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UBC Theses and Dissertations

Geochronology of the Clachnacudainn Gneiss, located near Revelstoke, B.C. Birnie, David John 1976

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GEOCHRONOLOGY OF THE CLACHNACUDAINN GNEISS, LOCATED NEAR REVELSTOKE, B.C. David John Birnie B.Sc., Queen's University at Kingston, 1972 A Thesis Submitted i n P a r t i a l Fulfilment of the Requirements f o r the Degree of Master of Science i n the Department of Geophysics We accept t h i s thesis as conforming to the required standard The U n i v e r s i t y of B r i t i s h Columbia May, 1976 In p r e s e n t i n g t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the r e q u i r e m e n t s f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h C o l u m b i a , I a g r ee t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r ag ree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t ten pe rm i ss i on . Depa rtment The U n i v e r s i t y o f B r i t i s h Co l umb i a 2075 Wesbrook Place Vancouver, Canada V6T 1W5 i i ABSTRACT K-Ar b i o t i t e ages and Rb-3r m i n e r a l i s o c h r o n ages i n d i c a t e t h a t a 55 m. y r . o l d T e r t i a r y thermal event has a f f e c t e d the rocks of the Clachnacudainn S a l i e n t of the Shuswap Metamorphic Complex. An attempt was made to date the Clachnacudainn Gneiss by the Rb-Sr whole rock method. I t was hoped t h a t t h i s study would provide some i n s i g h t i n t o the problem of determining the o r i g i n of the gneiss. However, the data shows considerable s c a t t e r v/ith no systematic p a t t e r n to i t . T h i s , together with petrographic evidence, suggests t h a t the cl o s e d system assumption has not been maintained. Thus no is o c h r o n could be determined. Several suggestions are presented to account f o r the s c a t t e r i n the data. i i i TABLE OF CONTENTS PAGE ABSTRACT i i ACKNOWLEDGEMENTS x i i i CHAPTER I INTRODUCTION 1 GENERAL STATEMENT 1 LOCATION AND ACCESS 1 PREVIOUS WORK 4 SAMPLING 5 CHAPTER I I GEOLOGICAL BACKGROUND 6 REGIONAL GEOLOGY 6 THEORIES OF ORIGIN OF THE GNEISS DOMES 15 GEOLOGY OF THE RSVELSTOKE-ALBERT CANYON AREA 19 DETAILED DESCRIPTION OF THE CLACHNACUDAINN GNEISS 26 CHAPTER I I I K-AR GEOCHRONOLOGY 34 CHAPTER IV RB-SR GEOCHRONOLOGY 38 INTRODUCTION 38 PREVIOUS RESULTS 4o NEW RESULTS 45 INTERPRETATION AND SIGNIFICANCE OF RESULTS 49 CHAPTER V GEOCHEMICAL CONSIDERATIONS 6 l CHAPTER VI CONCLUSIONS 67 REFERENCES 69 i v PAGE APPENDICES At LOCATION OF SAMPLE SITES 75 Bt BASIC THEORY OF RB-SR AND K-AR GEOCHRONOLOGY 77 INTRODUCTION 77 RB-SR METHOD 78 K-AR METHOD 85 C i MASS SPECTROMETRY 88 INTRODUCTION 88 GENERAL CONFIGURATION OF M.S.3 88 OPERATION OF THE MEASURING SYSTEM Q6 PERFORMANCE OF M.S.3 101 Dt X-RAY FLUORESCENCE METHOD 1 0 8 INTRODUCTION 108 THEORY 108 CALCULATION OF JUL 1 0 9 CALCULATION OF RB AND SR CONCENTRATIONS 1 1 5 ACCURACY OF THE METHOD 120 PRECISION OF THE METHOD 1 2 5 E i R3-SR METHOD 1 2 9 Ft PROGRAM LISTING S R 1 2 132 Gt K-AR METHOD 159 H i DETAILED EXPERIMENTAL DATA l 6 l SOLID SOURCE MASS SPECTROMETRY 161 Summary o f Dat a 161 V PAGE Spike and Standard C a l i b r a t i o n s 168 Blank A n a l y s i s 170 Data R e j e c t i o n 170 P r e c i s i o n and Accuracy 172 X-RAY FLUORESCENCE 175 GAS SOURCE MASS SPECTROMETRY 184 FLAME PHOTOMETRY 184 Ii STATISTICAL TECHNIQUES 191 FITTING OF STRAIGHT LINES TO DATA 191 ESTIMATES OF PRECISION FOR REPLICATE EXPERIMENTAL DATA 192 WEIGHTING OF EXPERIMENTAL DATA 1Q4 ANALYSIS CF RB-SR DATA CN A COMPSTON-JEFFERY PLOT v i LIST OF TABLES I I - l S i m p l i f i e d geologic tine scale and s t r a t i g r a p h i c table f o r the Kootenay Arc I I - 2 Duplicate whole rock analysis i n weight io oxides of sample Rl-T-2 I I I - l K-Ar r e s u l t s IV- 1 XRF Rb and Sr concentration r e s u l t s f o r Blenkinsop ( 1 . 