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Application of K-Ar and fission-track dating to the metallogeny of porphyry and related mineral deposits.. 1973

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APPLICATION OF K-Ar AND FISSION-TRACK DATING TO THE METALLOGENY OF PORPHYRY AND RELATED MINERAL DEPOSITS IN THE CANADIAN CORDILLERA by PETER ALLEN CHRISTOPHER B.Sc, State University of New York at Fredonia, 1966 M.A., Dartmouth College, Hanover, New Hampshire, 1968 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of Geological Sciences We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA . May, 1973 In presenting t h i s thesis i n p a r t i a l f ulfilment of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t freely available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of The University of B r i t i s h Columbia Vancouver 8, Canada i i . . ABSTRACT . This study evaluates the concept of metallogenic epochs as it applies to porphyry mineral deposits of the Canadian Cordillera, extends the study of the age of porphyry mineral deposits into northern British Columbia and the Yukon Territory, evaluates the usefulness of the fission-track dating method in determining the age and history of porphyry mineral deposits, and demonstrates the usefulness of an Ar^ total vs %K isochron plot. Samples were obtained from six areas in the Canadian Cordillera: the Syenite Range and Burwash Landing area in the Yukon Territory and Cassiar area, Adanac Property, Granisle Mine, and Copper Mountain area in British Columbia. Apatite was separated from the samples for use in fission-track analysis, and co-genetic biotite or hornblende was separated in order to obtain K-Ar checks on the fission-track ages. A comparison of fifteen apatite fission-track ages with K-Ar ages demonstrates that the apatite fission-track method can be used to age date porphyry mineral deposits, however the K-Ar method is generally more suitable in terms of cost and reliability. Discordant apatite fission-track and biotite K-Ar ages obtained from the Copper Mountain area and Granisle Mine suggest that apparent apatite fission-track ages from highly altered rocks or thermally complex areas should be checked by using another dating method (e.g. K-Ar). Radiometric dating of the Cassiar Molybdenum, Adanac, Mt. Reed and Mt. Haskin porphyry mineral deposits in northern British Columbia suggests that the Early Tertiary metallogenic.epoch- for porphyry deposits in central British i i i . Columbia and south-eastern Alaska, can be extended through northern British Columbia. Post-Eocene intermittent subduction of the Juan de Fuca plate below Vancouver Island and transverse motion along the Fairweather-Queen Charlotte- Shakwak-Denali Fault system with subduction into the Aleutian Trench are consistent with present plate-tectonic theory and the distribution of post- Eocene calc-alkalihe igneous rocks in the Canadian Cordillera. If porphyry mineral deposits form in calc-alkaline igneous rocks above active subduction zones, then the youngest porphyry deposits in the Canadian Cordillera should occur west of the Fairweather-Queen Charlotte-Shakwak-Denali fault system, on Vancouver Island and in the Cascade Mountains. The relatively young 26.2 m.y. biotite K-Ar age determined for the Burwash Creek porphyry west of the Shakwak Trench in the Yukon Territory is consistent with the evolution of porphyry mineral deposits above an active subduction zone. Comparison of K-Ar ages obtained for this study with published K-Ar ages suggests that metallogenic epochs for porphyry mineral deposits in the Canadian Cordillera occurred at approximately 195 m.y. and 150 + 10 m.y. for deposits of the plutonic and volcanic porphyry classes; and at approximately 100 m.y., 80 nwy., 65 m.y., 50 m.y., 35r40 m.y. and 26 m.y. for deposits of the phallic porphyry class. iv. ACKNOWLEDGMENTS Support for this study was provided through grants to Drs. A.J. Sinclair and W.H. White from the National Research Council of Canada and the Geological Survey of Canada. The writer was supported by teaching assistantships and a university fellowship from the University of British Columbia. The writer appreciates the assistance and co-operation of mining companies involved in exploration in northern British Columbia and the Yukon Territory. G. Brett (Brettland Mines), R..Oddy (Imperial Oil), W. Sirola (Kerr Addison Mines), G. Lamont (Delia Mines), and G. LeCheminant (Amax Exploration Inc.) were especially helpful. Several geologists employed by the British Columbia Department of Mines and by the Geological Survey of Canada provided helpful discussions of the geological settings of porphyry deposits in the Canadian Cordillera. Dr. V.A. Preto and N.C. Carter (B.C. Dept. Mines) and Drs. H. Gabrielse and J.W.H. Monger (Geological Survey of Canada) were especially helpful. The late Drs. J.A. Gower and W.H. White were instrumental in stimulating the writers interest in porphyry mineral deposits of the Canadian Cordillera. Their advice and encouragement contributed greatly to this study. Drs. A.J. Sinclair, H.R. Wynne-Edwards, A.E. Soregaroli and W.F. Slawson made suggestions for improvement of the original manuscript. Drs. A.J. Sinclair and H.R. Wynne-Edwards supervised the study. Numerous members of the Departments of Geological Sciences and Geophysics helped with useful discussion and advice. Miss Yvonne Colasanti, Mr. G. Cargill, Mr. B. Ryan, and Mr. J. Blenkinsop were especially helpful. Mr. J.E. Harakal supervised the potassium and argon analyses. CONTENTS Page INTRODUCTION 1.1 SCOPE 1 1.2 PORPHYRY MINERAL PROPERTIES STUDIED 3 POTASSIUM-ARGON DATING 2.1 INTRODUCTION 2.2, K-AR METHOD 2.3 GRAPHICAL INTERPRETATION OF K-AR DATA 2.4 APPLICATION OF ISOCHRON METHOD FISSION TRACK DATING 3.1 INTRODUCTION 3.2 FISSION TRACK METHOD 3.2.1 Procedure 3.2.2 Flux Determination 3.3. EVALUATION OF FISSION TRACK METHOD 3.4 PRESENTATION OF DATA 3.5 DISCUSSION OF FISSION TRACK RESULTS 7 8 11 14 2.4.1 Ar 4 0 total vs %K Isochrons 1 7 Case I. Cape Breton Whole-Rock Samples Case II. Tulameen Complex Hornblende Samples 2.5 SUMMARY 21 2.6 EVALUATION OF ISOCHRON METHOD 22 23 24 25 27 28 32 34 3.6 COMPARISON OF K-AR AND FISSION TRACK DATING TECHNIQUES37 40 3.7 SUMMARY AND CONCLUSIONS AREAS STUDIED 4.1 INTRODUCTION 4.2 SYENITE RANGE, YUKON TERRITORY 4.2.1 Introduction 4.2.2 General Geology and Geochronology 4.2.3 Radiometric dating 4.2.4 Discussion 4.3 CORK (BURWASH CREEK) Cu-Mo PROSPECT 4.3.1 Introduction 4.3.2 Potassium-Argon Results 4.3.3 Fission Track Results 4.3.4 Discussion 4.4 NORTHERN BRITISH COLUMBIA 4.4.1 Introduction 4.4.2 Cassiar Area Cassiar Molybdenum Property Mt. Haskin Mo and Mt. Reed Mo-W Properties Discussion 4.4.3 Atlin Area Adanac Mo Property 4.5 GRANISLE MINE, BABINE LAKE AREA, BRITISH COLUMBIA 4.5.1 Introduction 4.5.2 Potassium-Argon Dating 4.5.3 Fission Track Dating 4.5.4 Discussion v i i i . Page 4.6 COPPER MOUNTAIN AREA, BRITISH COLUMBIA 63 4.6.1 Introduction 63 4.6.2 General Geology 63 4.6.3 Fission Track Dating 66 4.6.4 Summary 68 5. REVIEW OF METALLOGENY AND METALLOGENIC EPOCHS FOR PORPHYRY MINERAL DEPOSITS OF THE CANADIAN CORDILLERA 69 5.1 INTRODUCTION 69 5.2 METALLOGENY AND METALLOGENIC EPOCHS 69 5.3 TECTONIC SETTING 71 5.4 AGE DATING AND METALLOGENIC EPOCHS 77 5.5 PLATE TECTONICS AND METALLOGENY OF PORPHYRY MINERAL DEPOSITS 85 6. CONCLUSIONS 88 REFERENCES 93 APPENDIX A. DESCRIPTION OF SAMPLES USED FOR K-Ar AND FISSION TRACK AGE DETERMINATIONS 104 APPENDIX B. POTASSIUM-ARGON DATING B.1 PROCEDURE 110 B.2 PRECISION AND ACCURACY 110 B.3 ATMOSPHERIC CONTAMINATION 112 B. 4 APPLICATION OF A r 4 0 (rad.) vs %K ISOCHRONS TO PUBLISHED DATA 112 B.4.1 Guichon Batholith 112 B.4.2 Topley Intrusions 116 B.4.3 Summary 116 APPENDIX C. FISSION TRACK DATING 118 C. l Introduction 118 Page C.2 Procedure 1 1 8 APPENDIX D. TABLE OF PUBLISHED K-Ar AGES REVIEWED FOR THIS REPORT 132 X . LIST OF TABLES Page Table 1-1 Classification of deposits studied. 6 2-1 Potassium-argon analytical data (ages obtained for 9 this study). 2-2 Isotopic abundance of potassium and argon. 10 2-3 Analytical data and ages of Cape Breton whole rock 18 samples. 2- 4 Analytical data and ages of hornblende from Tulameen Complex. 3- 1 Fission track analytical data and ages. 33 4- 1 Fission-track and K-Ar ages obtained for granitic 45 rocks in the Syenite Range, Yukon Territory. 4-2 Fission-track and K-Ar ages obtained for granitic 49 rocks in the Burwash Landing area, Yukon Territory. 4-3 Fission-track and K-Ar ages obtained for granitic 54 rocks in northern British Columbia. 4-4 Fission-track and K-Ar ages for granitic rocks in 68 the Copper Mountain area, British Columbia. B-l Potassium-argon data for Guichon Creek Batholith. 113 B-2 Potassium-argon data for the Topley Intrusions. 114 C-l Frantz separation settings for desired mineral 120 separation. C-2 Etching techniques used for materials studied. 125 C-3 Etching conditions for fission-track counting. 124 D-l Published K-Ar ages referred to in this report. 132 X I . LIST OF FIGURES Page Figure 1-1 Location map of areas studied. 5 2-1 Isochron plots for quartz latite porphyry near 15 Burwash Creek, Yukon Territory. 2-2 Isochron plots for Mt. Reed and Mt. Haskin 16 porphyries. 2-3 Total and corrected Ar 4 0  vs %K isochrons for 19 whole-rock K-Ar data. 2- 4 Comparison of Ar 4 ^ total isochron with Ar^O 20 corrected isochron diagram for K-Ar hornblende data from the Tulameen Complex, British Columbia. 3- 1 Graphical comparison of apatite fission-track and 35 biotite potassium-argon apparent ages. 3- 2 Track-loss curves for epidote, sphene, and apatite. 38 4- 1 General geology and geochronology of the Syenite 43 Range, Yukon Territory. 4-2 General geology and geochronology in the Burwash 47 Landing area, Yukon Territory. 4-3 General geology and geochronology of the Cork prospect.47 4-4 General geology and geochronology in the Cassiar area, 52 B.C., Mt. Haskin Mo property and Mt. Reed Mo-W property. 4-5 General geology and geochronology in the Atlin area 53 and of the Adera Claims - Adanac Mo property. 4-6 Geochronology and general geology of the Granisle Mine 61 pit. 4- 7 General geology of the Copper Mountain area, British 64 Columbia. 5- la Tectonic setting of porphyry mineral deposits in the 72 Canadian Cordillera (49-52°N). 5-lb Tectonic setting of porphyry mineral deposits in the 73 Canadian Cordillera (52-56°N). 5-lc Tectonic setting of porphyry mineral deposits in the 74 Canadian Cordillera (56-64°N). x i i . Figure 5-2 5-3 5-4 5-5 5-6 5-7 B-l B-2a B-2b C-l Plate 1 2 3 4 5 6 LIST OF FIGURES (Cont.) Page Tectonic map of the Canadian Cordillera. 76 K-Ar age determinations for igneous rocks in the 79 Canadian Cordillera. K-Ar age determinations for igneous rocks in segments 80 of the Canadian Cordillera between 49-52°N, 52-56°N and 56-64°N. K-Ar age of porphyry mineral deposits in the Canadian82 Cordillera. Triassic lavas and the Triassic and Jurassic porphyry83 deposits. Early Tertiary volcanic rocks and porphyry deposits. 84 Estimated precision for determining the ^kr/^K 111 ratio as a function of the atmospheric correction. Isochron plots for data from the Guichon Batholith, 115 Topley Intrusions, and sample T68-33 from the Topley Intrusions. Isochron plot for the Witches Brook Phase of the 115 Guichon Batholith. Flowsheet for mineral separating. 119 LIST OF PLATES Microphotograph showing spontaneous fission-tracks in standard apatite sample Me/G-1. 128 Microphotograph showing induced tracks in standard apatite Me/G-1. 128 Microphotograph showing spontaneous fission-tracks in sphene sample JH5. 128 Microphotograph showing faint induced fission-tracks in sphene sample JH5. 130 Microphotograph showing induced fission-tracks produced in standard glass used to calibrate reactor run. 130 Microphotograph showing induced fission-tracks in standard glass used to calibrate a reactor run. 130 LIST OF PLATES (Cont.) Microphotograph showing central part of a rectic used for measuring area from which track count was obtained. 1. 1. INTRODUCTION 1.1 SCOPE The purpose of this study is to investigate the age of porphyry mineral deposits in northern British Columbia and southwestern Yukon Territory, and wherever possible, to compare the relatively new fission- track method with the well-known potassium-argon method. In addition to dating samples from northern British Columbia and the Yukon Territory, where only reconnaissance radiometric dating is available, samples previously dated by the potassium-argon method were obtained from the Copper Mountain area, Brenda Mine and Granisle Mine to compare apatite and (or) sphene fission track ages for these samples. The isochron method is applied to potassium-argon data obtained for this study and published potassium-argon data from the Topley Intrusions and Guichon Batholith to evaluate the effect of excess initial argon on potassium-argon age determinations. A new Ar^ total vs %K, method of plotting isochrons is presented and evaluated. Finally, the concept of metallogenic epochs is evaluated for porphyry and related mineral deposits in the Canadian Cordillera in the light of the age determinations reported and the new global tectonics. Six samples from the Burwash Landing area and six samples from the Cassiar area were collected by the writer during the 1969 field season. A sample from the Granisle Mine and ten samples from the Copper Mountain area were obtained from the British Columbia Department of Mines. A sample of coarse alaskite from the Adanac Mine was obtained from W. Sirola of Kerr Addison Mines and two samples of quartz monzonite from the Syenite Range were collected for the writer by C. Godwin and K. Dawson of Atlas Exploration. 2. Biotite, hornblende, apatite, sphene and zircon were separated from the samples for dating. A sphene concentrate from quartz diorite at Brenda Mines was provided by Dr. W.H. White. Fifteen biotite K-Ar ages, two hornblende K-Ar ages and fifteen apatite fission-track ages were determined by the writer at the University of British Columbia in geochronology laboratories of the Departments of Geological Sciences and Geophysics. Parts of this study have been published: Christopher, P.A., White, W.H., and Harakal, J.E. , 1972a. K-Ar dating of the 'Cork' (Burwash Creek) Cu-Mo prospect, Burwash Landing area, Yukon Territory. Can. J. Earth Sci., 9, pp. 918-921. , 1972b. Age of molybdenum and tungsten mineralization in northern British Columbia. Can. J. Earth Sci., 9, pp. 1727-1734. Christopher, P.A., 1972. Metallogenic epochs for "porphyry type" mineral deposits in the Canadian Cordillera (Abstr.). In Proceedings of the 9th. Annual Western Inter-University Geological Conference, Vancouver, B.C. p. 15. , 1973. Application of apatite fission- track dating to the study of porphyry mineral deposits. Can. J. Earth Sci., 10, May, in press. 3. 1.2 PORPHYRY MINERAL PROPERTIES STUDIED The term porphyry copper refers to large low-grade copper deposits that are spatially, temporally and genetically related to porphyritic intrusive rocks. Porphyry mineral deposits in the Canadian Cordillera include mineral deposits of copper, molybdenum and (or) tungsten with one or more of these metals of economic interest. Sutherland Brown (1972) suggested that the porphyry deposits of the Canadian Cordillera have the following unifying characteristics: 1) Porphyry deposits consist of pervasive primary mineralization sparsely distributed in fracture or veinlet stockworks, breccias, or disseminations that are intimately related to porphyritic plutons. 2) Mineralization and alteration are distributed in porphyry or host in zonal patterns. 3) Plutons may be formed from magma of either granitic or syenitic affiliations. Sutherland Brown used variation within these unifying characteristics to classify porphyry deposits as: 1) phallic, 2) volcanic and 3) plutonic porphyry deposits. The criteria used to classify a porphyry deposit are: 1) size and shape of pluton, 2) position and distribution of mineralization and alteration, 3) stage in orogenic cycle, and 4) age relationship of deposit and host. The first two criteria can be evaluated from careful empirical observation and routine laboratory investigation. The last two criteria require sophisticated isotopic analysis of samples of the intrusive and host rocks. These later criteria, the evaluation of the age and geologic setting of porphyry mineral deposits, were investigated during this study. 4. The K-Ar method is extremely useful in age dating igneous rocks of Mesozoic and Cenozoic age. Porphyry mineral deposits in the Canadian Cordillera are of Mesozoic and Cenozoic age, and therefore, the K-Ar method is suitable for dating the age of porphyry mineral deposits. The apatite fission-track method is also useful for dating Mesozoic and Cenozoic rocks, and this method of dating porphyry mineral deposits is evaluated in sections 3.3 and 3.5. Areas studied by K-Ar and fission-track dating methods are located on Figure 1-1. The Burwash Landing area, Syenite Range, Cassiar area, and Adanac property were selected to extend the dating of porphyry mineral deposits into northern British Columbia and the Yukon Territory. Samples previously dated by the biotite K-Ar method were obtained from the Copper Mountain area (Preto et al., 1971) and the Granisle Mine (Carter, 1972b) to compare biotite K-Ar ages with apatite fission-track ages. Table 1-1 is an application of Sutherland Brown's (1972) porphyry classication to the deposits studied. 5. 1. SYENITE RANGE 2. BURWASH LANDING AREA CORK PROPERTY 3. CASSIAR AREA MT. HASKIN PROPERTY "MT. REED PROPERTY CASSIAR MOLYBDENUM 4. GRANISLE MINE 5. COPPER MOUNTAIN AREA 3A. ADANAC PROPERTY / ^ 2 c > YUKON ^ @j B.C. l«- 3A Figure 1 - 1 . Location map for areas studied. Table 1-1. Classification of deposits studied Deposit Tectonic Belt Pluton Age Host Age Shape Composition m.y. Mineralization Stage Type Burwash Insular 3000' Qtz. Creek x 1000'? latite 26.2 Permian & Cu, Mo in stock late Triassic and host Phallic Adanac Intermontane 6000' Alaskite x 3500'? 62.0 P e rmo-P enn- sylvanian & Jurassic Mo, W in stock late Phallic(?) Mt. Haskin Omineca Mt. Reed Omineca Cassiar Omineca Molybdenum Granisle Intermontane Copper Intermontane Mountain & Ingerbelle 4000' Granite x 4000' porphyry 1000' Granite x 3000'? porphyry 2000' Latite x 500' 2000' Bio.-Feld. x 1500' porphyry complex Syenite to Diorite 50.1 Cambrian 49.5 Cambrian less 70.0 51.2 Cretaceous 70.0 m.y. Triassic & Jurassic Mo in stock and late Phallic host Mo, W in stock late Phallic and host Mo, Cu in stock late Phallic and host Cu in stock and late Phallic host 193 Late Cu in stock and early Triassic host Volcanic 7. •2. POTASSIUM-ARGON DATING 2.1 INTRODUCTION The K-Ar method has been reviewed by Hamilton (1965), Damon (1968), Dalrymple and Lanphere (1969) and York and Farquhar (1972). York and Farquhar (1972) and York (1970) reviewed recent developments in K-Ar dating that include the K-Ar isochron method. The problem of radiometric dating of porphyry mineral deposits in the Canadian Cordillera involves the dating of events that occurred during Mesozoic and Cenozoic time. The K-Ar method has been extensively used for this purpose because: 1) It is suitable for dating events that occurred during the time span being investigated. 2) Most porphyry deposits contain mineral or whole-rock samples suitable for K-Ar dating. 3) The precision and accuracy required is obtained at a reasonable cost. K-Ar ages obtained for this study are used to extend the study of age of porphyry mineral deposits into northern British Columbia and the Yukon Territory and as a reference for comparing fission-track ages. In this chapter the K-Ar data is presented and examined by using the isochron method and a new Ar^® total vs %K isochron plot is suggested and evaluated. Application of the Ar 4^ rad. vs %K isochron method (section 2.3) to published K-Ar data from the Topley Intrusions and Guichon Batholith are presented in Appendix B. 2.2 K-Ar METHOD The K-Ar method of dating depends upon the decay of K^ to Ar^, both of which must be measured for an age to be calculated. Standard analytical techniques used for measuring potassium and argon have been described in detail by Hamilton (1965) , Dalrymple and Lanphere (1969) and York and Farquhar (1972). In the .present s.tudy, biotite and hornblende apparent ages were determined in K-Ar laboratories operated jointly by the Departments of Geophysics and Geological Sciences, University of British Columbia, using procedures and equipment previously described (White et al., 1967). In addition to the normal procedure, the sample and entire fusion system were baked at 130°C for 16 hours which effectively eliminates atmospheric argon contamination in the system (Roddick and Farrar, 1971). Isotopic ages of the seventeen analyzed samples are plotted on Figures 4-1 to 4-7 and analytical data given in Table 2-1. Isotopic abundances of potassium and atmospheric argon normally used for K-Ar dating were determined by Neir (1950) and are listed in Table 2-2. The assumptions made in using isotopic values have been reviewed by Dalrymple and Lanphere (1969). - 9. TABLE 2-1 Potassium-Argon Analytical Data ( a g e g o b t a i n e d  f o r t h i s stU dy) Spec men Ko. location Unit Rock Type Mineral ZKis* A 40 rad** A 6 u total A A0 rad. A^rad. (10-5 C c K 4 ° STP/g) xlO" 3 K 40 ATTC xlO 5 Ar«° I P * xlO 3 Apparent Age (m.y.) PCI Ut. long. 61*22'18" 139°18'20" Tertiary plug? Qtz. latite porphyry Biotite 7.06±0.05 0.81 0.733 1.534 8.1274 1.535 26.0+1.0 PC 2 Lat. Long. 61*22'17" 139*18'10" Tertiary plug? Qtz. latite porphyry Biotite 6.75*0.05 0.85 0.717 1.570 10.4016 1.915 26.7+1.2 PC3 Lat. Long. 61"22'30" 139*25'55" Tertiary plug? Qtz. latite porphyry Biotite 7.44*0.03 0.85 0.776 1.541 10.3722 1.885 26.2+1.0 PC4 U t . Long. 61*22'30" 139°26'08" Tertiary plug? Qtz. latite porphyry Biotite 7.30+0.03 0.83 0.757 1.533 9.2347 1.704 26.0*1.0 PC 5 Lat. Long. 61*22'00" 139*25'09" Kluane Range In- trusions Gabbro Hbl. 0.404*.001 0.56 0.190 6.943 0.5344 0.6619 115 ±4.0 PC 6 Lat. 61* 22 '05" Kluane Gabbro Hbl. 0.379+.002 0.36 0.181 7.038 0.2343 0.4590 117 +4.0 Long. 139*25'09" Range In- trusions PC7 Lat. 61*32*36" Ruby Range Biotite Biotite 6.51*0.02 0.75 1.357 3.081 2.7009 1.111 51.9*2.0 Long. 138*32*38" batholith Granodiorite PC8 U t . 61"32'36" Ruby Range Bio.-Hbl. Biotite 7.24±0.03 0.90 1.584 3.232 7.5150 2.711 54.5±2.0 Long. 138*45'30" batholith Granodiorite PC9 Lat. 59*20'25" Mt. Eaakln Granite Biotite 7.51±0.02 0.93 1.508 2.944 11.8377 3.764 49.7±1.5 Long. I29°30'22" porphyry porphyry PC10 Lat. 59*22*42" Mt. Haskin Granite Biotite 7.31*0.01 0.93 1.483 2.996 11.9294 3.853 50.5+1.5 long. 129*30'39" porphyry porphyry PCU Lat. 59*17*58" Mt. Reed Granite Biotite 7.78*0.05 0.84 1.521 2.888 5.0408 1.740 48.7*1.9 Long. 129*25'18" porphyry porphyry PC12 U t . 59*18'00" Mt. Reed Granite Biotite 7.75*0.03 0.89 1.491 2.979 8.0373 2.679 50.2+1.6 Long. 129*25'19" porphyry porphyry PC13 U t . 59°12'12" Cassiar Qtz. Biotite 6.52*0.01 0.83 1.886 4.274 3.1785 1.644 71.7*2.6 Long. 129*50'23" batholith Monzonite PC14 U t . 59*13'29" Cassiar Qtz. Biotite 7.60*0.03 0.85 2.093 4.068 4.1202 1.963 68.3*2.7 Long. 129°50'10" batholith Monzonite PC15 Lat. 59*42'30" Mt. Leonard coarse Biotite 5.16*0.04 0.89 1.287 3.685 6.2809 2.597 62.0*2.2 Long. 133*23'24" Boss Alasklte <5Z Chi.) PC16 Lat. 63*58'10" Syenite Qtz. Biotite 6.92*0.03 0.94 2.391 5.104 8.0164 4.364 85.3*2.7 Long. 137*18'10" RanRe In- Honzonlte trualons PC17 U t . 63*57*55" Syenite Qtz. Biotite 7.10*0.03 0.96 2.576 5.361 11.0437 6.183 89.5±2.7 Range In- Monzonite trusions * Potassium analyses by P. Christopher, J.E. Karakal and V. Boblk using KV and KY-3 flame photometers, a-standard deviation of quadruplicate analyses. ** Argon analyses by J.E. Harakal and P. Christopher using MS-10 mass spectrometer. Constants used in model age calculations:} e - 0.585 x 10" 10 y" " *.72 x lO-iOy" 1 . *°K/K - 1.1B1 x 10"*. 10. Table 2-2. Isotopic abundance of potassium and atmospheric argon (Data from Neir, 1950). Isotope Relative atomic abundance (per cent) A r 4 0 99.600 Ar 3 8 0.063 Ar 3 6 0.337 K 4 1 6.91 + 0.04 K 4 0 0.0119 + 0.0001 K 3 9 93.08 + 0.04 In order to determine the absolute age of a single mineral or rock sample, i t is necessary to assume that a l l argon in the rock or mineral is either radiogenic or argon with the present atmospheric ratio (i.e. Ar4(^ total = Ar4orad.+ Ar 4 0 with Atm. ratio). Because the Ar 4 0/Ar 3 6 atmospheric ratio is 295.5 (Neir, 1950), the conventional method of correcting for 'atmospheric argon' is to assume that Ar40rad.= Ar 4 (^total - 295.5 (Ar3^) . However, subsequent workers have shown variation in the i n i t i a l Ar4(^/Ar3^ ratio and an alternative graphical approach to determine the in i t i a l argon ratio has been suggested. This method is outlined below. 11. 2.3 GRAPHICAL INTERPRETATION OF K-Ar DATA Investigation of argon content of biotite (Wanless, Stevens and Loveridge, 1969; Giletti, 1971), hornblende (Roddick and Farrar, 1971), pyroxene (Hart and Dodd, 1962), plagioclase feldspar (Laughlin, 1966; Livingston et al., 1967), and nepheline (Macintyre, York and Gittens, 1969) shows that excess i n i t i a l Ar 4^ can occur in most datable minerals. Thus samples must be treated in a manner that does not assume that i n i t i a l argon has the present atmospheric ratio i f the K-Ar method is to be of use in establishing trends in age of intrusions and age of mineral deposits. The K-Ar isochron method (York et al. , 1969; McDougall et al., 1969; Roddick and Farrar, 1971; Hayatsu and Carmichael, 1970) provides a method of determining the i n i t i a l argon ratio. The data necessary for determining isochron ages is essentially the same as the data needed for the conventional K-Ar age calculation. The isochron method requires that for each rock unit dated at least two and preferably a minimum of three analyses are available from phases or minerals differing by at least 50 per cent in potassium content. In addition to the added analyses required, the entire fusion system must be baked overnight at a temperature that will remove loosely held atmospheric argon, but will not cause loss of i n i t i a l or radiogenic argon. The temperature required to clean samples properly has been empirically determined to be 130°C for 16 hours (Roddick, 1970; Roddick and Farrar, 1971). Ar4^/Ar36 vs K^O/Ar-^ and Ar 4^ radiogenic vs per cent potassium diagrams are plotted and the method of least squares (York, 1966) is used to f i t the best straight line to the points. The lines produced are called isochrons and the slope of the line is used to calculate an isochron age. 12. The (Ar 4 0/Ar 3 6) vs (K 4 0/Ar 3 6) isochron equation is: (Ar 4 0) = X e . (e X t -1) K 4 Q + (Ar 4 0) (2.1) Ar J b T Xg+ Xe Ar J b Ar36 i Where (Ar 4 0) = the total Ar 4 0 to total Ar 3 6 ratio found Ar^b T in the mineral at present. (Ar 4 0) = the i n i t i a l value of the ratio at t=0. Ar^6 i ( K 4 0) = present-day ratio of K 4 0 to Ar 3 6 in the Ar J b mineral X = Ae + Xg Xe = decay constant for electron capture by K 4 0 (0.585 x 10- 1 0yr _ 1). Xg = decay constant for beta emission by K 4° (4.72 x 10- 1 0yr _ 1). For equation 2.1 to be applicable to a set of samples, the samples must have: 1) the same age, 2) the same in i t i a l argon ratio and 3) essentially no atmospheric argon contamination. The A r 4 0 rad. vs %K isochron equation is: Ar 4 0rad. = 6.835 x IO - 4 m (%K) + A r 3 6 i (I - 295.5) (2.2) Where Ar 4 0rad. = radiogenic argon 40 expressed in cc/gm at S.T.P. and calculated assuming (Ar4°i + Ar 40 A t m.)