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U-PB geochronometry and regional ecology of the southern Okanagan Valley, British Columbia : the western… Parkinson, David Lamon 1985

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U-PB  GEOCHRONOMETRY  OKANAGAN  A N D REGIONAL G E O L O G Y OF THE  V A L L E Y , BRITISH C O L U M B I A :  T H E WESTERN  METAMORPHIC CORE  SOUTHERN  BOUNDARY  COMPLEX  by DAVID L A M O N BA.  UNIVERSITY  PARKINSON  O F CALIFORNIA,  A THESIS SUBMITTED  SANTA BARBARA,  IN PARTIAL  T H E REQUIREMENTS  FOR  MASTER O F  FULFILMENT  THE DEGREE  OF  SCIENCE  in THE FACULTY  OF G R A D U A T E  STUDIES  Geological Sciences  We  accept this thesis as conforming to the  required standard  T H E UNIVERSITY  O F BRITISH  August, David  COLUMBIA  1985  Lamon Parkinson  1981 OF  OF  A  In  presenting  this thesis in partial fulfilment of the requirements for an advanced  degree at the The University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may Department  or by  his or her representatives.  be granted by the Head It is understood  that  copying or  publication of this thesis for financial gain shall not be allowed without my permission.  Geological Sciences The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5  Date: August. 1985  of my  written  ABSTRACT  The  Okanagan Valley is the boundary between the Okanagan Metamorphic and  Complex of the Omenica Belt to the east and Okanagan Metamorphic grade paragneiss and  and  Plutonic  Belt  eugeosynclinal  rocks,  intruded  by  age.  These  are  mid-Cretaceous  the Intermontane Belt to the west. The  Complex  consists  consists  of  tectonically large  scrambled  Jurassic  overlain  plutons  by  Eocene  sedimentary rocks, capped by fanglomerate breccias and The  thesis area contains  Oliver pluton  originally  late  Paleozoic  and  locally  of  more  this  last  mafic,  to  by  non-marine  diorite, which  phase  hornblende  was  The  Triassic  plutons  volcanic  of and  gravity slide megabreccias.  all of these elements. In particular, the  phase: a porphyritic biotite granite. The intrusion  to amphibolite  mylonitic granitic rock.  is composed of three separate intrusive phases. The  heterogeneous biotite-hornblende  The  of greenschist  large areas of massive, gneissic, and  Intermontane  Plutonic  intruded  by  mid-Jurassic  oldest phase is a the  most  extensive  youngest phase is a garnet-muscovite granite.  created  the  bearing  porphyritic  granodiorite.  biotite The  granite  mineralogy  from  an  of  the  garnet-muscovite granite suggests that it might be of S-type. Several geochemical plots contradict this and Previous  suggests it is a highly evolved I-type magma.  geochronometry  Okanagan Metamorphic and gneisses on  that  the  Plutonic Complex and  the east that consistently yield K-Ar  for hornblende and yield  indicates  Jurassic  K-Ar  between 53 and U-Pb plutons both  45  48-50 Ma and  tectonic  boundary  dates and  the  the Intermontane Belt separates: 1) dates of 40-60 Ma,  typically 51  for biotite, from 2) intrusive rocks on  Rb-Sr  between  Eocene  volcanic  rocks,  Ma  the west that erupted largely  Ma.  dating of zircons indicates the presence of early Jurassic to east (granite  of  Anarchist  Mtn.,  ii  160Ma; gneiss  of  mid-Jurassic  Osoyoos, 201Ma;  deformed) and  west  undeformed) of the  (Similkameen  granodiorite,  170Ma; Olalla  Okanagan Valley. East of the  Syenite,  Okanagan Valley  18O-190Ma;  there are  also  mylonitic gneisses of Cretaceous age (gneiss of Skaha Lake, 105-120Ma; gneissic sill of Vaseaux  Lake, 97Ma), as  well  (Rhomb Porphyry, 51Ma). The and  early  Mesozoic  Complex and  as  metamorphosed  deformation  in both  the  the Intermontane Belt, there are  in  late  deformed  Eocene intrusives  interpretation is thaL although there are Jurassic plutons  bodies within the Okanagan Metamorphic and deformed  and  Cretaceous  to  early  Okanagan  Metamorphic  also Cretaceous and  and  Plutonic  Tertiary intrusive  Plutonic Complex that have been highly Tertiary  time.  Regional  geochronometry  summarized on  time versus blocking temperature graphs emphasizes the large (10  and  mm/yr) unroofing  rapid (1-4  Valley to near surface  km)  needed to bring the gneisses east of the Okanagan  temperatures in Eocene time. Field evidence for a low  angle  west dipping detachment fault (Okanagan Valley fault) which juxtaposes brittle disrupted Eocene and  older  rocks against  justifies comparison of the  unannealed mylonitic rocks with  Okanagan Metamorphic and  Cordilleran metamorphic core complexes.  iii  Eocene K-Ar  Plutonic Complex with  dates other  Table or Contents  LIST O F FIGURES A N D PLATES LIST O F TABLES I. INTRODUCTION . Location of Study Area Previous Field Work Acknowledgements  .  vi viii  ..  1 1 3 5  II. R E G I O N A L G E O L O G I C SETTING Okanagan Metamorphic and Plutonic Complex Eugeosynclinal Formations of the Okanagan Valley Region Plutonic Rocks West of the Okanagan Valley .. Tertiary Formations .  6 6 12 16 18  III. DESCRIPTION O F M A P UNTTS/STRATIGRAPHY PCLFCl£1%dSS€S  H«4  M W M M 1M»WH*  22  WM»»*»M«mtMMMHWttW»«««««t»M»»— #»«»««»>«»»»  Leucogneiss Cretaceous or Jurassic gniessic granitic rocks Late Paleozoic- Triassic Eugeosynclinal Rocks Oliver Ptuton .™_...™.„..........„ ....„.._™...........„....„  25 28 28 29  ..  m  Porphyritic Biotite Granite Garnet-Muscovite Granite Discussion of Geochemistry EOCCftC  Stf@t&  .  wmw«n«MWMWmmMW»ww.tn»»w«tw.w.»wmiMWM*HWW«WM  mtmtwwwwmi — —  IV. G E O C H R O N O M E T R Y Geochronometry - Previous Work ... Geochronometry - This Study . West of the Okanagan Valley .. Samples from the Okanagan Metamorphic and Plutonic Complex Summary of Geochronometry !. Discussion V. S T R U C T U R E ; Upper Plate . Okanagan Valley Fault and Related Fault Rocks Lower Plate Timing of Brittle and Ductile Deformation Discussion and Regional Implications , Conclusions  .  VI. G E O L O G I C HISTORY O F T H E S O U T H E R N O K A N A G A N REGION REFERENCES CITED  33 39 41 • » — • • « 54" 61 61 78 78 82 89 90 94 94 98 102 108 109 111 113 116  APPENDIX A - W H O L E R O C K S A M P L E LOCALITIES A N D DESCRIPTIONS  ....127  APPENDIX B - U - P B A N A L Y T I C A L P R O C E D U R E A N D D A T A  128  APPENDIX C - RB/SR A N A L Y T I C A L TECHNIQUES  149  v  11ST OF FIGURES AND PLATES Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure  1: Location Map 2: Geologic Map and Legend 3: Outcrop of gneisses 4: Stereonet of poles to fractures 5: Mylonitic gneisses 6: Foliated leucogneiss 7: Photomicrographs of leucogneiss 8: I s o c l i n a l f o l d i n lPz-Tr 9: Boudins i n lPz-Tr 10: Agmatite 11: Contact between Jpgr and Jgr 12: D i o r i t e 13: Pegmatitic D i o r i t e 14: Photomicrograph of D i o r i t e 15: General character of Jpgr 16: Photomicrograph of Jpgr 17: Photomicrograph of Jpgr 18: Photomicrograph of Jpgr 19: Photomicrograph of Jgr 20: Photomicrograph of Jgr 21: Major element v a r i a t i o n diagram 22: AFM diagram 23: Normative Q-Or-Plag diagram 24: MgO vs CaO 25: Sr and Rb vs SiO„ 26: Zr and Ba vs SiO 27,: Normative Q-Ab-Or 28: C and Di vs SiO . . . 29: Molar Al^/(CaO+Na 0+K 0) vs Rb/Sr 30: Skaha Formation 31: Photomicrograph of Eocene dike 32: Photomicrograph of Eocene dike 33: Foliated, lineated rhomb porphyry 34: Photomicrographs of rhomb porphyry 35: Location map for previous K-Ar dates 36: White Lake Basin Chronology 37: K-Ar histograms 38': Rb-Sr diagram for Osoyoos area plutons... 39: Rb-Sr diagram f o r leucogneiss .' 40: U-Pb location Map 41: Concordia diagram: 150-225 Ma 42: Photomicrograph of gneissic s i l l of Vaseaux Lake 43: Concordia diagram: 25-150 Ma 44: U-Pb sample l o c a l i t y f o r gneiss of Skaha Lake 2  2  vi  2 7 9 19 21 24 27 30 30 32 32 34 34 35 35 37 37 38 38 40 42 43 44 45 47 50 52 53 56 57 57 59 59 60 62 66 67 68 69 70 84 85 87 85  Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure  45: 46: 47: 48: 49: 50: 51: 52: 53: 54: 55: 56: 57: 58:  Closure temperature vs time Approximate u p l i f t rates Fractured Oliver pluton Stereonet of poles to fractures and dikes Low angle f a u l t s and fractures.. Map of Mahoney Lake area... Photomicrographs of mylonitic pgn. Photomicrographs of brecciated mylonite Photomicrographs of mylonites.. Asymmetric fabric i n rhomb porphyry Stereonet of poles to f o l i a t i o n s Lineations i n leucogneiss Stereonet of lineations Cross Section White Lake - Vaseaux Lake area  91 92 ....95 96 97 99 101 103 104 105 107 107 110 112 ia=poeket S e  PLATE 1  vii  I-1ST OF Table Table Table Table Table Table Table Table Table Table  1: 2: 3: 4: 5: 6: 7: 8: 9: 10:  Vaseaux Formation Structural succession from Eugeosynclinal Formations Stratigraphy of White Lake Whole Rock Chemistry Previous K-Ar data Previous and present study Previous U-Pb data U-Pb data Structural elements i n the  TABLES  Ryan (1973) Basin Rb-Sr data Vaseaux Formation  viii  11 ....13 15 17 48 63 72 79 80 106  I. INTRODUCTION  This study focuses on the boundary between the Intermontane the Canadian the  Cordillera. In southern British Columbia  Okanagan  Valley, east of which  Complex (Okulitch which  this boundary is coincident with  is the Okanagan  and Plutonic  are Carboniferous to Triassic eugeosynclinal formations, Jurassic intrusives and  The than  Columbia The  Metamorphic  et al., 1977; Okulitch, 1984) of the Omineca Belt, and west of  Eocene volcanic and sedimentary rocks of the Intermontane  more  and Omineca Belts of  Belt  Okanagan Valley and adjacent uplands have been under geologic study for a century, and most recently  the site  of many  University  of British  Ph.D. theses (Church, 1967; Okulitch, 1969; Christie, 1973; and Ryan, 1973).  purpose  of the present study has been to map an area connecting these four  thesis maps (Fig. 1), to study the Oliver  pluton with its mixed  S- and I-type  characteristics, and to carry out a regional U-Pb geochronologic reconnaissance. The result is a geologic synthesis of the southern Okanagan Valley region. Several conventions will be used throughout, these are: a) the time scale used is that of Palmer (1983); b) decay constants used for age calculations are from Steiger and Jage'f (1977); c) plutonic rock names are from Strekeisen (1976).  Location of Study Area  One reason for the continued geologic work in the Okanagan Valley is its accessibility. Highway 97 runs the length of the valley and is connected to Vancouver by  Highway 3 at its southern end, near the U.S.-Canada border (Fig. 1), and by  Highway 1 at its northern end, near Vernon. Within the study area there are many secondary or lower class roads.  1  0  2  H  119  Little.  30'  119  1961  SCALE  Figure 1: Location map of the study area; also shown are areas mapped theses and by the G.S.C..  for Ph.D.  3 An  area of 80 km  2  extending 12 km north, and 4 km east' and west, of the  town of Oliver (latitude 49° 11',  longitude 119° 3T) was mapped from June to August  1983. Mapping was done on 1:16,000 scale topographic maps enlarged from 1:50,000 NTS  maps 82E/1,2,5,6 sheets, supplemented  B.C. Ministry  of Environment)  by air photographs  (series 7580-82,7602  and 1:5,000 scale topographic maps of series 72-6T  (B.C. Ministry of Environment). Field observations were compiled onto a final 1:25,000 scale base (Plate 1).  Previous Field Work  Field work in the Okanagan Valley began i n the 1860's with a reconnaissance by G.M. Dawson (1877). This work was followed by the International Boundary Survey (Daly, 1906 and 1912), and then by Brock (1934), who studied the metamorphic rocks of  the southern  Okanagan Valley  Okanagan. The first systematic detailed was done by Bostock  from  mapping  of the southern  1927-1930 (Maps 341A, 1940;  627A,  1941a; 628A, 1941b), and Cairnes in 1934 (Maps 37-21, 1937; 538A, 1947) for the Geological Survey of Canada. This work was revised and incorporated by H.W. Little in 1958-1959 in his map of the west half of the Kettle River Sheet (Map 15-1961) (Fig.  1). A new Geological Survey  of Canada 1:250,000 scale map of the Penticton  Sheet was begun in 1983 by D. Templeman-KluiL Metamorphic and plutonic rocks east of the Okanagan Valley were studied by J.V.  Ross  and his students (Ross, 1973,  1974, 1981; Ryan, 1973; Christie, 1973;  Medford, 1975, 1973; Ross and Christie, 1979). The and  abundant granitic rock i n the Okanagan area was noted by Daly (1906),  by Brock  (1934), who attributed  metamorphism  of the Shuswap rocks to  the  emplacement of these granitic bodies. Waters and Krauskropfs (1941) study of the Colville batholith, just south of the U.S.-Canada border, is the classic on protoclastic  4 borders  of granitic  plutons. The  Colville  batholith  has  since  been  restudied  and  reinterpreted by Snook (1965), Fox et al. (1976), and Cheney (1980). Hibbard (1971) mapped  a  large  area  in northern  Washington state, primarily  within  the plutonic  granitic rocks of the Okanogan Range. Work on granitic rocks north of the border has been directed to the west of Okanagan Valley. Petb (1973 and papers on  the petrology  and  1979) and  geochronology  Petb and  Armstrong (1976) published  of the Pennask  Batholith. The  Oliver  pluton has been the subject of many U.B.C. B.Sc. theses because of its proximity to the U.B.C. field camp, and to its petrologie diversity (Matsen, 1960; Lammle, 1962; Cannon, 1966; Richards, 1968; Moore, 1970; Holtby, 1972). These were supervised by W.H.  White and A J . Sinclair and some results have been published (White et al.,  1968; Sinclair, et al., 1983). The Intermontane Belt lower grade rocks of Carboniferous-Permian to Triassic age have been the subject of two theses (Okulitch, 1969; Milford, 1984) (Fig.  1).  Other work on these rocks include those by Ross and Barnes (1972), Barnes and Ross (1975) and Read and Okulitch (1977). The  Tertiary  sedimentary and volcanic rocks of the White Lake Basin were  studied by Church (1967) (Fig. 1). He  has continued to work on these and other  Tertiary outliers in and around the Okanagan Valley (Church, 1972, 1973, 1975, 1977, 1978, 1979a, 1979b, 1980a, 1980b, 1980c, 1980d, 1980e, 1981a, 1981b, 1982, 1985; Church and Johnson, 1978; Church et al., 1983). W.H. relationship  between  (Mathews, 1981).  the Tertiary  volcanics  and  Mathews has investigated the  the underlying  metamorphic  rocks  5 Acknowledgements  The  author  would  like  to thank  R. L. Armstrong, thesis  supervisor, for  providing support, supervision, advice and enthusiasm throughout the project Thanks are also due to R. Parrish continued  for suggesting the map area and  for  guidance, insight, and enthusiasm. P. Van der Heyden, K. Scott and S.  Horsky provided laboratory assistance. J. Mortensen is thanked for his guidance, and healthy  dose  of paranoia, in U-Pb techniques and interpretation.  Assistance  from  members of the staff at the Department of Geology, University of British Columbia, most notably E. Montgomery, also merits recognition. This study benefited greatly from discussions with R. Parrish, J. Mortensen, W. H. Mathews, J. Monger, D. Templeman-Kluit, J. Montgomery, J. Fillipone, J. Logan, I. Moffat, M. Bloodgood, L. Erdman, K. McColl, and R. Friedman. Finally  the writer  would  like  to thank  J. Rublee  for patience and  encouragement, and M. Stockton, F. Borah and M. Honer for unique insights, postcards and financing his education. Natural  Sciences and Engineering  Research Council of Canada grant number  67-8841 to R. L. Armstrong provided support throughout the project  II. R E G I O N A L G E O L O G I C SETTING  The  rocks  in the  Southern  Okanagan Metamorphic and  Okanagan  can  be  divided into  four  "packages":  The  Plutonic Complex, which is mainly east of the Okanagan  Valley; late Paleozoic to Triassic eugeosynclinal formations found both east and west of the Okanagan Valley; undeformed Jurassic (and a few Cretaceous) plutons which occur mainly  west of the Okanagan Valley; and  finally  Eocene sedimentary  and volcanic  rocks of White Lake Basin, also largely west of the Okanagan Valley (Fig. 2).  Okanagan Metamorphic and  The consists  Okanagan Metamorphic and  primarily  amphibolite-grade paragneiss defined  are  by  Plutonic Complex  of  granitic  paragneiss  around  Bostock  Plutonic Complex, in the southern Okanagan,  orthogneiss  predominate  Vaseaux (1941a).  Lake These  (K-Jg (pgn  where  on  on they  feldspathic  Fig. 2);  only  locally  Fig. 2). The  best  exposures  comprise  Vaseaux  the  gneisses, with  minor  does of  Formation  mica  schist,  calc-silicate rocks and amphibolite, crop out over an area of 200 km .  Throughout the  Vaseaux Formation  foliated granitic  2  bodies  (Fig. 3). The  northwest,  west and  northeast, east granites within  there are also voluminous discordant to concordant  and  (Christie, the  Vaseaux  Formation  southwest limits with southeast, the  1973;  Vaseaux  is in fault  Little,  Formation,  Vaseaux  rocks of the  1)  from  highest numbered 5. In addition he defined two (A  sample of Christie's unit A,  Intermontane Belt  (1973) defined structurally  6  five  lowest  To  with  the  gneissic  paragneiss units numbered  intrusive units, designated A  leucogneiss of this study, was  analysis).  everywhere along its  is in intrusive(?) contact  1961). Christie (Table  contact  collected for  1, to and  B.  U-Pb  7  Figure 2: Geologic map  and legend of the southern Okanagan area.  8  LEGEND  Tertiary late Paleozoic. -Triassic  Qal  Alluvium  eTs eTcgl eTbr  Eocene sediments; non-marine ss Eocene c o n g l o m e r a t e Eocene b r e c c i a  eTv  Eocene v o l c a n i c r o c k s ; t r a c h y t e , dacite trachyandesite, andesite, basaltic andesite  lPz-Tr  l a t e P a l e o z o i c - T r i a s s i c ; greenstones, chert l i m e s t o n e , a r g i l l i t e s , minor greywacke; includes: O l d Tom, Shoemaker, Kobau, A n a r c h i s t , and N i c o l a f o r m a t i o n s  c 3  —I  0)  o>  (0  shales  paragneiss; amphibolite, feldspathic gneiss, s e m i p e l i t i c gneiss, c a l c - s i l i c a t e s , marble, s c h i s t ; l o c a l l y w i t h up to and more t h a n 50% g r a n i t i c i n j e c t i o n s  ©  o  &  •  Tertiary  lgn  leucogneiss; concordant with f o l i a t i o n s u r r o u n d i n g pgn, p o s s i b l e J-K age  eTi  Eocene i n t r u s i v e ;  Kg  Cretaceous i n t r u s i v e s ; g n e i s s i c granodiorite o f Skaha L a k e , and p o s s i b l y F a i r v i e w g r a n o diorite  K-Jg  Cretaceous or J u r a s s i c g r a n i t i c g n e i s s ; most t o Okanagan V a l l e y  syenitic  to  in  granitic  Cretaceous  Jurassic -  • •  J u r a s s i c hb g r a n o d i o r i t e (Similkameen bathol i t h and p r o b a b l e s a t e l l i t e s ) ; J u r a s s i c g r a n i t e , f o l i a t e d e a s t o f Okanagan V a l l e y ; J u r a s s i c hbbi diorite  Jgrd,Jgr,Jd  ejg  Fault;  (?) g r a n o d i o r i t i c t o h i g h l y deformed a d j a c e n t  Early  Jurassic  granodioritic  known, assumed; h a c h u r e on  Contact;  known,  assumed  upper  gneiss  plate  9  Figure 3: Photograph of outcrop of gneisses in roadcut on east shore of Vaseaux Lake, showing xenoliths of Vaseaux paragneiss in foliated granitic gneiss.  10 Christie identified and described five phases of deformation. He first  three  Formation  to  be  pre-mid-Pennsylvanian  (Okulitch, 1973). Unit A  during phase 2 deformation, and phases 4 and of Tertiary  was  by  structural  correlation  The  protolith  with  the  Kobau  interpreted by Christie to have been intruded  unit B  during or prior to phase 3. He  5, namely very broad warping on two trends and age.  interpreted the  for the  Vaseaux  Formation  considered  vertical joints, to be  was  inferred  to be  sequence of greywacke, argillite, minor ultramafic rock, mafic volcanic rock, and  a  minor  limestone (Christie, 1973). To (Table  the south, and  2) which  he  east of Osoyoos Lake, Ryan (1973) studied paragneisses  mapped as high-grade  equivalents of, and  traceable into, the  Anarchist Group of the eugeosynclinal package east of the Okanagan Valley. Ryan also mapped five intrusive bodies, which display varying degrees of deformation. Five phases of deformation were identified, the first 3 interpreted as pre-mid-Pennsylvanian, on  structural correlation with Old Tom  1972; Read and Okulitch, 1977), and body (gneiss of Osoyoos; collected  and  Shoemaker formations (Ross and  the latter two as Tertiary. The for U-Pb  analysis) was  being either pre- or syn-phase 1 deformation. Two  based Barnes,  earliest intrusive  interpreted by  of the remaining  Ryan as  four intrusives  were interpreted as post-phase 2 but pre-phase 3, a relatively late one as syn-phase 3  (Anarchist Mtn.  pluton; 152 Ma  granite; collected  by U-Pb  for U-Pb  analysis) and  and  latest (the Oliver  by R.L. Armstrong and B. Ryan, unpublished) as post-phase  3. Ryan's Rb-Sr work indicated that most intermediate and Jurassic age. The  the  late intrusives were of  Anarchist Group consists of greywacke, argillite, chert, mafic volcanic,  minor limestone; it contains lenses of ultramafic rock (Rinehart and  Ryan, 1973). Krauskopf  (1941) identified  mid-Permian  fossils from  Fox,  1972;  the middle  upper divisions of the Anarchist Group, as mapped in northern Washington  and  (which  continues north into Ryan's thesis area). Ryan chose to disregard the fossil and Rb-Sr data  to reach  his conclusions on  the ages of the deformation  based  on  structural  11  Table  1 - Description (from  Christie,  Unit  B  Foliated  Unit  A  Syn-F2 l e u c o c r a t i c  Unit  5  Biotite granulite; Hornblende granulites; A m p h i b o l i t e l a y e r s common.  