9 7 2 ) samples of the Clachnacudainn Gneiss IV-2 Rb and Sr is o t o p i c r a t i o s f o r Blenkinsop (1972) Clachnacudainn Gneiss whole rock samples IV-3 Rb and Sr i s o t o p i c r a t i o s f o r Clachnacudainn Gneiss whole rock samples c o l l e c t e d f o r t h i s study IV-^ Rb and Sr i s o t o p i c r a t i o s f o r Clachnacudainn Gneiss mineral samples IV-5 Comparison of K-Ar age dates and Rb-Sr ages from mineral isochrons C-l Shunt c o e f f i c i e n t s f o r the ladder at t e nuat or i n Ivl. S. 3 C-2 Peak shape, res o l u t i o n and dispersion of M.S.3 i n the range of the strontium sp>ectrum D-l /Lvalues calculated at X = 0 . 7 5 A which have been used at 13. B.C. f o r various standards D-2 Compilation from the l i t e r a t u r e of best determined Rb and Sr concentrations f o r the eight standards used i n t h i s study D-3 Input data to the U.B.C. computer program which determines the various c a l i b r a t i o n l i n e s v i i D-4 R e s u l t s o f r u n n i n g the s t a n d a r d s as unknowns and u s i n g the i n p u t d a t a i n T a b l e D-3 D-5 P r e c i s i o n o f XRF d a t a as e s t i m a t e d by Youden's (1951) method o f p o o l i n g i n f o r m a t i o n from many s m a l l s e t s o f une q u a l s i z e s H - l Data from mass s p e c t r o m e t e r runs completed f o r t h i s s t u d y H-2 S t a t i s t i c s f o r (3r8?/Sr86)n r a t i o s c a l c u l a t e d f o r mass s p e c t r o m e t e r r u n s d e s c r i b e d i n Table II-1 K - 3 D a t a f o r the s t a n d a r d (3RM 98?) and s p i k e (3RK 988) s o l u t i o n s used f o r t h i s s t u d y H-4 O v e r a l l d a t a r e j e c t i o n s t a t i s t i c s H-5 Summary of a n a l y t i c a l p r e c i s i o n i n i n d i v i d u a l r u n s H-6 D u p l i c a t e a n a l y s e s o f s e v e r a l whole ro o k and p o t a s s i u m f e l d s p a r samples H-7 R e p l i c a t e measurements o f SRI-.J 987 s t a n d a r d H-8 XRF Rb and S r c o n c e n t r a t i o n r e s u l t s H-9 Comnarison of XRF r e s u l t s w i t h t h o s e of B l e n k i n s o p (1972) H-10 Comparison o f XRF Sr d e t e r m i n a t i o n s w i t h s p i k e d 3r84 mass s p e c t r o m e t r i c S r d e t e r m i n a t i o n s H - l l D e s c r i p t i o n of samples dated by the K-Ar method H-12 A n a l y t i c a l da/ta f o r K-Ar a n a l y s e s H - l 3 K c o n c e n t r a t i o n r e s u l t s o f m i n e r a l s e p a r a t e s v i i i PAGE H-14 K c o n c e n t r a t i o n r e s u l t s and K/Rb r a t i o s o f whole r o c k samples 189 GRAPHS - (-back p o c k e t ) GRAPH A 3PI p l o t f o r C l a c h n a c u d a i n n G n e i s s Rb-Sr whole r o c k d a t a GRAPH B M i n e r a l i s o c h r o n s f o r the C l a c h n a c u d a i n n G n e i s s GRAPH C C o m p s t o n - J e f f e r y p l o t f o r C l a c h n a c u d a i n n G n e i s s Rb-Sr whole r o c k d a t a GRAPH D E q u a l - a r e a d e n s i t y p l o t o f the i n t e r s e c t i o n p o i n t s of l i n e s i n Graph C i x LIST OF FIGURE 1-1 Mainr Q+v.,,rt+,,~„i _-, . - P A GE 2 1-2 Major s t r u c t u r a l elements of the Canadian C o r d i l l e r a L o c a t i o n of samples taken f o r t h i s study I I - l G e neralized g e o l o g i c a l map of southeastern B r i t i s h Columbia showing the occurrence of major- gneiss dome complexes and gneiss wedges I I - 2 G e n e r a l i z e d g e o l o g i c a l map of the Kootenay Arc I I - 3 Diagrammatic p o r t r a y a l of the development of the core zone, Thor-Odin gneiss dome 11-^ L i t h o l o g i c map of the Revelstoke-A l b e r t Canyon area I I - 5 Geologic map of the I l l e c i l l o w a e t V a l l e y near A l b e r t Canyon I I - 6 Schematic c r o s s - s e c t i o n A-A* across the Revelstoke segment of the Kootenay Arc I I - ? I d e a l i z e d block diagram along the l i n e B-B' i n d i c a t e d i n Figure I I - 6 Exposure of uniform g r a n o d i o r i t e gneiss at sample l o c a t i o n 33 Exposure of s w i r l e d g r a n o d i o r i t e gneiss at sample l o c a t i o n 36-3 11-10 Hand specimen sample of Bo-3 11-11 Hand specimen sample of 36-1 11-12 Hand specimen sample of R3-T 11-13 C a l c i t e a l t e r a t i o n i n sample R3-T I I - l ^ - Epidote r e a c t i o n run around a b i o t i t e or amphibole g r a i n i n sample B3 II-8 I I - 9 7 10 17 20 21 23 23 29 29 30 30 31 31 33 X PAGE I I - 15 M y r