/(Ar 36 i + A r 3 ^ ) = 295.5 m = X e (e * t-1) slope = 6.835 x 10"4 m, (Roddick, 1970, p. 59) I = i n i t i a l Ar 4 o/Ar 3 6 ratio, and Ar 3 b^; Ar 4^^ = i n i t i a l concentration. For equation 2.2 to be applicable to a set of samples, the following criteria 13. must apply: 1) samples have the same age, 2) samples have the same init i a l argon ratio, and 3) samples have the same amount of i n i t i a l argon. An exception to criterion three occurs when the i n i t i a l argon ratio is 295.5. Roddick and Farrar (1971) refer to the Ar 4 ^rad. vs %K diagram as an in i t i a l argon diagram and Roddick (1970) suggested that: "Minerals having different crystal structures will probably incorporate different amounts of i n i t i a l argon. Therefore, only the same type of minerals can be plotted on an i n i t i a l argon diagram". Because Ar 4 0 rad. is calculated assuming (Ar 4 v \ + Ar 40 Atm.)/(Ar 3b ^ + Ar36 Atm.) = 295.5, the y-intercept of the Ar 4 0 rad. vs %K diagram is Ar 3 6 ^ (I - 295.5) (Roddick and Farrar, 1971) and not i n i t i a l Ar 4 0 rad. as the Ar 4 0 rad. vs %K plot seems to suggest. A positive intercept occurs on the Ar 4 0 axis when I>295.5 and a negative intercept occurs when I<295.5. Roddick and Farrar (1971) suggest that unlike the Ar 4 0 /Ar 3 6  vs K 40 / Ar 3 ^ isochron, the Ar 4 ^ rad. vs %K isochron yields the correct age of the mineral when atmospheric argon is present in the system. However, the presence of atmospheric argon in the system eliminated any possibility of obtaining quantitative information on the i n i t i a l argon ratio and the i n i t i a l concentration of argon in the sample. The assumptions necessary for a complete K-Ar isochron determination (both Ar 4 0 /Ar 3 6  vs K 40 /Ar 36  and Ar 4 0  rad. vs ZK) are: 1) the baking procedure essentially eliminates atmospheric argon from the system, and 2) the absolute amount of A r 4 0 i = i n i t i a l Ar 4 0 /Ar 3 6 ratio and age of the samples are the same. If these assumptions hold, then an Ar 4 ^ total vs %K plot will be a valid 14. .isochron plot. The A r 4 0 total vs %K isochron equation i s : Ar 4 0 total = 6.835 x 10~4 m (%K) + A r 4 0 i (2.3) Where Ar4u" total = total Ar 4 0 measured by mass spectrometry, slope = 6.835 x IO"4 m Ar4*-^ = i n i t i a l A r 4 0 in sample at t=0 = intercept on y axis. The y-intercept for this diagram yields the absolute amount of i n i t i a l Ar 4^. 2.4 APPLICATION OF ISOCHRON METHOD Ages shown in table 2-1 were calculated assuming that Ar 4 0 total = A r 4 0 radiogenic + A r 4 0 with atmospheric ratio. Four samples from quartz latite porphyry near Burwash Creek (PCI to PC4) and four samples from granite porphyry on the Mt. Reed and Mt. Haskin properties provided independent checks on the age of these units. Isochron plots were constructed for these samples to check the i n i t i a l Ar 4 0/Ar 3^ ratio and to compare isochron results with conventional determinations obtained using the assumed 295.5 in i t i a l argon ratio. Isochron ages for these units have large uncertainties due to the small spread in potassium content of analyzed biotite concentrates. Isochron ages shown for samples PCI to PC4 in Figure 2-1 and PC9 to PC13 in Figure 2-2 show much greater uncertainty than the respective mean ages of 26.2 + 0.3 m.y. and 49.8 + 0.7 m.y. for the samples. Initial argon ratios obtained for these samples both overlap the 295.5 value within the limits of error and therefore, the isochron result is consistent with the use of the 295.5 value. 15. Regression Results i 1 i 1 i i i 0 ',. 0.4 0.8 1.2 K ^0 / A r 36 x 1 0 6 0  0 2 k 6 8 Fig. Isochron plots for quartz latite porphyry 2-i near Burwash Creek, Yukon Territory. Fig. 2-2 Isochron plots for Mt. Reed and Mt. Haskin porphyries. 17. 2.4.1 Ar 4 0 total vs %K Isochrons 40 The Ar total vs %K isochron approach was checked by using published data from Hayatsu and Carmichael (1970) and Roddick and Farrar (1971) that 40 was unsuitable for Ar rad. vs %K plots. Case I Cape Breton Whole-Rock Samples A recalculated isochron for whole-rock K-Ar data obtained by Hayatsu and Carmichael (1970) is compared with a plot of total Ar 4 0 vs %K. Argon measurements have been converted from moles/gm. to CC.STP/gm. in order to allow comparison. Data is presented in Table 2-3 and the isochron plots are shown in Figure 2-3. Discordant whole-rock K-Ar data yielded a 40 concordant Ar rad. vs %K isochron age of 391 + 5 m.y. for samples from Cape Breton Island, Nova Scotia (see Hayatsu and Carmichael, 1970) 40 with a positive intercept on the Y axis that indicated an i n i t i a l Ar / Ar 3^ ratio greater than 295.5. An Ar 4 0 total vs %K plot yields an isochron 40 parallel to the Ar corrected vs %K plot and an isochron age of 391 + 7 m.y. 40 40 The total Ar plot also has a positive intercept on the Ar axis and this value is the absolute amount of i n i t i a l A r 4 0 plus a small increment of atmos- 40 pheric Ar (less than 10%). 40 This example shows that an Ar total vs. %K isochron can correct for discordant whole-rock K-Ar data and provides a one step method of obtaining 40 the i n i t i a l Ar content of a set of samples. Case II Tulameen Complex Hornblende Samples A recalculated isochron for hornblende K-Ar data obtained by Roddick and Farrar (1971) is compared with a plot of total Ar 4 0. Data is presented in Table 2-4 and the isochron plots are shown in Figure 2-4. Discordant hornblende K-Ar data yields a concordant Ar 4 0 rad. vs %K isochron 18. TABLE Analytlc.nl data and ages of Cape Breton whole rook samples (data from Hayatsu 2-3 Carmlohael, 1970). Units for Ar^° were converted from raoles/gm to oo. STP/gm. Sample No. Book Type K (*) 4 o Ar total" (xlO - 6  00. STP/gm.) 36 Ar"* (xl0 - 1 3 moles/gm.) (xl0 - ° 00. STP/gm.) Age + (m.y.) CB-18 Basalt 0.066 3.611 2.39 2.148 680 17 Basalt 0.363 9.677 2.72 8.019 485 12 Red felslte 0.777 16.442 3.54 14.246 412 9 Crystal llthlo tuff 0.931 19.219 3.54 17.024 411 8 Greywacke 1.52 28.582 1.49 27.686 409 7 Red felslte (quartz keratophyre7) 0.040 3.237 2.30 1.830 691 IA Greymoke 1.64 30.598 2.05 29.322 402 IB Greywacke 1.57 29.277 2.08 28.000 401 2 Amygdaloidal basalt 0.098 4.771 2.47 3.024 644 3 Basalt 0.270 6.406 1.38 5.555 456 it Basalt 0.261 6.406 1.43 5.533 455 5 Bed felslte 0.595 14.381 3.22 12.365 460 f40 A r  spike. ••3̂ Ar spike subtracted. •Values of constants used are Xo= O.566,  Uo K/& •= 1.18 x 10"*(4). TABLE Analytical data and ages of hornblende from Tulameen Complex (data from Roddick 2-4 and Farrar, 197D. Ar^° total was calculated using the values for Ax* 0  rad. and percent atmospheric argon reported by Roddick and Farrar, Sample Bo. K W *°Ar total" (xl0~° cc. STP/gm.) ^ r a d (xlO - 6 CO. STP/gm.) % Atmoa. (^0 A r /36 A r) T Age and Error (m.y.) 2H-2 I.63 1 3 . 5 5 1 3 . 1 4 3 . 0 9803 1 9 1 . 5 ± 2.9 2H-3 1.63 13.61 13.15 3 . 5 8330 191.6 ± 2 . 9 5H-3 1.19 9.16 9.86 3 . 4 8631 196.6 ± 3.0 5 H - 4 1.19 10.22 9.99 3 . 8 7682 199.1 ±3.0 8H-2 1.016 10.37 8.731 4 . 8 6152 2 0 3 . 5 ± 3 . 1 X e - 0.584 x IO' 10 .*!-- 1 ! - 4.72 x 1 0 - 1 0 yr - 1 t  4 °K = 1.22 x IO" 4  g/g K. * Calculated assuming (^Arj + **°Ar.) / ( 3 6 Arj +  36 Ar.) - 295.5. 19. 32 38 24 -I & CO 20 16 o VO I 12 O Regression Results Intercept 2.742±0.4623 Slope 17.18±0.3528 Total 1.246*0.2634 17.21+0.2012 Corrected *.Total • Corrected 0.2 OA Cv6 CX8 1.0 1.2 M 1.6 Fig. T o t a l a n d c o r r e c t e d A r 4 0 v s %K i s o c h r o n s f o r w h o l e - r o c k K - A r 2-3 d a t a . C o r r e c t e d I s o c h r o n i s r e c a l c u l a t e d f r o m H a y a t s u a n d C a r m i c h a e l ' s ( 1 9 7 0 ) d a t a . zo. Regression Results Intercept 1.645 ± 0.3846 Slope 7.31 + 0.166 1.331 +0 2556 7 24± 0.110 Total Corrected Total Corrected — i 16 Fig. 2-4 02 0/ 06 0.8 1.0 12 Comparison of A r 4 0 total isochron with Ar H U corrected isochron diagram for K-Ar hornblende data from the Tulameen Complex, British Columbia (data from Roddick and Farrar, 1971). -40 14 21. age of 175 + 3 m.y. for samples from the Tulameen Complex, British Columbia (see Roddick and Farrar, 1971) and an A r 4 0 total vs %K plot yields an isochron parallel to the A r 4 0 rad. vs %K plot and an isochron age of 176 + 4 m.y. The y-intercept for the Ar 4 0 total isochron is the absolute amount of i n i t i a l A r 4 0 plus a small increment of atmospheric Ar 4 0. This example suggests that the total argon plot yields essentially the same results as the A r 4 0 rad. vs %K plot, and that the absolute amount of i n i t i a l A r 4 0 is obtained directly by using the Ar 4 0 approach. Both plots yield A r 4 0 i values of 1.6 x IO - 6 CC.STP/gm. for the Tulameen hornblende samples, but the Ar 4 0 total vs %K plot does not require the plotting of an Ar 4 0/Ar 3^ vs K^/Ar 3^ isochron in order to obtain the A r 4 ^ value. 2.5 SUMMARY Hayatsu and Carmichael (1970) and Roddick and Farrar (1971) have 40 shown that the K-Ar isochron method corrects for excess i n i t i a l Ar in a mineral sample. Since the isochron method can yield more meaningful ages, an attempt should be made to apply the method to K-Ar data. At least three samples from a single igneous event are necessary in order to establish an isochron. Samples PCI to PC4 and PC9 to PC13 were analyzed in a manner suitable for isochron determinations (Roddick and Farrar, 1971), but the narrow range of potassium values for the samples leads to isochron ages with large uncertainties (Figure 2-1 and 2-2). Isochron plots of A r 4 0 total vs %K yield the same age as Ar 4 0 rad. vs %K plots, and in addition, the A r 4 0 total vs %K plot provides a one step approach to obtaining the absolute value of i n i t i a l A r 4 0 (Figures 2-3 and 2-4) . 22. 2.6 EVALUATION OF ISOCHRON METHOD The graphical approach to potassium-argon age dating provides a new approach to data treatment and interpretation. Advantages of the graphical approach are: 1) In order to obtain meaningful ages for minerals of low K content and (or) young age, the i n i t i a l argon ratio of the minerals must be determined. In theory, the Ar^/Ar3*^ vs K 4 o/Ar 36 plot will yield the i n i t i a l argon ratio of properly treated samples of related age and history. 2) Isochron plots are useful visual and interpretative aids, these diagrams emphasize irregularities and trends in K-Ar data. 3) As information on in i t i a l argon accumulates, i t will add to our understanding of the argon retentivity of various minerals and the origin of excess argon (Hayatsu and Carmichael 1970). 4) Provides a method of correcting for high i n i t i a l argon ratios (e.g. Hayatsu and Carmichael, 1970 and Roddick and Farrar, 1971). Disadvantages of the graphical approach are: 1) Several samples must be analyzed in order to determine the i n i t i a l argon ratio. 2) Mineral samples that are from the same intrusive phase often contain similar potassium content and therefore are not suitable for isochron plots, ( e.g Samples PCI to PC4 and samples PC9 to PC13 section 2r.4) . 3) For an A r 4 0 vs %K plot to apply, samples must contain the same amount of excess argon. It is unlikely that this assumption will generally hold for more than one mineral phase. 23. 3. FISSION TRACK DATING 3.1 INTRODUCTION Recent work has established the feasibility of using the fission- track technique for dating common accessory minerals (Fleischer and Price, 1964a; Naeser, 1967b; Wagner, 1968; Christopher, 1969; Naeser and Dodge, 1969; Naeser and McK.ee, 1970); however, most of the studies to date have been carried out on samples that are from unaltered rocks that yield clean concentrates of datable major and accessory minerals. These studies have shown that the fission-track method can be used as a dating tool and does provide information on the age and crystallization history of a mineral or rock unit. The Canadian Cordillera has been established as a porphyry copper and molybdenum mineral province (Sutherland Brown et al., 1971; Sutherland Brown, 1969a) with low grade (porphyry type) mineral deposits of the 'paramagmatic class' (White, Harakal and Carter, 1968). Most examples of porphyry copper deposits exhibit a characteristic sulfide and alteration zoning that was formed in an epizonal to mesozonal environment during Mesozoic and Cenozoic times (Lowell and Guilbert, 1970; Rose, 1970). Naeser (1967a) concluded that: "...apatite, because of its property of low temperature track annealing is a very sensitive temperature monitor. It is most useful in looking at events in the Mesozoic and Cenozoic, where effects of burial are minimal". Porphyry deposits of the Canadian Cordillera should provide an ideal setting for fission track age determinations on apatite. In this chapter the fission-track method is reviewed, and the application of apatite fission-track dating to the study of porphyry mineral 24. deposits is evaluated by comparing apatite fission-track and K-Ar ages for co-genetic minerals. 3.2 FISSION-TRACK METHOD Following the discovery by K.A. Petrzhak and G.N. Flervo in the U.S.S.R. in 1940 that uranium undergoes spontaneous fission, many scientists looked for tracks of radiation damage recorded in crystal structures. Fission-tracks were first detected in irradiated flakes of the mineral muscovite by Silk and Barnes (1959). The most direct method for observing tracks is to examine irradiated solids with an electron microscope at high magnification (50,000x). This method of observing fission-tracks limited their utility until the discovery of chemical etching techniques by P.B. Price and R.W. Walker (1962) permitted the study of fission-tracks with the optical microscope. The discovery of etch techniques for revealing fission-tracks was followed by the development of the fission-track technique for dating minerals and glass (Price and Walker, 1963, p. 4847; Fleischer and Price, 1964a, p. 331 and 1964d. p. 1705). Spontaneous fission-tracks can be produced by the fission decay "of U 2 3 8, U 2 3 5, and Th 2 3 2, but Price and Walker (1963) calculated that in most cases spontaneous fission of U 2 3 8 is the only likely source of fission-tracks. Therefore, the parent material for the fission-track method is U and the daughter products of a spontaneous decay are represented by a damaged trail (fission-track). The increase in the spontaneous fission-track density is a measure of the build-up of the daughter products and the spontaneous fission-track density is directly related to the age and U 2 3 8 content of a mineral or material. 25. The fission-track method has been applied to the dating of metamorphic and igneous events ranging in age from historic times to the Precambrian. Minerals suitable for fission-track dating include: biotite, hornblende, apatite, zircon, muscovite (Fleischer and Price, 1964b) , sphene (Naeser, 1967b) and epidote (Naeser, Engels, and Dodge, 1970). Glass (Brill et al., 1964; Fleischer and Price, 1964a and b) can also be dated and most plastics are excellent track detectors. 3.2.1 Procedure The procedure for determining fission-track ages involves: a) determining the spontaneous fission-track density on an etched interior surface of a mineral. b) using the calculated value for spontaneous fission decay constant ( X F), T O O c) determining the U content. An accurate, indirect determination of the Û -̂  content can be made by exposing an annealed portion of the sample to a known dose of thermal neutrons (Fleischer et al., 1964). Thermal neutron induced fission takes place in IT*̂ -*, b ut not in Û -̂ , and therefore, the induced track density (pi) will be a function of the thermal neutron flux, the cross section capture area of Û 35 f o r thermal neutrons, and the concentration of 11^35. Once the values necessary for determination of the U"235 content are obtained, the Û 38 content can be found by using the constant isotope ratio (U235/ ij238 _ 1/137.7). From an induced track count, a spontaneous track count, and a flux determination, the age of a.mineral can be obtained from the following equation (Fleischer et al., 1965a, p. 389): 26. A = 1 In [1 + ( ps X Da Id))] * D p i A F Where A = age in years; ps = spontaneous track density (natural tracks from spontaneous decay of U 2 3 8); p i = induced track density (tracks caused by neutron induced fission of U 2 3^); AD = total decay constant for U 2 3 8 (1.54 x lCT^yr" 1) ; a = thermal neutron cross section for fission of U 2 3^ (582 x IO - 2 4 cm2) ; 4> = total thermal neutron dose (nvt) ; I = 1/137.7 = isotope ration U 2 3 5/U 2 3 8 (7.26 x IO - 3); AF = fission decay constant for U 2 3 8 (6.85 x 10 _ 1 7yr _ 1) (Fleischer and Price, 1964a, p. 63). By substituting values for the constants, the equation reduces to (Naeser, 1967b, p. 1523): A = 6.49 x 10 In [1 + (9.45 x 10" 1 8 p_s ) ] yr. p i The various steps involved in a fission-track age determination are outlined in detail in Appendix C. The reader is referred to descriptions of the analytical procedure presented by Lahoud et al. (1966), Naeser (1967a and b) and Christopher (1969). 27. 3.2.2 Flux Determination The largest analytical uncertainty in determining a fission-track age generally involves the determination of the neutron flux obtained during sample irradiation. The reactor irradiation is used for determining uranium content of samples and a neutron flux in the order of 10"^ to nvt* is required for the uranium determination. The most accurate method for determining the flux obtained during a reactor run is to include a calibrated standard with either a known uranium content or known fission-track age and count fission-tracks produced in the standard. A glass standard calibrated by Dr. C.W. Naeser of the United States Geological Survey to contain 0.4 ppm uranium was included in the reactor run along with standard apatite Me/G-1 that has concordant 120 m.y. biotite potassium-argon and 119 m.y. apatite fission-track ages. Three independent checks were used to determine the flux obtained: 1) a flux of 1.31 x lO-L̂  nvt was determined for the standard glass; 2) a flux of 1.31 x 10^ nvt was obtained by comparing track density produced in the U.B.C. reactor run with the track density of the same standard glass included in the Dartmouth reactor run 1 (Christopher 1968 and 1969); and 3) a flux of 1.30 x 10 ̂ nvt was calibrated by using 120 m.y. as the age of standard apatite Me/G-1. Although the standard deviation of three independent checks of the flux is less than one per cent, an error of 5% was assigned to the 1.31 x 1 0 n v t flux because of uncertainty in the track density produced in the standard. * nvt = total thermal neutron dose. 28. 3.3 EVALUATION OF THE FISSION TRACK METHOD Several assumptions must be made in calculation of fission-track ages, many of which cannot be assigned an absolute error. Possible sources of error in each fission-track age include determination of (1) fossil track density, ( ps), (2) induced track density ( pi), and (3) neutron dose ( t t ) . In addition, incomplete knowledge of the physical and geochemical properties of uranium may also be a source of error. The ability to distinguish tracks from inclusions, dislocations, and other imperfections in crystals has been discussed by Fleischer and Price (1964 d). The five characteristics used in identification of fission-tracks are: 1) they form line defects, 2) they are straight, 3) they are randomly oriented, 4) they are of limited length (typically of the order of 5 to 20 microns or 5 to 20 x 10 - 3 mm), and 5) they can be caused to disappear by suitable heating (Fleischer and Price, 1964 d; Wagner, 1968; Naeser and Faul, 1969). The spontaneous and induced track counts are substituted in the dating equation as a ratio, and therefore, consistent application of the above 5 criteria in the counting of both the natural and induced tracks will help eliminate counting error. In natural mineral samples, the uranium isotope U 2 3 8 is the only element for which spontaneous fission is significant. Spontaneous fission of U 2 3^ and Th 2 3 2 also occur, but U 2 3^ would account for less than 0.5 per cent of the spontaneous fission tracks in a mineral and Th would make a 50 per cent contribution only in a substance in which i t was approx- imately 100',000 time more abundant than uranium (Faul, 1966). Cosmic-ray interaction could produce radiation damage similar to fission-tracks, but the effect of the cosmic ray flux on buried terrestrial samples is considered to be negligible because of strong attenuation by rock or soil 2 9 . (Price and Walker, 1 9 6 3 ) . Uranium in nature is predominately composed of two radioactive 2 3 5 2 3 8 isotopes U and U . These two isotopes have always been found to occur together in nature with the phases intimately mixed and in a 2 3 5 2 3 8 fixed proportion (U /U = 1 / 1 3 7 . 7 + 0 . 3 ) (Senftle et al., 1 9 5 7 ) . 2 3 5 2 3 8 U and U also decay by alpha emission with half lives of 7 . 1 3 x 8 9 1 0 yrs. and 4 . 5 1 x 1 0 yrs. respectively. Price and Walker ( 1 9 6 3 ) calculated that the effect of parent reduction because of alpha decay is 9 significant when the time involved is greater than approximately 1 0 yrs. 2 3 8 The value of the fission decay constant for U directly controls the accuracy of ages calculated by the fission-track method (Price and Walker, 1 9 6 3 ) . Fleischer and Price ( 1 9 6 4 a and c) determined a weighted - 1 7 - 1 average value of 6.85 + 0 . 2 0 x 1 0 yr for the decay constant for 2 3 8 spontaneous fission of U ( ?F). This average value was obtained by using two track counting methods that gave concordant results. The first value, / I F = 6.9 x 1 0 ~^yr \ was obtained by requiring that ages of a large number of minerals determined by using the fission-track method agree with ages determined by decay of and Rb^. The second value, 7lF = 6.6 + 0 . 8 x 1 0 yr , was determined by counting fission-tracks recorded in mica SSTR held against a sheet of uranium f o i l for six months. Fleischer and Price's weighted average value for /IF = 6 . 8 5 + 0..20 x 1 0 yr ^ is supported by a value of /IF = 7 . 0 3 + 0 . 1 1 x 1 0 "^yr ^ (Roberts et al., 1 9 6 8 ) determined using standard mica SSTR against uranium f o i l , and a value of 6.8 + 0.6 x 1 0 "^yr ^ (Kleeman and Lovering, 1 9 7 1 ) determined by accumulating fission fragment tracks in Lexan plastic held adjacent to 30. uranium metal for one year. Values for A-p ranging from 8.27 to 8.42 x lO'-^yr - 1 have been determined by Spadavecchia and Hahn (1967) and Galliker et al. (1970), using a 'spinner' apparatus. The larger values are not commonly used for fission-track dating and the weighted average value of Ap = 6.85 +0.20 x 10" 1 7yr - 1 (Fleischer and Price, 1964 a and c) was used in this study. A closed system for uranium is assumed. This assumption can be checked by careful observation of the position of natural and induced tracks in a substance. Irregularities in the uranium distribution are also detectable during fission-track counting. If extreme irregularities are found (e.g. sphene sample JH5 from Brenda Mine), the sample cannot be age dated by random counting methods. The accuracy of the flux determination has been discussed by Fleischer, Price and Walker (1964). A value of 1.31 + 0.07 x 10^ n v t was determined for the reactor run used for irradiating samples studied by the writer. Fleischer, Price and Walker (1964) showed that flux variation over a 5 cm length is about 10% and they estimated that the total error in the flux determination is about 15%. Samples used in this study were irradiated over a tube length of less than 2 centimeters and therefore flux variation should be about 3%. Error in the flux determination is caused by uncertainty in the uranium content of the standard, variation of the flux within the reactor, counting error, and uncertainty in constants assigned to isotope ratios and capture cross sections. Naeser (1967b) suggested that the number of tracks counted provided the major source of error in a fission-track age determination. If a minimum of 400 fossil and induced tracks are counted, the error for each 31. slide is + 5%, a value obtained by assuming a Poisson distribution, (i.e. the standard deviation of the track counts is the square root of the number of tracks counted). Empirically, Naeser and Dodge (1969) determined that + 10 per cent is a good estimate of the standard deviation of a fission-track age, assuming at least 250 counts of both fossil and induced tracks. For this study an error of + 10 per cent is considered to be a good estimate of the standard deviation of a fission-track age when at least 400 counts of both fossil and induced tracks are obtained. When total counts are less than 400, the standard deviation was calculated by taking the square root of the sum of the squares of the estimated error (10%) and the standard deviations of counting error for natural and induced tracks. 32. 3.4 PRESENTATION OF DATA Analytical data and the calculated fission-track ages measured on fifteen apatite concentrates from five localities (Figure 1-1) in the Canadian Cordillera are shown in Table 3-1. Analytical data for standard apatite samples Me/G-1 and Me/N-1 are also presented (see Christopher 1968 and 1969). K-Ar ages obtained at the University of British Columbia on co-genetic biotite are shown for comparison. The biotite K-Ar ages are believed to represent the time at which the rock cooled to a temperature at which biotite retains argon (about 150°C) , and for high-level epizonal and mesozonal igneous bodies, the time of emplacement and time of setting of the biotite K-Ar clock should be relatively close. Seven sphene and two zircon samples were also prepared for fission- track dating but etched grain mounts revealed extreme irregularities in uranium content, and the sphene and zircon samples could not be dated by using random track counting methods. An alternate procedure for dating minerals with non-uniform uranium content has been described by Naeser (1967 a and b), but samples were not irradiated in a manner suitable for treating samples with non-uniform uranium content. TABLE 3-1 FISSION TRACK ANALYTICAL DATA AND AGES (thermal neutron flux - 1.31 X IO 15 ) Minerals Tracks Traok Tracks Track Uranium Etch Fission K-Ar Age Dated Counted Density Counted Density Content Time Traok (m.y.) Sts f\ In ppm (seo.) Age (counts/cm') (counts/cm') (m.y.) xl05 xlO5 BURWASH LANDING AREA PCI Tertiary plug? Apatite Biotite 86 1.08 296 2.04 5.6 15 42±7 26.Oil.0 PC2 Tertiary plug? Apatite Apatite Biotite 1.53 0.91 466 301 2.27 2.10 6.3 5.8 10 15 5̂ ±6 " 35±5 26.7±1.2 PC3 Tertiary plug? Apatite Biotite 419 2.03 428 3.48 9.6 10 47±5 26.2±1.0 PC8 Ruby Range batholith Apatite Biotite 170 1.94 411 3.17 8.7 10 49+7 5^.5+2.0 CASSIAR AREA PC9 Bt. Haskin porphyry Apatite Apatite Biotite 416 316 2.58 2.92 310 336 4.28 3.89 11.8 10.7 15 12 48±6 60±8 49.7+1.5 PC12 Kt. Reed porphyry Apatite Biotite 144 2.71 593 4.04 11.1 13 54±7 50.2+1.6 PC13 Cassiar Intrusions Apatite Biotite 880 4.90 1094 5.87 16.2 10 6?