Unit  4b-  Laminated  Unit  Unit  Unit  Unit  and  and  o f Vaseaux  unfoliated  massive  1973)  syn-,  granitic  Formation  to p o s t - F ^ g r a n i t i c  intrusives  intrusive.  amphibo1ites  Sheared  Contact  Sheared C o n t a c t Laminated amphibo1ites; Basal g r a n u l i t e s ; Minor impure q u a r t z i t e , c a 1 c - s i l i c a t e and m a r b l e Sheared C o n t a c t 3 - S e m i - p e l i t i c g r a n u l i t e s , h o r n b l e n d e g r e a t e r than b i o t i t e ; thin b i o t i t e schist layers. Sheared C o n t a c t 2 - Biotite-muscovite s c h i s t s with interlayered s e m i - p e l i t i c granulite; Minor m a r b l e , c a 1 c - s i l i c a t e , q u a r t z i t e . Sheared C o n t a c t 1 - Biotite semi-pelitic granulite; Biotite schist layers characteristic's with associated ultramafic lenses. 4a  12 correlations of the three early  deformation episodes (using  attitude, style, and ages  assigned elsewhere by other workers). Studies  on granitic rocks  within  the Okanagan  Metamorphic  and Plutonic  Complex generally have been related to structural geometry (Christie,- 1973; Ryan, 1973; Medford, 1973). Little (1961) distinguished two major phases: Nelson type - generally more mafic and petrographically  similar to the Nelson  Batholith  to the east, and  Valhalla type - more felsic and younger than the Nelson intrusives. Recent work, east of the study area, in the Valhalla Dome (Parrish, 1984; Parrish  et al., 1985) has  shown that in the type area for the Valhalla Intrusives identified by Little, the rocks are in part Eocene in age. This suggests that regional petrologic correlations may be misleading.  Eugeosynclinal Formations of the Okanagan Valley Region  The have various poor  eugeosynclinal  rocks (lPz-Tr on Fig. 2) adjacent to the Okanagan Valley  formation and group names (Table 3). Because of structural complexity,  exposure, scarcity of fossils, and lack  of distinctive stratigraphic horizons, no  complete, or consistent stratigraphic picture has emerged. Okulitch  (1973) interpreted  pre-mid-Pennsylvanian  the highly  on structural  deformed  correlations  with  Kobau  Formation  metamorphic  rocks  to be of the  Okanagan Metamorphic and Plutonic Complex to the east, and on its relationship to the undeformed Blind Creek limestone to the north. The Blind Creek limestone was originally interpreted to be Upper Mississippian to Lower Permian in age (Barnes and Ross, 1975) but has since  been reinterpreted  as Late  Okulitch, 1977). Ryan (1973) interpreted the Anarchist  Triassic in age (Read and Group to be older  than the  Kobau and equivalent  to the Vaseaux Formation on structural grounds. Both of these  correlations  mid-Permian  disregard  fossils  identified from  the Anarchist  Group in  Table 2  D e s c r i p t i o n of S t r u c t u r a l S u c c e s s i o n from an a r e a e a s t of Osoyoos (B. Ryan, 1973)  Unit  IX - O l i v e r  Unit  VIII  pluton  (unfoliated)  - Garnet-biotite granite, ( A n a r c h i s t Mtn. g r a n i t e -  post-F^ syn-F.; of t h i s  study).  Mu s c o v i t e-b i o t i t e g r a n i t e .  Unit  VII  Unit  VI  - Biotite  Unit  V  granodiorite, - Biotite-hornblende (Osoyoos g n e i s s of t h i s s t u d y ) .  Unit  IV  - Amphibo1i t e.  Unit  III  Unit  II  - Quartzite  Unit  I  - A m p h i b o l i t e - h i g h grade a r e a ; g r e e n s t o n e - low grade a r e a .  - Pelite  granite.  -  a r g i l l i t e, - probable  phyllite, metachert.  syn-,  schist.  14  northern  Washington (Krauskopf,  1941). Rinehart  (1977) have mapped both Anarchist and  and  Fox,  (1972), and  Fox  et al.  Kobau equivalents in northern Washington and  have also concluded that the Anarchist Group is older and the Kobau Formation unconformably or disconformably upon Anarchist Peatfield (1978) attempted eugeosynclinal formations between Rossland  B.C.  on  the east and  lies  to correlate  the Okanagan area.  His correlations, at least those pertaining to the Okanagan area, follow Okulitch (1973). Read and Okulitch (1977) documented a regional Triassic unconformity and also attempted  a correlation of eugeosynclinal formations. This unconformity  Olalla, 20 km a  pre-Late  is exposed near  northwest of the study area. Read and Okulitch (1977) recognized there Triassic  deformation  that affected late  Paleozoic rocks (Old  Tom  and  Shoemaker Formations of Little, 1961). This deformed eugeosynclinal sequence (limestone pods, greenstone, ultramafic lenses, ribbon chert, and  argillite) is overlain by relatively  undeformed Upper Triassic Nicola Group equivalents (chert pebble conglomerate, bedded limestone, and siltstone). Milford (1984) has found fossils that show the Apex Mountain Group  (formerly  mid-Carboniferous was  Old  Tom  and  Shoemaker  Formations)  ranges  in  age  on the east near Olalla to mid-Triassic on the west This sequence  intruded by the Olalla Syenite, a zoned mafic alkalic complex (Sturdevant,  (collected  for U-Pb  analysis by  R.L.  Armstrong),  south (Fox et al., 1977; collected for U-Pb The  from  lithologic  similarity  of  and  1963)  Similkameen batholith to the  analysis).  these  different  formations  (Kobau  Formation,  Anarchist Group, Apex Mountain Group) is noteworthy and, with the exception of intermediate volcanic rocks and greywackes in the Anarchist, they appear to be nearly identical. On are,  this basis, and  on lack of contradictory fossil evidence, these formations  in the present report, lumped together as a single mid-Carboniferous  to Triassic  eugeosynclinal package. They represent a complex of marine basin environments (either ocean Triassic  floor  or  interarc  time, then  or  eroded,  back and  arc basin; Monger, 1977) subsequently  overlain  by  that was  the  Late  deformed in Triassic Nicola  15  Table  3 - Eugeosynclinal  Formations  N i c o l a Group a t O l a l l a (Read and O k u l i t c h , 1977) -massive limestone -chert granule limestone -chert breccia -minor sandstone -shale, limestone  Apex M t n . G r o u p ( M i l f o r d , 1984) F o r m e r l y O l d Tom and Shoemaker format ions.  Kobau F o r m a t i o n ( O k u l i t c h , 1973)  Anarchist Group ( F o x e t a l . , 1977)  -chert -greenstone -chert conglomerate -arg i l l i t e -1imestone  -chert -greenstone -argillite -1imestone  -greenstone -chert conglomerate -chert -argillite -greywacke -1imestone  16 Group (Read and Okulitch, 1977). This is admittedly a broad interpretation but based on existing data, or its inadequacy, little more can be said.  Plutonic  Rocks  West of the Okanagan  Valley  Since the pioneering study of Daly (1912), petrologic work on granitic rocks in the southern Okanagan, north of the U.S.-Canada border, has been restricted to study of the Jurassic Pennask Kelowna  batholith (Jgrd on Fig. 2) between Princeton, Penticton and  (Peto, 1973, 1973a, 1974, and 1979; Peto and Armstrong, 1976). The Pennask  batholith is zoned more abundant  with mafic intrusives at the border and younger  felsic intrusives  towards the center. Peto argues, on chemical grounds, that the felsic  intrusives could be derived from the mafic intrusives through magmatic differentiation (Petb, 1973) and that the chemical data is consistent with the interpretation that the mafic (and felsic differentiates) could be derived from partial fusion of the Triassic Nicola Group basalts (Peto, 1979). He argues against the batholith being derived from Shuswap gneisses of the Okanagan Metamorphic Okanagan Lake  on the basis of higher  87  and Plutonic Complex to the east of  Sr/ Sr ratios in the gneisses (Petb and 86  Armstrong, 1976). The wide range in ages makes a single magmatic series unlikely. The  other major batholith in the Southern Okanagan is the Similkameen (Jgrd  on Fig. 2). Rinehart and Fox (1972) and Fox et al. (1976, 1977) have studied this complex  in some detail in Washington. It is zoned from an older, mafic and alkalic  border phase (Kruger Complex) to a more felsic core (Fox et al., 1977). K - A r dates on Similkameen biotite and hornblende are discordant but the oldest K - A r dates of 171 and 177 Ma are inferred to be the intrusive age (Engels et al., 1976).  17  Table  SHAHA  4 - Stratigraphy of White ( C h u r c h , 1973)  Lake  Basin  FORMATION Upper  Member:  Fanglomerate.  Lower  Member:  Slide  breccias,  conglomerate WHITE  LAKE Upper Lower  MARAMA  some  intercalated  and t e p h r i t e  porphyry)  FORMATION Member:  P y r o c l a s t i c rocks, volcanic breccia, s e d i m e n t a r y r o c k s and t e p h r i t e . a n d M i d d l e Members: Volcanic sandstone, conglome r a t e a n d some c o a l ; f e l d s p a r porphyry lavas, lahars, pyroclasitc rocks.  FORMATION Rhyolite, rhyodacite, basal conglomerate.  MARRON  (augite  pyroclastics,  FORMATION  Nimp i t  Lake  Kearns  Creek  Kitley  Lake  Member:  Yellow  Lake  Member : A n o r t h o c l a s e l a v a, a u g i t e l a v a s , and p y r o c l a s t i c r o c k s .  SPRINGBROOK  Member:  Trachyte  Pyroxene Member: and e s i t e l a v a . Trachyte  and rich  and  t r cah y a n d e s i t e vesicular  B o u l d er  basaltic  t r cah y a n d e s i t e  FORMATION conglomerate.  lavas.  lavas.  porphyry  18 Tertiary  Formations  The  largest and best studied section of Tertiary rocks is the White Lake Basin  section (Fig. 2). Church  (1973) divided this section into five formations (Table 4). The  following summary is taken from Church, (1973). The  maximum  thickness of this section is 2400 m. Volcanic rocks  most of the lower half, and volcaniclastic to coarse clastic sediments upper  half of the section. A  relatively  thin  comprise the  (0-60 m) conglomerate  Formation) is the basal unit This is followed by voluminous  comprise  (Springbrook  basaltic, andesitic, and  trachyandesitic Marron Formation, deposited with slight angular unconformity upon the conglomerate.  A  second  slight angular unconformity  Formation, composed of rhyodacite, rhyolite  lava  marks the base of the Marama and pyroclastic rock  and a basal  conglomerate. The first significant angular unconformity marks the base of the White Lake Formation  comprised  of volcaniclastic to arkosic sediments, pyroclastic rocks, and  rare lavas. The Skaha Formation Lower  Skaha  megabreccias  is mainly  overlies a second  coarse conglomerate  include large  (1 km ), intact 2  major angular unconformity. The  (fanglomerate) and megabreccias. "rafted  slabs"  of Old Tom  These  Formation,  Shoemaker Formation, and granite - probably Oliver pluton (Church, 1973). The upper Skaha Formation is a poorly-bedded a  high  terrain  to the southeast  coarse conglomerate The clasts  within  interpreted to be shed this  conglomerate  from  are chert,  greenstone, granite, arkose, Tertiary augite porphyry, and phyllite. The  rocks of White Lake Basin are folded, ruptured and ultimately become  chaotic along the eastern boundary of the basin. Along the western border the lower units dip eastward only moderately the  successive formations  (0-10°) but eastward and stratigraphically upward,  dip increasingly  to the east  In addition, all formation  boundaries are at least slight angular unconformities, becoming increasingly angular for younger formations. Normal faulting appears to have been active throughout deposition  19  N  Figure 4: Stereonet of poles to fractures/cleavages from the eastern border of White Lake Basin (from Church, 1973); contour intervals are >7%, 5-7%, 2-5%, 1-2%, 0.5-1.0% and <0.5%.  20 of the basin but especially at the time of deposition of White  Lake sediments, and  culminating during deposition of Skaha Formation. Along the eastern boundary, where the deformation is greatest, Church  did a detailed study of slickenside, and  orientation (Fig. 4), which shows that the predominant NNE, NW  dipping steeply both west and  east The  fracture  fracture/cleavage orientation is  slickensides point to both normal  side down and slightly obliquely normal - NNW  -  side down movement  There are several known intrusives of Eocene age in' the southern Okanagan. A few  were described and  (1983). The  Armstrong  and  Peto (1981) and  Shingle Creek porphyry (Bostock, 1966) was  (Church, 1979b). syenite. They 1973).  dated by  These intrusives are calc-alkaline  are probably related  to rhyolite  Medford  dated by K-Ar  et al.  as 52.4  to alkaline, potassic, rhyolite  in the Marama  Formation  Ma to  (Church,  Figure 5: Photograph Vaseaux Lake.  of outcrop of mylonitic  gneisses on old railway  cut west of  III. DESCRIPTION OF  Using  the broad  subdivision of rock  MAP  UNITS/STRATIGRAPHY  types developed  for the regional geology, the  stratigraphy of the thesis area can be divided into four parts: metamorphic rocks of the  Okanagan  Metamorphic  and  minor argillite, greenstone, and  Plutonic  Complex  (pgn  greywacke of probable  and  lgn); chert, limestone,  late Paleozoic to Triassic  age  (lPz-Tr); intrusive plutonic rocks of Jurassic age (Jgr, Jgrd, Jd); and Tertiary volcanic, sedimentary,  and  intrusive  rocks  (eTv,  eTs,  eTd).  This  section  will  deal  with  distribution, relationship to other units, lithology, chemical composition of the intrusive units, and finally age and correlations (Plate 1).  Paragneisses  As  (pgn)  mentioned in the previous chapter the paragneisses within the study area  were named the Vaseaux Formation by Bostock (1941a). They were studied structurally by Christie (1973) who  defined five lithologic units in a structural succession (Table 1).  In the present study these were grouped into one  unit -  pgn.  The  area of  pgn  mapped extends from Mahoney Lake in the west to the cliffs west of Vaseaux Lake in the east, and  from Covert Farms in the south to Green Lake in the north. Unit  pgn has been intruded by unit lgn, but is in low-angle fault contact with all adjacent map  units (lPz-Tr, eTv, eTs, Jd and Jpgr) to the west Within the study area the paragneisses are predominantly  amphibolite and  biotite-  banded to massive  or hornblende-plagioclase gneiss with minor mica schist and  rare calc-silicate and diopside marble lenses. The  amphibolites range  in mineralogy  from  biotite-plagioclase-hornblende to  plagioclase-hornblende amphibolites, both contain garnet The  22  grain size is also variable  23  from fine (0.5-1 mm) area  of pgn  and  to medium (2-4 mm).  are  These rocks predominate in the mapped  more abundant in the  western  exposure. Schist is subordinate to amphibolite and  and  northern  half of  pgn  tends to follow the outline of the  leucogneiss (lgn) body which is interpreted by Christie (1973) as intruding the core of a phase 2 antiform. Minor and discontinuous pods of calc-silicate and diopside marble are found within the schist unit The  schist consists predominantly  muscovite  is commonly  1973). The  present  of biotite, quartz, plagioclase, and  "in highly sheared  portions of the  garnet, but  unit"  (Christie,  schist is also interlayered with what Christie (1973) has called semi-pelitic  granulite or simply biotite-quartz-feldspar gneiss. Gneissic granitic sheets or sills are common  as  lit-par-lit  injections  metamorphic grade of these  into  the  schist  and  gneisses is, as stated by  amphibolite.  Studying  Christie, unrewarding,  the  mainly  because of lack of variation of mineral assemblages within the area. Most of the area is at the same metamorphic grade: middle to upper amphibolite facies. Christie (1973) states that sillimanite is only locally developed  at the contacts with intrusive granitic  bodies. The  paragneisses have a well developed  foliation which dips gently westward.  Throughout the pgn  unit variable shear  is evident, with locally developed mylonitic  fabrics (Fig. 5). The  amount of mylonite within pgn  generally increases structurally and  topographically upward and is most intensely developed Mahoney banded  directly below eTv  Lake. Also at this locality are exposures of very quartzites (metachert?). At  high  structural  and  and  eTs at  siliceous mylonites  topographic  levels  and  (again in  particular at Mahoney Lake but continuing southward from there to Meyers Flat) the paragneisses are increasingly altered to chlorite and  epidote with very late pyrite. This  chlorite alteration is both synchronous with the latest mylonites (epidote and deformed  in highest level  mylonites) as  well  as  post-mylonite  (pyrite  chlorite  cubes  and  chlorite breccias with mylonite clasts). These structurally highest zones of mylonite and  Figure 6: Photograph of foliated leucogneiss, from north of Coven Farms.  25 associated chlorite alteration are spatially related to fault breccias, also chloritized , and faulted eTv and eTs. The contact between these Tertiary units and underlying mylonitic pgn has been mapped in the present study as a low-angle (10°-20°) west-dipping fault zone. The  stratigraphy of the paragneisses is not distinctive enough to make any  lithologic correlations. The age of the paragneisses is only known to be older than Jurassic (based on Rb-Sr data of Armstrong on lgn). The abundance of amphibolite, and  associated metamorphosed  ultramafics (and lack of quartzite or well bedded,  continuous carbonate) suggests to the author that these gneisses can be correlated with the lower grade Anarchist Group, Kobau Group, and Apex Mountain  Group found  locally. Ryan (1973), working east of Osoyoos, traced greenschist grade Anarchist Group rocks northward  into amphibolite grade paragneisses which are identical to, but not  continuous with, paragneisses in the Vaseaux area. Whole-rock Rb-Sr dating of schists within the Vaseaux Formation, in contrast, suggests a Precambrian  age (Ryan and  Armstrong, unpublished).  Leucogneiss  (lgn)  Within the pgn unit, and containing all but the earliest fabric present in the pgn, is a granitic intrusion: leucogneiss. At the southwestern end of exposure of lgn near Covert Farms it is easily demonstrated that the lgn/pgn contact is intrusive. This contact is commonly marked by leucocratic pegmatite and the intrusive body is here (Covert Farms area) relatively leucocratic (hence  the name). This intrusion is now  sill-like with respect to the foliation and compositional layering in pgn. The lgn unit can be easily traced on both sides of Vaseaux Lake and defines a broad, domal structure (phases 4 and 5 of Christie, 1973) within the metamorphic complex. Farther to the north and east across Okanagan Valley, this unit becomes richer in biotite.  26 The overall textural character of the lgn unit is variable and ranges from weak development of gneissic foliation (Fig. 6) to well developed  horizons of lineated and  foliated mylonite. Overall the body is a homogeneous biotite granite to granodiorite with lighter colored pegmatitic borders. The large volume of small granitic sills within the pgn unit are both texturally and lithologically similar to lgn, and apparently are injections from this intrusive. The lgn unit is a medium-grained  equigranular biotite granodiorite. In thin  section quartz is ubiquitously strained, variably recrystallized, and elongated parallel to the foliation. Plagioclase and K-feldspar are rounded and commonly broken due to deformation  (Fig. 7). The plagioclase (An _ ) (all plagioclase compositions 5  optically) is commonly zoned (normal  10  determined  to complex). The only mafic mineral is biotite  (or chlorite after biotite) which defines the foliation and is generally intergranular to plagioclase and K-feldspar, rarely occuring as inclusions in K-feldspar. The pegmatitic and  most leucocratic phases contain muscovite, gray quartz, white plagioclase, potassium  feldspar, and red garnet At the structurally uppermost exposures of the leucogneiss it is commonly altered: chloritized biotite, minor epidote, and allanite. The age and correlation of lgn are debatable. U-Pb results are ambiguous. The interpretation, although not unique, is that the leucogneiss was intruded in the Jurassic and has since been subjected to a later event(s) of Cretaceous or younger age. Part of the reason  for suggesting a Jurassic intrusive age is that there are no known older  plutons in the southern  Okanagan area. In addition a whole-rock Rb-Sr errorchron  (Armstrong,  based on a fairly large sample suite is Jurassic - likely a  unpublished)  maximum age.  27  Figure 7: Photomicrograph  of leucogneiss showing extensive deformation.  