m e k i t i c t e x t u r e seen i n sample B6-3 33 I I I - l K-Ar i s o c h r o n p l o t f o r C l a c h n a c u d a i n n G n e i s s b i o t i t e samples 3? IV- 1 L o c a t i o n s o f samples o f the C l a c h n a c u d a i n n G n e i s s c o l l e c t e d by B l e n k i n s o p (1972) 41 IV-2 BPI p l o t f o r B l e n k i n s o p whole rook samples 44 IV-3 BPI p l o t f o r B l e n k i n s o p whole r o c k samples showing r e c a l c u l a t e d i s o c h r o n s u s i n g a d d i t i o n a l d a t a from t h i s s t u d y 46 I V - 4 BPI p l o t f o r whole r o c k samples c o l l e c t e d f o r t h i s s t u d y 48 IV-5 Rb-Sr m i n e r a l i s o c h r o n s f o r the C l a c h n a c u d a i n n G n e i s s 51 IV-6 BPI p l o t f o r a l l whole rock d a t a f o r the C l a c h n a c u d a i n n G n e i s s 5^ IV- 7 Three i s o c h r o n i n t e r p r e t a t i o n model f o r whole r o c k d a t a 57 V- l P l o t of s t r o n t i u m v e r s u s r u b i d i u m f o r C l a c h n a c u d a i n n G n e i s s whole r o c k samples 62 V-2 P l o t of p o t a s s i u m v e r s u s r u b i d i u m f o r C l a c h n a c u d a i n n G n e i s s whole r o c k samples 63 V - 3 P l o t o f K/Sr r a t i o s v e r s u s Rb/Sr r a t i o s f o r C l a c h n a c u d a i n n G n e i s s whole r o c k samples 64 V - 4 P l o t of K/Rb r a t i o s v e r s u s Sr/Rb r a t i o s f o r C l a c h n a c u d a i n n G n e i s s whole r o c k samples 65 B - l C o m p s t o n - J e f f e r y p l o t 79 B-2 BPI p l o t 80 B - 3 S t r o n t i u m e v o l u t i o n diagram showing the time e v o l u t i o n o f Sr87/Sr86 and Rb87./Sr86 81 x i PAGE B-4 S t r o n t i u m e v o l u t i o n diagrams showing the e f f e c t s o f i s o t o p i c h o r c o g e n i z a t i o n f o r a two e p i s o d e model f o r a t o t a l r o c k r and f o u r o f i t s c o n s t i t u t e n t m i n e r a l s m^, m £ i IT13 and m/4. 82 B-5 S t r o n t i u m e v o l u t i o n diagram f o r m i n e r a l phases and t o t a l r o c k s of d i f f e r e n t i n i t i a l Rb87/3r86 f o r a two e p i s o d e model 83 B-6 S t r o n t i u m e v o l u t i o n diagram showing the e f f e c t s o f c o n t a m i n a t i o n 84 B-? P l o t o f K-Ar d a t a f o r s e v e r a l samples from a o o g e n e t i c s u i t e o f r o c k s 86 B-8 A l t e r n a t i v e p l o t o f K-Ar dat a i o r s e v e r a l samples from a o o g e n e t i c s u i t e of r o c k s " 8? G-l Schematic diagram of M.S. 3 90 G-2 C o n f i g u r a t i o n o f a i r - o p e r a t e d v a l v e s on M.S.3^ * 91 C-3 M.S.3 s o u r c e and mounting assembly drawn a p p r o x i m a t e l y t o s c a l e 93 C-4 M.S.3 c o l l e c t o r and mounting assembly drawn a p p r o x i m a t e l y t o s c a l e 94 C-5 M e a s u r i n g system on M.S.3 95 C-6 D e f i n i t i o n o f terms used i n d e v e l o p i n g the t h e o r y o f o p e r a t i o n o f the m e a s u r i n g system shown i n F i g u r e C-5 98 C-7 F i r s t o r d e r d i r e c t i o n f o c u s i n g mass a n a l y z e r 102 C-8 Mass s p e c t r o g r a m w i t h two peaks r e p r e s e n t i n g atomic masses M and M+ /M 102 C-9 Mass s p e c t r o g r a m from M.S.3 showing s t r o n t i u m peaks 103 x i i P l o t o f Mo.?5 ( c a l c u l a t e d ) v e r s u s l/llV'oKGS f o r s t a n d a r d s r u n on Dec, 8, 1973 P l o t o f MO.75 ( c a l c u l a t e d ) v e r s u s l / l l l o K C S f o r s t a n d a r d s r u n on Feb, 9, 197^ Rb c a l i b r a t i o n l i n e used by the w r i t e r f o r Dec. 8, 1973 d a t a Rb c a l i b r a t i o n l i n e used by the w r i t e r f o r Feb. 9, 197^ d a t a S r c a l i b r a t i o n l i n e used by the w r i t e r f o r Dec. 8, 1973 d a t a S r c a l i b r a t i o n l i n e used by the w r i t e r f o r Feb. 9, 197^ d a t a P l o t o f Rb and S r c o n c e n t r a t i o n v e r s u s s t a n d a r d d e v i a t i o n f o r the d a t a i n T a b l e D~^ x i i i ACKNOWLEDGEMENTS The w r i t e r wishes t o e x p r e s s h i s s i n c e r e t h a n k s t o R. D. R u s s e l l f o r s u p e r v i s i o n of t h i s t h e s i s and f o r h i s h e l p f u l