±7 - ?1.7±2.6 PC14 Cassiar Intrusions Apatite Biotite 660 3.59 734 4.85 13.4 10 6o±6' '•• 68.3±2.7 SYENITE RANGE PC16 Syenite .. Range Intrusions Apatite Biotite 702 7.74 934 8.18 22.5 10 '.76±8.. 85.3±2.7 PCI? Syenite Range Intrusions Apatite Biotite 187 9.92 COPPER 468 MOUNTAIN 6.48 AREA 17.9 15 121±l6 89.5+2.7 KA1 Lost Horse intrusion Apatite Biotite 616 9.17 472 6.25 17.2 10 117±12 194+8 XA4 Verde Creek Apatite qtz. monz. Biotite 571 7.50 52 4.64 12.8 10 129+23 101±4 KA9 Lost Horse (dike) Apatite Biotite 326 3.27 428 2.67 7.4 12 101±12 197±8 KA10 Lost Horse intrusion Apatite Apatite Biotite 381 292 5.02 6.02 271 151 3.97 3.77 10.9 10.4 10 15 101±13 127±18 195+8 GRAN ISLE MINE HC-69-8apatlte bearing vein Apatite Biotite 231 3.09 191 6.39 23.1 10 30±4 '. 50.2±2.1 STANDARD APATITE Ke/G-1 Apatite Apatite* Apatite* Biotite Apatite** 859 1120 2087 7.46 9.12 9.61 606 816 1588 4.95 6.4o 7.52 13.6 15.1 17.7 10 10 13-15 120+.12 133+20 119±18 113 120 Ke/N-1 Apatite Apatite• ApaKlte* Apatite* Apatite** 761 " 504 • •558-. 879 " 6.38 5*45 -7.27' 5.58 456 434 579 588 3.34' 3.79 5.71' 3.89 9.2 10.4 13.4 9.6 10" 15 - '1-5 15 152±15 115112 119±18 , 134±13 101 * Ages determined by the writer at Dartmouth College (Christopher 1968 and I969). ** Ages determined at Dartmouth College (personal communication J.B. Lyons 1971). Sample Unit No. 34. .3.5 DISCUSSION OF FISSION TRACK RESULTS Figure 3-1 is a graphical comparison of the results obtained for biotite K-Ar and apatite fission-track methods. It demonstrates that fission-track ages for apatite from the Burwash Landing area, Cassiar area and Syenite Range are consistent and in general concordant with K-Ar ages determined on co-genetic biotite; and that one sample from a mineralized potassic-zone vein at the Granisle Mine and four samples from the Copper Mountain area show discordant results. Thin section investigation revealed that co-genetic minerals obtained from weakly altered (potassic zone) rocks give concordant results and that discordant results are obtained from strongly altered propylitic and potassic zone rocks. Alteration of apatite makes track distinguishing more difficult, thus eliminating the possibility of using several of the apatite concentrates prepared for this study from the Copper Mountain intrusions. Thermal events have been suggested by Naeser (1967a), Naeser and McKee (1970), and Wagner and Reimer (1972) to explain apatite fission- track ages that are younger than the biotite K-Ar age for the sample. Annealing studies on apatite by Naeser (1967a), Naeser and Faul (1969) and Wagner (1968) show that fission-tracks in apatite are very sensitive to thermal events, and that a temperature of less than 75°C is necessary for complete track retention. Concordant apatite fission-track and biotite K-Ar ages suggest that the rock unit cooled from greater than 150°C (Damon 1968) to less than 75°C (Naeser and Faul 1969; Wagner, 1968) within a length of time less than the experimental error of the techniques. An apatite fission-track age younger than a biotite K-Ar age for a unit 35. Fig. Graphical comparison of apatite fission-track and biotite pottasium- 3-1 argon apparent ages. Potassium-argon ages determined at the University of British Columbia have been shown to be accurate within 3 per cent (J. Harakal personal communication). 36. indicates that either slow cooling or mild reheating in the temperature range 150°C to 75°C annealed fission-tracks from apatite while argon was being retained by biotite. If apatite fission track ages are older than K-Ar ages on co-genetic biotite, the discrepancy is difficult to explain. A mean apatite fission-track age of 111 + 7 m.y. from samples KA1, KA9, and KA10 from the Copper Mountain intrusions is considerably younger than the mean biotite K-Ar age of 195 + 2 m.y. for the samples. The consistently low ages obtained for apatite from the Copper Mountain intrusions suggest a thermal event that was strong enough to reset the apatite fission-track clocks but not the biotite K-Ar clocks. A temperatur between 150°C and 75°C associated with a Cretaceous thermal event would account for the difference in apparent apatite fission-track and biotite K-Ar ages. Concordance of apatite fission-track and biotite or hornblende K-Ar ages increases the reliability of an absolute age determination. Samples from the Cassiar area, Syenite Range, and Burwash Landing area generally have concordant biotite K-Ar and apatite fission-track ages. These findings suggest that the apatite fission-track method is a suitable absolut age dating method for late Mesozoic and Cenozoic igneous events in the Cassiar area, Burwash Landing area and Syenite Range. 37. 3.6 COMPARISON OF K-Ar AND FISSION-TRACK DATING TECHNIQUES Apatite fission-track ages of samples dated in this study are both concordant and discordant with K-Ar dates on co-genetic biotite or hornblende from the same sample. Young apatite fission-track ages have been attributed to the sensitive annealing character of fission-tracks in apatite (Naeser, 1967 a and b; Wagner, 1968; Christopher, 1969; Engels and Crowder, 1971). Apatite maintained at a temperature in excess of 50°C for a million years will lose 10 per cent of its tracks, and i f the temperature is maintained in excess of 175°C, al l accumulated fission- tracks will be annealed (Naeser and Faul, 1969) . Each mineral suitable for fission-track dating has a different temperature range for track annealing (Fleischer et al., 1965b; Naeser and Faul, 1969; Wagner, 1968). Figure 3-2 is a summary of annealing studies. In principle, dating a suite of minerals from the same site allows a thermal history to be constructed (e.g. Naeser, 1967 a and b; Engels and Crowder, 1971). Lowering of K-Ar ages can also be caused by heating, but for biotite and hornblende, the loss of argon does not begin until a temperature of approximately 150°C is reached (Damon, 1968). Hornblende is more resistant to argon loss than biotite, but for either mineral, essentially a l l argon will be retained when fission-tracks are being annealed from apatite at temperatures between 75 and 175°C. K-Ar ages, obtained in conjunction with apatite or other fission-track ages, help resolve the thermal history of an area. The simplicity of the apatite fission-track method is an appealing 38. 10" 800 700 600 300 400 -i r / / / / / »' T E M P E R A T U R E ( ° C ) 300 ZOO 150 100 SO 7^ T 10' y n 10' y r i - 10' yr«- .- in* I0V yrt 10* io°L o.i o • o J * / 7 " / 4 w / / 7 y—7—y / / / / i - l T iv / / y—f /////•• . win/ / Win/ •// ^7- // / ' E X P L A N A T I O N Epidott S p h t n t -6 A p o t i t t Circlid points from Wogntr (1968) 1.2 1.4 1.6 l . t £.0 2.2 2.4 T E M P E R A T U R E ( - ! f £ S ) 2.6 2.S 3.0 3.2 Pig. Track-loss curves for epidote, sphene, and apatite (3-2). (from Naeser and Dodge, 1969). 39. feature. Because normal laboratory equipment is used for fission- track dating, the experimental costs are minimal. The main cost of a fission-track determination involves the thermal neutron irradiation. Neutron irradiation services are commerically available, and by including several samples in a reactor run, the cost per sample is less than ten dollars. After obtaining mounted and polished thin sections for normal and irradiated sample portions, the time needed for making a fission-track age determination will depend upon the fission-track density. An apatite fission-track age determination should take between 2 and 6 hours (Naeser and McKee, 1970) i f between 10 and 20 grains are examined. For this study, track counting time was between 4 and 8 hours. The time necessary for a complete K-Ar analysis, including both potassium and argon analysis, is about 6 to 10 hours. In addition, the K-Ar analysis must be spread over several days. Because only a few grains of sample are necessary for a fission- track determination, the mineral separation time is short and mineral concentrates can be obtained as by-products of mica and amphibole mineral separations. Rocks that are poor in micas and amphiboles are not easily dated by K-Ar and Rb-Sr methods, but should be datable by the fission- track method. For samples with less than 50% atmospheric argon contamination, the precision of replicate K-Ar age determinations in the University of British Columbia K-Ar laboratory is within 1% and the accuracy within 3% (J.A. Harakal, personal communication, 1972). The amount of analytical 40. uncertainty is greater for fission-track age determinations. Empirically, Naeser and Dodge (1969) have determined that + 10% is a good estimate of 1 standard deviation in a fission-track age determination. Accuracy estimates for fission-track age determination cannot be made because of lack of interlaboratory comparison. 3.7 SUMMARY AND CONCLUSIONS Fifteen apatite fission-track ages were obtained for apatite concentrates from six areas in British Columbia and the Yukon Territory. Apatite fission-track ages obtained from epizonal and mesozonal intrusions with porphyry mineral deposit affinity are consistent and generally concordant with biotite K-Ar ages where alteration is weak. Apatite samples from the Copper Mountain area and from the Granisle Mine were difficult to date using the fission-track method because of the altered nature of the apatite. Three apatite fission-track ages from the Copper Mountain intrusions have a mean age of 111 + 7 m.y. This mean age is interpreted to reflect a heating event that is related to Early to Middle Cretaceous granitic intrusion. Because biotite K-Ar ages in the Copper Mountain area are affected only by contact thermal events, and apatite fission-track ages appear to be regionally reset, temperatures between the minimum annealing temperature of apatite (approximately 75°C) and the minimum temperature for argon loss from biotite (approximately 150°C) are suggested for a regional thermal event of Cretaceous age. Without additional geologic and geochronologic evidence, apatite fission-track ages from the Copper Mountain area and the Granisle Mine give misleading results with resulting misinterpretation of thermal history. Therefore, in cases where alteration is involved or thermal events are suspected, apatite fission-track ages should be checked by using another more refractory mineral or another radiometric clock. A comparison of fifteen apatite fission-track ages with K-Ar ages (Figure 3-1) demonstrates that the apatite fission-track method can be used to age date porphyry mineral deposits, however the K-Ar method is generally more suitable in terms of cost and reliability. 4. AREAS. STUDIED 4.1 INTRODUCTION Areas studied are located on Figure 1-1. This chapter outlines the geologic setting and age of the areas studied. In addition the K-Ar and fission-track methods are compared for these areas. 4.2 SYENITE RANGE, YUKON TERRITORY 4.2.1 Introduction Syenite Range is located about 60 miles southeast of Dawson City, Yukon Territory and 50 miles west-northwest of Mayo, Yukon Territory in the Yukon Plateau near the northeast flank of the Tintina Trench. Along the Tintina Trench and near its northeast flank are many bodies of course light grey granite commonly containing abundant feldspar phenocrysts (Bostock, 1948). These granitic bodies have been mapped by Bostock (1964) as Jurassic and (or) Cretaceous Coast Intrusions. The Syenite Range is composed of a composite stock of these coarse-grained granitic and syenitic rocks arranged in concentric zones with an outer zone of porphyritic syenite and a core of porphyritic granite (Bostock, 1948). 4.2.2 General Geology and Geochronology Figure 4-1 shows the general geology and geochronology of the Syenite Range. Granitic rocks that compose the Syenite Range intrude Paleozoic sedimentary rocks. Similar granitic rocks of Cretaceous age occur in the Mayo Lake, Scougale Creek and McQuesten Lake map areas (Green, 1971). 43. 137°30' 137°15' Figure 4-1. General geology and geochronology of the Syenite Range, Yukon Territory (geology after Bostock, 1964). 44. A Cretaceous age for granitic rocks of the Syenite Range is supported by f i e l d relationships and a number of radiometric age determinations. To the north and east of the Syenite Range, similar granitic rocks intrude the Keno H i l l Quartzite of probable Early Cretaceous age (Green, 1971) and about 50 miles west of the Syenite Range in the Tintina Trench, similar granitic debris is present in Tertiary conglomerates (Green, 1972). 4.2.3 Radiometric Dating Table 4-1 summarizes fission-track and K-Ar ages obtained for co-genetic biotite and apatite samples PC16 and PC17. Both rock samples contain about 5% .biotite that is weakly altered along cleavage edges and grain boundaries to chlorite. Biotite K-Ar ages of 85.3 + 2.7 m.y. and 89.5 + 2.7 m.y. were obtained for specimens PC16 and PC17 respectively. These ages are similar to biotite K-Ar ages of 85 + 7 m.y. (GSC 65-50) from a quartz monzonite stock about 25 miles south of the Syenite Range and 81+5 m.y. (GSC 65-49) from quartz porphyry in the Keno H i l l area about 50 miles northeast of the Syenite Range. An apatite fission-track age of 76+8 m.y. for sample PC16 is concordant with the 85.3 +2.7 m.y. biotite K-Ar age for the sample. An apatite fission-track age of 121 + 16 m.y. for sample PC17 is discordant with the 89.5 +2.7 m.y. biotite K-Ar age for the sample. The large uncertainty for the apatite fission-track age (16 m.y.) is caused by the small number (187) of spontaneous fission-tracks counted. 4.2.4 Conclusions The biotite K-Ar ages (85.3 + 2.7 and 89.5 + 2.7 m.y.) and apatite fission-track ages (76 + 8 and 121 + 16 m.y.) are mainly Late Cretaceous as defined in Wanless et a l . (1972). These ages are in agreement with 45. others (Gabrielse, 1967, p. 286),obtained from an arc of relatively small granitic intrusions strung out along the northeast side of the Tintina Trench. Table 4-1 Fission-track and K-Ar ages obtained for granitic rocks in the Syenite Range, Yukon Territory. Sample Unit Rock Mineral Fission- K-Ar Number Type dated track age* age** (m.y.) (m.y.) PC16 Syenite Qtz. apatite 76 + 8 Range monz. biotite 85.3 ± 2 - 7 intrusions PC17 Syenite Qtz. apatite 121 + 16 Range monz. biotite 89.5 ± 2 - 7 intrusions * Fission-track analyses by P.A. Christopher. Constants used in model age calculations:X p f o r U 2 3 8 = 6.85 x 10" 1 7Yr _ 1; \ D for U 2 3 8 = 1.54 x lO-iOyr - 1; a for U 2 3 5 = 582 x 10_24cm^. ** Argon analyses by J . E . Harakal and P.A. Christopher using MS-10 mass spectrometer. Constants used in model age calculations:X e = 0.585 x 10- 1 0yr - 1; Ag = 4.72 x 10~ 1 0yr - 1; 40K/K = 1.181 x IO - 4. 4.3 CORK (BURWASH CREEK) Cu-Mo PROSPECT 4.3.1 Introduction Eight K-Ar and four apatite fission-track ages were obtained from granitic and porphyritic textured intrusive rocks in the Burwash Landing area of southwestern Yukon Territory. Six of the samples were selected because of their spatial relationship to a porphyry Cu-Mo prospect on Burwash Creek, and two samples were collected to check the age of the Ruby 46. Range batholith to the east of Burwash Landing. Figures 4-2 and 4-3 show sample locations and outline the geology in the Burwash Landing area. The Cork property lies in the northern segment of the Insular tectonic belt (Sutherland Brown et al., 1971). The area is part of the St. Elias Fold Belt, and consists of an eugeosynclinal assemblage of sedimentary, volcanic and intrusive rocks with ages ranging from Devonian to Tertiary. High level porphyritic intrusive rocks near Burwash Creek have been mapped as Tertiary age by Muller (1967) on the basis of their chemical and textural similarity to s i l l s , dikes, and small stocks that cut Tertiary sediments in the St. Elias Fold Belt. The Cork Cu-Mo prospect occurs in and around a body of quartz latite porphyry that intrudes sedimentary and volcanic rocks of late Paleozoic (Cache Creek Group) and early Mesozoic age (Mush Lake Group). An unmineralized gabbroic stock, mapped as part of the Cretaceous (?) Kluane Range intrusions (Muller, 1967), occurs along the southern margin of the Cork property. Shakwak Trench, a major transcurrent fault zone, separates mainly volcanic and sedimentary rocks of the St. Elias Mountains to the southwest (Insular Belt) from mainly granitic and metamorphic rocks of the Yukon Plateau to the northeast (Coast Crystalline Belt) . The Yukon Complex and the Ruby Range batholith are the major components of the Coast Crystalline Belt in the Burwash Landing area. The Ruby Range batholith is considered by Muller(1967) as part of the Coast Intrusions. The age of the Ruby Range batholith cannot be determined directly by its relationship to fossiliferous beds (Muller, 1967). Biotite K-Ar age determinations on quartz monzonite L E G E N D LIMIT OF ROCK EXPOSURE GEOLOGIC CONTACT THRUST FAULT FELDSPAR PORPHYRY HORNFELS f y j RUBY RANGE BATHOLITH ICEFIELD RANGE INTRUSIONS gH^j KLUANE RANGE INTRUSIONS f j l i MUSH LAKE GROUP 1 | PERIDOTITE AND GABBRO CACHE CREEK GROUP t&$| YUKON COMPLEX FIG.4-2 General geology and geochronology in the Burwash Landing area, Yukon Territory. Geology after Muller (1967). *S!~M'Y  G S C s a m p l e  LOCATION AND AGE (Lowden I960) % % ' SAMPLE LOCATION AND AGE IN M.Y. (this report) FIG. 4-3 General geology and geochronology of the Cork prospect (for legend see Fig.2-3. 48. and granodiorite from the Ruby Range batholith have yielded early Tertiary and Jurassic ages (Lowden, 1960; 1961). A 58 m.y. biotite K-Ar age was obtained from gneissic biotite granodiorite east of Burwash Landing. 4.3.2 Potassium-Argon Results Isotopic age of the.8 analyzed samples are plotted on Figures 4-2 and 4-3. Table 4-2 summarizes K-Ar and apatite fission-track aged obtained for granitic rocks from the Burwash Landing area. Specimens PC3 and PC4 were collected from a mineralized quartz latite porphyry stock located on the Cork property. Specimens PCI and PC2 were collected from a chemically and texturally similar but unmineralized stock 3 miles east of" the Cork property. These porphyritic rocks contain from 1-4% biotite as phenocrysts with minor chlorite alteration along cleavage planes and crystal boundaries. Unaltered hornblende concentrates were obtained from gabbro specimens PC5 and PC6 from the Cork property, and unaltered biotite concentrates were obtained from granodiorite specimens PC7 and PC8 from the Ruby Range batholith. 4.3.3 Fission-Track Results Apatite concentrates were obtained from samples PCI, PC2, PC3, and PC8. The 48.9 + 6.6 m.y. apatite fission-track age.-determined for sample PC8 from the Ruby Range batholith is concordant with and provides support for the 54.5 + 2.0 m.y. biotite K-Ar age determined for this sample. Apatite fission-track ages ranging from 42.4 to 46.6 m.y. (PCI to PC3) were obtained for the porphyritic rocks near Burwash Creek. These age are Table 4-2. Fission-track and K-Ar ages obtained for granitic rocks in the Burwash Landing area, Yukon Territory. Sample Number Unit Rock Type Mineral dated Fission- track age* (m.y.) K-Ar age (m.y.) PCI PC2 PC3 PC4 PC 5 PC6 PC7 PC8 Tertiary stock (?) Tertiary stock (?) Tertiary stock (?) Tertiary stock (?) Kluane Range Intrusions Kluane Range Intrusions Ruby Range batholith Ruby Range batholith Qtz. latite porphyry Qtz. latite porphyry Qtz. latite porphyry Qtz. latite porphyry Gabbro Gabbro Bio. granodiorite apatite biotite apatite apatite biotite apatite biotite biotite hbl. 42 + 7 hbl. biotite 54 + 6 35 + 5 47 + 5 Bio.-Hbl. apatite granodiorite bio. 26.1 + 1.0 26.7 + 1.2 ~ 26.2 + 1.0 26.0 + 1.0 115 +4.0 117 + 4.0 51.9 + 2.0 49+7 54.5 + 2.0 Note: Porphyritic latite sample CKD-1 from the Cork property has a K-Ar age of 26.2 +0.4 m.y. and hornblende diorite sample JCD-1 from the Kluane Range intrusions on the Cork property has a K-Ar age of 111.7 + 2 m.y. (D.C. Way written communication, December 1972). Samples CKD-1 and JCD-1 were analysed by Dr. E. Farrar of the Department of Geological Sciences, Queen's University, Kingston, Ontario. * Fission-track analyses by P.A. Christopher. Constants used in model age calculations: f°r U 2 3 8 = 6.85 x 10 _ 1 7yr _ : L; A D for U 2 3 8 = 1.54 x 10- 1 0yr - 1; a for U235 = 582 x IO - 2 4 cm2. ** Argon analyses by J.E. Harakal and P.A. Christopher using MS-10 mass spectrometer. Constants used in model age calculations: Ae= 0.585 x i o - i o y r - i . A g = 4 > 7 2 x 1 0 - i 0 y r - i . 4 0 K / K m 1 1 8 1 x 1 0 _4 > 50. consistently older than the mean 26.2 +0.3 m.y. biotite K-Ar age determined for samples PCI to PC4, but both methods support the Tertiary age assigned to this unit by Muller (1967). The reason for consistently older apatite fission-track ages is not clear. Older apatite fission-track apparent ages relative to biotite K-Ar apparent ages are difficult to explain because argon is retained in biotite at a temperature that will cause annealing of fission-tracks in apatite (Naeser, 1967a; Naeser and Faul, 1969). It is unlikely that secondary biotite could have formed without the annealing of primary apatite grains and the discrete biotite grains and books appear to be primary biotite. If weathering was important in lowering the K-Ar age, it is not indicated by the small deviation in the four biotite K-Ar apparent ages, in thin section examination of rocks, or microscopic examination of biotite concentrates. The most likely explanation for the discrepancy is a slight bias in counting which might result because of the extremely low spontaneous track density and the small spontaneous to induced track density ratio. A consistent bias could explain the older ages. 4.3.4 Discussion The 26.2 + 0.3 m.y. mean biotite K-Ar age determined for quartz latite porphyry (PCI - PC4) is the best age for emplacement of this unit. Samples were analyzed in a manner suitable for isochron determinations (Roddick and Farrar, 1971), but the narrow range of potassium values for the samples leads to isochron ages with large uncertainties (see section 2.4). The 115 + 4 m.y. and 117 + 4 m.y. hornblende K-Ar ages determined for Kluane Range Intrusions on the Cork property agree with the Cretaceous age 51. assigned to this unit by Muller (1967). The 51.9 + 2.0 m.y. and 54.5 +2.0 m.y. biotite K-Ar ages determined for the Ruby Range batholith are slightly younger than the Geologic Survey of Canada age of 58 m.y. (Lowdon, 1961). Tertiary apatite fission-track ages determined for quartz latite porphyry near Burwash Creek and for one sample (PC8) from the Ruby Range batholith are consistent with biotite K-Ar ages and the Tertiary ages suggested for these units by Muller (1967). Both mineralized and barren quartz latite porphyry near Burwash Creek yield ages which are identical within the limits of detection and precision of the K-Ar method. This agrees with the findings of White et al. (1968) that for many British Columbia porphyry mineral deposits, mineralization is an integral feature of a magmatic event. The Cork prospect is in a large belt of Tertiary volcanic and intrusive rocks which extend through the St. Elias Mountains and adjacent Alaska Range (Muller, 1967 p. 102). This belt may contain other similar Tertiary porphyry type mineral deposits. 4.4. NORTHERN BRITISH COLUMBIA 4.4.1 Introduction Seven biotite K-Ar ages and four apatite fission-track ages (Table 4-3) were determined for porphyritic intrusions in northern British Columbia (Figures 4-4 and 4-5). Samples were selected because of their spatial and temporal relationship to Mo and Mo-W deposits in the Cassiar and Atlin areas. Sutherland Brown et al. (1971) suggested that an area extending from the Coast Crystalline Belt-Intermontane Belt boundary in the Atlin area across 52. PC L E GEND GRANITE PORPHYRY ATAN GROUP I | CHERT and OUARTZITE IjjijjiJ LIMESTONE, DOLOMITE and SKARN tggSI METASEOIMENTS and UNDIVIDED 1 SEDIMENTS SAMPLE LOCATION and AGE in M.Y. l l l l l i l l f c L EGEND fO CASSIAR INTRUSIONS PTI ULTRAMAFICS ft SERPENTINE £3 SYLVESTER GROUP MM POST ATAN GROUP ^ SEDIMENTS (UNDIVIDED! E33 ATAN GROUP EJJJGOOD HOPE GROUP l 50.2*1.6 =̂ «&3's1fr<* âgi:::::;;y!! si.-S-S-iiS.. Figure 4-4. General geology and geochronology in the Cassiar area, B.C. (after Gabrielse, 1963), Mt. Haskin Mo Property (after G. Lamont, 1971, unpublished mapping) and Mt. Reed Mo-W property (after P. Hirst, 1969, unpublished mapping). LEGEND TERTIARY S P A R S E PORPHYRY C R O W D E D PORPHYRY :\MOLLY COARSE A L A S K I T E L PTT3 Q T Z MONZONITE ^ PORPHYRY JURASSIC fj3 FOURTH of JULY C R E E K CARBONIFEROUS £2*] C A C H E C R E E K GROUP © PC 15 S A M P L E L O C . 62.0*2.2 and A G E in M.Y ^te?-'>&7t* ..... {.ft** SCALE IN FEET "WW W U * » . « ¥ v W ' / < V V V V V V » V V V V V V V V V V » » S C X f J ' O v v v V V V V V V V V V V V V ' ^ V V V V V V V V V V V V V V V V V V V V " — V V V V V V V V V V V V V V V vr v  v v v v v v v v v v v v v v v v v v v v v • V V V V V V V V V V V W , V V V V V V V V V V V V V V V V V V V V V V V V , •< V V v v v V V vv>>0 V V V V V V V V V V V V V V V V V V V V V V V ' / • v v v v v v v • V v v v v v v v v v v v v v v v v v v v v v v v . ' V V V VV" v v v v v v v v v v v v v v v v v v v v v v v v v / • ' V ^ v v v v v v v v v v v - v pc 15 ' W W W ' JVVVVVS R O I J ' v v v v v y Figure 4-5. General geology and geochronology in the Atlin Area (after Aitken, 1959) and of the Adera Claims - Adanac Mo property (after Sutherland Brown, 1969b) CO 54. Table 4-3. Fission-track and K-Ar ages of granitic rocks in northern British Columbia. Sample Number Unit Rock Type Mineral dated Fission- .K-Ar age** track age* (m.y.) (m.y.) CASSIAR AREA PC9 Mt. Haskin porphyry Granite porphyry apatite apatite biotite 48 + 6 60+8 49.7 + 1.5 PC10 Mt. Haskin porphyry Granite porphyry biotite 50.5 + 1.5 PC11 Mt. Reed porphyry Granite porphyry biotite 48.7 + 1.9 PC12 Mt. Reed porphyry Granite porphyry apatite biotite 54 + 7 50.2 + 1.6 PC13 Cassiar intrusions Quartz monzonite apatite biotite 67 + 7 71.7 +2.6 PC14 Cassiar intrusions Quartz monzonite ATLIN apatite biotite AREA 60+6 68.3 + 2.7 PC15 Mt. Leonard Boss coarse Alaskite biotite 62.0 + 2.2 * Fission-track analyses by P.A. Christopher. Constants used in model age calculations: XF f ° r U 2 3 8 = 6.85 x l O ' l A r r - 1 ; ^ f o r U 2 3 8 =6.85 x 10" 1 7yr~l; \ D for U 2 3 8 = 1.54 x 10- 1 0yr 1 ; a for U 2 3 5 = 582 x IO" 2 4 cm' '**' Argon analyses by J.E. Harakal and P.A. Christopher using MS-10 mass spectrometer. Constants used in model age calculations: X E = 0.585 x 10- 1 0yr - 1; Ag= 4.72 x 10- 1 0yr _ 1; 40K/K - 1.181 x IO - 4. the Stikine Arch into the Omineca Belt in the Cassiar area contains one of the three major molybdenum concentrations in the Canadian Cordillera. The general geology of the Cassiar and Atlin areas is described below. 