e s u l t i n g from an incompatible-element enrichment i n the mantle a f t e r the p r e v i o u s s e p a r a t i o n of the c r u s t and mantle, or as a " p r i m i t i v e / p r i m o r d i a l " mantle. The "enr i c h e d " mantle i s i n t e r p r e t e d to be a r e s u l t of metasomatism i n the mantle. The metasomatic f l u i d , e n r i c h e d in i ncompatible elements, may be d e r i v e d from subducted c r u s t (e.g. Armstrong, 1968, 1981; Chase, 1981; Hofmann and White, 1982; Z i n d l e r et a l . , 1982; White and Hofmann, 1982; White and P a t c h e t t , 1984), or from a lower mantle plume source (e.g. Lupton, 1983; Vollmer, 1983). The " p r i m i t i v e mantle" concept i s supported by s t u d i e s of i s o t o p e s of i n e r t gases (e.g. A l l e g r e et al.,1983; Lupton, 1983). Only the Hawaiian b a s a l t s s i m u l taneously meet the Sr, Pb and Nd isotope and i n e r t gas c r i t e r i a f o r a " p r i m i t i v e " source (White, 1985). He, among the l e a s t r e a c t i v e of gases and present only in trace q u a n t i t i e s i n a i r , i s the most important i n d i c a t o r of a p r i m i t i v e source. C o n t i n e n t a l rocks are d e p l e t e d i n 3He, but MORB g l a s s e s have 9 excess 3He. No mechanism has been found that c o u l d produce the non-radiogenic 3He/"He r a t i o s found i n the eart h ' s mantle. The d e t e c t i o n of excess 3He i n the MORB samples can only be i n t e r p r e t e d as evidence f o r the e x i s t e n c e of " p r i m i t i v e " mantle He. In many cases i t s t r a n s f e r to the s u r f a c e may be uncoupled with the f l u x e s of other elements (White, 1985). A l p i n e orogenic and o p h i o l i t e p e r i d o t i t e The t e c t o n i c s i g n i f i c a n c e of a l p i n e orogenic p e r i d o t i t e and o p h i o l i t e was recog n i z e d by Steinmann (1926 and 1927) i n the European A l p s . A l p i n e p e r i d o t i t e s c h a r a c t e r i s t i c a l l y i n t r u d e d c l o s e to the axes of maximum deformation along o r o g e n i c b e l t s and i s l a n d a r c s . I n t r u s i o n has f r e q u e n t l y been c o n t r o l l e d by major f a u l t s with s t r i k e lengths up to s e v e r a l hundred m i l e s , which almost c e r t a i n l y extend i n t o the mantle. Steinmann (1927) o r i g i n a l l y proposed that p e r i d o t i t e s represented u l t r a m a f i c cumulates from submarine l a v a . Hess (1938) suggested that the a l p i n e p e r i d o t i t e s were the r e s u l t of the d i r e c t i n j e c t i o n of a primary u l t r a m a f i c magma but such hypotheses are given l i t t l e credence today. Based on the p e r s i s t e n t a s s o c i a t i o n of a l p i n e p e r i d o t i t e s with orogenic a n d e s i t e , i t was a l s o proposed that the p e r i d o t i t e s represent the cumulate or r e s i d u a l p o r t i o n of a n d e s i t i c magmas brought to the su r f a c e by f a u l t i n g (Hess, 1955; Osborn, 1969; C h a l l i s , 1969; M i y a s h i r o , 1973). 10 O p h i o l i t e s c o n s i s t of bas a l u l t r a m a f i c l a y e r s from s e v e r a l hundred meters to s e v e r a l k i l o m e t e r s t h i c k o v e r l a i n by gabbroic and d o l e r i t i c rocks which in turn grade upward i n t o mafic p i l l o w l a v a s and b r e c c i a s , f r e q u e n t l y a s s o c i a t e d with r a d i o l a r i a n c h e r t s . Hess emphasized the d i s t i n c t i o n s between a l p i n e p e r i d o t i t e s and o p h i o l i t e s (Ringwood, 1975), but the trend of more recent and d e t a i l e d s t u d i e s has been to u n d e r l i n e t h e i r a f f i n i t i e s . A l p i n e p e r i d o t i t e s are now regarded as nothing more than the b a s a l zones of o p h i o l i t e complexes. Impressed by the s i m i l a r i t y of the o p h i o l i t i c sequence to the h y p o t h e t i c a l v e r t i c a l s e c t i o n of the ocean f l o o r , many i n v e s t i g a t o r s proposed that o p h i o l i t e s represent fragments of the a n c i e n t oceanic l i t h o s p h e r e ( i . e . Davies, 1968 and 1971; Coleman, 1971). Some workers c o n s i d e r e d the p e r i d o t i t e s to be formed by c r y s t a l s e t t i n g from a b a s a l t i c magma du r i n g the formation of oceanic c r u s t (Thayer, 1964,1967,1969; McTaggart, 1971). Others suggested the p e r i d o t i t e s represent r e s i d u a l mantle m a t e r i a l (e.g. Hess, 1964; Dickey, 1970). A l p i n e p e r i d o t i t e s and o p h i o l i t e s are in part t e c t o n i t e s , f o l i a t e d and deformed at high temperature, but surrounding rocks are oft e n of very low metamorphic grade. The b a s a l u l t r a m a f i c rocks are s i m i l a r i n pe t r o l o g y , mineralogy and s t r u c t u r a l f e a t u r e s to nodules i n a l k a l i b a s a l t s . Mainly because of the h i g h l y a l t e r e d nature of the A l p i n e p e r i d o t i t e s , there are fewer geochemical and i s o t o p i c 11 s t u d i e s on them than on u l t r a m a f i c nodules. However, study of a w e l l - p r e s e r v e d A l p i n e p e r i d o t i t e has the advantage over nodules i n that f i e l d r e l a t i o n s between the v a r i o u s l i t h o l o g i e s can be preserved, and t h i s may a i d i n i n t e r p r e t i n g t h e i r o r i g i n . A l l recent s t u d i e s support the hypothesis that a l p i n e -o p h i o l i t i c p e r i d o t i t e s are fragments of the upper mantle (e.g. Polve and A l l e g r e , 1980). Geochemical and i s o t o p i c s t u d i e s r e v e a l that some are s u i t a b l e to be d e p l e t e d suboceanic mantle (e.g. Menzies and Murthy, 1978), they have the same eNd-eSr c o r r e l a t i o n l i n e as oceanic b a s a l t s (Richard and A l l e g r e , 1980). Many cannot be e x p l a i n e d by simple s i n g l e stage models of p a r t i a l m e l t i n g and (or) c o n t a m i n a t i o n . Thus the idea t h a t the oceanic mantle i s p r o g r e s s i v e l y more and more d e p l e t e d and that i t i s mixed and r e c y c l e d was proposed (Polve and A l l e g r e , 1980). Jacobson et a l . (1984) p o s t u l a t e d a m u l t i p l e p a r t i a l m e l t i n g h i s t o r y f o r T r i n i t y p e r i d o t i t e . 1 2 11 . G E N E R A L GEOLOGY 11 — 1 U l t r a m a f i c nodules in B r i t i s h Columbia G e o l o g i c a l and t e c t o n i c s e t t i n g An important f e a t u r e of the present t e c t o n i c s i t u a t i o n o f f the west coast of Canada i s the r i d g e - t r e n c h -transform t r i p l e j u n c t i o n between the Juan de Fuca, P a c i f i c , and American l i t h o s p h e r i c p l a t e s near the c o n t i n e n t a l margin at approximately 51°N ( F i g u r e 2-1). The Juan de Fuca p l a t e i s one of the l a s t remnants of the F a r a l l o n p l a t e , which converged with the western margin of North America over the l a s t 150 m i l l i o n y e a r s . The c o l l i s i o n of the P a c i f i c - F a r a l l o n r i d g e with the American p l a t e between 25 and 30 m i l l i o n years ago (Ma) l e d to the i s o l a t i o n of the Juan de Fuca p l a t e at about 20 Ma. Since then i t s southern edge has migrated northward and there has been a r e d u c t i o n i n spreading r a t e and c l o c k w i s e r i d g e and p l a t e r o t a t i o n . For the p e r i o d from 7 to 4 Ma, motion of Juan de Fuca p l a t e r e l a t i v e to the America p l a t e was to the northeast at about 6.0 cm/yr. Between 4 and 3 Ma, the E x p l o r e r p l a t e broke o f f from Juan de Fuca p l a t e and was o v e r r i d e n by the American p l a t e . The Juan de Fuca p l a t e continues to subduct to the no r t h e a s t at about 4 cm/yr (Riddihough, 1984). The Juan de Fuca p l a t e B e n i o f f zone d i p s 15° eastward under Vancouver I s l a n d (Rodgers, 1983). Depth to Moho and to the low v e l o c i t y zone are shown i n F i g u r e Fig 2-1. Location map of the Juan de Fuca plate system (from Riddihough, 1984). 14 F i g . 2-2 C r u s t a l s t r u c t u r e o f t h e s o u t h e r n C a n a d i a n C o r d i l l e r a . S t r u c t u r e c o n t o u r s a t 5 km i n t e r v a l s g i v i n g d e p t h t o t h e M o n o . S t i p p l e d p a t t e r n s h o w s z o n e o f g e o m a g n e t i c s t a t i o n s m a r k i n g t r a n s i t i o n b e t w e e n h i g h l y c o n d u c t i v e c r u s t a n d u p p e r m a n t l e t o t h e s o u t h w e s t , a n d l e s s c o n d u c t i v e c r u s t a n d u p p e r m a n t l e t o t h e n o r t h e a s t . S t r u c t u r e s e c t i o n W-E s h o w i n g P - w a v e v e l o c i t y 1n k m / s . Q u a r t e r n e r y a n d R e c e n t v o l c a n i c r o c k s o c c u r a t t h e l o c a l i t i e s m a r k e d b y s o l i d t r i a n g l e s l a b e l l e d " v " T h e t h i n - s k i n n e d t h r u s t f a u l t s o f t h e R o c k y M o u n t a i n B e l t a r e s h o w n s c h e m a t i c a l l y e a s t o f t h e s o u t h e r n R o c k y M o u n t a i n T r e n c h ( R M T ) . a n d t h e g e n e r a l o u t l i n e o f t h e d e e p l y r o o t e d S h u s w a p M e t a m o r p h i c C o m p l e x ( S M C ) 1s s h o w n s c h e m a t i c a l l y w e s t o f t h e R o c k y m o u n t a i n T r e n c h ( f r o m M o n g e r a n d P r i c e . 1 9 7 9 ) . 8 7 S r / 8 6 S r c o n t o u r s o f M e s o z o i c I g n e o u s r o c k a r e a l s o s h o w n ( A r m s t r o n g , 1 9 8 5 , p e r s . c o m m . ) . N o d u l e s a m p l e l o c a l i t i e s a r e s h o w n w i t h I n v e r t e d t r i a n g l e s : <JL f r o m J a c q u e s L a k e , BM f r o m B 1 g T i m o t h y M o u n t a i n , KR f r o m W e s t K e t t l e R i v e r , L L f r o m L a s s i e L a k e . 15 Recent v o l c a n i c c e n t e r s are l a r g e l y c o n f i n e d to three b e l t s ( F i g u r e 2-3). The G a r i b a l d i B e l t v o l c a n i c c e n t e r s i n southwestern B r i t i s h Columbia are the northern c o n t i n u a t i o n of the Cascade arc and occur above the subducted Jan de Fuca p l a t e . The E-W t r e n d i n g v o l c a n i c b e l t at approximately 52°N i s the Anahim B e l t , c o n s i d e r e d by Bevier et a l . (1979) to be a hot spot t r a c e . The S t i k i n e B e l t in northern B r i t i s h Columbia i s thought to be r i f t r e l a t e d (Souther and Hickson, 1984). Throughout the Intermontane B e l t of B r i t i s h Columbia are i s o l a t e d c i n d e r cones and flows of a l k a l i c o l i v i n e b a s a l t erupted from Neogene through Recent time (Ross, 1983; W.H.Mathews unpublished data; B e v i e r , 1983). Many of these v o l c a n i c flows and cones c o n t a i n p e r i d o t i t e nodules. F i g u r e 2-3 shows the l o c a l i t i e s of b a s a l t s c o n t a i n i n g u l t r a m a f i c nodules i n B r i t i s h Columbia. Previ o u s work S o r e g a r o l i (1968) d e s c r i b e d nodules from B i g Timothy Mountain. L i t t l e j o h n and Greenwood (1974) analysed the mi n e r a l s of s p i n e l l h e r z o l i t e nodules from Jacques Lake, C a s t l e Rock and N i c o l a Lake. Temperatures were c a l c u l a t e d from d i s t r i b u t i o n of i r o n and magnesium between s p i n e l and o l i v i n e . They concluded that the l h e r z o l i t e nodules of C a s t l e Rock and Jacques Lake are probably from the upper mantle, whereas the N i c o l a Lake l h e r z o l i t e s are probably 17 c r y s t a l cumulates. They saw no evidence of r e g i o n a l chemical v a r i a t i o n s . F u j i i and Scarfe (1982) s t u d i e d nodules from the West K e t t l e R i v e r . They concluded that the upper mantle beneath southern B r i t i s h Columbia i s dominanted by s p i n e l l h e r z o l i t e but c o n t a i n s some banding on a s c a l e of c e n t i m e t r e to metres and that the chemical v a r i a t i o n s of c o n s t i t u e n t minerals w i t h i n i n d i v i d u a l nodules of the chromian d i o p s i d e s e r i e s are small even when banding i s p r e s e n t . C a l c u l a t e d e q u i l i b r a t i o n temperatures, using the two-pyroxene geothermometer of Wells (1977), ranged between 920 and 980°C. P r e s s u r e s of e q u i l i b r a t i o n , based on p u b l i s h e d phase s t a b i l i t y experiments, were i n f e r r e d between 10 to 18 kbar (30-60 km). Ross (1983) d i d numerous chemical and r h e o l o g i c a l analyses of nodules from West K e t t l e R i v e r , L a s s i e Lake, L i g h t e n i n g Peak, Big Timothy Mountain, Jacques Lake, Summit Lake, and C a s t l e Rock. He presented geotherms and d e v i a t o r i c s t r e s s v s. depth and s t r a i n r a t e / v i s c o s i t y vs. depth p r o f i l e s f o r a l l the above l o c a l i t i e s and p o s t u l a t e d a dynamic model of the upper mantle beneath B r i t i s h Columbia. Ross separated u l t r a m a f i c nodules i n B r i t i s h Columbia i n t o the f o l l o w i n g s i x groups: A l - a u g i t e (black c l i n o p y r o x e n e ) s e r i e s : (a) . Mg-rich w e h r l i t e s . Metacumulates. (b) . F e - r i c h w e h r l i t e s . Cumulate. 18 C r - d i o p s i d e s e r i e s (most abundant type) Magmat i c — (c) . Dark emerald-green d i o p s i d e - b e a r i n g T i - r i c h l h e r z o l i t e s . Metamorphic, with b r i g h t emerald-green d i o p s i d e — (d) . Depleted l h e r z o l i t e , h a r z b u r g i t e and d u n i t e . ( e j . Undepleted l h e r z o l i t e . ( f ) . Coarse-grained homogeneous w e b s t e r i t e . a l l with r e c r y s t a l l i s e d magmatic t e x t u r e s with or without p l a s t i c deformation. B r e a r l e y et a l . (1984) s t u d i e d nodules from the Summit Lake b a s a n i t o i d flow. T h e i r microprobe data on the m i n e r a l phases i n d i c a t e that the nodules are g e n e r a l l y w e l l e q u i l i b r a t e d . C a l c u l a t e d e q u i l i b r a t i o n temperatures, using the two-pyroxene geothermometer of Wells (1977), ranged between 1080 to 1100°C. Pressures of e q u i l i b r a t i o n , e s t i mated from a C o r d i l l e r a n geotherm, were between 10 to 20 kbar. The temperatures are somewhat higher than estimates from nodules of other l o c a l i t i e s . They concluded that e i t h e r the Summit Lake s u i t e represents samples from a deeper source region i n the upper mantle or the Late Cenozoic geotherm v a r i e d i n time and space. B r e a r l e y and S c a r f e (1984) s t u d i e d p a r g a s i t i c amphiboles in a chrome d i o p s i d e - bearing s p i n e l l h e r z o l i t e trapped w i t h i n an a l k a l i b a s a l t i c l a v a flow at L i g h t e n i n g Peak. They i n d i c a t e d that the p a r g a s i t e i s in e q u i l i b r i u m with the other phases in s p i n e l l h e r z o l i t e and probably 19 c r y s t a l l i z e d w i t h i n the s p i n e l s t a b i l i t y f i e l d of the upper mantle from a v o l a t i l e - r i c h metasomatic f l u i d . The p a r g a s i t e always shows evidence of m e l t i n g . They i n t e r p r e t e d the me l t i n g i n the p a r g a s i t e as caused by one of three p r o c e s s e s : superheating by the host a l k a l i b a s a l t , decompression as the magma ascended, or _in s i t u p a r t i a l m e l t i n g w i t h i n the upper mantle. They concluded that the p a r t i a l m e l t i n g of amphibole-bearing s p i n e l l h e r z o l i t e p r o v i d e s a p o s s i b l e mechanism f o r the g e n e r a t i o n of l a t e Cenozoic a l k a l i n e magmas of the Intermontane B e l t of B r i t i s h Columbia. F i e s h i n g e r and N i c h o l l s (1977) d e s c r i b e d the u l t r a m a f i c nodules i n K o s t a l Lake and Takomkane Mountain (near Jacques Lake and Big Timothy Mountain) and N i c h o l l s et a l . (1982) d e s c r i b e d the u l t r a m a f i c nodules i n C a s t l e Rock, N i c o l a Lake, Jacques Lake and Big Timothy Mountain i n t h e i r b a s a l t papers. Maxwell (1976) an a l y s e d Rb and Sr i s o t o p e s i n two nodules from Jacques Lake and one from Big Timothy Mountain, with poor data r e p r o d u c i b i l i t y . D i f f e r e n c e s of 8 7 R b / 8 6 S r i n reruns of the same min e r a l are about 30% and of 8 7 S r / 8 6 S r are up to ±0.003 f o r o l i v i n e and orthopyroxene and ±0.001 f o r c l i n o p y r o x e n e . Maxwell a t t r i b u t e d t h i s to d i f f e r e n t batches of mineral separates used f o r repeat a n a l y s e s , o v e r l e a c h i n g , s p i k i n g e r r o r s , and e r r a t i c l a b contamination. One nodule from Jacques Lake gave a mineral i s o c h r o n date of 2000 ± 100 Ma with ( 8 7 S r / 8 6 S r ) 0 = 0.7024 ± 0.0001. The other 2 0 Jacques Lake nodule and the Big Timothy Mountain nodule d i d not give reasonable m i n e r a l isochrons,, but they show evidence of great age (4700 ± 2400 and 4400 + 2500 Ma with ( 8 7 S r / 8 6 S r ) 0 = 0.7020-0.7006, r e s p e c t i v e l y . He concluded that the apparent is o c h r o n i s due to in_ s i t u decay of 8 7Rb and that the lower date r e p r e s e n t s a "mantle event". The cause of d i s e q u i l i b r i u m in other two nodules was unknown, but he thought metasomatism in the mantle may be a p o s s i b l e e x p l a n a t i o n . The new analyses suggest that h i s Rb analyses may have been too low because of o v e r e s t i m a t i o n of the Rb blank. Samples s t u d i e d Samples for t h i s study are from Jacques Lake, Big Timothy Mountain, West K e t t l e R i v e r and L a s s i e Lake. The chemical compositions of the host and a s s o c i a t e d b a s a l t s are shown in Tables 2-2 and 2-3. (1). Jacques Lake (5 on F i g . 2-3) (52°28.6'N 121°9.4'W) The Jaques Lake l o c a l i t y i s a small cone of coarse b a s a l t i c t u f f , P l e i s t o c e n e in age (Campbell, 1978), 4 miles south of Quesnel Lake i n c e n t r a l B r i t i s h Columbia. The la v a adhering to nodule JL14 i s sodic a l k a l i o l i v i n e b a s a l t s e r i e s ankaramite (Armstrong, 1985, pe r s . comm.). U l t r a m a f i c nodules and fragments of other rocks are s c a t t e r e d throughout the t u f f . The nodules are sub-rounded and range in s i z e from 2 to 35 cm. Most are l e s s than 15 cm i n diameter ( L i t t l e j o h n and Greenwood, 1974). 21 Four nodules from Jaques Lake (JL1, JL14, JL15 and JL18) were s e l e c t e d f o r t h i s study. They f a l l i n the l h e r z o l i t e r e g ion i n OL-OPX-CPX t r i a n g l e ( F i g u r e 2-4; Table 2-1) and are a l l of p r o t o g r a n u l a r t e x t u r e . O l i v i n e and orthopyroxene range up to 4 mm. O l i v i n e forms an i n t e r l o c k i n g mosaic of equidimensional g r a i n s , n e a r l y c o l o r l e s s to pale yellow i n hand specimen and c o l o r l e s s i n t h i n s e c t i o n . Kink bands are observed i n most o l i v i n e g r a i n s . Orthopyroxene occurs as subhedral g r a i n s with p e r f e c t cleavage, dark brown i n hand specimen and pale yellow i n t h i n s e c t i o n . Clinopyroxene forms sma l l anhedral g r a i n s , b r i g h t emerald green i n hand specimen and pale green in t h i n s e c t i o n . New spongiform m i c r o c r y s t a l l i n e c l i n o p y r o x e n e , due to p a r t i a l m e l t i n g , occurs commonly around c l i n o p y r o x e n e g r a i n s . S p i n e l s occur as i r r e g u l a r l y - s h a p e d g r a i n s i n s i d e or i n co n t a c t with orthopyroxene, some subhedral s p i n e l g r a i n s c r y s t a l l i z e d i n i n t e r g r a n u l a r p a r t i a l melt. Somewhat e q u i g r a n u l a r and p o r p h y r o c l a s t i c t e x t u r e were found i n JL15 and J L 1 8 , r e s p e c t i v e l y . The c l i n o p y r o x e n e i s d i o p s i d e and orthopyroxene i s e n s t a t i t e (Table 3-1, F i g u r e 2-5). (2 ) . B i g Timothy Mountain (4 on F i g . 2-3) (52°63'N, 121°9.4'W) B i g Timothy Mountain, not f a r from Jaques Lake, i s a cone (600 meters i n diameter) of p o t a s s i c s e r i e s a l k a l i (adhering t o nodule BM11 and BM26) to p i c r i t i c a l k a l i F i g 2-4 S a m p l e c l a s s i f i c a t i o n b a s e d o n mooai m i n e r a l o g y i n t e r m s o f o l i v i n e , o r t h o p y r o x e n e a n d c l i n o p y r o x e n e . 23 CoMgSi206 MgSiO, F i g 2 - 5 C o m p o s i t i o n o f c 1 1 n o p y r o x e n e a n d o r t h o p y r o x e n e i n u l t r a m a f i c n o d u l e s f r o m B r i t i s h C o l u m b i a . (adhering to nodule BM55) basalt or basanite (Armstrong, 1985, pers. comm.), Pleistocene in age (Campbell, 1978). The ultramafic nodules are round and subround, they range in size from 5 to 50 cm, and comprise from 1 to 25% of the lavas (Soregaroli, 1968). Three nodules from t h i s l o c a l i t y (BM11, BM16 and BM55) were selected for t h i s study. BM11 i s l h e r z o l i t e and BM16 and BM55 are o l i v i n e websterite (Figure 2-4, Table 2-1). BM11 and BM55 exhibit protogranular texture as observed at Jacques Lake. BM55 o l i v i n e displays spectacular kink bands in large grains. BM16 exhibits equigranular texture. Olivine and orthopyroxene grains are less than 1.5 mm across, with 120° 24 t r i p l e j u n c t i o n s . Subhedral c l i n o p y r o x e n e and s p i n e l are 0.5 mm a c r o s s . The clinopyroxene i s d i o p s i d e and orthopyroxene i s e n s t a t i t e (Table 3-1, F i g u r e 2-5). ( 3 ) . West K e t t l e River (1 on F i g . 2-3) (49°46.9'N, 119°4.0'W) There are four l a v a flow l a y e r s found in West K e t t l e River f i e l d . The four l a y e r s are stacked c o n c o r d a n t l y . The lower three are each approximately 2 meters t h i c k , the top l a y e r i s 11 meters t h i c k . The flows are s e p a r a t e d by rubbly h o r i z o n s about 10 cm t h i c k , but no weathering zones were observed, suggesting that the flows were erupted w i t h i n a short time. Two K-Ar dates f o r nearby b a s a l t s are 2.8±1.5 Ma (Church, 1980) and 4.2±0.5 Ma (Boyle, 1980; Stevens et a l . , 1982). The three lower l a y e r s are c a l c - a l k a l i n e s e r i e s s u b a l k a l i n e b a s a l t s , while the top l a y e r i s s o d i c a l k a l i o l i v i n e b a s a l t or basanite (Armstrong, 1985, p e r s . comm.) (Table 2-2). U l t r a m a f i c nodules were found o n l y i n the top l a y e r . T h i s l a y e r shows w e l l developed columnar j o i n t s with 50 cm average widths of columns. The nodules are sub-rounded and range in s i z e from 2 to 25 cm. The three nodules (KR1, KR2 and KR35) s e l e c t e d f o r t h i s study are l h e r z o l i t e ( F igure 2-4, Table 2-1). KR2 e x h i b i t s p o r p h y r o c l a s t i c t e x t u r e . E l o n g a t e d o l i v i n e and orthopyroxene give a f o l i a t i o n in hand specimen, and s p i n e l s are strung out p a r e l l e l to that f o l i a t i o n in t h i n s e c t i o n . The [010] of o l i v i n e i s o b l i q u e to the f o l i a t i o n by T a b l e 2 - 2 C h e m i c a l c o m p o s i t i o n s o f h o s t a n d a s s o c i a t e d b a s a l t s (wt%) WKR1B WKR2B WKR3B WKR4B KR35B KRB L L 1 B L L 1 4 B J L 1 4 B BM11B BM26B BM55B S 1 0 2 4 8 . 