guidance d u r i n g a l l phases o f the r e s e a r c h . O t h e r c o l l e a g u e s who p r o v i d e d a s s i s t a n c e and encouragement i n c l u d e T. K. Ahern, P. C. LeC o u t e u r , J . E. H a r a k a l , V. B o b i c , R. D. Mel drum, V/. F. Slawson, J . V. Ross, and R. L. Armstrong. The s u p p o r t g i v e n me by my w i f e d u r i n g t h e w r i t i n g o f t h i s t h e s i s i s g r e a t l y a p p r e c i a t e d . T h i s r e s e a r c h and the mass s p e c t r o m e t e r l a b o r a t o r y have been f i n a n c i a l l y s u p p o r t e d by the N a t i o n a l R e s e a r c h C o u n c i l o f Canada under Grant No. A-720. The w r i t e r a l s o w i s h e s t o thank the N a t i o n a l Research C o u n c i l f o r p e r s o n a l s u p p o r t i n the form of a p o s t - g r a d u a t e s c h o l a r s h i p . 1 CHAPTER I INTRODUCTION GENERAL STATEMENT The main o b j e c t i v e of t h i s i n v e s t i g a t i o n i s t o determine the K-Ar and Rb-Sr ages o f the C l a c h n a c u d a i n n G n e i s s , l o c a t e d n e a r R e v e l s t o k e , B r i t i s h C o l u m b i a , The age has i m p o r t a n t i m p l i c a t i o n s w i t h r e g a r d t o the p o s s i b l e o r i g i n o f the g n e i s s . P r e l i m i n a r y Rb-Sr whole r o c k d a t a o b t a i n e d by B l e n k i n s o p (19? 2 ) have s u g g e s t e d t h a t the g n e i s s may be P r e c a m b r i a n i n age; however, the i n t e r p r e t a t i o n of h i s d a t a i s ambiguous. T h i s s t u d y a t t e m p t s t o d e f i n e e x a c t l y what one can say about the g n e i s s ' s age from the K-Ar and Rb-Sr methods. I t i n v o l v e s a n a l y s e s o f m i n e r a l s e p a r a t e s and whole r o c k samples o f the g n e i s s . C o n s i d e r a t i o n i s a l s o g i v e n t o t h e l o c a t i o n end v a r i a t i o n o f p o t a s s i u m , r u b i d i u m and s t r o n t i u m i n the g n e i s s . I n a d d i t i o n , t h e r e i s a b r i e f d i s c u s s i o n o f the K-Ar age dates o f i n t r u s i v e r o c k s i n the a r e a , LOCATION AND ACCESS The C l a c h n a c u d a i n n G n e i s s i s l o c a t e d w i t h i n the C l a c h n a c u d a i n n S a l i e n t of the Shuswa/p Metamorphic Complex, n o r t h e a s t o f R e v e l s t o k e , B r i t i s h C o lumbia. The Shuswap Metamorphic Complex i s an e x t e n s i v e b e l t o f h i g h - g r a d e , h i g h l y deformed metamorphic r o c k s i n s o u t h e a s t e r n B r i t i s h 2 SEFB _ S t . E l i a s F o l d B e l t YCP - Yukon C r y s t a l l i n e P l a t f o r m MAG - M a c k e n z i e A r c Core Zone MA - M a c k e n z i e A r c CGW - C o l u m b i a n C l a s t i c Wedge FTFB - F o r e l a n d T h r u s t and F o l d B e l t OGB - Omineca C r y s t a l l i n e B e l t PA - P u r c e l l A n t i c l i n o r i u m KA - K o o t e n a y A r c SMG - Shuswap Metamorphic Complex HB - H i n t e r l a n d B e l t BB - Bowser B a s i n ITFB I n t e r m o n t a n e T h r u s t and F o l d B e l t GFB - Cascade F o l d B e l t CPG - C o a s t P l u t o n i c Complex IB - I n s u l a r B e l t I T F B \ \ 0 C ^ \ . ^ " " ' - - P G W ^ C l a c h n a c u d a i n n S a l i e n t CPG •:. \ '''ft FTFB\ I \%k \ ) \ / P a c i f i c - « A « * — C o l u m b i a n Orogen \ Orogen FIGURE I - l i M a j o r s t r u c t u r a l e l e m e n t s o f t h e C a n a d i a n C o r d i l l e r a ( a f t e r Wheeler and G a b r i e l s e , 1 9 ?2). The C l a c h n a c u d a i n n G n e i s s i s l o c a t e d w i t h i n t h e C l a c h n a c u d a i n n S a l i e n t o f t h e Shuswap Metamorphic Complex. The g e o l o g y o f the shaded a r e a i s shown i n F i g u r e I l - t . 