4.4.2 Cassiar Area * The Cassiar Batholith (Figure 4-4) has a mean K-Ar age of 102 + 3 m.y. Late Cretaceous igneous activity along the western margin of the Cassiar Batholith is indicated by mean ages of 96 + 3 m.y. from the Seagull Batholith and 76.5 + 4 m.y. from the Glundebery Batholith, and by K-Ar ages of 78 + 4 m.y. from the Parallel Creek Batholith and 71 m.y. from a quartz monzonite north of Dease Lake. Early Tertiary igneous activity to the west of the Cassiar Batholith is indicated by concordant K-Ar ages of 48 + 4 m.y. on hornblende and 46+2 m.y. on biotite from a small quartz diorite pluton that intrudes the Christmas Creek Batholith. A young stock, that occurs within the Cassiar Batholith to the northwest of the area shown in Figure 4-4 has yielded biotite K-Ar ages of 58+3 m.y. and 53+3 m.y. The Blue Light property, located in this young quartz monzonite body, contains tungsten and beryllium minerals (Mulligan, 1969). A muscovite K-Ar age of 57 m.y. was obtained from granitized terrain exposed about 10 mi. northeast of Mt. Haskin in the Horse Ranch Range. Gabrielse (in Lowdon et al., 1963b) suggested that this age might date the emplacement of post-tectonic plutons and metamorphic rocks recrystallized to some extent at that time. Because ,the youngest rocks intruded by the Cassiar intrusions in the area shown in Figure 4-4, are of Devono-Mississippian age (Gabrielse, 1963), * See Appendix D (Table D-l) for review of ages cited time of intrusion cannot be dated accurately by stratigraphic methods. Samples PC9 to PC14 (Figure 4-4) were collected from: (1) a quartz monzonite porphyry stock that intruded Paleozoic sedimentary and volcanic rocks to the east of the Cassiar Batholith and (2) small granite porphyry stocks, s i l l s and dikes that intruded sedimentary and metasedimentary rocks of the Atan Group. Cassiar Molybdenum Property The Cassiar Molybdenum property (Figure 4-4) occurs within a young quartz monzonite that cuts the Cassiar Batholith along its eastern border (Campbell, 1968). Stockwork and disseminated molybdenite are related spatially and probably genetically to a late, fine-grained phase of the young quartz monzonite. Samples PC13 and PC14 were collected from the early, pre-mineral- ization phase of the quartz monzonite stock. Biotite concentrates from these samples contain less than 2% chlorite as alteration along cleavage planes. Quartz monzonite samples PC13 and PC14 have consistent biotite K-Ar ages of 71.7 + 2.6 m.y. and 68.3 + 2.7 m.y. Mt. Haskin Mo and Mt. Reed Mo-W Properties Granite porphyry intruded sedimentary and metasedimentary rocks of the Atan Group on both the Mt. Haskin Mo and Mt. Reed Mo-W properties (areas shown in detail on Figure 4-4). Stockwork and disseminated molybdenum and tungsten bearing minerals are found in both the granite porphyry and contact altered metasedimentary rocks. Mineralization is believed to be temporally related to the granite porphyry. Granite porphyry samples PC9 and PC10 are from a small stock on the Mt. Haskin property and granite porphyry samples PC11 and PC12 are from a texturally and chemically similar stock on the Mt. Reed property. Biotite contents of samples PC9-PC12 range from 1 to 4%. Chlorite content of the analyzed biotite concentrates is less than 5%. Granite porphyry samples PC9 to PC12 from Mt. Haskin Mo and Mt. Reed Mo-W properties have biotite K-Ar ages ranging from 48.7 to 50.5 m.y. and a mean K-Ar age of 49.8 +0.7 m.y. Reliable isochron ages could not be obtained from the granite porphyry (see section 2.4) because of the small differences in potassium content of the biotite concentrates PC9 to PC12. Discussion Ages obtained for quartz monzonite and granite porphyry in the Cassiar area suggest that molybdenum and associated tungsten mineralization occurred after the emplacement of the Cassiar Batholith (102 + 3. m.y.). The 71.7 + 2.6 m.y. and 68.3 +2.7 m.y. ages obtained for a young phase of the Cassiar intrusions place an upper limit on the age of mineralization on the Cassiar Molybdenum property. Because both mineralized and barren granite porphyry samples from the Mt. Reed and Mt. Haskin properties yield the same age within analytical limits, mineralization on these properties is considered to be an integral part of an early. Tertiary magmatic event. The Late Cretaceous and early Tertiary ages obtained for quartz monzonite porphyry and granite porphyry phases of the Cassiar intrusions are consistent with a trend from older, more basic, granitic phases to younger, more acid, porphyritic bodies. 58. Apatite fission-track ages obtained from the Cassiar area are in good agreement with K-Ar ages for oogenetic biotite. Figure 3-1 demonstrates the K-Ar ages and apatite fission-track ages for samples PC8, PC12, PC13 and PC14 are the same within analytical limits. Because apatite fission-track and biotite K-Ar ages are concordant, the apatite fission- track method is considered to be useful in age dating Late Cretaceous and Tertiary units in the Cassiar area. 4.4.3. Atlin Area No radiometric ages are available for intrusive rocks in the Atlin area. Ages ranging from 54 m.y. to 70 m.y. were reported from the Bennett area to the west and adjacent parts of the Alaska Panhandle (Cristie in Lowdon et al., 1963a), and an age of 69 m.y. was obtained from quartz monzonite in the Tulsequah area to the south. Souther (in Lowdon et al., 1963b) reported that discordant quartz monzonite stocks along the eastern contact of the Coast Crystalline Belt in western British Columbia and southeastern Yukon are part of the youngest phase of the Coast Intrusions. More recently, K-Ar whole-rock and biotite ages ranging from 46.9 to 52.8 m.y. were obtained from quartz monzonite of the East Marginal Pluton of the Coast Intrusions in the Juneau Ice Field area (Forbes and Engles, 1970). These data reinforce the early Tertiary K-Ar ages for granitic rocks along the eastern margin of the Coast Intrusions. Adanac Mo Property Figure 4-5 shows the location and general geology of the Adanac area. The Adanac Mo property is on upper Ruby Creek, and molybdenum with minor tungsten is found in granitic rocks that are part of the Mt. Leonard Boss mapped by Sutherland Brown (1969b). The Mt. Leonard Boss intrudes a sequence of rocks ranging in age from Permo-Pennsylvanian Cache Creek metavolcanic rocks to the Fourth of July Batholith which has been assigned a Jurassic (?) age (Aitken, 1959). Sutherland Brown (1969b) suggested that the mid- Cretaceous (?) Mt. Leonard Boss is in a l l probability connected to the main Suprise Lake Batholith and that a l l phases of the stock are as closely related in age as they are in chemistry. One sample (provided by W. Sirola) was available from the Mt. Leonard Boss. This sample contained about 1% biotite with 15% chlorite alteration. A biotite concentrate containing about 5% chlorite was obtained from the sample. Low potassium content of the biotite (5.16 + 0.04%) is caused by chlorite alteration. A 62.9 + 2.2 m.y. K-Ar age was obtained for the biotite concentrate. The 62.9 + 2.2 m.y. age for the alaskite phase of the Mt. Leonard Boss is consistent with the young age of discordant quartz monzonite stocks along the eastern contact of the Coast Crystalline Belt (Souther in Lowdon et a l . , 1963a; Forbes and Engles, 1970). 4.4.4 Conclusions Late Cretaceous and early Tertiary ages obtained for the Adanac Mo property, Cassiar Mo property, Mt. Haskin Mo property, and Mt. Reed Mo-W property, and early Tertiary ages reported for quartz monzonite and pegmatite associated with the Blue Light tungsten property (Wanless et a l . , 1970) indicate a Late Cretaceous to early Tertiary metallogenic epoch for molybdenum and tungsten in northern British Columbia. The existence of a 60. Late Cretaceous to early Tertiary metallogenic epoch for porphyry mineral deposits has previously been suggested for central British Columbia (Carter, 1970; 1972a) and for southeastern Alaska (Reed and Lanphere, 1969). 4.5 GRANISLE MINE, BABINE LAKE AREA, BRITISH COLUMBIA 4.5.1 Introduction Copper deposits of the Babine Lake area are related to small, high- level, subvolcanic porphyritic intrusions of early Tertiary age that intrude Mesozoic volcanic and sedimentary rocks of the Hazelton Group (see Carter, 1972b, Fig. 12, page 28; Carter, 1970). The intersection of northwesterly and northeasterly striking faults may have controlled emplacement of Tertiary intrusions. Porphyry copper deposits are associated with dykes and plugs of biotite-feldspar porphyry of quartz diorite composition. Biotite K-Ar ages obtained for 10 samples from porphyries have yielded a mean age of 51.2 + 2 m.y. (Carter 1972b). The Granisle Mine has been classified as an elaborate porphyry deposit (Sutherland Brown, 1969a) because of the several phases and pulses of biotite-feldspar porphyry that are spatially and temporally associated with copper mineralization. An oval zone of potassic alteration is roughly coincident with the ore zone and a number of north 50° east striking bornite- chalcopyrite-quartz-biotite-apatite veins occur in the potassic zone (Carter, 1972b). 4.5.2. Potassium-Argon Dating A mean biotite potassium-argon age of 51.2 + 2 m.y. was determined for 61. J—I—L. 4 0 0 feet m BIO.-FELD. PORPHYRY / / contact; defined, assumed undivided / / A ^ l INTRUSIVE BRECCIA P7~] BIO-FELD. PORPHYRY gray massive m BIO.-FELD. PORPHYRY L_—I fractured,mineralized |~2~| QUARTZ DIORITE | T | METAMORPHIC ROCKS n/v fault V t edge of open pit • N C 6 9 - 8 Sample Location 50.2 ±2.1 K-Ar Age m.y. FT30±4 Fission-Track Age m.y. Figure 4-6. Geochronology and general geology of the Granisle Mine pit (geology from Carter, 1972b). three samples of biotite-feldspar porphyry and one sample (NC-69-8) of a quartz-chalcopyrite-bornite-apatite vein from the Granisle Mine (Carter, 1972b). Biotite from sample NC-69-8 has a K-Ar age of 50.2 + 2.1 m.y. (N.C. Carter personal communication, 1972). 4.5.3 Fission-Track Dating Part of sample NC-69-8 was obtained from N.C. Carter to obtain apatite for a fission-track age determination. Apatite grain mounts used to determine the fission-track age revealed two generations of apatite; 1) minor very clear and relatively unaltered apatite, (selectively counted), and 2) highly altered grains containing fluid, chalcopyrite and altered silicate inclusions. Only a few useable grains could be obtained by scanning the grain mounts at low power. A fission-track age of 29.6 + 4.1 m.y. obtained for this sample is discordant with the 51.2 + 2 m.y. biotite K-Ar age, but the apatite fission-track age does reflect the young Tertiary age. 4.5.4 Discussion The 50.2 + 2.1 m.y. biotite K-Ar age of sample NC-69-8 (Figure 4-6) is supported by mean K-Ar ages of 51.2+2 m.y. for four samples from the Granisle Mine and 51.2 + 2 m.y. for ten K-Ar age for porphyries in the Babine Lake area (Carter, 1972b). The 30+4 m.y. apatite fission-track age is young and could be a reset age, but alteration of apatite grains made track distinction difficult and the error in this determination may be larger than the counting error. 63. -4.6 COPPER MOUNTAIN AREA, BRITISH COLUMBIA 4.6.1 Introduction The Copper Mountain and Ingerbelle mineral deposits, which are located on opposite sides of the Similkameen River, about 10 miles south of Princeton, British Columbia, occur in syenitic stocks and volcanic rocks of the Upper Triassic and Lower Jurassic Nicola Group. These 'syenitic' deposits have been classified on the basis of structure as complex porphyry deposits (Sutherland Brown, 1969a) and on the basis of the high- level of emplacement of an associated and genetically related variable shaped pluton as volcanic porphyry deposits (Sutherland Brown, 1972). Copper deposits of the 'syenitic' volcanic porphyry class appear to be restricted to the intermontane tectonic belt of the Canadian Cordillera. Comprehensive geologic reports on the geology of the Copper Mountain area by Dolmage (1934), Rice (1947), Fahrni (1951, 1962, 1966), Montgomery (1967) and Preto (1972a and b) and K-Ar age dating studies by Sinclair and White (1967) and Preto et al. (1971) support the geologic interpretation presented in Figure 4-7. Table 4-4 is a listing of the apatite fission-track ages obtained for samples previously dated by the biotite K-Ar method. 4.6.2 General Geology Figure 4-7 shows the general geology of the Copper Mountain area and the location of the Ingerbelle and Copper Mountain mineral deposits. The oldest rocks in the area are part of the Upper Triassic Wolf Creek Formation of the Nicola Group (Rice, 1947). In the Copper Mountain area the Wolf Creek Formation is predominately andesite, tuff and volcanic clastic sediments 64. FIGURE2-7 GENERAL GEOLOGY OF THE COPPER MOUNTAIN AREA BRITISH COLUMBIA PRINCETON GROUP VERDE CREEK QTZ. MONZ. LOST HORSE INTRUSION PERTHOSITE PEGMATITE MONZONITE NICOLA GROUP VP-69AK-I ' 194 *a SAMPLE LOCATION AND AGE IN M.Y( Preto et al..1971) CM-I2-65 4 I82«8 SAMPLE LOCATION AND AGE IN M.Y. (Sinclair and White, I968) FTt01*12 FISSION-TRACK AGE M.Y. (this report) 65. that generally display very mild metamorphism and deformation, except in the immediate vicinity of intrusive bodies (Preto, 1972b). A number of quartz-poor plutons, collectively known as the Copper Mountain intrusions (Montgomery, 1967) are spatially and genetically related to the mineral deposits. The largest, the Copper Mountain stock, is a concentrically differentiated intrusion, elliptical in plan and about 6.5 square miles in area. It ranges in composition from diorite at its outer edge through monzonite to syenite and perthosite pegmatite at the core (Montgomery, 1967). Preto et al. (1971) divide the Copper Mountain intrusions into the zoned Copper Mountain stock, the satellite Smelter Lakes and Voigt stocks, and the Lost Horse intrusions (Figure 4-7). Northeast of Copper Mountain, diorite of the Voigt stock and volcanic rocks of the Nicola Group are cut by a body of younger quartz monzonite that was named the Verde Creek granite by Dolmage (1934) and believed by Rice (1947) to be correlative with the Otter intrusions of.Upper Cretaceous or younger age. K-Ar age dating by Preto et al. (1971) supports the Cretaceous age assigned to the Verde Creek body. In the vicinity of the Copper Mountain and Ingerbelle mineral deposits alkali metasomatism has produced a distinctive mineral assemblage characteristic of copper deposits of the Nicola Belt. Alteration is most intense in the Lost Horse intrusions and bears a close spatial relationship to faults and fractures (Preto, 1972a). Successive stages of alteration recognized by Preto (1972a) are: 1) Development of biotite that has been partly destroyed by later alteration. 66. 2) Development of albitlc plagioclase and epidote that was accompanied by removal of biotite and of disseminated magnetite, and bleaching of pyroxene. Secondary sphene, apatite and pyroxene are locally developed. 3) Development of pink potash and plagioclase feldspar along fractures that was accompanied by sulfide-bearing pegmatite veins characterized by selvages of coarse biotite along the edges and bornite, chalcopyrite, potash feldspar, and calcite at the center. 4) Development of late scapolite veins that are most prominent in the Ingerbelle area. Because biotite and apatite used for some of the age dating was developed during the alteration stages, the interpretation of radiometric ages would be tenuous without the detailed description of alteration provided by Preto (1972a and b). 4.6.3 Fission-Track Dating Ten samples (VP69 (KA1 to KA10) ) from the Copper Mountain area that had previously been dated by the biotite K-Ar method (Preto et al. 1971) were obtained from the British Columbia Department of Mines. Apatite concentrates were obtained from eight of the ten samples, but intense alteration of apatite grains eliminated the possibility of using four of the eight apatite concentrates for fission-track dating. Sample KA4 from the Verde Creek quartz monzonite in the Copper Mountain area gave discordant 101 + 4 m.y. biotite K-Ar and 129 + 23 m.y. apatite fission-track apparent 67 ages. The minor discordance is attributed to the altered nature of the apatite grains. Samples KA1, KA9 and KA10 from the Copper Mountain intrusions yield a mean apatite fission-track age of 111 + 7 m.y. and a mean biotite K-Ar age of 195 + 2 m.y. Biotite K-Ar ages for samples KA1, KA9 and KA10 are in close agreement with mean biotite K-Ar age of 193 + 8 m.y. reported by Preto et al. (1971) for eleven samples from Copper Mountain. The Copper Mountain intrusions are believed to be co-magmatic with the Upper Triassic to Lower Jurassic Nicola volcanics, and since extensive K-Ar dating supports an Upper Triassic or earliest Lower Jurassic age for the Copper Mountain intrusions (Preto et al. 1971; Sinclair and White 1968), the Cretaceous apatite fission-track ages for the Copper Mountain intrusions probably represent reset ages or thermally lowered ages. A widespread Cretaceous thermal event in the Copper Mountain, area is suggested by: 1) the average age of 99.5+4 m.y. determined by Preto et al. (1971) for the Verde Creek quartz monzonite. 2) a 104 m.y. age suggested for the major phases of the Eagle granodiorite lying to the west of Copper Mountain (Roddick and Farrar, 1972), and 3) an Early to Middle Cretaceous thermal event dated about 100 m.y. in northcentral Washington (Hibbard, 1971). . The consistent low ages obtained for apatite from the Copper Mountain intrusions suggest a thermal event that was strong enough to reset the apatite fission-track clocks but not the biotite K-Ar clocks. A temperature between 68. about 75°C (Naeser and Faul, 1969; Wagner 1968) and 150°C (Damon, 1968) associated with a Cretaceous thermal event would account for the difference in apparent fission-track and biotite K-Ar ages. 4.6.4 Summary A 129 + 23 m.y. apatite fission-track age for the Verde Creek quartz monzonite supports the Cretaceous age for this unit. A mean apatite fission-track age of 111 + 7 m.y. for samples KA1, KA9 and KA10 from the Copper Mountain intrusions reflect a heating event that is related to Early to Middle Cretaceous granitic intrusion. Table 4-4. Fission-track and K-Ar ages obtained for granitic rocks in the Copper Mountain area, British Columbia. (K-Ar ages are from Preto et al., 1971) Sample Number Unit Mineral dated Fission- track age (m.y.)* K-Ar age (m.y.) KA1 Lost Horse intrusion apatite biotite 117 + 12 194 + 8 KA4 Verde Creek qtz. monz. apatite biotite 129 + 23 101 + 4 KA9 Lost Horse intrusion (dike) apatite biotite 101 + 12 197 + 8 KA10 Lost Horse intrusion apatite apatite biotite 101 + 13 127 + 18 195 + 8 * Fission-track analyses by P.A. Christopher, Constants used in model age calculations: /|F for U 2 3 8 = 6.85 x 10~ 1 7yr _ 1; / i D for U 2 3 8 = 1.54 x lO-^yr" 1; o-for U 2 3 5 = 582 x 10 _ 2 4cm 2. 69. 5. REVIEW OF METALLOGENY AND METALLOGENIC EPOCHS FOR PORPHYRY MINERAL DEPOSITS OF THE CANADIAN CORDILLERA 5.1 Introduction In this chapter the K-Ar ages obtained for this study and published ages are used to place porphyry mineral deposits of the Canadian Cordillera in a tectonic-stratigraphic-lithologic framework; the concept of metallogenic epochs is evaluated for porphyry and related mineral deposits; and the concept of metallogenic epochs for porphyry deposits is examined in terms of global tectonics. 5.2 Metallogeny and Metallogenic Epochs Metallogeny is concerned with the genesis of mineral deposits and with their distribution in space and time. Metallogenic provinces and metallogenic epochs reflect an uneven distribution of various types of mineral deposits in space and time. The first statement of the concept of metallogenic provinces and metallogenic epochs was presented by De Launay (1913). As the result of his regional studies of mineral deposits in France, De Launay suggested that each metallogenic province belongs to a definite regional type depending on the tectonics and that the nature of each province may be forecast, to a certain extent, by the knowledge of the latter. This is a very comprehensive and concise statement of the problem encountered by the geologist attempting to outline a genetic model for a metallogenic province. Lindgren (1933) discussed the factor of time as it concerns the mineral deposits of a metallogenic province, and Petrascheck (1965) credits Lindgren 70. with the introduction of the concept of a metallogenic epoch. Lindgren's examples suggest that metallogenic epochs coincide with the major orogenic epochs in the earth's history. Turneaure (1955) used the term metallogenic epoch to designate periods during which mineralization was most pronounced. Petroscheck (1965) restricted metallogenic epochs to tectonic metallogenic intervals within a major tectonic unit (e.g. orogenic belt, shield area, or craton). If the concept of a metallogenic epoch is to be of use in classification and exploration of mineral prospects, a metallogenic epoch must be applied to a stage or interval within a tectonic cycle. The idea of relating mineral deposits to stages of development of orogenic belts was developed in the U.S.S.R. by Bilibin (1955). Bilibin's i n i t i a l work was concerned with endogenous (hypogene) mineral deposits. Semenov and Serpuklov (1957) added a study of exogenous (sedimentary and supergene) deposits to the regional metallogenic analysis. In Canada, the application of a tectonic approach to the study and classification of ore deposits is more recent. C.J. Sullivan's (1948) paper entitled "Ore and Granitization" was an early step toward a tectonic cycle approach. Sullivan emphasized the composition of the stratigraphic column through which intrusions make their way upward. Sullivan's (1957) classification of metalliferous provinces and deposits stresses field association and a "source bed" approach is used in his classification. McCartney and Potter (1962) and McCartney (1965) reviewed metallogeny of the Canadian Appalachians using Russian metallogenic concepts. In 71. these reviews the emphasis is on type of magmatic activity and related mineral deposits typical of successive stages of folded belt development. Sutherland Brown et al. (1971) related the general distribution of mineral deposits in the Canadian Cordillera to tectonic evolution. Porphyry mineral deposits of the Canadian Cordillera f i t into a generalized tectonic scheme (Figures 5-la, b and c) that shows the distribution of porphyry mineral deposits in time and space within the Canadian Cordillera. A.Y. Bilibin (1955) and A.I. Semenov and V.I. Serpuklov (1957) applied a similar approach to mineral deposits in folded belts of the U.S.S.R., and W.D. McCartney and R.R. Potter (1962) applied the tectonic concepts developed in the U.S.S.R. to mineral deposits of the Canadian Appalachians. The classic geosyncline model (Stille, 1936 and Kay, 1951) used by these workers has been replaced by a plate-tectonic approach. The general idea of cyclic development of a mobile belt holds, but cyclic development should only apply to well-defined segments of recrystallized sial (Monger et al., 1972), segments with different metallogenic and tectonic development may now be contiguous belts. An hypothesis that can be applied to the metallogeny or tectonics of one part of a tectonic belt may not be valid once a major fault is crossed or an apparent unconformity is encountered in the stratigraphic section. 5.3 Tectonic Setting Sutherland Brown et al. (1971), Souther (1970), Wheeler (1970), Hodder and Hollister (1972) and Monger et al. (1972) have described the tectonics and (or) mineral deposits of the Canadian Cordillera in terms of five distinct geological and physiographical belts. These are (from east 7 2 . F i g u r e 5 - l a . T e c t o n i c s e t t i n g o f p o r p h y r y m i n e r a l d e p o s i t s i n t h e C a n a d i a n C o r d i l l e r a ( 4 9 - 5 2 ° N ) . DIORITE - SYENITE CLANS QUARTZ DIORITE-GRANITE CLANS GABBRO AND ULTRAMAFE ROCKS BASIC VOLCANICS ISLAND ARC VOICANISM mainly andesite CONTINENTAL VOLCANISM mainly dacite & rhyofite PLATEAU4VALLEY BASALT NO LINKAGES KNOWN BETWEEN TECTONIC BELTS (alter MONGER et a.,1972) ANGULAR UNCONFORMITY, NONCONFORMA8LE. or UNCONFORMABLE NOT IN CONTACT, or FAULT CONTACT j y UPLIFT \ \ SUBSIDENCE — CONFORMABLE ISLAND COPPER Cu;Mo HEP Cu;Uo CATFACE Cu;Mo MT. WASHINGTON Cu;Mo TOFINO Mo CORRIGAN CK. Cu;Mo GREENDROP LK_ Cu;Mo GUICHON BATHOLITH Cu.Mo COPPER MOUNTAIN Cu IRON MASK Cu MAGGIE Cu: Mo McBRIDE CK. Cu;Mo LOSTCK. Mo RED MOUNTAIN Mo Brenda Mo.Cu 570 Figure 5-lb. Tectonic setting of porphyry mineral deposits in the Canadian Cordillera (52-56°N). -65 Canadian Cordillera 5 2 - 5 6 ° N m.y. 37- 38 53- 54 - 190- 195 - 205 - 215 •225 - 280 325 345 395 " 500 5 70 INSULAR I f — ! MAUDE • • • KARMUTSEN* COAST 40-50 64-79 J H A Z E L J O N ^ INTERMONTANE A A 60-69 GG HyOx v 8 0 98-105 BM 138-143 ^8P E Lr A HOGEM OMINECA EASTERN MARGINAL PROPERTIES Lr LORRAINE Cu E EN0AKO Ma BM BOSS MOUNTAIN Mo Hy HUCKLEBERRY Cu:Mo Ox OX LK. Cu;Mo GG GLACIER GULCH MO;W BCM BRITISH COLUMBIA MOLYBDENUM Ma Nm NEWMAN Cu Gt GRANISLE Cu Bg BERG Cu;Mo SG SAM GOOSLY (Cu.Ag massive sulfide) Figure 5-lc. Tectonic setting of porphyry mineral deposits in the Canadian Cordillera (56-64°N). PROPERTIES BC BURWASH Ck CuMo Ad Adanac Mo:W Sk STIKINE COPPER Cu LC LIARD COPPER Cu Cs CASINO Cu;Mo;W MR MT. REED Mo;W MH MT. HASKIN Mo Ct CANTUNG (skarn) MT MACTUNG W C u (W skam) <-570 75. to west): (1) Eastern Marginal Belt, (2) Omineca Belt, (3) Intermontane Belt, (4) Coast Crystalline Belt, and (5) Insular Belt. The terminology and belt configuration (Figure 5-2) used in this discussion follows Sutherland Brown et al. (1971). Because mineral deposits appear to be characteristic of individual belts, the configuration of belts shown in Figure 5-2 is applicable to a discussion of the distribution of endogenic mineral deposits in space and time. Monger et al. (1972) suggested that from the record in the Canadian Cordillera the present configuration of five geologic belts was only obtained by late Mesozoic time. Clastic wedges shed from the Omineca Belt during the Caribooan Orogeny (Antler Orogeny in the western United States) indicate that the Omineca Belt existed as a positive feature by late Devonian time. All the present tectonic elements were in existence by late Triassic time and common stratigraphic units linked the northern parts of the Omineca, Intermontane and Coast Crystalline belts by Upper Triassic time (Monger et al., 1972). In late Cretaceous and early Tertiary time the Canadian Cordillera represented a mobile belt similar to the present-day Andes (Monger et al., 1972) with great volumes of subaerial volcanic rocks. These volcanics represent the cover into which many small, calc-alkaline, epizonal, 76. / NORTHERN 14-/-, ' - . - — . . . Y U K O N | \ \ i • / / § ' MTS \ ) i — h SIMPLIFIED TECTONIC MAP OF THE CANADIAN CORDILLERA LATE TERTIARY PLATEAU BASALTS JURA-CRETACEOUS CLASTIC ROCKS OF BOWSER BASIN s—I" 11 GRANITIC ROCKS OF COAST CRYSTALLINE BELT TRIASSIC MARINE BASALT OF INSULAR BELT LOWER PALEOZOIC SEDIMENTARY ROCKS OF OMINECA 8 EASTERN MARGINAL BELT HELIKIAN a HAORYNI AN M ETAS EDI MENTARY ROCKS OF OMINECA BELT BOUNDARIES OF TECTONIC BELTS BOUNDARIES OF MINERALIZED REGIONS PROJECTIONS OF MAJOR CRATONIC FRACTURES Miles 100 100 N, r"' \ 1 Figure 5-2. Tectonic Map (from Sutherland Brown et a l . , 1971). 