8 6 4 9 .31 4 9 . 6 1 4 5 .01 44 . 8 3 44 . 5 47 . 5 9 4 6 . 75 42 . 2 1 4 1 . 8 0 4 3 . 36 41 . 4 0 T 1 0 2 2 . 35 2 . 22 2 . 17 2 . 9 4 2 . 5 7 3 . 12 2 . 3 6 2 . 33 2 . 5 8 3 . 19 3 . 16 3 . 16 A 1 2 0 3 16 . 4 1 16 . 6 7 16 . 6 2 14 . 6 5 14 . 6 0 14 . 1 15 8 3 14 . 36 13 . 27 13 . 0 3 13 . 38 12 . 9 5 F e 2 0 3 T 12 . 5 3 12 . 4 9 1 1 . 6 7 13 . 4 5 14 . 5 0 1 1 . 6 6 13 . 0 4 14 . 5 0 15 . 2 6 13 . 3 1 15 . 8 3 F e 2 0 3 3 . 73 F e O 8 . 5 2 MnO 0 . 19 0 . 17 0 . 16 0 . 18 0 . 19 0 . 2 1 0 . 17 0 . 18 0 . 18 0 . 2 0 0 . 19 0 .21 MgO 4 . 8 9 4 . 5 9 4 . 9 9 8 . 5 3 8 . 44 9 . 5 0 7 . 9 4 10 . 5 0 7 . 32 10 64 10 . 6 4 1 1 . 18 C a O 9 81 9 . 33 9 . 6 6 9 . 29 9 . 2 0 4 . 2 0 8 . 79 7 . 9 3 15 . 4 3 9 . 0 1 8 . 9 5 8 88 N a 2 0 3 . 17 3 . 39 3 . 35 3 . 4 6 3 . 4 3 1 . 6 5 3 . 0 4 3 . 17 2 . 14 3 . 4 0 3 . 35 3 . 29 K 2 0 1 . 26 1 . 32 1 . 26 1 . 6 4 1 . 4 4 0 . 79 1 . 9 9 1 . 19 1 . 6 9 2 . 6 0 2 . 79 2 . 29 P 2 0 5 0 . 52 0 . 52 0 .51 0 . 8 5 0 . 8 0 0 . 6 4 0 . 56 0 . 6 9 0 . 8 7 0 . 87 0 . 83 CIPW n o r m A p 1 . 22 1 . 22 1 . 2 0 2 . 0 0 1 . 88 1 . 83 1 . 5 0 1 , 31 1 62 2 . 0 5 2 . . 04 1 . 9 5 I 1 4 52 4 . . 27 4 . 17 5 . 6 6 4 . 9 5 5 . 93 4 . 5 3 4 . . 4 8 4 97 6 . 15 6 . 0 8 6 . 10 Mt 2 4 5 2 . 44 2 . 28 2 6 3 2 . 84 5 4 1 2 . 2 8 2 . 55 2 84 2 . 9 9 2 6 0 3 . 10 O r 7 . 54 7 . 8 9 7 . 53 9 8 2 8 6 3 9 75 1 1 8 9 7 . 12 0 0 1 5 . 28 16 7 0 13 75 Ab 27 . 15 29 . 0 3 2 8 . 6 7 16 . 51 17 . 0 5 12 . 92 22 48 24 . 94 O. . 0 0 . 0 3 2 1 0 . 76 A n 27 . 16 26 . 6 9 26 . 8 9 1 9 . 8 6 2 0 . 48 14 . 75 2 3 . 94 21 . 71 21 . 9 2 12 . 81 13 . 4 1 14 . 0 2 Ne 0 . 0 0 . 0 0 . 0 7 13 6 . 7 1 12 . 25 1 . 91 1 . 2 0 9 9 5 15 . 8 2 13 . 82 14 . 91 L c 0 . 0 0 . 0 0 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 7 . 94 0 . 2 5 0 . 0 0 . 0 01 - F o 4 . 0 6 4 . 0 0 4 . 0 2 1 1 . 42 1 1 . 58 1 1 . 0 3 1 1 . 23 1 5 . 94 5 . 5 5 14 . 1 1 14 . 0 0 15 . 36 01 - F a 4 . 7 0 4 . 98 4 . 25 7 . 6 9 9 . 07 4 . 01 7 . 27 9 . 04 5 . 0 0 8 . 75 7 . 25 9 55 01 - C a 0 . 0 O 0 O . 0 O. 0 0 . 0 0 . 0 0 . 0 0 . 0 1 . 12 0 . O 0 . 0 0 . 0 D ( - E n 3 75 3 . 24 3 . 8 0 5 . 23 4 . 8 0 7 . 92 3 . 9 7 3 . 74 1 0 . 57 6 . 77 6 . 8 6 6 . 37 Dt - F s 3 . 9 3 3 . 6 6 3 . 64 3 . 19 3 . 42 2 . 61 2 . 33 1 . 92 8 64 3 . 81 3 . 22 3 . 5 9 DI -Wo 7 . 8 0 6 . 98 7 . 6 0 8 . 8 6 8 . 57 1 1 . 47 6 . 6 5 6 . 0 2 19 . 84 1 1 . 19 1 0 . 78 1 0 . 53 H y - E n 2 . 79 2 6 1 3 0 3 O. 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 O. 0 H y - F s 2 . 92 2 . 9 5 2 . 91 0 . 0 0 . 0 0 . O 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 0 . 0 C o m m e n t : KRB d a t a f r o m Fuj11 & S c a r f e ( 1 9 8 2 ) , o t h e r s f r o m A r m s t r o n g ( 1 9 8 5 , p e r s . c o m m . ) . WKR1B. WKR2B a n d WKR3B a r e l o w e r l a y e r s o f t h e W e s t K e t t l e R i v e r e r u p t i o n s e q u e n c e . T h e y a r e n e p h e l I n e - n o r m f r e e s u b a l k a l i n e b a s a l t s t h a t l a c k n o d u l e s . O t h e r s a r e a l k a l i b a s a l t s t h a t c o n t a i n n o d u l e s . M e t h o d : A r m s t r o n g ' s d a t a a r e d e r i v e d f r o m XRF a n a l y s e s o f p r e s s e d p o w d e r p e l l e t s u s i n g a n a u t o m a t e d P h i l l i p s X - r a y s p e c t r o m e t e r i n t h e O c e a n o g r a p h y D e p a r t m e n t o f U . B . C . R e s u l t s a r e o x i d i z e d , a n h y d r o u s , a n d n o r m a l i z e d t o 100 p e r c e n t t o t a l s . T r a c e e l e m e n t a n a l y s e s o f t h e s a m e p e l l e t s u s i n g t h e s a m e e q u i p m e n t a r e r e p o r t e d i n t a b l e 2 - 3 . M a j o r a n d t r a c e e l e m e n t c o n c e n t r a t i o n s a r e b a s e d o n c o m p a r i s o n w i t h U S G S a n d o t h e r w i d e l y a n a l y s e d I g n e o u s r o c k s t a n d a r d s . M a s s a b s o r p t i o n c o e f f i c i e n t s a r e c a l c u l a t e d f r o m m a j o r e l e m e n t c o m p o s i t i o n s . 26 T a b l e 2 - 3 C o n c e n t r a t i o n s o f t r a c e e l e m e n t s - i n h o s t b a s a l t s ( p p m ) ( f r o m A r m s t r o n g , 1 9 8 5 , p e r s . c o m m . ) WKR1B WKR2B WKR3B WKR4B K R 3 5 B L L 1 B LL 14B J L 14B BM1 1B BM26B BM55B B a 3 1 6 3 2 8 2 9 3 4 7 0 3 9 7 4 1 6 4 15 5 6 9 9 3 2 8 7 3 891 C r 81 103 137 23 1 3 8 3 3 2 4 376 4 4 5 4 3 3 4 5 4 44 1 Nb 34 32 3 1 6 6 56 4 8 48 59 9 5 9 0 94 N1 4 9 4 9 48 164 2 7 0 2 7 3 3 7 8 3 8 6 3 3 5 3 9 7 3 5 5 Rb 17 17 17 29 2 6 2 9 2 1 13 57 52 54 S r 8 4 4 6 7 6 6 2 8 9 1 4 8 0 3 8 0 6 714 1444 1231 1203 1218 V 2 1 5 2 17 2 0 4 2 16 2 2 0 149 163 122 2 1 9 24 1 2 6 8 Y 23 22 2 1 25 24 24 23 28 26 24 27 Z r 2 1 0 2 0 0 193 3 1 9 281 2 4 4 237 3 6 7 401 391 3 9 5 an angle of 15° to 3 0 ° , due to i n t r a - c r y s t a l l i n e g l i d e . KR 1 e x h i b i t s p r o t o g r a n u l a r to p o r p h y r o c l a s t i c t e x t u r e . KR35 e x h i b i t s e g u i g r a n u l a r t e x t u r e and shows i n c i p i e n t m e l t i n g of c l i n o p y r o x e n e . The c l i n o p y r o x e n e i s d i o p s i d e and orthopyroxene i s e n s t a t i t e . O l i v i n e has the composition of Fo = 90.3-90.6. (Table 3-1, F i g u r e 2-5). (4 ) . L a s s i e Lake (2 on F i g . 2-3) (49°35.8'N, 118°55.3'W) L a s s i e Lake i s near the West K e t t l e R i v e r l o c a l i t y . The nodules are exposed on a group of h i l l s by L a s s i e Lake. No b a s a l t s t r a t i g r a p h y was observed during f i e l d work. Three K-Ar dates from nearby b a s a l t flows are 4.7±0.2 Ma ( C h r i s t o p h e r , 1978), 5.0+0.2 Ma ( C h r i s t o p h e r , 1977,1978) and 5.9±0.6 Ma (Boyle, 1980, Stevens et a l . , 1982). The lava i s i n f e r r e d to have approximately the same age as the West K e t t l e R i v e r l a v a s . The l a v a adhering to nodule LL1 i s p o t a s s i c s e r i e s a l k a l i o l i v i n e b a s a l t and that to LL14 i s sod i c s e r i e s p i c r i i c b a s a l t (Armstrong, 1985, per s . comm.). The nodules, weathered and sm a l l e r than those from West K e t t l e R i v e r , range i n s i z e from 2 to 15 cm. The two l h e r z o l i t e nodules (LL1 and L L 1 4 ) ( F i g u r e 2-4, Table 2-1) s e l e c t e d f o r t h i s study e x h i b i t p r o t o g r a n u l a r t e x t u r e . LL1 shows c o n s i d e r a b l e melt, LL14 has more than average brownish a l t e r a t i o n ( i d d i n g s i t e ? ) on g r a i n boundaries. The c l i n o p y r o x e n e i s d i o p s i d e and orthopyroxene i s e n s t a t i t e . O l i v i n e of LL1 has the composition of Fo = 89.7 ( t a b l e 3-1, F i g u r e 2-5). 11-2. Josephine P e r i d o t i t e of Southern Oregon The Josephine P e r i d o t i t e i s s i t u a t e d i n Klamath Mountains of southwestern Oregon and Northern C a l i f o r n i a ( F i gure 2-6). In these mountains s i x major north - south elongated l i t h i c b e l t s have been d e s c r i b e d by Irwin (i960, 1972). Josephine P e r i d o t i t e l i e s along the western margin of Irwin's western J u r a s s i c B e l t . T h i s b e l t , some 8 to 32 km wide and over 320 km long, i s composed of s h a l e , greywacke, and metavolcanic rocks of the G a l i c e and Rogue Formations, a v a r i e t y of i n t r u s i v e rocks, and the I l l i n o i s River Gabbro. The Josephine P e r i d o t i t e i s i n f a u l t c ontact on the west with the Dothan and F r a n c i s c a n t e r r a n e s of the Oregon and C a l i f o r n i a Coast Ranges. These i n c l u d e d t e c t o n i c a l l y d i s r u p t e d melange of greywacke, shal e , metavolcanic rocks, c h e r t , limestone and s e r p e n t i n i t e . There i s general agreenment that rocks i n the a r c u a t e b e l t s of the Klamath Mountains represent fragments of i s l a n d 28 F i g . 2 - 6 G e n e r a l i z e d t e c t o n i c s k e t c h map o f t h e J o s e p h i n e P e r i d o t i t e a n d i t s v i c i n i t y ( f r o m D i c k . 1 9 7 5 ) . • - s a m p l e l o c a l i t i e s . a r c s and ocean basins that c o l l i d e d with the c o n t i n e n t a l margin (e.g., Hamilton, 1969; Irwin, 1972, Schweickert and Cowan, 1974). The Josephine P e r i d o t i t e , c o v e r i n g n e a r l y 650 km2 and extending c o n t i n u o u s l y f o r almost 150 km along the western edge of the Klamath S t r u c t u r a l Arc, i s one of the l a r g e s t bodies of u l t r a m a f i c rock i n the world. The p e r i d o t i t e i s commonly 10 to 30% s e r p e n t i n i z e d . The f r e s h p e r i d o t i t e c o n s i s t s l a r g e l y of h a r z b u r g i t e ; there i s only a minor amount of i r r e g u l a r l y d i s t r i b u t e d dunite and v o l u m e t r i c a l l y i n s i g n i f i c a n t o r t h o p y r o x e n i t e and l h e r z o l i t e . An e x t e n s i v e l y p e t r o l o g i c study was c a r r i e d out by Dick 29 (1975) i n the area sampled. He suggested t h a t the p e r i d o t i t e i s the r e s i d u e of at l e a s t two episodes of p a r t i a l m e l t i n g in the mantle and that i t i s the r e l i c t of the e a r l i e s t stages of the c o n s t r u c t i o n of a circum - oceanic v o l c a n i c sequence. Four samples from Josephine P e r i d o t i t e were s e l e c t e d f o r t h i s study. They are a l l h a r z b u r g i t e ( F i g u r e 2-4, Table 2-1). JM2 from Vulcan Peak (42°11.0'N, 123°59.0'W) e x h i b i t s p r o t o g r a n u l a r t e x t u r e . There i s moderate (~15%) s e r p e n t i n i z a t i o n along mineral boundaries and mineral c r a c k s . O r i g i n a l m i n e r a l s are mainly o l i v i n e and orthopyroxene. JM14 from E i g h t D o l l a r Mountain (42°15.4'N, 123°41.0'W) e x h i b i t s p o r p h y r o c l a s t t e x t u r e . Elongated o l i v i n e has p r e f e r e d o r i e n t a t i o n and obvious kink bands. Orthopyroxene c l a s t s are products of fragmentation. S e r p e n t i n i z a t i o n i s minor (2-3%). JM5 and JM15, a l s o from E i g h t D o l l a r Mountain, e x h i b i t o r i g i n a l p r o t o g r a n u l a r t e x t u r e o v e r p r i n t e d by l a t e r fragmentation. S e r p e n t i n i z a t i o n i s minor (~5%) D i o p s i d e occurs as small anhedral g r a i n s i n low abundance in a l l samples. 3 0 I I I . CHEMICAL MINERALOGY T h r e e p o l i s h e d t h i n s e c t i o n s , K R 1 , K R 2 a n d L L 1 , w e r e p r e p a r e d f o r w a v e l e n g t h d i s p e r s i v e m i c r o p r o b e a n a l y s i s a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a . I n e a c h p o l i s h e d t h i n s e c t i o n , t w o g r a i n s o f o l i v i n e , s p i n e l , c l i n o p y r o x e n e a n d o r t h o p y r o x e n e w e r e a n a l y s e d , u s i n g a n A p p l i e d R e s e a r c h L a b o r a t o r i e s S c a n n i n g E l e c t r o n M i c r o p r o b e Q u a n t a m e t e r o p e r a t e d a t 15 k v 40 n A ( o n A l ) . T h e w o r k w a s g u i d e d b y J . K n i g h t a n d J . R i c e . T h e s t a n d a r d s u s e d w e r e p r e p a r e d b y J . R o s s a n d J . K n i g h t . I n e a c h g r a i n , t h e a n a l y s e s w e r e r e p e a t e d a t 5 t o 6 s c a t t e r e d p o i n t s . T h e d a t a a r e i n A p p e n d i x 1 a n d m i n e r a l f o r m u l a e i n T a b l e 3 - 1 . F e 2 + a n d F e 3 + c o n t e n t s o f s p i n e l w e r e c a l c u l a t e d a s s u m i n g a M 2 + M 3 + 0 „ f o r m u l a ( A p p e n d i x 2 ) . N o s i g n i f i c a n t c h e m i c a l z o n a t i o n o r v a r i a t i o n w a s f o u n d w i t h i n m i n e r a l g r a i n s a n d , i n e a c h t h i n s e c t i o n , t h e t w o m i n e r a l g r a i n s a n a l y s e d g a v e t h e s a m e c h e m i c a l c o m p o s i t i o n . T h e a v e r a g e v a l u e f o r e a c h m i n e r a l w a s u s e d f o r t h e f o l l o w i n g p l o t s a n d c a l c u l a t i o n s . C l i n o p y r o x e n e a n d o r t h o p y r o x e n e a n a l y s e s f o r s e v e r a l o t h e r n o d u l e s i n t h i s s t u d y w e r e p r o v i d e d b y J . V . R o s s . C l i n o p y r o x e n e a n d o r t h o p y r o x e n e d a t a f r o m D i c k ( 1 9 7 5 ) ( A p p e n d i x 3 ) w e r e c a l c u l a t e d t o m i n e r a l c o m p o s i t i o n s i n t h e s a m e m a n n e r a s t h e B r i t i s h C o l u m b i a n o d u l e m i n e r a l a n a l y s e s ( T a b l e 3 - 2 ) . A l t h o u g h t h e d a t a a r e f r o m s a m p l e s o t h e r t h a n t h o s e i n v o l v e d i n t h i s S r i s o t o p e s t u d y , t h e y a r e s t i l l p e r t i n e n t t o o u r d i s c u s s i o n b e c a u s e t h e J o s e p h i n e P e r i d o t i t e r - r -r 73 73 i cn r~ 73 i n ~~ ro -* r o O O O O —. o b b b 1 C/) CO O CO o o g i —• CO O CO o CO 00 01 oo _k o O o > ~ j cn CO i — t o CJ ro CO CO O O O o o o -> O O b o O o O O 5 o O o u ~* r o CO CO CO o o O • _^ Q b b •o. oo O o 5 oo 00 o ro ro & O l oo O O o O O O 3E -j -j ~i CO O o O co CO o o o ro r o o o o -n O O o t o t o ro ID — — 01 + O O b CO CO u i + O O o CO CO 00 o O O •n b O b o CO + Ul U l + i . o o O ro CO 01 o 01 ro "1 01 — -1 00 CO CD & £. o CO O O CO CD 2 CQ •o. ~4 ^ oo 03 CO 2 CQ IO ~ J + T l IS X o o o o — . CO 1 co 01 TO > co — CO — • -X 8 r r X T v X o i i B c c c i - i - 7 3 73 73 S 2 r - r - r — cn to — cn — oo oi .u cocooococooococsoooo co — oo — cooorococo-o. O O O O O O O O O O — — ro — — M-k — r O W — o o r o c n r o c o ^ o o o — O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O r o - f c - o — c j r o c j c o c j O O O O O O O O O O — — — — — — r o r o — r o c n O O C D ^ l O l C O O C J C O O C D O ^ — 00£». — . U C J O O O O O O O O O O O b b b b o b b b b o O O O O O O O O O O j k . u . f c . u . u a i . c . O T - f c - u i - o c n c n ^ i ^ i c n c n c n c n c n £ > o i c o . b 0 ~ > c o o o c n c n ^ i O O O O O O O O O O o o b o o o b b b o u u u r j u & u r o u u — 0 0 0 1 — rO — O l - U C O - E i O O O O O O O O O O O O O O O O O O O O 0 0 0 0 0 0 0 - - 0 c o a i c o c n o i - j ^ j o o c x j O O O O O O O O O O O O O O O O O O O O 01 ro ro — 4^ — —. — co O O O O O O O O O O o o b o o b o o b b o o - o cn cnoidioioioicnoicncn a iu ico — — r o o o r o o i o o O O O O O O C Q C O O O O O O O C D O O C O O O - J O O ~ J ~ J 0 1 C D - J -JCO-J — r o . & ^ i c n r o ^ i O O C O O O O O O O O r O O O MOAombcnMuui r - r - x x x c n o T j c . 1 - 1 - 7 3 7 3 7 3 3 2 1 -— CJ O l — — . u i r o — u i cn -u cocooococoooooao ^ O C D * - O I ~ J O O O O O O O O O O O O — ro c j ro — CJ CJ CJ 4 . 0 0 O — -J. r o r o — O O O O O O O O o b o o o b o o o o - o o - - -— o o o i r o o i r o o o i O O O O O O O O o b b b b b b b - j o o o o - j c n c o o o o o o i - 4 - . O J ^ O ~ J l o O O O O O O O O b o o b b g b b O O O O O O O O C J C J C J C J r o c j c j r o O O O O O O O O C O C D - J O O O D C O ^ J - J O O 0 1 U b - > I C D O O O O O O O O 00 -g oo 00 ~ j -g 01 co co co co cn co O O O O O O O O 0 — . o b - - -0 1 — :o Co co ro co O — 0001C0O1-403 O O O O O O O O o o o o b b o b c o r o r o r o c o — r o r o o i oo — - J o -4 O w O O O O O O O O O O O O O O O O Q O c n o i c n c n c n c n c n c n a i c n ~ s i ^ i ~ j o i o o ~ 4 ai co co co co — O i D o ^ a o o a i c n ^ C O C O r o O I & C S - J U l • C O l - f c A C O O l O I O l —. ro co — >i t u 6 3 2 has l i m i t e d v a r i a t i o n i n mi n e r a l composition. A l l the analyses r e p o r t e d sum to 98.1-101.0 weight percent t o t a l oxide. 0 1 i v i n e The composition of o l i v i n e in B r i t i s h Columbia nodules and Josephine P e r i d o t i t e i s s t r i k i n g l y uniform. O l i v i n e s from KR1,KR2 and LL1 have f o r s t e r i t e contents F o 9 0 . 6 > F o 9 0 . 3 and F o 8 9 7 , r e s p e c t i v e l y (Table 3-1). Josephine o l i v i n e s have a range of f o r s t e r i t e content from F o B 9 5 to F o 9 , 7 , with an average F o 9 0 . 3 (Dick, 1975). Clinopyroxene and orthopyroxene Clinopyroxene and orthopyroxene both i n nodules and i n Josephine P e r i d o t i t e are C r - d i o p s i d e s and e n s t a t i t e , r e s p e c t i v e l y . Clinopyroxene i n nodules v a r i e s from Wo=45.7 to 48.1, En=46.7 to 49.3, Fs=3.7 to 5.4. Clinopyroxene in Josephine P e r i d o t i t e v a r i e s from Wo=45.9 to 46.9, En=48.7 to 50.4, Fs=3.5 to 4.6 (Tables 3-1 and 3-2). Orthopyroxene i n nodules v a r i e s from Wo=1.1 to 2.2, En=86.6 to 90.2 and Fs=8.6 to 12.2. Orthopyroxene i n Josephine P e r i d o t i t e v a r i e s from Wo=1.2 to 3.5, En=87.7 to 90.6 and Fs=8.0 to 9.0 (Table 3-1 and 3-2). Numbers of Cr and T i per d i o p s i d e and e n s t a t i t e formula u n i t have been p l o t e d i n F i g u r e 3-1 ( a f t e r Ross,1983). Table 3-2 •Josephine P e r i d o t i t e pyroxene compositions (data from Dick,1975) Cpx SI Al TI Fe Mg Ca Cr 0 Wo En Fs J28f 1 .89 0 168 0 0011 0 0854 0.93 0 89 0.043 6 46.9 48 7 4 5 J871 1 .92 0 099 0 OOOB 0. 0730 1 OO 0 91 0.029 6 45 9 50 4 3 7 J120 1 .89 0. .209 0 .0041 0 .0848 0.90 0 .85 0.032 6 46 4 49 0 4.6 J120 1 .93 0 090 0 .0014 0 .0699 0.99 0 .92 0.020 6 46 5 49.9 3.5 Opx SI Al TI Fe Mg Ca . Cr 0 Wo En Fs J28f 1 .90 0 . 146 0 .0005 0 . 1756 1.71 0 .063 0.025 6 3 2 87 7 9 O J46h 1 .92 0. 134 0. 0010 0. 1662 1 .69 0. 067 0.024 6 3 5 87 8 8 6 J46h 1 .90 0. 131 0. O010 0. 1685 1 .74 0. 052 0.023 6 2 6 88 8 8 6 J871 1 .94 0. 094 0 0003 0. 1653 1 .75 0 041 0.015 6 2 1 89 5 8 4 J114 1 .90 O. 085 0 OOOS 0. 1775 1 82 0 041 0.014 6 2 0 89 3 8 7 J120 1 .91 0. 093 0 0005 0. 1793 1 .82 0 022 0.012 6 1 1 90 0 8 9 J46g 1 .93 0. 039 0 OOOB 0. 1636 1 .86 O 030 0.015 6 1 4 90 6 8.0 Table 3-3 Comparison of pyroxenes of depleted and undepleted nodules and Josephine Peridotite Mg/(Mg+Fe)x100 Cr/(Cr+A1)xlOO Cr/TI Al T 1 Cr Na Depleted nodules Diopside 92.2-92.9 Enstatite 91. 1-91 .3 * 11.4- 19.7 6.8-15 7 .6-13.5 12-40 0 0 . 14-0 . Il-O 21 15 0.001-0 0.0004-0 .005 0O2 0 0 .027 O i l -0 -0 .038 .024 0 O .050 .003-0 0 099 007 Undepleted nodules Diopside 89.8-90.5 Ens t a t i t e 87.7-90 2 5.0- 9.1 4.1- 6.1 1 .4-3.5 3-3.7 0 0 .28-0. .18-0. 32 23 0.008-0 0.002-0 .016 .004 0 0 .017 .009 -0 -0 .028 .012 0. 0. 111-006-0 0. 138 010 Josephine p e r i d o t i t e Diopside 91.4-93.4 Enstatite 90.7-91.9 13.1-22.6 11.3-27.7 7 23 .7-39.4 .6-50.4 0. 0. 09-O. 04-0. 21 15 0.001-0. O.OO03-0. 004 001 0. 0. 020 012 0. -0. 043 025 F i g . 3-1 T i - C r p l o t s of d i o o s i d e s a"<s e n s t a t i tes 35 From F i g u r e 3-1, we d e r i v e the f o l l o w i n g c o n c l u s i o n s : a. Most of d i o p s i d e underwent more i n t e n s i v e T i metasomatism than e n s t a t i t e . b. LL14 and KR2 are d e p l e t e d nodules without T i metasomatism. KR1 and BM11 are d e p l e t e d nodules with T i metasomatism. c. . BM16 i s undepleted without T i metasomatism, KR35, JL14 and BM55 are undepleted nodules with T i metasomatism. J.L15 and JL18 are undepleted nodules with u n s p e c i f i e d T i metasomatism, the u n c e r t a i n t y due to lack of d i o p s i d e data. d. LL1 d i o p s i d e f a l l s on the boundary of de p l e t e d and undepleted. E n s t a t i t e i n d i c a t e s somewhat deplet e d c h a r a c t e r . Because e n s t a t i t e c o n t a i n s l e s s Cr and T i than d i o p s i d e , the c o n t r a s t i n assignment i s probably not s i g n i f i c a n t . e. A l l pyroxenes from Josephine P e r i d o t i t e are of s t r o n g l y d e p l e t e d c h a r a c t e r without T i metasomatism. The degree of d e p l e t i o n i s l a r g e r than that of the nodules. In graphs of Cr/(Cr+Al)x100 vs. A l ( F i g u r e 3-2) and Mg/(Mg+Fe)xl00 vs. Cr/(Cr+Al)x100 (Figure 3-3), depleted and undepleted groups are s h a r p l y separated. In the e n s t a t i t e Mg/(Mg+Fe)x100 vs. C r / T i diagram (Figure 3-4(a)), the d e p l e t i o n trend i s w e l l d e f i n e d . In the d i o p s i d e Mg/(Mg+Fe)x100 vs. C r / T i diagram d e p l e t e d nodules are somewhat more s c a t t e r e d ( F i g u r e 3-4(b)), presumably due A l Atoms per Formula 0 . 1 0 0 . 1 4 0 . 1 8 0 . 2 2 0 . 2 6 0 . 1 0 o , 1— 1 i I I I I u I ro O X o o O O S I * ( TO K>' / 1 j / to 1 A / XI i »— 1* 1 rt 1* > a. / 1 "* 3= / a. c / r / r x Ft " < c .r— r-oo ~~ u i » rt l» a. • 00 o z O J ai 37 D l o p s i d e •JL • KR3S bt\dep l a t e d •A, \ \ * — - — I T — LO 15 20 Cr/(Cr+Al)xl00 F i g . 3-2(b) C r / ( C r + A l ) x 1 0 0 vs. Al p l o t of d i o p s i d e s / I D l o p s i d e ,--"/ •KR i , ' / ! / D j p l « t « < l N o 4 u l » , , , / . 'LL14 •1-KR2 / , "/ , ' d o » « p h l n « P e r l d o t 11« «' " .'•KR35\ '.BM55 B M 1 6 ! - ' j L 1 - 4 ' 10 15 _ -0 25 Cr/<Cr*Al)xl00 E n s t a t 1 t e _ _ _ _ ~ - 4 — - " . -LL1 B M 1,. 6f-KR35 .BM11 ~JL 14 JL 18 5 ! 0 15 J O 25 50 C r / ( C r » » l ) « 1 0 0 3-3 C r / ( C r + A l ) x 1 0 0 vs Mg/(Mg+Fe)x100 p l o t of d i o p s i d e s and enstatlt«a 39 to v a r i a b l e T i metasomatism. The composition ranges of pyroxenes i n d e p l e t e d and undepleted nodules and Josephine P e r i d o t i t e are given i n Table 3-3. In every case the assignment of i n d i v i d u a l specimens can be made without c o n t r a d i c t i o n . S p i n e l Only three nodules were analysed f o r s p i n e l c o mposition. There was no s i g n i f i c a n t v a r i a t i o n between two s p i n e l g r a i n s analysed in each nodule (Appendix 1 and 2),nor was chemical v a r i a t i o n among s p i n e l s from three nodules. (Table 3-1): Al=1.319 to 1.729, Mg=0.742 to 0.789, Fe 2 +=0.213 to 0.265, Cr=0.266 to 0.647. In the Cr/(Cr+Al)x100 vs. Mg/(Mg+Fe 2*)xl00 p l o t ( F i g u r e 3-5), the nodule s p i n e l s l i e on the lower ( l e s s depleted) end of the Josephine P e r i d o t i t e t r e n d . Pressure and temperature estimates Pyroxene geothermometry and geobarometry techniques f o r u l t r a m a t i c parageneses (Wood and Banno, 1973; Wood, 1975; Mer c i e r and C a r t e r , 1975; M e r c i e r , 1976) are based on t h e o r e t i c a l d e r i v a t i o n s f o r s e t s of e q u i l i b r i u m r e a c t i o n s i n v o l v i n g e n s t a t i t e , d i o p s i d e and ah aluminous phase, e i t h e r s p i n e l or garnet. Based on w o l l a s t o n i t e s o l i d - s o l u t i o n i n d i o p s i d e and A l - c o n c e n t r a t i o n in c o - e x i s t i n g e n s t a t i t e , Mercier (1976) g e n e r a l i z e d the pyroxene techniques to d e r i v e both C r / T l 10 I 20 __1 30 i AO Diopside ' N ^ / • \ L U 4 ' \ I \ I I \ I I 1 \ II I \ s I \ 9 C \ o I I I I \ \ \ \ • KR2 \ \ ' \ \ I "--VKR1 Undeleted / § M , ' 6 L L , \ JL14V.