3 Columbia i n the core zone of the Columbian Orogen (see Figu r e 1-1). Figure 1-2 shows the gneiss on Ross's (1968) . g e o l o g i c a l map of the R e v e l s t o k e - A l b e r t Canyon area, G i l n a n (1972) has mapped the ext e n s i o n of the gneiss southward across the I l l e c i l l e w a e t R i v e r . The d e t a i l e d g e o l o g i c a l s e t t i n g of the r e g i o n w i l l be considered i n Chapter I I . Access t o the gneiss i s a v a i l a b l e along the Trans-Canada Highway west of A l b e r t Canyon where e x c e l l e n t outcrop exposures e x i s t . There i s a l s o an o l d mining road which branches o f f the B i g Bend Highway i n the northwest of the area and f o l l o w s La. Forme Creek to exposures of the gneiss. PREVIOUS WORK Previous g e o l o g i c a l work of a reconnaissance nature i n the general area of the gneiss i n c l u d e s t h a t of Dawson ( 1 8 9 1 ) , Daly ( 1 9 1 5 ) . Gunning ( 1 9 2 9 ) , O k u l i t c h (19^9) and Wheeler ( 1 9 6 3 i 1 9 6 5 ) . D e t a i l e d work d e s c r i b i n g the g e o l o g i c a l and s t r u c t u r a l r e l a t i o n s h i p s i n and around the gneiss i n c l u d e s t h a t of Ross ( 1968) and Gilman ( 1 9 7 2 ) . P u b l i c a t i o n s by Wheeler ( 1 9 6 5 , 1 9 7 0 ) , Ross ( 1 9 7 0 ) , Ross and K e l l e r h a l s ( 1 9 6 8 ) , Reesor ( I 9 6 5 i 1 9 7 0 ) , Reesor and Moore ( 1 9 7 1 ) , F y l e s ( 1 9 7 0 a , 1970b), M c M i l l a n (1.970, 1 9 7 3 ) , and v a r i o u s papers c i t e d by them d i s c u s s the Shuswap Metamorphic Complex west of the Columbia R i v e r . The only previous g e o c h r o n o l o g i c a l work on the F IGURE J-2; L o c a t i o n o f samples t a k e n f o r t h i s s t u d y . T h i s g e o l o g i c a l map i s from Ross (1968) and shows t h e C l a c h n a c u d a i n n g n e i s s as c o l o u r e d . 5 C l a c h n a c u d a i n n G n e i s s i s t h e Rb-Sr whole r o c k s t u d y o f B l e n k i n s o p ( 1 9 7 2 ) . O t h e r Rb-Sr whole r o c k work i n t h e a r e a o f t h e Shuswap Metamorphic Complex i s l i m i t e d t o B l e n k i n s o p ' s (1972) s t u d y o f t h e M a l t o n and Quesnel Lake G n e i s s e s and Ryan's ( 1973) s t u d y i n t h e A n a r c h i s t M o u n t a i n a r e a , s o u t h -e a s t e r n B r i t i s h C o l u m b i a . Other g e o c h r o n o l o g i c a l d a t a i n c l u d e s a m u l t i t u d e o f K-Ar age da t e s f o r p l u t o n i c r o c k s and g n e i s s e s i n the Shuswap Complex ( G a b r i e l s e and Re e s o r , 196^; V/anless, 1 9 o 9 ) « and a v e r y few z i r c o n d a t e s (see C h a p t e r I I ) . SAMPLING D u r i n g J u l y , 1973 t w e n t y - t h r e e samples were c o l l e c t e d by the w r i t e r from o u t c r o p exposures a l o n g the Trans-Canada Highway, t h e B i g Bend Highway, and the L a Forme Creek bush r o a d . The approximate l o c a t i o n s of sample s i t e s are shown i n F i g u r e 1-2 and t h e d e t a i l e d l o c a t i o n s are d e s c r i b e d i n Appendix A. Sample s i z e s ranged from a p p r o x i m a t e l y 20 t o 50 Kgm. S i n c e the m a j o r i t y o f sarqoles came from r o c k c u t s , the w r i t e r was g e n e r a l l y a b l e t o o b t a i n samples o f f r e s h , unwea.thered r o c k . I t s h o u l d be n o t e d , however, t h a t samples from e x p o s u r e s a l o n g the La Forme Creek bush r o a d were o f p o o r e r q u a l i t y t h a n o t h e r s o b t a i n e d . Sample prepara.ti.on f o l l o w e d the p r o c e d u r e s o u t l i n e d i n Ryan ( 1 9 7 3 ) . 6 CHAPTER I I GEOLOGICAL BACKGROUND REGIONAL GEOLOGY The major s t r u c t u r a l elements o f s o u t h e a s t e r n B r i t i s h C o l u m b i a i n c l u d e t h e P u r c e l l A n t i c l i n o r i u m , the Kootenay A r c and the Shuswap Metamorphic Complex. The l a t t e r two compose the s o u t h e r n e x t e n s i o n o f the Omineca C r y s t a l l i n e B e l t , a l o n g i t u d i n a l s t r u c t u r a l p r o v i n c e which composes the v a r i a b l y deformed cor e zone o f the Columbian Orogen. F i g u r e I I - l i s a g e n e r a l i z e d g e o l o g i c a l map o f the r e g i o n . The P u r c e l l A n t i c l i n o r i u m i s p r i m a r i l y composed o f sediments o f t h e P u r c e l l ( B e l t ) System, t h e age o f which i s known o n l y w i t h i n b r o a d l i m i t s . A v a i l a b l e e v i d e n c e i n d i c a t e s t h a t P u r c e l l s e d i m e n t a t i o n t o o k p l a c e betv/een