77. subvolcanic stocks and some alkaline epizonal stocks were emplaced. Following the mid-Eocene volcanic events, most of the four eastern belts were inverted from a mobile belt under compressional stress to a stable continent edge. Souther (1970) suggested that onset of relaxation by late Eocene time was accompanied by a complete change in the structural style, volcanism and plutonism indicated by: 1) structural trend switching from predominately west-northwesterly to northerly, 2) acid volcanism replacing andesitic island-arc volcanism, 3) block faulting replacing elongate grabens and, 4) high-level intrusions of granitic plutons and dikes. Atwater (1970) suggested that intrusion and eruption of calc-alkaline magmas of predominately intermediate and s i l i c i c compositions should have existed above formerly active Benioff zones and should have ceased when subduction ceased. The 25-30 m.y. paucity of volcanism between Late Eocene and Miocene time suggests a major change in the plate interactions. 5.4 Age Dating and Metallogenic Epochs The importance of isotopic age dating in establishing metallogenic epochs and concepts of metallogeny has been stressed by White (1966), White et al. (1968), and Livingston et al. (1968). Several authors (White et al., 1968; Livingston et al., 1968; Moore et al., 1968; Fyles et al., 1973) have demonstrated the close association of intrusion and mineral deposition in Cordilleran porphyry mineral deposits by showing that the ages of the mineral deposit and the host or associated intrusion are within the limits of detection of the K-Ar method. The sub-volcanic setting for porphyry mineral 78. deposits has been suggested by White (1966), Carter (1970 and 1972b), Sutherland Brown et al. (1971), Northcote and Muller (1972) and others. Therefore, by obtaining the age of the porphyritic mineral deposit, the deposit can be placed in the proper lithologic-tectonic-stratigraphic environment. The K-Ar dating method has been extensively used for determining the apparent age of intrusive rock in the Canadian Cordillera. Since the early 1960s several hundred K-Ar determinations have been published. Published age determinations that form a basis for this review are listed in Appendix D. Age patterns for intrusive rocks are examined by plotting histograms (Figures 5-3 and 5-4) of K-Ar ages published after 1965 and ages obtained by Mathews (1964) that are in close agreement with fossil evidence. Many ages reported before 1965 have been found to be unreliable and therefore, ages reported before 1965 are not used in histogram plots. Variation in apparent age of plutonic rocks is examined by plotting histograms for segments parallel to the north-westerly trend of the Canadian Cordillera (tectonic belts) and normal to the trend of the Canadian Cordillera (arbitrary segmenting by latitude). Figure 5-3 shows the variation of K-Ar ages for tectonic belts and Figure 5-4 shows variation of K-Ar ages for southern, central and northern segments of the Canadian Cordillera. The total plot of K-Ar ages has concentrations at about 26 m.y., 50 m.y., 78 m.y., 98 m.y., 140 m.y. and 198 m.y. but only the 50 m.y. peak consistently appears in the various tectonic segments. Age plots appear to reflect both a geographic bias and a mineral deposit bias. The Late Triassic (Guichon Batholith and Copper Mountain intrusions), Late Jurassic 25 20 15 10 5 INTERMONTANE BELT JQ=L f~l r-i 10 n n r - i r - ; '-J^L 1 r ~ i ~ - i INSULAR BELT 49-5l"N r -n n n 51-56°N n r I 56 -64° N 20 15 10 l—i • I I I OMINECA BELT j—I r - i r - i r - i I I •  U J I n r - i — i i i i ; i I I m n 1 1 - — n —1 r - 1 i r - i . r - - - 5 2 - 5 6 ° N r — i pur 10 , — -'"1 1 1 5 I ! r - H COAST CRYSTALLINE BELT 49-52°N i 1 r—I r - i — n 5 2 - 5 6 ° N 1 1 r—1 r ^ n 56 -64°N 20 40 60 80 100 120 age in m.y. 140 160 180 200 220 Figure 5-3. K-Ar age determinations for igneous rocks in the Canadian Cordillera. Dashed line represents total for tectonic belt. 80. Figure 5-4. K-Ar age determinations for igneous rocks in segments of the Canadian Cordillera between 49-52°N, 52-56°N and 56-64°N. 81. (Topley Intrusions) and in part the Eocene peaks reflect vigorous collecting of samples that are from porphyry mineral, deposits and the Isotopic Age Map of Canada (Wanless, 1969) shows concentrations of samples in south-central British Columbia, the Skeena Arch area and the Cassiar Mountains. Gilluly (1973) suggested that, "taking the Cordillera as a whole, magmatism was roughly constant except for the apparent low about 115 to 125 m.y. ago". This low in number of K-Ar ages for igneous rocks is especially apparent in the Canadian Cordillera (Figure 5-4) and may represent a time of major change in either direction or rate of plate motion. Evolution of the continental margin from an Indonesian type island arc to an Andean type margin (Wheeler et al., 1972) occurred during early Cretaceous time and may be related to rebound of light sialic material consumed during early Mesozoic subduction. Gilluly's (1973) suggestion that episodic magmatism is a local phenomenon and that magmatism was roughly constant in the Cordillera, appears to hold for early Mesozoic time in the Canadian Cordillera but his suggestion is not supported by the low in early Cretaceous K-Ar ages or by the widespread pulse of Eocene igneous activity. The apparent early Cretaceous change in the pattern of K-Ar ages for igneous rocks may represent either a reduction in the effect of burial on the apparent K-Ar age of igneous rock emplacement or a more uniform history for the various tectonic belts that were completely linked by Cretaceous time (Monger et al., 1972). Metallogenic epochs for porphyry mineral deposits are also examined by plotting a histogram (Figure 5-5). For porphyry deposits, the number of significant mineral deposits is plotted against the K-Ar age. Porphyry (^^approximate number of K-Ar ages •20 15 10 •Phallic Class- Plutonic & Volcanic Classes © 7 RS T B9 cT NIH MR RM s > i © © © Ad Ca M OO [ic] 20 40 60 80 100 age in m.y. 120 140 160 180 200 Figure 5-5. K-Ar age of porphyry mineral deposits in the Canadian Cordillera. GD - Greendrop Lk.; BC - Burwash Ck. ; CC - Corrigan Ck.; MW - Mt. Washington; S - Serb; RB - Red Bird; T - Tofino Mo.; Bg - Berg; Cf - Catface; MH - Mt. Haskin;,MR - Mt. Reed; Ad - Adanac; M - Maggie; Cs - Casino; GG - Glacier Gulch; LCK - Lost Ck.; BM - Boss Mtn.; E - Endako; B - Brenda; IC - Island Copper; Lr - Lorraine; LC - Liard Copper; CM - Copper Mountain. 83. Figure 5-6. Triassic lavas and the Triassic and Jurassic porphyry deposits (from Sutherland Brown et al., 1971). IC - Island Copper; CM - Copper Mountain and Ingerbell; Ba - Brenda; HV - Highland Valley; CB - Cariboo Bell; E - Endako; Lr - Lorraine; Sk - Stikine Copper; GL - Gnat Lake. 84. Figure 5-7. Early Tertiary volcanic rocks and porphyry deposits (modified from Sutherland Brown et al. 1971). Cs - Casino; BC - Burwash Creek; Ad - Adanac; BEM - British Columbia Molybdenum; Gi - Granisle; GG - Glacier Gulch; Bg - Berg; Cf - Catface; GD - Greendrop Lake. 85. mineral deposits f i t into several age groupings that show consistent metal content and geologic setting. K-Ar dating of porphyry mineral deposits indicates metallogenic epochs at about 195 m.y. and 150 + 10 m.y. for deposits that f i t in Sutherland Brown's plutonic and volcanic classes; and at about 100 m.y., 80 m.y., 65 m.y., 50 m.y., 35-40 m.y. and 26 m.y. for deposits that f i t into Sutherland Brown's phallic class. Porphyry mineral deposits are distributed throughout the four western tectonic belts. Porphyry copper deposits are associated with Triassic to Miocene intrusions and volcanic rocks (Figures 5-6 and 5-7) of the Insular and Intermontane belts and porphyry molybdenum and tungsten deposits are associated with Jurassic to Eocene intrusions into metasedimentary and sedimentary rocks of the Coast Crystalline Belt, Intermontane Belt and Omineca Belt. The 50 m.y. metallogenic epoch is the only mineralizing event that has been documented and is significant in the four western tectonic belts. Porphyry deposits of the plutonic and volcanic classes have received the most attention from exploration and research projects because they are the major producers and contain the major proven reserves of copper and molybdenum in the Canadian Cordillera. 5.5. PLATE TECTONICS AND METALLOGENY OF PORPHYRY MINERAL DEPOSITS The relationship of porphyry mineral deposits to paleo-Benioff zones has been discussed on a global basis by Sillitoe (1972 a and b), Guild (1971 and 1972), and Mitchell and Garson (1972). These authors generally conclude that porphyry copper deposits are derived from materials regenerated in subduction zones and emplaced at high levels in the crust with stocks of 86. calc-alkaline affinity. An eastern migration of intrusive centers has been suggested for western South America (Farrar et al., 1970; Ruiz et al., 1965) and Sillitoe (1972) suggests that the age of porphyry deposits show a similar age distribution in the Cordillera of the United States and Mexico. Age patterns for porphyry mineral deposits in the Canadian Cordillera do not show a simple trend. Deposits range in age from Jurassic (Island Copper) to Miocene (Burwash Creek) in the Insular belt and from Triassic (Copper Mountain, Bethlehem, Lornex, Stikine Copper etc.) to Eocene (B.C. Molybdenum, Granisle, Bell etc.) in the Intermontane Belt. The age pattern of mineral deposits does support a basic difference between the pattern of development of porphyry deposits in the Intermontane and Insular belts. Triassic 'syenitic' volcanic porphyry deposits are restricted to the Intermontane belt and porphyry deposits of the volcanic class are associated with a middle Jurassic island arc assemblage (Bonanza Group)on Vancouver Island. Post-Eocene porphyry deposits are restricted to the Insular tectonic belt and Cascade Mountains and in particular to areas that appear to be affected by post-Eocene subduction. Atwater (1970) and Grow and Atwater (1970) suggest post-Eocene underthrusting of the Farallon Plate and Kula Plate below Vancouver Island and the Aleutian Arc respectively. The timing and direction of underthrusting of these plates is supported by the young age of the Mt. Washington and Corrigan Creek porphyry deposits on Vancouver Island (Carson, 1969), the Greendrop Lake property in the Cascades, and the Burwash Creek porphyry deposit southwest of the Shakwak Trench in the Yukon Territory. Widespread Eocene igneous 87. activity in the Canadian Cordillera suggests that subduction was occuring along the western margin of the continent until about 45 m.y. Post- Eocene transform motion from north of Vancouver Island to the Aleutian Trench would explain the distribution of igneous activity and the presence of younger porphyry mineral deposits on Vancouver Island, in the Cascade Mountains and in the St. Elias Fold Belt. 88. 6. CONCLUSIONS The following conclusions are based on fission-track and K-Ar dating of intrusive rocks from the Syenite Range and Burwash Landing area in the Yukon Territory and from the Cassiar area, Adanac property, Granisle Mine and Copper Mountain area in British Columbia; and on a review of published K-Ar ages for igneous rocks in the Canadian Cordillera. 1. A 26+0.3 m.y. mean K-Ar age was determined for four biotite concentrates from quartz latite porphyry near Burwash Creek, Yukon Territory. This apparent age for mineralized porphyry represents the youngest documented porphyry prospect in the Canadian Cordillera. 2. The 115 + 4 m.y. and 117 + 4 m.y. hornblende K-Ar ages determined for Kluane Range intrusions on the Cork (Burwash Creek) property agree with the Cretaceous age assigned to this unit by Muller (1967) . 3. The 51.9 + 2.0 m.y. and 54.5 + 2.0 m.y. biotite K-Ar ages determined for the Ruby Range batholith east of Burwash Landing agree with a previous 58 m.y. K-Ar age (Muller in Lowdon, 1960) for a marginal phase of the batholith. Muller (in Lowdon, I960; p. 9) described the 58 m.y. age as unexpected, but concordant biotite K-Ar and apatite fission-track ages of 54.5+2.0 m.y. and 48.9 +6.6 m.y. respectively for granodiorite sample PC8 provides convincing support for the early Tertiary apparent age for at least part of the Ruby Range batholith. Granite porphyry on the Mt. Haskin Mo and Mt. Reed Mo-W properties east of Cassiar, British Columbia has four biotite K-Ar ages ranging from 48.7 to 50.5 m.y. and a mean biotite K-Ar age of 49.8+0.7 m.y. Apatite fission-track ages of 48+6 m.y. and 60 + 8 m.y. for granite porphyry sample PC9 from the Mt. Haskin property and an apatite fission-track age of 54+7 m.y. for granite porphyry sample PC12 from the Mt. Reed property provide an internal check on the K-Ar age of these bodies. Mineralized and barren quartz latite porphyry near Burwash Creek and mineralized and barren granite porphyry from the Mt. Reed and Mt. Haskin properties yield ages that are identical within the limits of precision of the K-Ar method. This agrees with the findings of White et. al. (1968) that for many British Columbia porphyry deposits, mineralization is an integral feature of a magmatic event. On radiometric evidence these porphyry deposits f i t into the paramagmatic class of mineral deposits suggested by White. Biotite K-Ar ages of 71.7 + 2.6 m.y. and 68.3 + 2.7 m.y. obtained from a young phase of the Cassiar intrusions, place an upper limit on the age of the molybdenum mineralization on the Cassiar Molybdenum property. 90. 7. A 62.0 + 2.2 m.y. age, determined for a biotite concentrate from the coarse alaskite phase of the Mt. Leonard Boss, dates the molybdenum mineralization on the Adanac property. 8. Late Cretaceous and Early Tertiary ages obtained for the Adanac Mo property, Cassiar Molybdenum property, Mt. Haskin Mo property, and Mt. Reed Mo-W property and Early Tertiary ages reported for quartz monzonite and pegmatite associated with the Blue Light tungsten property (Wanless et al., 1970) indicate that the Early Tertiary metallogenic epoch, documented in central British Columbia and southeastern Alaska, can be extended through northern British Columbia. 9. Apatite fission-track ages from the Burwash Landing area, Cassiar area and Syenite Range are consistent and in general concordant with K-Ar ages determined on co-genetic biotite. These results suggest that the apatite fission-track method is a suitable method for dating late Mesozoic and Cenozoic igneous and metamorphic events in the Burwash Landing area, Cassiar area and Syenite Range. 10. One sample from a mineralized potassic-zone vein at the Granisle Mine has respectively 30+4 m.y. and 50.-2 + 2.1 m.y. apatite fission-track and biotite K-Ar ages. Discordant results is attributed to the altered nature of the apatite. 91. 11. Apatite fission-track ages from the Copper Mountain intrusions are consistently younger than K-Ar ages on co-genetic biotite. The fission-track ages are interpreted to reflect a heating event that is related to Early to Middle Cretaceous granitic intrusions. Because biotite K-Ar ages are affected only by contact events, and apatite fission-track ages appear to be regionally reset, temperatures below approximately 150°C are suggested for a thermal event of Cretaceous age. 12. Without additional geologic and geochronologic evidence, apatite fission-track ages from the Copper Mountain area and the Granisle Mine give misleading results with resulting misinterpretation of the thermal history. Therefore, in cases where alteration or thermal events are involved, apatite fission-track ages should be checked by using another more refractory mineral for fission-track dating or another radiometric clock. 13. Porphyry mineral deposits in the Canadian Cordillera f i t into several classes that show consistent metal content, geologic setting, and age. K-Ar apparent ages support metallogenic epochs for porphyry mineral deposits at approximately 190 m.y. and 150 + 10 m.y. for deposits that f i t into Sutherland Brown's plutonic and volcanic classes; and at approximately 100 m.y., 80 m.y., 65 m.y., 50 m.y., 35-40 m.y. and 26 m.y. for deposits that f i t into Sutherland Brown's phallic class. The age and distribution of the various classes of porphyry mineral deposits in the Canadian Cordillera are compatible with Monger et al. (1972) plate- tectonic model for the evolution of the Canadian Cordillera, but do not suggest a simple pattern of eastern migration of intrusive centers that has been suggested for western South America (Farrar et al., 1970 Ruiz et al., 1965) and for porphyry mineral deposits of the Cordillera of the United States and Mexico (Sillitoe 1972b) . 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APPENDIX A - DESCRIPTION OF SAMPLES USED FOR K-AR AND FISSION TRACK AGE DETERMINATIONS Burwash Creek, Yukon Territory (Fig. 4-2 & 4-3) PCI Quartz Latite Porphyry Sample is from recent road cut in barren, quartz-feldspar-biotite porphyry located three miles each of the Cork property. The rock contains 40% phenocrysts that are 65% plagioclase feldspar (zoned An3Q- An3g), 20% quartz, 6% biotite, 3% amphibole and 5% carbonate in a microgranular matrix of plagioclase, quartz and k-feldspar. Accessories are apatite, zircon and limonite after magnetite. Alteration Biotite is generally fresh but some grains show weak chlorite alteration along edges and limonite replacing magnetite inclusions. Amphibole is pseudomorphicly replaced by tremolite and iron oxide. Carbonate replaces cores of plagioclase phenocrysts and occurs along microfractures. PC2 Quartz Late Porphyry Sample is from recent cut about 500' east of PCI. The sample is similar in texture and mineralogy to PCI, but altered plagioclase phenocrysts have chlorite cores rimmed by carbonate and amphibole is replaced by carbonate, tremolite and iron oxides. PC3 Quartz Latite Porphyry Sample is from a recent cut near the West Fork of Johnson's Creek in the mineralized zone on the Cork property. Hand specimen contains molybdenite, pyrite and chalcopyrite in quartz veinlets and along "dry" fractures. The rock contains 20% phenocrysts that are 85% plagioclase 105. (about Ari25)» quartz "eyes", 3% biotite, and 1% amphibole in a microgranular matrix of plagioclase, k-feldspar, quartz and biotite. Accessories are iron-oxide, sphene, epidote and apatite. Alteration' Biotite is altered to chlorite in the matrix but the biotite phenocrysts show only weak chlorite alteration along cleavage planes. Amphibole is altered to carbonate and chlorite. PC4 Quartz Latite Porphyry Sample is from barren quartz-feldspar-biotite porphyry from recent cut on the Cork property. The sample is similar in mineralogy and texture to PCI and PC2 with 1% biotite as phenocrysts altering to chlorite along cleavage planes. PC5 Gabbro Sample is from barren gabbro along Johnson's Creek. Hypidiomorphic granular textured rock containing plagioclase (60% AngQ), hornblende (18%), orthopyroxene (3% hypersthene), clinopyroxene (13% augitic), magnetite (5%) and apatite (tr). PC6 Gabbro Sample is from the Cork property 500' south of PC5. Hypidiomorphic granular textured rock containing plagioclase (60%-Ango)» hornblende (20%) , pyroxene (8% mainly augitic), magnetite (5%), and apatite (tr) . Chlorite and carbonate (1%) occurs as alteration along fractures. Ruby Range Batholith, Yukon Territory (Fig. 4-2) PC7 Biotite Granodiorite Medium grained, hypidiomorphic granular textured rock contains 36% plagioclase (A1120) > 38% orthoclase, 19% quartz, 6% biotite and accessory apatite and sphene. Biotite shows minor alteration to chlorite along cleavage planes and edges. PC8 Biotite - Hornblende Granodiorite Medium grained, hypidiomorphic granular textured rock contains 58% plagioclase (An38), 10% orthoclase, 18% quartz, 8% biotite, 4% hornblende, 2% sphene and accessory apatite and magnetite. Biotite shows minor alteration to chlorite along cleavage planes and edges and plagioclase cores show minor alteration to sericite. Mount Haskin, British Columbia (Fig. 4-4) PC9 Granite Porphyry (ref. Gabrielse 1963, p. 94) Mineralized sampleMs from outcrop along southern edge of small "stock" on Mt. Haskin Mo property. The rock contains 60% phenocrysts that are 45% orthoclase, 25% quartz, 22% plagioclase (zoned albite) and 3% biotite in a micro-crystalline groundmass of K-feldspar-plagioclase- quartz-biotite. Apatite, zircon and pyrite occur as accessory minerals, and the hand specimen is cut by 1/4" molybdenite bearing quartz vein. Biotite contains inclusions of apatite and zircon and is altered to chlorite. PC10 Granite Porphyry Sample of barren d r i l l core (hole DM 68-16) is from northern edge of small "stock" on Mt. Haskin Mo property. The rock contains 35% phenocrysts that are 40% orthoclase, 40% quartz, 16% plagioclase (zoned oligoclase), and 4% biotite in a microcrystalline groundmass of K-feldspar-quartz- plagioclase. Garnet occurs as an accessory mineral. A quartz vein and quartz-carbonate-K-feldspar coatings along hairline fractures compose 20% of the thin section. Biotite phenocrysts are fresh, but a finer, felted secondary biotite, that is associated with fractures, is altered to chlorite. Mt. Reed, British Columbia (Fig. 4-4) PC11 Granite Porphyry Sample is from a barren "stock" on the Mt. Reed Mo-W property. The rock contains 60% phenocrysts that are 70% orthoclase, 20% quartz and 10% albite in a phaneritic groundmass of K-feldspar-albite-quartz- biotite. Sphene, apatite and magnetite occur as accessory minerals. Biotite shows 5% alteration to chlorite along cleavage planes and edges. PC12 Granite Porphyry Sample is from the central mineralized part of the small "stock" on the Mt. Reed Mo-W property. The specimen contains 80% phenocrysts that are 50% orthoclase, 25% quartz, 20% albite and 5% biotite in a microcystalline groundmass of quartz-K-feldspar-plagioclase-biotite. Apatite, sphene, and magnetite occur as accessory minerals. Biotite- shows minor chlorite alteration along edges. Cassiar Area, British Columbia (Fig. 4-5) (young phase of Cassiar Intrusions that cuts Cassiar Batholith) PC13 Quartz Monzonite Medium grained, hypidiomorphic granular rock contains 32% plagioclase (An3Q, 30% K-feldspar-(microperthite), 30% quartz, and 8% biotite. Apatite sphene and magnetite occur as accessory minerals. Biotite is 10% altered 108. to green biotite and chlorite. PC14 Quartz Monzonite Medium grained, hypidiomorphic granular rock contains 35% quartz, 30% plagioclase (An30), and 24% K-feldspar (microperthite). Sphene (1%), apatite (1/2%), zircon (tr) and magnetite (tr) occur as accessory minerals. Biotite is 10% altered to chlorite along cleavage planes and edges. Adera Claims - Adanac Mo Property Atlin Area, British Columbia (Fig. 4-5) PC15 Coarse Alaskite (ref. Sutherland Brown 1969, pp. 29-35 Coarse grained, hypidiomorphic granular rock contains 30% K-feldspar (perthite), 38% quartz, 27% plagioclase (zoned oligoclase), 2% carbonate, 1% biotite and 1% allamite. Molybdenite, pyrite, zircon, sphene and apatite occur as accessory minerals. Biotite is 20% altered to chlorite. Syenite Range, Yukon Territory (Fig. 4-1) PC16 Quartz Monzonite Coarse-grained, hypidiomorphic granular rock contains up to 3/4" crystals of K-feldspar (40%) in finer-grained, phaneritic quartz (15%), plagioclase (An28-30%), hornblende (7%), biotite (5%), sphene (1%), apatite (1%) and accessory zircon, fluorite, magnetite and allanite. Alteration Biotite shows minor chlorite alteration and contains inclusions of apatite, sphene, quartz and other accessories. Hornblende shows stronger alteration to chlorite, carbonate, epidote and biotite. PC17 Quartz Monzonite Although this specimen was obtained from the margin of a small stock, mapped by Bostock "(1948) as zoned from a granite core (PC16) to a syenite outer rim, the specimen is texturally and mineralogically similar to sample PC16. Samples PC16 and PC17 were collected by K. Dawson and C. Godwin. Copper Mountain, B.C. (Fig. 4-7) KA1 to KA11 Samples KA1 to KA11 inclusive were obtained from Dr. V. Preto. Specimens and K-Ar ages obtained on biotite concentrates are described by Preto et al. (1971). Granisle, Central British Columbia (Fig. 4-6) NC-69-8 Sulfide Rich Vein This sample is from a biotite (25 to 50% altered to chl.)-quartz- feldspar-apatite-bornite-chalcopyrite vein that was exposed in the Granisle open-pit in 1969. N. Carter collected the sample and has obtained a K-Ar biotite age of 50.2+2.1 m.y. for this sample (N. Carter personal communication). Brenda Mines, Southern British Columbia JH5-68 Quartz Diorite (ref. Oriel 1972) This sample is from the speckled quartz diorite phase of the Brenda stock. Dr. W.H. White provided a 90% sphene concentrate from this sample. Concordant ages of 174 + 7 m.y. on biotite and 177 + 7 m.y. on hornblende have been obtained for this sample (J. Harakal personal communication). 110. APPENDIX B - POTASSIUM-ARGON METHOD B.l PROCEDURE Biotite and hornblende potassium-argon ages were determined in laboratories of the Department of Geology, University of British Columbia, using procedures and equipment previously described (White et al. 1967, p. 683; Northcote 1969, pp. 61-65). In addition to the normal procedure, the sample and entire fusion system were baked at 130°C for 16 hours which effectively eliminates atmospheric argon contamination in the fusion system (Roddick and Farrar 1971). Analytical data and K-Ar isotopic ages are given in Table 2-1. B.2 PRECISION AND ACCURACY The precision and accuracy of the potassium-argon age determinations must be continually monitored to determine reliability of potassium-argon model ages. Interlaboratory standard mineral and rock samples are analyzed in the U.B.C. potassium-argon laboratory to establish the accuracy of the equipment and replicate analyses of minerals are used to determine the precision of the equipment (see White et al. 1967, and Northcote, 1969). J. Harakal runs periodic checks on the Ar^°/Ar36 ratio of atmospheric argon and on the argon isotope ratios in the spike system as measured on the U.B.C. MS-10 mass spectrometer. For samples containing less than 50% atmospheric argon contamination, U.B.C. results are internally consistent within 1% and a limit of error in an age determination (accuracy) is within 3% of the calculated age (J. Harakal, personal comm. June 1972). rOO 90 c o 0 8 O s "I IO 20 30 40 50. 