-.BM55*--R35 8 8 39 90 91 92 93 Mg/(Mg+Fe)xl00 g. 3-4(b) Mg/(Mg+Fe)x100 vs. Cr/T1 p l o t of d l o p s i d e s 42 MO to •0 70 • •0 -Cr x 100 Cr + AI so 40 10 SO 10 100 60 40 Mg x 100 Mg + F . + + F1g. 3-5 Mg/(Mg+Fe++)x100 vs. Cr/(Cr+AI)x100 p l o t of s p i n e l ( J o s e p h i n e P e r i d o t i t e d a t a from D i c k , 1975) temperature and pressure on the b a s i s of a single-pyroxene a n a l y s i s , the composition of the c o - e x i s t i n g phases being i n f e r r e d from t h i s a n a l y s i s and from e m p i r i c a l l y determined p a r t i t i o n c o e f f i c i e n t s . T h i s method can be a p p l i e d to p a r t i a l l y a l t e r e d or r e e q u i l i b r a t e d f a c i e s and to xenocrysts, assuming o r i g i n a l e q u i l i b r i u m between two pyroxenes and s p i n e l or garnet. The method has been r e v i s e d by M e r c i e r (1980). 43 Temperature and p r e s s u r e estimates are independently obtained through the use of the g e n e r a l equations (Mercier, 1976): T = [AH (v'+v"lnK')-AH (v'+v"lnK')]/D a w w w w a a a P = [AH (RlnK'+AS )-AH (RlnK'+AS )]/D a w w w a a i n which, D = (RlnK'+AS ) (v ' + v" InK ' ) -•( RlnK' +AS )(v'+v"lnK') a a w w w w w a a a p e r t i n e n t thermodynamic parameters and the p a r t i t i o n c o e f f i c i e n t s K' and K' are given by M e r c i e r (1980) w a J M e r c i e r ' s r e f i n e d pyroxene thermobarometry (1980) has been used to c a l c u l a t e e q u i l i b r i u m temperature and pressure of B r i t i s h Columbia nodules and Josephine P e r i d o t i t e through the program "PGEOTH" p r o v i d e d by J.V. Ross. Data in Table 3-1 were used f o r the c a l c u l a t i o n . C a l c u l a t e d T, P, and depth are l i s t e d i n Table 3-4. The T, P and depth c a l c u l a t e d s e p e r a t e l y f o r d i o p s i d e and e n s t a t i t e do not agree: e n s t a t i t e c a l c u l a t i o n g i v e s s y s t e m a t i c a l l y higher v a l u e s than d i o p s i d e . Temperature, pressure and depth v a l u e s from J.V. Ross (Appendix 4) were d e r i v e d from data f o r i n d i v i d u a l a n a l y t i c a l p o i n t s . There i s l i k e w i s e a degree of i n c o n s i s t e n c y between d i o p s i d e and e n s t a t i t e . The i n c o n s i s t e n c y may be due to d i s e q u i l i b r i u m between d i o p s i d e and e n s t a t i t e or due to s i g n i f i c a n t d e v i a t i o n of p a r t i t i o n c o e f f i c i e n t s from those of M e r c i e r (1980). C o n s i d e r i n g the w e l l d e f i n e d m i n e r a l isochrons (see Chapter V ) , the i n c o n s i s t e n c y seems u n l i k e l y to be due to 44 T a b l e 3-4 C a l c u l a t e d T(°C), P(kb) and Depth(km) M e r c l e r (1980) Modi f i ed CPX OPX CPX OPX T P D T P 0 T I ? D T 1 P D KR#1 940 1 1 . 77 39.9 1006 16 . 75 55 .0 936 1 1 . 49 39 . 1 936 12 .02 40. . 7 KR#2 929 1 1 .49 39 . 1 1002 16 .82 55 . 2 975 14 .43 48 .0 974 14 . 88 49 . 3 LL#1 1004 13. 72 45 .8 1057 18 . 10 59 . 1 999 13 . 42 44 .9 998 14 .03 46 . 8 JL14 995 13 . 74 45.9 1089 20 . 18 65 . 4 995 13 . 76 45 .9 995 13 .64 45 . 6 JL15 1062 18 . 16 59 . 3 JL18 1025 17 . 18 56 .3 8M1 1 1093 13 . 37 44 .8 BM1S 940 9.81 34 .0 113 1 20. ,97 67 . 8 937 9 . 56 33 .2 939 7 . 92 28 . 2 BM55 1053 16.95 55 . 6 KR35 949 10.90 37 . 3 1 105 19 . 21 62 . 5 ' 947 10 . 77 36 .9 950 8 . 70 30. 6 LL14 1012 16.52 54 . 3 1068 19. 1 1 62. , 1 1009 16 . 34 53 8 1008 15 . 18 50. 3 J o s e p h i n e p e r i d o t l t e J28f 1000 11 . 34 38.6 12 15 20. 79 67 . 2 1005 1 1 .62 39. . 5 1002 7 .62 27 . 3 J871 1040 19.67 63.9 1 123 23 . 97 76 . 9 1042 19 . 80 64 . 2 104 1 18 . 38 60. 0 J120 1010 20. 46 66 . 3 998 18 . 79 61 . 2 1013 20 . 72 67 .0 101 1 19 . 72 G4 . 0 J114 1114 24 . 50 78, .5 J46h 1235 22 . 67 72 . 9 J46h 1 169 19. 27 62 , 6 d i s e q u i l i b r i u m between d i o p s i d e and e n s t a t i t e . In M e r c i e r ' s t h e r m o b a r o m e t e r , t h e p a r t i t i o n c o e f f i c i e n t K' f o r En and D i s o l i d - s o l u t i o n s w M g 2 S i 2 0 6 = M g 2 S i 2 0 6 D i ss En s s i s g i v e n by K; = ( X ^ ) d i / ( X ^ ) e n = ( i-2W d. )/(1 -2W e n) + + . where, W = Ca/(Ca+Mg+Mn+Fe ) and t h e f a c t o r 2 a r i s e s from t h e c o n s i d e r a t i o n of Fe s o l i d s o l u t i o n . By p l o t t i n g m i n e r a l d a t a i n W g n v s . 0.5-W d i, M e r c i e r q o t a v a l u e of W /(0.5-w,.)=0.333 f o r s p i n e l - f a c i e s . Thus ^ en d i f o r e n s t a t i t e , K' w=6.000W(1-2W) f o r d i o p s i d e , K w=(1-2W)/(0.667+0.667W). I f t h e r e i s a l a r g e d e v i a t i o n f r o m w e n / ( 0 . ) = 0 . 3 3 3 , t h e d i f f e r e n c e between c a l c u l a t e d f r o m d i o p s i d e and f r o m e n s t a t i t e w i l l be s i g n i f i c a n t . F o r example, f o r n o d u l e LL14, th e d i o p s i d e c a l c u l a t i o n g i v e s K w = 0 . 0 7 i 5 , but t h e e n s t a t i t e c a l c u l a t i o n g i v e s 45 K'=0.0989. T h i s d i f f e r e n c e i s the main source of the w i n c o n s i s t e n c y . When c o e x i s t i n g e n s t a t i t e and d i o p s i d e data are a v a i l a b l e , c a l c u l a t e d K'=(1-2W,.)/(1-2W ) w i l l be more w d i en r e l i a b l e . For example, f o r nodule LL14, K w=0.072. Thus M e r c i e r ' s s i n g l e pyroxene thermobarometer has been m o d i f i e d f o r t h i s study. When c o e x i s t i n g pyroxenes data are a v a i l b l e , we take K1 = (1-2W,.)/(1-2W ). Otherwise, we w d i en c a l c u l a t e , f o l l o w i n g M e r c i e r , IT =6. 000W( 1-2W) f o r e n s t a t i t e and K'=(l-2W)/(0.667+0.667W) f o r d i o p s i d e . The r e s u l t s w d e r i v e d by t h i s m o d i f i c a t i o n are a l s o l i s t e d i n Table 3-4. 46 IV. Rb-Sr ISOTOPE ANALYTICAL METHOD IV-1. Sample p r e p a r a t i o n (1 ). Nodules Only r e l a t i v e l y f r e s h nodules were s e l e c t e d f o r t h i s study. Small b a s a l t fragments adhering to the nodules were removed by hand p i c k i n g a f t e r i n i t i a l c r u s h i n g using a hammer. Next the same sample was reduced in a s t e e l mortar to l e s s than 16 mesh, and 5 gram samples were set a s i d e f o r whole rock a n a l y s i s . The 40-16 mesh f r a c t i o n of the remainder was used f o r m i n e r a l s e p a r a t i o n . The whole rock s p l i t was f u r t h e r crushed i n the s t e e l mortar to pass 40 mesh and then ground i n a motor d r i v e n agate mortar to l e s s than about 150 mesh. The i n t e r s t i t i a l m a t e r i a l i n u l t r a m a f i c rocks c o n t a i n s much higher Rb and Sr than the p r i s t i n e m i n e r a l s . T h i s m a t e r i a l must be completely removed from the s u r f a c e s of the m i n e r a l s i n order to get true chemical values f o r the m i n e r a l s . The procedure f o r doing t h i s i s : A f t e r washing with Q u a r t z 1 H 20, 20 grams of dry 40-16 mesh s i z e f r a c t i o n was allowed to stand f o r 6 hours i n 6N Quartz HC1 while heated to 80°C i n a pyrex beaker. A f t e r the r e s i d u e was washed with Quartz H 20 three times i t was d r i e d on a hot p l a t e . The HC1 and H 20 used i n t h i s c l e a n i n g process were d r i e d . The r e s u l t i n g c h l o r i d e s were used f o r 1 " Q u a r t z - " i s d e f i n e d i n s e c t i o n IV 2-(2). 47 " a c i d - l e a c h m a t e r i a l " a n a l y s e s . The a c i d - l e a c h m a t e r i a l weights of JL14, JL15, JL18, BM11, BM16, BM55, KR35, and LL14 were taken as the weight d i f f e r e n c e between the sample before and a f t e r the l e a c h i n g . The a c i d - l e a c h m a t e r i a l weights of KR1, KR2 and LL1 were d i r e c t l y weighed from d r i e d c h l o r i d e s . From the d r i e d leached sample 2 to 4 grams of o l i v i n e , orthopyroxene and c l i n o p y r o x e n e were hand p i c k e d under a b i n o c u l a r microscope. Only those g r a i n s with c l e a r s u r f a c e s and fre e from i n c l u s i o n s and e x s o l u t i o n l a m e l l a e were chosen f o r a n a l y s i s . Each m i n e r a l separate was then ground in a c l e a n agate mortar to 100-40 mesh and reexamined to ensure that no f i n e i n c l u s i o n s (e.g. magnetite and s p i n e l ) remained. The pure m i n e r a l separates ( >99.5% ) were leached with 6N Quartz HC1 i n an u l t r a s o n i c bath f o r 15 minutes and then p l a c e d on a hot p l a t e (80°C) i n small pyrex beakers f o r h a l f an hour to remove any contamination from h a n d l i n g d u r i n g hand p i c k i n g . The r e s i d u e s were washed with Quartz H 20 three times and d r i e d . The res i d u e s were then ground in the agate mortar to l e s s than 150 mesh in a laminar a i r flow hood. The agate mortar was washed with u l t r a p u r e acetone between samples. (2). Josephine P e r i d o t i t e Approximately 50 grams of each sample were processed through a jaw crusher and r o t a r y p u l v e r i z e r to g i v e l e s s than 40 mesh s t a r t i n g m a t e r i a l . The 80-40 mesh s i z e f r a c t i o n 48 was passed through a Carpco magnetic r o l l s e p arator to remove magnetite and i r o n (from the c r u s h e r s ) . D i f f e r e n t d e n s i t y f r a c t i o n s were seperated from a water-washed 80-40 mesh f r a c t i o n using methylene i o d i d e d i l u t e d by acetone. Four f r a c t i o n s of s u c c e s s i v e l y lower d e n s i t y were c o l l e c t e d . Examination under a b i n o c u l a r microscope i n d i c a t e d that the second f r a c t i o n was f r e e of s e r p e n t i n e , s p i n e l and other accessory m i n e r a l s . I t was used f o r f u r t h e r s e p a r a t i o n with a Franz magnetic s e p a r a t o r . The "non-magnetic" f r a c t i o n c o n s i s t e d mainly of c l i n o p y r o x e n e ; the "magnetic" f r a c t i o n , of o l i v i n e ; and the "weak magnetic" f r a c t i o n , orthopyroxene. Unwanted minerals i n the n e a r l y pure mineral separates were removed by hand p i c k i n g . The pure (>99%) m i n e r a l c o n c e n t r a t e s then went through the same l e a c h i n g and g r i n d i n g procedure as d e s c r i b e d f o r m i n e r a l separates from nodules. Evaporation and f i n a l g r i n d i n g procedures were c a r r i e d out i n a laminar flow hood to a v o i d contamination. IV-2. Chemical Procedures (1). Laminar flow hood The laminar flow hood was used f o r a l l a c i d e v a p orations and f i l a m e n t l o a d i n g to a v o i d contamination from the dust in the a i r . The blank improvement can been seen i n Tables 4-1 and 4-3 and F i g u r e s 4-3(a) and 4-3(b). 49 ( 2 ) . Reagents Because of low Rb and Sr c o n c e n t r a t i o n s i n u l t r a m a f i c r o cks, contamination from reagents used f o r sample d i s s o l u t i o n and column e l u t i o n has to be minimized. In order to reduce t h i s contamination, only G. F. Smith Vycor -double d i s t i l l e d HC10, and "Quartz"- and "2B"- reagents were used. "Quartz"- r e f e r s to reagents d i s t i l l e d i n a quartz g l a s s s t i l l . "2B"- r e f e r s to reagents d i s t i l l e d at s u b b o i l i n g temperature i n two-bottle t e f l o n s t i l l s . Quartz H 20: prepared by r e d i s t i l l i n g d i s t i l l e d H 20 i n a qua r t z g l a s s s t i l l . Rb blank i s 0.013 ± 0.003 ng/g, Sr blank i s 0.072 ± 0.002 ng/g. 6.2 N Quartz HC1: prepared by d i l u t i n g 'Baker analysed' reagent HC1 with an a p p r o p r i a t e q u a n t i t y of d i s t i l l e d H 20, then d i s t i l l e d in a quartz g l a s s s t i l l . Rb blank i s 0.020 ± 0.015 ng/g, Sr blank i s 0.64 ± 0.32 ng/g. 2.5 N Quartz HC1: prepared by d i l u t i n g 6.2 N Quartz HC1 with an a p p r o p r i a t e q u a n t i t y of Quartz H 20. The nomality was confirmed by 1N NaOH t i t r a t i o n . Rb blank i s 0.014 ± 0.010 ng/g, Sr blank i s 0.17 ± 0.02 ng/g. 1.5 N Quartz HC1: prepared by d i l u t i n g 6.2 N Quartz HC1 with a p p r o p r i a t e q u a n t i t y of Quartz H 20. The 1.5 N value was confirmed by 1 N NaOH t i t r a t i o n . 6.0 N Quartz HC1: prepared by d i l u t i n g 6.2 N Quartz HC1 with a p p r o p r i a t e q u a n t i t y of Quartz H 20. The 6.0 N value was confirmed by 1 N NaOH t i t r a t i o n . 50 2B HF: prepared by d i s t i l l i n g M a l l i n c k r o d t A n a l y t i c a l Reagent HF at s u b b o i l i n g temperature i n two-bottle t e f l o n s t i l l . Rb blank i s 0.051 ± 0.032 ng/g, Sr blank i s 0.27 ± 0.21 ng/g. HC10«: G. F. Smith Vycor - double d i s t i l l e d HClO« was used. Rb blank i s 0.020 ± 0.011 ng/g, Sr blank i s 0.39 ± 0.20 ng/g. A l l reagent blanks were determined by i s o t o p e d i l u t i o n . Rb and Sr s p i k e s were mixed with the reagent and d r i e d . 2.5 N HC1 was used to take up the p r e c i p i t a t e d materals and loaded i n t o a l a r g e c a t i o n r e s i n column for chemical s e p a r a t i o n . So a l l the Rb and Sr blanks r e p o r t e d here i n c l u d e large-column blanks. T a b l e 4-1 shows a l l the reagent blank measurements. From Ta b l e 4-1 we reach the f o l l o w i n g c o n c l u s i o n s : (a) . Two-bottle d i s t i l l a t i o n of HF reduces the Rb blank from an average value of 0.17 to 0.051 ng/g and Sr blank from an average value of 26 to 0.26 ng/g. (b) . Quartz d i s t i l l a t i o n of d i s t i l l e d H 20 reduces Rb blank from an average value of 0.056 to of 0.013 ng/g and Sr blank from an average value of 2.5 to of 0.072 ng/g. (c) . Using HC10„ d i r e c t l y from t e f l o n source b o t t l e (average Rb blank i s 0.020 ng/g and average Sr blank i s 0.39 ng/g) s i g n i f i c a n t l y improved the blanks f o r HClO f t. From the g l a s s dropper b o t t l e the average Rb blank i s 0.22 ng/g and average Sr blank i s 3.5 ng/g. T h i s i n d i c a t e d t hat HC10fl i n the dropper b o t t l e had been s i g n i f i c a n t l y contaminated. T a b l e 4-1 Reagent B l a n k s Reagent Date(Yr/Mo/Da) Rb b l a n k ( n g / g ) Sr bl a n k ( n g / g ) comment 84/6/13 0 .045 ± 0 .003 (6.15 0.40) Sr abnormal D1st11 l e d 84/6/13 0 .083 ± 0 .001 0.61 ± 0.07 H20 84/6/19 0 .040 ± 0 . 002 0. 63 0.04 av e r a g e 0 .056 ± 0 .024 0.62 ± 0.05 84/5/14 3 . 47 ± 0 .05 16.4 ± 11.6 * 84/7/13 0 .015 0 .000 0.07 ± 0.02 0-H20 84/7/13 0 .01 1 ± 0 .000 0.07 0.01 avg. of 7/13 0. .013 i 0. .003 0.07 ± 0.00 84/7/13 0 .030 i 0 .001 0. 95 ± 0.02 6.5 N 84/7/13 0. .009 ± 0 .OOO 0.31 0.03 average 0. .020 + 0. .015 0.63 0.45 84/5/14 8 .52 + 0 .09 2.65 ± 0. 75 * 2.5 N 84/7/13 0. .023 ± 0 .000 0. 15 ± 0.00 0-HC1 84/7/13 0. .006 ± 0. OOO 0.18 ± 0.01 avg. of 7/13 0. .014 0, .01 1 0.17 0.02 84/5/14 76 1 140 10 Reagent 84/6/13 0. .095 + 0 005 39 ± 4 HF 84/6/19 0. . 24 ± 0. .01 1 . 3 ± 0. 1 avg. 6/13-19 0. 17 ± 0. 10 26 18 84/5/14 3 . 72 0. .06 4.8 ± 2 . 5 84/6/13 0, .080 ± 0, .001 2B-HF 84/6/19 O. 057 i. 0. 010 0.4 1 0.03 84/7/27 0. 017 ± 0. 000 0.12 ± 0.01 avg.6/13-7/27 0. 051 ± 0. 032 0. 27 ± 0.2 1 84/5/14 9. 5 ± 0. 1 220 ± 140 84/6/13 0. 103 0. 003 7 . 2 ± 0.6 84/6/19 0. 42 0. 04 1 . 48 ± 0.04 84/7/27 0. 123 0. 001 1 . 70 0 0 2 HC104 avg.6/13-7/27 0. 22 ± 0. 18 3 . 5 i 3 . 2 84/8/2 0. 01 1 ± 0. 000 0. 20 ± 0.01 84/8/2 0. 032 ± 0. 000 0 . 59 ± 0.03 84/8/2 0. 018 0. 000 0. 39 ± 0.02 * * average of 8/2 0. 020 ± 0. 01 1 0. 39 ± 0. 20 coment: * - a c i d e v a p o r a t i o n i n laminar flow hood, p l a n c h e t t e e v a p o r a t i o n and f i l a m e n t l o a d i n g in open a i r . o t h e r w i s e a l l e v a p o r a t i o n and f i l a m e n t l o a d i n g i n laminar f l o w hood. ** - a p p l i e d to HC104, from t e f l o n s o u r c e b o t t l e , o t h e r w i s e from gl-ass dropper b o t t l e , a l l the b l a n k s went through l a r g e ion exchange columns, so "reagent b l a n k " i n c l u d e s l a r g e column bla n k . 52 (d) . There i s a s i g n i f i c a n t r e d u c t i o n i n the blank v a l u e s f o r a l l the reagents when the laminar flow hood was used f o r a l l evaporations and f i l a m e n t l o a d i n g . (3). Rb and Sr sp i k e s D i l u t e d 8 7 R b was used f o r Rb isotope d i l u t i o n a n a l y s i s . The measured 8 5 R b / 8 7 R b was 0.00809 ± 0.00004, g i v i n g 8 7Rb abundance of 99.20 ± 0.01% and 8 5 R b of 0.803 ± 0.004%. In order to determine the c o n c e n t r a t i o n of 8 7 R b spi k e , the spike was mixed with a weighed amount of standard RbCl s o l u t i o n (N.B.S. standard 984). A N.B.S.-type mass spectrometer was used to determine the is o t o p e composition of the mixture. The Rb s p i k e c o n c e n t r a t i o n was c a l c u l a t e d to be 0.01069 ± 0.00007 Mmoles Rb/gm. D i l u t e d 8 " S r (N.B.S. SRM 988) was used f o r Sr isotope d i l u t i o n a n a l y s i s . The measured Sr spike i s o t o p i c r a t i o s are given i n Table 4-2. The i s o t o p e r a t i o s used ( 8 6 S r / 8 f t S r = 0.00202 ±0.00001; 8 8 S r / 8 * S r = 0.01244 ± 0.00012 and 8 7 S r / 8 * S r = 0.00111 ±0.00005) were d e r i v e d from N.B.S. c e r t i f i c a t e ; 1984 and 1985 measurements and c o n s i d e r a t i o n of common Sr contamination. The c o n c e n t r a t i o n of the 8 < t S r spike was 0.01130 ± 0.00001 jumoles Sr/gm determined g r a v i m e t r i c l y when i t was f i r s t prepared i n Feburary of 1974. By r e p l i c a t e d c a l i b r a t i o n s using a standard Sr s o l u t i o n (N.B.S. standard 987), a c o n c e n t r a t i o n of 0.01130 Mmoles Sr/gm was determined (Maxwell, 1976). During the course of t h i s work r e p l i c a t e 53 T a b l e 4 - 2 I s o t o p l c c o m p o s i t i o n o f N . B . S . S r s p i k e S R M - 9 8 8 D a t e o f m e a s u r e m e n t 8 6 S r / 8 4 S r 8 8 S r / 8 4 S r 8 7 S r / 8 4 S r N . B . S . c e r t i f i c a t e o f a n a l y s i s 1 9 7 6 ( R . M a x w e l l ) 1 9 7 8 ( R . L . A . ) 1 9 8 4 ( R I A & M S ) 1 9 8 5 ( R L A & P . M i c h a e l ) 0 . 0 0 0 5 8 9 0 . 0 0 0 9 3 0 . 0 0 1 6 2 0 . 0 0 2 1 7 0 . 0 0 2 0 2 ± 0 . 0 0 0 0 1 0 . 0 0 0 3 8 6 0 . 0 0 2 9 0 . 0 0 8 6 0 . 0 1 3 7 4 0 . 0 1 2 4 4 ± 0 . 0 0 0 8 8 0 . 0 0 0 0 9 8 0 . 0 0 0 3 2 0 . 0 0 0 6 1 0 . 0 0 1 2 4 0 . 0 0 1 0 7 ± 0 . 0 0 0 1 0 c a l i b r a t i o n s of the 8 4 S r spike were done using the same standard as was used i n the i n i t i a l c a l i b r a t i o n s . The procedure f o r Sr s p i k e c a l i b r a t i o n was e s s e n t i a l l y the same as f o r Rb. C o n c e n t r a t i o n s of 0.011475 and 0.011533 Mmoles Sr/gm were given by the new c a l i b r a t i o n s . A value of 0.01150 ± 0.00003 Mmoles Sr/gm f o r 8 f t S r s p i k e c o n c e n t r a t i o n was used f o r the i s o t o p e d i l u t i o n c a l c u l a t i o n s d u r i n g t h i s work. Agreement with the o r i g i n a l c a l i b r a t i o n s i s good. The c o n c e n t r a t i o n d i f f e r e n c e l a r g e l y l i e s i n the gradual i n c r e a s e i n common Sr that has occured over ten years i n the storage f l a s k . ( 4 ) . Sample d i s s o l u t i o n ( a ) , sample d i g e s t i o n was c a r r i e d out i n a S a v i l e x t e f l o n d i s s o l u t i o n v e s s e l with t e f l o n screw cap. 200-300 mg of c l i n o p y r o x e n e or whole rock, and 400-500 mg orthopyroxene or o l i v i n e were weighed d i r e c t l y i n t o the v e s s e l on a M e t t l e r H 2o balance. The balance has a maximum s e n s i t i v i t y of 10 Mg. 8 7Rb and 8 f t S r spikes were f i r s t added to the v e s s e l v i a c a p i l l a r y tubes mounted i n the caps of t e f l o n s pike b o t t l e s , then the sample. The weights of sample and 54 sp i k e s were c a l c u l a t e d by d i f f e r e n c e . By o b s e r v i n g the spike e v a p o r a t i o n d u r i n g weighing, the p r e c i s i o n of a l l weighing in t h i s work was estimated to be ± 0.0001 gms(la). Normally a group of 10 samples p l u s blanks were processed at one time. (b) . A f t e r approximately 5 ml of 2B HF and 1 ml of HCIO, were added to the sample, the t e f l o n beakers were capped t i g h t l y and p l a c e d on a hot p l a t e at b o i l i n g temperature f o r at l e a s t 4 days. (c) . A f t e r d i g e s t i o n , the samples were evaporated to dryness i n a laminar flow hood and then allowed to c o o l . (d) . The samples were r e d i s s o l v e d i n 5 ml 2.5N Quartz HCl and c e n t r i f u g e d i n pyrex c e n t r i f u g e tubes f o r 4 minutes. The sample s o l u t i o n was immediately loaded onto ion exchange columns. (5) . Chemical s e p a r a t i o n Elements were i n i t i a l l y separated by u s i n g a l a r g e c a t i o n r e s i n column (20cm lon g , 1cm diameter, f i l l e d with 200-400 mesh AG 50W-X8 r e s i n ) . 2.5 N HCl was used f o r e l u t i o n . The Rb and Sr were c o l l e c t e d f o r mass spectrometer measurements or fut h e r p u r i f i c a t i o n , r e s p e c t i v e l y . The c a l i b r a t i o n of each column was c a r r i e d out i n three ways: ( a ) . 2 drops of r a d i o a c t i v e 8 9 S r t r a c e r was loaded i n t o the column. By using a Geiger counter B 9 S r c o n c e n t r a t i o n was determined i n s u c c e s s i v e 5 ml elu a n t a l i q u o t s , and the Sr 55 peak p o s i t i o n thus determined. (b) . 5 ml 2.5N HC1 s o l u t i o n c o n t a i n i n g 0.2 mg RbCl, 0.4 mg SrC0 3 and 0.8 mg CaC0 3 was loaded i n t o the column. By u s i n g an atomic a b s o r p t i o n spectrometer, Rb, Sr and Ca c o n c e n t r a t i o n s were determined in each 5 ml eluant a l i q u o t . In t h i s way the Rb, Sr and Ca e l u t i o n peaks were determined. The p o s i t i o n of the Sr peak determined by t h i s means agreed with that determined by 8 9 S r t r a c e r . (c) . 