28  Cretaceous  or Jurassic gneissic granitic  rocks  (K-Jgr)  Foliated and lineated granitic rocks were mapped on the southeastern margin of the study area. Christie (1973) mapped this as his unit B, and Ryan (1973) as his units VI and VII. Little (1961) mapped this unit as continuous  with much of the  granitic rocks to the east This unit is in the footwall of the Okanagan Valley fault which is its western  boundary. K-Jgr  area  was not examined  and therefore  comprises  only a minor portion of the study  in any detail.  Its composition  is biotite  granodiorite to quartz monzonite. The presence or absence of K-feldspar porphyroclasts is the main variation within this unit Both pre-  Christie and Ryan interpreted  or syn-F , although 3  this unit to have intruded post F and 2  the trend of the lineations for both  coaxial. Little correlated, on the basis of petrology, the K-Jgr  of these phases is  with Valhalla intrusives  to the east The only age determination on this unit is a K - A r biotite date of 56 Ma (Armstrong  and Mathews, unpublished), which more than likely represents thermal  resetting.  iMte  Paleozoic-Triassic  Eugeosynclinal  Exposures of lPz-Tr  Rocks  (lPz-Tr)  are restricted to south  and north of the Oliver pluton  along the western margin of the field area. This unit is in fault contact to the north with the Tertiary White Lake Basin sequence (Bostock, 1941a; Little, 1961) and in partial fault contact with dioritic rocks of the northern Oliver pluton. The southern contact of the Oliver pluton is intrusive into the Kobau Formation, and at the upper reaches of Orofino Creek the Oliver pluton again appears to have intruded lPz-Tr. Because this unit is sporadically exposed, as well as lacking any distinctive or continuous  stratigraphy, only the bounding structures  were mapped. No attempt was  29 made to decipher its internal structure, although this is known to be complex (Fig. 8; Okulitch, 1973). This unit is composed of chert or metachert, greenstone,  carbonate,  and minor greywacke. The and  metachert ranges from 90 to 98 percent quartz with very rare plagioclase,  rare to common biotite, white mica, and chlorite. The texture of the quartz is  also variable, with the development of both grain size is generally fine (0.5 mm  120° and sutured grain boundaries. The  or less) but ranges to medium (0.5-1 mm).  Carbonates are discontinuous along strike and are commonly found as pods: 10 meters or less in strike length and, 5 meters or less in thickness. Locally  these  carbonate pods are metamorphosed to calc-silicates adjacent to the Oliver pluton, and show extensive deformation (Fig. 9). The It is fault  greywacke is restricted to the northeasternmost  exposures of the map area.  bounded. The greywacke is an immature, medium  grained, well-sorted  sediment with angular clasts of mono-crystalline quartz, plagioclase, and K-feldspar.  Oliver  Pluton  The  (Jd,  Oliver  heterogeneity between  Jpgr,  mafic  by  both  granite.  This  very  compositional  agmatitic southward  biotite  garnet-muscovite  is a composite,  distinct phases. The northern  diorite, becoming porphyritic  pluton  is defined  three  Jgr)  heterogeneous intrusive differences and textural  third  granite  variations  of the pluton is predominantly  towards the contact with  biotite  body. The  is in  the main  turn  intruded  body of by  a  granite. The pluton is not neatly concentrically zoned but there is a  outer zone and a felsic core. Three distinct magmatic intrusive episodes are  inferred but they are not necessarily separated by long time periods. The  outer contact relationships of the Oliver pluton vary considerably. As stated  in the previous section intrusive contacts into lPz-Tr unit are found  on the southern  30  Figure 9: Photograph of calc- silicate boudins in IPz-Tr unit  31  border of the Oliver. Contacts to the north with lPz-Tr, and to the  east with gneissic granite  to the northeast  have all been mapped as  with pgn,  faults. Nowhere can  the Oliver pluton be seen to intrude the metamorphic rocks to the east The internal contacts between the three phases vary from a broad agmatitic zone between Jd and Jpgr (Fig. 10) to a knife sharp contact between Jpgr and Jgr (Fig. The  three  phases  (Jd,  Jpgr,  Jgr)  will  be  described  in  11). order  of  decreasing  relative age.  Diorite  (Jd)  The dioritic phase of the northern third of the Oliver pluton is also exposed on the western edge of the map area, west of Burnell Lake (Plate 1). The diorite is observed  in  various  stages of  disaggregation  and  assimilation (Fig.  12)  in  a broad  agmatitic zone at the contact with the porphyritic biotite granite. This  assimilation is  the cause for the porphyritic biotite granite  to and within  being more mafic adjacent  this agmatite zone. There are various types of agmatite:  angular, rounded, and sheared;  mostly diorite, or mostly granitic. Near its northern contact the diorite becomes increasingly foliated. Just north of Orofino  Creek  highly  deformed,  Northward in the metasediments  mylonitic,  metasediments  this deformation decreases.  that this contact is a fault, dipping gently ( < 3 0 ° )  of  lPz-Tr  are  These observations  exposed. suggest  to the north.  The presence of a large inclusion of lPz-Tr within the diorite is evidence that the _ diorite  does  in  fact  intrude  the  development of higher-grade calc-silicates  metasediments. adjacent  Supporting  to the  evidence  is  the  diorite in the  northwestern  It is difficult to  discern how  part of the area. Internally the diorite is extremely much  of this heterogeneity  heterogeneous.  is original and how much is superimposed by the  later  32  Figure 11: Photograph of sharp contact between Jpgr (on right) and Jgr (on left).  33 intrusion of Jpgr and Jgr. Texturally the diorite ranges from agmatite to gneiss. Within a single outcrop grain size ranges from fine and medium to pegmatitic (Fig. 13). Hornblende  diorite  is the most comon  composition  but can change within  meters, to biotite diorite. This heterogeneity may be original or superimposed. In thin section the diorite is variably but ubiquitously altered with the development of chlorite, epidote, and sericite. Hornblende is invariably euhedral, plagioclase (An -«) ranges from 35  euhedral, in plagioclase rich samples, to anhedral and interstitial in rocks which contain 80 percent or more hornblende (Fig. 14). Biotite content ranges from zero to generally about 10 percent and rarely reaches 40 percent Opaques are common and are in part secondary pyrite. The  age, based  on  field  relationships, is well  bracketed  (youngest age of lPz-Tr unit that it intrudes) and mid-Jurassic  between  Triassic  (age of Jgr that  intrudes it). The origin and correlation is more of a problem. It may be an intrusive equivalent to Late Triassic Nicola volcanic rocks. More likely, it represents an early mafic phase of the Early to Mid-Jurassic intrusions.  Porphyritic  The  Biotite  Granite  (Jpgr)  main phase of the Oliver pluton is a porphyritic K-feldspar granite (Fig.  15). This phase clearly intruded the diorite. The Jpgr also intruded lPz-Tr along the southern border of the pluton and is itself intruded by Jgr in the central part of the map area, northwest of the town of Oliver. A contact  between  west-dipping  the gneissic granites of the Okanagan  low angle  Metamorphic  fault is the and Plutonic  Complex, to the east, and Jpgr. The  mineralogy  of  the  Jpgr  is consistently  biotite-plagioclase  (An ) 20  - quartz- porhyritic K-feldspar (1 cm). Biotite is the main mafic mineral and, for most of the area, the only original one present The southern border of the Jpgr, the only  Figure 13: Photograph of pegmatite J d  35  Figure 15: Photograph showing the general character of Jpgr unit  36 area where hornblende  is identified  as a component (Fig. 16), is more mafic. In  addition the biotites display a deep brown pleochroism and striking pleochroic haloes (Fig. 17). Elsewhere  in the Jpgr the biotites are green and show very small or no  pleochroic haloes (Fig. 18). In the southern exposures plagioclase (25 percent, An ) is 25  euhedral to subhedral and lath shaped; K-feldspar (25 percent, microcline microperthite) is not as porphyritic as elsewhere in this unit but is still coarse (0.5 cm); quartz (25 percent) is anhedral  and strained but not recrystallized -  as it very commonly is  elsewhere in the unit Sphene, zircon, and apatite are accessory minerals, the latter two being responsible for the well-developed pleochroic haloes in biotite. This mineralogy puts the southern part of the Jpgr unit (in Strekeisens, 1976 IUGS the border  classification) on  between granodiorite and granite. The alteration in the southern Jpgr is  limited to minor saussurite development in plagioclase, minor chlorite and epidote. The majority  of  Jpgr  exposures  lack  hornblende  and  contain  saussurite/white mica+calcite as common alteration products -  chlorite,  epidote,  locally making up to  5-10 percent of the rock. The rocks with green biotite  +  alteration products are interpreted to be an  altered equivalent of the hornblende-biotite granite exposed in the southern part of the Jpgr. This alteration is spatially related to the later intruding Jgr, which is more felsic, potassic and sodic. Another Oliver  was  explanation for the mafic character of the southern  proposed  by Richards (1968). He  border  called on the assimilation  of the  of Kobau  formation as the cause. Lack of Kobau Formation inclusions along this contact and the unsuitable composition  of the Kobau  (chert, limestone, and  rare greenstone)  argue  against this hypothesis. For the Jpgr unit as a whole, it appears that alteration of an original hornblende-biotite granite/granodiorite to a biotite granite by the later intruding Jgr is the most satisfactory explanation for the limited preservation of hornblende.  Figure 17: haloes.  Photomicrograph  of brown  biotite  from  southern Jpgr, with  pleochroic  39 The zircon date  Jpgr unit is older than Jgr unit, which gives a 152 Ma  concordant  (Ryan and  the lPz-Tr unit  Armstrong, unpublished), and  younger than  U-Pb  which it intrudes.  Garnet- Muscovite  The  Granite  (Jgr)  youngest phase  of the  Oliver  pluton  is a  leucocratic  garnet-muscovite  granite. Sharp intrusive contacts are observed with the Jpgr unit. The  Jgr is the least  voluminous of the three phases. It is restricted to an exposure with the shape of a large half circle, northwest of the town of Oliver. The  only other exposures are small  circular outcrops, two of which are of mappable scale. The  field exposures, and contact  relationships suggest a very viscous, nearly solid intrusion. The this unit supports  this interpretation. The  only  highly felsic nature of  rocks that cut the Jgr are Eocene  rhomb porphyry and lamprophere dikes. The  Jgr  unit  is extremely  lithologically across its exposure.  homogeneous. It does not  The  change  texturally  or  only variability is amount of manganese stain  along fractures. The  mineralogy  of the granite is plagioclase (Ano. ) = 2  (microcline, with minor microperthite) > plagioclase,  and  K-feldspar  gray-white color. The  are  muscovite  equigranular  >  commonly  0.2  K-feldspar  garnet (Fig. 19). The  and. give  the  unit  quartz,  its characteristic  muscovite is magmatic, and euhedral (Fig. 19) (Best et al, 1974;  Anderson and Rowley, 1981; Miller et al., 1981) The and  quartz =  mm  in size. Garnets  range  garnet is red in hand specimen  from  alteration or reaction rims to completely replaced by  nearly  euhedral  with  minor  white mica pseudomorphs (Fig.  20). This unit has  given a concordant  Rb-Sr whole rock date of 157±8 Ma  U-Pb  (Armstrong  zircon date  of 152+3 Ma  and Ryan, unpublished).  and  a  Figure 20: Photomicrograph from Jgr showing partly altered garnets (top) and unaltered and completely altered garnets (bottom).  41 Discussion  of  Geochemistry  Whole rock X R F major element analyses, using pressed powder pellet technique of Van der Heyden, Horsky and Fletcher (1982), were done on a total of 26 samples. Two analyses were duplicated. Trace elements were measured on 11 samples, and Rb and Sr concentrations on 20 samples. The results are given in Table 5. The discussion of the whole rock chemistry will be broken into three parts 1) general characteristics, 2)  differences  classifications.  between It should  Jpgr  and Jgr and, 3) investigation  be stated,  however, that  of S-  because some  and 1-type  samples are both  intrusive and altered, in some cases highly altered, the data should only be used for discerning  general  trends  and associations  and should  not be used  for detailed  petrogenetic models and calculations. 1) General Characteristics General characteristics are: A - the scattered Harker  diagram  nature of the diorites on the  and A F M plot (Fig. 21 and 22) which  confirms the textural and  lithologic heterogeneity seen in the field and thin section. B - the highly felsic nature of the Jgr unit - 75 to 78 percent S i 0 Mg  the spread in Jpgr samples from and Ca. On an A F M diagram  Jgr, plot within  2  and virtually no iron or magnesium, and C  moderate to higher silica values and lower Fe, (Fig. 22) the three units, in particular Jpgr and  the trend for calc- alkaline rocks (Kuno, 1968; Irvine and Baragar,  1971). On  a  normative  Q-Or-Plag  diagram  (Fig. 23) the Jpgr  granodiorite/granite fields and Jgr plots mostly within the granite 2) Geochemical The  field.  Comparison of Jpgr and Jgr.  spread in values in the Jpgr is interpreted to be due to alteration affects  caused by the intrusion of Jgr. The samples of Jpgr which end  straddles the  are at the lower silica  of this trend are the least altered in thin section. Those samples with values  approaching  Jgr are increasingly altered - as well as spatially closer to Jgr. On a  42  wt. % 2 _ • •  Ti0  1 _  •  2  2  14 - •  1  Jd Jgr leucogneiss  T  • 3  Jpgr  A  0  Al 0  A • • •  •  A  •  •  0  A  Fe 0 2  3  A  8 -  r\ 0 —  •  A  8 -  CaO  A  A 4 -  n  MgO  •  rri  8 -  A  • •  0  •  Na 0 2  4 -  A  • •  A  •  •  o •  K0 2  4 •  0 40  •  • • I  •  A A I  50  I  I  I  60  Si0  2  I  70  I  I  80 wt  -*  Figure 21: Major element variation diagram for different phases of Oliver pluton. Also shown are two analyses from the leucogneiss.  43  Figure 22: A F M diagram for samlpes from Jpgr unit Also plotted are U-Pb samples.  Oliver pluton; note symbol  change for  44  Q  Normative  Figure 23: Q-Or-Plag diagram showing most Jgr plotting in the Jpgr plotting on boundary between granite and granodiorite fields.  granite  field,  most  45  Jpgr Jgr  3-1  2-J  MgO  H  CaO  Figure 24: Mgo vs CaO plot for Jpgr and Jgr samples.  4  wt. %  46 MgO  vs CaO  diagram (Fig. 24) these two units plot even more distinctly apart with  only two Jpgr values close to the Jgr cluster. These two samples are again the most highly altered. This separation of units on geochemical on and  trace element plots (Fig. 25 and Sr seem  suggested  to show the  characteristics also can be seen  26) (Sr, Rb, Ba, and Zr vs Si0 ). Of these Zr 2  most distinct separation. The  above, is that the  Jpgr  values which  interpretation of this, as  plot away  from  Jgr represent the  original composition of this unit (that of a Hb-Bi granodiorite), which  was  altered  when the Jgr unit intruded. These two units are not an in situ differentation sequence and may  have separate origins.  In support of this is the normative Q-Ab-Or projection (Fig. 27; Residua  System") on  which  the Jpgr and  Jgr plot in or approaching  "Petrogeny's the  thermal  trough at the experimentally determined minima for low pressure conditions (Turtle and Bowen, 1958). Taking normative An for a particular P the Ab  t  into account would shift the minimum towards Q,  (Strong, 1979; Hyndman, 1984). In general the Jpgr samples plot to  side of the fractionation curve which  potassic as  cooling  continues from  those  cooling (Carmichael et al., 1974). The  separates liquids which  which  become more  become more sodic with continued  Jgr samples generally plot on  the Or  side of  this fractionation line. This, from petrographic evidence, is to be expected. Plagioclase was  clearly a liquidus mineral for the Jpgr unit and  alkali-feldspar is euhedral to  sub-hedral in Jgr samples, suggesting it was a liquidus mineral. 3) Comparison with S- and I-Type Granites In recent years work on granites has focused on whether the source rock of sedimentary  (S) or igneous  (I) origin (Chappell and  White,  1974). The  was  Jgr unit  (containing both garnet and muscovite, as well as having very high silica composition) appears to fit into the  S  category. In an  observations several plots were made which granitic rock. These plots show: A  -  effort to substantiate the petrographic demonstrate the S or I character of a  degree of alumina  saturation with respect to  47  • Jpgr • Jgr  500J  400  300  Sr 200J  100 J  E a  0^  300-1 250J 200. Rb 150H  •• •  100-1 50 J  48  ' 52  i 56  i 60  i 64  r  -  68  SiCL Figure 25: Sr and R b vs S i 0  2  for Jpgr and Jgr samples.  72  76  80 wt. %  Table 5 (See Appendix A for procedures and error estimates). WHOLE ROCK DATA FOR PORHYRITIC BIOTITE GRANITE SAMPLE* S102 T102 A 1203 Fe203 MnO MgO CaO Na20 K20 P205 H20  227  205  73 .74 72 87 0 . 10 0 .25 13 . 18 12 .97 1 38 2 67 0 . 17 0. 16 1 44 0 69 1 37 2 15 4 59 3 64 3 26 3 77 0 07 0. 10 0 93 0. 49  275.1 69 .45 0 28 13 .90 2 95 0 17 1 83 2 .74 4 15 3. 23 0. 1 1 1 .19  275.2 66 66 0 39 13 73 4 37 0. 18 2. 88 3 22 4 24 2 99 0. 16 1 .19  205  203  WHOLE ROCK DATA FOR DIORITE 71  72 .74 70 05 74 .64 0 . 27 0 31 0 .07 13 .02 14 35 12 83 3 .05 3 18 1 .31 0 .06 0 06 0 12 1 .38 1 35 0 ,47 1 .37 2 27 2 51 4 .43 3 19 3 43 3 38 4 04 3 97 0 14 0. 16 0. 06 0 49 0. 56 • 0 73  245 67 .47 0 46 14 49 4 45 0 17 2 . 25 3 27 2 85 3 93 0, 20 0. 46  CATION NORMS 0 OR AB AN DI HY MT IL HM AP C  27 . 40 22 51 41 . 73 4 .24 1 .74 1 06 0 19 0. 14 0. 84 0. 15  SAMPLE* S102 T102 A1203 Fe203 MnO MgO CaO Na20 K20 P205 H20  207  178  261.1  46 .97 49 .86 56 .29 1 . 70 1 . 10 0 .78 15 .04 18 .43 13 70 14 .25 10 88 8 93 0 17 0 .20 0 18 7 .79 5 17 8. 92 9 07 7 . 36 5 66 1 90 3 .09 2. 53 1 05 1 38 2 49 O 93 0 68 0. 14 1 13 1 .86 1 .10  261.2  140  45 .90 0 .91 12 .91 12 .44 0 28 15. 94 7. 36 1 44 2 67 0 15 1 50  41 17 2 .08 13 65 13 .45 0 . 16 16 55 9. 39 1 44 1 .39 0. 22 1 .20  15 .58 9 48 20 .51 36 62 1 1 68  8 . 17 1 .33 26 .49 35 .83 14 . 76  CATION NORMS 32 .66 20 39 29 .30 10 .57 4 .18 1 88 0 38 0. 30 O.35  23 51 19 36 38 . 1 1 9 .76 2 65 4. 1 1 1 .87 . 0 40 0. 23  18 .56 17 .90 38 .88 9 .58 4 .44 7 77 1 98 0 55 0 34  30 91 19 57 33 28 9 54 0 51 3 79 1 82 0 35 O.02 0. 21  25 87 24 25 31 32 1 1 .59 4 12 1 91 0..44 0. 34  o. 16  28 87 23 . 7 1 40 28 3 41 2. 46 0. 08 0 14 0 10 0. 83 0. 13  23 68 23 .66 26 . 12 15 .20 8 . 10 2 08 0. 65 0 43 o 08  0 OR AB AN OL DI HY NE MT IL HM AP C  0 39 6 .45 a .41 17 . 78 28 . 73 30 .55 33 . 10 1 84 7 93 27 77 23 48  4 .67 14 .78 23 .07 18 .64 6 92 28 . 17  3 18 2 46  2 75 1 58  2 .37 1 09  2.1 1 2 .46 1 .25  7 .00 3 .07 2 88  2 02  1 .47 0. 09  0 29  0. 31  0. 46  131 380 479 15 26  138 294 557 1 1 31  52 489 611 11 25  62  51  46  TRACE ELEMENTS (ppm) Rb Sr Ba Nb Y Zn Zr  150 212  146 348 670 12 17 126  163 365  154 396  150 347 592 15 12 47 126  180 389 817 14 11 47 1 18  135 294  204 462  TRACE ELEMENTS (ppm) Rb Sr Ba Nb Y Zn Zr  37 821  34 756 924 14 23 133 11 1  oo  WHOLE ROCK DATA FOR GARNET MUSCOVITE  GRANITE WHOLE ROCK DATA FDR U-PB  SAMPLE* S102 T102 A 1203 Fe203 MnO MgO CaO Na20 K20 P205 H20  234  2 0 9 . 1 209 .2  263  1B2  9  263  73 .63 76 67 78 13 76 22 75 .34 75 . 15 75 .49 0 08 0 OS 0 . 03 0. 0 3 0 .04 0 08 0 .04 13 75 12 . 45 1 178 12 .73 13 .40 13 .33 12 77 1 ,00 , 1 04 . 1 .08 1 09 1 .39 O. 88 0 91 0 .04 0 17 0 . 10 0 03 0 .02 0 .03 0 .07 0 36 0 07 0 .26 0 . 21 0 .09 0 .27 0 37 1 . 11 1 .09 1 03 0 17 0 . 75 0 .92 0 .79 6 88 4 . 30 3 42 3 20 3 64 3 68 3, 91 3 .04 4 . 25 4 37 5 10 4 76 4 71 4 95 0 . 04 O. 03 0 . 01 0 . 02 0 . 03 0 03 0 04. 0 92 0 . 33 0 . 03 0. 42 0. 44 0 .23 0..42  SAMPLE* S102 T102 A1203 Fe203 MnO MgO CaO Na20 K20 P205 H20  156  95  74 3 0 0 04 13 89 0 . 38 O 12 0 . 24 2 32 5 92 2 . 41 0 05 0 33  74 .25 0 . 14 13 19 1 .66 0 17 O 67 1 59 3 77 4 14 0 07 0 . 33  66 0 14 3 0 0 5 6 2 0 0  43 32 97 21 18 95 12 . 28 . 18 18 19  38 76 27 93 48 63 16 20 05 15  12 12 55 6 10  17 77 97 13 26  CATION NORMS  CATION NORMS  0 20 . 24 31 .61 37 .46 33 .60 31 .62 30 .96 29 .55 OR 17 .83 25 .33 26 .29 30 .65 28 48 28 . 14 29 .53 AB 56 .56 39 .01 31 . 32 29 .29 33 . 15 33 .47 35 .52 AN 2 10 4 . 26 5 25 3 93 5 .31 2 .67 DI 1 .. 16 0 .50 1 78 HY 1 .64 0 25 0.. 76 0.. 73 0. 14 0 20 MT 0 17 0 .01 0. 08 IL 0 04 O. 04 0 04 0 03 0..05 0. 06 0. 06 HM 0 . 50 0 73 0 . 77 0..77 0. 98 0. 59 AP 0 . 08 0 . 06 0 .04 0 . 06 0 . 06 0 02 0 . 08 C 0. 03 0 . 78 0. 03 SP 0..04 0 . 10 0. 07 ACMITE 2.76 NAMETASILO.53 -  0 OR AB AN 01 HY MT IL HM AP C  TRACE  TRACE Rb Sr Ba Nb Y Zn Zr  ELEMENTS 312 45  (ppm) 136 181  136 181 684 14 8 17 60  141 201 254 4 3 18 69  221 209 401 12 12 24 65  213 185 349 14 16 36 64  141 201  Rb Sr Ba Nb Y Zr  24 83 14 16 52 91 4 17 3 44 0 0. 