60 70 SO 90 (OO Atmospheric correction (° /o) Figure Estimated precision for determining the ^°Ar/*°K (B-l) . ratio as afunction of the atmospheric correction (from Damon, 1968). 112. B.3 ATMOSPHERIC CONTAMINATION The atmospheric argon correction often introduces the largest error in the precision of the calculated age. The percentage standard deviation in a potassium-argon age as a function of the fraction of radiometric argon is shown in Figure B-l. This diagram demonstrates the effect of subtracting a large percentage of atmospheric argon from the total Ar 4^ measured. Error increases rapidly once atmospheric contamination reaches about 70% and therefore, the baking procedure described above should be used even i f samples are not likely to be suitable for isochron determinations. B.4 APPLICATION OF A r 4 0 (RAD.) VS %K ISOCHRONS TO PUBLISHED DATA K-Ar data (Table B-2) from the Topley Intrusions and (Table B-l) from the Guichon Batholith was evaluated using Ar4*-* radiogenic vs %K diagrams. Plotting of Ar 4 0/Ar 3^ vs K 4 0/Ar 3^ diagrams is not attempted because the fusion system had not been baked prior to each analysis. B.4.1 Guichon Batholith Figure B-2a contains a plot of Ar 4 0 rad. vs %K data for 18 biotite samples from the Guichon Batholith. A mean of the individual K-Ar ages of 199 + 4 is in good agreement with the isochron age of 196 + 5 m.y. and the intercept near zero suggests that the use of the present atmospheric Ar^O/Ar3^ ratio in the correction for i n i t i a l argon is reasonable. Figure B-2b is a plot of Ar 4^ rad. vs %K data for 6 biotite samples from the Witches Brook phase of the Guichon Batholith. The isochron age of 189 + 9 m.y. for the Witches Brook phase is consistent with the composite isochron age and with the mean biotite K-Ar age of 199 + 5 m.y. for the Witches Brook TABLE Potassium-argon data for Guiohon Creek Batho l i th (Northcote, 19691 White B- l et a l . 19671 Blanchflower, 1971). 40 4o Sample No. Ar*» Ar * *» Apparent (Isochron Mineral trr,— (10~ 5 co Age* * * * No.) Rook Unit analyzed* K±s(J*)*» Tota l u A r STP/gm) (m.y.) K64-102 (1) . Witches Brook. B i o t i t e . 4.91 ±0.03 4.91 ±0.03 . 0.87 0.91 • 4.055 4.077 198±8 199+8 K64-105-1 (2) Witches Brook B i o t i t e 6.53 ±0.04 0.90 5.442 198±S K63-171 (3) Witches Brook B i o t i t e 6.59 +0.06 0.75 5.263 192±8 K64-203 (4) Witches Brook B i o t i t e 4.42 ±0.02 4 .42 ±0.02 0.64 0.79 3.759 3.750 203±8 203±8 K64-17 (5) Witches Brook B i o t i t e 3.59 +0.02 0.74 3.093 206±8 K63-222 (6) Wltohes Brook B i o t i t e 7.16 +0.01 0.87 5.903 198±8 K63-223 (7) Guichon B i o t i t e 5.77 ±0.02 0.87 4.689 195+8 GD12 (8) Guichon B i o t i t e Hb . (a l t . ) 5.56 +0.01 0.424±0.004 0.83 0.60 4.663 0.3629 201+8 205±8 K64-ll6a (9) Chataway B i o t i t e . 5.24 +0.04 0.77 4.358 199±8 K63-220 (10) Chataway-Leroy B i o t i t e 5.20 +0.02 5.20 ±0.02 0.92 0.30 4.325 5.390 199±8 201±10 K63-37 (11) Leroy B i o t i t e 6.42 ±0.03 6.42 ±0.03 0.78 0.85 5.385 3.795 201±8 202±8 K64-101 (12) Leroy B i o t i t e 5.16 +0.05 0.90 4.295 199+8 K63-13 (13) Hybrid B i o t i t e 4 .49 ±0.02 4 .49 ±0.02 0.91 0.52 3.716 5.776 198±8 206±8 K64-156a (14) Hybrid B i o t i t e 6.73 ±0.01 0.93 5.659 198±8 K64-98-1 (15) Gump Lake B i o t i t e 5.95 +0.01 5.95 ±0.01 0.37 0.91 4.817 4.919 194+10 198+8 K63-I87 (16) Bethsalda B i o t i t e 4.48 ±0.02 4.48 ±0.02 0.80 0.88 3.573 3.648 192+8 195±8 K63-231 (17) Bethsalda B i o t i t e 5.86 +0.07 0.86 5.044 205+8 K63-240 (18) Brecola B i o t i t e 5.60 ±0.01 0.84 4.643 199+8 K63-II5 (19) Bethlehem B i o t i t e 5.90 ±0.07 0.90 4.307 195+8 GD-10 (20) P3 Porphyry Hb . (a l t . ) 0.292±0.002 0.53 0.2432 199+8 GD-102 (21) P3 Porphyry H b . ( a l t . ) 0.140±0.001 0.140±0.001 0.24 0.39 0.09845 0.09879 170±12 171±12 K64-186a (22) Bethlehem B i o t i t e 1.87 ±0.01 1.87 ±0.01 O.83 0.27 1.644 1.634 210+12 212±12 GD-5 (23) Daclte Porphyry B i o t i t e 5.56 ±0.03 0.50 4.717 203+8 GD- l l a (24) Bethlehem H b . ( a l t . ) o.l6i±o.oo 0.44 O.1305 194±10 GD-4 (25) Guichon H b . ( a l t . ) O.I69+.O.OOI 0.60 0.1474 208+8 K63-114 (26) Volcanic dike B i o t i t e 6.99 ±0.02 6.99 A0.02 0.88 O.83 1.389 1.433 49±3 51±3 • Hb . (a l t . ) = a l te red hornblende • * Potassium analyses by Wm. H. White, J . E . Harakal and others using KY and KY-3 flame photometers, s-standard deviat ion of quadruplicate analyses. • • • Argon analyses by J . E . Harakal and others using MS-10 mass spectrometer. n » • « * Constants used in model age ca lcu la t ions 1 i p = 0.585 x l 0 - 1 0 y - l , a = It.72 x l 0 _ l ° y 40KA = 1.181 X 10-*. '  C  • " 114. TABLE Potassium-argon data for the Topley Intrusions (from White et a l t , 19?0, and White B-Z et a l . , 1968). Sanrple No, f T or»r« h r n n Mineral analyzed *°Ar* 4 0 ^ . (10"-" 00 STP/gm) Apparent Age**« (m.y.) No. Rook unit Type K±s(#)* Total ̂ °Ar T66-15 (1) Endako Qtz. Monzonite Biotite 5.6710.07 0.82 3.328 14316 T66-14 (2) Endako Qtz. Monzonite Biotite 6.4610.03 0.85 3.748 14115 T65-3 (3) Endako Qtz. Monzonite Biotite 5.8110.04 0.70 3.318 140t6 T66-21 (4) Nlthl Qtz. Monzonite Biotite 5.13±0.04 0.89 2.974 I4lt6 T66-20 (5) Nithl Qtz. Monzonite Biotite 5.80±0.03 0.78 3.281 13815 T66-25 (6) Glenannon Qtz. Monzonite Biotite 4.58+.0.03 0.75 2.639 140±6 T67-29 (7) Glenannon Qtz. Monzonite Biotite 4.3910.02 4.3910.02 O.65 0.87 2.419 2.423 134i5 13515 T66-10 (8) Tatln Qtz. Monzonite Biotite 5.6910.04 0.73 3.327 I42t6 T66-27 (9) Tatln Qtz. Monzonite Biotite 6.59±0.02 O.65 3.687 13615 T66-18 (10) Casey Qtz. Monzonite Biotite 5.*>6±o.03 0.80 3.118 139±5 T66-26 (11) Casey Qtz. Monzonite Biotite 6.34±0.06 0.68.. 3.558 137t6 T67-3I (12) Francois Granite Biotite 6.0610.03 0.80 3.408 137±5 T67-3O (13) Francois Qtz. Monzonite Biotite 5.3l±o.05 0.76 2.993 137+6 T66-16 (1*) Stellako Qtz. Monzonite Biotite 4.9910.03 0.65 2.804 I37t5 T65-2 (15) Stellako Qtz. Monzonite Biotite 3.70±0.03 0.57 2.063 136t5 T66-11 116) Triangle Qtz. Monzonite Biotite 6.2110.01 6.2210.01 0.85 0:78 3.393 3.403 13315 133+5 T65-4 (17) Casey Qtz. Monzonite Biotite 7;054±o,026 0.85 4.099 14115 T66-23 (18) Casey Qtz. dike -Biotite Biotite ?.03±o.o6 0.58 4.012 13916 T65-6 (19) Qtz. Monzonite Biotite 6.90310.025 0.88 3.961 14015 T66-12 (20) Qtz. Monzonite Biotite 6.94+.0.03 0.82 4.064 14215 T66-13 (21) Bio. K i t h qtz.- rnoly vein Biotite 6.5310.02 0.74 3.808 14215 T68-33 (22) Simon Bay Diorite Hb. 1.2110.01 0.62 0.7745 155+8 T68-33 (23) Simon Bay Diorite Biotite 3.7210.07 0.86 2.221 14518 T68-33 (24) Simon Bay Diorite Plagioclase 1.78+0.01 0.70 1.007 13816 T66-22 [25) Simon Bay Qtz. Monzonite Biotite 6.7610.105 6.7610.105 0.78 0.85 4.313 4.317 155+6 155±6 T66-28 [26) Late dike Daclte Biotite 6.25+0.04 6.2510.04 0.58 0.65 1.264 1.277 50+2 51±2 T65-I [27) Praaer Qtz. Monzonite Biotite 5.23+0.02 5.23+0.02 0.58 0.40 2.424 2.385 114±4 11214 * Potassium analyses by Wm. H. White, T. Richards, and I. Semple using KY and KI-3 flame photometers, s.-standard deviation of quadruplicate analyses. ** Argon analyses by J , E. Harakal using M3-10 mass spectrometer. •»* constants used in model age calculations. /)_- O..585 1 IO" 10 /" 1 , J V - 4.72 x 10" 1 0 y - 1 , *°K/fc - 1.181 x 10-4. e J'fi 115. Regression Results Intercept Slope 0.08321 ±0.2 236 0.8176*0.02321 .Guichon 0.01572*0.1615 0.5895+0.04017 T68-33 •0.1293* 0.1670 0.5930*0.01645 Topley 3 8 3 \ P-< EH CO O 2 o o % Regression Results Intercept Slope 0.2579*0.3592 0.7853*0.03714 10 2.0 4.0 5.0 6.0 7.0 a. Isochron plots for data from the Guichon Batholith, • Topley Intrusions, and sample T 6 8 - 3 3 from the Topley Intrusions. b. Isochron plot for the Witches Brook Phase of the Guichon Batholith. 116. phase of the batholith . . B.4.2 Topley Intrusions K-Ar data for the Topley Intrusions near Endako, British Columbia has been interpreted by White et al. (1970) to indicate either one protracted perhaps intermittent magmatic event culminating in early Late Jurassic or three separate and unrelated events. Isochron plots of the Topley data were attempted in order to evaluate the two alternatives. The Triangle, Stellako, Francois, Casey, Tatin, Glenannon, Nithi and Endako phases of the Topley Intrusions have biotite K-Ar ages ranging from 133 m.y. to 143 m.y. and a mean age of 138 + 3 m.y. The Simon Bay phase has a 155 m.y. age for biotite from sample T66-22 and from sample T68-33 discordant ages of 155, 145 and 138 m.y. The Topley isochron shown in Figure B-2a is from data (Table B-2) used to obtain the 138 + 3 m.y. mean age and the isochron age of 144 + 4 m.y. is consistent with the mean age. Hornblende, biotite and plagioclase data for sample T68-33 plots on an isochron that is parallel to the Topley isochron and has an isochron age of 143 + 10 m.y. For both the Topley isochron and sample T68-33 isochron, the isochron age and mean age of the conventional K-Ar determinations are consistent. Since the isochron and mean ages overlap, the isochron plots cannot be used to distinguish between continuous igneous activity or an intrusive pulse model. B.4.3 Summary Application of Ar 4^ (rad) vs %K isochron plots to data from the Topley Intrusions and Guichon Batholith supports the conventional age 117. determinations. In both cases the mean age of the conventional determinations is consistent with the isochron age. For both the Topley Intrusions and the Guichon Batholith the i n i t i a l argon ratio is essentially the same as the present-day value (Ar 4 o/Ar 3^ = 295.5). 118. APPENDIX C - FISSION TRACK DATING C.l INTRODUCTION Fission track dating provides a method for using normal laboratory equipment for determining the age of nonconductors. Once polished section mounts are obtained, track counting and age determination takes only a few hours for materials with suitable age to uranium ratios. Unfortunately, in this study pre-counting steps consumed a majority of the time. C.2 PROCEDURE Fission track dating involves: (a) determining the spontaneous fission track density (p s) on an etched interior surface of a mineral or other nonconductor, (b) using the calculated value for fission decay of U 2 3 8 ( Ap), and (c) determining the U 2 3 8 content. Step 1. MINERAL SEPARATION Concentrates of the mineral to be used for fission track dating are obtained using standard mineral separation methods (see flow sheet Fig. C-l and Table C-l). Care must be taken during mineral separation and subsequent steps to ensure that tracks are not annealed by heating. Step 2. DIVISION OF SAMPLE The mineral concentrates (65-95%) pure are split to obtain two portions. One portion is*_used to obtain the spontaneous (natural) track density, and this sample is saved t i l l Step 6. 119. Figure C-1 Flowsheet for mineral separating iiHimiiiiim v Jaw Crusher Gyratory Crusher _____ Cone Crushers I Primary Secondary * — » I J mesh I -28+35 4- high surface | -35+48-— area minerals -48 + 65- |Save -65~ J ur Dryer • 50°c Water j± Dryer <50°c Pulverizer Screens __r > 28 mesh | \ ~ / B r o m o f o r m I N N - / ' V c^C^n „ . Acetone H' X S .G.>2.8^Aceton_ co Metheline Iodide u S-G.>3.2 i Remove Magnetite - * with Hand Magnet Save? Feldspar, Quartz, etc. CJ to Apatite, Biotite, Hornblende * Acetone Wash I Magnetite, Zircon, Sphene, Epidote, etc. Acetone Wash Magnetic Cleaner - See Table C-1 120. TABLE C-l FRANTZ SEPARATION SETTINGS FOR DESIRED MINERAL SEPARATION (ROSENBLUM, 1958, p. 171) Mineral Cross t i l t Flow t i l t Current amps Fraction used Magnetite Ilmenite Pyrrhotite Hornblende Pyroxene Biotite Sphene Zircon Molybdenite Pyrite Fluorite Apatite less 0.2 0.2-0.5 I I 0.6-1.0 greater 1.2 n heavies lights heavies lights ti Step 3. PREPARATION OF SAMPLES FOR IRRADIATION The second portion obtained from the split is placed in a porcelain crucible. This portion of each sample was annealed in an electric oven for 24 hours at 650 + 25°C. Naeser (1967 p. 54) determined that annealing for one hour at 350°C and 625°C for apatite and sphene respectively will cause 100% track destruction. Therefore it is assumed that a l l spontaneous tracks were destroyed in the annealing procedure used by the writer. Annealed apatite and sphene samples weighing between 0.01 and 0.2 gm. (minimum of 100 grains but generally several hundred) were next wrapped in high purity aluminum fo i l (provided by Mr. F.T. Murphy of AECL). Glass standards* weighing between 0.1 and 0.2 gm. (1mm x 5mm. x 5mm) * Standard glass used to calibrate UBC reactor run 1 was provided by Dr. Charles Naeser of the U.S. Geological Survey. were prepared in two different ways. One standard was in aluminum f o i l . A second standard was cleaned in a sequence of reagent grade solutions, including 50% ammonium hydroxide, acetone benzene and rinsed in deionized water, and then wrapped in a plastic detector which has been cleaned in reagent grade n i t r i c acid, and rinsed in deionized water (Lahoud et a l . , 1966). The sample with the plastic detector was also wrapped in aluminum f o i l . Step 4. SAMPLE IRRADIATION Wrapped mineral samples and glass standards' were placed in an aluminum capsule. The capsule was sealed and irradiated by Atomic Energy of Canada Limited in the self-serve unit of a NTX Reactor. A flux of 1.2 x lO^nvt was requested and a cobalt tag included in the run was calibrated by the laboratory to have received a flux of 1.05 x 15 12 2 10 nvt (1.35 x 10 n/cm /sec for 13 minutes). Step 5. FLUX DETERMINATION Mr. F.T. Murphy of AECL (personal communication) suggested that the flux determined using the cobalt tag should be within 5% of the actual value, but Dr. C.W. Naeser (personal communication) has found that standards containing known uranium contents provided a more accurate determination. Three separate determinations provide independent support for a flux value of 1.31 x lO^nvt + 5%. These determinations include: (1) count of induced tracks produced in standard glass included in the reactor run, (2) comparison of the ratio of tracks/area in the standard glass included in the U.B.C. reactor run with the ratio of tracks/area in a piece of the same. 122. standard glass included in the Dartmouth reactor run 1 (flux of 1.A6 x lO-^nvt was calculated by Dr. C.W. Naeser for the Dartmouth reactor run) and (3) count of induced tracks/area produced in standard apatite Mc/G-1 that has a mean fission track apatite age of 120 m.y. and a concordant biotite K-Ar age of 120 m.y. (Christopher 1968). Step 6. MOUNTING AND POLISHING In order to handle 28-100 mesh mineral grains during fission track analysis, i t is necessary for them to be mounted. The sample preparation procedure described by Naeser (1967, pp. 75-76 and 1967b, p. 1524) was used as a guide in preparing mounts. At least 100 grains from each mineral concentrate are placed on a teflon sheet. The grains are then covered with a few drops of freshly mixed epoxy resin, and a labelled glass microscope slide is placed on top of the resin. The thickness of the epoxy wafer is gauged by placing a 0.1 to 0.5mm spacer at each end of the slide. Placing an iron weight on each mount eliminates bubbles from the mounts and produces an epoxy wafer of uniform thickness. After allowing the resin to dry for about 12 hours, the mounted sections are removed from the teflon sheet. The mineral grains in the epoxy wafer must be polished to expose a fresh smooth interior surface. The grinding and polishing employed standard manual methods. An attempt was made to produce identical mounts of natural and irradiated mineral samples. Lack of a mechanical method for producing polished thin sections is considered to be one of the major problems in 123. application of the fission track method. After spending over two hours (average) per polished section, variability in sections is considered to be one of the major sources of error. The glass standard is mounted and polished in the same manner as the mineral grains. Other laboratories (Rensselaer and General Electric) have used fracturing methods for preparing the glass standard. Step 7. ETCHING Two slides of each mineral concentrate must be used to obtain an age. One slide is made from the natural mineral concentrate (Plates 1 and 3). A second slide is made from the annealed and irradiated portion (Plates 2 and 4). The two slides are placed back to back and dipped in an appropriate etchant (see Tables C-2 and C-3). For minerals with variable composition (e.g. apatite, epidote or micas), the etching has to be done in steps and the tracks examined at intervals to obtain the proper etch time. * The track density in the glass before irradiation is essentially zero, and therefore only the irradiated glass standard is mounted, polished to expose an interior surface and etched (Plates 5 and 6). A Makrofol KG plastic detector (polycarbonate) was also used to detect induced fission in the glass. Unfortunately the plastic detector was over etched. Step 8. COUNTING TRACKS Track densities for etched apatite and sphene samples were determined by observation using a polarized-light-microscope at about 1500x (magnification obtained from Zeiss lOOx oil immersion objective, 12.5x eyepiece and 1.25x TABLE C-3. ETCHING CONDITIONS FOR FISSION-TRACK COUNTING. Material Etchant Temp. Time Reference Comments Apatite HN03(65%) 25°C Zircon (prism NaOH (100N) 220°C face) Glass (micros- HF (48%) 25°C cope slide) Muscovite (001) HF (48%) 25°C Sphene 1HF, 2HN03, 25°C 3HC1, 6H2O Sphene 6:3:2:1 20°C H20:HC1:HN03: HF Muscovite HF (48%) 20°C Zircon 100M NaOH 220°C Apatite HNO3 (5%) 20°C Apatite HNO3 23°C Glass HF (48%) 23°C Fluorite H2S04 (98%) 23°C Makrofol (KG) NaOH 6N 23°C Apatite HNO3 (70%) 20°C Sphene HCl (37%) 90°C Muscovite HF (48%) 20°C Epidote NaOH 50N 140°C Allanite NaOH 50N 140°C Garnet 50N NaOH 140°C Glass 24% HBF4, 25°C 5% HNO3, 0.5% CH3C02H Pyroxene 6 g. NaOH, boiling 4 co H2O point Plagioclase 6 g. NaOH, boiling 8 co H20 point 15 sec. Reimer et al. 1970 9 hrs. 5 sec. 15 min. 14 min. 1- 5 min. Naeser and McKee, 1970 7-9 min. 4- 6 hrs. 25 sec. 5- 30 sec.Fleischer and Price, 1964d 5 sec. 10 min. " 2- 2-1/2 ' Lahoud et al., 1966 hrs. 5-20 sec.Naeser and Dodge, 1969, unpublished 15-60 min. 5-15 min. " " 1/2-2 hr.Naeser, Engels and Dodge, 1970 2-60 min. 30-120 11 " min. 35-50 Macdougall, 1971 compares other min. etchants 50 min. Wilkening et al., 1971 12 min. 125. setting on an optivar magnification changer). Track densities for etched glass standards were determined by observation using a reflected- light microscope at about lOOOx (magnification obtained from a Zeiss 40x objective, 12.5x eyepiece and 2.Ox setting on an optivar magnification changer). Tracks are counted in the field of view covered by a square reticle (Plate 7). The number of fields counted varied with the track density. Since the counting error decreases with increase in the number of tracks counted, a minimum of 400 counts is desirable. The standard deviation of the track counts is taken as the square root of the number of tracks counted (Naeser 1967b). This formula yields a counting error of + 5% for 400 counts. TABLE C-2 ETCHING TECHNIQUES USED FOR MATERIALS STUDIED Material Etchant Etch Time Temp. Reference Comments Apatite Glass slide (standard) Sphene Zircon Makrofol (K6) 65-70% 5-30 sec. 23°C 48% HF 6:3:2:1 H20:HCL: HN03:HF 100M. NaOH 6N NaOH 5 sec. 1-5 min. 23°C 20°C 4-6 hrs. 220°C 2-2-1/2 hr. 23°C Fleischer and Time varies Price, 1964d with composition Naeser et al. 1970 Naeser and McKee, 1970 Lahoud et al. 1966 Step 9. URANIUM DETERMINATION By using a ratio of spontaneous tracks to induced tracks, the determination of absolute uranium content can be bypassed in the age calculation. Lahoud et al. (1966) suggest that the fission-track method is 10,000x more sensitive than other analytical methods of determining uranium content. In theory, i t is possible to determine concentrations as low as 10~5ppb. The only limitation on the sensitivity is the effect of extremely large neutron doses on the sample and the availability of standards for determining the flux. In order to calculate the uranium concentration in a mineral phase, i t is necessary to know the induced track density and the neutron dose which produced the tracks. The formula is (Naeser 1967a): C(ppm U 2 3 8) = F p ±/ $ N ya IRQ where 238 (atomic weight of T J 2 3 8 ) x No. atoms in F mineral formula x 10^ molecular weight of mineral pi = induced track density: I = U 2 3 5/U 2 3 8, (7.26 x IO"3); a = thermal neutron cross section for fission of U 2 3 5 (5.83 x 10"22cm2); 3 N v = number of atoms per cm of sample; RQ = average fission fragment range (either 8 x 10~4 i f new surface is exposed and etched after irradiation, or 4 x IO - 4 cm i f an old surface is used. By substituting values for constants, the equation reduces to: C = 3.61 x 10 1 0 P i for apatite when F = 9.80 x 106 and N v = 0.8010 x IO 2 3 atoms/cc and to: C = 3.33 x 10 1 0 P i for sphene when F = 9.71 x 106 and N v = .8603 x IO 2 3 atoms/cc 128. Plate 1. Microphotograph showing spontaneous (natural) fission- tracks in standard apatite sample Me/G-1. Apatite from this sample has a spontaneous track density of 8.73 + 5 2 1.12 x 10 tracks/cm and a uranium content of 15.5 + 1.9 ppm. Scale 1 inch = 22 microns Plate 2. Microphotograph showing induced tracks in standard apatite Me/G-1. Annealed apatite grains were exposed to a thermal neutron flux of 1.535 x lO-^. The induced track density produced was about 6.96 x 10^ tracks/cm2. Scale 1 inch = 22 microns. Plate 3. Microphotograph showing spontaneous (natural) fission-tracks in sphene sample JH5. Cracks in sphene grains cause counting problems but can generally be distinguished from tracks of uniform size and characteristic shape. Scale 1 inch = 15 microns, Plate 4. Microphotograph showing faint induced fission-tracks in sphene sample JH5. Lines which cross entire plate are scratches produced during polishing. Scale 1 inch = 15 microns.  .130. Plate 5. Microphotograph showing induced fission-tracks produced in standard glass used to calibrate U.B.C. reactor run. Glass contains 0.4 ppm uranium and was radiated to a flux of 1.31 x 10 1 5 nvt. Scale 1 inch = 22 microns. Plate 6. Microphotograph showing induced fission-tracks produced in standard glass used to calibrate a reactor run. Glass contains 0.44 ppm uranium and was irradiated to a flux of 8 x 10 1 6 nvt (flux determined by S. Barr). Scale 1 inch = 22 microns. Plate 7. Microphotograph showing central part of a reticle used for measuring area from which track count was obtained. Scale 1 inch = 15 microns.  132. TABLE D-l APPENDIX D TABLE OF PUBLISHED K-Ar AGES REVIEWED FOR THIS REPORT Published K-Ar ages referred to In this report. Report Reference No. Number and Mineral Dated Age in m.y. Rook Type Unit Location Referenoe 1 AK50 Bio 2 GSC60-28 Bio 3 GSC67-12 Muso 4 GSC67-15 Bio 5 GSC70-35 Bio CASSIAR BATHOLITH - MEAN AGE 102 ± 3 m.y. 101 • Quartz monzonite Cassiar , 60°04'N. Batholith 130°29'W. 98 Blotlte- granodlorlte 105±5 Granltlo gneiss 105*5 Quartz monzonite 102t5 Quartz monzonite 32«N. °29*W. Batholith 131 margin of 6o°00'N. Cassiar 130°44'W. Batholith Cassiar 58°49'N. Batholith 129°52'W. Cassiar . 58°42.5'N. Batholith 128°43.5'W. Baadsgaard, et a l . . 1961 GSC Paper 6 l -17 1 p. 17 GSC Paper 69-2A, p. 9-10 GSC Paper 69-2A, p. 11 GSC Paper 71-2, pp. 21-22 LATE CRETACEOUS AGES 6 GSC67-14 Bio 78±4 Granite 7 GSC66-1 Hb 8 GSC70-4 Hb 9 GSC60-25 Bio 10 GSC70-49 Bio (replaces GSC59-14) 11 GSC70-50 Bio 79±11 Granite 7̂ +4 Granite 71 9 8 ± 5 Quartz monzonite Leuoo- quartz monzonite 97±5 Leueo- 92±4 quartz monzonite WEST OF CASSIAR BATHOLITH Parallel Creek Batholith 59°13.5'N. 130°23.5'W. Glundebery 5 9 ° 1 4 ' N . Batholith 130 ° 4 9'S. Glundebery 60°12'N. Batholith 131°06«W. unnamed 58°53 ,49"N. 130601'28"W. Seagull 60°02'32"N. Batholith 131°10 ,11"W. Seagull 60°04.5'N. Batholith 131°09'W. GSC Paper 69-2A, p. 1 0 GSC Paper 6 7 - 2 A , p. 1 1 GSC Paper 7 1 - 2 , pp. 7 - 8 GSC Paper 61-17, P. 1 5 GSC Paper 7 1 - 2 , p. 3 1 GSC Paper 7 1 - 2 , pp. 3 2 - 3 3 1 2 G S C 6 7 - 9 Hb 1 3 GSC67-IO Bio 1 4 G S C 7 0 - 1 9 Bio EARLY TERTIARY AGES - WEST OF CASSIAR BATHOLITH 48±4 Quartz unnamed 59°23'45"N. GSC Paper 69-2A, pp. 8-9 46t2 diorite ^l^O'SO"*. 58*18 Quartz Mount 59°22'N. GSC Paper 71-2, P. 14 diorite McMaster 133 0 12'W. Stock EARLY TERTIARY AGES - BODY INTRUDES CASSIAR BATHOLITH 15 G S C 6 7 - 1 Muso 58±3 Quartz unnamed 59°39'N. GSC Paper 6 9-2A, p. 6 monzonite stook? 130°20.5'W. 1 6 GSC67-2 Muso 53±3 Pegmatite • 5 9 ° 3 9 ' N . GSC Paper 69-2A, p. 6 130627.5*W. E A R L Y TERTIARY ACE - EAST OP CASSIAR BATHOLITH 1 7 G S C 6 2 - 7 4 Muso 5 7 GnelBS Horse Ranch 5 9 ° 3 0 , 4 0"N. G8C Paper 63-17, p. 4 8 Group 128°55'45"W. * See referenoe. 133. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Beport Reference No. Number and Mineral Dated Age In m.y. Hook Type Unit Location Referenoe NOME LAKE AND SIMPSON PEAK BATHOLITHS, NORTHERN B. C. 18 19 CSC67-3 GSC67-4 Hb Bio ,181±14 165±8 . Quartz monzonite Simpson Peak Batholith 59°44'N. 131026*45"W. GSC Paper 69-2A , pp. 6-7 20 21 GSC67-5 GSC67-6 Hb Bio 183±9 183±8 Quartz monzonite Nome Lake Batholith 59°37'N. 130 6 53.5'W. GSC Paper 69-2A . P. 7 PLATE CHEEK STOCK, NORTHERN B.C. 22 GSC70-23 Hb 184*10 Quartz diorite Plate Creek59°53'N. Stock 130°45.5'W. GSC Paper 71-2, p. 16 23 GSC67-11 Hb 159±10 Quartz diorite Plate Creek Stook 59°52'30"W. 130 6 45'W. GSC Paper 69-2A . P. 9 PARALLEL CREEK, KLINKET AND TUYA BATHOLITHS, NORTHERN B.C. 24 GSC70-24 Bio 87+4 Quartz monzonite Kllnket Batholith 59°28'N. 131°13'W. GSC Paper 71-2, pp. 16-17 25 GSC67-13 Bio 92*5 Granite Tuya Batholith 59°04.3'N. 130°43'W. GSC Paper 69-2A p. 10 6 GSC67-14 Bio 78*4 Granite Parallel Creek Batholith 59°13.5'N. 130°23.5'W. GSC Paper 69-2A p. 10 CHRISTMAS CHEEK BATHOLITH, NORTHERN B.C. 26 GSC70-20 Hb 177±9 Quartz diorite Christmas Creek Batholith 59°18'N. 131°40.5'W. GSC Paper 71-2, P. 15 27 28 GSC67-7 GSC67-8 Hb Bio 128*6 56*3 Quartz diorite Christmas Creek Batholith 59°22'30"N. GSC Paper 69-2A, PP. 7-8 29 30 GSC66-2 GSC66-3 Hb Bio 146*17 73+5 Quartz diorite Christmas Creek Batholith 59°16'N. 131°29"W. GSC Paper 67-2A, pp. 11-12 HOTAILUH BATHOLITH, NORTHERN BRITISH COLUMBIA 31 32 GSC70-27 GSC70-28 Hb Bio 147±8 139+6 Grano- diorite Hotalluh Batholith 58°09.6'N. 129°51.9'W.. GSC Paper 71-2, pp. 17-18 33 34 GSC70-29 GSC62-71 Hb Hb Bio I66t8 157*11 193 Granite Hotalluh Batholith 58°08'30"N. 129°52*00"W. GSC Paper 71-2, GSC Paper 63-17, p. 18 pp. 45-46 35 GSC70-30 Hb 155±8 Quartz monzonite Hotalluh Batholith 58°10.5'N. 129°38.5'W. GSC Paper 71-2, p. 19 3« 37 GSC70-31 GSC70-32 Hb Bio 163±9 163*7 Quartz Hotalluh monzonite / Batholith granodiorite 58°07.5*N. 129°30'W. GSC Paper 71-2, P. 19 38 GSC70-33 Hb Hb 215±H 2 1 5 t H Monzonite/ quartz monzonite Hotalluh Batholith 58°10'N. 129°39'W. GSC Paper 71-2, p. 20 39 GSC70-34 Hb Hb 217*11 217*11 Diorite Hotalluh Batholith 58oo4.5«N. GSC Paper 71-2, p. 20 4o 41 GSC70-25 GSC70-26 Hb Bio 161*8 141*7 Quartz monzonite Hotalluh Batholith? 58°15.5'N. •130°15.5*W. GSC Paper 71-2, P. 17 * See referenoe. 