5 ml 2.5N H'Cl s o l u t i o n s of UBC l a b standard P-1 ( g r a n o d i o r i t e ) and of u l t r a m a f i c nodule were mixed with 0.1 mg RbCl, 0.2 mg SrC0 3 and 0.05 mg Sm 20 3, and then loaded i n t o the column r e s p e c t i v e l y . 100 ml 2.5N HC1 and then 50ml 6.ON HC1 were used for e l u t i o n . An atomic a b s o r p t i o n spectrometer was used to determine Rb, Sr, Mg and Sm c o n c e n t r a t i o n i n each 5 ml eluant a l i q u o t . The r e s u l t gave Rb, Sr, Mg and Sm e l u t i o n peaks. No s i g n i f i c a n t d i f f e r e n c e was found i n Rb, Sr, Mg and Sm e l u t i o n between P-1 and the u l t r a m a f i c sample. But the Rb peak was 2 ml and the Sr peak 3 ml e a r l i e r compared to the p o s i t i o n determined by l o a d i n g with pure elements. The e l u t i o n curves are shown in F i g u r e 4-1. The sample Rb and Sr, d u r i n g t h i s work, were c o l l e c t e d a c c o r d i n g to the "rock matrix" e l u t i o n r e s u l t s f o r each column. Despite the e f f e c t i v e chemical s e p a r a t i o n of Rb and Sr by going through the l a r g e column, Rb i n t e r f e r e n c e was s t i l l a s e r i o u s problem. S i g n i f i c a n t spike 8 7 R b would be added to S r I Rb C a S r 10 2 0 3 0 4 0 5 0 6 0 7 0 8 0 9 0 1 0 0 0 10 2 0 3 0 4 0 m i s 6 . 0 N Q u a r t z HC1 e l u t a n t m i s 2.5 N Q u a r t z HC1 e l u t a n t F i g . 4 - 1 E l u t i o n c u r v e s f o r M g . R b , C a , S r a n d Sm o n l a r g e c o l u m n 1. P e a k s w e r e d e t e r m i n e d d u r i n g I n i t i a l c o l u m n c a l i b r a t i o n b y c o l l e c t i n g t h e e l u a n t i n 5 ml a l i q u o t s . I i n d i c a t e s c a l i b r a t i o n b y 8 9 S r t r a c e r l o a d i n g ; I I i n d i c a t e s c a l i b r a t i o n b y l o a d i n g p u r e r e a g e n t s ; I I I i n d i c a t e s l o a d i n g o f e l e m e n t s i n a r o c k s o l u t i o n m a t r i x . R e l a t i v e e l e m e n t a l c o n c e n t r a t i o n s i n t h e a l i q u o t s w e r e m e a s u r e d b y a t o m i c a b s o p t t o n s p e c t r o m e t r y a n d G e l g e r c o u n t e r . F e c u r v e i s f r o m M a x w e l l ( 1 9 7 6 ) . U l 57 8 7 S r d u r i n g Sr isotope mass spectrometer measurement so as to g i v e an i n c o r r e c t 8 7 S r / 8 6 S r v a l u e . During mass spectrometer Sr measurement using program "UBCSSR", the 8 7Rb c o r r e c t i o n was done by measuring 8 5Rb and assuming a n a t u r a l Rb i s o t o p e r a t i o , i . e . 8 5Rb/ 8 7Rb=2.59265. But f o r 8 7Rb spik e d samples t h i s Rb c o r r e c t i o n would be i n c o r r e c t . In order to s o l v e t h i s problem, 10 small columns were prepared f o r a second Sr s e p a r a t i o n to e l i m i n a t e spike Rb i n t e r f e r e n c e . The small columns (8 cm long, 0.5 cm diameter, f i l l e d with 200-400 mesh AG 50W-X8 r e s i n ) were c a l i b r a t e d by l o a d i n g a s o l u t i o n of RbCl, SrC0 3 and CaC0 3 and e l u t i n g with 2.5 N , 2.0 N and 1.5 N Quartz HCl r e s p e c t i v e l y . An atomic a b s o r p t i o n spectrometer was used fo r Rb, Sr and Ca d e t e r m i n a t i o n i n each 2 ml eluant a l i q u o t . The e l u t i o n curves are shown in F i g u r e 4-2. 1.5 N Quartz HCl was used f o r second Sr column e l u t i o n d u r i n g t h i s work and Sr i s c o l l e c t e d from 12.5 to 20.0 ml. 8 7Rb i n t e r f e r e n c e on 8 7 S r was thus reduced to l e s s than 0.0009 and the Rb was of n e a r l y normal composition so 8 7 S r / 8 6 S r r a t i o s are r e l i a b l e to 4th decimal p l a c e . (6). Mass spectrometry Rb isotope measurement was done on a N.B.S.-type mass spectrometer with programmable magnetic f i e l d c o n t r o l and d i g i t a l data a q u i s i t i o n l i n k e d to a Hewlett-Packard HP85 computer. 58 Rb c« Sr 2 . 9 N Rb C a S r 2 . 0 N 1 .5 N 0 5 10 15 ml e l u t a n t F i g . 4 - 2 E l u t i o n c u r v e s f o r R b , C a a n d S r o n s m a l l c o l u m n s . P e a k s w e r e d e t e r m i n e d d u r i n g i n i t i a l c a l i b r a t i o n b y c o l l e c t i n g t h e e l u a n ' t i n 2 . 5 ml a l i q u o t s . R e l a t i v e e l e m e n t c o n c e n t r a t i o n m t h e a l i q u o t s w e r e m e a s u r e d b y a t o m i c a b s o p t l o n s p e c t r o m e t r y . 1 . 5 N Q -HC1 1 s s e l e c t e d f o r s e c o n d S r c o l u m n e l u t i o n a n d S r I s c o l l e c t e d f r o m 1 2 . 5 t o 2 0 m l . (a) . Single tantalum filaments mounted on N.B.S. filament blocks were baked out for 15 minutes under < 3.0 X 10~5 torr vacuum and at 3.2 amps current. (b) . One drop of sample, taken up in Quartz H20, was loaded on the filament ribbon at 1.5 amps current. (c) . The loaded filament was then heated to a d u l l red glow for 10 seconds. (d) . the filament was then loaded into the mass spectrometer. The sample analysis was only started when the vacuum in the mass spectrometer was less than 10"7 t o r r . This took about 2 hours by using rotary, vacsorb, and then ion pumps. (e) . The filament current was increased u n t i l the more intense Rb peak (usually 8 7Rb) was f i r s t detected on 30 mV 59 s c a l e . The s i g n a l was focused to maxmum i n t e n s i t y . Data were c o l l e c t e d on 100 mV or 300 mV s c a l e as i n d i v i d u a l b l o c k s . Using the. program "NBSRB2", w i t h i n each block 3 backgrounds followed by 4 p a i r s of 8 5 R b and 8 7Rb peaks were measured, then c a l c u l a t i o n s and s t a t i s t i c s were done and 8 5 R b / 8 7 R b r a t i o with 1a e r r o r was p r i n t e d . Blocks were repeated to achieve a c c e p t a b l e o v e r a l l p r e c i s i o n . Sr i s o t o p e measurement was done on a VG ISOMASS 54R mass spectrometer with a programmable magmatic f i e l d c o n t r o l and d i g i t a l data a c q u i s i t i o n l i n k e d to a Hewlett-Packard HP85 computer. (a) . S i n g l e tantalum f i l a m e n t s mounted on Cathodion f i l a m e n t beads were baked out i n the same way as Rb f i l a m e n t s . (b) . A t i n y b i t of milky T a 2 0 5 suspension was p l a c e d on the baked f i l a m e n t . (c) . Two drops of a sample, d i s s o l v e d in Quartz H 20, were d r i e d on the f i l a m e n t at 1.5 amps f o r 5 minutes, the second drop only being added a f t e r the f i r s t drop had d r i e d . (d) . The f i l a m e n t was heated to a red glow for 10 seconds. (e) . 6 f i l a m e n t s were mounted on the c a r o u s e l in the mass spectrometer. The source region was pumped down by r o t a r y and then T i s u b l i m a t i o n and ion pumps. A n a l y s i s was s t a r t e d only a f t e r the mass spectrometer source had been pumped to below 10" 6 mbar. 60 ( f ) . A n a l y s i s was completed as f o l l o w s : The f i l a m e n t c u r r e n t was i n c r e a s e d to about 2 amps, a f t e r the 8 5 R b peak was found and focused, the f i l a m e n t c u r r e n t was i n c r e a s e d to 3.0 to 3.2 amps u n t i l the 8 8 S r was detec t e d on X 1 0 0 0 s c a l e . The 8 8 S r s i g n a l was then focused to a maximum i n t e n s i t y . At t h i s stage, data was c o l l e c t e d on X100 s c a l e by using " s h o r t b l o c k " mode. Each "short block" c o n t a i n s background, 8 5Rb, 4 p a i r s of 8 7 S r and 8 6 S r , background, 8 5Rb, 4 p a i r s of 8 8 S r and 8 6 S r , f o l l o w e d by 4 p a i r s of 8 t t S r and 8 6 S r measurements. The computer then r e p o r t s the 8 7 S r / 8 6 S r and 8 " S r / 8 6 S r r a t i o s , normalized to 8 8 S r / 8 6 S r = 8.3752 and c o r r e c t e d f o r n a t u r a l Rb. A f t e r 4 to 6 b l o c k s , a summary was made and the f i l a m e n t c u r r e n t i n c r e a s e d to run on X10 s c a l e using "long b l o c k " mode. In each "long block", background, 8 5Rb, 5 p a i r s of 8 7 S r and 8 6 S r , background, and 8 5 R b bracket 5 p a i r s of 8 B S r and 8 6 S r measurements. T h i s i s f o l l o w e d by p r i n t o u t of r a t i o s and s t a t i s t i c s and then, o p t i o n a l l y , f u r t h e r measurement of 5 p a i r s of 8 < t S r and 8 6 S r and p r i n t o u t of the normalized 8 " S r / 8 S S r r a t i o s . A f t e r 10 to 15 "long b l o c k " measurements, a summary f o r 8 7 S r / 8 6 S r was done. Any block with 8 7Rb c o r r e c t i o n to 8 7 S r > 0.0009 or with a f o r 8 7 S r / B 6 S r > 0.0010 was r e j e c t e d . ( 7 ) . Blanks Low blanks were e s s e n t i a l f o r the de t e r m i n a t i o n of the extremely low c o n c e n t r a t i o n s of Rb and Sr i n mi n e r a l s of 61 u l t r a m a f i c rocks. During the course of t h i s work, 24 t o t a l Rb blanks and 30 t o t a l Sr blanks were measured. The r e s u l t s are given i n Table 4-3 and F i g u r e s 4-3 and 4-4. Comparisons of t o t a l Rb and Sr blanks with p r e v i o u s work i n t h i s lab and other labs are given i n T a b l e 4-4. A f t e r May of 1984, using laminar flow hood f o r a l l e v a p o r a t i o n s and f i l a m e n t l o a d i n g , using 2B HF, and t a k i n g HC10„ d i r e c t l y from i t s t e f l o n source b o t t l e f o r sample d i g e s t i o n , the Rb and Sr blanks were reduced by a f a c t o r of 10. Average t o t a l Rb blank was 0.26 ± 0.13 ng. Average t o t a l Sr blank was 3.3 ± 2.2 ng. Those v a l u e s are above the l e v e l s achieved i n the l u n a r - s a m p l e - o r i e n t e d c l e a n l a b o r a t o r i e s of C.I.T., U.C.S.D. and A.N.U. N e v e r t h e l e s s the UBC blank l e v e l s are comparable to the l e v e l of other good eart h - s a m p l e - o r i e n t e d l a b s , i . e . of Brueckner (1974, 1975), Basu (1978), Menzies & Murthy (1978) and Mengel et a l . (1984). The average t o t a l Rb and Sr blanks and blank 8 7 S r / 8 6 S r r a t i o (0.714 ± 0.016) were used f o r Rb and Sr blank c o r r e c t i o n s . The lowest c o n c e n t r a t i o n s of Rb and Sr f o r Josephine P e r i d o t i t e samples are 0.02 ppm Rb i n c l i n o p y r o x e n e and 0.12 ppm Sr i n o l i v i n e . The minimum q u a n t i t y of Rb from 300 mg of c l i n o p y r o x e n e i s 6 ng and Sr from 500 mg of o l i v i n e i s 60 ng. Thus the l a r g e s t blank c o r r e c t i o n s f o r Rb and Sr are about 5%. For the nodules, Rb and Sr blank c o r r e c t i o n s are l e s s than 1%. T a b l e 4-3 T o t a l B l a n k s Date Rb b l a n k s Sr b l a n k s 87Sr/86Sr comment yr/mo/da ng nanomoles ng nanomoles 84/4 3.3 0 .04 1 1 0 . 127 0 .718 * * 17 0 . 19 . 24 0 . 25 0 . 725 * 32 0 . 37 39 0 .41 0 .717 * 8 . 3 0 .097 8 0 .9 0 . 700 * 84/5/14 0.94 0 .011 7.0 0 .079 0 . 726 * * 6.8 O .078 o . 777 84/6/13 0.12 0 .0015 1 . 30 0 .015 0 . 700 * 0.27 0 .0032 2.8 0 .032 0 .700 * 9 . 1 0 . 10 0. . 708 * * 84/6/19 0.40 0 .0047 2.13 O .024 (O .68) * 0. 36 0 .0042 1 .09 0 .012 (0. .692) * 0. 27 0 .0031 7 . 1 0 .081 (0. .691 ) fc 0. 20 0 .0023 6 . 3 0 .072 0. .711 + * 0.27 0. .0031 2.2 0 .025 0. 701 * 5 . 8 0 .067 0. 718 * * 3.3 0 .038 0. 731 sma11 co1umn 84/7/5 0. 22 0 .0026 1 . 56 0 .018 0. . 752 • * 0. 39 0, ,0046 ( 106) * Sr abnorma1 84/7/18 0. 78 0 .009 (0 65) sma11 co1umn 3.64 0. .042 (0. 808 ) sma11 co1umn 84/7/27 ( 1 68) 3.98 0 .045 0. 709 * Rb abnorma1 O. 36 0. . 004 2 3 . 2 0 . 037 0. 705 * 84/8/2 0. 18 O. 0021 1.19 0. .018 0. 712 * 84/8/17 0. 44 0 .0052 7 . 2 0 .083 0. 708 * •* 0.45 0. .0052 3 . 87 0 .044 0. 706 * * 0. 24 0. 0029 3 . 1 0. .035 0. 705 * * 84/10/9 0. 33 0. 0038 1 . 6 0. 012 0. 716 * * 0. 49 0. 0057 1 . 1 0. 018 0. 7 14 84/12/19 0.11 0. 0013 2 . 1 0. 024 0. 738 + * 85/2/1 0.11 0. 0013 2 . 2 0. 025 0. 747 85/5/24 0.12 0. 0014 2 . 25 0. 026 0. 699 tt * 0.09 0. 0010 6.16 0. 070 0. 703 * * 0.12 0. 0014 1 . 55 0. 018 (0. 683) * * a v e r a g e 0. 26 0. 0031 3 . 3 0. 038 0. 7 14 abnormal blanks a f t e r 84/5/14 ±0.13 +0. 0015 ±2 . 2 ±0. 025 ±0. 016 exc1uded comment: * - s1ng1e column f o r Rb and Sr . ** - s i n g l e column f o r Rb, double column f o r Sr. B l a n k s i n 84/4: u s i n g o r d i n a r y HF and HC104 from d r o p p e r b o t t l e r , e v a p o r a t i o n i n open a i r . B l a n k s on 84/5/14: u s i n a 2B-HF and HC104 from d r o p p e r b o t t 1 e , e v a p o r a t i o n i n laminar flow hood. p l a n c h e t t e e v a p o r a t i o n and f i l a m e n t l o a d i n g in open a i r . B l a n k s a f t e r 84/5/14: u s i n g 2B-HF and HC104 from s o u r c e b o t t l e , o p e r a t i o n i n laminar flow hood. 84/4 84/5/14 84/6/13 84/6/19 84/7/05 t 84/7/18 o H > O H rr rt £L 84/7/27 cr ^ 84/8/02 D 84/8/17 0Q I 84/10/09 84/12/19 85/2/01 85/5/24 i ' i 1 i Range of p r e v i o u s Rb b l a n k s ' O J 84/4 84/5/14 84/6/13 84/6/19 84/7/05 84/7/18 84/7/27 -«-'./«/02 84/8/17 -84/10/09 84/12/19 |_ 85/2/01 85/524 ng Sr i 1 +-—i 1 « 1 — - i " 1— i 1 1 I i I - ' 1 * •4 * * 4 4 65 T a b l e 4-4- C o m p a n s l o n o f t o t a l b l a n k w i t h o t h e r l a b s D a t a s o u r c e L a b y e a r R b b l a n k ( n g ) S r b l a n k ( n g ) U B C 1 9 8 4 0 . 3 3 . 4 UBC 1 9 7 S 1 . 7 - 8 . 9 14 - 34 M i a m i U . 1974 4 - 1 0 10 - 7 0 U C L A 1 9 7 3 2 2 C . I . T . 1 9 7 3 0 . 0 2 0 . 2 ANU 1971 0 . 4 5 - 0 . 1 4 0 . 9 0 - 0 . 1 9 W A I T 1 9 7 0 10 100 L a m o n t 1 9 7 4 0 . 3 - 0 0 7 1 - 10 L a m o n t 1 9 7 3 0 . 3 - 0 . 0 7 1 U C S O 1 9 8 0 0 . 2 - 0 . 5 M i n e s o t a '1978 0 . 1 1 G . I . G . 1 9 8 4 0 . 1 2 O x f o r d P o l y t e c . 1 9 7 5 0 . 8 - 1 . 0 0 . 7 - 1 .4 C . I . T . 1984 0 . 1 U . P a r i s 1 9 7 8 0 . 0 1 5 - 0 . 0 5 9 0 . 0 4 5 - 0 . 1 1 7 T h i s w o r k M a x w e l l ( 1 9 7 6 ) S t e u b e r a t a l . ( 1 9 7 4 ) M a r k e t a l . ( 1 9 7 3 ) P a p a n a s t a s s l o u e t . a l . ( 1 9 7 3 ) C o m p s t o n e t a l . ( l 9 7 l ) D e L a e t e r e t a t . ( 1 9 7 0 ) B r u e c k n e r ( 1 9 7 4 ) B r u e c k n e r ( 1 9 7 5 ) C a r l s o n ( 1 9 8 0 ) M e n z t e s e t . a l . ( 1 9 7 8 ) B a s u ( 1 9 7 8 ) M e n g e l e t a l . ( 1 9 8 4 ) B u r w e l l ( 1 9 7 3 ) J a c o b s e n e t a l . ( l 9 8 4 ) 0 . 1 1 7 A l l e g r e e t a l . ( 1 9 8 2 ) S y n t h e t i c t o t a l b l a n k s , c a l c u l a t e d f r o m 5 ml 2B-HF, 1ml HC10, and 10 ml 2.5N H C l , a r e 0.42 ng Rb and 3.4 ng S r . The d i f f e r e n c e between c a l c u l a t e d and l o w e s t t o t a l b l a n k s must be what i s added i n column s t e p f o r r e a g e n t b l a n k s . S i n c e c a l c u l a t e d b l a n k s a r e g r e a t e r t h a n o b s e r v e d b l a n k s by a s m a l l amount t h e r e must be a s m a l l column b l a n k i n c l u d e d i n t h e r e a g e n t b l a n k s . T h i s means t h e " t o t a l b l a n k s " a r e m a i n l y f r o m r e a g e n t s , t h e column b l a n k i s l e s s t h a n 0.2 ng Rb and 1.0 ng S r . ( 8 ) . D a t a r e d u c t i o n Rb and Sr d a t a r e d u c t i o n was done by a FORTRAN program "RBSR" r e v i s e d from BASIC p r o g r a m s "RBSPK3" and "SRSPK3" ( A p p e n d i x 5 ) . The t o t a l e r r o r ( l a ) , b a s e d on a l l u n c e r t a i n t i e s c a r r i e d t h r o u g h t h e c a l c u l a t i o n i s g i v e n by AF = • K l l A X . ) 2 , (Nunes, 1980) O A • 1 66 where AF i s the f i n a l e r r o r , AX^ i s the e r r o r i n the i t h v a r i a b l e , and F = F(X,,X2,...,X ) The computer performs the p a r t i a l d i f f e r e n t i a t i o n f o r each v a r i a b l e : •gjj ^  = F ( X l f . . . X ^ +AX^ , . . . X^) - F(X 1,...X^,... X^ ) . A l l e r r o r s l i s t e d in t a b l e s , t e x t , or diagrams in t h i s t h e s i s a r e - l a or standard e r r o r of the mean f o r averaged numbers. (a) .Rb data r e d u c t i o n Rb mmoles = C -W •(R • P 8 7 - P 8 5 ) / ( P 8 5 - R -P 8 7) sp sp m t t s m s Rb(Aim o l e s / g m ) s a m p l e = [ Rb(.umoles) - Rb blank (umoles)]/(sample weight) Rb ( P P m ) s a m p l e = Rb(M m o l e s / g m ) s a m p l e . a t o m i c weight of Rb, where R = measured 8 5 R b / B 7 R b r a t i o , m P 8 7 = % abundance of 8 7Rb i n s p i k e . P 8 5 = % abundance of 8 5Rb i n s p i k e . P 8 7 = % n a t u r a l abundance of 8 7Rb. s P 8 S = % n a t u r a l abundance of 8 5Rb. s C gp = spike c o n c e n t r a t i o n (/umoles/gm) . = spike weight (grams). (b) . Sr data r e d u c t i o n 8 8 S r / 8 6 S r r a t i o was normalized to the n a t u r a l 8 8 S r / 8 6 S r r a t i o of 8.3752 du r i n g data c o l l e c t i o n . However 8 < t S r spike c o n t a i n s 8 8 S r and 8 6 S r i n a p r o p o r t i o n s i g n i f i c a n t l y d i f f e r e n t from the n a t u r a l 8 8 S r / 8 6 S r r a t i o . To o b t a i n t r u e 8 4 S r / 8 6 S r and 8 7 S r / 8 6 S r r a t i o s of the sample-spike mixture, 67 the 8 8 S r / 8 6 S r r a t i o was renormalized i t e r a t i v e l y by a f a c t o r d e r i v e d from ( 8 8 S r / 8 6 S r ) , / ( 8 8 S r / 8 6 S r ) m r a t i o . The C a 1 C IT163 S i t e r a t i o n was stopped when [ ( 8 8 S r / B 6 S r ) c a l c / ( 8 8 S r / 8 6 S r ) m e a s ] i -[ ( B 8 S r / 8 6 S r ) / ( 8 8 S r / 8 6 S r ) ], < 0.00000l. c a l c meas i-1 Sr c o n c e n t r a t i o n was then c a l c u l a t e d u s i n g formulae s i m i l a r to those used f o r Rb. The t o t a l e r r o r f o r Sr was e v a l u a t e d in the same manner as for Rb. A common Sr atomic weight of 87.62 was used f o r Sr ppm c a l c u l a t i o n . (9) . N.B.S. standard SRM987 measurements The value f o r the N.B.S. standard SRM987 8 7 S r / 8 6 S r i s taken to be 0.71020, an average of the v a l u e s reported.by s e v e r a l l a b s . A c t u a l measurements during t h i s work gave an average value of 8 7 S r / 8 6 S r = 0.71017 ± 0.00004 (Table 4-5). A c c o r d i n g l y , a l l the 8 7 S r / 8 6 S r r a t i o s r e p o r t e d i n t h i s work have been a d j u s t e d by adding a f a c t o r of 0.00003. (10) . Isochron c a l c u l a t i o n and p l o t A r e v i s e d YORK REGRESSION program was used for Rb-Sr i s o c h r o n slope, i n t e r c e p t and the date c a l c u l a t i o n (Appendix 6-a). 8 7 R b / 8 6 S r and 8 7 S r / 8 6 S r and t h e i r one sigma e r r o r s were read from the output of data r e d u c t i o n program "RBSR". Sample data p o i n t s with one sigma e r r o r bars were p l o t e d by u s i n g a FORTRAN program "PLRBSR" (Appendix 6~b) . T a b l e 4-5 87Sr/86Sr r a t i o s of N.B.S. SRM-987 ( K . S c o t t , p e r s . comm., 1985) Date(yr/mo/da) No. of B l o c k s 87Sr/86Sr + /-1984/8/8 6 0. 71002 0.00012 15 0. 71016 0.00010 15 0. 70967 0.00018 9 0. 71007 0.00009 13 0. .71032 0.00005 18 0 71026 0.00009 1984/9/1 1 16 0. .71028 0.00009 18 0. 71017 0.00007 16 0. 71030 0.00008 17 0. 71017 0.00009 16 0. 70999 0.00013 15 0. 71017 0.00013 1984/10/ 10 34 0. 71022 0.00006 1984/1 1/12 40 0. 71018 0.00012 1985/1/3 18 0. 71017 0.00007 18 0. 7 1007 0.00005 19 0. 71007 0.00005 19 0. .71021 0.00005 16 0. 71014 0.00004 18 O. 71023 0.00005 1985/3/29 9 . 0. 7 1013 0.00004 10 0. 71020 0.00007 1985/4/15 18 0. 71022 0.00006 16 0. 7 1017 0.00003 18 0. 71018 0.00002 19 o. 71020 0.00002 1985/5/22 17 0. 71019 O.00005 19 0. 7 1022 0.00006 19 0. 71015 0.00005 18 0. 71014 0.00004 17 0. 7 1023 0.00003 18 0. 7 102 1 0.00003 Average v a l u e = 0.71017 +/- 0.00004 weighted by number of a n a l y s e s and I n d i v i d u a l e r r o r s . 69 V. Rb-Sr ISOTOPE RESULTS V-1. Nodules and host b a s a l t s O l i v i n e , orthopyroxene and c l i n o p y r o x e n e mineral s e p a r a t e s , whole rock, and a c i d l e a c h m a t e r i a l from 12 nodules have been analysed f o r Rb and Sr c o n c e n t r a t i o n and Sr i s o t o p e composition. Of these, 4 nodules are from Jacques Lake, 3 from Big Timothy Mountain, 3 from West K e t t l e R i v e r , and 2 from L a s s i e Lake. Eleven host b a s a l t s were a l s o a n a l y s e d (Table 5-1). Some samples have been r e p e a t e d l y a n a l y s e d d u r i n g t h i s work. The r e p r o d u c i b i l i t y f o r Rb i s 1-2%, f o r Sr about 5%, for 8 7 S r / 8 6 S r 0.0005, and f o r 8 7 R b / 8 6 S r <6% (Appendix 7). For these samples, weighted mean values are used f o r f u r t h e r d i s c u s s i o n , the mean value u n c e r t a i n t y was c a l c u l a t e d by Nunes' equation (see I V - 2 - ( 8 ) ) . A number of mineral i s o c h r o n s are d e f i n e d . (1) . Jacques Lake Jacques Lake nodule (JL1, JL14, JL15 and JL18) mineral i s o c h r o n s are shown on F i g u r e s 5-1, 5-2, 5-3 and 5-4. The data are l i s t e d i n Table 5-2. (2) . Big Timothy Mountain Big Timothy Mountain nodule (BM11, BM16 and BM55) mine r a l isochrons are shown on F i g u r e s 5-5, 5-6, and 5-7. The data are l i s t e d i n Table 5-3. (3) . West K e t t l e R i v er 70 West K e t t l e River nodule (KR1, KR2, and KR35) mi n e r a l i s o c h r o n s are shown on F i g u r e s 5-8, 5-9, and 5-10. The data are l i s t e d i n Table 5-4. (4). L a s s i e Lake L a s s i e Lake nodule (LL1 and LL14) mineral isochrons are shown on F i g u r e s 5-11, and 5-12. The data are l i s t e d i n Table 5-5. V-2. Josephine P e r i d o t i t e M i n e r a l separates from 4 samples (JM5, JM14, JM15 and JM2) have been analysed. The data are l i s t e d i n Table 5-6. M i n e r a l i s o c h r o n s are shown on F i g u r e 5-13, 5-14, and 5-15. For comparison, Table 5-7. the mineral isochrons are summarized i n 71 T a b l e 5 - 1 R b - S r d a t a o f h o s t a n d a s s o c i a t e d b a s a l t s S a m p l e s R b ppm */- S r ppm +/- 8 7 S r / 8 6 S r +/- 8 7 R b / 8 6 S r + / -J L 1 4 B A S T 1 2 . 7 0 . 1 1 2 9 7 16 0 . 7 0 2 5 4 0 0 0 0 1 4 0 . 0 2 8 0 . 0 0 1 BM11 B A S T 5 4 . 9 1 . 8 1514 51 0 . 7 0 2 6 4 0 . 0 0 0 1 0 0 . 105 0 . 0 0 5 B M 5 5 B A S T 4 5 . 5 2 . 8 1 2 7 6 3 3 0 . . 7 0 2 7 2 0 . . 0 0 0 0 6 0 . 103 0 . 0 0 7 BM26 B A S T 6 2 . 1 0 . 1 1 3 0 3 6 0 . 7 0 2 6 9 0 . 0 0 0 0 4 0 . 138 0 . 0 0 1 KR B - 1 1 7 . 1 0 . 5 8 5 9 19 0 . 7 0 3 1 8 0 . 0 0 0 0 9 0 . 0 5 8 0 . 0 0 1 KR B - 2 1 7 . 2 0 . 5 7 1 2 4 0 . , 7 0 3 6 0 0 . . 0 0 0 1 4 0 . 0 7 0 0 . 0 0 1 KR B - 3 1 7 . 5 0 . 2 6 4 2 19 0 . 7 0 2 9 1 0 . . 0 0 0 0 5 0 . 0 7 9 0 . 0 0 2 KR B - 4 3 0 . 4 0 . 6 9 5 1 9 0 . . 7 0 2 8 9 0 . 0 0 0 1 4 0 . 0 9 2 0 , . 0 0 1 K R 3 5 B A S T 21 . 5 1 . 6 8 4 2 2 3 0 . 7 0 2 6 2 0 . 0 0 0 1 2 0 . 0 7 4 0 . . 0 0 6 L L 1 B A S T 31 . 8 0 . 4 8 4 0 8 0 . 7 0 3 3 0 0 . 0 0 0 1 1 0 . 110 0 . . 0 0 1 L L 1 4 B A S T 1 8 . 5 0 . 8 7 0 2 34 0 . 7 0 2 3 8 0 . 0 O O 0 5 0 . 0 7 6 0 . 0 0 5 T a b l e 5 - 2 R b - S r i s o t o p e d a t a o f J a c q u e s L a k e n o d u l e s S a m p l e s Rb ppm + / - S r ppm + / - 8 7 S r / 8 6 S r + / - 8 7 R b / 8 6 S r + / -J L 1 8 A c i d l e a c h 1, 2 2 0 . . 0 2 7 8 . 9 0 , 8 0 . 7 0 2 9 0 . 0 0 0 3 0 , . 0 4 4 7 0 . 0 0 0 7 W h o l e r o c k 0 . 2 5 2 0 . . 