0. 0.  20 06 13 10  ELEMENTS 63 409  30 24 34 6 0 1 0 0. 1 0.  179  1 .88 O 44 O 37  SAMPLES 246 68 .22 0 30 13 .83 3 .44 0 . 17 1 57 3 68 5 08 3 21 0 19 0 29  90  300  74 . 1 1 5 3 . 77 0.84 0 . 14 14 .33 17.OO 1 .46 6.50 0 02 0.11 5. 29 0.45 2 79 5 02 4.61 4 . 74 2 .06 5.03 0.02 1 OO 0 . 26 0.20  17 18 45 5 9 0 1 O  32 30 82 98 12 22 7 1 4 1 71 12 31 43 28 0 84 59 0 83 88 42 0 03 1 02 O 40 O .04  29 30 9 10  . 36 36 96 58  7 22 2 40 1 16 2 07  (ppm) 151 350  44 1004  125 640  51 787 1362 6 9 57  141 3313 3492 90 27 4 12  •  Jpgr  • Jgr •  Jd  150-  Zr  •  •  •  100-  E a a.  A  A  •  A  800-  Ba 600-  •  •  A •  A A  • •  400-  • 40  1  1  50  60  70  Si0  Figure 26: Zr and Ba vs S i 0  2  2  for Jpgr and Jgr samples.  80  51 normative corundum or diopside, versus S i 0 Na 0  +  2  K 0 ) versus Rb/Sr 2  molar Al 0 /(CaO 2  3  Both  + Na 0 + 2  (Fig. 28); and B - molar Al 0 /(CaO  2  2  ratio (Fig. 29). Rocks K 0) > 2  with  3  +  normative corundum and  1.1 are considered typical S-type granites.  Jpgr and Jgr units have samples which contain (<1 percent) normative  corundum. Otherwise the samples are scattered mainly with low to moderate normative Di.  On  the molar  Al 0 /(CaO 2  +  3  Na 0  +  2  K 0 ) vs Rb/Sr 2  characteristic is again the separation (in Rb/Sr terms  of S and I classification  values) between  the Jgr samples  the most  striking  these two units. In  are all (except one) below 1.1,  suggesting a highly evolved I-type magma. The Jpgr unit straddles this dividing line at 1.1,  with  several  values  up  to  1.2  molar  Al 0 /(CaO 2  3  +  Na 0  +  2  K 0). 2  Petrographically the Jpgr unit is not of S-type character. An alternate explanation for the slightly aluminous character of this unit and very likely considering the mineralogy, is  amphibole  fractionation  causing  alumina  enrichment (Cawthorn  and Brown 1976,  Cawthorn et al, 1976). In summary it appears that neither of these granitic bodies is truly of S-type. The  Jpgr unit has high molar Al 0 /(CaO 2  3  +  Na 0 2  +  K 0 ) values due possibly to 2  amphibole fractionation and the Jgr unit which has S-type petrographic characteristics, does not plot neatly in S-type granite fields on either C - D i or molar Al 0 /(CaO 2  Na 0 2  +  3  +  K 0 ) scales. Jgr may be a highly differentiated I-type magma or it could 2  be the result of fusion of eugeosyclinal or lower crust rocks rather than pelitic schists and therefore does not clearly display S-type geochemistry.  52  Q  Normative wt. %  Figure 27: Q-Ab-Or for Jpgr, Jgr, and Jd samples. Boundary curves and temperature contours for water saturated liquids at P = 1.0 kb, from Carmichael et al. (1974).  5-i  Jpgr Jgr  4H  3 H  Di 2-4  1H  l-type S-type 1H  68  72  70  74  76  SiO.  Figure 28: C and Di vs S i 0  2  for Jpgr and Jgr samples.  78  54  Eocene  Strata  (eTv, eTs,)  Eocene  volcanic  northwestern were  part  rocks  of the area.  and coarse They  examined in detail by Church  clastic  represent  sediments  are  exposed  in the  a small part of this study area but  (1973) and therefore  the internal stratigraphy is  well defined. The volcanic rocks within the study area include the Matron Formation and  local occurrences  of rhyodacite  Clastic sediments present rocks  are  found  at  and pyroclastic  rocks of the Marama Formation.  are the Skaha Formation. In the area studied the volcanic  lower  stratigraphic,  structural  and topographic  levels  than the  sediments. The contact between the volcanics and overlying sediments has been mapped (Church,  1979b,  and the present  study)  as a fault directly north  and northwest of  Mahoney Lake, but elsewhere in the White Lake Basin Church has demonstrated this contact to be an angular unconformity. The contact between the volcanics and lPz-Tr to  the south  is also a fault, as is the contact between  the Eocene  rocks and the  Vaseaux gneisses to the east The  volcanic  flows  exposed  west  of Mahoney  Lake  are  extremely  altered,  fractured, and faulted. They can be related to Church's detailed stratigraphy only on the basis of texture (relict "Clot Porphyry", Church, 1973). The phenocrysts, except for feldspars,  are invariably altered  beyond  recognition.  These  volcanics  are andesite  to  trachyandesite in composition; the groundmass is a mosaic of quartz and feldspar. The alteration  consists  of calcite,  quartz,  and opaques (oxidized pyrite, and fracture-filling  iron oxides). The Skaha sediments are coarse conglomerates,  and form the youngest unit in  White Lake Basin. Church describes them as fanglomerate, shed from highlands which lay  to the southeast  granite.  Church  (1973)  The predominant reports  clasts  phyllite clasts  Vaseaux Formation. The Vaseaux  are chert, which  greenstone,  he interprets  and unfoliated  as coming from  Formation is not seen at such a low metamorphic  55 grade, therefore south, or an  the  phyllite is interpreted to come from  Kobau Formation to  the  equivalent unit of lPz-Tr age. Church reports the presence of Vaseaux  clasts but this could  not be  confirmed in the present study. Various highly strained  rocks from the lPz-Tr formations make up the greatest percentage of clasts within the Skaha. At Green Lake this unit is faulted and are pebble to boulder (1 m)  fractured. The  clasts, in a sand matrix,  size (Fig. 30). Bedding or stratification is not evident at  this locality but from the east side of the Okanagan valley, looking west, large-scale bedding can be discerned, dipping 25° The  White  Lake  volcanic  to the east rocks,  which  include  both  andesitic  and  alkali- trachyandesitic compositions can be correlated with other Eocene volcanics in  B.C.,  Washington, and  near  Montana. Andesitic rocks have been well studied  Kamloops by Ewing (1981a) and and  B.C.  Dikes  Tertiary dikes are the to  exposure  frequency. The m  alkaline volcanics are known from south central  north-central Washington as well as from Montana (Church, 1973).  Eocene  due  further north  and  a  most conspicuous in the  marked  dikes are 1-2  m  color  wide and  contrast  but  Oliver pluton. This is partly also because of  can be followed for no  truly  greater  more than 50-100  along strike. They occur locally in swarms, particulary near Madden Lake. They  invariably are fractured and commonly altered. Mineralogically these dikes are identical to the lower volcanic units within the Marron  Formation.  clinopyroxene  Rhombehedral  zoned  anorthoclase  (Fig. 31). These dikes generally are  is  common,  altered but  a  few  were observed. These show in thin section delicate pyroxene zoning and slightly altered olivine (Fig. 32). These dikes flows of the Marron Formation.  were apparently  as  is  unaltered  zoned ones  unaltered  feeders to the  or  basal  56  O  1.3  • Jpgr  -J  • Jgr  CM  + O  + 234  1.2 H  CM  CO  +  S-type l-type  1.1  o CO  o  CO CM  0.99  H  « 0.98 -| O  0.4  0.5  0.6  "1  r~  0.7  0.8  0.9  1.0  1.1  Rb/Sr  Figure 29: Molar Al 0 /(CaO 2  3  + N a 0 + K 0 ) vs Rb/Sr for Jpgr and Jgr samples. 2  2  57  Figure 30: Photograph of fractured outcrop of Skaha Formation, west of Green Lake.  Figure 31: Photomicrographs of Eocene rhomb porphyry dike.  58 The proximity  number of dikes found in the pgn and lgn units is low considering their to the White  Lake Basin. A  metamorphosed  and deformed  dike bearing  rhomb-shaped anorthoclase phenocrysts in the pgn and lgn just north of Covert Farms (Plate 1) has for many years been suspected to be an equivalent to the basal rhomb porphyry  of the Marron (Ross, 1974). This dike cuts the compositional layering and  foliation in the pgn and lgn at a very low angle and is itself strongly foliated and lineated  (Fig. 33). Metamorphism  pull-aparts of anorthoclase  is expressed  as garnet  and biotite  and clinopyroxene, as well as in the matrix  Clinopyroxene appears to be reacting to form hornblende;  growth in (Fig. 34).  the matrix is a recrystallized  mosaic of quartz, feldspar, biotite and chlorite. A U-Pb date on zircon from this sill gives a concordant date of 51 Ma (this study). Ross (1974) has reported several other dikes/sills  of similar  composition  and texture within the pgn and lgn units. The  number of dikes or sills within the metamorphic rocks is probably low  but many have been overlooked  rendered  not anomalously  because the metamorphism and deformation has  them almost indistinguishable from the pgn, except where well exposed. Only  undeformed dikes are rare in the metamorphic rocks.  Figure 33: Photograph of foliated and lineated rhomb porphyry from within the pgn unit, north of Covert Farms area.  Figure 34: Photomicrographs of metamorphosed and deformed rhomb porphyry' showing garnet and biotite growth in pullaparts of pyroxene (top) and feldspar (bottom).  IV. G E O C H R O N O M F X R Y  In the Shuswap Metamorphic Complex  of southern B.C. an extensive area of largely  pre-Eocene plutonic and metamorphic rocks yields K - A r dates of 45-55 Ma. Many authors have  observed and discussed this regionally extensive pattern of reset dates  (Armstrong, 1974, 1982, 1983, 1985; Ross, 1974; Medford, 1975; Miller 1975; Fox et al., 1977; Mathews,  and Engels,  1981, 1983; Parrish, 1979; Okulitch, 1984; Price,  1985; Price, et al., 1981; Archibald et al., 1984). The explanations include high heat flow and tectonic unroofing. One purpose of the present study was to determine the geologic nature (abrupt or transitional) of the western boundary of this reset terrane. Another was to use the U-Pb method post-kinematic  granitic  rocks  to obtain original ages for pre-, syn-, and  to ascertain  the time(s) of deformation  within the  metamorphic complex.  Geochronometry  -  Previous  Work  Geochronometric studies in the Okanagan region began with reconnaisance K - A r work Rb-Sr  on Cenozoic volcanic rocks (Mathews, 1964). Since that time both K - A r and studies have been done for a number of theses and research projects. This  section summarizes the results of those studies (Fig. 35; Table 6). The early K - A r work done by Mathews (1964), Baadsgard et al. (1961) and White et al. (1968) established that volcanic rocks equivalent to those in White Lake Basin are Eocene, about 50 Ma old, and that intrusive rocks west of the Okanagan Valley are Mesozoic. Geochronology of the White Lake Basin was reported by Church (1970, 1973, and 1980d), and is summarized in Figure 36. Church (1975, and 1979a), Ewing (1981a, and 1981b) and Mathews (1981) have documented other Eocene volcanic  61  62  119 3 0 '  KNA-1004 KNA-1315 KNA-1348  3-20  JR-1 3-10 3-22 Inkaneep *1 80-55 Inkaneep +2  ^Anarchist phyllite| 78-84 78-85  SCALE  Figure 35: Location map of previous K - A r analyses.  63  Table 6 - Previous K-Ar Data Data from 49°-49°50'; 119°10'- 120° Sample //  Rock Type  Mineral  Date Ma*  Latitude  Longitude  G.S.C. analyses (Wanless et a l . ,1979; Stevens et a l., 1982) 76-1 78-82 78-83 78-84 78-85 80-54 80-55  gneiss gneiss gneiss gneiss gneiss gneiss gneiss  Hb Bi Ms Bi Hb Hb Ms  48.4 47.8 45.5 45.6 63.5 48.8 59.4  49°39'50 49°17.5'  M  119°36'10" 119°30'  1!  49°00'40" it 49°39'50" 49°09'45"  II  119°24'15" II  119°36'10" 119°30 15" ,  Analyses done for B.C.M.E. M.P.R. by U.B.C.; except * done by Geochron Labs (Church, 1970, 1979, 1980, 1982; Church et a l . , 1983). *Kitley BNC-78-1 KNA-1004 BNC-78-2 BNC-70-5 KNA-1315 KNA-1348 SUM-1006 OK-12 LYN-001  trachyte breccia dacite porphyry tephrite dacite(?) rhyolite dacite trachyte syenite  Bi Bi WR Bi WR Bi Mica WR Bi Bi  52.9 52.5 44.2 52.4 48.4 52.9 47.7 47.9 52.7 53.0  49°20.6' 49°18.5 49°54.75' 49°28.52' 49°18.75' 49°49.65' 49°48.45' 4 9°35' 49°33' 49°23'  119°44.3' 119°37.5' 119°39.5' 119°38.83' 119°37' 119°44.4' 119°43.40' 119°40' 119°52' 119°20.4'  49°36.7' 49°43.9' 49°44.5' 49°39.2' 49°42.6' 49°25.2' 49°03.5' 49°16.5' 49°26.6' 49°36.6* 49°42.5' 49°42.8' 49°15'  119°34.6' 119°31.3' 119°31.0' 119°33.8* 119°36.0' 119°47.2' 119°38.5' 119°31.2' 119 34.5' 119°47.8' 119°48.8' 119°16.5' 119°10.5'  Analyses from Medford, 1975. 1-50 1-148 1-150 1-160 1-178 3-3 3-7 3-10 3-13 3-18 3-20 3-21 3-22  dike gneiss gneiss dike gneiss diorite Kruger syenite paragneiss gneiss diorite grd. gneiss grd.  WR Hb Hb WR Hb Bi Hb Hb Hb Bi Bi Bi Bi  48.2 49.3 50.7 49.8 51.8 188 173 61.0 53.3 168 135 52.7 52.7  cont inued  *A11 dates corrected to decay constants recommended by Steiger and Jager (1977).  64  T a b l e 6 (con't) Analyses from Read and O k u l i t c h , HP-1 dike HP-2 dike O l a l l a Gd . g r d .  Hb Hb Bi  1977. 153 172 155  49°18*31" 49°18'09" 49°18'43"  119°47'39" 119°47'48" 119 48'34"  49°16.7'  119°29.0'  0  A n a l y s e s from Ross, 1974. JR-1 JR-1 JR-1 JR-2A JR-1 A M-15  rhomb p o r . rhomb p o r . rhomb p o r . Marron Fm. Marron Fm. pegmatite  WR Bi Hb WR WR Ms  42.4 45.3 48.4 42.2 44.3 48.9  rl  It  it  It  49°18.0' 49°17.7' 49°15.9'  119°36.6' 119°35.2' 119°32.8'  A n a l y s e s from White e t a l . , 1968, and S i n c l a i r e t a l . , 1984. W-65-1 W-65-2 W-65-3 W-65-4 W-65-5 W-65-6 W-65-7 W-66-2 W-66-5 W-66-7 W-67-1  syenite grd. granite granite granite granite a l t e r a t ion dike granite granite alteration  Px-Hb Bi Bi Bi Bi Ms Ser Bi Ms Bi Ser  154 113 120 84 104 141 138 53.8 146 101 115  49°3.2' 49°12' 49°12' 49°12.2' 49°12.1' 49° 1.1.4' 49°11.8* 49°11.8' 49°11.5' 49°10' 49°13.0'  119°41.7' 119°38.2' 119°35.9' 119°35.4' 119°34.85' 119°33.3' 119°33.5' 119°33.6' 119°35.5' 119°35' 119°35.9'  Unpublished a n a l y s e s from U.B.C. (1-3, c o l l e c t e d by Mathews and Armstrong; 4 c o l l e c t e d by Mathews; 5 and 6 c o l l e c t e d by S o r e g a r o l i and C h r i s t o p h e r ) . Inkaneep #1 Inkaneep #1 Inkaneep #2 Anar. Mtn. S74-6-12.3 S74-7-3.1  granite " gneiss phyllite q t z . monzo. grd.  Bi Ms Bi WR Hb Bi  87 146 56.4 53.6 171 112  Hb  49 10'35"  119 29'30"  49 09'50"  119 29'50"  49°0r45"  119°2r20"  49°06' 49°01'  119°48' 119°55'  184  49°16.5*  119°50'  Bi Hb  50. 118.  49 01.4' 49°3.0*  119 22.5*  Hb Bi Hb Bi  181 73 175 72  Similkameen b a t h o l i t h  K-Ar r e p o r t e d by: O k u l i t c h e t a l . , 1977: Olalla  syenite  Fox e t a l . , 1975 and 1977: Osoyoos #2 g n e i s s L-704 grd.  119°44.2'  south o f 4 9 ° : L-618 L-618 L-301 L-301  grd. grd. alkalic border  65 basins and  erosion remnants, north and. east of the southern Okanagan Valley. Engels  et al. (1976) dated equivalent rocks south of 49°  as Eocene as well. K-Ar  White et al. (1968), Roddick  et al. (1972), Medford (1975), and  dated  rocks  the  extensive  granitic  west of  the  Okanagan  Fox  Valley as  studies by  et al., (1976) Jurassic  and  This duality of dates (Fig. 37) is in contrast to unimodal Eocene K-Ar  and  mid-Cretaceous.  fission track dates for dikes, pegmatites 1975)  and  gneissic granites (Ross, 1974;  Medford,  east of Okanagan Valley, from within the Okanagan Metamorphic and Plutonic  Complex. Several Geological Survey of Canada K-Ar from east of both Osoyoos and (Wanless et al., 1979;  analyses (Table 6) on  gneisses  Vaseaux Lake, also show this pervasive Eocene event  Stevens et al., 1982). These dates on  metamorphosed plutonic  rocks have been interpreted to be thermal reset ages, and not the intrusive age. Published Rb-Sr data of Peto and Armstrong (1976) and Medford et al. (1983) documented Jurassic (and possible Paleozoic) intrusives to the west of Okanagan Valley with  87  Sr/"Sr initial ratios below 0.705. Armstrong and Petb (1981) as well as Medford  et al. (1983) demonstrated the presence and  Siwash  Creek  porphyries) and  of both Eocene (Shingle Creek, Trout Creek,  Paleocene  (Whiteman  Creek  stock) high  level  intrusives west of Okanagan Lake. A  wealth  of  unpublished  Rb-Sr  data  (Table  7)  exists  for  the  southern  Okanagan, and by far the majority of this data is on orthogneiss, paragneiss and schist from the Okanagan Metamorphic and Plutonic Complex. Much of this work was by  Ryan  (Ph.D. thesis, 1973)  supplemented  this.  The  results  at U.B.C. and from  (unpublished) has obtained a 157+8 Ma  this  in recent years ongoing  study  whole rock date on  R.L.  are  Armstrong  varied.  done has  Armstrong  the Oliver pluton, on  the west side of the Okanagan Valley. In addition three variably deformed intrusive bodies, mapped  by  Ryan  (1973) northeast  of Osoyoos from  within the  Okanagan  Metamorphic and Plutonic Complex, yield Jurassic isochrons with large errors (Fig. 38).  66  K-Ar Date (Ma) upper  Skaha Formation fanglomerate, slide b r e c c i a s  lower upper  48.4  52.5  White Lake Formation sediments, pyroclastic  rocks  mid-lower  Marama Formation  47.9  rhyolite, rhyodacite Park Rill Member Nimpit Lake Member  Marron Formation  andesite, trachyandesite basaltic andesite, anorthoclase, augite porphyry flows  Kearns Cr Member Kitley Lake Member Yellow Lake Member  Springbrook Formation conglomerate  Figure 36: K - A r chronology for White Lake Basin.  52.7 52.9 52.9  67  K-Ar dates from the Okanagan Metamorphic and Plutonic Complex Data from LAT 4 9 ° - 49°50' L O N G 119° 10' - 120°  K-Ar dates from west of the Okanagan Valley  Volcanic Rocks  Plutonic Rocks  J~l 20  80  100  120  140  n 160  180  I 200Ma  Figure 37: Histograms of K - A r dates from plutonic rocks and volcanic rocks west of the Okanagan Valley, and metamorphic rocks east of the Okanagan Valley.  68  Osoyoos Area Plutons  Figure 38: Osoyoos.  Rb-Sr  diagram  for  four gneissic  granitic units  A  U N I T VII  A  UNIT  of Ryan  VI  (1973), east of  69  Leucogneiss 0.707 - \  .  WHOLE ROCK  A  FELDSPARS FROM L 2  0.704H  0.2  0.4  87  Rb 86 Sr  Figure 39: Rb-Sr diagram for leucogneiss.  0.6  0.8  1.0  70  DP300, rhomb porphyry Ol-Sy, Olalla Syenite  DP246, Similkameen batholith  SCALE  Figure 40: U-Pb  sample locality map for both previous work and the present study.  71 One  of these (granite of Anarchist Mtn.)  study. The  other orthogneiss (Unit V)  interpretable  whole  rock  orthogneisses  yield  mostly  was  from  collected  Ryan's Ph.D.  isochron. Mineral-whole Paleocene-Eocene  for zircons in the present  rock  area  isochrons  dates. The  did not from  leucogneiss  yield  these  body  an  same  north  of  Covert Farms, within the present study area (and sampled for zircons), gives a Jurassic Rb-Sr errorchron (Fig. 39; Armstrong, unpublished). Rb-Sr  data  for paragneiss  from  the  Okanagan  Metamorphic  and  Complex do not produce whole rock isochrons, but all the mineral-whole  Plutonic rock pairs  yield Paleocene-Eocene dates. Some paragneiss samples have highly radiogenic strontium, supporting the interpretation that the protolith is Precambrian  in age (Ryan, 1973;  and  Armstrong, unpublished). Previous U-Pb the  Oliver  granite  work (Table 8; Fig. 40) in the Okanagan has  pluton (152+3; Armstrong  from  Medford's  concordant at 68 ± 2  Ma;  Ph.D.  Ryan, unpublished), and  (1973) area  south  of  on  Kelowna  a (3  gneissic fractions  analaysis by Geological Survey of Canada). Fox et al. (1976)  reported a late Cretaceous Washington, 50 km  thesis  and  been done on  U-Pb  date  from  the  south of the present study area.  Okanogan  Dome  in north-central  Table 7 Previous Rb-Sr Analytical Data* Sample  Description  Sample Suite: SH SH SH SH SH SH SH SH SH SH SH SH  L M R S U W K C D E A T  S9  muscovite  Sample Suite: VL VL VL VL VL VL  1 2 3 5 6 7  49°15.13' 49°15.14' 49°15.0' 49°15.14' 49°15.20' 49°15.14' 49 15.11' 49°15.19' 49°15.20' 49°15.25' 49°15.08' 49°15.17'  119°32.92' 119°33.16' 119°33.0' 119°33.25' 119°33.27' 119°33.16' 119°32.73' 119°32.27' 119°32.25' 119°32.22' 119°32.33' 119°33.25'  310 211 106 292 704 193 328 913 763 647 476 393  150 22.8 84.3 78.7 99.4 64.4 51.8 71.3 83.2 99.9 108 109  1.400 0.312 3.69 0.78 0.409 0.968 0.457 0.226 0.315 0.447 0.659 0.805  0.7209 0.7066 0.7273 0.7228 0.7073 0.7185 0.7201 0.7073 0.7079 0.7083 0.7218 0.7145  166  116  2.039  0.7673  117 38.9  149 310  3.683 23.21  0.7467 0.7640  0.208 0.182 0.135 0.245 0.332 0.073  0.7045 0.7051 0.7055 0.7062 0.7065 0.7062  Paragneiss, Covert Farms (Ryan, 1973)  schist, Vaseaux Formation  SIO SmlO  Longitude  Paragneiss, Covert Farms (Armstrong)  paragneiss amphibolite paragneiss paragneiss hb granulite paragneiss paragneiss hb d i o r i t e hb d i o r i t e hb d i o r i t e paragneiss paragneiss  Sample Suite:  Latitude  49°15'10" "  119°33 25" ,  "  Paragneiss, Vaseaux Lake roadcut (Armstrong)  gneiss gneiss gneiss gneiss gneiss gneiss  49°16.7' " " " " "  119°31.0' " " " " "  608 667 1021 683 534 793  43.7 41.9 47.5 57.7 61.3 20.0  P r e v i o u s Rb-Sr A n a l y t i c a l Sample //  Description  Sample S u i t e : Gl  Gbl P2 Pm2 Pml2  SHI SH3 SH5 SH6 SHF SHG SHN SHO SHP SHQ Leucol Leuco2 Leuco2--I Leuco2--IV Leuco2--M Leuco2--B  leuco-  " " " " " " mylonite mylonite granod. g n e i s s it  119 29*40"  49 04' 53'  119  49°515'  119 28.5 *  27*57"  777 .3  28.9  0.1075  0.7044  262.2 519.6 139.3 17.98  256. 2 34. 0 232. 0 462. 2  2.825 0.1892 4.819 74.7  0.7058 0.7082 0.7106 0.7511  27. 5  0.130  0.7048  647 519 521 693 594 662 657 1275 680 623 616 320 790 43.0 104  55. 7 78. 1 83. 3 31. 3 47. 8 27. 6 79. 8 38. 1 66. 1 23. 2 39. 0 5. 