134. TABLE D-l (cont'd) Published K-Ar ages referred to i n this report. Report Referenoe No. Number and Mineral Dated Age in m.y. Rook Type Unit Location Referenoe EARLY CRETACEOUS STOCK, NORTHERN B.C. 4 2 GSC70-21 Hb Hb 112*28 Bi o t i t e 120t26 quartz d i o r i t e Tachllta Lake stock .58°38.5'N. 130656'W. .GSC Paper 71-2, p. 15 4 3 GSC70-22 Bio 137±6 Hornblende quartz d i o r i t e Tachllta Lake stook * GSC Paper 71-2, pp. 15-16 HOGEM BATHOLITH, NORTHERN B.C. 44 GSC70-11 Bio 122±6 Granite Hogem Batholith 56°20'113'N. 125°49'W. GSC Paper 71-2, p. 11 45 K65-1 Bio 1?0±8 Syenite Hogem Batholith 55°56'N. 125°28'W. Lorraine White et a l . 1968» 1968 Koo, COAST LATE CRETACEOUS AND EARLY TERTIARY AGES INTRUSIONS, NORTHERN B.C. AND SOUTHEASTERN ALASKA 46 GSC61-39 Bio 5 4 B i o t i t e granodiorite Coast Intrusions 59°44'N. 134059'W. GSC Paper 62-17, P. 23-24 47 GSC61-38 Bio 65 B i o t i t e granodiorite « 590^7130"N. 135000'30"W. GSC Paper 62-17, P. 23 48 GSC61-46 Bio 65 Granite r. 5 9°34'N. 135 6 ll'W. GSC Paper 62-17. P. 29 49 GSC61-47 Bio 70 B i o t i t e granodiorite f. 59°30'30"N. 135°13'30"W. GSC Paper 62-17. P. 29 50 GSC60-26 Bio 61 Granite 59°37'N. 1350o8-w..i_ GSC Paper 61-17. P. 15-16 51 GSC60-27 Bio 68 B i o t i t e 59°50'30"N. 135O01'W. GSC Paper 61-17, p. 16 52 GSC62-75 Bio 69 Quartz monzonite m 58°34'24"N. 133°18' 00"W. GSC Paper 63-17, p. 49 53 GSC66-6 Bio 44±2 Granodiorite " mouth of Soud River - White et a l . 1 9 6 8 54 GSC60 - 3 4 Bio 30 Quartz d i o r i t e * 59*18'N. 135°20'W. GSC Paper 61-17, p. 20 EARLY TERTIARY AGES - EAST MARGINAL PLUTON (ALASKA) 55 PM3-1 Bio 4 8.7±1.8 Monzonite 1 East Marginal Pluton 58°44'N. 133°51'w. Porbes and Engels, 1970 56 PM3-2 Bio 52.8±2.6 Quartz monzonite m 58°43« 30"N. 133°52'30"W. 57 EN-2 Whole R 51.Itl.5 Quartz monzonite n 58°43'N. 133°55'W. 58 EN-3 Whole R 46.9±1.4 Quartz monzonite . 58°43'N. 133058'W. 59 EN-4 Bio 49.6±1.4 Quartz monzonite N 5 8°4l'N. 133°59'W. 60 EN-5 Whole R 51.011.0 Quartz monzonite M 58°40'30"N. 134oo4'W. 61 EN-6 Bio 4 7 . O t l .6 Quartz monzonite w 58°39'N. 134°18'W. • See referenoe. 135. TABLE (cont'd) Published K-Ar ages referred to In this report. D-l Report Referenoe No. Number and Mineral Dated Age In m.y. Rook Type Unit Looatlon Referenoe KING SALMON LAKE AREA, B.C. 62 GSC62-76 Bio 22? 63 GSC62-77 Bio 206 Granodiorite boulder in oong. 58°34'40"N. GSC Paper 6 3 - I 7 , PP. 49 -50 133°02'30"W. GSC Paper 63-I7, p. 50 STIKINE COPPER, NORTHERN B.C. 64 GC66-1 Bio 174±9 65 GC66-2 Bio I 8 9 + 9 66 GC66-5 Bio 182±9 Granite » (chlorltlc) 67 GC66-7 Bio 177+9 Syenite Copper Canyon syenite 6 8 A 6 4 - 1 Bio 198+7 Central ore White et a l . , 1 9 6 8 zone DDH GC193 8 400' Central ore " zone DDH GC148 @ 519' Central ore zone BLUE RIVER ULTRAMAFIC INTRUSIONS, NORTHERN B.C. 69 G S C 6 4 - 1 Whole R 2 4 5 ± 8 0 Amphibolite • 5 9°32'N. GSC Paper 6 5 - 1 7 , p. 7 129058'W. 7 0 GSC62-68 Muse 7 1 G S C 6 2 - 6 9 Bio CASSIAR INTRUSIONS NEAR DALL LAKE, B.C. 1 3 9 1 2 3 Quartz monzonite 59 027'N. 1 2 7 ° 4 2'W. GSC Paper 6 3 - 1 7 , pp. 44 -45 72 GSC62-72 Bio 124 7 3 GSC62-73 Muso 1 9 4 7 4 G S C 6 2 - 7 0 Muse, 1 7 8 Gneiss Gneiss Oblique Creek* 59°57"N. 131°58«W. GSC Paper 6 3 - 1 7 , pp. 46-47 5 8 ° 5 8 ' 3 6 " N . GSC Paper 6 3 - 1 7 , p. 4 5 1 3 0 ° 0 1 ' 2 4 " W . 7 5 G S C 7 0 - 9 Whole R 4 9 ± 5 7 6 G S C 7 0 - 1 0 Whole R 5 3 ± 6 SUSTUT GROUP, NORTHERN B.C. Tuff Tuff Sustut Group Sustut Group 5 7 ° 1 9 ' N . 1 2 7 ° 4 0 ' W . 56°54'H. 1 2 6 ° 5 6 ' W . GSC Paper 7 1 - 2 , pp. 9 - 1 0 GSC Paper 7 1 - 2 , p. 1 0 77 GSC70-14 Muso 78 GSC70-15 Bio 4713 43±3 WOLVERINE COMPLEX, NORTHERN B.C Granite Wolverine Complex 56°23'N. 125°21.5'W. GSC Paper 71-2. p. 12 79 GSC70-12 80 GSC70-13 Muso Bio INGENIKA GROUP, NORTHERN B.C. 1 2 8 l 6 1 2 4 ± 6 Sohlst Ingenlka Group 56°23 , N. 125°21.5'W. GSC Paper 7 1 - 2 , pp. 11 -12 • See reference. 136. TABLE D-l (oont'd) Published K-Ar ages referred to In this report. Beport Referenoe Age No. Number and In m.y. Mineral Dated Rook Type Unit Looatlon Reference 81 CSC66-18 Hb 82 GSC66-19 Bio POLARIS ULTRAMAFIC COMPLEX, NORTHERN B.C. 152±15 l64±9 Peridotite Polaris S6°Z6'H. Ultramaflo 125°35'W. Complex GSC Paper 67-2A, p. 21-22 8 3 GSC?0-48 Huso CASSIAR BATHOLITH 1 8?+4 Granodiorite Cassiar 69°04,47"N. GSC Paper 71-2. pp. 30-31* (cataclastlo) Batholith 130°49*35"W. 8 4 GSC61-45 Bio 126 8 5 GSC60-30 Bio 98 MARKER LAKE BATHOLITH Granodiorite Marker Lake 6o°33'N. Batholith 130°57'W. Schist east of 60°37'N. Harker Lake 130°47*W. Batholith GSC Paper 62-17, p. 28 GSC Paper 61-17, P . 17-18 8 6 GSC60-29 Bio 6 6 Granodiorite unnamed stock * 6l°07'N. 130°51'W. GSC Paper 61-17, P. 17 87 G S C 6 6-60 Hb 88 G S C 5 9-9 Huso 89 GSC59-11 Bio 90 GSC61-41 Bio 91 GSC61-42 Muso AGES SOUTHWEST OP TINTINA TRENCH, YUKON TERRITORY (NASINA SERIES, YUKON GROUP, BRICK CREEK SCHIST) 199+34 Granitic Laberge cobble i n Group conglom. 214 140 147 222 Schist Schist Schist Schist Yukon Group Yukon Group Yukon Group 6l°37'N. 135653'W. 60-6l°N. 132-134°W. 6l 017'N. 138°07'W. 6l°l4'N. 136°57'W. GSC Paper 67-2A, pp. 55-56 GSC Paper 60-17, p. 7 GSC Paper 60-17. p.8 GSC Paper 62-17, PP. 25-26 60°00'30"N. GSC Paper 62-17, PP. 26-27 132°08'20"W. 92 GSC60-33 Muse 138 93 GSC61-40 Muse 175 KLONDIKE SCHIST Schist Schist Klondike schist Kondike schist 63054'N. 138°52'W. 64°07'N. 140°48*W. GSC Paper 61-17, p. 19 GSC Paper 62-17, P. 25 94 GSC62-82 Bio 95 GSC64-24 96 GSC 64-25 97 GSC64-26 98 GSC64-27 Bio Hb Muso Bio 202 187 161 178 182 FELLY GNEISS Granodiorite P e l l y gneiss Gneiss Granitic gneiss Pelly gneiss Pelly gneiss 64°02'00"N. 140°23'20"W. 62°53i'N. 138°51'W. 63°o6,45"N. 139°29'30"W. GSC Paper 63-17, pp. 53-54 GSC Paper 65-17, p. 22 GSC Paper 65-I7, pp. 23-25 * Bee reference, 1 This sample Is not Included i n mean age since Poole (1972) considers the age to be young. 137. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Report Referenoe Age Ko. Number and In m.y. Mineral Dated Rook Type Unit Looatlon Referenoe 99 GSC59-10 Bio 223 100 GSC59-12 Bio 176 101 C S C 5 9-13 Bio 58 102 GSC60-31 Bio 65 103 GSC60-32 Bio 58 GRANITIC ROCKS Granodiorite * 60°53*N. 135°33'W. 6l°21'N. 138°03'W. 6l°25'N. 138°45'W. Quartz Ruby Range 6l°05'N. monzonite Batholith 136°59'W. Granodiorite Ruby Range 6l°01'N. Batholith 138°08'W. Quartz * monzonite Granodiorite Yukon Group GSC Paper 6o-17t PP. 7-8 GSC Paper 60-17, PP. 8-9 GSC Paper 60-17, p. 9 GSC Paper 61-17, pp. 18-19 GSC Paper 61-17, pp. 18-19 104 GSC65-34 Bio 105 GSC65 -35 Bio 106 GSC65-36 Bio NORTH-BIG SALMON RIVER CRYSTALLINE BELT 90±6 90±6 91±5 Quartz Big Salmon 6 l°35 '30"N. monzonite R. Crystal- 133°26'30 ,, W. line Belt 6l°46'N. 1 3 3 ° 2 6 ' 3 0 " W . Granite Schist 107 GSC65-37 Amphibole83±26 Gneiss 6l°40'N. 133°20'W. 6l°4l'N. 133016'w. GSC Paper 6 6 - 1 7 , pp. 35-36 GSC Paper 6 6 - 1 7 , PP. 35-36 GSC Paper 6 6 - 1 7 , pp. 36*37 GSC Paper 6 6 - 1 7 , pp. 37-38 108 CP-25-69 109 CP-2-69 110 GSC67-45 Hb Bio CANADIAN CREEK, YUKON TERRITORY (CASINO DEPOSIT) 69±3 Porphyritic « 62°43'N. daoite 138°49'W. Phillips and Godwin, 1970, P. 3 71±3 Porphyritic • 62 0 43'N. 138°49'W. dacite 99+6 Granodiorite 95+5 62°42.9'N. GSC Paper 69-2A, p. 27 138°50.8'W. SELHYN BASIN NEAR YUKON TERRITORY - MACKENZIE TERRITORY BOUNDARY 111 GSC67-65 Hb 80±5 112 GSC67-66 Bio 87±4 113 GSC67-49 Bio 88±4 114 GSC62-88 Bio 110 115 AK 125 Bio 96 116 AK 107 Bio 94 117 CSC65 - 4 5 Bio 99±5 Quartz monzonite Schist 62°51'25"N. GSC Paper 69-2A, p. 37 128°49'30"tf. 6l°39'40"N. GSC Paper 69-2A, pp. 28-29 T?RO-»)Lion"u. 128°34'00 W Quartz Pyramid 6 l o 5 3 ' 0 3"N. GSC Paper 6 3 - 1 7 , p. 58 monzonite Mtn. stock 127°58'52"W. Granodiorite Itsl 65°55'N. Mountains 130°10'W. Pluton Quartz Nahannl monzonite Schist • 62°05'N. 6l°23'N. 130°33'W. Baadsgaard et al., 1961 a and b Baadsgaard et al., 1 9 6 l b , pp. 4 5 8 - 4 6 5 GSC Paper 6 6 - 1 7 , pp. 4 3 - 4 4 • See referenoe. 1 3 8 . TABLE D-l (oont'd) Published K-Ar ages referred to In this report. Report R e f e r e n o e A g e No. Number and In m.y.- Mineral Dated Rook Type Unit Location Reference 118 GSC63-15 Bio 265±12 119 AK 108 220 120 GSC63-15 Bio 370±l6 121 AK 51 Bio 353 122 GSC63-I6 Hb 355 123 AK 110 Bio 95 (ohlorltic) 124 GSC65-51 Whole R 237+47 125 AK 105 Whole R 312 NORTHERN YUKON TERRITORY 67°42'N. 140°42'W. 67°44>N. 139°50'W. Porphyrltio Mount 67°42'N. granite Fllton stock 140°42'W. Porphyrltio Old Crow granite Batholith Old Crow Batholith Quartz " monzonite Porphyritic Mount granite Sedgwick stock 68°30'N. 138°01 , W. 68°55'N. 139°07'W. Porphyrltio granite Basalt Syenite dike GSC Paper 6 4 - 1 7 (Part 1), p. 22 Baadsgaard et al., 1961b, pp. 458-465 GSC Paper 64-17 (Parti), P. 22-23 Baadsgaard, et al., 196la, pp. 689-702 GSC Paper 64-17 (Part 1), P. 23 68051'N. 139°07*W. 69°01 , N. 141°05'W. 65°19'N. 130°48'W. ( D . of Mackenzie) Baadsgaard et al., 1961b, pp. 458-465 GSC Paper 66-17, P. 49 Baadsgaard et al., 196lb, pp. 458-465 KENO. HILL AREA, YUKON TERRITORY 126 GSC65-46 Muse 84±8 Schist Yukon Group 63°55'15"N. 135°26'W. (Galena Hill) GSC Paper 66-17, P. 44 127 GSC65-47 Muse 93±12 Schist Yukon Group 64°11'N. 135°21'30"W. GSC Paper 66-17, P. *5 128 GSC65-48 Huso 101±6 Schist Yukon Group 63°47'30"N. 135°4l'45"w. GSC Paper 66-17, PP . 45-46 129 GSC70-4? Muso 64±3 70±3 Schist Yukon Group 63023'N. 136°40 , W. GSC Paper 71-2. ] P. : 29 130 GSC65-49 Bio 81±5 Quartz porphyry * 63°51'05"N. 135°51'20"W. GSC Paper 66-17, P. 47 131 GSC65-50 Bio 85+7 Quartz monzonite • 63°29'N. 136 0 58'W. GSC Paper 66-17, pp . 47-48 132 GSC62-78 Bio 102 Quartz monzonite * 64°01'50"N. 135°25'50*W. GSC Paper 63-17. P. 51 133 GSC62-8O Bio 106 Granodiorite • 64°02'N. 135°50«w. GSC Paper 63-17, p. 52 134 GSC62-81 Bio 81 Porphyrltio • quartz diorite 63°53*55*N. 134°46,i5-w. GSC Paper 63-17, PP . 52-53 135 GSC66-58 Bio 136 GSC66-59 Hb 137 GSC62-79 Bio TOMBSTONE STOCK (SIMILAR AGE BODIES) NORTH OF TINTINA TRENCH, YUKON TERRITORY 91±5 Quartz Tombstone 64°27"13"N. GSC Paper 67-2A, pp. 54-55 80±13 monzonite stock 138°33'00"W. 134 Blo- feldspar porphyry 64°09*25"N. GSC Paper 63-17, p. 51 137°40'00"W. • flee reference. 139. TABLE (oont'd) Published K-Ar ages referred to In this report, D-l Report Referenoe No, Number and Mineral Dated Ago In m.y. Rook Type Unit Location Referenoe ANVIL AREA, YUKON TERRITORY 138 GSC61 -43 Bio 100 Porphyritic daoite • 62°31'N, 131°51'W. GSC Paper 62-17, P. 27 139 GSC61-44 Bio 117 Porphyritic daoite • 62°27>N. 132°18'W. GSC Paper 62-17, P. 27 140 GSC65-44 Bio 86+6 Daoite Tay Formation 62°15'30"N. 132°03 ,30"W, GSC Paper 65-17, PP . 42-43 MOUNT SELOUS PLUTON 141 GSC65-38 Bio 83+7 Quartz monzonite Mount Selous Pluton 62°57*N. 132&30'W. GSC Paper 66-17, P. 38 142 GSC65-39 Bio 81±10 Granodiorite w 62°54'N. . 132 D 27'W. GSC Paper 66-17, P. 9 143 GSC65-4O Bio 74+7 Quartz monzonite • 62°56'N. 132°27*W. GSC Paper 66-17, PP . 38-40 144 GSC65-41 Bio 90+5 Quartz monzonite Anvil Batholith 62°27'N. 133O27 ,30"W. GSC Paper 66 -17 , P. 40 145 146 GSC65-42 GSC65-43 Muso Bio 79+6 87+5 Quartz monzonite Anvil Batholith 62°17'N. 133°03'W. GSC Paper 66 -17 , PP . 40-42 147 148 GSC 67 GSC67-48 Muse Bio 99+5 93+4 Schist thermal metamorphosed contact zone 62°22'N. 133023'W. GSC Paper 69-2A, PP . 27-28 149 150 GSC70 -45 GSC70-46 Huso Bio 94+5 94±5 Granodiorite (sheared) Anvil Batholith 62°17 .5'N. 133°l6.5'W. GSC Paper 71-2, ; PP. 28-29 INSULAR BELT (51°-56°N.) - • QUEEN CHARLOTTE. ISLANDS, B.C. JURASSIC AGES (SYNTECT0NIC AND POST-TECTONIC?) 151 GSC70 -1 Hb I 43 t8 Granodiorite (gneissic) Kano Batholith 53°17.5'N. 132°38.5'W. GSC Paper 71-2, P. 6 152 153 GSC67 -20 GSC70-3 Hb Hb 142*14 Quartz diorite I56+IO Quartz diorite San Chrlstoval Batholith Chlnukudl Pluton 52°34,30"N. 131 5 40'W. 53°19'N. 131°58'W. GSC Paper 69-2A, GSC Paper 71-2, P. P. 13 7 154 GSC66-14 Hb 142±37 Granodiorite Burnaby Island Pluton 52°22*N. 131°15'W. GSC Paper 67-2A, P. 19 MID-TERTIARY (POST-TECTONIC) 155 GSC70-2 Bio 30±3 Granodiorite Central Kano Batholith 53°13'N. 132°29'W. GSC Paper 71-2, PP. 6-7 156 157 GSC67 -16 GSC67-17 Hb Dlo 26±6 29±2 Granodiorite n 5 3 ° 1 7 ' N ' 132°26'W. GSC Paper 69 -2A, PP . 11-12 158 159 GSC67-18 GSC67-19 Hb Bio 38±2 39±2 Granite Pocket Batholith 52°34'N. 131 0 48'W. GSC Paper 69 -2A, PP . 12-13 160 AK 378 Bio TERTIARY ACIDIC VOLCANIC ROCKS 62±3 Porphyry Massett 53°24.2' sill(?) formation 132°23 .1 ' Mathews, 1 9 6 4 , pp. 4 6 5 - 4 6 8 * See referenoe. 140. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Beport Referenoe No. Number and Mineral Dated Age in m.y. Rock Type Unit Location Reference COAST CRYSTALLINE BELT OF BRITISH COLUMBIA BETWEEN LATITUDES 52.°N to 56°N 161 162 GSC66-11 GSC66-12 Hb Bio 133+22 139+7 Quartz d i o r i t e * 53°09*N 129°35'W. GSC Paper 67-2A, P. 16 163 GSC67-24 Bio 104±4 Quartz di o r i t e 53°15'N. 129°35'W. GSC Paper 69-2A, P. 15 1 6 4 GSC67-23 Bio 115±6 Quartz monzonite 53 o 03'N 129°27*w. GSC Paper 69-2A, PP. 14-15 165 166 GSC64-5 GSC64-6 Bio 103+.6 111+6 Granodiorite » 53 0 3l'N. 130°01*W. GSC Paper 65-17, PP. 10-11 1 6 7 1 6 8 GSC66-17 GSC66-16 Bio Hb • 88±5 87±11 Granodiorite * 52°34'N. 128 6 4l'W. GSC Paper 67-2A, P. 20 I69 GSC67-21 Bio 84±4 Granodiorite Melville I s l . stock 54°24'N. 130°44'W.. GSC Paper 69-2A, pp. 13-14 1 7 0 1 7 1 GSC66-4 GSC 66-5 Bio Hb 96+5 101+15 Granodiorite • 54°29'N. 130°57*W. GSC Paper 67-2A, P. 12 172 GSC67-26 Bio 109+5 Granodiorite • 52°45« 30"N. 129°22'30"«. GSC Paper 69-2A, PP. 16-17 173 176 GSC67-27 GSC67-28 Hb Bio 100+6 90±4 Gabbro • 52°06'30"N. 128°17'00"W. GSC Paper 69-2A, P. J 7 175 176 GSC67-29 GSC67-30 Hb Bio 87±5 81±4 Andeslte * 52o13'00"N. 127°50'30"w. GSC Paper 69-2A, PP. 17-18 177 GSC64-11 Bio 67+5 Quartz d i o r i t e » 53°28'N. 128°51'W. GSC Paper 65-17. pp. 13-14 1 7 8 1 7 9 GSC66-13 GSC 66-12 Bio Hb 70±4 87+15 Granodiorite E c s t a l l Pluton 53°4l'N. 129°30'W. GSC Paper 67-2A, P. 17-18 1 8 0 1 8 1 GSC67-33 GSC67-34 Hb Bio 79+5 75+5 Granodiorite « . 52°10'N. 128 o 00'W. GSC Paper 69-2A, PP. 20-21 1 8 2 GSC65-31 Bio 64±8 Quartz d i o r i t e • 54°13'N. 130°O4'W. GSC Paper 66-17, PP. 32-33 I83 GSC64-8 Bio -.{-4+14, me .77+5 sh) Quartz d i o r i t e » 52°32*N. 128 6 02 ' W . GSC Paper 65-17, P. 1 1 1 8 4 G S C 6 4 - 7 Bio 77+5 (-100+150. mesh)" Quartz d i o r i t e * 52°32"N. ^ooi'SS'w. GSC Paper 65-17, PP. 11-12 1 8 5 G S C 6 7-25 Bio 49±4 Quartz d i o r i t e * 53°l6'N. 128°l6 ' W . GSC Paper 69-2A, P. 16 1 8 6 GSC64-12 Bio 48±5 Bi o t i t e schist * 53°38'N. 128°52'W. GSC Paper 65-17, P. 14 I87 GSC66-15 Bio 47± 4 Granodiorite * 54°54'N. 129°25'W. GSC Paper 67-2A, pp. 19-20 1 8 8 1 8 9 G S C 6 6 - 9 G S C 6 6-8 Bio Hb 44±5 49±7 Quartz d i o r i t e Quottoon Pluton 54°35'N. l30 o ll'W. GSC Paper 67-2A, P. 15 190 1 9 1 GSC66-6 GSC66-7 Bio Hb 50±5 48t9 Quartz d i o r i t e Quottoon Pluton 54°21 , N. 129°52'W. GSC Paper 67-2A, PP. 13-14 192 GSC65-29 Bio 43*5 Quartz d i o r i t e • • 54 0 17«N. GSC Paper 66-17, PP. 30-31 193 CSC65-30 Bio 44±4 Granodiorite A l a s t a i r . Lake Pluton 54°05'N. 129°01'W. GSC Paper 66-17, PP. 31-32 1 9 4 GSC65-32 Bio 46±10 Granodiorite • 54°38 , H. 129°02 ' W . GSC Paper 66-17, PP. 33-34 * See reference. 1 4 1 . TABLE (cont'd) Published K-Ar ages referred to In this report. D-l Report Reference Age No. Number and In m.y. Mineral gated. Rook Type Unit Looatlon Reference 195 GSC64-9 Bio 45+12 196 GSC65-19 Bio 47±5 197 GSC65-28 Bio 70±14 198 GSC64-10 Bio 57+6 199 GSC66-20 Muso 51±6 200 NC67-8 Bio 54±3 201 NC67-12 Whole R 53±3 202 NC67-IO Bio 48±2 203 NC67-9 Bio 44+2 204 GSC67-22 Bio 37+2 205 GSC67-3I Whole E 14.5±1 206 GSC67-32 Whole R 12.5±2. 207 NC67-15 Bio 179±8 Quartz monzonite Granodiorite Labouohere Pluton Granodiorite War Drum Pluton Quartz monzonite Quartz monzonite Labouohere Pluton 55°13'N. 129°51'W. 52°49'N. 126°38'W. 52°07'N. 126°18'W. 127°l4'W. 52°25'N. 127°l4'W. BERG "Cu-Mo" PROPERTY 208 Serb Creek Bio 4l±3 Quartz diorite Hornfels Quartz monzonite (porphyry) Latite por- phyry dike Pegmatite Gabbro 7 Diabase Granodiorite Porphyritic Quartz monzonite 5 3 r, 127° GSC Paper 65-17, p. 12 GSC Paper 66-17, P. 23 GSC Paper 66-17, p. 30 GSC Paper 65-17, p. 13 GSC Paper 67-2A, pp. 22-23 White, Harakal and Carter (1968) 53°47'N. 129°02'W. GSC Paper 69-2A, p. 14 52^09.'15"N. GSC Paper 69-2A, p. 18 GSC Paper 69-2A, pp. 19-20 128°04'00"W. 52°12'15"N. 128°08'00"W. Luoky Ship (54°N, 127°W. 54°N. 127°W.  N , W * White, Harakal and Carter ) (1968) Amax Expl. Ltd., Det. by Geochron Labs., Inc. 209 AK23 Bio 163 210 GSC61-34 Bio 63 211 GSC61-35 Bio 178 212 GSC6I-36 Bio 138 213 GSC61-37 Bio 154 INTERMONTANE BELT 52° - 56°N. TOPLEY INTRUSIONS (see Table ) Granite Topley Diorite « (non-follcated) Diorite Granite Granite Topley Topley Topley 54°04'N. 124°4l'W. 53°42'N. 124°02'W. 54°31'N. 124652'W. 54°05'N. 125002'W. 54°02'N. 125°02'W. Baadsgaard et a l . , 196la GSC Paper 62-17, P. 21 GSC Paper 62-17, P. 22 GSC Paper 62-17. P. 22 GSC Paper 62-17, P. 22 GLACIER GULCH MOLYBDENUM DEPOSIT - SMITHS RS • B. C. 214 GSC67-35 Bio 67t5 Quartz monzonite (porphyry) 215 GSC67-36 Bio 60±5 Quartz latite (porphyry) 54°49'30"N. GSC Paper 69-2A, p. 21 127°18'W. 2,782-2,851' DDH28 54°49'30"N. GSC Paper 69-2A, p. 22 127°18'W. * See referenoe. 142. TABIE (cont'd) Published K-Ar ages referred to in this report, D-l Report Reference Age No, Number and In m.y. Mineral Dated Rook Type Unit Location Referenoe 216 GSC6?-37 Bio 63±4 217 GSC67-38 Hb 65+6 218 NC67-41 Bio 69±3 Qtz-Bio veinlets Qtz-Hb- Sulphlde veinlets Bio in quartz molybdenum seam 54°49'30"N. GSC Paper 69-2A, pp. 22-23 127°18'W. 54°49'30"N. GSC Paper 69-2A, p. 23 127°18'W. White et a l . , 1968 219 BM65-1 Bio 105+4 220 BM65-3 Bio 98+4 221 B M 6 5 - 4 Bio 104±4 B0S3 MOUNTAIN MINE, B. C « Quartz diorite Altered dike Dike fragment In breccia ore 5045 Level White et a l . , 1968 White et a l . , 1968 White et a l . , 1968 TAKOMKANE BATHOLITH - CARIBOO DISTRICT, B. C. 222 GSC62-64 Bio I87 Granodiorite Takomkane 52°06 , 00"N. GSC Paper 63-I7, p. 42 Batholith 120°55'03"W. 223 AK302 Bio 53+2 224 AK395 Bio 48+2 CENOZOIC VOLCANIC ROCKS Daclte T-Allln Endako Group 54°03.5"N. 125057.1"W. 54°07.3'N. 125°19.0'W. Mathews, 1964, pp. 465- 468 225 NC69-6 226 NC69-7 227 GSC70-40 Bio 228 GSC70-41 Muso 229 GSC70-43 Muso 230 GSC70-42 Bio 231 GSC70-44 Bio 232 GSC70-37 Muso 233 GSC70-38 Muso SAM GOOSLEY PROPERTY, CENTRAL B.C 56.2±3 Biotite granitic stook 48.8±3 Syenomonzonite • 44*4 4 6 ± 3 4 0 ± 2 43±4 45±2 45±3 50± 6 54°11'N. 126oi6'W. 54°11'N. 126°l6'W. Church 1970, (G.E.M.) pp. 119-125 OMINECA BELT 52Q - S6° WOLVERINE METAMORPHIC COMPLEX Gneiss Wolverine 55°07'35"N. GSC Paper 71-2. pp. 23-24 Complex 123029'15"W. Gneiss Granite grelsen Gneiss Wolverine 55°07'35"N. GSC Paper 71-2, p. 24 Complex 123°29'15"W. Wolverine 55°07'35"N. GSC Paper 71-2, PP. 24-25 Complex 123°29'15"W. Wolverine 55°32'10"N. GSC Paper 71-2, p. 24 Complex 123°52'40"W. Amphibolite Wolverine 55°32'10"N. Complex 123°52'40"W. GSC Paper 71-2, p. 25 Schist Wolverine 55°23'30"N. GSC Paper 71-2, p. 22 Complex 123°39'50"W. Pegmatltlo Wolverine 55°23'30"N. granite Complex 123°39'50"W. GSC Paper 71-2, p. 23 * See referenoe. 143. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Report Referenoe Ago No. Number and In m.y. Rook Type Unit Looatlon Referenoe Mineral Dated ; 234 GSC70-39 Muso 47±3 Gneiss Wolverine Complex 55°19'N. 123O30'W. GSC Paper 71-2, P. 23 235 236 GSC61-31 GSC61-32 Muso Bio 75 77 Sohist Wolverine Complex 55°23'30"N. 123°39*50"W. * GSC Paper 62-17, P. 19-20 237 GSC61-30 Bio 69 Gneiss Wolverine Complex 55°33'N. 123°56'w. GSC Paper 62-17, P. 19 238 GSC61-33 Muso 71 Gneiss Wolverine Complex 55°19'N. 123°30'W. GSC Paper 62-17, P. 20-21 239 GSC60-23 Muso 22 Pegmatitlo granite • 55°24'N. 123°39'W. GSC Paper 61-17, P. 14 240 GSC60-24 Bio 29 Marble * 55°27'N. 123°34'W. GSC Paper 61-17, P. 14 241 GSC62-67 Bio 78 Granite • 55°5'20"N. 123°18'50"W. GSC Paper 63-17, PP . 43-44 MALTON COMPLEX 242 243 GSC70-16 GSC70-17 Muse Bio 60±3 66±3 chips of gneiss and schist Malton gneiss 55°25*N. 118°42'W. GSC Paper 71-2, P. 13 244 GSC70-18 Bio 57±3 Granite Malton gneiss 52°22.5'N. U8°38.5'W. GSC Paper 71-2, P. 13-14 245 GSC67-43 Bio 53±4 59±5 Gneiss Malton gneiss 52°36'00"N. 119°01'20"W. GSC Paper 69-2A, P. 25 246 GSC67-44 Hb H4tl2 m « ta GSC Paper 69-2A, P. 26 24? GSC65-24 Bio 72+5 Gneiss » 52°38'N. 118°59'W. GSC Paper 66-17, PP . 26-27 248 GSC67-40 Bio 36+3 Quartz diorite • 54°06'N. GSC Paper 69-2A, P. 24 249 GSC67-41 Bio 93±4 Quartz monzonite • 53°38'N. 122°38*W. GSC Paper 69-2A, PP . 24-25 MISINCHTKKA SCHIST 250 251 GSC62-65 GSC62-66 Bio Muso 143 136 Sohist Misinchlnka 55°10'49"N. schist 122°45'55"W. GSC Paper 63-17. PP . 42-43 PRINCE GEORGE QUESNEL AREA* 252 GSC66-21 Bio 105±6 Granite boulder * 53°42'N. 122°4l'W. GSC Paper 67-2A, PP . 23-24 253 G3C66-22 Bio 98t5 Quartz monzonite • 53°41'N. 122°4l'W. GSC Paper 67-2A, PP . 23-24 254 GSC66-23 Bio 104±5 Quartz monzonite • 53°18'N. 122°22'W. GSC Paper 67-2A, P. 24 255 GSC66-24 Bio 107±6 Quartz monzonite • 53°25'N. 122°l4'W. GSC Paper 67-2A, P. 24-25 256 GSC66-25 Hb 176+20 Granite • 53°44'N. 122°20'W. GSC Paper 67-2A, PP . 25-26 257 GSC66-26 Bio 106±6 Granodiorite * 52°04'N. 122°35'W. GSC Paper 67-2A, P. 26 • See referenoe. 144. TABLE (oont'd) Published K-Ar ages referred to in this report. 0-1 Report Referenoe Age No. Number and in m.y. Rook Type Unit Looatlon Referenoe mineral,. Pat so. MIETTE GROUP 258 GSC66-47 Bio 111±5 Quartzose Hiette 52°32'34"N. GSC Paper 67-2A, pp. 43-44 phylllte Group llS^l'Se-W. KAZA GROUP 259 GSC64-4 Muso 85+15 Granite Kaza pegmatite Group 52°54'N. l^^l'W. GSC Paper 65-I7, p. 9 260 G S C 6 4-13 Bio 51±6 261 GSC64-14 Huso 5 4 ± 6 CARIBOO GROUP Quartz Cariboo 5 2 ° 2 1 , 4 0 " N . GSC Paper 65-I7, pp. 15-16 monzonite Group 1 1 9 ° 3 9 ' 0 0 " W . 262 GSC63-6 Bio 1 4 3 ± 1 4 Granodiorite * 52°34 ,00"N. GSC Paper 64-17, Part 1, 120°02'30"W. pp. 15-16 INSULAR BELT - VANCOUVER ISLAND 263 K-Ar-1652 Phlogo-181±8 Skarn p i t e 1 7 8 ± 8 Empire Dev.& Carson et al., 1971 Coast Copper BRYNNOR MINE 264 GSC 64-2 Bio 167+10 Granodiorite * 265 GSC64-3 Bio 121±35 Feldspar * porphyry 266 K-Ar-1716 Bio 47+3 (GSC70-1716) dyke 49o03«N. 125°25'W. 49°03'N. 125026'W. GSC Paper 65-17, PP. 7-8 GSC Paper 65-17, pp. 8-9 Carson et al., 1971 267 GSC65-I8 Bio 166±8 268 GSC65-17 Bio 162±9 UCONA BATHOLITH Granodiorite Ucona 49°43'30"N. Batholith 125°56'25"W. Granodiorite Ucona 49°49'15"N. Batholith 125°58«25"W. GSC Paper 66-17, P. 22 GSC Paper 66-17, P. 21 NIMPKISH IRON MINE 269 G S C 6 5 - 1 4 Bio 270 G 3 C 6 5 - 1 5 Hb 271 G S C 6 6-27 Bio 151±l4 Granodiorite Nlmpklsh 50°l6'35"N. GSC Paper 66-17, pp. 18-20 l43±60 Batholith 126°51'21"W. 150±8 152±7 Quartz monzonite Nlmpklsh 50o22'15"N. GSC Paper 6?-2A, p. 27 Batholith 126°45'40"W. 272 GSC66-28 Phlogo-l48±8 Skarn plte ZEBALLOS IRON MINE » 50o02'58"N. GSC Paper 67-2A, p. 28 126°49'56"W. 273 K-Ar-1698 Hb TEXADA MINES I65+9 Granodiorite Gllles stock 4 9 ° 4 2 ' N . 1 2 4 ° 3 3 ' H . Carson et al., 1971 * See referenoe. 145. TABLE (cont'd) Published K-Ar ages referred to In this report, D-l Report Referenoe Age No. Number and In m.y. tUnera!, gated Rock Type Unit Location Referenoe- 2 ? 4 GSC67-39 Bio 120±6 275 K-Ar-15*H(2) Bio 110+5 276 K-AT-1541A Hb Il4il5 277 K-Ar-1778A Bio 111+6 2 7 8 K-Ar-1778 Bio 106±4 279 K-Ar-1?77 Hb 155+8 Granodiorite Pocahontas 49°43'25"N. GSC Paper 69-2A, pp. 23 - 2 4 Stock 124°24'30"W. Granodiorite Pocahontas Stock Granodiorite East Stook Carson et al., 1971 Carson et al., 1971 2 8 0 G S C 6 6 - 3 3 Bio 160+8 2 8 1 GSC66-34 Whole R 163*20 282 GSC65-II Bio 48+.12 2 8 3 GSC66-31 Bio 50+5 2 8 4 GSC66-32 Bio 5 9 + 3 285 GSC70-36. , Hb. 44±6 286 GSC65-13 Bio 39+10 287 GSC65-12 Bio 3 8 ± 4 288 GSC66-29 Bio 39*7 289 GSC66-30 Bio 35+6 290 GSC69-I653 Bio 38+2 Granodiorite Sohist Quartz diorite Sicker Group Catfaoe Stook Granodiorite Quartz monzonite Orebody Quartz diorite Quartz diorite Quartz diorite Quartz diorite Quartz diorite 49°05'15"N. 124°l6'15"W. 48°52'00"N. 123°47'30"W. (Twin J) 49 0 l4'35"N. 125°57'00"W. (Catface) 49 o 09'25"N. 125°55'30"W. 49°oi'25"N. 125029'10"W. (Brynnor Mine)* 48°27'N. . 124°03'W. (Sunro Mine) 48°26'55"N. 124°00'00"W. (Faith Lake) Zeballos 50°02'07"N. Batholith 126°47*04"W. GSC Paper GSC Paper GSC Paper GSC Paper GSC Paper 67-2A, pp. 32-33 67-2A, pp. 33-34 66- 1 7 , P. 15 67- 2A, pp. 30-31 67-2A, pp. 31-32 GSC Paper 71-2, p. 22 GSC Paper 66-17, PP. 17-18 49°39'12"N. 125°24'4l"W. (Forbidden Plateau) GSC Paper GSC Paper 66-17, PP. 16-17 67T2A, P. 29 Mount 4 9 ° 4 6 ' 0 4 " N . GSC Paper Washington 125°17 '24"W. stook (Mt. Washington Mine) 49 cr 01'N. 1 2 4 ° 3 9'W. (Corrlgan Creek) 67-2A, pp. 29-30 Carson, D.J., I969, p. 518 291 10 292 11 293 12 2 9 4 13 295 1 4 296 15 COAST CRYSTALLINE BELT AND CASCADE MOUNTAINS CHILLIWACK BATHOLITH Gabbro 49° - S2°N. Bio 29tl Bio 28±1 Bio 26±1 Bio 26+.1 Bio 26tl Mafic 24+.1 cono. Quartz diorite Quartz monzonite Quartz monzonite Quartz monzonite Quartz diorite Chllliwack 49°03'N. Batholith 121°19'W. 49°05'N. 121<>26'W. 49°06'N. 121°27'W. 49°02*N. 121°23'W. " 49°02'N. 121°23'W. Williams • Peak Stock Richards & White, 1970, p. 1206 * See referenoe. 146. TABLE (cont'd) Published K-Ar ages referred to In this report. D-l Report Referenoe Age  : No. Number and In m.y. Rook Type Unit Looatlon Referenoe Mineral Dated 297 16a b Bio Bio 24±1 24+.1 Quartz d i o r i t e Hioks Stock Rlohards & White, 1970, p. 1206 298 17 Bio 21±1 Granophyre Mount Barr Batholith 49°19'N. 121°27'W. m 299 18 Bio 18_1 Grano d i o r i t e Mount Barr Batholith 49°l4'N. 121°35'W. M 300 19 Bio 16+1 Quartz monzonite Mount Barr Batholith 49°15'N. 121°33'W. 301 AK-31 Bio 18 Quartz d i o r i t e Mount Barr Batholith 49°15*N. 121°40'W. Baadsgaard, I96I 302 AK-45 Bio 18 Quartz d i o r i t e Mount Barr Batholith, 49°l4'N. 121°4o'W. 303 Bio 32 Chllliwack Batholith 48°38'N. 121°21'W. UBC Guidebook, 1968 304 Bio 23 Granodiorite * 49°20'N. 121°38'W. Richards, 1971 305 20 Quartz d i o r i t e Cascade Pass stock 49°30'N. 121°02'W. Misch, 1966 306 GSC65-8 Bio 39+4 Granite * 49°30'30"N. 121°10'W. GSC Paper 66-17, p. 11 307 GSC65-26 Bio 40±5 Daoite • 51°23'N. 120°58'W. GSC Paper 66-17, P . 28 HELL'S GATE STOCK 308 AK-24 Bio 35 Granodiorite Hell's Gate 49°47'N. 121°27'W. Baadsgaard, 1961 309 GSC70-1736 Hb 40 Hell's Gate 49°46'N. 121°26'W. reported by Richards, 1< HOPE PLUTONIC COMPLEX 310 9 Hb 35±2 Quartz d i o r i t e S l i v e r Creek Stock 49°23'N. 121°20'W. Richards & White, 1970, p. 1206 VATJI INTRUSIONS 311 8 Bio 35+2 Quartz d i o r i t e Ogllvle Stock 49°20'N. 121°27'W. Richards & White, 1970, p. 1206 312 7 Bio 4l±2 Quartz monzonite Coqulhalla Stock 49°22'N. 121°22'W. « 313 4a b Bio Bio 59+3 59±3 Granodiorite -Berkey Creek 49°19'N. 121°21'W. H CUSTER RIDGE MICA-HORNBLENDE PERIDOTITE 314 6 Hb 44±3 Hbite Skagit Mica Perldotite 49°01'N. 121°18'W. Richards .& White, 1970, p. 1206 315 GSC70-1737 Bio 44 49°46'N. 121°26'W. •See referenoe. 