0 0 1 3 8 . . 5 0 . 3 0 . 7 0 2 4 0 , . 0 0 0 2 0 . , 0 1 9 1 0 . 0 0 0 2 S y n . w r 0 . . 2 0 8 0 , . 0 0 1 4 0 .6 0 . 1 0 . 7 0 2 6 0 0O01 o , , 0 1 4 8 0 . 0 0 0 1 0 1 o p s 1 d e 0 . . 3 4 8 0 . . 0 0 3 2 3 8 . 7 0 . 9 0 . , 7 0 2 6 0 . 0 0 0 1 0 . . 0 0 4 2 1 0 . 0 0 0 0 4 E n s t a t 1 t e 0 . 2 5 9 0 . 0 0 2 4 . 2 0 0 . 0 2 0 . 7 0 3 4 0 , 0 O 0 4 0 , 178 0 . 0 0 2 0 1 1 v 1 n e 0 . , 1 5 3 0 . 0 0 1 2 . 3 2 0 .01 0 . 7 0 3 6 0 . 0 0 0 6 0 , . 191 0 . 0 0 2 J L 1 5 A c i d l e a c h 0 . . 5 4 6 O. . 0 0 5 7 . . 6 5 0 . . 0 2 0 . 7 0 3 0 0 . 0 0 0 4 0 , . 2 0 6 0 , . 0 0 2 W h o l e r o c k 0 . 0 9 5 8 0 . . 0 0 0 7 8 . 9 5 0 , . 0 3 0 . 7 0 2 9 0 , . 0 0 0 1 0 , . 0 3 1 0 0 . 0 0 0 3 S y n . w r 0 . , 161 0 . . 0 0 1 9 . 5 8 0 . 0 5 0 . 7 0 2 9 0 . . 0 0 0 1 0 . , 0 4 8 5 0 . 0 0 0 4 D i o p s i d e 0 . . 2 8 1 0 . . 0 0 3 5 4 . 3 0 . 3 0 . 7 0 2 6 0 , . 0 0 0 1 0 0 1 5 0 0 . 0 0 0 2 E n s t a t 1 t e 0 . 2 6 0 0 . 0 0 2 2. . 7 6 0 . ,01 0 . 7 0 5 1 0 . 0 0 0 9 0 . 2 7 3 0 . 0 0 3 01 1 v 1 n e I I \ A 0 . 0 8 4 2 O. . 0 0 0 9 0 . 3 2 5 0 , O 0 7 0 . 7 0 8 6 0 , 0 0 0 4 0 . , 7 4 9 0 . 0 1 7 U L 1 4 A c i d l e a c h 1. 7 6 0 . . 0 3 31 . . 7 0 , , 1 0 . 7 0 3 1 0 . 0 0 0 4 0 . 161 0 . 0 0 3 W h o l e r o c k 0 . 179 0 . . 0 0 1 8 . 4 4 0 , 0 4 0 . 7 0 3 0 0 , . 0 0 0 3 0 . 0 6 1 3 0 , . 0 0 0 5 S y n . w r 0 . 146 0 . , 0 0 1 6 8 2 0 , 0 2 0 . 7 0 2 8 0 , 0 0 0 1 0 . 0 6 1 9 0 , 0 0 0 1 D1 o p s 1 d e 0 . . 1 5 4 0 . . 0 0 1 3 2 . 1 0 . . 1 0 . 7 0 2 5 0 , . 0 0 0 1 0 . 0 1 3 9 0 . 0O01 E n s t a t 1 t e 0 . 191 0 . . 0 0 2 1 . 2 6 0 . ,01 0 . 7 0 5 1 0 . 0 0 0 5 0 . 4 3 8 0 . , 0 0 5 01 1 v 1 n e 11 4 0 . . 104 0 . , 0 0 1 0 . 6 2 4 0 . 0 0 5 0 . 7 0 5 6 0 . , 0 0 0 4 5 0 . 4 8 3 0 . , 0 0 5 O L l S y n . w r 0 . 0 9 1 2 0 . 0 0 0 2 13 , 2 0 . , 1 0 . 7 0 3 0 0 . 0 O 0 2 0 . 0 2 0 0 0 . 0 0 0 2 D 1 o p s 1 d e 0 . . 1 2 5 0 . 0 0 2 7 6 . 5 0 . ,4 0 . 7 0 2 9 0 . . 0 0 0 2 0 . 0 0 4 7 5 0 . , 0 0 0 0 8 E n s t a t 1 t e 0 . 0 1 9 1 0 . 0 0 0 6 2. 81 0 . . 0 2 0 . 7 0 2 9 0 . 0 0 0 2 0 . 0 1 9 7 0 . 0 0 0 6 0 1 1 v i n e 0 . , 1 16 0 . . 0 0 1 0 . 3 4 4 0 . , 0 0 7 0 . 7 1 0 6 0 , 0 O 0 6 0 . 9 7 7 0 . 0 2 1 72 T a b l e 5 - 3 R b - S r I s o t o p e d a t a o f B i g T i m o t h y M o u n t a i n n o d u l e s S a m p l e s Rb ppm + / - S r ppm + / - 8 7 S r / 8 6 S r + / - 8 7 R b / 8 S S r + / -BM1 1 A d d l e a c h 2 . 7 9 0 . 0 6 3 4 1 1 . 2 5 0 . 0 3 0 . . 7 0 3 3 0 . 0 0 0 1 0 , . 7 1 8 0 , 0 1 6 W h o l e r o c k 1 . . 13 0 .01 25 .6 0 . 2 0 . . 7 0 2 8 0 . 0 0 0 1 0 . , 128 0 . , 0 0 2 S y n . wr 0 . . 4 1 0 0 . 0 0 2 9 . 0 6 0 . 0 2 0 . 7 0 3 3 0 , . 0 0 0 1 0 . , 1 3 1 0 . 0 0 1 D i o p s i d e 0 . . 6 0 9 0 . 0 0 5 54 . 7 0 .2 0 . . 7 0 2 9 0 . 0 0 0 1 0 , . 0 3 2 2 0 , , 0 0 0 3 E n s t a t 1 t e 0 . . 9 3 6 0 . 0 0 7 10 . . 4 0 0 . . 0 3 0 . . 7 0 3 6 0 . 0 0 0 4 0 . . 2 6 0 0 . , 0 0 2 0 1 1 v t n e 0 . , 2 3 2 0 . 0 0 2 3 . 5 2 0 . . 0 2 0 . . 7 0 3 6 0 . 0 0 0 2 0 . 191 0 , , 0 0 2 BM16 A d d l e a c h 0 . . 7 1 6 0 . 0 0 9 3 . 6 6 0 .01 0 . , 7 0 4 4 0 . 0 0 0 2 0 . 5 6 5 0 . . 0 0 7 W h o l e r o c k 0 . . 2 8 0 0 . 0 0 6 4 .61 0 . 0 2 0 . , 7 0 3 5 0 . 0 0 0 1 0 . 176 0 . 0 0 4 S y n . wr 0 . . 1 1 3 0 . 0 0 1 3 . 4 9 0 , .01 0 . 7 0 3 9 0 . . 0 0 0 5 0 , . 0 9 3 2 0 . . 0 0 0 6 D i o p s i d e 0 . 160 0 . . 0 0 1 1 0 . , 2 5 0 . . 0 3 0 . 7 0 2 7 0 , , 0 0 0 5 0 . , 0 4 5 1 0 . . 0 0 0 4 E n s t a t 1 t e 0 . . 0 7 3 0 0 . . 0OO6 0 . 4 0 8 0 , . 0 0 8 0 . , 7 1 5 7 0 . 0 0 0 9 0 , . 5 1 9 0 . 0 1 1 0 1 i v l n e 0 . 102 0 . . 0 0 1 0 , , 4 5 7 0 . . 0 0 7 0 . 7 1 5 3 0 . 0 0 0 4 0 . . 6 4 1 0 . . 0 1 1 BM55 A c i d l e a c h 2 . 84 0 . . 0 6 1 0 . . 2 5 0 , . 0 3 0 . 7 0 3 3 0 . 0 0 0 2 0 . . 8 0 2 0 . . 0 1 6 W h o l e r o c k 0 . 3 2 6 0 . , 0 1 0 1 1 . . 7 0 , .3 0 . 7 0 2 7 0 , . 0 0 0 1 0 . 0 8 1 8 0 . . 0 0 1 5 S y n . wr 0 . 159 0 , . 0 0 1 1 0 . . 7 3 0 , . 0 2 0 . 7 0 3 5 0 , . 0 0 0 2 0 , . 0 4 2 9 0 . . 0 0 0 2 D i o p s i d e 0 . 140 0 . . 0 0 1 33 . , 4 5 0 . . 0 7 0 . 7 0 3 3 0 . . 0 0 0 2 0 . ,01 19 0 . . 0 0 0 1 E n s t a t 1 t e 0 . 2 5 2 0 . . 0 0 1 0 . , 7 4 9 0 . 0 0 5 0 . 7 0 8 6 0 , , 0 0 0 3 0 . 9 7 5 0 . , 0 0 8 01 W i n e 0 . 0 7 0 1 0 . . 0 0 0 4 0 , 2 6 0 0 . . 0 0 5 0 . 7 0 8 4 0 , . 0 0 0 5 0 . . 8 2 6 0 0 2 0 T a b l e 5 - 4 R b - S r i s o t o p e d a t a o f W e s t K e t t l e R i v e r n o d u l e s S a m p l e s Rb ppm + / - S r ppm + / - 8 7 S r / 8 6 S r + / - 8 7 R b / 8 6 S r + / -K R 3 5 A c i d l e a c h 0 . . 2 5 3 0 . 0 0 3 4 . 2 8 0 .01 0 , 7 0 5 3 0 . 0 O 0 1 0 . 171 0 . 0 0 2 W h o l e r o c k 0 . . 125 0 . 0 0 1 1 0 . . 5 3 0 . 0 9 0 , . 7 0 2 2 0 . 0 0 0 1 0 . 0 3 4 3 0 .O0O4 S y n . wr 0 , , 158 0 . 0 0 1 9 . , 3 9 0 . 0 4 0 , 7 0 2 9 0 . O 0 0 2 0 . 0 4 8 6 0 0OO3 D i o p s i d e 0 . 2 7 8 0 . 0 0 2 5 5 . . 6 0 .2 0 , , 7 0 2 2 0 . 0 0 0 3 0 . 0 1 4 4 0 . 0 0 0 1 E n s t a t i t e 0 . . 192 0 . 0 0 2 0 . , 9 3 1 0 . 0 5 4 0 , , 7 1 4 0 0 . 0 0 0 3 0 . 5 9 7 0 . 0 3 5 0 1 1 v 1 n e KR 1 0 . , 1 0 0 0 , . 0 0 1 0 . . 3 6 9 0 . 0 0 8 0 . 7 1 9 7 0 , . 0 0 0 4 0 . . 7 9 5 0 , . 0 1 8 A d d l e a c h 0 . . 2 9 3 0 . 0 0 2 1 . 4 7 5 0 , . 0 0 7 0 . , 7 0 6 7 0 . . 0 0 0 6 0 . . 5 7 4 0 , . 0 0 5 W h o l e r o c k 0 . , 3 8 5 0 , . 0 0 5 1 4 , 3 3 0 . , 0 3 0 . 7 0 4 0 0 . . 0 0 0 2 0 . . 2 6 1 0 . , 0 0 4 S y n . wr 0 . , 1 1 1 0 , 0 0 1 2 . 8 5 0 . . 0 2 0 . 7 0 3 7 0 . 0 0 0 2 0 . . 1 1 3 0 , , 0 0 1 D1 o p s 1 d e 0 . , 149 0 . 0 0 3 24 . 5 0 . . 1 0 . 7 0 3 1 0 . , 0 0 0 2 0 . . 0 1 7 6 0 . OO04 E n s t a t i t e 0 . 139 0 . , 0 0 1 0 . 2 8 8 0 . , 0 0 9 0 . 7 1 4 7 0 , . 0 0 0 2 1 . 4 0 0 . . 04 01 W i n e I / O o 0 . 0 9 9 4 0 . 0 0 0 8 0 . 145 0 . 0 0 8 0 . 7 1 6 2 O . 0 0 0 3 1, . 9 9 0 . 1 1 r x K ^ A c i d l e a c h 0 . 164 0 . . 0 0 1 6 . 16 0 . 0 3 0 . 7 0 5 5 0 . . 0 0 0 6 0 , . 0 7 6 8 0 . 0 0 0 8 W h o l e r o c k 0 . 2 7 2 0 . , 0 0 2 9 . 41 0 . , 0 3 0 . 7 0 3 7 0 . , 0 0 0 1 0 , , 0 8 3 7 0 . 0 0 0 7 S y n . w r O . 0 9 8 2 0 . 0 0 0 5 0 . 761 0 . 0 0 6 0 . 7 0 5 8 0 . 0 0 0 3 0 . , 3 7 3 0 . 0 0 4 D 1 o p s 1 d e 0 . 162 0 . . 0 0 3 9 . 31 0 . 0 3 0 . 7 0 3 2 0 . , 0 0 0 3 0 , , 0 5 0 2 0 . 0 0 0 8 E n s t a t i t e 0 . 122 0 . 0 0 1 0 . 4 1 6 0 . 0 0 9 0 . 7 1 2 3 0 . 0 0 0 6 0 . 8 4 8 0 . 0 2 0 0 1 1 v 1 n e 0 . 0 7 9 7 0 . 0 O 0 7 0 . 112 0 . 0 0 8 o . 7 1 4 2 0 . 0 0 0 1 2 . 0 6 0 . 15 T a b l e 5 - 5 R b - S r I s o t o p e d a t a o f L a s s i e L a k e n o d u l e s S a m p l e s Rb ppm + / - S r ppm + / - 8 7 S r / 8 6 S r + / - 8 7 R b / 8 6 S r + / -L L 1 A d d l e a c h 2 . 8 7 0 . 0 2 5 6 . 3 0 . 2 0 . 7 0 4 5 0 . 0 0 0 3 0 . 147 0 . 0 0 1 W h o l e r o c k 6 . 0 5 0 . 13 51 . 1 1 . 3 0 . 7 0 3 6 0 . 0 0 0 2 0 . 3 4 2 0 . 0 1 1 S y n . wr 0 . 9 5 7 0 . . 0 0 6 16 , 9 0 . . 1 0 . . 7 0 3 1 0 . . 0 0 0 2 0 . 164 0 , . 0 0 1 D i o p s i d e 3 . . 4 7 0 . . 0 3 9 8 . . 5 0 , ,4 0 . 7 0 3 0 0 , , 0 0 0 2 0 . . 102 0 , . 0 0 1 E n s t a t 1 t e 1 . . 0 5 0 . 01 2, 9 3 0 . . 0 2 0 . . 7 0 4 3 0 . . 0 0 0 1 1 . , 0 2 0 .01 01 1 v 1 n e 0 , . 2 7 4 0 . , 0 0 2 0 , . 7 9 8 0 . 0 0 8 0 , . 7 0 4 7 . 0 . . 0 0 0 4 0 . 9 9 5 0 . 0 1 3 L L 1 4 A c i d l e a c h 3 . 2 4 0 . , 13 41 , . 0 0 . 6 0 . 7 0 4 7 0 . . 0 0 0 2 0 . , 2 3 5 0 . 0 0 4 W h o l e r o c k 0 . 7 6 9 0 . . 0 0 7 8 . 77 0 . 0 4 0 . 7 0 3 7 0 . . 0 0 0 1 0 . . 2 5 4 0 . 0 0 3 S y n . w r 0 . 197 0 . . 0 0 1 10 . 7 9 0 , . 0 3 0 . 7 0 4 2 0 . . 0 0 0 2 0 . 0 5 2 8 0 . 0 0 0 4 D 1 o p s 1 d e 0 . . 2 3 3 0 . . 0 0 2 16 . . 9 0 . . 0 5 0 . . 7 0 4 1 0 . 0 0 0 2 0 . 0 3 9 8 0 . 0 0 0 4 E n s t a t 1 t e 0 . 154 0 , . 0 0 1 0 . 7 9 7 0 , . 0 0 7 0 . . 7 0 8 9 0 . 0 0 0 3 0 . . 5 6 0 0 . 0 0 6 • 11 v i n e 0 . 0 5 4 6 0 . 0 0 0 5 0 , . 4 9 8 0 O 0 6 0 . . 7 0 7 4 0 . 0 0 2 0 0 . . 3 1 7 0 . 0 0 5 T a b l e 5 - 6 R b - S r i s o t o p e d a t a of J o s e p h i n e P e r i d o t i t e S a m p l e s Rb ppm + / - S r ppm + / - 8 7 S r / 8 6 S r + / - 8 7 R b / 8 6 S r +/ J M 1 4 S y n . w r 0 . 0 9 1 8 0 . 0 0 0 8 0 . . 4 4 9 0 . 0 0 8 0 . . 7 0 7 3 0 . 0 0 0 5 0 . 5 9 2 0 . 0 1 2 D i o p s i d e 0 . 0 7 6 1 0 . 0 0 1 1 0 , . 5 8 2 0 . 0 2 8 0 . . 7 0 6 3 0 . 0 0 1 5 0 . 3 7 9 0 . 0 1 4 E n s t a t 1 t e 0 . 0 7 3 3 0 . 0 0 1 0 . 8 2 5 0 . 0 2 4 0 . 7 0 5 3 0 . 0 0 0 8 0 . 2 5 7 0 . 0 0 8 0 1 1 v l n e - 1 0 . 116 0 , . 0 0 1 0 , 2 8 3 0 . 0 0 6 0 . . 7 1 1 1 0 . 0 0 0 9 1 . 19 0 . 0 3 0 1 1 v 1 n e - 2 0 . 0 8 4 0 , . 0 0 1 0 , . 3 0 5 0 . 0 0 9 0 . 7 0 8 9 0 . 0 0 0 4 0 . 8 0 0 .01 J M 2 E n s t a t 1 t e 0 . 0 3 2 2 0 , . 0 0 0 3 0 . , 1 3 0 0 , . 0 0 8 0 . 7 0 8 7 0 . . 0 0 1 5 0 . 7 8 4 0 . . 0 3 2 J M 1 5 S y n . wr 0 . 0 5 2 5 0 . 0 0 0 6 0 . , 143 0 , . 0 1 0 0 . 7 0 9 1 0 , . 0 0 1 1 1 . . 0 7 0 , , 0 7 D i o p s i d e 0 . . 0 2 3 3 0 . 0 0 0 7 0 . 2 5 6 0 . . 0 1 2 0 . 7 0 5 4 0 . . 0 0 0 5 0 . . 2 3 0 0 . 0 3 0 E n s t a t 1 t e 0 . 0 2 9 3 0 , . 0 0 0 7 0 . , 126 0 , . 0 1 5 0 . 7 0 6 4 0 . . 0 0 2 0 0 . 6 7 6 0 . 0 8 2 0 1 1 v 1 n e . I H cs 0 . 0 9 1 2 0 , . 0 0 1 3 0 . , 153 0 , . 0 1 5 0 . 7 1 3 3 0 . . 0 0 0 8 1. 7 3 0 . 2 U r n 3 S y n . w r 0 . 1 1 6 0 , . 0 0 1 0 . 3 2 3 0 , . 0 0 8 0 . 7 0 9 5 0 . 0 0 1 1 1. 0 4 0 . 0 3 D i o p s i d e 0 , . 0 5 5 7 0 . . 0 0 1 5 0 . 4 5 6 0 . . 0 1 5 0 . 7 0 5 6 0 . 0 0 0 5 0 . 3 4 8 0 . 0 1 2 E n s t a t i t e 0 , 1 5 1 8 0 . 0 0 1 2 0 . 4 1 8 0 . 0 0 6 0 . 7 0 9 9 0 . 0 0 0 6 1. 0 5 0 . 0 2 01 1 v 1 n e 0 . . 102 0 . . 0 0 1 0 . 2 6 7 0 . 0 1 3 0 . 7 0 9 6 0 . 0 0 3 1 1. 10 0 . 0 5 T a b l e 5-7 Summary of mineral Isochrons Sample (87Sr/86Sr) +/- Date(Ma) + /- P e t r o l o g y T e x t u r e C h e m i s t r y Depth(km) uL1 0 . 7028 0 .0001 560 47 L h e r z o l 1 t e P r o t o g r a n u l a r JL14 0 .7024 0 .0001 450 55 L h e r z o l 1 t e P r o t o g r a n u 1 a r U n d e p l e t e d 46 JL15 0 .7025 0 .0001 576 41 L h e r z o l 1 t e P r o t o g r a n u l a r U n d e p l e t e d <vJL14 JL18 0 . 7026 0 .O001 34 1 137 L h e r z o l 1 t e P r o t o g r a n u 1 a r U n d e p l e t e d <JL 15 BM 1 1 0 . 7028 0 .0001 276 82 L h e r z o l 1 t e P r o t o g r a n u 1 a r D e p l e t e d <BM16 BM16 O 7019 0 .0016 1518 24 1 011v-Lherz Equ1granular U n d e p l e t e d 30 BM55 0 . 7032 0 .0002 396 27 011v-Lherz P r o t o g r a n u l a r U n d e p l e t e d >BM16 KR 1 0. . 7030 0 .0007 561 63 L h e r z o l 1 t e P r o t o - p o r p h D e p l e t e d 40 KR2 0 . 7028 0 .0001 792 58 L h e r z o l 1 t e P o r p h y r o c l a s t 1 c D e p l e t e d 49 KR35 0 7018 0 .0001 1537 74 L h e r z o l 1 t e E q u 1 granular U n d e p l e t e d 33 LL1 0. 7029 0 .0002 101 18 L h e r z o l 1 t e P r o t o g r a n u l a r D e p l e t e d 46 LL14 0. 7037 0 .0002 645 50 L h e r z o l 1 t e P r o t o g r a n u l a r D e p l e t e d 52 JM5 0. 7035 0. 0008 428 78 H a r z b u r g l t e P r o t o g r a n u l a r D e p l e t e d JM14 0. 7038 0. 0009 441 85 H a r z b u r g l t e P o r p h y r o c l a s t 1 c D e p l e t e d 35-63 JM15 O. 704 1 0. 0006 366 64 01Iv-Harzb. P r o t o g r a n u l a r D e p l e t e d 75 F i g . 5-1 JL1 m i n e r a l I s o c h r o n d e f i n e d by D i , En, 01. (87Sr/86Sr), = 0.7028+/-0.0001, s l o p e = 0.0080+/-0.0007 Rb-Sr d a t e = S59+/-47 Ma. F1g. 5-2 JL14 m i n e r a l Isochron d e f i n e d by WR, D i , En, 01. (87Sr/86Sr)„ = O.7024+/-O.0001, s l o p e = 0.00G4+/-O.0008 Rb-Sr d a t e = 450+/-55 Ma. 77 F i g . 5-3 JL15 m i n e r a l i s o c h r o n d e f i n e d by WR, D i , En, 01. (87Sr/86Sr )« = 0.7025+/-0.0001. s l o p e = 0.0082+/-0.0005 Rb-Sr d a t e = 576+/-41 Ma. 78 F i g . 5-4 JL18 m i n e r a l i s o c h r o n d e f i n e d by D i , En. 01. (87Sr/86Sr )„ = 0.7026+/-0.0001. s l o p e = 0.0049+/-0.0019 Rb-Sr d a t e = 341+/-137 Ma. 79 F1g. 5-5 BM11 m i n e r a l Isochron d e f i n e d by Dt. En, 01. ( 8 7 S r / 8 6 S r ) 0 = O.7028+/-O.OOO1. s l o p e = O.0039+/-O.0009 Rb-Sr date = 275+/-82 Ma. 80 81 F i g . 5-7 BM55 m i n e r a l i s o c h r o n d e f i n e d b y D i , En, 01. (87Sr/86Sr )„ = 0.7032 + /-0.0002, s l o p e = 0.0056+/-0.0003 Rb-Sr d a t e = 396+/-27 Ma. F i g . 5-8 KR1 m i n e r a l I s o c h r o n d e f i n e d by D i . En, 01. (87Sr/8GSr ). = O.7030+/-0.0007. s l o p e = 0.0080+/-O.0003 Rb-Sr d a t e = 561+/-63 Ma. F i g . 5-9 KR2 m i n e r a l I s o c h r o n d e f i n e d by WR. D i . En. (87Sr/86Sr)„= 0.7028+/-0.O O O1. s l o p e = 0.0113+/-0.0008 Rb-Sr d a t e = 792+/-58 Ma. 84 F i g . 5-10 KR35 m i n e r a l I s o c h r o n d e f i n e d by WR, 01, En. 01. (87Sr/86Sr )„ = 0.7018+/-0.0004. s l o p e = 0.0221+/-0.0007 Rb-Sr date = 1537+/-74 Ma. A - 0 t o p s tote • - E n s t a t i t e * - 01 1v1ne o - S y n . WR • - W h o l e r o c k 0 - A c i d l e a c h a t e V - H o s t b a s a l t 0 0.25 0.5 0.75 1 0 1 .25 "Rb/^'Sr l .5 2.25 2.5 F i g . 5-11 LL1 m i n e r a l i s o c h r o n d e f i n e d by WR, D1. En. 01. (87Sr/86Sr)„ = O.7029+/-0.0002, s l o p e = 0.0014+/-0.0002 Rb-Sr date = 101+/-18 Ma. T h i s sample i s p a r t i a l l y melted. The a s s o c i a t e d b a s a l t has g a i n e d 87Sr. * - O ( o p s ) d e • - E n s t a t i t e * - 0 1 i v i n e o - S y n . WR * - W h o l e r o c k 0 - A c i d l e a c h a t e V - H o s t b a s a l t o.o 0.25 0.5 0 75 I 25 " R b / ^ S r I 5 2.25 2 5 F i g . 5-12 LL14 m i n e r a l i s o c h r o n d e f i n e d by 01. En. 01. (87Sr/86Sr)»= 0.7037+/-O.OO01. s l o p e = O.0092+/-0.0006 Rb-Sr d a t e = 645+/-49 Ma. 87 F i g . 5-13 JM5 m i n e r a l i s o c h r o n d e f i n e d by O i , En. 01. (87Sr/86Sr )„= O.7035 + /-O.0008, s l o p e = O.0061+/-O.0011 Rb-Sr date = 428+/-78 Ma. 88 F i g . 5-14 JM14 m i n e r a l i s o c h r o n d e f i n e d by D i , En, 01. (87Sr/86Sr)» = 0.7038+/-0.0009. s l o p e = 0.0063+/-0.0011 Rb-Sr d a t e = 441+/-85 Ma. 89 F i g . 5-15 JM15 m i n e r a l Isochron d e f i n e d by D i . En. 01. ( 8 7 S r / 8 6 S r ) 0 = 0 . 7041+/-0.0006. s l o p e = 0.0052+/-0.0008 Rb-Sr date = 366+/-64 Ma. 90 VI. DISCUSSION General c o n s i d e r a t i o n s Mid ocean r i d g e b a s a l t (MORB) has low Rb and Sr contents and low Rb/Sr and 8 7 S r / 8 6 S r r a t i o s , i . e . Rb<10 ppm , Sr = 90-200 ppm, Rb/Sr =0.001-0.02 (or 8 7 R b / 8 6 S r = 0.0029-0.058), and 8 7 S r / 8 6 S r = 0.702-0.703 ( B a s a l t i c Volcanism Study P r o j e c t , 1981), and i s viewed as from a t y p i c a l " d e p l e t e d " mantle. If a mantle-derived sample i s not so d e p l e t e d i n incompatible elements, i t i s a s c r i b e d to c r u s t a l contamination or an "undepleted" or " e n r i c h e d " mantle. C o n t i n e n t a l f l o o d b a s a l t s have high Rb, Sr c o n t e n t s and 8 7 S r / 8 6 S r = 0.70369-0.70503 ( B a s a l t i c Volcanism Study P r o j e c t , 1981) and are most o f t e n i n t e r p r e t e d as showing contamination from the c r u s t ( C a r l s o n , 1984) or o r i g i n from an c i e n t l i t h o s p h e r e (Church, 1985). Ocean i s l a n d a l k a l i b a s a l t and some c o n t i n e n t a l w i t h i n - p l a t e b a s a l t s have high Rb and Sr contents and m i d d l i n g 8 7 S r / 8 6 S r r a t i o s , i . e . Rb>l0 ppm, Sr = 400-4000 ppm and 8 7 S r / 8 6 S r = 0.703-0.707 ( B a s a l t i c Volcanism Study P r o j e c t , 1981). Because there i s no c o n t i n e n t a l c r u s t present, i t i s i n f e r r e d that the b a s a l t i s from an undepleted or e n r i c h e d source r e g i o n i n the mantle, and f u r t h e r e n r i c h e d due to small degrees of p a r t i a l m e l t i n g . I s l a n d arc b a s a l t has Rb c o n c e n t r a t i o n of 2.4 - 32 ppm and Sr 135 - 540 ppm, 8 7 S r / 8 6 S r = 0.70328 ± 0.00015 91 ( B a s a l t i c Volcanism Study P r o j e c t , 1981). I s l a n d arc b a s a l t i s i n f e r r e d to o r i g i n a t e from m e l t i n g and dehydration of the subducted b a s a l t i c l a y e r of the oceanic c r u s t , with or without a sedimentary component (Green and Ringwood, 1968; B o e t t c h e r , 1977; Stern and W y l l i e , 1978); or from hydrous m e l t i n g of the p e r i d o t i t e wedge o v e r l y i n g the subducted s l a b (e.g. N i c h o l l s and Ringwood, 1973); or from m e l t i n g of p e r i d o t i t e mantle m o d i f i e d by i n t r o d u c t i o n of water or melt from the subducted oceanic c r u s t (e.g. N i c h o l l s and Ringwood, 1973). In any case i t s enrichment i n LIL and 8 7 S r i s now u n i v e r s a l l y a t t r i b u t e d to contamination with subducted m a t e r i a l . B a s a l t s (1) . Jacques Lake and Big Timothy Mountain B a s a l t s from Jacques Lake and Big Timonthy Mountain have very high Sr c o n t e n t s , 1276 - 1514 ppm, but r a t h e r normal range of Rb, 12.7 - 62.1 ppm. T h e i r 8 7 S r / B 6 S r r a t i o s are r e l a t i v e l y low, 0.70254-0.70301. (2) West K e t t l e R i v e r and L a s s i e Lake B a s a l t l a y e r s 1 to 3 i n West K e t t l e River l o c a l i t y have a uniform Rb c o n c e n t r a t i o n of 17 ppm. T h e i r Sr v a r i e s from 859 ppm of l a y e r 1 down to 642 ppm of l a y e r 3. A c c o r d i n g l y , 8 7 R b / 8 6 S r i n c r e a s e s s l i g h t l y upwards but 8 7 S r / 8 6 S r decreases from 0.7036 to 0.7029. These b a s a l t s are q u i t e s i m i l a r to c o n t i n e n t a l f l o o d or i s l a n d arc b a s a l t s . 92 B a s a l t l a y e r 4, the top l a y e r i n the West K e t t l e R i v er s e c t i o n , has a much higher Rb, higher Sr c o n c e n t r a t i o n , and higher 8 7 R b / 8 6 S r r a t i o . I t s 8 7 S r / 8 6 S r r a t i o i s the lowest of a l l , 0.70289, impl y i n g t h i s l a y e r r e s u l t e d from recent more i n t e n s i v e metasomatism or u n u s u a l l y small degree of m e l t i n g of a low 8 7 S r / 8 6 S r mantle source. B a s a l t adhering to nodule KR35 has s i m i l a r c h a r a c t e r , with even lower 8 7 S r / 8 6 S r r a t i o , 0.7026. B a s a l t adhering t o nodule LL14 has comparable Rb and Sr c o n c e n t r a t i o n s , 18.5 and 701 ppm r e s p e c t i v e l y , and a very low 8 7 S r / 8 6 S r r a t i o , 0.70254. The b a s a l t a d h e r i n g to nodule LL1 i s an e x c e p t i o n . I t has a higher 8 7 S r / 8 6 S r r a t i o , 0.7033, Rb=31.8 ppm and Sr=840 ppm. I t i s most l i k e ocean i s l a n d a l k a l i b a s a l t . The nodule-bearing b a s a l t s (except that adhering to nodule LL1) are very s i m i l a r to mid ocean r i d g e b a s a l t i n 8 7 S r / 8 6 S r r a t i o , but Rb and Sr c o n c e n t r a t i o n s are more l i k e ocean i s l a n d - w i t h i n p l a t e c o n t i n e n t a l b a s a l t s . P l a t e a u b a s a l t s i n g e n e r a l i n B r i t i s h Columbia have 8 7 S r / 8 6 S r above 0.703 (Armstrong, p e r s . comm., 1985) so these with nodules are q u i t e e x c e p t i o n a l . Nodules, nomative nepheline, and non r a d i o g e n i c Sr are a l l a s s o c i a t e d . The h i g h Rb and Sr contents can not be e x p l a i n e d by a " p r i m i t i v e mantle" or c r u s t a l contamination or the metasomatism i n which the metasomatic f l u i d i s d e r i v e d from the subducted sediments or a l t e r e d b a s a l t , because any of these mechanisms w i l l l e a d to d i s t i n c t l y higher 8 7 S r / 8 6 S r 93 r a t i o s than MORB. One hypothesis to e x p l a i n the nodule b e a r i n g b a s a l t s i s that they are generated as a r e s u l t of Juan de Fuca p l a t e subduction (see F i g u r e 2-1). Juan de Fuca p l a t e i s t y p i c a l l y o c e a n i c . The oceanic sediments on the downgoing p l a t e were f i r s t i n v o l v e d in the p a r t i a l m e l t i n g under the G a r i b a l d i arc and the b a s a l t s generated have higher 8 7 S r / 8 7 S r (0.7030 to 0.7036). The oceanic b a s a l t i c l a y e r (0.7025) was more i n v o l v e d in l a t e r stages of p a r t i a l m e l t i n g and the degree of m e l t i n g was small so that b a s a l t s with h i g h Sr and low 8 7 S r / B 6 S r r a t i o were generated. Recent plume/metasomatism of a d e p l e t e d mantle c h a r a c t e r i z e d by low 8 7 S r / 8 6 S r r a t i o i s an a l t e r n a t e e x p l a n a t i o n f o r a l k a l i b a s a l t s but would r e q u i r e i n t h i s case a plume/metasomatic f l u i d of u n u s u a l l y low 8 7 S r / 8 6 S r r a t i o . T h i s i s not p r e v i o u s l y r e c o g n i z e d . U l t r a m a f i c nodules A c i d - l e a c h m a t e r i a l from the nodules has r e l a t i v e high Rb (0.2-3 ppm), Sr (4-78 ppm) and high Rb/Sr r a t i o ; 8 7 S r / 8 6 S r r a t i o i s about 0.703 i n Jaques Lake and Big Timothy Mountain and 0.705-0.706 in K e t t l e R i v e r and L a s s i e Lake nodules. The a c i d - l e a c h m a t e r i a l i s a mixture of i n t e r s t i t i a l m a t e r i a l , adhering b a s a l t , weathering products and m a t e r i a l etched from the pyrex g l a s s beaker d u r i n g l e a c h i n g . The g l a s s has 0.36 ppm Rb, 3.6 ppm Sr, 8 7 S r / 8 7 S r = 0.7084 and 8 7 R b / 8 6 S r = 0.288. The weight l o s s of the g l a s s f o r one sample l e a c h i n g i s about 1 mg. Compared to the 94 amounts of Rb and Sr in the a c i d - l e a c h mixture of c h l o r i d e s , the Rb and Sr c o n t r i b u t e d by the g l a s s i s i n s i g n i f i c a n t . ( 1 ) . Jacques Lake An e a r l y to mid P a l e o z o i c i s o t o p i c e q u i l i b r a t i o n or miminum age are recorded by four m i n e r a l isochrons (576-341 Ma), with low Sr isotope i n i t i a l r a t i o s (0.7024 to 0.7028). The s y n t h e t i c whole rock has i d e n t i c a l Rb, Sr and 8 7 S r / 8 6 S r r a t i o with measured whole rock. Whole rock Sr iso t o p e composition and 8 7 R b / 8 6 S r r a t i o are l i k e MORB today. The a c i d - l e a c h i n g m a t e r i a l from JL14 and JL18 p l o t on the corr e s p o n d i n g mineral i s o c h r o n s , implying that the i n t e r s t i t i a l m a t e r i a l s might have been in e q u i l i b r i u m with the nodule m i n e r a l s d u r i n g the mantle events recorded by the is o c h r o n s . The a c i d - l e a c h m a t e r i a l from JL15 does not p l o t on the isoc h r o n due to high Rb/Sr r a t i o . The high Rb/Sr r a t i o can be i n t e r p r e t e d as l a t e r metasomatism i n the mantle or while in co n t a c t with molten b a s a l t , but not to weathering because the 8 7 S r / 8 6 S r r a t i o i s low. In c o n t r a s t to the depleted-source c h a r a c t e r i s t i c of the Sr, pyroxenes i n the nodules d i s p l y an undepleted major element chemistry and JL14 d i o p s i d e i n d i c a t e s Ti-metasomatism. Thus the mantle (40 km, 995°C) represented by these nodules i s a s u i t a b l e MORB source. The b a s a l t adhering to JL14 has s i m i l a r Rb, Sr