2 167 124 267  0.249 0.436 0.463 0.131 0.233 0.121 0.351 0.086 0.281 0.107 0.183 0.047 0.611 8.33 7.41  0.7055 0.7055 0.7056 0.70515 0.7048 0.7046 0.70585 0.70475 0.7051 0.7042 0.7053 0.7050 0.7057 0.7120 0.7098  3402  151  0.129  0.7061  (Armstrong)  49 15.45'  119  49 15.43' 49°15..41' 49°15..40' 49°15..40' 49°15..40' 49°15,.43' 49°15..44' 49°15.,60' 49°15..60' 49°15..40' 49°15..42'  119 33.35' 119°33.40' 119°33.40* 119°32.28' 119°32.29' 119°33.41' 119°33.42' 119°33.48' 119°33.48' 119°32.36' 119°33.35'  33.35'  heavy f e l d s p a r light feldspar muscovite biotite + chlorite Rhomb Porphyry, Covert Farms  a n o r t h o c l a s e augen gneiss  ppm Sr  (Ryan, 1973)  49 18'0'  L e u c o g n e i s s , Cover Farms  garnet gneiss  Sample S u i t e : Rhomb P  Longitude  P l u t o n i c Rocks; Vaseaux Lake a r e a  Synkinematic Q t z monzonlte s i l l biotite pegmat i t e muscovite muscovite  Sample S u i t e :  Lat l t u d e  Data  49°14.97'  609  (Armstrong) 119°33.00'  Previous Rb-Sr Analytical Data Sample //  Description  Sample Suite:  Latitude  Longitude  ppm Sr  „, ppm Rb  87„ ,86„ Rr/ Sr  87 ,86 Sr/ Sr  145.6 3.354 568.1 207.1 293.0 13.45  0.7156 0.8577 0.7206  Anarchist Pelite (Unit III of Ryan, 1973)  51 Sbl Sml  pelite biotite muscovite  49°04'59" " "  119°28'07" "  109.4 8.05 63.0  52 Sb2  pelite biotite  49°04'57" "  119°28'00" "  270.0 21.14  122.0 416.2  1.308 57.15  0.7139 0.7413  55 Sb5  pelite biotite  49°04'10"  119°25'17"  182.1 13.74  54.2 223.0  0.861 47.08  0.7115 0.7287  S4 Sb4 Sm4  pelite biotite muscovite  49°05'12"  119°25'42"  "  "  86.7 8.70 41.38  126.9 4.356 550.0 184.4 247.0 17.31  0.7250 0.7937 0.7335  56  pelite  49 02'15"  119°22'55"  273.1  142.3  1.511  0.7278  57 Sb7  pelite biotite  49°or45"  119°20'53"  164.3 66.34  80.4 233.8  1.416 10.21  0.7131 0.7177  58  pelite  49°or40"  119°20'40"  122.4  89.1  2.107  0.7136  165 181 309 166  4.9 7.7 41.0 22.0  0.086 0.123 0.384 0.384  0.7058 0.7060 0.7088 0.7071  Sample Suite: Al A2 A3 A4  O  Anarchist Amphibolite (Unit I of Ryan, 1973)  greenschist facies amphibolite facies " "  49°0r00" 49°03'15" 49°05 17" 49°06'35" ,  119°20'20" 119°25'13" 119°28 26 119°30 58" ,  1  M  P r e v i o u s Rb-Sr A n a l y t i c a l Sample //  De s c r i p t Ion  Sample S u i t e : Fl  F2 F3 F4 F5 F6 F7 F8 F9 *BDRgn *BDRap  DI Dml D2 Dm2 D3 D4 D5  49 00'40"  49°0r53" 49°0r33" II II  s e p a r a t e body ti  gneiss def. a p l i t e quartz monzonite  qtz.  monzonite  biotite muscovite s e p a r a t e body alaskite  Sample S u i t e :  Longitude  ppm Sr  „ ppm Rb L  8 7 ^ .86„ Rb/ Sr  87„ ,86„ S r / Sr  g n e i s s o f Osoyoos ( U n i t V o f Ryan, 1973; * a n a l y s e d by Armstrong)  b i granod g n e i s s  Sample S u i t e : El E2 Eb2 Em2 E3 E4  Latitude  Data  quartz monzonite  q t z . monzonite muscovite q t z . monzonite muscovite q t z . monzonite  49° 04'37" 49°04'34" 49° 04'50" 49°05'45" 49°08'40" 49°09'20" 49°0.65* 49°0.65'  119 20*43" 119°23'00" 119°24 50" 119°25'15" 119°27'20" 119°29'20" ,  119°3r04" 119°26'50" 119°26 55" 119°24.0' 119°24.0' ,  487.3 459.8 549.3 536.2 458.9 442.8 455.3 459.7 616.5 515 119  63.2 74.4 56.3 69.1 63.7 71.1 74.6 76.9 54.7 68.4 239.0  0.376 0.468 0.296 0.373 0.401 0.487 0.474 0.484 0.257 0.384 5.82  0.7074 0.7054 0.7050 0.7066 0.7045 0.7054 0.7048 0.7070 0.7045 0.7045 0.7158  637.8 310.1 192.0 223.0 740.2 5.72  103.8 0.471 281.5 2.63 840.0 12.69 658.3 8.55 79.0 0.309 344.1 181.8  0.7081 0.7128 0.7220 0.7182 0.7088 1.166  101.0 36.38 99.77 42.09 133.8 257.7 243.5  175.1 5.022 615.8 49.23 5.238 180.5 596.6 41.2 160.6 3.474 92.72 1.041 1.188 100.0  0.7186 0.7622 0.7168 0.7562 0.7134 0.7083 0.7079  (Unit VI o f Ryan, 1973) ,o, 49 08'15" 49°02'44"  119 30'40' 119°23'53'  49 04'55" 49°02'48"  119 28'40* 119°20'38'  (Unit V I I o f Ryan, 1973) 4 9° 08'20"  119°26 35*  49 08'15"  119 26'25"  49 08'10" 49°07'50" 49°07'40"  119°2r35"  ,  119°26'17" 119°21'30"  Ul  Previous Rb-Sr Analytical Data Sample //  Description  Sample Suite: Cl Cbl C2 C3  01 01-m W-65-7  HP2 HPl Gd-Olalla Horn Silver  Oliver pluton  granite muscovite muscovite from Gypo mine  Sample Suite:  Longitude  ppm Sr  ppm Rb  8 7  Rb/ Sr 8 6  8 7  Sr/ Sr 8 6  late quartz monzonite (Unit VIII of Ryan, 1973)  qtz. monzonite biotite altered, saussuri t i z e d , fractured qtz. monzonite  Sample Suite:  Latitude  49 11'35"  119 28'00'  49 11 '02' 49 12'10"  119 27'30"  194 1. 0 449.4 456.0  51.1 804.0 151.7  0.142 5.181 0.963  0.7070 0.7169 0.7092  119 26'30"  1003.0  66.4  0.192  0.7119  119 33'07"  10.6 4.1 12.9  (Armstrong) 49 H'29" " 49°ir45" 0  119 33* 31'  314 1199 1813  87.56 1057.0 448.0  0.9014 3.253 1.744  O l a l l a area plutons (Armstrong)  hb andesite porph hb andesite granodiorite hb monzonite  „o. „ . .. 49 18*09" 49°18'31" 49°18'43" 49°03.4'  .. n  119 47*48" 119°47'39" 119°48'34" 119°41.5'  555 510 533 1638  29.3 29.5 125 142  0.158 0.167 0.679 0.251  0.7071 0.7058 0.7059 0.7045  —i  Rb-Sr Analytical Data from this study Sample //  Description  Longitude  ppm Sr  ppm Rb  49 12.1  119 31.2  49 11.6'  119 34.0'  395 365 462  154 163 204  1.127 1.293 1.276  0.7094 0.7098 0.7091  DP156 plag« gneiss gneissic s i l l of Vaseaux Lake  49°18.0'  119 31.5'  409  63  0.446  0.704 6 6  DP95 gar-bi granite granite of Anarchist Mtn.  49°03.5'  119 21.1'  350  151  1.246  0.7106  DP179 hb granod. gneiss gneiss of Skaha Lake  49 24.5'  119 34.0'  1004  44  0.129  0.7095  DP246 hb granodiorite Similkameen batholith  49°02.0'  119 41.5'  640  125  0.564  0.7056  DP90 b i gneiss leucogneiss  49 18.5'  119 30.2'  772  51  0.190  0.7061  Sample Suite: DP275.1 DP275.2 DP245.2  Oliver pluton  hb-bi granod.  Sample Suite:  Lat itude  8 7  Rb/ Sr 8 6  8 7  Sr/ Sr 8 6  (Jpgr) 1  U-Pb samples  (See Appendix C for procedures and error estimates). —i  -J  78 Geochronometry  -  This  Study  Detailed mapping done west of the Okanagan Valley by Bostock (1940, 1941a, 1941b) and east of the Okanagan Valley by Ryan (1973), and Christie (1973), along with  the regional  map  of Little  (1961) provided  a basis for the U-Pb study  undertaken (Fig. 40). Two samples from  west of the Okanagan Valley fault and six samples from  the Okanagan Metamorphic and Plutonic Complex east of the fault were dated using analytical procedures given in Appendix B. A summary of analytical data and dates is given in Table 9, with complete  analytical data and rock descriptions in Appendix B.  All U-Pb errors stated are at a 2 a level (95% confidence limit).  West of the  Okanagan  Similkameen batholith  The  Valley  (DP246)  Similkameen  batholith is a mesozonal hornblende  granodiorite (Fig. 2). It  crosscuts structures in the lPz-Tr unit and is itself undeformed (Bostock, 1941a; Fox et al,  1977).  Fox et al. (1977) published  hornblendes of the Similkameen  K - A r dates  of 171 and 177 Ma for  batholith. To confirm this a sample for U-Pb analysis  was collected from the northern border of this batholith, southeast of Keremeos (Fig. 40). Two zircon fractions (Table 9) were analysed (Fig. 41). The coarse nonmagnetic fraction  is concordant  at 170 ± 2 . Ma, and the fine magnetic  fraction  is slightly  discordant at 169±2 Ma. The zircons appear to be magmatic, and are colorless to slightly pink, euhedral with occasional opaque inclusions. The discordance, which can be attributed to minor low temperature lead loss, is not considered significant because at the 9 5 % confidence level the ages for the two fractions overlap. The U-Pb date of 170+2 Ma  confirms the K - A r date  and represents the crystallization age of the  79  Table 8 Previous U-Pb Geochronometry  Sample #  Fraction  Dates Ma 2 0 6  Pb/  2 3 8  u  2 0 7  Pb/  2 3 5  u  2 0 7  CAa76-3 foliated hb granod.  0-176E  Oliver pluton  Source  Pb/ ° Pb 2  very coarse  68.3 68.5 73.4  coarse nonmag.  67.8 68.0 72.0  fine magnetic  67.2 67.1 64.4  6  87.3 100.0 151.9 +/- 2 152.1 +/- 3 156.2 +/- 15  G.S.C. Wanless and Loveridge (unpublished; Okulitch, pers. comm.)  Fox et al.,1976  Ryan and Armstrong, unpublished.  Table 9 U-Pb isotopic data Isotopic abundance^ Pb 206 = 100 weight (mg)  size <u)  U rad. Pb (ppm) (ppm)  207  208  204  Measured 2 0 6  Pb  2 0 6  2 0 4  pb  2 3 8  Dates (Ma) +/- 2o e r r o r  2 , 3  Pb  ° Pb  u  2 0 7  2 3 5  Pb u  2  7  2 0 6  Pb  DP156; gneissic s i l l of Vaseaux Lake 45-75 45-75 75-150 >150  M NM NM NM  37.4 0.3 38.5 3.9  1474 3594 1272 1620  20. 5 49. 4 17.4 22. 6  4.8808 4.8454 4.8855 4.9296  3.0853 1.7174 1 .7445 1.8944  0.0002 0.0085 0.0006 0.0028  38,426 2,005 20,105 17,459  95. 7±1 .0 95. 8±1 .2 95. 6+1 .0 97. 2 + 1 .0  97. 3+1 .0 94. 4±1 .8 97. 3+1 .0 99. 0+1 .2  14. 2 27. 8 14. 5  5.07 94 5.2043 5.0651  7.6381 8 .6363 7 .1205  0.0016 0.0105 0.0005  19,421 5,384 19,468  200. 2+2 .2 201. 7+2 .2 200. 5±2 .2  201. 8±2 .0 203. 0±2 .8 202. 2±2 .0  220. 7±8.4 218. 2±22. 221. 9±6.0  4.9749 4.9660  4 .2912 4 .2654  0.0015 0.0003  36,116 34,856  159. 7±1 .8 160. 9±1 .8  160. 6±1 .6 162. 0±1 .6  172. 9+5.8 176. 9±4.8  137. 3±8.2 59. 7±38 136. 9±5.8 142. 3±12.:  Oso; gneiss of Osoyoos 45-75 M 37.6 45-75 NM 0.6 75-150 NM 27.5  4 64 891 476  DP95; granite of Anarchist Mtn. 45-75 M 75-150 NM  31.9 39.0  7852 3983  185 94. 6  DP246; Similkameen batholith 45-75 M 75-150 NM  36.4 35.2  633 488  17. 3 13. 6  5.4754 13 .7505 5.9722 13 .4675  0.0338 0.0700  2,555 1,000  168. 6±1 .8 169. 9±1 .8  169. 7±1 .8 169. 8±2 .0  185. 3+13. 168. 6±17.l  1111 1132 1080 954 845  18. 5 18.8 18. 33 17.4 15. 5  5.3178 5.4198 5.3411 5.5007 5. 1965  0.0032 0.0017 0.0032 0.0032 0.0091  11,877 21,819 12,864 11,107 6,774  112. 9±1 .2 6+1 .? 114. 7±l .2 .4 122. 2 + 1 120. 7±1 .4  122. 6+1 .2  316. 3±6.4 368. 6+6.0 326. 1±5.8 393. 1+5.6 223.8±7.0  DP90; leucogneiss 45-75 45-75 45-75 75-150 >150  M 31.6 M 14.9 NM 16.4 NM 16.4 NM 9.5  4.4765 4 .3973 4 .5535 5 .0930 1 .6540  m.  ]±]  125. 1±1 .2 136. 5+1 .4 125. 8±1 .2  U-Pb Isotopic data Isotopic abundance Pb 206 = 100 size (u)  weight (mg)  U rad. Pb (ppm) (ppm)  207  204  208  Measured 206 204  Dates (Ma) +/- 2o error 206  Pb Pb  207.  Pb  238.  235,  Pb  2,3 207 206.  Pb Pb  DP179; gneiss of Skaha Lake 45-75 M 75-150 NM  34.2 33.0  308 381  4.7 6.1  4.9393 10.0325 4.9574 9.4778  0.0064 0.0064  5,885 4,233  98.7+1.0 104.3+1.2  99.7±1.2 105.4±1.2  121.6+13.2 130.1+16.0  1100 1923  9.5 16.1  5.8566 18.0336 5.6498 15.7190  0.0658 0.0661  799 617  51.5+0.6 50.9+0.6  53.4±0.8 50.6+1.8  142.2+25 36.7+40  1341  51.2  5.1738 46.3786  0.0060  9,279  185.612.0  189.2±1.8  234.6±6.2  DP300; rhomb porhyry 45-75 75-150 NM  1.6 1.4  O l a l l a Syenite 45-75  NM  6.7  , 206„, ,204^, 15.54; Pb/ Pb: 17.75. ^ r r e c t e d for blank with composition = P b / P b : 37.00; P b / P b : 2 207 206 Isotopic composition of common Pb i s based on Pb/ Pb age and i s derived from the growth curve of Stacey and Kramers (1975). -9 ?T8 = 0. 155125 x 10 V y r ; X 0.98485 x 10 /yr; U/ U = 137.88. 238 235 2 0 8  2 0 4  M = Magnetic fraction, (magnetic at 1.5A and 0.5  2 0 7  2 0 4  c  c /  side t i l t on Franz); NM = Nonmagnetic.  82  intrusive.  Olalla Syenite (Ql- Sy) A R.L.  sample of the Olalla Syenite Complex (Sturdevant, 1963)  Armstrong, and  hornblende  collected  dated in this study (Fig. 41). More work is required, but  fraction (fine) from this rock is slightly discordant at 185-189 Ma. K-Ar  was  date on this body of 184 Ma  by one  This supports a  from Queens University reported by  Okulitch et al. (1977).  Samples from the  Two VIII). One  Okanagan  Metamorphic  and  Plutonic  Complex  samples were collected from B. Ryan's Ph.D.  thesis area (his Units V  and  (the gneiss of Osoyoos, unit V) is exposed at the lookout above Osoyoos  on Highway 3. Ryan interpreted it to be possibly syn-Fi, but definitely pre-F , 2  and  the oldest granitic unit in the succession.  gneiss of Osoyoos (Oso) Three zircon discordant at 201.5 The  fractions (Table 9) were Ma  (Table 9 and  analysed. A l l three are  Fig. 41.) the  207  very  slightly  Pb/ Pb dates are 219±20Ma. 206  zircons appear to be magmatic, and are transparent, pink, generally euhedral with  common cloudy Jurassic). The  cores. The  intrusive age  is interpreted to be  discordance, though slight, may  lead loss from a latest Triassic pluton. A  be  201.5 ±2.2  Ma  (Early  ascribed to inheritance, or to slight  geologic maximum age limit for this pluton  is mid-Permian to early Triassic, the age of the Anarchist Group which is intruded by the body. A  minimum age is 150 Ma,  provided by a Rb-Sr whole rock date on  an aplite from the Osoyoos lookout (Table 7; Armstrong, unpublished). Both K-Ar Rb-Sr mineral dates from this gneiss are Eocene.  and  83  granite of Anarchist Mtn, (PP95) The  other unit from  Ryan's thesis area is a slightly  foliated garnet-biotite  granite (Unit VIII of Ryan, 1973). This unit is interpreted by Ryan to have been emplaced late in the deformation  (post F  and pre- or syn-F ). Two  2  3  fractions of  zircon (Table 9) were analysed and plot very near (within two sigma error) concordia at 160.2±1.8 Ma and 161.4±1.8 Ma. The and  207  Pb/ Pb ages are 173 Ma and 177 Ma, 206  probably represent an upper age limit (Fig. 41). The zircons, interpreted to be  magmatic, are generally  euhedral  but highly  fractured, and cloudy. The discordance,  though very slight, is probably attributable to inheritance, particularly with the hint of S-type character of the intrusive. The interpretation is that 160.512 Ma represents a minimum crystallization age. Three samples were collected from Christie's thesis area at Vaseaux Lake: 1) A crosscutting,  but foliated,  intrusive  sill  (gneissic  sill  of Vaseaux  Lake);  2) The  leucogneiss body north of Covert Farms; 3) the rhomb porphyry sill at Covert Farms. The  latter two are also within the area mapped for this study.  1) gneissic sill of Vaseaux Lake (PP156^ This gneissic sill (Fig. 42) was collected 0.5 km east of Vaseaux Lake where it crosscuts the paragneiss but is itself foliated and lineated. Four zircon fractions (Table 9) from dates  this rock plot between 95.5 and 97.21 1.2 ( Pb/ U ages). The 206  for the fine magnetic,  approximately  140110  Ma. The  essentially concordant, although age;  coarse  238  207  Pb/ Pb 206  nonmagnetic, and very coarse fractions are  fine  nonmagnetic  slightly  handpicked  all  fraction (0.3 mg) is  above concordia, at 95.811.2 Ma ( Pb/ U 206  238  Fig. 43). The zircons are transparent, slightly pink, euhedral, with no visible  cores; they are interpreted to be magmatic. The minimal spread of these analyses, with large variation in uranium and lead significant (not >  content, suggests that lead loss is probably not  5 percent) and that  the intrusive age for this gneissic sill is  Figure 41: Enlargement of 150-225 Ma  section of U-Pb  concordia diagram.  Figure 44: U-Pb dikes(?).  sample locality for gneiss of Skaha Lake, note deformed mafic  86 probably on the Early-Late Cretaceous boundary.  2) leucogneiss (PP9Q) The leucogneiss north of Covert Farms has not yielded an interpretable zircon array cloudy  after cores  analysing and  between 112 Ma  five  fractions. The  apparent overgrowths. and 135 Ma  zircons are clear, euhedral, with The  points are all discordant  common  and scatter  (Fig. 43). Unlike most discordant zircons, these do not  lie along a single line but instead plot in a cluster. A probable interpretation (there are an infinite number of interpretations) is that the leucogneiss body was intruded in the Jurassic, based on the Rb-Sr errochron (Fig. 39; Armstrong, unpublished), and was subjected to later metamorphism. This would have to have occured in post-Aptian time based on the discordance pattern of the zircons. The problem is compounded  by a  small inherited component and possible later low temperature lead loss.  3) rhomb porphyry  (DP3QQ)  The rhomb porphyry  body (as described in Chapter 3) was collected from the  north edge of Covert Farms (Plate 1). At this locality the rhomb followed for 1 km  as it cuts through  porphyry  can be  the paragneiss and leucogneiss. It is deformed  and metamorphosed. Two zircon fractions (both very small amounts) were analysed. The zircons  are slightly  to deeply  pink  colored, equant, and barrel  shaped. They are  interpreted to be magmatic. The fine zircon fraction from this rock plots very nearly concordant at 52 ± 1 Ma, a second (coarser) fraction is concordant at 51 ± 1 Ma (Fig. 43). The slightly discordant point probably the concordant date  of 51+1  deformed rhomb porphyry  Ma  indicates traces of xenocrystic zircon, and  is interpreted to be the crystallization age. The  is therefore equivalent in age to the basal rhomb  porphyry  flows of the Marron Formation, as has long been inferred but never proven, and in accord with U-Pb  ages of Coryell syenites dated by Parrish (pers. comm., 1985).  oo  88 gneiss of Skaha Lake The  (PPP9)  other unit sampled east of the Okanagan Valley, but not in Ryan or  Christie's thesis areas, is a  large gneissic granodiorite mapped  crosscutting the paragneiss but itself foliated and 44) is on Skaha Lake, 5.5 km Two  zircon  fractions  lineated. The  by  Little  (1961) as  outcrop sampled (Fig.  south of Penticton. were  analysed, both  are  slightly  discordant: the  magnetic fraction discordant at 99.5±1.2 Ma  ( Pb/ Pb age  =  122± 12  coarse nonmagnetic discordant at 104.5+1.2 Ma  ( Pb/ Pb age  =  130+16 Ma) (Fig.  207  207  J06  206  Ma),  fine the  43). There are no cores visible in the zircons, which are clear, and generally euhedral. This is interpreted as a Cretaceous intrusive that was  subsequently metamorphosed. The  discordance could be due to lead loss, in which case the Cretaceous dates represent a minimum age for the intrusive. If lead loss was significant then this intrusive could be as old as Jurassic. The  discordance of zircons from  the leucogneiss north of Covert Farms (in  addition to an inherited component), the gneissic sill of Vaseaux Lake, and the gneiss of Skaha Lake, is inferred to be due  to metamorphism and  deformation. During the  metamorphic event the zircons either lost lead or overgrowths of new (or  both). The  zircon developed  latter interpretation is favoured based on the nonmetamict character of  the zircons and work done by Martinson (1972, and 1978) and Williams et al. (1984). Either interpretation is viable however, given the present data. The growth episode would have to be in post-middle Cenomanian time.  lead loss or zircon  89 Summary  of  Geochronometry  The K - A i woik in the southern Okanagan demonstrates that the volcanic rocks of White Lake Basin, and equivalents, plutonic rocks west of the Okanagan Okanagan  are Eocene and that the intrusive age  for  Valley is generally Jurassic. The gneisses of the  Metamorphic and Plutonic Complex  have had an Eocene thermal overprint  however, and therefore their original ages are not obtainable by K - A r techniques. The  Rb-Sr  work  done  in the Okanagan  has documented  Jurassic and  Paleocene- Eocene intrusives to the west of the valley. In addition unpublished data of Armstrong and Ryan indicate Jurassic intrusives both east and west of the Southern Okanagan Valley. This data also shows that, like K-Ar, the Rb-Sr mineral dates on the Okanagan Metamorphic and Plutonic Complex are Paleocene and Eocene. The results of the U-Pb geochronometry reveal: -Early  Jurassic  or Late  Triassic intrusive within  the Okanagan  Metamorphic and  Plutonic Complex (gneiss of Osoyoos). -Middle to Late Jurassic intrusives both east (granite of Anarchist Mtn., deformed) and west (Oliver pluton, Similkameen batholith, and Olalla Syenite, all undeformed) of the Okanagan Valley. -Jurassic or Cretaceous intrusives (leucogneiss north of Covert Farms, gneiss of Skaha Lake, gneissic sill of Vaseaux Lake, all deformed) within the Okanagan Metamorphic and Plutonic Complex. -Eocene intrusive (rhomb porphyry, deformed) within the Okanagan Plutonic Complex.  Metamorphic and  90 Discussion  A plot of closure temperature versus age (cooling curve) has been constructed for the gneisses east of the Okanagan Valley using K-Ar, fission track, and Rb-Sr muscovite data (Medford, 1975; Armstrong, unpublished) (Fig. 45). Also plotted are zircon ages and closure temperatures from the rhomb porphyry, gneissic sill of Vaseaux Lake, and gneiss of Skaha  Lake. Closure temperatures for K - A r and fission track  dates are from Harrison (1981) and Harrison and McDougall (1980, and 1982). (For an alternate  assessment  of the K - A r closure  temperature  concept  in amphiboles, see  Deutsch and Steiger, 1985). For zircons, estimates of closure temperatures are from Parrish and Roddick (1985), and Mattinson (1978). Rb-Sr muscovite-whole rock closure temperatures are estimated at 550° ± 50° C (Wagner et al., 1977). A Rb-Sr muscovite-whole rock date of 58 Ma from the leucogneiss north of Covert Farms indicates that the gneisses were below approximately 600° C by this time. The K - A r hornblende dates (with closure temperature of approximately 530° C) cluster with minimal spread around 51 Ma. Both the K - A r biotite and fission track sphene dates have considerable spread, both in age and error; the fission track apatite is well constrained (closure temperature =  105° C) between 44 and 48 Ma. This data alone  dictates that the gneisses of the Okanagan Metamorphic  and Plutonic Complex cooled  through 400° C in 3-10 Ma. Assuming  a geothermal gradient it is possible to calculate the depth of the  gneisses at 51 Ma, and at 45-48 Ma  (Fig. 46), and thereby estimate uplift rates  during that time interval. Using 50° C/km, the gneisses would have been uplifted from 11 km (at 51 Ma) to 2 km (at 45-48 Ma); this implies a 2-4 mm/yr uplift and erosion rate. Using 30°C/km, a more reasonable estimate (being the present-day Basin and  Range geothermal gradient according to Eaton, 1982), the gneisses would  have  been uplifted from 18 km (at 51 Ma) to 3 km (at 45-48 Ma); this implies a 3-5  91  Closure Temperature vs Time Data Lat  from  T  Long  T T  i i  4 9 ° - 49°50'  i  119°10' - 120°  U-Pb  -  Zircon  I  I  1 1  1 R b - S r  I  II  I  II T T T T T  '  n • •••• i i 11111  i  X  I I T, | U. 1  ±  I 11 I  T  T  Muscovite  T T  K-Ar Hb  F.T.  