about 850 and 1^5° m. y r . ago w i t h the b a s a l s t r a t a b e i n g d e p o s i t e d on c r y s t a l l i n e basement h a v i n g a minimum age o f 1600 m. y r . ( G a b r i e l s e , 1 9 7 2 ) . The E a s t Kootenay Orogeny ( W h i t e , 1959) i s r e g a r d e d as an e p i s o d e o f r e g i o n a l u p l i f t accompanied by r e g i o n a l metamorphism and minor f o l d i n g t h a t t e r m i n a t e d t h e l o n g p e r i o d of P u r c e l l s e d i m e n t a t i o n . I t r e s u l t e d i n an u n c o n f o r m i t y between P u r c e l l s t r a t a and the o v e r l a i n s t r a t a o f the Windermere System. G a b r i e l s e (1972) s u g g e s t s t h a t the Windermere System was d e p o s i t e d r e l a t i v e l y r a p i d l y d u r i n g the i n t e r v a l o f a p p r o x i m a t e l y 800 t o 600 m. y r . However, M i l l e r e t a l . (1973) have more r e c e n t l y p u b l i s h e d K-Ar d a t e s o f QL Quesnel Lake G n e i s s MG M a l t o n G n e i s s FC Frenchman's Cap TR T h o r - O d i n P P i n n a c l e s V V a l h a l l a FIGURE I l - l t G e n e r a l i z e d g e o l o g i c a l map o f s o u t h e a s t e r n B r i t i s h C o l u m b i a s h o w i n g t h e o c c u r r e n c e o f major g n e i s s dome complexes and g n e i s s wedges ( a f t e r R e e s o r , 1 9 7 0 ) . O n l y t h e s o u t h e a s t e r n t i p o f t h e Quesnel Lake G n e i s s i s seen on t h i s map (see C a m p b e l l , 1 9 7 3 ) . 8 800-900 m. y r . f o r b a s a l t from the middle p a r t of the Windermere System i n northeastern Washington. Thus, although the p r e c i s e t i m i n g of the East Kootenay Orogeny i s unknown, i t i s reasonably expected t o have occurred between 900 and 600 m. y r . ago. Blenkinsop (1972) p o i n t e d out t h a t the East Kootenay Orogeny may have encompassed m u l t i p l e events extending over a considerable p e r i o d of time ( i n the order of 100 m. y r . ) , and thus a spread o r smearing of r a d i o m e t r i c age dates may be expected. He obtained Rb-Sr whole rock ages of 7^0 t 30 m. y r . , 7^0 ± 150 m. y r . and 680 ± 80 m. y r . f o r the Clachnacudainn Gneiss, the Quesnel Lake Gneiss and the Malton Gneiss r e s p e c t i v e l y . Although the r e l i a b i l i t y of these dates i s quest i o n a b l e because of the s c a t t e r i n the data (see Chapter I V ) , Blenkinsop (1972) has t e n t a t i v e l y c o r r e l a t e d them w i t h the East Kootenay Orogeny. He p o i n t s out t h a t i f the c o r r e l a t i o n i s v a l i d the orogeny was more extensive than p r e v i o u s l y thought. Blenkinsop's (1972) age dates are c o n s i s t e n t w i t h s e v e r a l K-Ar ages of 700-800 m. y r . ( G o l d r i c h e t a l . , 1959; Lowdon, 1961; Leech, 1962; Hunt, 1962; Wanless et a l . , I967) of r e g i o n a l l y metamorphosed rocks and of stocks thought t o have been i n t r u d e d d u r i n g the orogeny. However, i t i s u n c e r t a i n whether these dates represent an age of i n t r u s i o n as w e l l as an age of metamorphism. Ryan and Blenkinsop (1971) obtained a Rb-Sr age of 1300 1 100 m. y r . f o r a stock p r e v i o u s l y dated by the 9 K-Ar method a t ? 0 5 m. y r . (Lowdon, 1961) and 769 m. y r . (Hunt, 1 9 6 2 ) . Campbell (1973) has r e p o r t e d a Pb207/Pb206 age o f 722 m. y r . from z i r c o n s from a s i n g l e sample o f the M a l t o n G n e i s s , but the d a t a s u g g e s t t h a t the system has s u f f e r e d a l o s s o f l e a d , i n d i c a t i n g t h a t t h e t r u e age i s l i k e l y o l d e r . The Kootenay A rc (see F i g u r e I I - 2 ) i s a narrow c u r v i n g o s t r u c t u r a l b e l t w h i c h c o m p r i s e s r o c k s r a n g i n g i n age from l a t e P r e c a m b r i a n (Windermere) t o T r i a s s i c ( R o s s , 1970; Wheeler, 1 9 ? 