and 8 7 S r / 8 6 S r r a t i o to the nodule d i o p s i d e and whole rock and l i e s on the iso c h r o n . But they are not cognate because i f so, the min e r a l isochron would be reset d u r i n g p a r t i a l m e l t i n g and gi v e the same age as the host b a s a l t . The nodule 95 i s i n t e r p r e t e d as an a c c i d e n t a l i n c l u s i o n ; the host b a s a l t r e s u l t e d from melting of a mantle s i m i l a r to the nodules. (2) . Big Timothy Mountain M i d - P r o t e r o z o i c and mid-Paleozoic dates (1518 Ma and 276 - 396 Ma), are given by three mineral i s o c h r o n s . None of the s y n t h e t i c whole rocks i s c o n s i s t e n t with the measured whole rocks. The measured whole rock data p l o t to the right-below the i s o c h r o n s . T h i s might be due to the e f f e c t of i n t e r s t i t i a l m a t e r i a l , because the a c i d - l e a c h m a t e r i a l has a high Rb/Sr r a t i o . The s y n t h e t i c whole rock 8 7 S r / 8 6 S r r a t i o s , 0.7033 to 0.7039, are i n the range of oceanic i s l a n d b a s a l t s from o n l y , s l i g h t l y d e p l e t e d mantle. Pyroxenes i n BM16 and BM55 d i s p l a y an undepleted, but i n BM11 a de p l e t e d , major element chemistry. Pyroxenes i n BM11 and BM55 show Ti-metasomatism but BM16 does not. We can i n f e r t h a t e i t h e r an e q u i g r a n u l a r m i d - P r o t e r o z o i c mantle l a y e r or l e n s (30km, 940°C) may have l a i n between p r o t o g r a n u l a r mid-Paleozoic mantle l a y e r s or the younger iso c h r o n s are reset by a mid-Paleozoic or l a t e r event. Host b a s a l t from B i g Timonthy Mountain p l o t s r i g h t - b e l o w the nodule m i n e r a l i s o c h r o n s . It c o u l d not be d e r i v e d from the same mantle as that represented by the nodules. The exp l a n a t i o n i s that the host b a s a l t came from a de p l e t e d mantle u n d e r l y i n g a l e s s d e p l e t e d mantle from which the nodules are e x t r a c t e d . (3) . K e t t l e River 96 An e q u i g r a n u l a r mantle was dated as Middle P r o t e r o z o i c by KR35. T h i s mantle has the same date, Sr i n i t i a l r a t i o , t e x t u r e , depth, and e q u i l i b r i u m temperature as BM16. Pyroxenes are undepleted in major element chemistry and show Ti-metasomatism. The whole rock 8 7 S r / 8 6 S r and 8 7 R b / 8 6 S r are on the boundary between d e p l e t e d and undepleted mantle types. The measured whole rock i s not i d e n t i c a l with the s y n t h e t i c whole rock, but i s on the i s o c h r o n . The b a s a l t adhering to KR35 i s not on the is o c h r o n , implying a non-cognate r e l a t i o n s h i p between the nodule and the host b a s a l t . A c i d - l e a c h i n g m a t e r i a l i s on the mineral i s o c h r o n , implying i t c o u l d have been i n e q u i l i b r i u m with the m i n e r a l s d u r i n g the event recorded by the i s o c h r o n . Under t h i s mantle l a y e r , the mantle represented by KR1 and KR2 i s p o r p h y r o c l a s t i c , undepleted in Sr isotopes but de p l e t e d i n major element chemistry of pyroxenes. KR1 g i v e s a p o o r l y d e f i n e d mineral isochron date of 561 Ma. Data from KR2 are too s c a t t e r e d to give an i s o c h r o n . Ignoring o l i v i n e , KR1 and KR2 give dates of 588 and 799 Ma, r e s p e c t i v e l y , Late Precambrian. Ignoring orthopyroxene, they give dates of 466 and 384 Ma, middle P a l e o z o i c , r e s p e c t i v e l y . O l i v i n e s are s e r i o u s l y d e v i a t e d from the iso c h r o n s , implying that mantle deformation or higher temperature or longer exposure t o e l e v a t e d temperatures has r e s u l t e d i n p a r t i a l r e s e t t i n g of these m i n e r a l i s o c h r o n s . Host b a s a l t s from K e t t l e R i v e r p l o t right-below the nodule mineral i s o c h r o n s , they are not cognate with the nodules. 97 (4). L a s s i e Lake A p r o t o g r a n u l a r mantle (52 km, 1008°C), was dated by LL14 to be 645 Ma, l a t e Precambrian. Pyroxenes are d e p l e t e d and l a c k Ti-metasomatism. The whole rock has been analysed in t r i p l i c a t e , i t p l o t s w e l l below the i s o c h r o n . The host b a s a l t c o u l d only a f f e c t the nodule 8 7 S r / 8 6 S r r a t i o , the reason why the nodule whole rock has high 8 7 R b / B 6 S r r a t i o i s not c l e a r . The s y n t h e t i c whole rock has undepleted Sr iso t o p e c h a r a c t e r . The host b a s a l t i s not i n e q u i l i b r i u m with the nodule, implying the b a s a l t came from a d e p l e t e d mantle u n d e r l y i n g the undepleted mantle from which the nodule came. In a shallower depth of the mantle (46 km, 995°C) the yougest event, 101 Ma, Mesozoic, was recorded by LL1. C o n s i d e r i n g the c o n s i d e r a b l e melt v i s i b l e i n the t h i n s e c t i o n and that the pyroxenes are not on the magmatic c r y s t a l l i z a t i o n t r e n d , t h i s date may be d r a s t i c a l l y r e s e t by the p a r t i a l m e l t i n g event. The host b a s a l t adhering to the nodule has e x c e p t i o n a l h i g h B 7 S r / 8 6 S r r a t i o compared to other nodule-bearing b a s a l t s . Although the b a s a l t p l o t s on the i s o c h r o n , the nodule i s not cognate with the b a s a l t because the observed m e l t i n g o c c u r r e d about 5 Ma ago. The Middle P r o t e r o z o i c to middle P a l e o z o i c C o r d i l l e r a n m i o g e o c l i n a l wedge occupies most of the core of the Rocky Mountain B e l t and u n d e r l i e s p a r t s of the Omineca C r y s t a l l i n e B e l t , but i t i s not observed i n the Intermontane B e l t (Monger and P r i c e , 1979). The Omineca western exposures of 98 basement and s t r a t i g r a p h i c e q u i v a l e n t s of t h i s wedge l o c a l l y c o n t a i n evidence of Middle and Late Precambrian (e.g. Duncan, 1978; Armstrong, 1985, p e r s . comm.) and mid-Paleozoic (e.g. O k u l i t c h et a l . , 1975) g r a n i t i c i n t r u s i o n , metamorphism and deformation. C o n s i d e r i n g that the isochron dates may be d i r e c t l y r e l a t e d to synchronous events in o v e r l y i n g c r u s t (e.g. B u r w e l l , 1975), the nodule mineral isochron dates may be r e l a t e d to m i d - P r o t e r o z o i c to Mid-Paleozoic r e g i o n a l g e o l o g i c a l h i s t o r y . A l t e r n a t i v e e x p l a n a t i o n s f o r the nodule mineral isochrons are that they r e c o r d the events that only i n v o l v e d mantle rocks or that they are h y b r i c - p a r t i a l l y and r e c e n t l y r e s e t from a s i n g l e E a r l y to Middle P r o t e r o z o i c time of c r y s t a l l i z a t i o n . In any case o l d mantle l i t h o s p h e r e must extend at l e a s t to the western edge of the Omineca B e l t . Josephine P e r i d o t i t e The Josephine P e r i d o t i t e has not been dated i s o t o p i c a l l y before t h i s work. The i s o t o p i c dates on gabbro to trondhjemite of the o p h i o l i t e s u i t e , which are t r a d i t i o n a l l y r e l a t e d to i t s age of formation (Harper, 1984), are a l l about 150 to 160 Ma (Dick, 1973; Coleman and o t h e r s , 1976; Hotz, 1971; Saleeby et a l . , 1982). Harper (1984) i n f e r r e d the Josephine P e r i d o t i t e was generated 157 Ma ago in the e a r l i e s t stages of back-arc spreading. However, Josephine P e r i d o t i t e i s dated to be middle P a l e o z o i c , 366 to 441 Ma, by three mineral i s o c h r o n s . The 99 d i s c r e p a n c y between the dates of Josephine P e r i d o t i t e and the a s s o c i a t e d rocks i n d i c a t e s that the o p h i o l i t e base does not n e c e s s a r i l y have the same age as o v e r l y i n g v o l c a n i c rocks and dykes. I t p r e s e r v e s . e v i d e n c e of an o l d e r mantle event. Other rocks i n the Klamath region a l s o give mid-Paleozoic metamorphic or i n t r u s i v e dates but i t i s not obvious how these can be r e l a t e d to the Josephine P e r i d o t i t e . Josephine P e r i d o t i t e i s extremely d e p l e t e d in Sr, more so than Rb, compared to the nodules. Both 8 7 R b / 8 6 S r and 8 7 S r / 8 6 S r are much higher than the nodules, today, and when the rocks were l a s t e q u i l i b r a t e d . The pyroxenes d i s p l a y extreme d e p l e t i o n and lac k Ti-metasomatism. Josephine P e r i d o t i t e may be i n t e r p r e t e d as a r e s i d u e of a l a r g e degree of melt e x t r a c t i o n , and the melt had i s l a n d arc b a s a l t Rb/Sr r a t i o and Sr i s o t o p i c composition. Evidence for m u l t i p l e episodes of p a r t i a l m e l t i n g was recognized by Dick (1975). Mantle growth curve The f i f t e e n mineral i s o c h r o n dates and Sr i n i t i a l r a t i o s have been p l o t on a Time - 8 7 S r / B 6 S r diagram (Figure 6-1). A l l nodules are d e p l e t e d compared with the bulk e a r t h . Most nodules are near the depleted-mantle e v o l u t i o n curve connecting BABI and MORB. Some d e v i a t e from t h i s curve. Only LL14 i s on "bulk e a r t h " e v o l u t i o n curve, i n d i c a t i n g an undepleted p r e h i s t o r y . The Josephine P e r i d o t i t e has 100 undepleted c h a r a c t e r , near to bulk e a r t h e v o l u t i o n curve. But i t s extreme Rb and Sr d e p l e t i o n e l i m i n a t e s the " p r i m i t i v e mantle" e x p l a n a t i o n . C o n s i d e r i n g i t s i s l a n d arc environment i n the J u r a s s i c and perhaps a l s o i n the P a l e o z o i c , the high 8 7 S r / 8 6 S r must be due to contamination from subducted m a t e r i a l during p a r t i a l m e l t i n g , and r e a c t i o n with r i s i n g v o l c a n i c arc magmas. Summary Jacques Lake nodules represent a d e p l e t e d MORB source-type mantle, other nodules represent somewhat l e s s d e p l e t e d mantle. E q u i g r a n u l a r nodules give a m i d - P r o t e r o z o i c mineral i s o c h r o n date . P r o t o g r a n u l a r nodules give l a t e Precambrian, e a r l y - m i d P a l e o z o i c and Mesozoic dates. P o r p h y r o c l a s t i c nodules do not d e f i n e mineral i s o c h r o n s , but must a l s o be P a l e o z o i c or o l d e r i n age. Host b a s a l t s are not cognate with the nodules and come from a low 8 7 S r / 8 6 S r mantle with small degree of mel t i n g or with recent metasomatism by f l u i d s of low 8 7 S r / 8 6 S r r a t i o . A P a l e o z o i c date f o r the Josephine P e r i d o t i t e i s i n c o n f l i c t with the view that i t was generated in the l a t e J u r a s s i c j u s t before Nevadan Orogeny. 101 1 - LL 1 * - J114 ^ - KR39 10 - JL 1 13 - JM14 2 - BM11 S - JL15 8 - BM5S 11 - KR 2 14 - JM 5 3 - JL18 6 - BM16 9 - KR 1 12 - JM19 IS - LL14 ° - ° 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 " 0 0 3 0 0 0 3 5 0 0 , 0 0 0 4 5 0 0 5 0 0 0 DATE (Ma) F i g . 6-1 E a r t h e v o l u t i o n c u r v e s 102 REFERENCES A l l e g r e , C . J . , S h i m i z u , N . a n d R o u s s e a u , D . ( 1 9 8 2 ) H i s t o r y o f t h e c o n t i n e n t a l l i t h o s p h e r e r e c o r d e d b y u l t r a m a f i c x e n o l i t h s . N a t u r e , 2 9 6 , 7 3 2 - 7 3 5 . A l l e g r e , S t a u d a c h e r , T . , S a r d a P . a n d K u r z , M . ( 1 9 8 3 ) C o n s t r a i n t s o n e v o l u t i o n o f E a r t h ' s m a n t l e f r o m r a r e g a s s y s t e m a t i c s . N a t u r e , 3 0 3 , 7 6 2 - 7 6 6 . A r m s t r o n g , R . L . ( 1 9 6 8 ) A m o d e l f o r t h e e v o l u t i o n o f s t r o n t i u m a n d l e a d i s o t o p e s i n a d y n a m i c E a r t h . R e v i e w s o f G e o p h y s i c s 6 , 1 7 5 - 1 9 9 . A r m s t r o n g , R . L . ( 1 9 8 1 ) R a d i o g e n i c i s o t o p e s : t h e c a s e f o r c r u s t a l r e c y c l i n g o n a n e a r - s t e a d y - s t a t e n o - c o n t i n e n t a l -g r o w t h e a r t h . P h i l . T r a n s . R . S o c . L o n d , A 3 0 1 , 4 4 3 - 4 7 2 . B a s a l t V o l c a n i s m S t u d y P r o j e c t ( 1 9 8 1 ) B a s a l t i c v o l c a n i s m o n t h e t e r r e s t r i a l p l a n e t s . P e r g a m o n P r e s s , I n c . , N e w Y o r k . 1 2 8 6 p p . B a s u , A . R . a n d M u r t h y , V . R . ( 1 9 7 6 ) S r - i s o t o p e s a n d t r a c e e l e m e n t s i n s p i n e l l h e r z o l i t e x e n o l i t h s i n b a s a l t s , S a n Q u i n t i n , B a j a C a l i f o r n i a . E O S , 5 7 , 3 5 5 . B a s u , A . R . a n d M u r t h y , V . R . ( 1 9 7 7 ) A n c i e n t l i t h o s p h e r i c l h e r z o l i t e x e n o l i t h i n a l k a l i b a s a l t f r o m B a j a C a l i f o r n i a . E a r t h a n d P l a n e t a r y S c i e n c e l e t t e r s , 3 5 , 2 3 9 - 2 4 6 . B a s u , A . R . ( 1 9 7 8 ) T r a c e e l e m e n t s a n d S r - i s o t o p e s i n s o m e m a n t l e - d e r i v e d h y d r o u s m i n e r a l s a n d t h e i r s i g n i f i c a n c e . G e o c h e m i c a e t C o s m o c h i m i c a A c t a , 4 2 , 6 5 9 - 6 6 8 . B e r r y , M . J . a n d M a i r , J . A . ( 1 9 7 7 ) T h e n a t u r e o f t h e E a r t h ' s c r u s t i n C a n a d a . A m e r i c a n G e o p h y s i c a l U n i o n G e o p h y s i c a l M o n o g r a p h 2 0 , 3 1 9 - 3 4 8 . B e t t o n , P . J . a n d C i v e t t a , L . ( 1 9 8 4 ) S t r o n t i u m a n d n e o d y m i u m i s o t o p i c e v i d e n c e f o r t h e h e t e r o g e n e o u s n a t u r e a n d d e v e l o p m e n t o f t h e m a n t l e b e n e a t h A f a r ( E t h i o p i a ) . E a r t h a n d P l a n e t a r y S c i e n c e L e t t e r s , 7 1 , 5 9 - 7 0 . 1 03 B e v i e r , M.L., A r m s t r o n g , R.L. and S o u t h e r , J.G. (1979) M i o c e n e p e r a l k a l i n e v o l c a n i s m i n w e s t - c e n t r a l B r i t i s h C o l u m b i a - - i t s t e m p o r a l and p l a t e t e c t o n i c s e t t i n g . G e o l o g y , 7, 389-392. B e v i e r , M.L. (1983) R e g i o n a l s t r a t i g r a p h y and age of C h i l c o t i n G r o u p b a s a l t s , s o u t h - c e n t r a l B r i t i s h C o l u m b i a . C a n a d i a n J o u r n a l of E a r t h S c i e n c e s , 20, 515-524. B i e l s k i - Z y s k i n d , M., W a s s e r b u r g , G.J. and N i x o n , D.H. (1984) Sm-Nd and Rb-Sr s y s t e m a t i c s i n v o l c a n i c s and u l t r a m a f i c x e n o l i t h s from M a l a i t a , Solomon I s l a n d , and n a t u r e of t h e Ontong J a v a P l a t e a u . J o u r n a l of G e o p h y s i c a l R e s e a r c h , 89, 2415-2424. B o e t t c h e r , A.L. (1977) The r o l e of a m p h i b o l e s and w ater i n c i r c u m - P a c i f i c v o l c a n i s m . I n : H i g h P r e s s u r e R e s e a c h (M.H. M a n a g h n a n i , ed.) A c a d e m i c P r e s s , N.Y, 107-126. Boyd, F.R. (1973) The p y r o x e n e g e o t h e r m . G e o c h i m i c a e t C o s m o c h i m i c a A c t a , 37, 2533-2546. B r e a r l e y , M., S c a r f e , C M . and F u j i i , T. (1984) The p e t r o l o g y of u l t r a m a f i c x e n o l i t h s from Summit L a k e , n e a r P r i n c e G e r o g e , B r i t i s h C o l u m b i a . C o n t r i b u t i o n s t o M i n e r a l o g y and P e t r o l o g y , 88, 53-63. B r e a r l e y , M., and S c a r f e , C M . (1984) A m p h i b o l e i n a s p i n e l l h e r z o l i t e x e n o l i t h : e v i d e n c e f o r v o l a t i l e s and p a r t i a l m e l t i n g i n t h e upper m a n t l e b e n e a t h s o u t h e r n B r i t i s h C o l u m b i a . C a n a d i a n J o u r n a l of E a r t h S c i e n c e s , 21, , 1067-1072. B r u e c k n e r , H.K. (1974) " M a n t l e " Rb/Sr and S r 8 7 / S r 8 6 r a t i o s f o r c l i n o p y r o x e n e s from N o r w e g i a n g a r n e t p e r i d o t i t e s and p y r o x e n i t e s . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , 24, 26-32. 1 04 B r u e c k n e r , H.K. (1975) C o n t a c t and f r a c t u r e u l t r a m a f i c assemblages from Norway: Rb-Sr e v i d e n c e f o r c r u s t a l c o n t a m i n a t i o n . C o n t r i b u t i o n s to M i n e r a l o g y and P e t r o l o g y , 49, 39-48. B u r w e l l , A.D.M. (1975) Rb-Sr i s o t o p e g e o c h e m i s t r y of l h e r z o l i t e s and t h e i r c o n s t i t u e n t m i n e r a l s from V i c t o r i a , A u s t r a l i a . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , 28, 69-78. C a m p b e l l , R.B. (1978) Quesnel Lake map-area. G e o l o g i c a l Survey of Canada. Open F i l e Map 574. C a r l s o n , R.W. (1980) C r u s t - m a n t l e d i f f e r e n t i a t i o n on the e a r t h and moon: e v i d e n c e from i s o t o p i c s t u d i e s f o r c o n t r a s t i n g mechanisms and d u r a t i o n , u n p u b l i s h e d P h . D . t h e s i s , U n i v e r s i t y o f ' C a l i f o r n i a at San D iego, 219pp. C a r l s o n , R.W. (1984) I s o t o p i c c o n s t r a i n t s on Columbia R i v e r f l o o d b a s a l t g e n e s i s and the n a t u r e of the s u b c o n t i n e n t a l m a n t l e . Geochimica et C o s c h i m i c a A c t a , 48, 2357-2372. C h a l l i s , G.A. (1969) D i s c u s s i o n of the paper, "The o r i g i n of u l t r a m a f i c and u l t r a b a s i c r o c k s " ; by P.J. W y l l i e , T e c t o n o p h y s i c s , 7, 495-505. Chase, C.G. (1981) Oceanic i s l a n d Pb: two-stage h i s t o r i e s and mantle e v o l u t i o n . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , 52, 277-284. Church, S.E. (1985) G e n e t i c i n t e r p r e t a t i o n of l e a d - i s o t o p i c d a t a from the Columbia R i v e r B a s a l t Group, Oregon, Washington, and Idaho. G e o l o g i c a l S o c i e t y of America B u l l e t i n , 96, 676-690. Cohen, R.S., O'Nions, R.K. and Dawson, J.B. (1984) I s o t o p e g e o c h e m i s t r y of x e n o l i t h s from East A f r i c a : i m p l i c a t i o n s f o r development of mantle r e s e r v i o r s and t h e i r i n t e r a c t i o n . E a r t h and P l a n e t a r y S c i e n c e L e t t e r s , 68, 209-220. 1 0 5 C o l e m a n , R . G . (197 1 ) P l a t e t e c t o n i c e m p l a c e m e n t o f u p p e r m a n t l e p e r i d o t i t e s a l o n g c o n t i n e n t a l e d g e s . J o u r n a l o f G e o p h y s i c a l R e s e a r c h , 7 6 , 1 2 1 2 - 1 2 2 1 . C o l e m a n , R . G . , G a r c i a , M . a n d A n g l i n , C . ( 1 9 7 6 ) T h e a m p h i b o l i t e o f B r i g g s C r e e k : a t e c t o n i c s l i c e o f m e t a m o r p h o s e d o c e a n i c c r u s t i n s o u t h w e s t e r n O r e g o n ( a b s t r a c t ) . G e o l o g i c a l S o c i e t y o f A m e r i c a A b s t r a c t s w i t h P r o g r a m s , 8 , 3 . D a v i e s , H . L . ( 1 9 6 8 ) P a p u a n u l t r a m a f i c b e l t . X X I I I I n t e r n a t i o n a l G e o l o g i c a l C o n g r e s s R e p o r t , 1 , 2 0 9 . D a v i e s , H . L . ( 1 9 7 1 ) P e r i d o t i t e - g a b b r o - b a s a l t c o m p l e x i n e a s t e r n P a p u a , a n o v e r t h r u s t p l a t e o f o c e a n i c m a n t l e a n d c r u s t . B u r e a u o f M i n e r a l R e s o u r c e s , A u s t r a l i a B u l l e t i n , 1 2 8 . D i c k , H . J . B . ( 1 9 7 3 ) K - A r d a t i n g o f i n t r u s i v e r o c k s i n t h e J o s e p h i n e P e r i d o t i t e a n d R o g u e F o r m a t i o n w e s t o f C a v e J u n c t i o n , S o u t h w e s t e r n O r e g o n ( a b s t r a c t ) . G e o l o g i c a l S o c i e t y o f A m e r i c a A b s t r a c t s w i t h P r o g r a m s , 5 , 3 3 - 3 4 . D i c k , H . J . B . ( 1 9 7 5 ) T h e o r i g i n a n d e m p l a c e m e n t o f t h e J o s e p h i n e p e r i d o t i t e o f s o u t h w e s t e r n O r e g o n , u n p u b l i s h e d P h . D . t h e s i s , Y a l e U n i v e r s i t y , New H a v e n , 3 0 1 p p . D i c k e y , J . S . ( 1 9 7 0 ) P a r t i a l f u s i o n p r o d u c t s i n a l p i n e - t y p e p e r i d o t i t e s , S e r a n i a d e l a R o n d a a n d o t h e r e x a m p l e s . M i n . S o c i e t y o f A m e r i c a S p e c i a l P a p e r , 3 , 3 3 - 4 9 . D u n c a n , I . J . ( 1 9 7 8 ) R b / S r w h o l e - r o c k e v i d e n c e f o r t h r e e P r e c a m b r i a n e v e n t s i n t h e S h u s w a p C o m p l e x , S o u t h e a s t B r i t i s h C o l u m b i a ( a b s t r a c t ) . P r o g r a m w i t h A b s t r a c t s , G e o l o g i c a l A s s o c i a t i o n o f C a n a d a , 3 , 3 9 2 - 3 9 3 . F a r l e y , A . L . ( 1 9 7 9 ) A t l a s o f B r i t i s h C o l u m b i a — p e o p l e , e n v i r o n m e n t , a n d r e s o u r c e u s e . U n i v e r s i t y o f B r i t i s h C o l u m b i a P r e s s , 1 3 6 p p . 1 06 F i e s i n g e r , D.W. and N i c h o l l s , J . (1977) Petrography and p e t r o l o g y of Quaternary v o l c a n i c rocks, Quesnel Lake region,• e a s t - c e n t r a l B r i t i s h Columbia. In: Baragar, W.R.Q., Coleman, L.C. and H u l l , J.M. (ed.) V o l c a n i c regimes in Canada. G e o l o g i c a l A s s o c i a t i o n of Canada S p e c i a l Paper, 16, 25-38. Forbes, R.B. and Kuno, H. (1965) The r e g i o n a l p e t r o l o g y of p e r i d o t i t e i n c l u s i o n s and b a s a l t i c host r o c k s . Upper mantle symposium, New D e l h i , 1964, Copenhagen, I n t e r n a t i o n a l Union of G e o l o g i c a l S c i e n c e s , 161-179. Forbes, R.B. and Kuno, H. (1967) P e r i d o t i t e i n c l u s i o n s and b a s a l t i c host rocks, In: P.J. Wylley (ed.) U l t r a m a f i c and r e l a t e d rocks, New York, Wiley, 328-337. F u j i i , T. and S c a r f e , C M . (1982) Pet r o l o g y of u l t r a m a f i c nodules from West K e t t l e R i v e r , near Kelowna, Southern B r i t i s h Columbia. C o n t r i b u t i o n s to Mineralogy and P e t r o l o g y , 80, 297-306. F u s t e r , J.M., Pasz, A. and Sagredo, J . (1970) S i g n i f i c a n c e of b a s i c and u l t r a m a f i c rock i n c l u s i o n s i n the b a s a l t s of Canary I s l a n d s . B u l l e t i n V o l c a n o l o g i q u e , 33, 665-693. Gast, P.W. (1972) The chemical composition of the e a r t h , the moon and c h o n d r i t i c m e t e o r i t e s , In: E.C. Robertson (ed.) The Nature of the S o l i d E a r t h , Mcgraw H i l l , New York, 19-40. Green, T.H. and Ringwood, A.E. (1968) Genesis of the c a l c - a l k a l i n e igneous rock s u i t e . C o n t r b u t i o n s to Mineralogy and P e t r o l o g y , 18, 105. Green, H.W. (1976) On the O r i g i n of spinel-pyroxene s y m p l e c t i t e s . EOS, T r a n s a c t i o n s of the American Geo p h y s i c a l Union, 57, 1026. G r i f f i n , W.L. and Murthy, V.R. (1968) Abundances of K, Rb, Sr and Ba in some u l t r a m a f i c rocks and m i n e r a l s . E a r t h and P l a n e t a r y Science L e t t e r s , 4, 497-501. 