Sph»n»  K - A r BI  •~i5S-5I  0  I  I  20  I  I  40  I  F.T.  I  60  Apatite  I  P-  80  Time M a  Figure 45: K - A r , fission track, and muscovite Rb-Sr mineral dates versus their respective blocking temperature for gneisses of the Okanagan Metamorphic and Plutonic Complex; sources: Ryan (1973), Medford (1975), and Armstrong (unpublished).  Approximate Uplift Rates  Geothermal Gradient  Depth of Gneisses at 51 Ma  Uplift Rate a) for 3Ma interval b) for 5Ma interval c) for 10Ma interval  50 C/km  11 km  a) 3 mm/yr b) 1.8 mm/yr c) 0.9 mm/yr  30 C/km  18 km  a) 5 mm/yr b) 3 mm/yr c) 1.5 mm/yr  Figure 46: Uplift rates for the gneisses of the Okanagan Complex using assumed geothermal gradients.  Metamorphic and Plutonic  93  mm/yr uplift and erosion rate. In contrast the granitic rocks west of the Okanagan Valley were well below the blocking temperature for hornblende and biotite by 100 Ma, indicating a depth of only 2 to 3 km. Recent work on uplift of the Himalaya reports rates not much higher than 1 mm/yr and generally much less (Zeitler, 1985). Bradbury and Nolen-Hoeksema, (1985) calculate uplift rates for the Lepontine Alps of between 1 and 2 mm/yr. Taken at face value the Okanagan data require either exceptional erosion rates (filling unknown basins), exceedingly high geothermal gradients, or a tectonic explanation.  V. S T R U C T U R E  The  most important structural feature within the study area is a low-angle (10-20°)  west-dipping fault (named the Okanagan Valley fault by  DJ.  Templeman-Kluit, 1984).  In the upper plate of this fault the rocks were deformed in a brittle fashion whereas in the lower plate the rocks were deformed ducuiy, and metamorphic fabrics. This  chapter  will  structure; 2) Okanagan Valley fault and  be  divided  show a complex overprint of  into  four  parts  1)  upper plate  related fault rocks; 3) lower plate structure;  and 4) timing of deformation.  Upper  Plate  The  late Paleozoic to Triassic formations were isoclinally  to the  deposition  Within  the  of the  Upper Triassic Nicola  Group  study area this deformation predates the  folded (Fig. 8) prior  (Read and  Oliver  Okulitch, 1977).  pluton  which  is itself  unfoliated. Other than the results of this Triassic deformation the predominant structure seen in the upper plate rocks is brittle fracturing. Within observed  in  the  Oliver  pluton,  and  to  the  north  the study area, this is best  in  the  Eocene  volcanic  and  sedimentary rocks of White Lake Basin. Fractures are. pervasively developed within the Oliver pluton (Fig. 47). In addition there are distinctive topographic lineaments which contain fault gouge but, in the absence of identifiable markers, any of offset is uncertain. Tertiary dikes fracture system (trend N40E, dip Fracturing and  within the  Oliver pluton  60-90NW; Fig. 48)  and  are  sense and  amount  commonly intrude  a  themselves fractured.  faulting in the Oliver pluton is more intense approaching the Okanagan  Valley fault; in addition, fractures become predominantly low angle (Fig. 49). Ultimately this intense fracturing produces a monolithologic  94  breccia (Fig. 47). A  highly fractured  Figure 47: Photographs of fractured and brecciated Oliver pluton.  96  Figure 48: Stereonet of poles to fractures and Eocene Okanagan Valley Fault. Triangles=dikes; dots=fractures.  dikes  in  upper  plate  of  Figure 49: Photographs of low angle faults and fractures in Oliver pluton.  98 and  faulted section has been documented by Church (1973) in the southeastern White  Lake Basin. In fault  addition to the pervasive northeast-trending northwest-dipping  set there  north-dipping  are less  abundant  but possibly  large  fracture and  westnorthwest- trending,  faults in the upper plate. The largest one i n the map area  is  in  Orofino Creek and can be followed for several kilometers to the westnorthwest It separates the Oliver pluton from lPz-Tr rocks. Another north-dipping fault, just north of the map area, separates lPz-Tr from White Lake Basin volcanic rocks. These faults are  not well understood,  but are restricted  to the upper plate. They  have normal  displacement, and may be partly responsible for the large megabreccias/landslide blocks of lPz-Tr and Oliver pluton in the Skaha Formation.  Okanagan  The map  Valley  Fault and Related  Fault  Rocks  Okanagan Valley fault can be traced from Green Lake where it enters the  area from the north, to southeast of Oliver, where it leaves the map area. It is  exposed only locally east of Oliver and at Mahoney Lake, (Fig. 50) where the map pattern shows it to be low angle (10°-20°), and west dipping. The fault is, in these exposures, marked by underlying mylonitic pgn, orthogneiss, or ultramylonite (Fig. 51), which  grades upward  into  microfaulted mylonite, brecciated mylonite  and ultimately  brecciated, chloritized, and silicified upper plate rocks (Fig. 52). This fault everywhere juxtaposes intensely fractured rocks against ductiley deformed rocks. The fault itself was presumably ductile at depth (represented by mylonitic pgn) and brittle at shallow levels (represented by abrupt truncation of the brecciated upper plate). The overprinting of contrasting strain types is seen in brecciated mylonite. In this interpretation the fault embraces a brittle-ductile transition, and now juxtaposes rocks from contrasting strain environments.  ° Is  1 ^ Hi* H  ** c>  1 CP  o IP  to a  0  100  101  Figure 51: Photomicrographs of mylonitic pgn at Mahoney Lake.  102  Sense of shear indicators (Simpson and Schmid, 1983) (Fig. 53) from mylonitic rocks at Mahoney Lake are not everywhere unambiguous (Ross, 1973, and 1981) but are  interpreted  to be consistent  with  westward  movement of the upper plate. This  same sense of shear can be seen in asymmetric fabrics (Bell and Etheridge, 1973; Berthe et al., 1980; White  et al., 1980; Lister and Snoke,  1984) parallel to  stretching lineation in rhomb porphyry 1 km east of Willowbrook (Fig. 54) and  the in  gneiss east of the Okanagan Valley (Bardoux, 1985; Parrish et al., 1985).  Lower  Plate  Rocks structurally beneath the Okanagan Valley fault have been deformed at temperatures of at least 400°-500° C. The structural geometry  of these gneisses has  been well documented (Christie, 1973; and Ross and Christie, 1979), and is summarized in Table 10. The predominant fabric within the gneisses is the foliation (Fig. 55) ( F of Christie) which consistently dips gently  2  westward. The leucogneiss body (lgn) has  been demonstrated to crosscut the earliest fabric (FO but contains the F  2  foliation.  This foliation is generally defined by compositional layering and is commonly mylonitic. This mylonitic foliation becomes more common, and more strongly developed structurally upward and towards the west lineation, outlined  Within the mylonites there is a consistent  by elongated quartz and pulled  trends N65W, 10SW (Fig. 57). F  2  apart feldspars  stretching  (Fig. 56), which  fold axes parallel this stretching lineation (Christie,  1973), and are interpreted to be rotated into parallelism by progressive simple shear (Bell, 1978; Bell and Hammond, 1984). The rhomb porphyry (dated at 51 Ma) can be shown to locally crosscut this mylonitic fabric but is "also foliated and lineated parallel to F . The post-51 M a 2  deformation must have been at temperatures higher than  450° -500° C (Harrison, 1981), because of garnet and biotite growth in pullaparts of feldspar and pyroxene in the rhomb porphyry, and 51 Ma hornblende dates on the  Figure 52:  Photomicrographs  of brecciated mylonite from Mahoney Lake.  1 mm  Figure 53: Photomicrographs of mylonites showing sense of shear of top to the west Looking north.  105  106  Table 10 Summary of t h e S t r u c t u r a l E l e m e n t s In the Vaseaux F o r m a t i o n (Christie,  1973)  i s o c l i n a l r o o t l e s s f o l d s ; f o l d axes and l i n e a t i o n s p l u n g i n g v a r i a b l y N and S.  penetrative  t i g h t o f t e n r o o t l e s s f o l d s ; f o l d axes and l i n e a t i o n s g e n t l y p l u n g i n g NW and SE;  penetrative  open to t i g h t f o l d s ; SSW and NNE g e n t l y i n c l i n e d s u r f a c e s ; f o l d axes and p e n e t r a t i v e l i n e a t i o n s p l u n g i n g g e n t l y WNW and ESE. open f o l d s ; axes g e n t l y  s t e e p l y d i p p i n g NE p l u n g i n g N and S.  fractures; rare  open f o l d s ; s t e e p l y d i p p i n g W to NNW f r a c t u r e s ; minor f o l d axes g e n t l y p l u n g i n g NW and SE.  axial  fold  Figure 56: Photograph of lineations in lgn unit  108  gneisses. Temperatures could not have  exceeded 500° -600°  because of only partially reset 58 Ma  Rb-Sr date on muscovite from the leucogneiss.  This  several  ductile  fabric  is  overprinted by  sets  of  C  minor  (Wagner et al., 1977),  warps (F , 3  F,  F  4  J (  of  Christie, 1973) which interfere to produce a foliation dome evident in the topography. Possible apparent F  2  interpretations for the rhomb porphyry both cutting and containing an  fabric, are: 1) That it was intruded late in a single protracted mylonitic  event, and crosscut some mylonitic zones but was caught up in continuing deformation; 2) that the rhomb porphyry crosscuts an earlier fabric (syn-, or post-intrusion of lgn) which was reactivated after 51 Ma. In fabric  in  the  rhomb  porphyry  is  either case, the deformation responsible for the  also responsible  for  bringing  the  gneisses to the  surface. In summary, the lower plate shows ductile strain. The overwhelming fabric is a gently except  west dipping foliation (F ). This fabric affects all rocks within the lower plate, 2  the  rhomb  deformation was  porphyry  which  apparently  both  contains  and  crosscuts  it  This  either one protracted event or was reactivated after the intrusion of  the rhomb porphyry. The interpretation is  that  the  deformation seen in  the  rhomb  porphyry is responsible for much of the mylonite which becomes increasingly pervasive structurally movement  upwards related  to  (towards the  the  Okanagan  west).  This  Valley  mylonitization  fault  These  represents  mylonitic  rocks  mid-crustal were  then  overprinted by the chlorite breccia as they approached the surface.  Timing  of Brittle  and  Ductile  Deformation  The brittle deformation in the upper plate is known to be as young as Eocene because it affects White Lake 'Basin rocks. There are several angular unconformities in the upper parts of White Lake Basin, with associated conglomerates and megabreccias, deposited in active-fault bounded basins. The lower half of White  Lake Basin shows  109  little evidence of syn-depositional faulting. Extensive tectonism appears to have affected White Lake Basin only after deposition of the Marron  Formation at approximately 50  Ma. The age of structures in the lower plate is not well constrained. In order there is a fabric (foliation, early isoclinal folds) older  than  the  intrusion  of  the  leucogneiss  body.  a relative  within the paragneiss which is  The  second,  predominant  fabric  overprints the lgn  body. Apparently this fabric also affects the rhomb porphyry. The  best absolute  relationship  than  51 Ma.  age The  strong  that the  earliest fabric  Precambrian. The main F A  is  fabric in  (pre-lgn)  is  the rhomb  pre-Jurassic, and  porphyry may  be  is  younger  as  old  as  event is post-Early Jurassic to possibly post-Aptian.  2  argument  that the mylonites in the lower plate are Eocene is that  they are not annealed even though, from geochronometric evidence, the gneisses must have been at relatively high temperatures at this time. The deformation of the rhomb porphyry, and presumably  formation of the mylonites, is coincident in time with the  Eocene extensional deformation in the upper plate.  Discussion  In  and  Regional  Implications  recent years  1978; Frost and  the literature on  Martin,  crustal  1982; Wernicke,  extension  has  1981, 1985; Wernicke  blossomed and  (McKenzie,  Burchfiel, 1982;  Wernicke et al., 1982; Wernicke et al., 1985; Allmendinger et al., 1983; Miller, 1983; Miller et al., 1983). Quantitative evaluation of the amount of extension and diplacement on  known  structures  faults can  be  has  been the focus  matched  across  the  of  much  of this  Okanagan  Valley  work. Because fault,  no  units  reconstruction  to  or a  pre-extension configuration is not possible. However, an estimate for structural omission across the Okanagan Valley fault can be derived using in the previous chapter.  geochronometric data presented  110 Granitic rocks west of the fault give Jurassic and Cretaceous K-Ar and  hornblende  biotite dates. Gneisses immediately in the footwall of the Okanagan Valley fault  give K-Ar 50° C/km  hornblende dates averaging 51 Ma. and  30° C/km  implies between 9 and  Using assumed geothermal gradients of 15 km  structural omission across this  fault Combining this with a simplified fault geometry implies displacements between 10 and  60 kilometers. These estimates are meant to show: a) the extremes in possible  displacement due to fault geometry (listric versus planar; Wernicke and Burchfiel, 1982), and b) that displacement must be on the order of 10's of kilometers.  Figure 57: Stereonet of mylonitic lineations.  Ill Conclusions  Although  there is evidence for early structures (pre-Late Triassic) in both the  upper and lower plates, the latest, and locally pervasive structures are interpreted to be Eocene. This includes both the brittle deformation of the upper plate and some ductile deformation  and  mylonitization  in  the  lower  plate.  The  explanation  for  these  late  structures is a low angle normal fault regime (Fig. 58) as described by many workers in the Basin and Range area of the western U.S. et al., 1980; Coney, 1980; Coney  (Armstrong  1972, 1982; Crittenden  and Harms, 1984; Davis, 1983; Davis and Coney,  1979; Wernicke, 1981; Wernicke, et al., 1985). The resulting interpretation is that the Okanagan Valley  fault is responsible  the Okanagan Metamorphic  for the tectonic unroofing  and rapid cooling  of  and Plutonic Complex. This idea is compatible with both  structural and geochronometric evidence, and implies 10's of kilometers displacement on the Okanagan Valley fault  Geologic Cross Section White Lake - Vaseaux Lake Area  0  1  2 Miles  Scale  Figure 58: Cross-section through White Lake and Vaseaux Lake area (see Figure 2 for location and legend); unit symbols: eTv=Eocene volcanic rocks; eTs=Eocene sedimentary rocks; lPz-Tr=late Paleozoic to Triassic eugeosynclinal formations; lgn=leucogneiss; pgn=paragneiss of Vaseaux Formation; K-Jg=Cretaceous or Jurassic gneissic granitic intrusives. Elevations in feeL Modified from Christie (1973), and Church (1973).  VI. G E O L O G I C HISTORY O F THF. S O U T H E R N O K A N A G A N  The  pre-late Paleozoic history  only  inferred.  The  age  of  of the southern Okanagan region  the  Vaseaux  Formation  REGION  can be, at present,  protoliths  is  unknown.  Highly  radiogenic Sr from these gneisses suggests that they could be Precambrian in age. This Precambrian  component  is  not  evident  in  the  U-Pb  work.  (Except  possibly  the  leucogneiss discordance). Deposition of the eugeosynclinal  formations  (Apex  Mountain,  Kobau, Anarchist;  Milford, 1984; Okulitch, 1973; Read and Okulitch, 1977; Monger, 1977) began in the mid-Carboniferous  and continued through  greenstone, chert, limestone, argillite) basin. By and  represents an ocean floor, interarc, or back arc  late Triassic time these eugeosynclinal  deeply  probably  the early Triassic. This sequence (ultramafic,  eroded  (Read  represents  Nicola-Rossland  and  telescoping  Okulitch, of  formations  1977).  this  This  basin  had been intensely folded  pre-Late  before  Triassic  the  deformation  beginning  of  the  volcanic arc environment (Monger and Price, 1979).  Following this deformation the Late Triassic Nicola Group equivalents at Olalla Creek were deposited (Read and Okulitch, 1977). The Nicola Group represents a Late Triassic to Early Jurassic island arc sequence. The gneiss of Osoyoos is time correlative with  the Guichon Batholith  Group. An Valley  is  and other early Jurassic intrusives associated  with Nicola  important observation in the history of the rocks west of the Okanagan that the Late Triassic rocks  are only  mildly  deformed (tilted and  faulted)  and unmetamorphosed except near Jurassic or younger plutons. Jurassic time in This  began  deformed  with  Anarchist  the  the southern intrusion  Formation,  of  Okanagan the  followed  was  granodioritic by  the  marked  by  abundant  gneiss  of  Osoyoos  Olalla  Syenite  and  granodioritic batholith (mJ) intruding deformed Apex Mountain, and Kobau  113  plutonism. (eJ)  into  Similkameen strata. The  114  Late Jurassic was marked by more felsic intrusions (Miller and Bradfish, 1980) of the Oliver  pluton  (garnet-muscovite  phase)  and  the  granite  of  Anarchist  Mountain  (garnet-biotite). This Jurassic intrusive event has correlatives farther east with Kuskanax (Miller,  1978;  Anarchist  Parrish  Mountain),  and  Wheeler,  and  Galena  1983;  Bay  Olalla,  Stock  Similkameen),  (Oliver  Nelson  Granite),  both  (granite  in  time  of and  sequence of composition (Gabrielse and Reesor, 1974). Within  the Okanagan Metamorphic  and Plutonic Complex  several plutons were  emplaced in either Jurassic or Cretaceous time which have since been highly deformed and  metamorphosed  (leucogneiss,  gneiss of  Lake). The Kettle (Cheney, 1980; Rhodes 1976;  Goodge  Carr,  1985)  and  Hansen,  gneissic  1983)  culminations  and all  Skaha  Lake, and  gneissic  sill  of  Vaseaux  and Cheney, 1981), Okanogan (Fox  Valhalla contain  (Parrish,  deformed  1984;  Parrish  Cretaceous  et al.,  et al., 1985;  and  Cretaceous(?)  intrusives. This observation may be the key to explaining the later evolution of these domes. Cretaceous time in southeastern B.C. is marked by crustal melts indicating large amounts  of crustal thickening (Monger  et al., 1982; Armstrong,  1983). A  scenario of  crustal thickening prior to and spatially related to later crustal extension fits the model of Coney and Harms (1984) for the development of metamorphic core complexes. The  Paleocene  was  a  time  of  relative  quiescence  with  only  a  few  known  intrusives of this age (Medford  et al., 1983; Parrish, 1984), which probably represent  the  episode  beginning  of  the magmatic  that culminated  in  Early  Eocene  time. The  Eocene begins with a regionally developed basal conglomerate (Springbrook River  Formations)  volcanic  sequence  followed by the voluminous then  evolved  with  time  mafic alkaline Marron into  a  more  felsic  and Kettle  Formation. This and  calc-alkaline  composition (Church, 1973). The higher parts of this Eocene basin are highly disrupted by  syn-depositional  deposited in 4-10 in  the  upper  normal  faulting. The entire Eocene section appears to have been  Ma. This basin development and subsequent extensional deformation  plate  of  the  Okanagan  Valley  fault  is  coincident  with  intrusion,  115  deformation  and  metamorphism  of  the  rhomb  porphyry  in  the  lower  plate,  and  development of extensive mylonites responsible for tectonic unroofing of the Okanagan Metamorphic and Plutonic Complex. A similar pattern of deformation, but with opposite sense of movement, has been documented for the Valhalla Dome to the east (Parrish et al., 1985; Carr, 1985). A  highly extended Eocene section has also been documented  at Midway (Monger, 1968), between the Okanagan and the Valhalla area. The  implication is  that a large  area of southern  B.C.  has  undergone  crustal  extension (Parrish, 1985). The geochronometric evidence shows this to have taken place very  rapidly  beginning  at  approximately  51  Ma.  