147. TABLE (oont'd) Published K-Ar ages referred to in this report. D - l Report Referenoe Age No. Number and in m.y. Rook Type Unit Location Reference Mineral Dated 316 GSC70-1728 Bio 70 4 9°50'N. 121°4l 'W. unpublished 317 GSC70-1731 Hb 72 49°55'N. 12l°34'W. a 318 GSC?0-1734 Hb 73 49°4l'N. 121°29'W. •t 319 GSC70-1735 Bio 74 49°4l'N. 121°29 'W. a 320 321 ' Hb Bio 80 80 Quartz diorite • 4 9°23'N. 121°28'W. Richards, 1971 322 Bio 82 Quartz diorite • 49°22'N. 121°29'W. Richards, 1971 323 GSC65-10 Bio 84±6 Granodiorite Dewdney Creek Group 49°12'N. 121°05 'W. GSC Paper 6 6 - 1 7 , PP. 13- 324 GSC65-9 Bio 98±6 Granodiorite * 4 9 ° l 6 ' 4 5 " N . 120°46'W. GSC Paper 66-1?, pp. 12- 325 Bio 92 Granodiorite 49°14'N. 123°08'H. White, 1968 326 Bio 95 Quartz diorite * 49°5l'N. 123 & 11'W. m 327 Hb 97 Quartz diorite • 49°43'N. 123°06'W. a 328 KA-126 Bio 9 7 Granodiorite * 49°22'N. 123°l6«W. Baadsgaard, 1961 329 Bio 102 Quartz diorite • 49 0 21'N. 12l°34'w. Richards, 1971 330 GSC66-47 Bio 111±5 Quartzose Phylllte Hlette Group 52°32'34"N. 118°4l'56"W. GSC Paper 67-2A, p. kj-i 331 Bio 158 Quartz diorite 49°54'N. 123D07'W. White, 1968 SPUZZUM INTRUSIONS 332 la b Bio Bio 103±5 103±5 Quartz diorite Richards &. White, 1970, p. 1206 333 2a Bio 79+4 Quartz diorite • a 334 3 Bio 77±3 Quartz diorite • a 335 336 • • Hb Bio 76 76 Quartz diorite 4 9°36'N. 121°27'W. McTaggart & Thompson, (1967) 337 Bio 253 * Oroas Island 48°39'N. 12  6 01'W. UBC Guidebook, 1968 338 Whole R 258 • Vedder Mountain 49°04'N. 122°03'W. Ross in UBC Guidebook, 1968 • See referenoe. 148. TABUS (oont'd) Published D-l K-Ar ages referred to i n this report. Report Hel'eronoe Ho. Number and Mineral Dated Age i n m.y. Rook Type Unit Looatlon Reference INTERMONTANE BELT - •52° - 49° TERTIARY AGES 339 AK-116 A0±2 Basalt » 50°58.5'N. 120°58.8'W. Mathews, 1964 340 AK-268 12±2 Basalt * 51°54.9*N. 123 0 01.9*M.. * 341 AK-100 13t2 Basalt • 51°53.2'N. 122°49.5'tf. • 342 CSC65-26 Bio 40i5 Daoite • 5l°23'N. 120°58'W. GSC Paper 66-17, pp . 28-29 343 AK-117 Bio 45±2 Trachyte Kamloops Group 50°43'N. 120°49'W. Mathews, 1964 344 Bio 46 Quartz d i o r i t e Castle Peak Stock 48°59*N. 120°52'W. GSC Paper 67-2A, p. 39 345 AK-149 47±2 Breccia Kamloops Group 50°08.3 , N. 119°37.5'W. Mathews, 1964 346 Bio 47 Basalt « 49°29«N. 120°46'W. UBC Guidebook, 1968 (map) 347 AK-99 Bio 48t2 Volcanic ash Princeton Group 49°27*N. 120°32'W. Mathews, 1964 348 Bio 49 Basalt • 50°48'N. 121°10'W. Mathews, 1964 349 AK-118 Bio 49±2 Dolerite Kamloops Group 50°44'N. 12 o°33'w. • 350 Bio 50 » • 49°26'N. 120°30'W. UBC Guidebook, 1968 (map) 351 Bio 50 • 49°14 , N. 120°36'W. rj 352 GSC69-1444 Bio 64 • 51°28°N. 122°58 , «. unpublished 353 AK-625 Andeslne 50 Hornblende- andeslte * Sunday Summit H i l l s £ Baadsgaard, 1967 354 AK-626 Hb 48 Andesite « n - . 355 AK-627 Hb 52 Andeslte • • • 356 AK-628 Bio 50 Ash • KcAbee • 357 AK-629 Andeslne 48 Ash • M • 358 AK-631 Glass • ..shards 22 Bentonite « Qullchena * 359 AK-632 Bio 50 Rhyolite Lava • Allenby 360 AK-633 Andeslne 49 a • H 361 AK-634 Sanldine (fine) 47 L a p l l l l Tuff • Sunday Creek * 362 AK-635 Sanldine (coarse) 50 L a p l l l l Tuff • Sunday Creek 363 AK-636 Andeslne 51 Ash • HcAbee • 364 AK-637 Bio 56 Ash « m * 365 AK-638 Sanldine 56 Ash • m • * See reference. 149. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l R e p o r t R e f e r e n o e A g e No. Number and In m.y, Mineral Dated Rook Type Unit Looatlon Reference 366 AK-640 Ollgo- olase .51 Ash • Battle Bluff Hills 4 Baadsgaard, 367 AK-641 Sanldlne 50 Ash • - • 368 AK-642 Bio 50 Ash - m 369 AK-656 Bio 48 Ash M ft 370 AK-643 Bio 47 Bentonite « Collins Gulch M 371 AK-630 Sanldlne 79* Bentonite • Qullchena m 372 GSC67-42 Hb 73+4 Granodiorite China Head Mtn. stock 51°10'N. 122°23'W. GSC Paper 69-2A, P. MAGGIE MINE (Cu-Mo Porphyry) 373 MM16 Whole R 6l.2±2 Biotite porphyry « 50°52.3-55.5'N. McMilllan, 1970, 121 6 23.1-23.7'W. pp. 324-325 (Haggle) Unmlnerallzed volcanic strata that overlie mineralized Nicola unc onformably rocks - Cralgmont 37* 375 GSC61-29 Bio 80 (108)* Lava,. 50°12'N. I20°55'w. GSC Paper 62-17, unpublished P. 376 GSC65-27 Bio 100±6 Quartz diorite boulder in 51°11'N. eonglomeratel22°35'W. GSC Paper 66-17, P. 377 GSC65-25 Bio 166±11 Quartz diorite « 5l°15'N. 120°58'W. GSC Paper 66-17, P. 378 GSO65-23 Bio 105+.9 Quartz monzonite • 51°4l'20"N. 120°07 , 25"W. GSC Paper 66-17, P. EAGLE GRANODIORITE 379 GSC65-9 Bio 98±6 Granodiorite * 49°l6'45"N. 120°46'W. GSC Paper 66-17, 380 GSC62-56 Bio 1 4 3 Granodiorite • 4 9 ° 3 1 ' N . 120 6 55'W. GSC Paper 63-17, 381 E-la b Bio Bio 103tl.6 ., 106.2±1.7 H * • Roddick, 1970 382 E-2-1 2 Bio Bio 99.1±1.6 96.4±1.5 m • • m 383 E - 3 Kusc Muso 71.7±1.2 71.8+1.2 Pegmatite • • m 384 E - 4 Bio 85.4±1.4 Granodiorite * » m 385 E-5 Bio 102.±1.6 m * • m 386 E-6 Hb 104.5±1.7 u • • m 387 E-7 Bio 106.2+1.7 m • • m •See reference. 150. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Report Referenoe Age Ho. Number and In m.y. Rook Type Unit Looatlon Referenoe Mineral Dated 388 E -8-1 Hb 111.4+1.8 Granodiorite • * Roddick, 1970 111 .7±1 .7 2 Bio 112 .1±1 .8 « • 389 GSC65-22 Bio 14019 Quartz • 51°49'N. GSC Paper 66-17, P. 25 (see 378) monzonite 120°03'30"W. 390 GSC65-25 Bio 166+.11 Quartz » 51°15'N. GSC Paper 66-17, P. 2 8 diorite 120°58'W. IRON MASK BATHOLITH 391 G S C 6 6 - 4 1 Bio 176±8 Pegmatite Iron Mask 50°35'N. GSC Paper 67-2A, p. 39 120°21'W. (Fargo Mineral Claim) BRENDA MINES (see Oriel 1972) 392 W67-3 Bio Hb 1 4 8 + 6 168±8 Granodiorite Okanagan Batholith Brenda Pit White et al. 393 V67-4 Bio Hb 14815 I66t8 Granodiorite Okanagan Batholith Brenda Pit a SIMILKAMEEN BATHOLITH 394 H-l Bio 154.5+2.4 Granodiorite Similkameen Roddick, 1970 395 H-2 Hb Bio 152.2+2.4 1 4 9 . 5+2 . 3 a « 396 H-3 Bio 156.9+2.4 m . a • • 397 H-4 Bio 156.4+2.4 a a - • 398 H-10 Bio 156.1+2.4 a - a * • HEDLEY COMPLEX 399 H-6 H-6a Hb Hb 170.7+2.7 179.5*3.7 Diorite Hedley Complex • 4oo H-8 Hb 183.2±2.9 Diorite a • 401 H-11L Hb 170.812.6 Diorite a • 402 H-11H Hb 176.2±2.9 Diorite a • 403 H-12. Hb 188.313.0 Gabbro a • 404 H-14 Hb 190.213.0 Diorite a « Roddick 1970 TULAMEEN COMPLEX 405 GSC62-55 B i o 1 8 6 406 T - l a 407 I B 405a GSC62-57 Bio 68.011.2 Bio 81.9H. 3 Hb 286 Pyroxenlte Tulameen 49°34 'N . 120°54'W. Pyroxenlte Pyroxenlte Pyroxenlte 49°26'N. 120O48'W. GSC Paper 63-17, p. 38 Roddlok, 1970 Roddick & Farrar, 1 9 7 1 GSC Paper 63 - 1 7 , p. 39 • See referenoe. 151. TABLE (oont'd) Published K-Ar ages referred to In this report, D-l Report ReferenoeAge No. Number and In m.y. Rook Type ' Unit Location Referenoe Mineral Dated 408 2H-1 2 3 Hb Hb Hb 192.5+2.9- 191.5+2.9 191.6±2.9 Diorite Tulameen • Roddlok & Farrar, 409 3 B Bio 127.4±2.0 Diorite M « w 410 5H-1 2 I Hb Hb Hb Hb 201.5+3.0 200.4+3,0 196.6+3.0 199.1±3.0 Hornblen- dlte •1 • m 411 7W Whole R 1?8.1±7.2 Amphibolite M • N 412 8B Bio 151.5±2.3 Hb ollnopy- roxenite H • M 413 8V Whole R 198.2±3.2 M • M 414 8P Pyrox 922.3tl3.2 Hb ollnopy- roxenlte U • M 415 8H-1 -2 Hb Hb 206.4±3.1 203.5±3.1 M • • 416 9 H Hb 209.6+3.5 It m • 41? 10B Bio 171.5+2.6 Pyroxenlte m • m COPPER MOUNTAIN, B.C. 418 CM-ore-65 Bio 194±7 Biotite velnlet with ohaloopyrlte Wolf Creek 49°19'N. 120°32'W. Sinclair 4 Wh 419 CM-F20a-65 Bio 199+7 Monzonite - Copper Mtn. Stock m 420 CM-AL7-65 Bio 194+8 Monzonite * m 421 CM-E2a-65 Bio Clino- pyroxene 151+6 150+.9 Diorite hydrothermally altered » • m 422 CM-12-65 Bio 182±8 Gabbro « • m 423 VP-69KA-1 Bio 194±8 Latlte porphyry Lost Horse 49°19*N.» 120°32'W. Preto et al.» 424 VP-69KA-2 Bio 197+8 Diorite Smelter Lakes " m 425 VP-69KA-3 Bio 200±8 Diorite m n 426 VP-69KA-4 Bio 101±4 Quartz monzonite Verde Creek m 42? VP-69KA-5 Bio 98+4 Quartz monzonite Verde Creek m 428 VP-69KA-6 Bio 181±7 Diorite . Volgt • m 429 VP-69KA-7 Bio 194+7 Diorite Volgt m 430 VP-69KA-8 Bio 194+8 Mleromonzonlte porphyry Lost Horse m 431 VP-69KA-9 Bio 197+8 Latlte porphyry Lost Horse dike m 432 VP-69KA-10 Bio 195±8 Mleromonzonlte porphyry Lost Horse m 433 VP-69KA-13 Bio I89+.8 Biotlte-sulphlde pegmatite vein m * See referenoe. 152. TABLE (oont'd) Published K-Ar ages referred to in this paper, D-l Report R e f e r e n o e Ko. N u m b e r a n d M i n e r a l D a t e d A g o In m.y. Rook Type Unit Looatlon Referenoe GUICHON BATHOLITH -• HIGHLAND VALLEY, B. C.• 434 1DB70 Seriolte 196±6 Quartz diorite Bethsalda « Blanohflower, 1971 435 2DB70 Seriolte 195+6 „. . ! * . N • m 436 3DB70 Bio 189+6 a a • M 437 4DB70 Bio 203+6 a a « ft 438 5DB70 Bio 198+6 M a • • 439 K63-240 Bio 199±8 Breccia Iona Breccia « White in Northoote, 1969 440 CSC66-37 Bio 184t8 Quartz diorite Gulohon Batholith 50°29'20"N. 120°51'55"W. GSC Paper 67-2A, PP. 35-36 441 GSC66-38 Hb 189±20 Quartz diorite M 50°29'20"N. 120°51'55"w. GSC Paper 67-2A, PP. 36-37 442 443 444 GSC66-40 Hb 187+27 GSC66-39 Bio 197±10 (Replaces GSC63-3)* AK-44 Bio 186 Quartz diorite Quartz diorite H II 50o34'45"N. 121°13'25"W. 50°29'N. 120°58'W. GSC Paper 67-2A, Baadsgaard, 1961 PP. 37-38 445 GSC62-63 Bio 224** Granodiorite W 50°29'10"N. 121°03'20"W. GSC Paper 63-17, pp. 41-42 446 GSC62-59 Bio 227»* Quartz diorite « 120°55'05"W. GSC Paper 63-I7, p. 40 447 GSC62-61 Bio 230*» 237*« Quartz diorite 50°28«55"N. i20°55'4o"w. GSC Paper 63-17, pp. 40-41 448 CSC62-60 Bio 237** Quartz diorite • 50°29'N. 120°55'W. GSC Paper 63-17, p. 40 449 GSC62-62 Bio 242«* Granodiorite m 59°29'10"N. 121°03'30"W. GSC Paper 63-17. p. 41 450 GSC62-58 Bio 245»* Quartz diorite m 50°30«03"N. 120°56'25"W. GSC Paper 63-17, P. 39 451 GSC63-2 Bio 242±12 *« Granodiorite M 50°26'N. 121 o l4'20"H. GSC Paper 64-17, p. 12 (Pt. 1), 452 GSC63-3 Bio 265±l4«» Quartz diorite ft 50°34'45"N. 121613'25"W. GSC Paper 64-17, pp. 12-13 (Pt. 1), 453 GSC63-4 Bio 240±12** Quartz diorite « 50 o 29*20"N. 120°51'55"W. GSC Paper 64-17, P. 13 (Pt. 1), 454 GSC63-5 Bio 248±12 Granodiorite 50°13'10°N. GSC Paper 64-17, 120°55«00"W. pp. 13-15 (Craigmont Open Pit) (Pt. 1), 455 GSC66-35 GSC66—36 (see 389) Bio Hb 194+10 198tl2 Granodiorite • 51°20'40"N. 120°24'00"W. GSC Paper 6?-2A, PP. 34-35 * See reference. •» Values considered to be high (see reference). 153. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Report Referenoe Age No. Number and In m.y. Mineral Dated Rook Type Unit Looatlon Referenoe TERTIARY AGES AK-25 Bio 36 Granite Casoade 49°01'N. 118°18'W. Baadsgaard. et al.i 196 45? AK-27 Bio 8 Granite Nelson(?) Batholith 50°00'N. 118°06'W. M CORYELL 458 AK-28 Bio 54 Syenite Coryell 49°03'N. 118°03'W. 459 AK-26 Bio 58 Syenite 49°04'N. 11?°58'W. 460 GSC60-20 Bio 27 Leuorosyenite " 49°24'N. 118°02'30"W. GSC Paper 61-17, pp. 12 461 GSC61-13 Bio 32 Granite * 49°50'30"N. H 7 0 5 6 ' 3 0 » w . GSC Paper 62-17, P. 11 462 GSC61-12 Bio 53 Granite 49°49'15"N. 117°56«20"W. GSC Paper 62-17, P. 10 463 CX70-17 Bio 50.6±1.5 Monzonite 49°05'N. 117°15'W. Macdonald, 1972, in pre paration 464 CX70-21 Bio 49.5±1.5 Lamprophyre dike 49°05'N. 117°15'W. 465 R70-1 Bio 48.9±1.4 Monzonite - • Fyles, et al., 1 9 7 t i - 466 B70-5 Bio 49.0+1.5 Monzonite • * m 467 B70-18 Bio 48.3±1.4 Syenite • m 468 R70-12 Bio 48.1+1.5 Gabbro Diorite dyke • Fyles, et al., 197 469 R70-3 Bio Hb 46.4+1.5 48.4+.1.5 Lampro- phyre Spokane dyke * 470 R70-4 Whole R 58.1±2.0 60.5+2.0 Lampro- phyre Conglomerate * dyke 471 R70-7 Bio 49.0±1.4 Lampro- phyre Mayflower dyke « 472 B70-9 Bio 48.8+1.6 Lampro- phyre Nickel Plate * dyke 473 B70-11 Bio 49.2tl.4 Lampro- phyre Dyke • 474 B70-13 Bio 48.1+1.6 Lampro- phyre Headwall dyke • 475 B70-14 Whole H 47.0+.1.8 Hornfels • • 476 B70-15 Bio 48.7+1.5 Quartz diorite Rainy Day Stook • 477 R70-16 Bio 50.5+1.5 Grano- diorite Trail Batholith • 478 B70-1? Bio 49.5±1.4 Grano- diorite Trail Batholith • 479 R70-2 Bio 47.3+1.5 Monzonite RosBland Monzonite • • See referenoe. 154. TABLE (oont'd) Published K-Ar ages referred to in this report, D-l Beport Referenoe Age No. Number and in m.y. Mineral Dated 4 8 0 R70-6 4 8 1 B?l-1 Bio Bio Bio Rook Type Unit Location Referenoe 89.7+2,8 Monzonite Rossland 90.8+2.0 Monzonite 58.8+1.8 Monzonite Rossland Monzonite Fyles, et al., 1973, POST-TECTONIC INTRUSIONS 4 8 2 G S C 6 6 - 4 6 Bio 46+3 4 8 3 C S C 6 6 - 4 5 Bio 39±5 4 8 4 G S C 6 3 - 1 Phlogo- 4 1 + 1 0 plte 4 8 5 GSC63-7 Bio 5 6 ± 8 Quartz monzonite Quartz monzonite Lamprophyre Granite 49°07'24.4"N. GSC Paper 67-2A, pp. 44-45 118°23'14"W. 49°02'49.3" ..'GSC Paoer 6?-2A, pp. 41-42 118°21'43"W. 51°17'N. 118°28'W. 50°00'N. 123°58'W. GSC Paper 64-17, (Pt. 1), p. 11 GSC Paper 64-17, (Pt. 1), p. 16 TERTIARY VOLCANICS 486 F69-203 Whole R 51.6+1.7 Latlte OK Volcanic 49+2 487 AK-112 488 AK-I50 489 AK-151 490 * Bio Bio Bio Bio Ash Midway 4 8 + 2 4 6 + 2 5 1 . 6 * 1 . 8 Pulasklte Kettle porphyry River Daclte Kettle River Marron 49°03.8*N. U 8 ° 5 8 . 4 ' W . 49°02.8'N. 1 1 8 ° 5 3 . 1 ' W . 49°48'N. 119°06.l 'W. Fyles, et al., 1973, Mathews, 1964 East of Formation Yellow Lake* p. 397 (Kitley Lake member) Church, 1970, In (GEM), OKANAGAN 491 W65-6 Muse 139+5 Granite Okanagan » White et al., 1 9 6 8 492 W65-5 Muse 144+6 Granite M * 493 W65-7 Sericite 140+6 Footwall alteration N . # 494 W65-4 Bio 82t3 Granite ft • 495 W66-7 Bio 99+4 Granite ft * - 496 W65-3 Bio 118±4 Granite t l • • 497 W67-I Sericite 114*5 • f l • • " NELSON BATHOLITH 498 499 GSC66-50 GSC63-10 Hb Bio 141+16 123+20 Quartz diorite Ruby Stock 50°04'57.5"N. 117°43'59"W. GSC Paper 67-2A, p p . 46-47 500, GSC66-51 Hb 136±14 Granodiorite Nelson 49°47.0'N. 117°22.4'W. GSC Paper 67-2A, p . 47 501 GSC66-52 Hb 146+10 Granodiorite (porphyrltio) Nelson 49°49'N. 117°12'W. GSC Paper 67-2A, p p . 47-48 502 GSC66-53 Hb l4l±24 « Nelson 49°46.4'N. 117°04.5'W. GSC Paper 67-2A, p . 48 503 GSC62-27 Bio 159 * Nelson II CSC Paper 67-2A, p . 20 504 CSC66-54 GSC62-5 Hb Bio 152tl0 128 Granodiorite Porcupine stock 49°15'N. 11?°05'W. CSC GSC Paper Paper 67-2A, 63-17, p p . p p . 48-49 7-8 * See reference. 155. TABLE (oont'd) Published K- D-l Ar ages referred to in this report; Report Reference No. Number and Mineral Dated Age In m.y. Rock Type Unit Location Reference 505 GSC62-5 Bio 128 Granodiorite Porcupine stook 49°15'N. 117°05'W. GSC Paper 63- I7 , PP . 7-8 506 c Bio 150+6 Quartz monzonite Nelson 49°53 ,45"N. U7°l4'23"W. Nguyen, et al.. 1968 507 D Bio I69t6 Lamprophyre Dike (outs Nelson) 49°53'49"N. 117°l4'23"W. 508 K Hb l6l±6 Quartz monzonite Mt. Carlyle 49°54 ,58"N. stook in^Ok'lB'V. 509 L-236 Bio 135+5 Hornfels Zenollth in 49 o 52'20"N. Nelson 117°06'57"W. Batholith 510 R-ll Bio 120t5 Granodiorite (porphyritic) Nelson 49°53'15"N. 117°6'25"W. 511 R-12 Bio 146+5 Quartz diorite w 49°52 '56"N. 117°6'38"W. 512 R-13 Bio 130+5 Granodiorite (porphyritic) m 49 ° 4 3 « 5 8"N. 117°9"45"H. • 513 8 Hb 150±5 Quartz monzonite m 49°57*29"N. 117°21'l6"w. * 514 GSC61-17 Bio 131- Granodiorite m 49°51'30"N. 117°02,48"W. GSC Paper 62-17. P« 13 515 CSC62-27 Bio 159 Granodiorite m 49°46'24"N. 117°04'30"W. GSC Paper 63-17, P. 20 516 GSC62-29 Bio 163 Granodiorite m 49°46« 54"N. 117 20'18"W. GSC Paper 63-I7, P. 21 517 GSC62-26 Bio 165 Granodiorite m 49°45'48"N. 117°13'30"W. GSC Paper 63-17, P. 20 518 GSC62-28 Bio 1 7 1 ' Granodiorite m 49°47*N. 117°22 , 24"W. GSC Paper 63-17, PP . 20-21 519 GSC62-30 Bio 171 Granodiorite m 49°56 , N. 11708'W. GSC Paper 63-17, P. 21 AGES PREVIOUSLY. ASSIGNED TO NELSON BATHOLITH 520 GSC60-21 Bio 49 Quartz monzonite Nelson 49°42'N. 117°19'W. GSC Paper 61-17, P. 13 521 G S C 6 0 - 2 2 Bio 55 Granodiorite (porphyritic) 49°36 , N. 117015'W. GSC Paper 61-17, PP . 13-14 522 GSC62-32 Bio 63 Granodiorite « 49°29'18"N. 117°20'30"W. GSC Paper 63- I7 , PP . 2 2 - 2 3 523 GSC59-1 Bio 86 Granodiorite M 49°29'N. 117o20«W. GSC Paper 60-17, P. 5 524 G S C 6 2 - 3 1 Bio 105 Leuoogranlte m 49°36'36"N. 117007'54"w. GSC Paper 63-17, P. 2 2 POST TECTONIC INTRUSIONS (see 482-485 and referenoe) 525 GSC 64-22 Bio 52i6 Syenite • 51°55.5*N. 118°10.5»W. GSC Paper 65-17, P. 20 526 GSC64-15 Bio 96+5 Quartz monzonite • 51°27'N. 119°56'W. GSC Paper 65-17, P. 16 527 GSC64-16 Bio 80+6 Granodiorite • 51O17'20"N. GSC Paper 65-17, PP . 16-17 • S e e r e f e r e n o e . 156. TABLE D-l (oont'd) Published K-Ar ages referred to In this report. Report Referenoe Age No. Number and In m.y. Rook Type Unit Mineral Dated Location Referenoe CHINA HEAD MOUNTAIN STOCK 528. GSC67-42 Hb . 73+> Granodiorite • - 51°10'N. 122°23'W. GSC Paper 69-2A, p. 25 529 GSC60-18 Bio 45 530 GSC60-19 Muso 63 531 GSC62-12 Bio 76 532 GSC62-8 Muso 83 533 GSC62-11 Bio 86 534 GSC62-10 Muse 91 535 GSC62-9 Muso 97 FRI CHEEK BATHOLITH Quartz Fry monzonite Creek Quartz " monzonite Quartz " monzonite Quartz " monzonite Quartz " monzonite 50°05'N. 116°51'W. 49°52'N. ll6°34'W. 49°59'N. 116044'12^W. GSC Paper 61-17, P. 11 GSC Paper 63-I7, PP. 10-11 GSC Paper 63-17, P. 9 50°05'24"N. GSC Paper 63-I7, p. 10 116°33'24"W. GSC Paper 63-17, P. 9-10 50°Q1'54"N. 116°39'42"W. GSC Paper 63-17, p. 9 536 GSC62-7 Bio 33 53? KA 118 Bio 77 538 GSC62-6 Bio 100 BAXONNE BATHOLITH Granodiorite Bayonne 49° l6 '30"N. Batholith . li,6°39'W. Granodiorite Kootenay Lake 49°15'N. 116°39'W. Quartz Bayonne 49°24'30"N. monzonite Batholith 116°44'18"W. GSC Paper 63-17, pp. 8-9 Baadsgaard et a l . , 1961 GSC Paper 63-17, p. 8 539 GSC62-43 Bio 118 540 GSC62-4 Bio 119 ANGUS CREEK STOCK Granodiorite Angus 49°33'N. Creek 116°08'36"W. LOST CREEK STOCK Quartz monzonite GSC Paper 63-17, p. 30 49°05'36"N. GSC Paper 63-17, p. 7 117°10'12°W. 541 CX-70-19 Bio 100±3 Granite DODGER STOCK Dodger Stock 49°05'N. 117°15'W. Macdonald, 1972, In prep. KUSKANAX BATHOLITH 542 GSC62-33 Bio 66 Quartz 543 GSC62-34 Muso 90 monzonite 544 GSC66-48 Muso 137t7 Feldspar porphyry Kuskanax 50°4l'N. 117°53'M. GSC Paper 63-17, pp. 24-25 50°25*15"N. GSC Paper 67-2A, pp. 44-45 117°20'50"W. 545 AK 46 Bio 355 546 AK 83 Bio 360 54? AK 84 Bio 304 • See referenoe,. , - 7 ICE RIVER COMPLEX Jaoupiranglte Ice Blver 51°10'N. 116°23'W. Mlnette Pegmatite 51°08'N. 116°24'H. 51°11'N. 116°27'W. Baadsgaard, et a l . , 196la 157. TABLE (cont'd) Published K-Ar ages referred to i n this report, D-l Report Referenoe No. Number and Mineral Dated Age In m.y. Rook Type Unit Looati on Referenoe 548 CSC59-7 r Bio 340 Syenite Ice River 51°12'N. U6°29'W. GSC Paper 60-17, PP . 6-7 549 GSC59-8 Bio 330 * N 51°12'N. 116°29'W. GSC Paper 60-17, P . 7 550 Pyroxenlte 392 Biotite pyroienlte • * Rapson, 1963, pp . 116-124 551 Bio 336 Biotite pegmatite • • a 552 Bio 327 Mlnette s i l l • * TOBY STOCK 553 GSC66-49 Eb 162*8 Granodiorite Toby 50°13'N. 116°34'W. GSC Paper 67-2A, PP . 45-46 554 GSC62-14 Bio 179 Granodiorite gneiss Toby 50°11'N. 116°34'W. GSC Paper 63-17, PP . 12-13 555 GSC62-13 Bio 232 Granodiorite Toby 50°12'36"N. 116°33'24"W. GSC Paper 63-17, PP . 13-14 ADAMANT BATHOLITH 556 GSC64-23 ,Whole R 97+12 Monzonite Adamant Pluton 51°44'N. 117°55'W. GSC Paper 65-17, PP . 20-21 55? GSC61-24 Bio 90 Granodiorite Adamant •-5i 0 46*8"iJ. U7°54'20"w. GSC Paper 62-17, PP . 16-17 558 GSC62-24 K - feldspar 92 Granodiorite Adamant 5l°44'30"N. 118°44'W. GSC Paper 63-17, PP . 18-19 559 GSC61-22 Bio 131 Pegmatite Adamant 51°42'40"N. 117°50'30"W. GSC Paper 62-17, P . 15 560 561 GSC61-23 GSC62-25 Bio Hb 200 116 Granodiorite Adamant 51°46'8"N. 117°51'30"W. GSC Paper 62-17, GSC Paper 63-17, PP P . . 15-16 19 562 GSC61-21 Bio 281 Granodiorite Adamant 51°42'40"N. 11?°50'30"W, CSC Paper 62-17, P . 15 WHITE CREEK BATHOLITH 563 GSC60-3 Bio 18 Quartz monzonite White Creek 49°53'N. 116°22'W. GSC Paper 61-17, P . 6 564 GSC60-4 Bio 29 Quartz monzonite \. « 49°50'N. 116°17'W. GSC Paper 61-17, PP. , 6-7 565 GSC60-5 Bio 56 Maflc-rlch inclusion m 49°48'N. 116°16'W. GSC Paper 61-17, P . 7 566 GSC60-6 Bio 60 Quartz monzonite 49°51'N. 116°14'W. GSC Paper 61-17, P . 7 56? GSC61-9 Bio 73 Granodiorite « 49°48'33'*N. 116°13'10"W. GSC Paper 62-17, P . 9 568 GSC60-7 Bio 79 Granodiorite N 49°48«N. 116°13'W. GSC Paper 61-17, PP. . 7-8 569 570 GSC61-11 GSC61-10 Huso Bio 80 82 Quartz monzonite if 49°51'10"N. 116°16'40"W. GSC Paper 62-17, f P . P . 10 9 571 GSC 62-2 Bio 126 Meta- dlorlte H 49°47'18"N. 116°18'54"W. GSC Paper 63-17, P . 5 * See reference. 158. TABLE. (oont'd) Published K-Ar ages referred to in this report. D-l Beport Reference Age No. . Number and in m.y. Rock Type Unit Location Referenoe Mineral Dated 572 GSC62-3 Bio 138 Quartz White 4 9 ° 4 5 ' 4 2 " N . GSC Paper 63-I7. P P . 7 - 8 diorite Creek 1 1 6 ° 1 9 ' 4 8 " W . s i l l 573 GSC62-16 Bio 108 574 GSC61-19 Bio 205 HOBSETHIEF CREEK BATHOLITH Quartz Horsethlef 50°36'12"N. monzonite Creek ll6630'42"W. Granite 575 GSC65-21 Bio 96+16 Schist 576 GSC65-20 Muso 55+8 50°38'6"N. 1I6°35'42°W. 51°48'N. U 7 ° 5 8 ' W . GSC Paper 63-17, P. 14 GSC Paper 62-17, pp. 13-14 GSC Paper 66-17, pp. 24-25 '578 GSC62-23 Bio 579 GSC70-5 Hb 1 6 8 1 6 4 + 9 FANG CREEK STOCK Granodiorite Fang stook 51°20'N. 117°50'W. GSC Paper 63-17, p. 18 GSC Paper 71-2, p. 8 5 8 0 GSC62-21 Muse 91 5 8 1 GSC62-20 Bio 92 582 GSC62-19 Bio 94 583 GSC62-22 Muse 120 BATTLE BATHOLITH Quartz monzonite Quartz monzonite Pegmatite Battle Batholith 51°03'N. 117°30'W. 51°03'N. 117°30'W. 51°03'N. 117°30'W. GSC Paper 63-17, p. 17 . P. 16 GSC Paper 63-17, p. 16 GSC Paper 63-17, ppJ.7-18 584 GSC61-20 Bio 100 585 GSC62-17 Bio 586 GSC62-18 Muso 132 138 BUGABOO BATHOLITH Granodiorite Bugaboo 50°44'6"N. Batholith 116°55'30"W. Quartz monzonite 50°45'36"N. 116°49'6"W. GSC Paper 62-17, p. 14 GSC Paper 63-17, p. 15 , pp. 15-16 587 GSC61-18 Bio 127 588 GSC62-15 Bio 145 GLACIER CREEK STOCK Granodiorite Glacier Creek Granodiorite " GSC Paper 62-17, P. 13 50°23'12"N. 1 1 6 ° 4 7 ' 4 9 H W . 50°23'12"N. GSC Paper 63-17, p. 13 116°47'42"W. 589 G S C 5 9-5 B i o 11 590 GSC59-4 Bio 13 591 GSC60-8 Bio 15 592 G S C 5 9-6 B i o 16 SHUSWAP METAMORPHIC COMPLEX (After Gabrielse & Reesor, 1 9 6 4 ) VALHALLA COMPLEX Valhalla 593 CSC60-9 Bio 25 Granite- gneiss Granodiorite gneiss Granlte- gnel88 Granodiorite gneiss Granitic gneiss 49°51*N. 117°4l'W. 49°51'N. 117o37'30"W. 49°57'N. 117°35'10"W. GSC Paper 60-17, p. 6 GSC Paper 60-17, p. 6 GSC Paper 61-17, p. 8 49°51'30"N. GSC Paper 60-17, P . 6 117°37'W. 49o52*30"N. GSC Paper 61-17, P . 8 117°4l'15"W. * See referenoe. 159. TABLE (oont'd) Published K-Ar ages referred to In this report. D-l Report R e f e r e n o e A g e No, Number and In m.y. Mineral nat.nd Rook Type Unit Looatlon Referenoe 594 CSC60-10 31o . 28 595 GSC60-II Bio 31 596 CSC60-12 Bio 42 597 CSC6O-13 Bio 46 598 GSC60-14 Bio 47 599 CSC60-15 Bio 58 600 CSC61-16 Bio 58 601 GSC61-15 Bio 59 602 GSC60-I6 Bio 60 603 GSC60-17 Bio 62 604 GSC61-14 Bio 66 605 CSC62-39 Bio 69 606 CSC63-II Bio 107±6 Quartz monzonite (gneiss) Granite gneiss Granite Pegmatite Gneiss Gneissic Granite Granite Granite- gneiss Granite- gneiss Gneiss Granite Quarts monzonite Quartz monzonite Valhalla 607 GSC63-IO Bio 123±20 Diorite 608 GSC63-12 Bio 7 4 + 4 609 GSC63-8 Bio 110±6 610 A Bio 149±5 611 G S C 6 6 - 4 3 Hb 6l_6 Quartz monzonite Granite* 49°37'N. 117°48'W. 49°47'30"N. 117°37'W. 49°48'N. 117°49'40"W. 49°42'53"N. 117°42'20"W. 49°46'N. 117°29'W. 49°53'13"N. 117°42'W. 49°48'N. 117°54'W. 49°42 , 25"N. 117°54'W. 4o°53'47"N. 117°37'20"W. 49°42'N. 117°36'W. 49°44'N. 117°58'W. 49°59«l4"N, 117°50'H. 50°l'23"N. 117°42'23"W. 50°4'57.5"N. 117°43'59"M. 50°2'17"N, 117°35'19"W. Granodiorite Fennell Cr. 49°53'12"N. (porphyritic) Stock 117°l4 , ll"W. 612 GSC66-44 Hb 613 GSC62-35 Bio 79±8 64 Granodiorite Shuswap gneiss Granodiorite Shuswap gneiss 50°34'N. 118°9'W. 50°33'12"N. 118°o4 , 54"W. GSC Paper 61-17, PP. 8-9 GSC Paper 61-17, P. 9 GSC Paper 61-17, p. 9 GSC Paper 61-17. PP. 9-10 GSC Paper 61-17, p. 10 GSC Paper 61-17, P. 10 GSC Paper 62-17, P. 12 GSC Paper 62-17, P. 12 GSC Paper 6l-17, PP. 10-11 GSC Paper 61-17, p. 11 GSC Paper 62-17, P. 11 GSC Paper 63-17, PP. 26-29 GSC Paper 64-17, Pt. 1, p. 19 GSC Paper 64-17, Pt. 1, p. 18 GSC Paper 64-17, Pt. 1, p. 20 GSC Paper 64-17, Pt. 1, pp. 16-17 Nguyen, et a l . , 1968 GSC Paper 67-2A, pp. 40-41 GSC Paper 67-2A, p. 41 GSC Paper 63-17, pp. 25-26 614 AK 25 Bio 36 615 G S C 6 1 - 5 Bio 52 6 1 6 C S C 6 1 - 4 Bio 57 617 AK 29 Bio 57 618 GSC60-1 Bio 6 2 Gneissic granite Gneiss Pegmatite Granodiorite M0NASHEE GROUP Honashee Gneiss 49°1'N. 118018^. 50°34'N. 118°43'W. 50°34'N. 118°43'w. 51°08'N. 118°11'H. 50°15'N. 119°9'w. Baadsgaard et a l . , 1961 GSC Paper 62-17, P. 6 GSC Paper 62-17, P. 6 Baadsgaard et a l . , 1961 GSC Paper 61-17, P. 5 * See reference. 160. TABLE (oont'd) Published K- D-l Ar ages referred to In this report. Beport ReferenoeAge No. Number and In m.y. Mineral Dated Rook Type Unit Location Reference 6 1 9 GSC62-45 Muso 6 5 620 GSC62-44 Bio 70 621 GSC61-6 Bio 71 622 GSC62-46 Huso 73 623 GSC62-4? Bio 76 624 GSC61-8 Muso 8 1 625 G S C 6 2 - 4 8 Bio 8 1 6 2 6 GSC62-36 Bio 6 2 7 GSC61-7 Bio 6 2 8 AK 2? Bio 6 2 9 AK 4 ? Bio 96 89 102 Quartzite Pegmatite Quartzite Granite Pegmatite Paragneiss Gneiss Paragneiss Granite Granite (porphyrltio) Monashee 50°49'13"N. 118°15'9"W. 50°56'N. 118°27'W. 50°49'N. 118°15'30"W. 50°47'24"N. 118°15'16"W. 50°49'3"N. 118°15'48"W. 50°46'44"N. 118°l4'l6"M. 50°32'N. 118°2'W. 50 o S6'N. 118°27'W. 50°00'N. 118°06'W. 49°58'N. 118°18'V. GSC Paper 63-I?, p. 31 GSC Paper 62-17. P. 7 GSC Paper 63-I7, PP. 31-32 GSC Paper 63-I7, p. 32 GSC Paper 62-17, PP. 8-9 GSC Paper 63-17, PP. 32-34 GSC Paper 63-17, p. 26 GSC Paper 62-17, PP. 7-8 Baadsgaard et al., 1961 Baadsgaard et al., I96I 630 GSC62-37 Bio 127 631 GSC61-2 632 GSC61-3 Bio Muso 1 ? 6 l 4 o 633 GSC61-1 Bio 140 MT. IDA GROUP Leucooratlo rock Sohist Gneiss 50°46'N. 119020'H. 50°48«N. 118°42 , W. GSC Paper 63-17, p. 26 GSC Paper 62-17, p. 5 1 P. 6 50°47'30"N. GSC Paper 62-17, p. 5 118°40'W. METAMORPHIC ROCKS NORTH AND SOUTH OF ADAMANT BATHOLITH Schist * 634 GSC62-49 Bio 73 635 GSC62-50 Muse 72 636 GSC61-28 Muse 107 Pegmatite 637 GSC62-51 Bio 119 Schist 638 GSC62-52 Muse 124 639 GSC62-53 Bio 146 Schist 640 GSC62-54 Muso 205 51°54'10"N. GSC Paper 63-17, p. 34 117 D 56'8"W. 5 1 ° 4 8 ' N . 1 1 7 ° 5 7'W. GSC Paper 62-17, p. 18 51°34'55 U N. GSC Paper 63-17, P. 35 " ~'4"W. II7038 . 0 51°34'5"N. 117 6 33'30"W. GSC Paper 63-17, p. 36 . PP. 37-38 UNDIFFERENTIATED METAMORPHICS 641 GSC64-18 Phlo- 51+10 Marble goplte Chancellor Formation 642 GSC64-19 Bio 6 4 3 GSC64-20 Muso 5 8 + 6 67+10 Quartzite 51°58'N. 118 6 1.5'W. 51°47'N. 117°43'H. GSC Paper 65-17, p. 1 8 GSC Paper 65-17, P. 1 8 161. TABLE (oont'd.) Published K- D-l Ar ages refered to In this report. Report Referenoe Age No. Number and In m.y. Mineral Pitted Rook Type Unit Location Reference 644 KN-68-158 Whole R 32.3*1.6 .7 Vancouver Island (Supplement) Dike 645 PN-70- 646 KN-69- 124A Bio 10 Whole R 64? KN-69-8 Whole R -98 Whole R 6 4 8 KN-69- VI 649 PN-70- 650 KN-69- 651 KN-68- 652 CN-70- 653 KH-68. 654 KN-69' 655 CN-70 •124A Bio .327 Whole H •177A Bio •152 Bio •168 Whole R •234 Bio -204B Bio 50.6ti 103*4 134*4 139*4 145*5 l45±6 1 5 * * 6 159*5 l6ii6 163*6 l66±5 656 KN-69-264A Bio 169*6 65? Whole R 182*6 Intrusive Rhyodaolte Rhyollte Rhyodaclte Intrusive Rhyodaolte Intrusive Intrusive Granitic Intrusive Bonanza E. Straggling Unpublished K. Northoote Island B.C. Dept. Mines 4 Pet. Res. Hepler Creek " East side of mouth " of Hansons Lagoon Cape Soott * East side of mouth * of Hansons Lagoon Helper Creek " Radar Domes San Josef " East End Rupert Inlet " Southeast of Nahwittl " Lake Apple Bay North of Nahwittl Lk. Ridge east of Stranby " & south of Irony North of west end of " Nahwittl Lake Shaft Creek (Llard Copper) B.C. unpublished age Dept. Mines & Pet.

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