1 07 Hamilton, W.E. (1969) Mesozoic C a l i f o r n i a and underflow of P a c i f i c mantle. G e o l o g i c a l S o c i e t y of America B u l l e t i n , 80, 2409-2430. Harper, G.D. (1984) Middle to l a t e J u r a s s i c t e c t o n i c e v o l u t i o n of-the Klamath Mountains, C a l i f o r n i a - O r e g o n . T e c t o n i c s , 3, 759-772. H a r r i s , P.G., Reay, A. and White, I.G. (1967) Chemical composition of the upper mantle. J o u r n a l of Geophysical Research, 72, 6359-6369. Hess, H.H. (1938) A primary p e r i d o t i t e magma. American J o u r n a l of Science, 35, 321-344. Hess, H.H. (1955) S e r p e n t i n e s , orogeny and epirogeny. G e o l o g i c a l S o c i e t y of America S p e c i a l Paper 62, 391-408. Hess, H.H. (1964) The oceanic c r u s t , the upper mantle and the Mayaguey s e r p e n t i n i z e d p e r i d o t i t e . N a t i o n a l Academy of Sciences N a t i o n a l Research C o u n c i l P u b l i c a t i o n 118, 169-175. Hofmann, A.W. and White, W.M. (1982) Mantle plumes from a n c i e n t oceanic c r u s t . E a r t h and P l a n e t a r y Science L e t t e r s , 57, 421-436. Hotz, P.E. (1971) P l u t o n i c rocks of the Klamath Mountains, C a l i f o r n i a and Oregon. U.S. G e o l o g i c a l Survey, P r o f e s s i o n a l Paper 684-B, 20pp. Irwin, W.P. (1960) Geologic reconnaissance of the Northern Coast Ranges and Klamath Mountains, C a l i f o r n i a , with a summary of the m i n e r a l r e s o u r c e s . C a l i f o r n i a D i v i s i o n of Mines B u l l e t i n 179, 80pp. Irwin, W.P. (1972) Terranes of the Western P a l e o z o i c and T r i a s s i c b e l t in the southern Klamath Mountains, C a l i f o r n i a . U.S. G e o l o g i c a l Survey P r o f e s s i o n a l Paper 800C, 103-111. 1 08 Jackson, E.D. (1968) The c h a r a c t e r of the lower c r u s t and upper mantle beneath the Hawaiian I s l a n d . Procedings of the 3rd I n t e r n a t i o n a l G e o l o g i c a l Congress, 1, 135-150. Jackson, E.D. (1970) X e n o l i t h s in the Honolulu v o l c a n i c areas, Hawaii. J o u r n a l of P e t r o l o g y , 11, 405-430. Jacobson, S.B., Quick, J.E. and Wasserburg, G.J. (1984) A Nd and Sr i s o t o p i c study of the T r i n i t y p e r i d o t i t e : i m p l i c a t i o n s f o r mantle e v o l u t i o n . E a r t h and P l a n e t a r y Science L e t t e r s , 68, 361-378. Jagoutz, E., Palme, H., Baddenhausen, H., Blum, K., Cendates, M., Dreibus, G., S p e t t e l , B., Lorenz, V. and Wanke, H. (1979) The abundance of major, minor and t r a c e elements in the e a r t h ' s mantle as d e r i v e d from p r i m i t i v e u l t r a m a f i c nodules. Procedings of the 10th Lunar and P l a n e t a r y Science Conference. 2031-2050. Jaoutz, E., Lorenz, V. and Wanke, H. (1979) Major t r a c e elements of A l - a u g i t e s and C r - d i o p s i d e s from u l t r a m a f i c nodules in European a l k a l i b a s a l t s . In: Boyd, F.R., Mayer, H .O.A. (eds.) The mantle sample: i n c l u s i o n s in k i m b e r l i t e s and other v o l c a n i c s . American Geo p h y s i c a l Union, 382-390. Jagoutz, E., C a r l s o n , R.W. and Lumair, G.W. (1980) E q u i l i b r a t e d Nd - u n e q u i 1 i b r a t e d Sr i s o t o p e s i n mantle x e n o l i t h s . Nature, 286, 708-711. Kennedy, G.C. and I t o , K. (1972) Comments on: "A comparision of recent experimental data on the gabbro-garnet g r a n u l i t e - e c l o g i t e t r a n s i t i o n " . J o u r n a l of Geology, 80, 289-292. Kramers, J.D. (1977) Lead and s t r o n t i u m i s o t o p e s i n Cretaceous k i m b e r l i t e s and man t l e - d e r i v e d x e n o l i t h s from Southern A f r i c a . E a r t h and P l a n e t a r y Science L e t t e r s , 34, 419-431. Kuno, H. (1969) Mafic and u l t r a m a f i c nodules i n b a s a l t i c rocks of Hawaii. G e o l o g i c a l S o c i e t y of America Memoir, 115, 189-234. 1 09 Kushiro, I. (1969) The system f o r s t e r i t e - d i o p s i d e - s i 1 i c a with and without water at hi g h p r e s s u r e s . American J o u r n a l of Science, 267-A, 269-294. Larimer, J . (1971) Composition of the e a r t h : C h o n d r i t i c or a c h o n d r i t i c ? Geochimica et Cosmochimica Acta, 31, 1239-1270. L i t t l e j o h n , A.L. and Greenwood, H.J. (1974) L h e r z o l i t e nodules i n b a s a l t s from B r i t i s h Columbia, Canada. Canadian J o u r n a l of Earth S c i e n c e s , 11, 1288-1308. Lupton, J.E. (1983) T e r r e s t r i a l i n e r t gases: isotope t r a c e s t u d i e s and c l u e s to p r i m o r d i a l components in the mantle. Annual Review of E a r t h and P l a n e t a r y Science, 11, 371-414. Macdonald, G.J.F. (1959) C h o n d r i t e s and the chemical composition of the e a r t h . I n : Abelson, P. (ed.) Researches in Geochemistry. Wiley, New York,476-494. MacGregor, I.D. (1974) The system M g O - A l 2 0 3 - S i 0 2 : s o l u b i l i t y of A l 2 0 3 in e n s t a t i t e for s p i n e l and garnet p e r i d o t i t e compositions. American M i n e r a l o g i s t , 59, 110-119. Mark, R.K., Lee-Hu C. and W e t h e r i l l , G.W. (1973) Rb-Sr St u d i e s of lunar b r e c i a s and s o i l s . Procedings of the 4th Lunar Science Conference, 1 7 8 5 - 1 7 9 5 . Maxwell, R.J. (1976) A study of rubidium, strontium and st r o n t i u m i s o t o p e s in some mafic and sul p h i d e m i n e r a l s , unpublished M. Sc. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, 123pp. McTaggart, K.C. (1971) On the o r i g i n of u l t r a m a f i c rocks. G e o l o g i c a l S o c i e t y of America B u l l e t i n , 82, 23-42. Mengel, K., Kramm, U., Wedepohl, K.H. and Cohn, E. (1984) Sr iso t o p e in p e r i d o t i t e x e n o l i t h s and t h e i r b a s a l t i c host rocks from the northern Hessian Depression (NW Germany). C o n t r i b u t i o n s to Mineralogy and Pe t r o l o g y , 87, 369-375. 1 10 Menzies, M and Murthy, V.R. (1978) Strontium isotope geochemistry of A l p i n e t e c t o n i t e l h e r z o l i t e s : data compatible with a mantle o r i g i n . E a r t h and P l a n e t a r y Science L e t t e r s , 38, 346-354. Menzies, M and Murthy, V.R. (1980) Nd and Sr isotope geochemistry of hydrous mantle nodules and t h e i r host a l k a l i b a s a l t s : i m p l i c a t i o n s f o r l o c a l h e t e r o g e n e i t i e s in metasomatically veined mantle. E a r t h and P l a n e t a r y Science L e t t e r s , 46, 323-334. M e r c i e r , J-C and C a r t e r , N.L. (1975) Pyroxene geotherms. J o u r n a l of Geophysical Research, 80, 3349-3362. M e r c i e r , J-C and N i c o l a s , A. (1975) Textures and f a b r i c s of upper mantle p e r i d o t i t e s as i l l u s t r a t e d by x e n o l i t h s from b a s a l t s . J o u r n a l of P e t r o l o g y , 16, 454-487. M e r c i e r , J-C (1976) Single-pyroxene geothermometry and geobarometry. American M i n e r a l o g i s t , 61, 603-615. M e r c i e r , J-C (1980) Single-pyroxene thermobarometry. Tectonophysics, 70, 1-37. M i y a s h i r o , A. (1973) The Troodos complex was probably formed in an i s l a n d a r c . E a r t h and P l a n e t a r y Science L e t t e r s , 19, 218-224. Monger, J.W.H. and P r i c e , R.A. (1979) Geodynamic e v o l u t i o n of the Canadian C o r d i l l e r a - progress and problems. Canadian J o u r n a l of Earth S c i e n c e s , 16, 770-791. N i c h o l l s , I.A. and Ringwood, A.E. (1973) E f f e c t of water on o l i v i n e s t a b i l i t y i n t h o l e i i t e s and production of s i l i c a - s a t u r a t e d magmas in the i s l a n d arc environment. J o u r n a l of Geology, 81, p.285. N i c h o l l s , J . , Stout, M.Z. and F i e s i n g e r , D.W. (1982) P e t r o l o i c v a r i a t i o n s in Quaternary v o l c a n i c rocks, B r i t i s h Columbia. C o n t r i b u t i o n s to Mineralogy and P e t r o l o g y , 79, 201-218. 111 Nunes, P.D. (1980) The O n t a r i o G e o l o g i c a l Survey Geochronology Research - An Overview. In: Pye, E.G. (ed.) Summary of geochronology s t u d i e s 1977-1979, O n t a r i o M i n i s t r y of N a t u r a l Resources, M i s c e l l a n e o u s Paper 92,4-6. O'Hara, M.J. and Mercy, E.L.P. (1963) P e t r o l o g y and Pe t r o g e n e s i s of some g a r n e t i f e r o u s p e r i d o t i t e s . T r a n s a c t i o n s of the Royal S o c i e t y of Edinburgh, 65, 251-314. O'Hara, M.J. (1965) Primary magmas and the o r i g i n of b a s a l t s . S c o t t i s h J o u r n a l of Geology, 1, 19-40. O'Hara, M.J. (1967) M i n e r a l parageneses i n u l t r a m a f i c rocks. In: W y l l i e , P.J. (ed.) U l t r a m a f i c and r e l a t e d rocks, 393-402. O'Hara, M.J. (1968) The bearing of phase e q u i l i b r i a s t u d i e s in s y n t h e t i c and n a t u r a l systems on the o r i g i n and e v o l u t i o n of b a s i c and u l t r a b a s i c rocks. E a r t h - S c i e n c e Reviews , 4, 69-331. O k u l i t c h , A.V., Wanless, R.K. and Loveridge, W.D. (1975) Devonian pluto n i s m i n s o u t h - c e n t r a l B r i t i s h Columbia. Canadian J o u r n a l of E a r t h s c i e n c e s , 11, 976-997. O'Nions, R.K., Hamilton, P.J. and Evensen, N.M. (1977) V a r i a t i o n s i n 1• 3Nd/ 1 u"Nd and 8 7 S r / 8 6 S r r a t i o s i n oceanic b a s a l t s . E a r t h and P l a n e t a r y Science L e t t e r s , 34, 13-22. Osborn, E.F. (1969) The complementariness of orogenic a n d e s i t e and a l p i n e p e r i d o t i t e . Geochimica et Cosmochimica Acta, 33, 307-324. Papanastassou, D.A. and Wasserburg, G.J. (1973) Rb-Sr ages and i n i t i a l S r 8 7 / S r 8 6 r a t i o s i n A p o l l o 15 b a s a l t s . E a r t h and P l a n e t a r y Science L e t t e r s , 17, 324-337. Paul, D.K. (1971) Strontium isotope s t u d i e s on u l t r a m a f i c i n c l u s i o n s from D r e i s e r Weiher, E i f e l , Germany. C o n t r i b u t i o n s to Mineralogy and P e t r o l o g y , 34, 22-28. 1 1 2 Polve, M. and A l l e g r e , C.J. (1980) Orogenic l h e r z o l i t e complexes s t u d i e s by 8 7 R b - 8 7 S r : a c l u e to understand the mantle c o n v e c t i o n processes? E a r t h and P l a n e t a r y Science L e t t e r s , 51, 71-93. Richard, P. and A l l e g r e , C.J. (1980) Neodymium and strontium isotope study of o p h i o l i t e and orogenic l h e r z o l i t e p e t r o g e n e s i s . E a r t h and P l a n e t a r y Science L e t t e r , 47, 65-74. Riddihough, R.P. (1982a) Contemporary movements and t e c t o n i c s on Canada's west c o a s t : a d i s c u s s i o n . Tectonophysics, 86, 319-341. Riddihough, R.P. (1982b) One hundred m i l l i o n years of p l a t e t e c t o n i c s in western Canada. Geoscience Canada, 9, 28-34. Riddihough,. R.P. (1984) Recent movements of the Juan de Fuca p l a t e system. J o u r n a l of G e o p h y s i c a l Research, 89, 6980-6994. Ringwood, A.E. (1962) Present s t a t u s of the c h o n d r i t i c e a r t h models. In: C.B. Moore (ed.) Researches i n M e t e o r i t e s Wiley, New York, 198-216. Ringwood, A.E. (1975) Composition and p e t r o l o g y of the earth's mantle. New York, McGraw-Hill, 618pp. Rogers, G.S. (1983) S e i s m o t e c t o n i c s of B r i t i s h Columbia. Unpublished Ph.D. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, 1-20. Ross, C.S., F o s t e r , M.D. and Myers, A.T., (1954) O r i g i n of d u n i t e s and of o l i v i n e - r i c h i n c l u s i o n s i n b a s a l t i c rocks. American M i n e r a l o g i s t , 39, 693-736. Ross, J.V. (1983) The nature and rheology of the C o r d i l l e r a n upper mantle of B r i t i s h Columbia: i n f e r e n c e s from p e r i d o t i t e x e n o l i t h s . T e c t o p h y s i c s , 100, 321-357. 1 1 3 Saleeby, J.B., Harper, G.D., Snoke, A.W. and Sharp, W.D. (1982) Time r e l a t i o n s and s t r u c t u r a l - s t r a t i g r a p h i c p a t t e r n s i n o p h i o l i t e a c c r e t i o n , west c e n t r a l Klamath Mountains, C a l i f o r n i a . J o u r n a l of Geophysical Research, 87, 3831-3848. Schweickert, R.A. and Cowan D.S. (1974) P r e - T i t h o n i a n magmatic a r c s and subduction zones of the western S i e r r a Nevada, C a l i f o r n i a . G e o l o g i c a l S o c i e t y of America A b s t r a c t s with Programs, 6, 251-252. S o r e g a r o l i , A.E. (1968) Geology of the Boss Mountain Mine, B r i t i s h Columbia, unpublished Ph.D. t h e s i s , U n i v e r s i t y of B r i t i s h Columbia, Vancouver, 200pp. Souther, J.G. and Hickson, C.J. (1984) C r y s t a l f r a c t i o n a t i o n of the b a s a l t comendite s e r i e s of the mout E d z i z a v o l c a n i c complex, B r i t i s h Columbia: major and t r a c e elements. J o u r n a l of Volcanology and Geothermal Research, 21, 79-106. Stacey, R.A. (1974) P l a t e t e c t o n i c s , volcanism and the l i t h o s p h e r e in B r i t i s h Columbia. Nature, 250, 133-135. Steinmann, G. (1926) Die o p h i o l i t i s c h e n zonen i n dem Mediterranean Kettengebirgen. 14th I n t e r n a t i o n a l G e o l o g i c a l Congress, Madrid, Compte Rendu, 2, 638-667. St e r n , C R . and W y l l i e , P.J. (1978) Phase compositions through c r y s t a l l i z a t i o n i n t e r v a l s i n b a s a l t - a n d e s i t e -H 20 a t 30 kb with i m p l i c a t i o n s f o r subduction zone magmas. American M i n e r a l o g i s t , 63, 641-663. Stosch, H.G., C a r l s o n , R.W. and Lugmair, G.W. (1980) E p i s o d i c mantle d i f f e r e n t i a t i o n : Nd and Sr i s o t o p i c e v i d e n c e . E a r t h and P l a n e t a r y Science L e t t e r s , 47, 263-271 . Stueber, A.M. and Ikramuddin, M. (1974) Rubidium, s t r o n t i u m and the i s o t o p i c composition of strontium i n u l t r a m a f i c nodule minerals and host b a s a l t s . Geochimica et Cosmochimica Acta, 38, 207-216. 1 1 4 Thayer, T.P. (1964) P r i n c i p l e f e a t u r e s and o r i g i n of podiform chromite d e p o s i t s and some ob s e r v a t i o n s on the Guleman Soridag D i s t r i c t , Turkey. Economic Geology, 59, 1497-1524. Thayer, T.P. (1967) Chemical and s t r u c t u r a l r e l a t i o n s of u l t r a m a f i c and f e l d s p a t h i c rocks i n a l p i n e i n t r u s i v e complexes. In: P.J. W y l l i e (ed.) U l t r a m a f i c and r e l a t e d rocks, Wiley, New York, 222-239. Thayer, T.P. (1969) G r a v i t y d i f f e r e n t i a t i o n and magmatic reemplacement of podiform chromite d e p o s i t s . In: H.D.B. Wilson (ed.) Magmatic ore d e p o s i t s . Economic Geology Monograph, 4, 132-146. Trask, N.J. (1969) U l t r a m a f i c x e n o l i t h s i n b a s a l t , Nye County, Nevada. U.S. G e o l o g i c a l Survey P r o f e s s i o n a l Paper, 650-D, 43-48. Vollmer, R. (1983) E a r t h degassing, mantle metasomatism, and i s o t o p i c e v o l u t i o n of the mantle. Geology, 11, 452-454. Wagner, P.A.(1928) The evidence of the k i m b e r l i t e pipes on the c o n s t i t u t i o n of the outer part of the e a r t h . South A f r i c a n J o u r n a l of Science, 25, 127-148. Wells, P.R.A. (1977) Pyroxene thermometry in simple and complex systems. C o n t r i b u t i o n s to Mineralogy and Pe t r o l o g y , 62, 129-139. White, R.W. (1966) U l t r a m a f i c i n c l u s i o n s in b a s a l t i c rocks from Hawaii. C o n t r i b u t i o n s to Mineralogy and Petrology, 12, 245-314. White, W.M. and Hofmann, A.W. (1982) Sr and Nd isotope geochemistry of oceanic b a s a l t s and mantle e v o l u t i o n . Nature, 296, 821-825. White, W.M. and P a t c h e t t , J . (1984) Hf-Nd-Sr isotopes and incompatible element abundances in i s l a n d a r c s : i m p l i c a t i o n s f o r magma o r g i n s and crust-mantle e v o l u t i o n . E a r t h and P l a n e t a r y Science L e t t e r s , 67, 167-185. 1 15 White, W.M. (1985) Sources of oceanic b a s a l t s : r a d i o g e n i c i s o t o p e evidence. Geology, 13, 115-118. W i l s h i r e , H.G. and Binns, R.A. (1961) Basic and u l t r a b a s i c x e n o l i t h s from v o l c a n i c rocks of Newsouth Wales. J o u r n a l of P e t r o l o g y , 2, 185-208. W i l s h i r e , H.G. and S h e r v a i s , J.W. (1975) A l - a u g i t e and C r - d i o p s i d e u l t r a m a f i c x e n o l i t h s in b a s a l t i c rocks from western U n i t e d S t a t e s . In: Ahrens, L.H. et a l . (eds.), P h y s i c s and Chemistry of the Ea r t h , 9, Pergamon, New York, 257-272. W y l l i e , P.J. (1967) Mafi c and u l t r a m a f i c nodules i n t r o d u c t i o n . In: P.J. W y l l i e (ed.) U l t r a m a f i c and r e l a t e d rocks. Wiley, New York, 327-328. Wood, B.J. and Banno, S. (1973) Garnet - orthopyroxene and cli n o p y r o x e n e - orthopyroxene r e l a t i o n s h i p s i n simple and complex systems. C o n t r i b u t i o n s to Mineralogy and Pe t r o l o g y , 42, 109-124. Wood, B.J. (1975) The a p p l i c a t i o n of thermodynamics to some s u b s o l i d u s e q u i l i b r i a i n v o l v i n g s o l i d s o l u t i o n s . F o r t s c h r i t t e M i n e r a l o g i e , 52, 21-45. Z i n d l e r , A., Jagoutz, E. and G o l d s t e i n , S. (1982) Nd, Sr and Pb i s o t o p i c s y s t e m a t i c s i n a three-component mantle: a new p e r s p e c t i v e . Nature, 298, 519-523. APPENDIX 1 PROBE ANALYTICAL DATA OF NODULE MINERALS CPX MgO A 1 2 0 3 N a 2 0 S 1 0 2 C a O K 2 0 F e O C r 2 0 3 T 1 0 2 MnO T o t a l KR1 1 5 . 7 1 3 . 8 9 1.41 5 4 . 0 5 2 1 . 1 2 0 2 . 0 9 1 . 2 7 0 . 2 1 0 . 0 8 9 9 . 8 3 1 5 . 4 5 3 . 9 9 1 . 32 . 5 3 . 4 7 21 . 4 2 0 2 . 0 6 1 . 4 5 0 . 18 0 . 0 8 9 9 . 4 3 1 5 . 6 6 3 . 9 0 1 . 36 54 . 54 21 . 2 0 0 2 . 0 6 1 . 18 0 . 19 0 . 0 5 1 0 0 . 1 3 1 5 . 0 2 3 . 9 9 1 . 6 4 55 . 22 2 0 . 41 0 2 . 16 1 . 13 0 . 15 0 . 0 5 9 9 . 7 6 1 4 . 8 2 3 . 9 7 1 . 4 2 54 . 1 1 21 . 36 0 2 . 1 2 1 . 28 0 . 2 0 0 . 0 9 9 9 . 4 7 1 5 . 8 6 4 . 0 6 1 . 36 5 3 . 5 7 21 . 3 5 0 . 0 2 2. 13 1 . 4 2 0 . 17 0 . 11 1 0 0 . 0 5 15. . 15 4 . 8 0 1 . 17 54 .46 21 . 4 2 0 2 . 35 0 . 8 4 0 . .08 0 . .09 1 0 0 . 36 15. . 0 4 5 . 0 6 1 . 18 5 3 . .94 21 . 3 2 0 . .02 2 .33 0 . 9 7 0 . 0 8 0 . .06 100 . .01 14 . 9 3 4 8 6 1 . 2 6 5 3 .76 21 . 5 9 0 .01 2 . 3 5 0 98 0 . . 05 0 . .08 9 9 87 15. .21 4 9 8 1 . 24 53 . 12 21 . 3 9 0 2 .33 1 . 0 2 0 . .04 0 . . 11 9 9 .46 15 . 6 8 4 . 6 8 1 . 2 5 5 3 . 2 9 21 . 3 6 0 2 .31 0 , 8 6 0 0 9 0 , . 10 9 9 . 6 3 15. . 5 3 4 . 6 9 1 . 2 0 54 . . 04 21 . 44 0 . .01 2 . 2 7 0 . 8 8 0 . 10 0 . 0 4 100 . 2 0 15 . 3 7 5 . 0 0 1 .21 51 . 5 7 21 . 47 0 2 . 3 0 1. .02 0 . .08 0 . . 09 98 . 11 15 . 19 5 . 0 5 1 . 2 9 5 3 . . 62 21 . 2 6 0 2 . 28 1. 0 4 0 . . 1 1 0 . 11 9 9 . 93 14 . 9 3 6 . 6 0 1 . 5 8 52 . 8 5 2 0 . 10 0 . .01 2 .85 1 . 0 0 0 . 26 0 .06 100 . 23 14 . 8 7 6 . 4 0 1 . 6 3 53 . 13 2 0 . 0 4 0 2 88 0 . 9 6 0 . 31 0 . , 10 1 0 0 . 32 14 . 8 2 6 . 6 0 1 . 6 7 5 3 .01 2 0 . 14 0 . ,01 2 9 2 0 . 9 9 0 . 32 0 .08 100 . ,55 14. .68 6 . 7 6 1 . 58 52 . 4 3 2 0 . 15 0 . 01 2 83 0 , ,98 0 . 38 0 . ,09 9 9 . 8 9 14 . 6 0 6 . 7 5 1 . 5 8 52 . 9 2 2 0 . 0 2 0 2 . 97 0 ,98 0 . 44 0 . . 12 100 . 38 14 . 76 6 . 8 0 1 . 54 51 . 5 5 19 . 95 0 2 . . 87 0 , .94 0 . 34 0 . ,08 9 8 . 84 14 . 5 5 6 . 4 5 1 . 4 9 51 . 8 3 2 0 . 0 4 0 . .01 2 . 88 0 .95 0 . 27 0 . . 14 98 .64 14 . 8 3 6 . 4 5 1 . 6 5 51 . 76 2 0 . 12 0 . 01 2 . 77 1, , 03 0 . 28 0 . , 13 9 9 . 0 14 . 6 3 6 . 2 5 1 . 4 9 51 . 86 2 0 . 12 0 01 2 . 78 0 92 0 . 25 0 . . 09 98 . .45 OPX MgO A 1 2 0 3 N a 2 0 S 1 0 2 C a O F e O C r 2 0 3 T i 0 2 MnO T o t a l 34 . 0 8 2 . 75 0 . .08 5 6 , , 4 0 0 . 61 5 . . 9 0 0 , . 53 0 .02 0 . 14 100 . 5 1 32 8 2 2 . 8 2 0 . . 12 5 5 , 42 0 . . 59 5 .91 0 . 54 0 .04 0 . 16 98 .41 35 . 0 6 2 . 8 0 0 . 0 5 56 ,44 0 . 5 9 5 . 9 0 0 , 58 0 .03 0 . 18 101 .63 3 4 , . 8 0 2 . 8 3 0 . . 05 56 , 2 9 0 . 5 9 5 8 0 0 . 53 C ,03 0 . 16 101 . 09 34 8 9 2 84 0 . 0 7 5 6 , 41 0 . 6 0 5 . 87 0 , 55 0 0 6 0 . 15 101 44 3 5 , . 0 0 2 . 7 7 0 . .04 56 . 19 0 . 61 5 . . 8 1 0. 5 0 0 0 6 0 . 14 101 . . 12 34 .33 2 .76 0 . 16 56 . 75 0 . 59 5 . 82 0. 5 1 0. 06 0 . 15 101 . 12 3 3 , .81 2 . 9 0 0 . . 09 5 6 , . 72 0 . 61 5 . 87 0. 52 o. 03 0 . 15 100. 6 9 33 .98 2 .92 0 . 0 6 56 32 0 . 61 5 . 87 0. 54 0 05 0. 17 9 9 . 52 3 4 , 51 2 .88 0 . . 12 55 , , 76 0 . 58 5 . 74 0. 5 1 0. 0 6 0 : 14 100. 29 33 9 3 3 71 0 . 0 9 5 5 . 6 7 0 . 57 6 0 7 0 . 39 0 .03 0 . 13 100 . 5 9 34 , 0 3 3 82 0 .05 56 . 10 0 . .55 5 . 94 0 . 39 0 . 0 0 0 . 19 101 .07 34 . .01 3 . 64 0 0 7 5 5 . 14 0 . 58 5 . 8 9 0 . 34 0 . 0 0 0 . 14 99 81 33 . 7 0 3 . 66 O . 0 9 55 . 4 9 0 , .57 5 . 85 0 . 40 0 .03 0 . 15 99 .94 3 4 . 28 3 . 82 0 .04 55 . 78 0 . 53 5 . 91 0 . 44 0 .01 0 . 12 100 .93 3 3 . . 9 9 3 68 O . 10 56 . 15 0 . 58 5 93 0 . 47 0 .01 0 . 14 101 06 33 .51 3 . 79 0 .08 55 . . 75 0 . 61 5 88 0. 38 0 .01 0 . 20 100. 21 33 . 2 8 3 . 74 0 . 0 5 55 . . 84 0 . . 6 0 5 , 95 0 . 38 0 .01 0 . 15 100. 01 34 . 44 3 . 72 0 0 9 5 3 . 6 0 0 . 58 5 . 95 0 45 0 .02 0 . 13 9 8 . 98 34 . 33 3 .65 0 . 0 7 55 . 26 0 . .59 5 . 9 1 0 4 1 0 ,02 0 . 17 100. 42 LL1 T ; I X) 1 K> 1 KR 1 OL LL1 CD^4*4CI )^ l~<lCDCDC0GDa) 1 O O O I O O ~ - I - J O O - J C D 1 0 1 ( 0 ( 0 ( 0 0 ( 0 0 0 0 0 0 X i IQ i O ^ c j i o u i c o a ) 0 - > i c n u i - - i - j C D ~ j j ) * k c n u i c n u i O i c o o — ui — — — C O O I M C D ^ I -J . U l f O C D-1^1 — ~ J < T > O C 0 M 0 0 0 0 ( 0 0 0 ( 0 ( 0 1 0 0 1 - - . ^ - o - - - > o o m 1 m U U I U I M i l O l l i t ' l ' M I l — cn*»cjcnui — cncotocou i O u u — ( o u c n c n c D O O M i u i O d i - J O - J t u o i O u i ^ C D U i f e O f e ^ i c J c n i o i O i o a i c n — o - O o o c o i fflCtUUOMalU-JCI O l IO 1 o o o o o o o o o o o o - 0 0 0 0 - - 0 0 - - -O a> co CO (0 O — c o c a o o o O O O O O O O O O O O i O O O O O O O O O O i O O O O O O O O O O O 1 u i m u i u i u i u i u i u i u i i n u i u i U l { i { t G J c n U I U ! & U I » U I U I o - o o o o o o o - o i u > 0 ( o a o o u i o o ( o - ~ i O ( o i O O O O O O O O O O i O O O O O O O O O O a ) u i c n b ( j i < n ~ j c n c n c n 01 1 O 1 r o t n o f c O ( J u i ^ — lococn c o n o i o u i O u i a a ) « o i n o o o o o o o o o o o o ( 0 ( 0 ( 0 ( 0 ( 0 ( 0 ( 0 ( 0 ( 0 ( 0 ( 0 t ( 0 ( 0 ( 0 1 0 1 0 ( 0 1 0 ( 0 ( 0 ( 0 1 ( 0 ( 0 ( 0 ( 0 ( 0 1 0 ( 0 ( 0 ( 0 ( 0 •n i c j ( O c n o A & K > & c n ~ i c n o > COCDCOOOIOCOCDCO^IGOGO 1 ' - l U U U ' U O U - J H 1 M O — a i ^ t o w a i - . * . (D 1 O i cncFicncncncncncncncncf icn — c o t o M u o o b j u c o u i u i - i O O O O O O O O O O O i O O O O O O O O O O i O O O O O O O O O O Z l o o o o o o o o o o o o c n u r o c D t k C J O ^ c j i n o i O 1 o o o o o o o o o o o o O O O O O O O O O O O i O O O O O O O O O O i O O O O O O O O O O Z i o o o o o o o o o o o o o »M^jMi » ~ 4 o r > c n ( o ~»- j - i m O « a o u > i o i » - o > o i a i o o o o o o o o o o o o t 0 ( 0 l O ( 0 ( O < O ( O l O ( O ( 0 ( Q 1 CDCDCDCDCDCOCDCDOOCDtO 1 O ( o o o t o ( 0 ( o c o c o ( o i O ( O O - » G D ( 0 ( 0 ( 0 ( 0 ( O l o o o o g o o o g o Toti O l O l O l O ( 0 < 0 ( O I O U > ( 0 0 0 O ( 0 a > 0 3 ( 0 ( 0 ( 0 C D C D C D O O a > M O c D O - > u c n c j u } — > u i u i ^ i m r o O O > o c n c D - » i c j ~ j < n ( 0 a n - . c n m c o m i cnuiu i&~j<»ui-- .