0 ) . T a b l e I I - l summarizes the s t r a t i g r a p h y o f the A r c . The s t r u c t u r e w i t h i n t h e Arc i s b o t h complex and v a r i a b l e , t h e r o c k s h a v i n g undergone p o l y p h a s e d e f o r m a t i o n . A l l of the r o c k s are variab3.y metamorphosed from the l o w e r g r e e n s c h i s t t o upper a m p h i b o l i t e f a c i e s . A s e r i e s o f p o s t -t e c t o n i c i n t r u s i v e r o c k s , the l a r g e s t o f w h i c h are the N e l s o n and Kuskanex 3 a t h o l i t h s c o m p l i c a t e the g e o l o g y o f the A r c . The N e l s o n B a t h o l i t h has been da t e d a t 165 m. y r . by Nguyen e t a l , ( 1 9 6 8 ) . E v i d e n c e from l e a d i s o t o p e s t u d i e s o f g a l e n a s from the A r c ( S i n c l a i r , 1966; Reynolds and S i n c l a i r , 1971 ; L e C o u t e u r , 1973) s u g g e s t s t h a t the basement beneath the A r c i s a s o u r c e o f r a d i o g e n i c l e a d whose age i s a p p r o x i m a t e l y 1 5 0 0 - 1 7 0 0 m. y r . The Shuswap Metamorphic Complex i s a narrow b e l t o f i n t e n s e l y deformed h i g h - g r a d e metamorphic r o c k s . R e g i o n a l metamorphism i s c h a r a c t e r i s t i c a l l y o f the upper a m p h i b o l i t e 1-2 i Generalized geological map of the Kootenay Arc — ( a f t e r Ross, 1970). I n d i c a t e d are the map-areas o f Ross ( 1968) and G i l m a n ( 1972) w h i c h are shown i n F i g u r e s I I - 4 and I I - 5 r e s p e c t i v e l y . The approximate l o c a t i o n o f g e o l o g i c c r o s s s e c t i o n A-A' (see F i g u r e I I - 6 ) i s g i v e n . TIME ERA (m. y r . ) 0-2-] 65-70-135-135-195-225-230-280-285-PERIOD STRATIGRAPHY EVENTS OF REGIONAL IMPORTANCE 3^5-350-395-405-440-500-570-600-800-950-1450-1735-TABLE I I - l : MESOZOIC PALEOZOIC Quntr?rnnry T o r t i 3 r y Cretaceous T r i a s s i c Permian Pennsylvania! -: K i s s i r ; s i p p i a n Devonian Silurian O r d o v i c i a n Cambrian j ( i n t r u s i o n of Nelson _ (BatholSth 165 m. yr. QC-ART Sloc.'in Group ? K o s l o Formation . M i l f o r d Group Lardeau Group Badshot Formation main Shuswap r e g i o n a l mctamorphism (Ressor, 1970) U T t-^main Shuswap metamort>hism (Ross, 1970) F2' F l Windermere System Purceil System H o r s e t h i e f Creek Group East Kootenay Orogeny I Hudsonian Orogeny ~J (Canadian S h i e l d ) S i m p l i f i e d g e o l o g i c time s c a l e and s t r a t i g r a r j h i c t a b l e f o r the Kootenay A r c ( a f t e r Ross, 1970). E v e n t s o f r e g i o n a l i m p o r t a n c e and_the approximate t i m i n g o f Ross's d e f o r m a t i o n phases are i n d i c a t e d . U n c o n f o r m i t i e s are i n d i c a t e d by t h e w i g g l y l i n e s . The c o l o u r scheme i s the same as i n F i g u r e I I - 2 . 12 f a c i e s and t h u s the b o u n d a r i e s o f the Complex g e n e r a l l y c o i n c i d e w i t h the s i l l i m a n i t e i s o g r a d . Most o f the r o c k s c o n t a i n e x t e n s i v e l a y e r s and l e n s e s o f p e g m a t i t e and l e u c o g r a n i t e . A l o n g the e a s t e r n m a r g i n o f the Complex i s a s e r i e s o f g n e i s s domes spaced a t 30 t o 50 m i l e i n t e r v a l s (see F i g u r e I I - l ) . S t u d i e s o f the V a l h a l l a ( R e e s o r , 1 9 6 5 ) , T h o r - O d i n ( R e e s o r , 1970; Reesor and Moore, 1971) and Frenchman's Cap ( F y l e s , 1 9 7 0 a ; M c M i l l i n , 1 9 7 0 , 1973) g n e i s s domes have shown t h a t t h e y have m i g m a t i t i c g r a n i t o i d c o r e s m a n t l e d by met a s e d i m e n t a r y g n e i s s e s . a n d s c h i s t s . The C l a c h n a c u d a i n n G n e i s s (Ross, 1 9 6 8 ; G i l m a n , 1972) i s s i m i l a r t o t he core zone g n e i s s e s . M e t a s e d i m e n t a r y r o c k s c r o s s the c u l m i n a t i o n o f the P i n n a c l e s dome and the g r a n i t o i d core p r e s u m a b l y l i e s a t depth ( R e e s o r , 1 9 7 0 ) . I t has p r o v e d d i f f i c u l t b o t h t o dete r m i n e the ages o f many r o c k s w i t h i n the Shuswap Complex as v / e l l as t o c o r r e l a t e them w i t h f o r m a t i o n s beyond. M e t a s e d i m e n t a r y r o c k s t h a t m a n t l e the g n e i s s domes are a p p a r e n t l y d e r i v e d from r o c k s t h a t are s t r a t i g r a p h i c a l l y e q u