This  might  possibly  be  tied  interaction of the North American plate and the Kula/Farallon plates offshore  to  (Ewing,  1980). Plate motions and velocities for these plates (Engebretson et al., 1984) indicates that for most of Paleocene time the motion between North America and Kula/Farallon plates was at a low velocity with oblique, nearly strike slip, convergence. The Eocene is marked by very rapid plate velocities and more orthogonal convergence (Engebretson et al., 1984). This  apparently set up an intense arc-back  arc volcanic regime  which  may have brought about mantle upwelling. The initial mafic alkaline magmatism can be interpreted as mantle melting, signaling the onset of this aesthenospheric upwelling. As this  thermal  pulse  calc-alkaline,  felsic  moved  upward  composition.  The  into  the  crust  deformation  followed the onset of volcanism and may  the  volcanism  (extension)  also  changed appears  to  to  a  have  be linked to the evolution of the arc or  back arc environment Tectonically little seems to have occured in the Okanagan region since the demise of this intense Eocene activity.  REFERENCES  CTTRD  Allmendinger, R.W., Sharp, J.W., Von Tish, D., Serpa, L., Brown, L., Kaufman, S., Oliver, J., Smith, R.B., 1983, Cenozoic and Mesozoic structure of the eastern Basin and Range province, Utah, from C O C O R P seismic-reflection data: Geology v. 11, p. 532-536. Anderson, J.L., and Rowley, M.C, 1981, Synkinematic intrusion of two mica and associated metaluminous granitoids, Whipple Mountains, California: Canadian Mineralogist v. 19, p 83-101. 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'W 119°35.0'W 119°35.0'W 119°35.4'W 0  (Jpgr):  porphyritic b i o t i t e granite 49°12.2'N, 119°31.2'W porphyritic b i o t i t e granite 49°12.2'N, 119°31.2'W hornblende-biotie granodiorite' 49°11.5'N, 119°35.0'W porphyritic b i o t i t e granite 49°12.4'N, 119°35.4'W porphyritic b i o t i t e granite 49°13.1'N, 119°34.7'W porphyritic b i o t i t e granite 49 13.1'N, 119°34.8'W p o r p h y r i t i c b i o t i t e g r a n i t e ( a l t e r e d ) 49°13.2N, 119°35.0'W 0  Garnet-Muscovite g r a n i t e samples (Jgr) : 234 209.1 209.2 263 182 9  garnet-muscovite g r a n i t e garnet-muscovite granite garnet-muscovite g r a n i t e garnet-muscovite g r a n i t e garnet-muscovite g r a n i t e garnet-muscovite g r a n i t e  49°11.75'N, 49 13.1'N, 49°13.1'N, 49°12.5'N, 49°13.3'N, 49°13.2'N, 0  119°33.8'W 119°34.3'W 119°34.3'W 119°34.4'W 119°37.4'W 119°37.35'W  Whole rock data was derived from XRF analyses of pressed powder pellets using an automated Phillips X-ray spectrometer in the Oceanography Department of U.B.C. Results are oxidized, anhydrous, and normalized to 100 percent totals. Trace element analyses of the same pellets were done using the same equipment Major and tracre element concentrations are based on comparison with U.S.G.S. and other widely analysed igneous rock standards. Mass absorption coefficients are calculated from major element compositions.  127  APPENDIX B -  U-PB  A N A L Y T I C AT, P R O C E D U R E A N D  were  separated  from  magnetic  techniques.  DATA  Mineral Separation Zircon Wilfley  concentrates  table, heavy  liquid,  and  20-40  kg  The  samples procedure  using is  standard  summarized  below.  1.  samples  were broken into fist-sized pieces at the collecting site, and stored in  separate pails for shipment Only the freshest available material with the cleanest surfaces was collected. 2.  the surfaces of the sample were wire-brushed and all loose matter was removed using a high-pressure air nozzle.  3.  samples were reduced to very fine sand size or smaller using a jaw crusher and a disk mill. The crushing equipment was completely dismantled and cleaned, and all crushing surfaces wire-brushed and blown clean between samples.  4.  the heavy  mineral concentrate was  separated  from the sample  using  a  Wilfley  table. The concentrates were washed with acetone and then dried. 5.  metal filings and magnetite were removed using a strong hand magnet  6.  the light minerals were removed using tetrabromoethane (S.G.=2.89).  7.  the  samples  were washed  in  warm  6N  HCI  for  15 minutes  to  remove  iron  oxide coatings on the grains. 8.  samples were passed through methylene iodide (S.G. = 3.32) to remove apatite and other impurities.  9.  the final heavy mineral concentrates were washed HN0  3  and then for 15 minutes in warm 6N HCI  for 15 minutes in warm  8N  to remove sulfides and any  remaining iron oxide coatings. 10.  samples  were cleaned using  a  Franz magnetic  side tilt, 1.7 amps magnet current). 128  separator  (25°  forward  tilt, 2°  129  This procedure usually produced a 99% pure zircon separate.  Preparation  of Fractions  Desired samples  was  and Sample  magnetic  fractions  Dissolution  were  separated  then separated into a coarse  using  (100-200  the  Franz.  mesh) and  Each  of  these  fine (200-325  mesh)  fraction. Several samples yielded very coarse (70-100 mesh) fractions.  purity  Individual  fractions  under  binocular  a  were then weighed microscope.  and hand-picked  These  hand-picked  to greater  fractions  than 90%  were  carefully  weighed, then put into pre-cleaned Teflon dissolution capsules, given a final acid wash (15 minutes in 7N  HN0 ,  15 minutes 6N HCI,  3  15 minutes 2B H 0 2  on a hot plate  at 120° C). After pipetting off the rinse water, 0.75 to 1.0 ml of concentrated 2B was  added  to  the  samples  along  with  3-4  drops  of  concentrated 2B  HN0 . 3  HF The  capsules were then sealed in steel jackets, and placed in a 200°-210° C oven for one week. In all cases dissolution was complete in 7 days. After  one  week,  the  opened. The contents (HF 120°  hotplate. The  overnight, sample isotopic  after  was  were  equilibrate chemistry.  0.5  were ml  aliquoted, one half  composition  (IC),  removed  from  the  oven,  then placed back  of  3.1  of  the  N  the other half  HCI.  3.1N to  in  They  HCI be  the  ovens  spike  weighed and  and  capsules  and  sample.  the Then  ID  solution  mixed  both  placed IC  at  200° -210° C  were then removed  on  and  with  a  the ID  and the  to be analysed 20!  Pb/  and Pb concentrations using isotope dilution (ID).  carefully the  were  plus fluorides) were evaporated to dryness overnight on a  capsules  adding  determination of U splits  samples  235  spike  The IC  hotplate  were  U  ready  for the for  and  ID  overnight  to  for  column  130  Ion Exchange  All  Column  Chemistry  chemical processing  of samples  was  carried out in a laminar  flow hood.  Separation of the U and Pb from the dissolved samples was carried out using 0.5 and 0. 15 ml  Teflon columns. These were stored in  8N  HN0  3  between use. They were  removed from storage, rinsed in 2B H 0 , then loaded with pre-cleaned anion exchange 2  resin, (Dowex AG1-X8, 100-200 mesh chloride form, in 2B H 0). The resin was then 2  washed as follows. 1.  2 column volumes (c.v.) IX  2.  2 c.v. 6N  HCI  3.  2 c.v. 2B  H 0  4.  2 c.v. 6N  HCI  5.  2 c.v. 2B  H 0  H 0 2  2  2  The resin was then equilibrated with 3-4 c.v. of 3.1N HCI. The samples (dissolved hr 3.1N HCI)  were then carefully pipetted onto the columns and allowed to drip through.  The sample was then washed and Pb and U collected as follows. 1.  add 1 drop 3.1N HCI  and allow to drip through  2.  repeat step (1) five times  3.  add 100 lambda 3.1N  HCI  4.  add 150 lambda 3.1N  HCI  5.  take off Pb with 6 c.v. of 6N  6.  take off U  with 6 c.v. of 2B  After the Pb and U  HCI H 0 2  have been taken off the columns, the resin is removed and the  columns  are rinsed in  Cleaning  of Dissolution  IX  H 0 2  and  Capsules and  stored  Beakers  in  8N  HN0 . 3  The  resin is discarded.  131  Teflon dissolution capsules and beakers were cleaned after use as follows: 1.  wash in warm soapy water; rinse in IX  2.  2 days in warm aqua regia; "  3.  2 days in warm 8N H N 0 ;  4.  2 days in warm 6N HCI;  5.  2 days in cold IN  HBr; "  6.  2 days in warm IX  H 0;  7.  remove, drain, and store in IX  Reagants and  IX  "  "  H 0 2  bottle  H 0  in a clean plastic container.  2  Blanks  was obtained from a pyrex-vycor still in K. Fletcher's lab, or from a  quartz still in K. Scott's lab. Using teflon  2  "  3  2  H 0.  still  described  by  IX  H 0, 2  Martinson  starting with reagent grade stock. IX  HCI  2B H 0 2  (1970).  was prepared by a sub-boiling  All  and H N 0  3  other  reagents  were purified  were obtained by distillation in  pyrex; 2B HCI, H N 0 , and H F were then prepared by sub-boiling still. 3  Total procedural blanks, run with every batch of zircons processed, range from 0.1 ng to 1.0 ng Pb, and generally were 0.5 ng or less.  Mass  Spectrometry  U  and Pb isotopic ratios were measured on a V.G. Isomass 54 R  which has  data aquisition digitized and automated using a H P . 85 computer. Pb was loaded using the phosphoric acid-silica gel method on a single rhenium filament, U  was run as an  oxide  single  using  filament U  tantalum  oxide-nitric acid-phosphoric  acid  method  on  a  rhenium  was also loaded using the phosphoric acid-silica gel method and found to  132  be more stable and gave longer runs. Precision on all measured ratios were normally better than 0.1%, and commonly for  instrumental  mass  better than 0.05%. Pb  fractionation  on  the  basis  of  and U replicate  ratios were corrected analyses  of  National  Bureau of Standards SRM-981, and 983 for Pb and U-500 for U.  Data  reduction  U-Pb  and  error  calculation  date errors (2a)  are obtained by individually propagating  all calibration  and analytical uncertainties through the entire date calculation program and summing all the individual  contributions to the total variance. Data  reduction and  automation  are  done on a dedicated Hewlett-Packard HP-85 computer.  U  decay constants and isotope ratios are:  238  U X = 0.155125 x 10-9 a-  23i  U A =0.98485 x 10-9 a"  2 3 8  U/  2 3 5  U  =  1  1  137.88  All published dates cited in the text have been recalculated, if necessary, to conform to these constants.  133  (NTS • Mineral analysis • O • Concordia i n t e r p r e t a t i o n • M i n e r a l or rock i s o c h r o n Sample Number(s) and R e f e r e n c e ( s ) Upper I n t e r c e p t  U  _  D  h  £>P/S&  Lab No:  /US  Ckrisrit;  Ref:  2a e r r o r  Computed Q Assumed •  +  Lower I n t e r c e p t Computed• Assumed • Record No: S u i t e No: Sample Name:  rif/s&Z  2o e r r o r  238 2 0 6 UPb date IT  SJ/I  Ma  f&D.  235  g-f VasetkuX Lake  D V  +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  J  207 U - P b  date  decay constant 2 0 7  • old:  0.1537/0.9722/0.0499/137.8  Qtfew:  0.155125/0.98A85/0.049475/137.88 2 3 2  • other:  Pb/  Th-  2 0 6  2 0 8  Pb  Pb  date  date  • not r e p o r t e d Number of P o i n t s : n=  Latitude:  Longitude:  °  'OO"  N,  UMT Zone Sec.  //? ° 3 /  E  N;  V  (X <30"  W  Z"  or X  Y.Y ) 1  ) ; E l e v a t i o n : /«3 SB  (± C  Province:  C'.  ,T  Co., S t a t e  (NTS  Per* f/c So/l  Map Area (1:250,000)  Location: frm MIB of )/as<?a.L>x: LOLUP ^ Source Type: Rock Types: f e o c a a ^ j ,~c a Uc - ^ r j- - [<-s^c^- n\Wni+rc G e o l o g i c U n i t : f>teiss/C sit/of ^asea^r L«ke. . G e o l o g i c S e t t i n g : /negates. Vassal* A. ^/SAeJi M a t e r i a l Analysed: Zircon  g  g-f c/j-fb y^-eUsi^.  rA  Comment on  Analyses:  Interpretation:  C o l l e c t e d by: Dated b y : _  JL  far forts on  Date of l i s t i n g :  cleave °j*ivel rd. sUI '  Sample  Name  or  Number:  Split-  <p  /V7V  266 218  206  -  Pb  215  U  ratio  Split-  fine  MntAfAo  -33STn,  2tjb ,  <  J  l  ' "  0. o / V ? 7 Spli tMlneral  20b  207  Pb  215  U  ppm P b  /<2  /7  Pb  2 l F T T  r  73.  u  ,  a  t  o  207 215  t  ppm U  Mineral  Pb U  .  pb -  °  r  O.o/Sjo  r  a  t  Spli t-  267  Pb  t  215  U  ppm U  Mineral  206  Pb  f  ,  of  a  Pb  206  Pb  207  . ' ° t  ! °  t  Pb  215  U  r  composition  of  blank:  Isotopic  composition  of  common  . d  a  a  t  o  i  +  t  2  -  e  . r  a  t  Pb  „, r  P  da te  b  U  d  206  Pb j  3  Meas.  238  U  ,  ' °  t  7W5' 206  Pb j  i  238  U  ^  6  -0°°o6C  Ao  t  Mole  ™L 20T  Blank 3.  .  2  -  215  20*1  A  d  a  t  0  7  P  da te  b  U  d  a  206 — r 20T  P C }  / O S  .  207  Pb j  2i5  li  ,  a  s  -  Pb r  a  ,.  ^  206  °  i  n m r  t  i  aofssff  207  .  J d  a  m  Modern  Pb  . r  Pb  232Th/20'tPb=37.19; decay  a  t  i  o  (6A:l8.7, growth  constants  i  20*i  206  Pb  . .  A  Pb j  215  U  Pb U  0.155125,  6/l»»i  1Vl'5?T  0.981(85,  £re:  or  7/^=12.998,  137-88;  207  Pb  206  Pb  Pb  or  Common Pb A q e  j d  ate  Pb  K  +  Common  Rad+ComPt  207  2o5-pb  e  Pb A q e  Pb  Mole  3  t  e  0 O t h e r  a  Rad+ComPt  207  %  Pb A q e  /VC Pb  IbTTb %  i  e  Common  o.m  Pb  t  Pb  Rad.  . . d  a  t  Pb  207  i  206-pb  A  e  t  Pb A q e  Pb j d  °&  Common  Rad+ComPb  .  . a  t  C  TA  i  +  faAiaS. (6/'i:/77/7/'i/j:i'78/'i:J700 )  0?T=31.23 a t Other  .  d  - i : /  Rad.  AJ Blank  Pb j  /si.? %  *-  isefop/'t  [JJ  R  +  " 3?.o  Rad.  +  / _g~  7/^: l | f l W i ? ® h : 3 8 . 6 3 )  t  j d  Pb  0 7 /  ,  t 3  ™L 20T  215 +  curve:  d  *  207  ate  o. rrV  0.3%  207  Meas.  t  lov- J o ^ . i , , '  _£__P—  on S-K  . e  j d  ±£f  -  Blank  ff.o  208  loTTb  3x/£  t  ±0.ooo/3  207  .  Pb  Pb  ,  Mole e  Pb  206  Rad.  %  AO  20^  207  / . O O  (7^VS? 207  Pb A q e  Rad+ComPt  +  Blank  -  M  loTTb  * Pb S%  Mole  -/a  208  Common  (37.3  - Ae  „„ Meas. c  e  Pb  Rad+ComPt  +  a  O o 8 £ ~  +  Pb b a s e d  7  ?7.  20l|  /  207  ' ° ±  e r r o r s  [Is-K  a  oo-Yg77  *  .  0  235  - AO  9S-.7  208  +  Isotopic  U  6-  -  206  207  238  Pb  Rad.  oooa.  208  206 Pb  taoooc,  ppm P b  ^  Pb  O O  o./o£<(  Uncertainties:  238U/20'iPb=9.7'i,  to-oeaog-  206  9YY  . r  + Statement  207  206  .  +  207  ±0. oooST  ppm P b  -aooocf  +  .  /  2~T8 ir  o  u  207  206  Very Course 3.9^9 m  a  206  %  /.ooa  - O.oo/e  £>. /ooS Split-  r  y  . i  Pb  „.  Mole Blank  y'f/sy  ratio  Oo97y  -6.000/0  206  206  ppm U  jr. 5~m<>  -&oonf  -  Pb  O. o Y * 7 P  /OO U  2l8  to.ooay  ppm P b  ppm U  +  207  Meas.  2Ct  o.  207  o./ooG>  Mineral  208  207  20,5"  U  •  Sheet  ppm Pb  ppm U  Mineral  Fin e  ptt?'^  3-7Ga  (G/'t:  4^  with J/U:  8/l»  :  )  135  U  cfj.  (NTS  D Mineral analysis •Concordia interpretation D M i n e r a l or rock isochron Upper I n t e r c e p t Sample Number(s) and R e f e r e n c e ( s ) Computed• Lab No: 7>P /77 Assumed D Ref: L,rf/f Mm /6~Lower I n t e r c e p t Computed• Assumed • Record No: 238,, 206 , , ^ UPb date S u i t e No: Sample Name:  e/s  —DK ~» O  2a e r r o r +  Ma 2a e r r o r  +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  o  /  skaka. Ukt.  2 3 5  U-  2 0 7  Pb  date  decay constant 2 0 7  •  oldj  0. 1537/0.9722/0.0499/137.8  0 ^ :  2 0 6  Pb  date  0. 155125/0.98485/0.049475/137.88 2 3 2  •  Pb/  other:  Th-  2 0 8  Pb  date  Q n o t reported Number of P o i n t s :: n=•  Latitude: (V?  Longitude: N,  °JY'2S'"  //?  °3Y  UMT Zone Sec.  (X° ' OS~"  N;  Y' W  (±  Province:  <  or  X°  );  Elevation:  Y.Y') '  Co., State_ _Map Area (1:250,000)  (NTS  Location: S~-/ km SovrA Source Type: roa.ct'<Lvr~ Rock Types: 9*e>/'5<,/V Mb Geologic Unit: a*e;sj> G e o l o g i c S e t t i n g : / /yi£uff(es M a t e r i a l Analysed: g / V c o n  ok Pe^rv'c/c^ —on £>sa>roe//or/£r Zaitp  s6*Aa. Vasea.uK  ^^cst*- s/orct  fats  Analyses:  J).  C o l l e c t e d by: 3  7%,/HS>0*>? -  7*'  S/^g/a.  q-.H/e, JlGf)  Interpretation:  Dated by:  ///O  —-  ,R.  ,T  Comment on  Z"  a  Date of l i s t i n g :  -4g/f>  °f SAaric ^-A^C  Sample Name o r Number: ^t^e/sS Spli tHlneral Fj*e Mat  3oS  2t)6 Pb  mrr O.0'S*/y Split-' Mineral  „. _,_  rat  '° t o.eooof  ppm U  C^aars e Mr* Mey 33 Or»f  20b Pb  .  2wrr  rat,  C>/63o Spl1tMi n e r a l  °t  to.ooooj  206  SplitMineral  —  +  2T8~rr  +  2W  t  ppm U  206 Pb +  4. ?3?3 207 Pb  „. ^ '° ±  206-pb  rat  t I  206 Pb j  ^  '° *  TWIT  206  207  G./a.  /OO  /.?S7Y 207 Pb 206-Tb  r  a  t  O./0 93  Statement o f U n c e r t a i n t i e s :  20 7 , 2  s  Pb u  207  Pb 238 u  Pb  207 Pb  loTTb  + arc  d  e  r a t  ,. '° +  -  e  20lf  206 Pb . „  ^  t  M T  ¥  .  +  i £^  d  d a t e  +  0  7  P  b  a  t  a  a  +  206 Pb , . d a t e  A&4,>  +  ^  t  /oS  207 Pb j 206~Pb d  a  t  e  , t  207 Pb , . . 215 U t + a  t  e  207 Pb 235 U  %  d  +  Common Pb Aqe  207 Pb . . d a t e  +  A  t  Mole % Rad. Pb Common Blank Pb Rad+ComPb Pb Aqe .  J d  207 Pb , ate 206 Pb +  loTTb  R  Common Pb Aqe  Mole % Rad. Pb Blank Pb Rad+ComPt  Meas. 206 20T  TTiTTT  O. ? 96 .  Mole % Rad. Pb Blank Pb Rad+ComPt  da te +  d  R  %  t /• SL  20T  i  •  e  Meas. 22*  ^  .  *  2.  o. 9%  Y  235 U  o. ??£  Mole * Rad. Pb Common Blank Pb Rad+ComPl Pb Aqe  IoT  208  r a t i o  a. a-  t  - /  Common Pb Aqe  20S~Pb  e  207 Pb . . 235 U t  2 a  t  Meas. 206  +  208  207  . rat.o.  t  a  IoT  VJ33  /o£~.  20&  b  I06-Pb  206  ppm Pb  t  P  207  . . . '°± +  a  . t  20(t  r a t l  r a t  d  208  J rati o + 206 Pb +  2 0  206  207 Pb 215 U  2WTT  r a t ,  207  +  Meas. 206  d  ]  207 Pb j  A  20A 206 Pb , .  . ^ ° t  t  O. (=%  207 Pb . . 235 U t • ??. 7  c o o fey  ±00007  ratio +  20T  ± -/o  /o</. 3  206  20TPb 235 U  208  A  . . . '°±  .  |  Mole % Rad. Pb B l a n k Pb Rad+ComPt  Meas.  d a t e  fr.7  ppm Pb  207 Pb 2v;u  20*1  /O.033.S to. oo(></  O./03/ -o.oooC  .  r a t i o  r a t  208  207  /oo  ppm Pb  „. ra  SplitMineral  -  ppm U  206 Pb  y-7 207 Pb 235 U  ppm Pb  ppm U  218 U  206  ppm Pb  ppm U  Sheet  a  t  e  , ±  207 Pb j  206-Tb  +  d a t C  .  t  +  jra.  I s o t o p i c c o m p o s i t i o n o f b l a n k : f ~ ] s - K Modern Pb ( 6 / l » : l 8 . 7 , 7/^:1$J63', l/A: 38.63) o r p T o t h e r (6/A J7- 7fl/k :Ai'S78/U : 37°* ) I s o t o p i c c o m p o s i t i o n o f common Pb based on S-K growth c u r v e : 6/A-11'. 152,'' 7/A=12.998, 57V=31.23 at 3.7Ga w i t h 238U/20APb=9.7't, 232Th/20'tPb=37.19; decay c o n s t a n t s 0.155125, 0.98A85, 137-88; o r Other (6/^: J/k: %/k : )  137  (NTS D Mineral analysis Q Concordia i n t e r p r e t a t i o n D M i n e r a l o r rock i s o c h r o n Sample Number(s) and R e f e r e n c e ( s ) Upper I n t e r c e p t Computed D Lab No: g F J ^ O Assumed D  U  — Dh • O  2a  __  +  Lower I n t e r c e p t Computed • Assumed • Record No: S u i t e No: Sample Name:  error .  2a  238 206.,, . UPb date  Ma  error  +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  IT  235.. 207_, . ^ UPb date decay constant  207 . ,206-. , Pb/ Pb date D  •  old:  0.1537/0.9722/0.0A99/137.8  •  other:  •  not  232_ 208,,, , ThPb date  reported Number of P o i n t s : n=  Latitude: (V? UMT  Longitude: "  °  N,  //?  3 3 ' & _N;  Zone  Sec.  0  (X "  Y' W  (±  Province:  Z"  or  X  );  Elevation:_  Co., Map Area  Location Source Typ>e: f -r^crep Rock Typ Geologi c Unit: Xh***L '?»zA«ry Geologic Setting: T^i^urJe<i M a t e r i a l Analysed: Z/rrmsf  '  u  Comment on  Y.Y')  B.C.  , T  (NTS  <Jikc"  State  (1:250,000)  f  "  '  Analyses:  Interpretation:  C o l l e c t e d by: , / ) , Dated by:  task/nSm^  /a r f(  =5  Date of l i s t i n g :  Sample Name o r Number SplitMineral •f.n €  U  ppm  ppm  //OO / C »<g ' 2 0 6 Pb .. .  2iru11-  Mine r a l Coarse  ° t  r a t ,  U  ppm  Sheet  5".  207 2  ppm  2 0 6  2 0 6  U  ppm  Pb  .. a  t  ,  Pb  U  „,  ppm  ^  + Statement o f U n c e r t a i n t i e s :  i  o  . . . '° ± +  r  a  t  i  °  I W T  i  d  a  t  Pb 206-Tb  A  i  e  . . . '°± +  r a t  Pb 235 U 2 0 7  t  207 Pb r  a  t  i  °  t  Pb 206-Tb  r  a  t  CW^  r  , a  t  i  o  +  cD CT  i -  t  e  +  D  A  T  E  2 3 T T T  <^^~^T^J  D  A  <o/7 C-6% 207 Pb , . 235 U *A  d  T  E  a  ^o.&  t  e  ± f-8  a  t  e  235 U  d  ,. ^ t +  a  a?t/) 2 0 7  R  206  -  SO  Pb j Pb d  a  t  e  . -  3^.7  Rad. Pb Common Mole S Blank Pb Rad+ComPt Pb Aqe  t  C  207 ±  20A 206 Pb . .  d  Pb j 206" Pb + 2 0 7  d  a  t  e  . -  R  % R  Rad. Pb Common Meas. 2 ? T ^Mole % 20¥ Blank Pb Rad+ComPt Pb Aqe  +  208  207 Pb  t  C  Pb _, . . 206" Pb -  Mole 1 Rad. Pb Common Blank Pb Rad+ComPt Pb Aqe  20T  20TT  20*)  2 3 T T T  c  207 Pb  a  t  Meas. 206  206 Pb . „  ,. ^ ' ° t +  207  206-Tb  d  208  207  . . . '°± +  20^  2 3 T T T  +  207  £  206 Pb j  ., .  206-Tb  e  -  208  207  r a t  efroKS  a  viftf. ?  206  Pb  d  a  S&  207  £~3. V * O. ? H  . i  2 0 6  r a t ,  d  „ 206 neas. — r -  20l|  Pb j 238 U  ., ^ ° t  207 Pb , . 235 U t  t  -0.6  208  207  206  Pb  2 0 7 Pb 235 U  .  ° t +  ppm  206 Pb . .  ^  sy.s  206  r a t  ppm  t  Pb  Pb 235 U  +  bp 111Mlneral  a  2 0 7  ° t  r a t ,  2WTr  2 0 6  ppm  Pb  2TOSplitMineral  U  ppm  0.96/  /r.o32&  Pb  207  ., . ± toooof  2 0 7  Mole * Rad. Pb Common Blank Pb Rad+ComPt Pb Aqe  Meas. 206  /oo  /  ^  r  SplitMi nera 1  'f  206-Tb  206  Pb  20*1  2 0 T  O.oS-Vf to-oooy  Pb 2WTTratl° ± 235 U 0. eo 793 ±000005 0.oS~// ' 2 0 6  207  Pb „. ^ „ rat.o ±  «  208  207  9-5"  /9a 3  Pb  206  Pb  •  Pb . . 235 U + A  d  a  t  Meas. 206 2 0 T  A  ±  +  /0~~  207 Pb 235 U  (hr  d  a  e  Pb j 2 0 6 " Pb + 2 0 7  d  a  t  G  , -  Mole % Rad. Pb Common Blank Pb Rad+ComPb Pb Aqe  t  +  . . t e  /So/op.v'C  207 Pb j 266" pb + d  a  t  . e  i  rex //Q3  !8A:38.63) o r f^fo'ther {(>/UJTTiV/U-JL<:y78/k:37O0 ) I s o t o p i c c o m p o s i t i o n o f b l a n k : [Is-K Modern Pb (6/^:18.7, 7 / ' t : l j j I s o t o p i c c o m p o s i t i o n o f common Pb based on S-K growth c u r v e : 6 A ' 1'. 