«CD U I - I C J — c j ^ i c n o i c o c d — a> U O ) I 0 O « < ] 1 - ' U O 1 > I O M SP MgO A1203 S102 FeO Cr203 MnO T1203 total KR1 17.45 38.44 17.56 39.65 17.69 38.58 17.76 40.00 17:60 40.01 17.64 40.25 17.54 39.84 0.04 13 . 08 0.06 12.72 O.OO 12.82 0.00 12.32 0.00 12.72 0.04 12.19 0.05 12.72 29.63 0.15 29.03 0.15 29.55 0.19 28.44 0.17 29.01 0.17 28.35 0.16 28.38 0.17 0.09 98.88 0.09 99.27 0.07 98.91 0.06 98.75 O.10 99.61 0.10 98.74 0.05 98.75 KR2 20.15 53.24 19.84 53.52 19.87 53.41 19.74 53.43 20.03 52.80 0.04 10.06 0.03 10.08 0.05 10. 13 0.06 10.05 0.00 10.06 15.05 0.13 15.27 0.12 15.32 0.09 15.40 0.13 15.37 0.07 0.00 98.67 0.07 98.93 0.02 98.88 0.00 98.82 0.00 98.34 LL1 19.93 55.77 20.09 55.87 20.05 55.77 19.91 55.49 20.05 55.87 0.06 9.45 0.07 9.73 0.09 9.56 0.07 9.70 O.OO 9.85 12.80 0.12 12.86 0.12 12.95 0.11 12.66 0.11 12.74 0.09 0.07 98.21 0.11 98.84 0.22 98.75 0.01 97.95 0.20 98.79 119 APPENDIX 2 F e 2 * and F e 3 * i n S p i n e l C a l c u l a t i o n (KR1 as an example) KR1 Sp.Mg A l S i Fe Cr Mn T i T o t a l oxide 17.61 39.54 0.027 12.65 28.94 0.166 0.08 99.01 wt.% # of 0.742 1.319 0.00080.300 0.647 0.004 0.0017 3.014 ions Formula (Mg,Fe,Mn)(Al,Cr,Fe) 20„ Mg + Mn + F e 2 * = 0.742 + 0.004 + 0.254 = 1 A l + Cr + F e 3 * = 1.319 + 0.647 +0.034 = 2 T o t a l Fe w i l l be p a r t i t i o n e d i n t o the formular as F e 2 * and F e 3 * a c c o r d i n g to the r a t i o F e 2 * / F e 3 * = 0.254/0.034. The r e f o r e F e 2 * = 0.300x0.254/(0.254+0.034) = 0.265 F e 3 * = 0.300x0.034/(0.254+0.034) = 0.035 A c c o r d i n g l y , m ineral composition has been r e c a l c u l a t e d t o : ion # oxide wt. oxide wt% Mg 0.742 29.9 17.73 A l 1.319 67.2 39.86 Si 0.0008 0.048 0.0003 F e 2 * 0.265 19.04 11.3 F e 3 * 0.035 2.79 1 .65 Cr 0.647 49.2 29. 18 Mn 0.004 0.28 0. 166 T i 0.0017 0.14 0.08 T o t a l 168.6 99.97 120 APPENDIX 3 PROBE ANALYTICAL DATA FOR JOSEPHINE PERIDOTITE PYROXENES (from D i c k , 1975) CPX FeO MgO S i02 CaO A1203 Cr203 T102 T o t a l J 2 8 f 2.88 16 . 98 5 1 . 24 22 . 73 3.84 1 . 46 0 0 4 99. 15 U87 1 2 . 43 18.55 52 .96 23.42 2.36 1 .00 0.03 100.75 J120 2.91 17 . 30 54 .04 22.73 5.11 1 . 10 0. 16 103.35 J120 2.30 18 . 27 53 . 45 23.77 2 . 10 0.69 0 .05 100.63 OPX FeO MgO 5 102 CaO A1203 CT203 T102 T o t a l J28 f 6 01 32 83 54 . 31 1 .73 3 56 0 91 0 .02 99 . 37 J46h 5. 83 33 . 37 56 . 30 1 . 83 3 34 0. 89 0. .04 101 . 60 J46h 5. 79 33 63 54 . 6 1 1 39 3 18 0 85 0 .04 99 . 49 J871 5 . 84 34 78 57 . 28 1 , , 1 1 2 .37 0, 55 0 .01 101 94 J 1 14 6*. 02 34 . 70 54 01 1 .04 2 .05 0 49 0 .01 98 32 J120 6 . 17 35 08 55 .01 0. 55 2 27 0. 43 0. .02 99 53 J46g 5 . 58 35 64 55 09 0 .79 0 .95 0 .55 0 .03 98 62 121 APPENDIX 4 CALCULATED TEMPERATURE , PRESSURE, DEPTH FROM J.V .ROSS DIOPSIDE ENSTATITE T°C P(kb) D(km) T°C P(kb) D(km) JL1 5 1063 18.61 60.6 1 051 17.98 58.7 1071 17.73 58.0 1059 17.71 57.9 1 072 19.50 63.3 1011 14.47 48. 1 1053 18.13 59.2 1013 14.57 48.4 1 034 17.49 57.3 .995 14.84 49.2 1 059 17.89 58.5 992 12.67 42.6 1 067 17.57 57.5 JL18 1 003 14.74 48.9 1 024 1 7.28 56.6 1017 14.73 48.9 1018 1 6.32 53.7 1 025 17.87 58.4 1 034 17.69 57.9 1 040 17.85 58.3 BM55 1038 16.05 52.9 1 067 17.76 58. 1 BM1 6 935 9.27 32.3 1 1 87 25.70 82. 1 943 10.41 35.8 1 064 1 6.62 54.6 1145 21 .70 70.0 1 083 17.74 58.0 117 1 23.46 7 5.4 BM1 1 1 093 1 3.37 44.8 LL1 4 1 024 17.49 , 57.3 1055 1 7.28 56.6 998 15.70 51 .8 1 067 1 7.72 57.9 1 074 20.51 66.4 1068 1 9.07 62.0 1 068 18.10 59. 1 KR35 922 8.76 30.8 1 058 1 6.44 54. 1 973 13.06 43.8 1 051 15.55 51.4 1039 14.10 47.0 1 1 27 19.91 64.6 122 APPENDIX 5 PROGRAM "RBSR" C PROGRAM "RBSR" C REWRITTEN FROM BASIC PROGRAMS "RBSPK3" AND "SRSPK3" C BY MIN SUN, 1984. C THIS PROGRAM IS FOR SPIKED RB,SR DATA REDUCTION. C TO RUN IT,2=(DATAFILE),GETTING SAMPLE NAME,WEIGHT,RB C SPIKE WEIGHT, C RB85/87,+/-,SR SPIKE WEIGHT,4/6,+/-,7/6,+/-. C BLANK VALUES HAVE BEEN PUT INTO THE PROGRAM. TO CHANGE C THEM, JUST C CORRECT XRB(5),YRB(5),XSR(6),YSR(6),XSR(7),YSR(7). C RB,SR SPIKE VALUES HAVE BEEN PUT IN THE PROGRAM. TO CHANGE C THEM, JUST C CORRECT XRB(I),YRB(I),1=2-4,XSR(J),YSR(J),J=2-5 C WEIGHING ERRORS ARE .0001. SR88/86=8.3752+/-.00001. C DIMENSION XRB(9),YRB(9),ERB(4),SRB(4,9), 1 XSR(12),YSR(12),T(11),F(11),SSR<6,12),ESR(6) WRITE(7,10) WRITE(8,11) WRITE(9,12) 10 FORMAT(//'RB SPIKE CONC(MICMOL/G) = .01069+/-.00007 */ 1'%87=99.2+/-.0l, %85=0.803+/-.004*/'RB BLANK=.0000036+/-*, 1 '.0000012 MOCROMOLES'//15X,'RBMICMOL/G',4X,'+/-', 1 6X,'RBPPM*,5X,'+/-',3X,'RB87MICMOL/G*,2X,'+/-',6X,'%BLANK', 1 3X,'RB87/SR86 +/-*) 11 FORMAT(//'SR SPIKE CONC(MICMOL/G) = .01150 + /-.00003 */ 1 'SR6/4=.00202+/-.00001,8/4=.01244+/-.00012,7/4=.00111+/-.00005' 1 'SR BLANK=.000047+/-.000032 MICROMOLES, 7/6=.7114+/-.0054'// 1 1X,'SRMICMOL/G',4X,'+/-',6X,'SRPPM',6X,'+/-',3X,'SR86MICMOL' 1 ,'/G',2X,'+/-',5X,'7/6 NORM',4X,'+/-',2X,'7/6 NORM-BLK', 1 3X,'+/-',5X,'%BLANK',3X,'86/88 MIX',2X,'CONV.CYS') 12 FORMAT(//l8X,'RBPPM',6X,'+/-',6X,'%BLANK',4X,'SRPPM',6X, 1 '+/-',5X,'SR87/86',6X,'+/-',5X,'%BLANK',3X,'RB87/SR86 +/-') IC=0 READ(2,20)CH1,CH2,CH3,XRB(7),XRB(6),XRB(8),YRB(8),XSR(11), 1 XSR(8),YSR(8),XSR(9),YSR(9) IF(IC.EQ.0)GOTO 17 20 FORMAT(///A4,1X,A4,1X,A4,F9.5,4F8.5,F10.5,F9.5,2F8.5) C 20 FORMAT(A4,1X,A4,1X,A4,F9.5,4F8.5,F10.5,F9.5,2F8.5) 15 READ(2,21)CH1,CH2,CH3,XRB(7),XRB(6),XRB(8),YRB(8),XSR(11), 1 XSR(8),YSR(8),XSR(9),YSR(9) 21 FORMAT(A4,1X,A4,1X,A4,F9.5,4F8.5,F10.5,F9.5,2F8.5) 17 WRITE(6,20)CH1,CH2,CH3,XRB(7),XRB(6),XRB(8),YRB(8),XSR(11), 1 XSR(8),YSR(8),XSR(9),YSR(9) DATA BLAN/'BLAN'/ IF(CH2.EQ.BLAN)GOTO 18 XRB(5)=0.0000036 YRB(5)=0.0000012 XSR(6)=0.000047 123 YSR ( 6 ) « 0 .000032 GOTO 19 18 XRB<5)-0.00000001 YRB(5 )»0 .000000005 XSR(6)»0.0000001 YSR(6)=0.00000005 19 XSR(7)=»0.7114 YSR(7)»0.0054 c * * * * * * * * * * * * g R DATA REDUCTION*********************** XSR(2)=0.0115 YSR(2)=.00003 XSR(3)=.00202 YSR(3)=.00001 XSR(4)=.01244 YSR(4)=.00012 XSR(5)=.00l11 YSR(5)=.00005 XSR(10)=8.3752 YSR(10)=.00001 YSR(11)=.00001 YSR(12)=.00001 XSR(12)«XRB(7) XSR(12)=XRB(7) XSR(1)=0.0 YSR(1 )=0.0 c CALCULATION DO 150 1=1,12 XSR(I)=XSR(I)+YSR(I) C SPIKE (4 + 6 + 8)/(4 + 6+7 + 8) A=(XSR(3)+XSR(4)+1.0)/(XSR(3)+XSR(4)+XSR(5)+1.0) W=A*XSR(2)*XSR(11) C SPIKE 4/(4 + 6 + 8) A4=1/(XSR(3)+XSR(4)+1) C SPIKE 6/(4 + 6 + 8) A6=XSR(3)/(XSR(3)+XSR(4)+l) C SPIKE 8/(4 + 6 + 8) A8=XSR(4)/(XSR(3)+XSR(4)+1) R1=XSR(8) F(1)=XSR(10) C ITERATION FOR FRACTIONATION DO 100 J=2,11 C..COMMON SR 4/6=.056584,8/6=8.3752 SO 6/(4+6+8)=0.106024 C 4/(4 + 6 + 8) = .005999,8/(4+ 6 + 8) = .887976 C SAMP+BLK (4 + 6+8) T(J)=W*(A4-R1*A6)/(R1*0.106024-0.00 5999) C SAMP + BLK 86 B6=T(J)*0.106024 C SAMP + BLK 88 B8=T(J)*0.887973 C SAMP + BLK 88/86 CAL C=B8/B6 C SAMP + B L K + SP 88/86 C A L R3=(B8+A8*W)/(B6+A6*W) 124 C SAMP+BLK+SP (88/86)CAL/(88/86)MEAS F(J)-R3/XSR(10) F2 - F ( J ) - 0 . 5 * ( F ( J ) - 1 . 0 ) R1-XSR(8)*(1/F(J)) R2«XSR(9)*F2 K-J-1 IF(ABS(F(J)-F(K)).LT.0.000001) GOTO 110 100 CONTINUE c CALCULATION C SSR(L,1)=F(X2,...X12) VALUES WITHOUT ERRORS C.....SSR(L,2)»F(X2+DX2,...X12) VALUES WITH ERRORS 110 SSR(1,I)-T(J) C 6/8 MIX IF(I.EQ.1) R4-1/R3 C SAMP+BLK+SP 87 G»R2*(B6+A6*W) C. .. . SAMP+BLK 87 B7»G-XSR(2)*XSR(11)*XSR(5)/(XSR(3)+XSR(4)+XSR(5)+1.0) C SR MICMOL/G SSR(2,I)=(T(J)+B7-XSR(6))/XSR(12) C SR PPM (COMMON SR ATMWT=87.62) SSR(3,I)=SSR(2,I)*87.62 C BLANK 87 C7=XSR(6)*XSR(7)/(XSR(7)+0.056584+1+8.3752) C BLANK 86 C6=C7/XSR(7) C SR86 MICMOL/G SSR(4,I)=(B6-C6)/XSR(12) C SR87/86 SSR(5,I)=B7/B6 C SR87/86 (-BLK) SSR(6,I)*(B7-C7)/(B6-C6) XSR(I)=XSR(I)-YSR(I) 150 CONTINUE c ERRORS C DELTF=SORT(SIGMA(DF/DXI*DXI)**2) C DF/DX2*DX2 = F(X2+DX2, . . .XI 2)-F(X2 XI 2) DO 170 J=2,6 ESR(J)=0 DO 160 1=2,12 ESR(J)=ESR(J) + (SSR(J, I )-SSR(J, 1 ) ) * * 2 160 CONTINUE ESR(J)=SQRT(ESR(J)) 170 CONTINUE Q — — RESULTS — BLKSR=XSR(6)/(SSR(1 ,1)+B7)*l00 WRITE(8,180)CHI,CH2,CH3,SSR(2,i),ESR(2),SSR(3,1),ESR(3), 1 SSR (.4 , 1 ) ,ESR( 4 ) ,SSR( 5, 1 ) ,ESR( 5) , SSR( 6, 1 ) , ESR ( 6 ) , BLKSR, 1 R4,K 180 FORMAT(A4,1X,A4, 1X,A4/2F10.6,2Fi0.5.2F10.7,6F10.5,6X,I 2) Q ************* R g DATA REDUCTION ************************* XRB(2)=.01069 125 YRB(2)-.00007 XRB(3)-99.2 YRB(3)«.0l XRB(4)«.803 YRB(4)=.004 YRB(6)=.0001 YRB(7)=.000l C . . . FRACTIONATION FACTOR XRB(9)-1.0 YRBC9)».003 c CALCULATION C S(J,1)=F(X2,...X9) VALUES WITHOUT ERRORS C S(J,2)=F(X2+DX2,...X9) VALUES WITH ERRORS XRB(l)-0 YRB(1)»0 DO 50 1 = 1,9 XRB(I)»XRB(I)+YRB(I) XRB(8)=XRB(8)*XRB(9) C MMOL RB(SAMP+BLK) SRB(1,I)=(XRB(3)*XRB(8)-XRB(4))/(72.1654-XRB(8)*27.8346 1 )*XRB(2)*XRB(6) IF(SRB(1 ,1).LT.0.0) WRITE(6,40) 40 FORMAT('WARNING!! UNDERSPIKED...RB<0') C MMOL/G RB (SAMP) SRB(2,I)=(SRB(1,I)-XRB(5))/XRB(7) C • PPMRB SRB(3,I)=SRB(2,I )*85.48 C RB87 MMOL/G SRB(4,I)-SRB(2,I)*0.278346 XRB(I)=XRB(I)-YRB(l ) 50 CONTINUE c ERRORS C DELTF=SQRT(SIGMA(DF/DXI*DXI )**2) C DF/DX2*DX2=F(X2+DX2, . . .X9)-F(X1 X9) DO 70 J=2,4 ERB(J)=0.0 DO 60 1=2,9 ERB(J)=ERB(J)+(SRB(J,I)-SRB(J, 1 ))**2 60 CONTINUE C ERRORS ERB(J)= SQRT(ERB(J)) 70 CONTINUE C RESULTS RBBLK=XRB(5)/SRB(1 ,1 )* 1 00 RBTSR=SRB(4,1)/SSR(4, 1 ) ERBSR=SQRT(ERB(4)**2/SRB(4,1)**2+ESR(4)**2/SSR(4,1)**2) 1*RBTSR WRITE(9,200)CH1,CH2,CH3,SRB(3,1),ERB(3),RBBLK,SSR(3,1), 1 ESR(3),SSR(6,1),ESR(6),BLKSR,RBTSR,ERBSR 200 FORMAT(A4,1X,A4,1X,A4,1 OF 10.5) WRITE(7,80)CHI,CH2,CH3,SRB(2,1).ERB(2).SRB(3.1).ERB(3). 126 1 SRB(4, 1 ) ,ERB(4) ,RBBLK,RBTSR,ERBSR 80 FORMAT(A4,1X,A4,1X,A4,2F10.7,2F10.6,2F10.7,3F10.6) IF(CH1.NE.END)GOTO 15 STOP END 127 APPENDIX 6-a PROGRAM "YORK" C c c c c c c c c c c c c c c. REVISED FOR RB-SR ISOCHRONS IN JAN., 1985 BY MIN SUN. B= APPROX. SLOPE, N = NO. OF POINTS X = 87RB/86SR, P = 1/SIGMA SQUARED OF X Y = 87SR/86SR, Q = 1/SIGMA SQUARED OF Y (THUS EACH POINT IS INDIVIDUALLY WEIGHTED ACCORDING TO ITS ACCURACY) FOR PB, WHEN R=1 ALL ERROR IS ASSUMED TO BE IN THE 204 MEASUREMENT WHEN R=0 , RANDOM ERRORS ARE ASSUMED : THIS IS EQUIVALENT TO THE OLD LEAST SQUARES CUBIC RESULTS. INTERMEDIATE VALUES OF R ASSIGN ERRORS PROPORTIONALLY BETWEEN THESELIMITS FOR RB-SR, R=0 DIMENSIONX(100),Y(100),U(100),V(100),P(100),Q(100),Z(100), 1R(100),F(100),G(100),ZIP(100),DX(100),DX2(100),ZAP(100), 2DY2(100),DAX(100),SDAX(100),DAY(100),SDAY(100),RESX(100), 3C(100),EX(100),EY(100),SANO(100),CH1(100),CH2(100), 4AL(100),DY(100),RESY(100),CH3(100) 100 WRITE(6,99) 99 FORMAT('INPUT # OF POINTS(I3), TITLE(A12)' ) READ(5,1)N,TITLE1,TITLE2,TITLE3 1 FORMAT(13,1X,A4,A4,A4) IF(N.EQ.O) GOTO 300 DO 110 1=1, N R(I)=0.0 READ(2,7) CH1(I),CH2(I),CH3(I),Y(I),EY(I),X(I),EX(I) 7 FORMAT(A4,1X,A4,1X,A4,50X,2F10.5,10X,2F10.5) P(I)=1/EX(I)**2 Q(I)=1/EY(I)**2 110 CONTINUE B=(Y(N)-Y(1))/(X(N)-X( 1 ) ) EPS=0.0001 ITMAX=10 ITER-0 SLOPE=B WRITE(7,50)TITLE1,TITLE2,TITLE3 50 FORMAT(//40X,'YORK REGRESION FOR ',3A4/) 10 B=SLOPE WRITE(7,55)B 55 FORMAT( 1 OX, 'TRIAL SLOPE=*,F10.5) ITER=ITER+1 SUMZ =0.0 XBAR =0.0 YBAR =0.0 BE = 0.0 D = 0.0 E = 0.0 128 ZU2 = 0 .0 SUMT - 0 .0 SUMS » 0 .0 SUMF = 0 . 0 SUMG = 0 . 0 ZIPS = 0 .0 DXS = 0 . 0 ZAPS = 0 . 0 DYS = 0 .0 DBS = 0 . 0 SZUM = 0 . 0 SDAXS = 0 . 0 SDAYS = 0 . 0 ALPHA = 0 . 0 DUJB = 0 .0 DVJB = 0 .0 BETA = 0 . 0 SUPER=0.0 RENO=0.0 DO 2 1 = 1 ,N AL(I) = SQRT(P(I)*Q(I)) Z<I) = P( I ) * Q ( I ) / ( B * B * Q ( I ) + P ( I ) - 2 . 0 * B * R ( I ) * A L ( I ) ) 2 SUMZ = SUMZ + 2 ( 1 ) DO 3 I = 1 , N XBAR = XBAR + Z(I)*X(I)/SUMZ 3 YBAR = YBAR + Z(I)*Y(I)/SUMZ DO 4 1=1,N U(I) = X(I) ~ XBAR V(I) = Y(I) - YBAR BE = BE + ( Z ( I ) * * 2 ) * ( ( U ( I ) * * 2 ) / Q ( l ) - ( V ( I ) * * 2 ) / P ( I ) ) D = D + ( Z ( I ) * * 2 ) * ( U ( I ) * V ( I ) / P ( I ) - R ( I ) * ( U ( I ) * * 2 ) / A L ( I ) ) ZU2 = ZU2 + Z ( I ) * U ( I ) * U ( I ) SUMT = SUMT + Z ( I ) * X ( I ) * X ( I ) F ( I ) = ( Z ( I ) * * 2 ) * V ( I ) * ( U ( I ) / Q ( I ) + B * V ( I ) / P ( I ) " R ( I ) * V ( I ) / A L ( I ) ) G ( I ) = ( Z ( I ) * * 2 ) * U ( I ) * ( U ( I ) / Q ( I ) + B * V ( I ) / P ( I ) - B * R ( I ) * U ( I ) 1/AL(I)) SUMF = SUMF + F(I ) SUMG = SUMG + G(I) 4 E = E + ( Z ( I ) * * 2 ) * ( U ( I ) * V ( I ) / Q ( I ) - R ( I ) * ( V ( I ) * * 2 ) / A L ( I ) ) SLOPE = (-BE + SQRT(BE**2 + 4.0*D*E))/(2.0*D) IF(ITER.GT.ITMAX) GOTO 101 IF(ABS(SLOPE-B).GT.ABS(EPS*SLOPE)) GOTO 10 SLOPE2 = SUMF/SUMG DO 5 I = 1,N 5 SUMS = SUMS + Z ( I ) * ( ( V ( I ) - SLOPE*U(I))**2) CINT = YBAR - SLOPE*XBAR VARB = 1.0/ZU2 SIGMAB = SQRT(VARB) VARA = VARB*SUMT/SUMZ SIGMAA = SQRT(VARA) DO 80 I = 1 ,N ZIP(I) = Z(I)**2*(SLOPE**2*V(I)/P(I)-2.0*(SLOPE**2)* 1R(I)*U(I)/AL(I) + 2.0*SLOPE*U(I)/Q(I) - V ( I ) / Q ( I ) ) 129 ZAP(I) = Z(I)**2*(SLOPE**2*U(I)/P(I)-2.0*SLOPE*V(I) 1/P(I)-U(I)/Q(I) + 2. 0 * R ( I ) * V ( I ) / A L ( I ) ) ZIPS = ZIPS + ZIP(I) ZAPS = ZAPS + ZAP(I) ALPHA=ALPHA+4.0*(Z(I)**3*(R(I)*AL(I)-SLOPE*Q(l))* 1(SLOPE*U(I)-V(I)) 1 * ( U ( I ) / Q ( I ) + S L O P E * V ( l ) / P ( l ) - R ( l ) * ( S L O P E * U ( I ) + V ( l ) ) / 2 A L ( I ) ) ) / A L ( I ) * * 2 DUJB=DUJB+2.0*Z(I)**2*U(I)*(SLOPE*Q(I)-R(I)*AL(I))/ 1(SUMZ*AL(I)**2) DVJB=DVJB+2.0*Z(I)**2*V(I)*(SLOPE*Q(I)-R(I)*AL(I ) ) / 1(SUMZ*AL(I)**2) 80 DBS = DBS +• Z(I )**2*(U(I )**2*( 1 . 0/Q (I )-2 . 0*SLOPE*R( I) / 1 A L ( I ) + V ( l ) * ( 2 . 0 * S L O P E * U ( I ) - V ( l ) ) / P ( l ) ) DO 81 I = 1 , N DX(I) = ZIP(I) - Z(I)*ZIPS/SUMZ DX2(I) = DX(I)**2/P(I) DXS = DXS + DX2(I) DY(I) = ZAP(I) - Z(I)*ZAPS/SUMZ DY2(I) = DY(I)**2/Q(I) BETA=BETA+Z(I)**2*(DUJB*(SLOPE**2*V(I)/P(I)+2.0*SLOPE* 1U(I)/Q(I)-V 1(I)/Q(I))+DVJB*(SLOPE**2*U(I)/P(l)-2.0*SLOPE*V(I)/P(I) 1- U ( I ) / Q ( I ) ) 2- 2.0*R(l)*(SLOPE**2*U(I)*DUJB-V(I)*DVJB)/AL(I)) 81 DYS = DYS+DY2(I) DCS = ALPHA + BETA DDS = DBS+DCS DO 82 I = 1,N 82 SZUM = SZUM + Z( I ) * * 2 * ( R ( I ) * A L ( I ) ~ S L O P E * Q ( I ) ) * ( V ( I )-1SLOPE*U(I))/(AL(I))**2 DO 83 I = 1,N DAX(I) = -SL0PE*Z(I)/SUMZ + (2.0*SZUM/SUMZ-XBAR)*(-1DX(I)/DDS) SDAX(I) = DAX(I)**2/P(I) DAY(I) = Z(I)/SUMZ + (2.0*SZUM /SUMZ-XBAR)*(-DY(I)/DDS) SDAY(I) = DAY(I)**2/Q(I) SDAXS = SDAXS + SDAX(I) SDAYS = SDAYS + SDAY(I) SUPER=SUPER+DX(I)*DY(I)*R(I)/AL ( I ) 83 RENO=RENO+DAX(I)*DAY(I)*R(I)/AL(I) ERRAA = SQRT(SDAXS + SDAYS) ERRAB=(SQRT(DXS +DYS))/DDS E5=ERRAB*SQRT(SUMS/(N-2)) E6=ERRAA*SQRT(SUMS/(N-2)) DO 84 1=1,N C(I)=R(I)*AL(I) RESX(I)=Z(I)*(CINT+S L O P E*X(I)-Y(I))*(C(I)-SLOPE*Q(I)) 1/(P(I)*Q(I)) 84 RESY(I)= Z(I)*(CINT + S L O P E * X ( I ) - Y ( I ) ) * ( P ( I ) - S L O P E * C ( I ) ) / 1(P(I ) * Q ( I ) ) TEMP=SUMS/(N-2) WRITE(7,52)TEMP 130 52 FORMAT(78X,6HMSWD= ,F15.8) WRITE(7,60)SLOPE2,SLOPE,SIGMAB,ERRAB,E5,CINT,SIGMAA, 1 ERRAA,E6 60 FORMAT(1 OX,8HSLOPE2= ,F15.8,5X,7HSLOPE= ,F15.8,10X, 1'EST SIGMA=',F15.8/ 1 6 8 X , ' E X A C T SIGMA=' ,F15.8,' OR' ,F15.8//1OX,'INTERCEPT* ' , 1, F15.8,35X 2, 'EST SIGMA=',F15.8/68X,'EXACT SIGMA=',F15.8,' 0R',F15.8) WRITE(7,56) 56 F0RMAT(/15X,'SECOND RESULT APPLIES IF MEAN SQUARE WEIGHTED 1 DEVIATES > 1') WRITE(7,70)XBAR,YBAR,ITER 70 FORMAT(//1OX,6HXBAR- ,F15.8,5X,6HYBAR- ,F15.8,1 OX,'ITER-',I 5) A2=100000*ALOG(1+SLOPE2)/l.42 IF(TEMP.GT.1.0) ERRAB-E5 A3-100000*ALOG(1+ERRAB)/1.42 WRITE(7,71)A2,A3 71 FORMAT(//'Rb-Sr date=',F10.5,'+/-',F10.5,'Ma') IF(TEMP.GT.1.0) ERRAA=E6 WRITE(7,72)CINT,ERRAA 72 FORMAT('INITIAL 87Sr/86Sr=',F10.5,'+/-',FI0.5) WRITE(7,65) WRITE(7,66)(CH1(I),CH2(l),CH3(I),X(I),EX(I),P(I),RESX(I),Y(I), 1EY(I),Q(I),RESY(I),1=1,N) 65 FORMAT(///17X,'Rb87/Sr86 +/- WEIGHTS RESIDUALS', 1 ' Sr87/Sr86 +/- WEIGHTS RESIDUALS') 66. FORMAT(A4,1X,A4,1X,A4,2F10.5,E15.5,3F10.5,E15.5,F10.5) GO TO 200 101 WRITE(7,95) 95 FORMAT(25X,22HDATA DID NOT CONVERGE.//) 200 GO TO 100 300 STOP END 131 APPENDIX 6-b PROGRAM "PLRBSR" C PROGRAM PLRBSR. WRITTEN BT MIN SUN, 1984. C THIS PROGRAM PLOTS RB-SR ISOCHRON BY INPUTTING C 2=(OUTPUT 9 OF PROG. "RBSR") DIMENSION X(3),Y(3) K=0 WRITE(6,10) 10 FORMAT('INPUT #(12) OF POINTS,MAX OF RB87/SR86, 1 MAX OF SR87/86') READ(5,20)NPOINT,RSMAX,SSMAX 20 FORMAT(12,1X,2F1 0.5) DO 100 1=1,NPOINT READ(2,30)A2,B,A1,C 30 FORMAT(64X,2F10.5,10X,2F10.5) X(1)=A1-C ' X(2)=A1 X(3)=A1+C Y(1)=A2 Y(2)=A2 Y(3)=A2 CALL POINTS(X,Y,K,RSMAX,SSMAX) K= 1 X(1)=A1 X(2)=A1 X(3)=A1 Y(1)=A2-B Y(2)=A2 Y(3)=A2+B CALL POINTS(X,Y,K,RSMAX,SSMAX) 100 CONTINUE 13 WRITE(6,11) 11 FORMAT ( ' INPUT INTERCEPT ( F 1 5 . 8 ) S, SLOPE ( F 1 5 . 8 ) , IF NO', 1'ISOCHRON IS PLOTED, PUT 0.0,0.0') READ(5,12)CINT,SLOPE 12 F0RMAT(2F15.8) IF(CINT.EQ.0.0)GOTO 120 X(1)-0.0 Y(1)=CINT X(2)=0.5*RSMAX Y(2)=0.5*RSMAX*SLOPE+CINT X(3)=RSMAX Y(3)=RSMAX*SLOPE+CINT CALL POINTS( X , Y , K ,RSMAX,SSMAX) GOTO 13 120 CALL PLOTND STOP END 132 Q *****************************pr JQT POINTS************ SUBROUTINE POINTS(X,Y,K,RSMAX,SSMAX) DIMENSION X(3),Y(3) IF(K.NE.0)GOTO 100 CALL ALSCAL(0.0,RSMAX,0.700,SSMAX) CALL ALSIZE(10.0,10.0) CALL ALAXIS('RB87/SR86',9,'SR87/SR86',9) 100 CALL ALGRAF(X,Y,-3,0) RETURN END APPENDIX 7 DUPLICATED RB-SR DATA S a m p l e Rb ppm +/• - S r ppm S r 8 7 / 8 6 +/- R b 8 7 / S r 8 6 +/-BM55 B A S T 4 3 . .5 2 .8 1276 33 0 . 7 0 2 5 8 0 0 0 0 0 5 0 . . 103 0 . . 0 0 7 0 . 7 0 3 1 0 0 . 0OO18 * a v e r a g e 0 . 7 0 2 7 2 0 . 0 0 0 0 6 BMS5 W R 0. . 3 3 2 0 . 0 1 3 12 . 1 0 . 0 5 0 7 0 2 7 0 0 . 0 0 0 1 1 0 . 0791 0 .0031 0. . 3 2 4 0 . 0 0 3 11 3 0 . 0 8 0 . . 7 0 2 6 3 0 0 0 0 0 9 0 . . 0 8 2 7 0 . 0 0 1 0 a v e r a g e 0 . . 3 2 6 0 . 0 1 0 11 . , 7 0 , . 3 3 0 . 7 0 2 6 7 0 0 O O 1 0 0 . 0 8 1 8 • 0 . . 0 0 1 5 BMS3 D I O P 33 3 0 . 1 1 0 . , 7 0 3 7 4 0 . 0 0 0 6 6 0 . 142 0 .001 3 3 , 1 0 . 10 0. 7 0 2 6 7 0 . 0 0 0 2 2 0 . 0 1 2 4 0 .0001 0. . 138 0 .001 3 4 . 9 0 , . 15 0. 7 0 3 0 7 0 . 0 0 0 3 8 0 . 0 1 1 4 0 . 0 0 0 1 0. 7 0 3 7 0 0 . 0 0 0 2 7 * a v e r a g e 0. . 1 4 0 0 .001 3 3 . ,5 0 . 0 7 0 . 7 0 3 3 3 0 . 0 0 0 2 2 0 . , 0 1 1 9 0 . 0 0 0 1 BMS5 01IV 0. .070 0 . 0 0 0 6 0 . 2 2 9 0 .007 0 . 7 0 9 8 3 0 . 0 0 0 9 3 0 . 8 8 3 0 . 0 2 8 0. . 0 6 9 0 . 0 0 0 7 0 . 2 6 0 0 . 0 0 8 0 . 7 0 9 3 1 0 . 0 0 0 9 1 0 . 7 6 9 0 . 0 2 5 0. .071 0 . 0 0 0 7 0 . ,291 0 O 0 8 0 . , 7 0 7 5 4 0 . 0 0 0 5 7 * a v e r a g e 0. .070 0 . 0 0 0 4 0 . 2 6 0 0 , 0 0 5 0 . 7 0 8 3 5 0 . 0 0 0 5 0 0 . 8 2 6 0 . 0 2 0 BM55 OPX 0 . .251 0 . 0 0 2 0 . 7 3 5 0 , . 0 0 7 0 . 7 0 7 3 8 0 . 0 0 0 5 7 0 , . 986 . 0 . 0 1 2 0 . 2 5 4 0 . 0 0 2 0 . 7 6 2 0 , 0 0 6 0 . 7 0 8 9 9 0 , . 0 0 0 2 8 0 . 9 6 4 0 .011 0 2 5 4 0 . 0 0 2 0 . 7 0 8 6 9 0 . 0 0 0 1 9 * a v e r a g e 0 . 2 5 2 0 , .001 0 . 7 4 9 0 . . 0 0 5 0 . 7 0 8 5 7 0 . 0 0 0 2 9 0 . , 9 7 5 0 . 0 0 8 2 BM11 W R 1. . 14 0 . 0 2 2 5 . 2 0 .6 0 . , 7 0 2 2 1 0 . 0 0 0 3 4 0 . 130 0 . 0 0 4 1 . . 12 0 . 0 2 2 5 . 7 0 . . 1 0 . 7 0 2 9 7 0 . 0 0 0 0 8 0 . 126 0 . 0 0 2 a v e r a g e 1 . 13 0 .01 2 5 . 6 0 . 2 0 . 7 0 2 8 2 0 , . 0 0 0 1 4 0 . .128 0 , . 0 0 2 J L 1 8 W R 0 . 2 5 2 0 , . 0 0 2 3 8 . 7 0 . . 1 0 . 7 0 1 9 5 0 . 0 0 0 1 3 0 . 0 1 8 8 0 . , 0 0 0 2 0 . 2 5 2 0 , . 0 0 2 37 . 0 0 . 7 0 . 7 0 3 8 1 0 , . 0 0 0 4 0 0 . 0 1 9 7 0 . 0 0 0 4 a v e r a g e 0 . 2 5 2 0 0 0 1 3 8 . 5 0 , 3 0 . 7 0 2 4 2 0 0OO2O 0 . 0 1 9 1 o. 0OO2 J L 1 4 W R o. 181 0 . 0 0 1 8 . 3 7 0 . 0 8 0 . 7 0 3 5 8 0 . . 0 0 0 8 8 0 . 0 6 2 4 0 . 0 0 0 8 0 . 176 0 .001 8 . 4 7 0 . . 03 0 . 7 0 2 9 0 0 , . 0 0 0 1 1 0 . 0 6 0 2 0 . 0 0 0 5 a v e r a g e 0 . 179 0 .001 a. 44 0 0 4 0 . 7 0 2 9 8 0 0 0 0 3 2 0 . 0 6 1 3 0 . 0 O 0 5 J L 1 4 O L I V 0 . 0 9 4 0 0 0 1 0 . 6 1 7 0 . 0 0 8 0 . 7 0 5 3 9 0 . 0 0 0 4 9 0 . 4 3 9 0 . 0 0 7 0 . 1 15 0 . 0 0 1 0 . 6 3 0 0 . 0 0 7 0 . 7 0 6 5 8 0 . 0 0 2 0 5 0 . 5 2 6 0 . 0 0 7 a v e r a g e 0 104 0 0 0 1 0 . 6 2 4 0 . . 0 0 5 0 . 7 0 5 6 3 0 , 0 0 0 4 5 0 . 4 8 3 0 . 0 0 5 J L 1 D I O P 7 7 . 1 0 . 7 0 . 7 0 3 0 0 0 . 0 0 0 1 2 0. 125 0 . . 0 0 2 76 . O 0 . 5 0 . 7 0 2 5 8 0 . 0 0 0 2 1 0 . 0 0 4 7 5 0 . ooooa a v e r a g e 76 . 5 0 . 4 0 . 7 0 2 8 6 0 , 0 0 0 2 2 J L 1 5 OPX 0 . 2 6 0 0 . . 0 0 2 2 . 76 0 . 01 0 . 7 0 3 9 2 0 . 0 0 2 3 1 0 . 2 7 3 0 . 0 0 3 o. 7 0 5 2 4 o. 0 0 0 3 8 a v e r a g e 0 . 7 0 5 0 5 0 . 0 0 0 8 6 J L 1 5 O L I V 0 . , 0 8 4 0 0 0 1 0 . 3 2 5 0 . 0 0 7 0 . 7 0 7 9 1 0 . 0 0 0 9 5 0 . 7 4 9 0 . 0 1 7 0 . 7 0 8 7 6 0 . 0 0 0 2 0 a v e r a g e 0 . 7 0 8 5 9 0 . 0 0 0 3 7 1 3 4 LL14 WR 0. 774 0 .008 9 .05 0 .07 0 .70388 0 .00013 0 .247 0. .003 0. 765 0 .007 8 .70 0 .03 0. .70347 0 .00010 0 .254 0, ,002 0. 767 0 .008 8 .55 0 .04 0 . 70362 0 .00010 0 .259 0 003 average 0. .769 0 .007 8 .77 0 .04 0 .70366 0 .00010 0 .254 0, .002 LL14 OIOP 0. 233 0 .002 16 .9 0 .06 0 .70422 0 .00029 0 .0398 0, 0O04 0. 70402 0 .00015 * average 0, .70409 0 .00017 KR33 OIOP 0. 278 0 .002 55 .6 0 .2 0. .70113 0 .00049 0, .0144 0, 0001 KR3S OIOP 0. . 70255 0 .00017 • average . 0. 70220 0 .00025 KR3S OLIV 0. 101 0 .001 0. .369 0. .008 0. ,71969 0 .00036 0, .795 0. .0178 0. 099 0 001 average 0. 100 0 OOI KR 1 WR 0. 385 O .005 4 26 0 .03 0. . 70358 0 .00030 0, .261 0 .004 4 . 39 0, .03 0. 70407 0 .00041 0. 70416 0 .00015 * average 4 . 33 0. .03 0. . 70399 0 .00020 KR2 OPX 0. 122 0. OOI 0, ,416 0. ,009 0. 71253 0 00175 0. .848 0. .0196 0. 71228 0 00026 * average 0. 71232 0 .00059 JM14 DIOP 0. 078 0 .001 0. 593 0. .033 0. 70631 0 00117 0. .381 0. .022 0. 074 0 002 0. .571 0. 040 0. 70577 0. 00347 0. .376 0, 027 average 0. 076 0 .001 0. . 582 0 028 0. . 70628 0 .00150 0 . 379 0 .014 JM14 OPX 0. 073 0. 001 0. 825 0 .024 0. 70609 0. 00241 0. .257 0, .008 0. 70513 0, .00050 average 0. 70529 0, .00080 0M2 OPX 0. 032 0. .0004 0. . 171 0. .008 0. 70845 0 .00199 0. 099 0. .020 0. 032 0. 0003 0. . 1 19 0 005 0. .70903 0 .00133 0. .784 0, 032 average 0. 032 0, 0003 0, . 130 0 .008 0. .70874 0 .00150 JM15 OLIV 0. 154 0. 02 0. 091 0. 0013 0 153 0. .01 0. 7 1330 0, 0008 1 1 .73 0. . 16 average 0. 153 0. 01 JM1S OPX 0. 031 0. 001 0. 130 0. 025 o. 683 0, 13 0. 028 0. 001 0. 121 0. 015 0. 70792 0 . 00352 o. 670 0. 087 0. 70564 0 00142 a v e r a g e 0. 029 0. 001 0. 126 0. 015 0. 70640 0 0 0 2 0 0 0. 676 0. 082 JM3 DIOP 0. 449 0. 019 0. 7 0 6 4 2 0 0 0 2 4 7 0. 056 0. 001 0. 463 0. 010 0. 7055 1 0 0 0 0 3 9 0. 348 0. 012 average 0. 456 0. 015 0. 70563 0 00050 * - - u n s p l k e d r u n 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
https://iiif.library.ubc.ca/presentation/dsp.831.1-0052429/manifest

Comment

Related Items