152,' 7/4=12.998, 87T= 31-23 a t 3-7Ga w i t h Ilk: 238U/20'iPb=9.7't, 232Th/20'»Pb=37.19; decay c o n s t a n t s 0.155125, 0.98485, 137-88) o r [ [ Other 8/A :  139  (NTS ©"Mineral analysis Q Concordia interpretation • Mineral or rock isochron Upper Intercept Sample Number(s) and Reference(s) Computed • Lab No: Assumed • Ref: £/-v't>t fWr /f63 ~~ Lower Intercept Computed• Assumed • Record No: 238 206^ . Suite No: UPb date Sample Name:  U  f  —Dh ""*v U  %c2 £  2o error +  Ma  L  2a error +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  TT  235.. 207,,, , „ UPb date decay constant  207 . ,206 , , „ Pb/ Pb date D  • old:  0.1537/0.9722/0.0499/137.8  Qliew:  0.155125/0.98485/0.049475/137.88  D  232^ 208 . ThPb date nv  • other: • not reported  •  Number of Points: n= Latitude:  Longitude: O"  N,  //? V?.6<  (X  Y'  0  UMT Zone  W  N;  (±  Z"  or X  ); Elevation:  Province:  _,R.  Sec.  Y.Y')  Co., State _Map Area (1:250,000)  (NTS  Location: -/<?c*rW erf O/g/fa tCov\ rogJcok j^s~r SovM Source Type: oof crop Rock Types: AfaA'f SyreuiH AnupltX Geologic Unit: g 'O/a//* SyfxJ/-tt Geologic Setting: i A tr ucf e± 'Apr* Mou«A;« r^aop Material Analysed: ircevt  d  Arto-isl  ^  Comment on Analyses:  Interpretation:  Collected by: Dated by:  2).  R- I.  Ar*1S-/rtv19  TarfailSam  Date of l i s t i n g :  /  Sample  Name o r  Spli tMlnera1 Gin*  Number:  206  ppm Pb  ppm U  /oo  /3V/ ' 206 Pb r 2  i  r  r  a  t  r  .. . ° i  ,  207 Pb 215 U  „. '° *  207 Pb 206-pb  ppm U  206 P b _ . , „ 218 u — + A  SplitMineral  ppm U  SplitMineral  A  ppm U  206 Pb ,. ^ 2T8-u° ± + r a t ,  bp 111Mineral  ppm U  206 Pb M i r r  Statement o f  a  t  l  207 Pb r a t i o + 215 U + ppm Pb  206 Pb —ra . 11 o + 2l8 + h  206  ppm Pb  206  207 Pb 215 U  r a t  '° * +  ppm Pb  206  207 Pb 215 U  r a t  . . . '° ± +  ppm Pb  . ° t +  Uncertainties:  206  207 Pb 215 U  r a t  . '°± +  0  7  P b  206 Pb  A  0+  rati  r a t i  -rrors arer j _ g ~  t  0.??7 DOG  201.  d  a  t  iinr  +  2imr  . date  +  208  .» i  +  o  . t  -  206 Pb 1^  r/*/eJ-(  :  date  +  7  P  d  a  +  d  a  t  e  d  a  t  ,  6  207 Pb j 215 U  ±  d  Jtr*-  /So  e  . i  R  207 Pb . ate + 206 Pb +  R  d  207 Pb j 206 Pb + d  a  t  . -  e  R  e  2bTTb  d  a  t  e  +  t  Mole % Rad. Pb Common Blank Pb Rad+ComPb Pb Aqe  Meas. ° _ 20T  ^ / <r~  , t  207 Pb , . . 215 U + 2  t  Mole % Rad. Pb Common Blank Pb Rad+ComPt Pb Aqe  Meas. 12^L 20T  i  a  Mole % Rad. Pb Common Blank Pb Rad+ComPt Pb Aqe  +  .  d  Mole % Rad. Pb Common B l a n k Pb Rad+ComPt Pb Aqe  207 Pb j 215 U  -  207 Pb j loTTb  + /.  da t e +  b  215U  201)  iTB-rr  0  e  Meas. 106  20<i  206 Pb ° t +  t  2 +  ,  d a t e  t  Meas. 206 20T  20l)  206 Pb j  ^ ' ° *+  r a t l  a  e  a  2.  P b  208  r  d  ± 2 - 0  208  r a t  207 Pb . „ ^ 215 U ±  e  *°S date 218 u +  +  207  207 Pb 20TTb  a  208  207  loTTb  d  ±QOO<x>7/SS. C  207  207 Pb 206-pb  Meas. 206 20T  *°6 Pb , . ^ 218 u -  .. ° ±  r a t ,  207  2  20l|  Mole % Rad. Pb Common B l a n k Pb Rad+ComPt Pb Aqe  • */C.17U O. OOQo  S/73? A  r a t  208  207  0OSO8& Spl i t Mlneral  •  Sheet  a  . t  +  / n p i c  e  t  207 Pb j loTTb + d  a  t  e  . t  R  /-O.//0-S  0 0 t h e r {S/h:/7 rf/k:/S.S79>lk I s o t o p i c c o m p o s i t i o n o f b l a n k : £ ^ ] s - K Modern Pb ( 6 / * 4 : 1 8 . 7 , 7 A : 1 5 *3^M'»: 38.63) o r om m ppoosbii ti iioonn o u rr vvee :: 6/'t ^= 2.. 9 9O8,, 87V=31.23 a w ii tt nh iIssoo tt oo pp ii cc cc o o rf common common Pb based D a s e d on o n S-K s - i s growth growtn c cu D / M - 1.152, 7 / //M =1 I Z 3 3 O / H = J I . Z ^ a tt 3-7Ga j./ua w 8/1) 238U/20'iPb=9.7't, 232Th/20i4Pb=37.19; d e c a y c o n s t a n t s 0 . 1 5 5 1 2 5 , O.SSkSS, 1 3 7 - 8 8 ; or Q O t h e r (6/l»: 7/k:  : 37-06  )  141  (NTS • Mineral analysis •Concordia interpretation • M i n e r a l o r rock i s o c h r o n Sample Number(s) and R e f e r e n c e ( s ) Upper I n t e r c e p t Lab No: Z>P ' Computed • Assumed • Ref: ?-ax g / g / (977 Lower I n t e r c e p t Computed• Assumed • Record No: 238 206 , , UPb date S u i t e No: Sample Name:  U  Q L ™ r D  IT  2 3 5  U-  2a e r r o r +  Ma 2a e r r o r  +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  o  2 0 7  Pb  date  decay constant 2 0 7  •  old:  0.1537/0.9722/0.0499/137.8  •-new:  Pb/  2 0 6  Pb  date  0.155125/0.98485/0.049475/137.88 2 3 2  • other:  Th-  2 0 8  Pb  date  • not r e p o r t e d Number of P o i n t s : n=  Latitude: (f?  Longitude:  °  1  OO  "  N,  //?  ° V/  ' VJ" »  (±  or  X  Y.Y')  );  Elevation:,  Co., State_  _) "Pe/i kic -kcrv1  L o c a t i o n : ^ km norski Source Type: /W//gr5  ok OS k!od>jed  Rock Types: 6rrr.^orJ.or.ff Geologic Unit: S/m,'/Ko-'v?e™ Geologic Setting: /nkkuefrs M a t e r i a l Analysed: ~P-;<con  Comment on  w  Z"  ,R.  , T.  (NTS  Y'  Province:  N;  UMT Zone Sec.  (X  _Map Area  - Czr,g</^ -h-cn^  ho^cker road Cv+-  gV  (1:250,000)  A V y 3,"  31  '  6^rha///li  /ToAau for**a.-/>tn<]  Analyses:  Interpretation:  C o l l e c t e d by: 7)Dated by:_  7kr!< Date of l i s t i n g :  j e ok  Kerc^^ _  Sample  Name o r  Number:  bp 1i t -  £>o//to/'Y~/\  ppm P b  ppm U  Mlnera1 fine. Mc^a ZC  'S//^///(ameir^  206  G2>2. 9 /7.3 P b _  218  u—  f  „  !  A  -  207  bp 1i t -  „  M  C rs  A/0* Moy  oo-Jo"*,  206  ,.  2wir  ratio  0-0^.07/ Split-  206  Pb  Pb  i  235  U  A  2nnr +° ± Split-  206  Pb  2T8-rr  b p 111-  A  rat,  +  °t  ppm U  Mineral  206 F  Pb _ _  a  t  l  o  Pb U  °  i  Pb  235  U  . r  a  t  a  U  ±0.000/'/  .  . r  a  t  207  *  IbT-pb  .  207  a  /<**.£  -  S  a  206  °  i  2 l O -  ,  .  .  207  ±  206-pb  Pb j d  a  t  206  Mole  20T  Blank  rat  '° ±  Pb j  23inr  Isotopic  c o m p o s i t i o n o f common Pb b a s e d  %  Rad.  ' °  t  ±  Pb  a  -  S  . r a t ,  20?  Blank  207  Pb  t  235  U  . d  d  3  .  .  °±  t  t  t  /7&  206  Pb  ,  Pb j U  e  -  d  a  t  e  Pb  0.  ^  207  Pb  *-  235  U  207  t  206-pF  769  Pb  . . d  a  Pb  235  U  Rad.  Pb  t  2oiTPb  e  %  R  Pb A q e  . . d  a  t  Rad.  Pb  e  ^ i  R  Common  Rad+ComPt  Pb  207  Pb  loTTb  ±  Pb A q e  . „ d a t e  A  *  + Mole % Blank  a  t  Common  Pb  207  i  Mole  , . d  _,_  +  206 20T  207  h  date  e  P b Rad+ComPt  ,  Blank  a  t  0  . d  R  Pb A q e  + Meas.  +  Common  9S7  ^  J  m  Heas  ate  d  Rad+ComPt  Mole X  235  ^  .  Pb  Rad.  Pb  Blank  207  2Tinr+ ±  Pb  e  t  -  201)  206  t  a  „ 206 M e a s . —TrH  Pb A q e  °$ %  ' / ty  / COO  .  Common  O. ?7 7 207  )  -/ r  +  +  t  e  Rad.  Pb  Pb  Common  Rad+ComPb  .  207  Pb  206-pF  t  +  Pb A q e  . „ d  a  t  e  ^ i  TA  +  2 a-  Pb  on S-K  decay  C  Pb  +  , .  2 3 0 -  208  Pb  206-pb  Modern  M  |  P b Rad+ComPt  +  a  Mole  201)  206  , a  d  ?. 7  . d a t e  208  r  da te  b  235 U  204  206  t  P  +  Pb  207  are.  composition of blank: Q s - K  C  7  9. ?  208  207  °r  Isotopic  + -  0  * /.V  +  g/yor-s  e  C- 07 OO  ^  t  t  2  201)  „,  207  .  232Th/204Pb=37- 19;  date  d  +  Pb +  r  Pb  loTTb  -  ' ° +  r a t ,  Pb  —  238U/204Pb=9-74,  t a  0. o v ? y y t a 0001%  206  235 u  ° ^ 238 U 0  208  207  ' ° +  ppm P b  Uncertainties:  .  206  207  207  r  2  13. YC 7b  206  207  t  Pb  207  ±0.00//  235  + of  t  o./fJ-l  ^ r  a  ppm P b  ppm U  Mineral  r  ppm P b  rat,  0 +  rati  b  /oo  207  ppm ll  Mineral  P  O.CV7 7?  206  ^  ±0000,5  1 206 20  ±000//  /3. 6 Pb  e  c 2%  rat io +  235 U  ppm P b  ppm U  Mlnera1  Statement  201,  /oo Pb  o./8/f  i  208  207  M  m<\ 206  2  Sheet  (6/4: 1 8 . 7 , growth  m  7/4 : l£ 43  m :38.63)  or  c u r v e : 6/4-11'.'l527/4=12.998,  c o n s t a n t s 0.155125, 0 . 9 8 4 8 5 ,  137-88;  or  f^fother  (6/4 :P Sj/lt  875=31-23  a t 3-7Ga  with  f j Other  (6/4:  7/4:  7  :  ,s.S7 8/4 :78/4:  °0) )  143  U  zaz/s  (NTS _DK r D  Q-Mineral analysis •Concordia interpretation • M i n e r a l or rock i s o c h r o n Upper I n t e r c e p t Sample Number(s) and Reference(s) Computed • Lab No: 2>P9e>  Ref:  CAr-xA-c. /g-Zi/?o*s v- £77,*/?* /?7*  Lower I n t e r c e p t Computed• Assumed •  Record No: S u i t e No: Sample Name:  A foe  +  O  Assumed  ergs  2a e r r o r Ma 2a e r r o r +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  238 206„. , UPb date TI  235.. 207_, , ^ UPb date  o Q/te/sS decay constant  2 0 7  • old:  0. 1537/0.9722/0.0499/137.8  Qfiew:  Pb/  2 0 6  Pb  date  0.155125/0.98485/0.049475/137.88 2 3 2  • other:  Th-  2 0 8  Pb  date  • not r e p o r t e d Number of P o i n t s : n=  Latitude: {¥? UMT Sec.  Longitude:  ° / c f ' 30  "  //?  N,  ° 36  E  Zone , T.  (X  < /O  N;  •'  W  Z"  or  (±  );  Province:  73.  _,R.  /e*>f/c -rz>  (NTS  X  Y.Y')  Elevation:  C  ^  Co., State_  Vtu  ;<?_(//'73) \ /e*ceptriss /Tn  Aar.  M^Ainsovf C/ffS.  /«  Analyses:  Interpretation:  C o l l e c t e d hy\ZE>.7nr'k 'n<&*i — ,. "7^ T$ 7l  Dated by:  . /& r/\<rt^er>]  SO  Map Area (1:250,000)  L o c a t i o n : ,2.3 k»* A/£ /V'W' * / Source Type: Qo/crap </~ Rock Types: A/nj /j-,/-'/* frTZjul.t-C Geologic U n i t : A ^ rJ, Geologic Setting: /nAroc/fS " VasfiauX. M a t e r i a l Analysed:  Comment on  Y*  ^  ¥  /•  x9  <4r/HS-fro 7  D  a  t  e  o  f  listing: 6  -  Sample Name o r Number:  bp 1 i tMlneral h»e  3/  /t?  ppm Pb  ppm U  '"lap /HI & ~f 206 Pb ^ r n n r ° ± r  a  t  ,  r-,«r  ppm U  (H-P)  3  f-Tne A/orttfay  /(, Y~<>  /o*o  0.017?C?  ±0.000/0  ppm U  Mineral  Coarse AJmMam  /(,. V « f /  iwir  „. ^  ±  raUo  00/9/3  bp 1 i tMineral  235 U  ±a.oo°/(  ppm U  206 Pb  /3//  r a t i  /oo .. . °t  S. H/9c? 207 Pb  ^  °±  c. 0 o j a 206 Pb j 238 u d  a  . t  -  e  207 Pb  206-pb  ., ,  r a t i  206  235 U  loTTb  rat  ± 0.0008 0.oS'YS3 206  207 Pb  rat,  U  0/3/9  Statement of Uncertainties:  r a t  0-3%  207 Pb j  . -  /2S.  d a t e  /  0  20(4  R  d a t e  6. ?7?  °±  3 00  207 PbA  206 Pb  d 3 t e  . -  ± /: 3.  mir  .  //y 7  207 Pb j  235 U  -  date  -A3.  d  ±o°o°o7  R  *  ?  206-Tb  ±0.0007  O 0S0G3  are.  r a t i o  ±  ±0.0000$  e  /J6.JT  nnr  d a t e  d a t e  . i  R  -  207 Pb j  206-Tb  d a t e  .  *  /</  Rad. Pb Common Meas. —,- Mole S 20T Blank Pb Rad+ComPb Pb Aqe M»=C  206  o.S%  O O O ? /  206 Pb . \  206-pb  0.3%  207 Pb , . . 235 U d a t e -  20<4  7 65 y * ., .  t  207 Pb j  Mole % Rad. Pb Common Blank Pb Rad+ComPt Pb Aqe  /<=2^?. Q ± /. y  208  207 Pb  a  . -  ps./ -/a 32 6./  20^  206 Pb . . 2W1T ±  '° ±  207  ^ '°±  d a t e  //,'C7  ., .  /oo  „, ^  76,  207 Pb j  Rad. Pb Common Meas. 206 Mole % 20T Blank Pb Rad+ComPt Pb Aqe  s'.S'ooy 207 Pb  r a t  ppm Pb  <5V? 235 U  //S- 6 - / 3.  208  207  /oo ... '° -  O.ZY3?  d a t e  206 Pb j  °±  ±600007  ±0 0007 Oo£2>9y  207 Pb  238 U  . -  o.?rs>  S-3V//  '° ±  0/3//  206 Pb j  3%  . 206" Pb + 6/ /22 c - /.a. 3/4.3 Mole * Rad. Pb Common Meas. ™ 20T Blank Pb Rad+ComPt: Pb Aqe  0 001 7  208  207  / o o r a t  ^ i ±0oeoe>7  O.  207 Pb . . ^ 235 U d a t e *-  20l»  y 3?Z3  r a t i o  O.CxS'Z9Y  206  235 U  208  206-pb  ±ooot>-)  /f-33 207 Pb  Tnr ±°6. ±ooo// 235 O-O / &7o ?1  206-Tb  r a t l  S Y S b - roo^  207 Pb  207  ppm Pb  ?S</  206 Pb  v y  7?  206  ppm Pb  .. . rat.o +  Sp 1 i t-  207 Pb  ±0.0oo/o  206 Pb  I T r j r  S~3/  Q ]  Rad. Pb Common Heas. 206 Mole $ Blank Pb Rad+ComPl Pb Aqe  20A  //3.9 -/a. ^  ppm U  208  207  207 Pb „. ^ 2 „ „ rat.o +  ppm Pb  206 Pb - i j—ratio +  bp 1i tMineral  206  ZOO  //33  X&/76  Sheet  to.oco/o  e>.oi7(,(>  bplitMlneral  VCOCfZ/S^  ^  ±  207 PbJ . . 235 U d a t e -  o.??y ZOO 207 Pb j . 206 Pb d a t C  /30.7 - / V / cr  ^rr-  /i5'/ot>,x  ra.Ac ~<2JL  I s o t o p i c c o m p o s i t i o n o f b l a n k : [ J j S - K Modern Pb ( 6 A : l 8 . 7 , 1/U : 15 j63, flA : 38 .63) o r P^f Other (6/'i:/?. ifl/h \ISS~1 Q/k -.TJ.oO ) I s o t o p i c c o m p o s i t i o n o f common Pb based on S-K growth c u r v e : 6A=11.152,' 7/^=12.998, 8/5=31.23 a t 3-7Ga w i t h 238U/20'(Pb=9.7'i, 232Th/20')Pb=37.19; decay c o n s t a n t s 0.155125, Q.39>h^, 137-88; o r Other (6/A: 1/k: 9,/k : )  145  (NTS Q~Mineral a n a l y s i s D • Concordia i n t e r p r e t a t i o n Q M i n e r a l or r o c k i s o c h r o n Upper I n t e r c e p t Sample Number(s) and R e f e r e n c e ( s ) Computed • Lab No: 2>P?3~ Assumed •  U  Ref:  &3L £ / 3  —DK  #yg^  2a e r r o r +  Ma  ^tXTJeiCS  Q„ />  Lower I n t e r c e p t Computed• Assumed •  V77T  Record No: S u i t e No: Sample Name:  2a e r r o r +  Ma  +  Ma  +  Ma  +  Ma  +  Ma  238 2 0 6 UPb date tI  D V  J  235.. 207_. , „ UPb date decay constant 2 0 7  • old:  0. 1537/0.9722/0.0499/137.8  •"new:  Pb/  2 0 6  Pb  date  0.155125/0.98485/0.049475/137.88 2 3 2  • other:  Th-  2 0 8  Pb  date  • not r e p o r t e d Number of P o i n t s  Latitude:  Longitude:  ( V ? ° & 3 ' ^ 0 "  N,  (X° "  / / ? ° < 5 / '  UMT Zone  N;  Y' W  Z"  or X°  (±  Province:  & -~(  Co., S t a t e  P^V /ic /on  (NTS  _Map Area  L o c a t i o n : JuarT.L'^/ /JAi - ~ 8 Km Source Type: A,,/rref Rock Types: a w e f - As* /i/e QfnitC Geologic U n i t / fj«i-/777/4/ ^/A^Cl973):ar^„if G e o l o g i c S e t t i n g : }*Aucl(><> _Jy&.rcJii±4- £*o<jp>. M a t e r i a l Analysed: jZ-irTetf  Comment on  VjOO/Z.  ); E l e v a t i o n :  ,R.  Sec.  Y.Y')  p/  (1:250,000)  Osoj/*ur. 3£' 7  J.  .  .  *f J m a r c h A / - f »  Analyses:  Interpretation:  Collected _ _ , . Dated by:  by:J?).  /$W/>.-?^  7> / JJ. /%„Ain3*r*  f  /?•/••  ds«<sA'0>r<> 7  /ViV*f  ^  Date of l i s t i n g6:  -  X,A cm  .  Sample Name o r Number:  /U/a'c/i&t  Spl1t-  J/. 9 ~? M i nera1 206 Pb  2lFl^  39.0*9  70 O  /?s~ .,  ^ a t , 0  O. O2£~09 bpli tMlneral  206  ppm Pb  ppm U  .  t  ±o. &oo/y  ppm U  207 Pb 235 U C>./7/3  .. ^ '° -  r a t  +  to.oaot  ppm Pb  3? 83 206 Pb ,, , j^j-jj-ratlo +  206  207  Pb 235 U  r a t  .. . '° ±  206 Pb  ..  2lFTT  ° i  r a t l  + SplitMineral  ppm U  206 Pb 2WTT Spli tMi nera1  ° t  2irnr  207 Pb 235 U  r a t  ., r a t l  . . . '° * + 206  207 Pb 235 U  r a t  +  ppm U  206 Pb  206  ppm Pb  „. r a t ,  ^O.ooof  ppm Pb  ppm U  Sheet  208  207  206-p¥  r a t  206 Pb j 238 U  „. ^ '° *  d  O.oYfS'3  to.ooooC  207  208  .. . '° ± +  ppm Pb  .  °^  206  207 Pb 235 U  +  r a t  . . . '° t +  20T  O. oo/S~  Y39/2  Y?7f?  207 Pb  a  t  e  .,  loTTb  r a t i o  .  i  iwir  ±  O.OY96/ ^O.ooccQ 208  207 Pb WTb  207 Pb  ., . ° t +  .  -  +  a  t  ,.  207 Pb  206 Pb . .  ^  '° t  i3inr  +  208  rat  . . .  d a t e  +  d  a  t  t  +  +  e  ±  R  *  ? Common Pb Aqe  207 Pb j 206-PF  .  d a t e  Mole X Rad. Pb Blank Pb Rad+ComPt  d  a  t  C  t  R  207 Pb . . 235 U d a t e  +  c  207 Pb j 206-pb + d  a  t  . t  K  Common Pb Aqe  207 Pb j 206-pb + d  e  a  t  e  . t  Mole % Rad. Pb Common Blank Pb Rad+ComPb Pb Aqe  20T  207 Pb j 235 U + d  Common Pb Aqe  Mole X Rad. Pb B l a n k Pb Rad+ComPt  206  „ 206 Meas. — , -  ^  d a t e  e  207 Pb j ^ , 235 U +  H  206 Pb .  . t  /7t>.?  ^  iTinr  t  '° t  a  / OO  207 Pb j , ' , 235 U ±  i  204  d  Mole X Rad. Pb Blank Pb Rad+ComPt  20T 8SC  Meas.  204  ± -AC  20T  rat  e  20T  2WTT  d a t e  206-pb  d  Meas. 206  206 Pb j  208  207  loTTb  204  r a t i  207  loTTb  d a t e  235 U  3f  206 Pb j  /60  o.n?  207 Pb j  Meas. 206  204  Common Pb Aqe  207 Pb . . ^ /60. £  /ST. 7 - / *  .  207  o./%  , -  O.0003 207 Pb  Mole X Rad. Pb Blank Pb Rad+ComPt  Meas. 206  204  /oo  0 . / 7 J ?  Spli tMineral  prasi'Se  a  t  e  . -  207 Pb j  206-Tb  d a t e  +  .  t  R  -w  Statement o f U n c e r t a i n t i e s :  £trc.r-<  aye  3 g-  o/ -/rS' a  /  <T  /£r  /So-fvp/c  rii//oS  Isotopic composition o f blank: Q ' Modern Pb ( 6 / 4 : 1 8 . 7 , 7/4 : 15 '63, 8/4 : 3 8 . 6 3 ) o r f ^ j o t h e r (6/4 :/7 7J~7/4 :/SS 78/4 : 37.06 I s o t o p i c c o m p o s i t i o n o f common Pb based on S-K growth c u r v e : 6/4=11.152, 7/4=12.998, 8/4=31.23 a t 3.7Ga w i t h 238U/204Pb=9.74, 2 3 2 T h / 2 0 4 P b = 3 7 - 1 9 ; decay c o n s t a n t s 0 . 1 5 5 1 2 5 , 0.98485, 1 3 7 - 8 8 ; o r Y~] Other ( 6 / 4 : 7/4: 8/4: ) S  K  )  147  U  /?/3  ^2  (NTS • Mineral analysis •Concordia interpretation • Mineral or rock isochron Upper I n t e r c e p t Sample Number(s) and R e f e r e n c e ( s ) Computed• Lab No: OsoynoS Assumed • Ref: /{ye* /f73 PL D rt^/l Lower I n t e r c e p t Computed • Assumed • Record No: 238,, 2 0 6 , S u i t e No: UPb date Sample Name:  T  —.DK ~"rD  2a e r r o r +  Ma 2a e r r o r Ma  D V  2 3 5  U-  2 0 7  Pb  +  Ma  +  Ma  +  Ma  +  Ma  date  decay constant 2 0 7  •  old:  0.1537/0.9722/0.0499/137.8  Q-riew:  2 0 6  Pb  date  0.155125/0.98485/0.049475/137.88 2 3 2  •  Pb/  other:  Th-  2 0 8  Pb  date '  • not r e p o r t e d Number of P o i n t s : n=:  Latitude:  (V?  Longitude:  °Or7.'  /O  "  N,  //f  ° J P S ~ ' / 0  UMT Zone Sec.  (X "  Y' W  Z"  (±  or X );  Elevation:,  Co.,  ,R.  (NTS  Y.Y')  Province:  N; , T  State  Map Area (1:250,000)  Pert//c/o^  Location: 3 JT/*I C/OIO«A>7/ /ro*, /oa/Coo/ Source Type: Rock Types: 9rt<?/Ss*~C 9rjttf»£//*r*'r f Geologic Unit : Unif 2i£ fiy4r?j l973)j Geologic S e t t i n g : i«-bu<Je< 4*, „,.l,L<+ ^ Q Q J > M a t e r i a l Analysed: JZ/'~e.at l  roa-dcui-  i  a  ^t^y.  3 j eai  r*  G«e/L<.s eV (DSoyaoS  in  o»  i  7-  '  _  '  /  Comment on  Analyses:  Interpretation:  C o l l e c t e d by: D  a  t  e  d  b  Y  :  R.L.  2±L  4r*HS-/rorl^  Park;nsnM  3  Date of l i s t i n g :  0  J  Qsoy  OB S  /^rA/rtScnT//?^  Sample Name o r Number: Split-  Fine  Afa<?. 27 <c ~9 J«o '266  2lB~U~ 003  r a t ,  ATS"  Split-  .  207  Pb  ° ±  2V,  U  pint A'»"/*f«^  206  Pb  2 l 8 - l ^  ' °  t  207  ±  Pb  206-Tb  ,, r  OOSIlg  a  t  ,  0  206  ppm P b  S7/  O' (t r»f  a  r  a  „.  _  °  i  t  ,  235  ±  207  U  r  a  t  IbTTb  ° ±  i  Pb  Pb  2ifnr  0 O 3 ' f ?  206  ppm P b  r  a  207 „  ° -  2  c-.Q3.o3  207 „  Pb . .  266 2TO-rat . o  Pb „. „ ratio  t  2  207  t  ±  Pb _ ratio  207  Split-  ppm U  206  Pb  2nnr  „. ratio  +  206  ppm P b  _  t  Statement o f U n c e r t a i n t i e s :  207  Pb  235  U  r  _  207  ' ° • +  ±  206-Tb  t  a  composition  o f b l a n k : __JS-K  Isotopic  composition  o f common Pb b a s e d  238U/204Pb=9.7'i, 232Th/204Pb=37-19; decay  Mole %  2W  0.7% _  235  U  t  a  t  e  „,  ,  °  t  U  ..  o. 000 5~ Pb j  °  d a t e  00. S  -  ,  -  e  O.  Pb . .  2iinr  _  d a t e  i  Common Pb A q e  207 P b j  IbTTb  Mole %  .  206  Rad. Pb  d  a  t  e  <Y(,S _  207  235  U  ±  loTTb  d  a  t  e  Mole %  Pb . „  Pb , .  ,  207  U  -  206-Tb  _  207  a  t  e  e  a  _ i  R  Common Pb A q e  Pb . . d  a  t  Rad. Pb  C  _ t  Common  B l a n k Pb Rad+ComPt  Pb _ . d  t  + Mole %  206 20T  235 U  t  a  Rad. Pb  235  d  d  B l a n k Pb Rad+ComPt  207  Meas.  Pb A q e  3. ° 1  Pb . .  t  e  ,  Pb A q e  207 Pb . ,  IbTTb  -  d  a  t  G  _ i  + :  -71  cia/Ts)  R  Common  +  Pb . ,  i T i n r  i  d a t e  /.OO  +  20*1  0  973 D 3 S ~  207  +  <r~  t  M e a s . 20&L 20?  204  206  t  /%  ,  23TTT  208  r a t I  Rad. Pb  B l a n k Pb Rad+ComPt  3  °* +  a  Meas. 206  206  A  7  J J Q  P 0 3 . 0 - a.. %  -a.3.  /3oS  r a t ,  d  .  *  d a t C  B l a n k Pb Rad+ComPt  -  d  Pb A q e  207 P b j  IbTTb 0  238 U  Pb ( 6 / ' 4 : l 8 . 7 ,  constants  2  t  208  on S-K g r o w t h  ±  o/oS~  O.  +  Modern  e  ' °  I 0~~  /So/pfi/C  -/o-y  •.fc--V'4.'  _____ Isotopic  t  Meas. 206  20k  to.0O»'t-  3-  a  Pb , .  Pb  e^or^ ore  ±  d  207  207  „. a  r  Pb  loTTb  U  .  207  . +  235  206 P b _ _  t  Pb  0.05-o6"^  206  _  -  208  loTTb  +  Mineral  e  Pb . .  _  207  ±000/VL  ppm Pb  ppm U  t  207  300. a. - <__<2_ ao/.g  7.  to-ee./7  a  ao/-7  . r a t ,  d  Common  o.a%  _  „.  H7C  7. S^f  Mi n e r a 1  238 u  Rad. Pb  B l a n k Pb Rad+ComPt  1/a.l  0 OOlCo Pb . „  y. 6363 _  Mole %  Meas.  2pF  208  207  /oo  3-7.7? 207 P b  .  ppm U  Mlneral  bpli t-  206  tcxeoo/g  Spli t-  20b  204  7.6 3?/ _  r  208  -«O«D/7  ppm U  Mineral  3  207  /oo  J  Pb  Sheet  206  ppm Pb  ppm U  Mineral  (j&oyooS y?e/SJ  : —  rezTitaS.  :  1/h : 15,^3,  curve:  8/4 :38.63)  or  Hither  (6/'(: / * 737/l(  7 8/4 J  7. OO )  6/4=11.152,' 7/4=12.998, 8/4=31.23 a t 3-7Ga w i t h  0.155125, 0 . 9 8 4 8 5 ,  137.88;  or  ["J  Other  (6/4:  7/4:  8/4:  )  149  APPENDIX C -  Rb  and  Sr  concentrations  were  RB/SR  determined by  pellets using X-ray fluorescence. U.S. calibration;  mass  scattering  absorption  measurements.  replicate analysis  ratios  were  obtained  have  a  concentrations a precision of 5% (1 sigma). Sr unspiked  samples  prepared  using  TECHNIQUES  of pressed powder  Geological Survey rock standards were used for  coefficients  Rb/Sr  ANALYTICAL  standard  from  precision  Mo of  K-alpha  2%  (1  sigma)  isotopic composition was ion  exchange  Compton and  measured on  techniques.  The  mass  spectrometer, a V.G. Isomass 54 R, has data aquisition digitized and automated using a H.P.  85 computer. Experimental  0.1194 and adjusted so  data have  that the NBS  been normalized to a  standard  SrC0  3  (SRM  987)  S6  Sr/ Sr 88  gives  a  ratio of !7  Sr/ Sr !6  ratio of 0.71020± 2 and the Eimer and Amend Sr a ratio of 0.7080012. The precision of a single  87  Sr/ Sr ratio is better than 0.00010 (1 sigma). Rb-Sr dates are based on 86  a Rb decay constant of 1.42 x 10" " y . The regressions are calculated according to the 1  technique of York (1967).  

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