i v a l e n t t o t h o s e o f the P a l e o z o i c and p o s s i b l y Windermere ( l a t e P r e c a m b r i a n ) s u c c e s s i o n s (see Ta b l e I I - l ) o f the P u r c e l l - S e l k i r k M o u n t a i n s t o t he e a s t . However, the age and g e n e s i s o f the g n e i s s e s i n the core zones o f the domes are c o n t r o v e r s i a l . T h e i r complex metamorphic and d e f o r m a t i o n a l h i s t o r y make them d i f f i c u l t t o date from g e o l o g i c e v i d e n c e a l o n e ; t h u s , t h e r e has been a 13 c o n t i n u i n g e f f o r t t o date them r a d i o m e t r i c a l l y , Ross (1968, 1970) and Reesor (1970) have p r e s e n t e d two d i f f e r e n t h y p o theses f o r t h e i r o r i g i n . Ross has s u g g e s t e d , cased on h i s i n t e r p r e t a t i o n o f the d e f o r m a t i o n a l h i s t o r y o f the a r e a , t h a t t h e core g n e i s s e s were p o s s i b l y d e r i v e d from Hudsonian c r y s t a l l i n e basement r o c k s and were t e c t o n i c a l l y emplaced. Reesor f a v o u r s the p o s s i b i l i t y t h a t the m i g m a t i t e s were d e r i v e d from r o c k s o f the Windermere s u c c e s s i o n d u r i n g r e g i o n a l metamorphism. These t h e o r i e s w i l l be d i s c u s s e d i n more d e t a i l i n the n e x t s e c t i o n . The t i m i n g o f the r e g i o n a l metamorphism o f t h e Shuswap Complex i s a t p r e s e n t based on s t r s t i g r a p h i c d a t a . Ross and K e l l e r h a l s ( 1968) and Ross (1970) p l a c e i t as p o s t - M i l f o r d Group ( C a r b o n i f e r o u s , ( ? ) 3 a r l y Permian) and p r e - S l o c a n Group ( L a t e T r i a s s i c ) . R e e s o r ( 1970) and Reesor and Moore (1971) p l a c e i t as p o s t - M i l f o r d Group ( M i s s i s s i p p i a n ) , p o s s i b l y p o s t - S l o c a n Group ( T r i a s s i c ) , and p r e - T e r t i a r y . Thus Ross s e t s the main Shuswap metamorphism as p r e - M e s o z o i c w h i l e Reesor i n c l u d e s the p o s s i b i l i t y o f a M e s o z o i c age (see T a b l e I I - l ) . C a m pbell ( 1973) has proposed a model f o r the d e v e l o p -ment o f the s o u t h e a s t e r n C a n a d i a n C o r d i l l e r a t h a t i n v o l v e s a fu n d a m e n t a l change i n s t r u c t u r a l c h a r a c t e r f rom basement i n v o l v e m e n t i n the w e s t e r n C o r d i l l e r a t o no basement i n v o l v e m e n t i n t h e e a s t e r n C o r d i l l e r a , He p r o p o s e s t h a t such 14 a change t a k e s p l a c e p o s s i b l y a l o n g a group o f m a j o r f a u l t s (the U p l i f t Boundary F a u l t System) t h a t s e p a r a t e the M a i n and F r o n t Ranges i n t h e s o u t h e r n R o c k i e s . He s u g g e s t s t h a t west o f t h i s boundary m o b i l i z e d c r y s t a l l i n e basement was d i r e c t l y i n v o l v e d i n the d e f o r m a t i o n o f o v e r l y i n g s t r a t a . C a mpbell ( 1973) d e f i n e s basement as h a v i n g been made up o f deformed and p o s s i b l y metamorphosed pre-V/indermere ( P u r c e l l ) s t r a t a ( i . e . , p a r a g n e i s s e s ) p l u s deeper o l d e r c r y s t a l l i n e r o c k s (Hudsonian basement). The d i s t i n c t i o n between the two was t h e n l o s t w i t h i n a zone o f m o b i l i z a t i o n and m e l t i n g . The i n v o l v e m e n t o f basement i n c l u d e d d i a p i r i s m and t h e development o f g n e i s s t o n g u e s , which domed the c o v e r r o c k s i n t h e Shuswap Complex, as w e l l as t h e upward movement o f more b r i t t l e g n e i s s wedges such as the M a l t o n G n e i s s . Campbell (1973) c i t e s t he C l a c h n a c u d a i n n G n e i s s (Ross, 1 9 6 8 ; Gilman, 1 9 7 2 ) , the Quesnel Lake G n e i s s ( C a m p b e l l and Ca m p b e l l , 1970; F l e t c h e r , 1972) and the M a l t o n G n e i s s ( C a m p b e l l , 1 9 6 8 ; G i o v a n e l l a , 1968) as t h r e e s u c h o c c u r r e n c e s o f c r y s t a l l i n e basement. As p r e v i o u s l y m e n t i o n e d , a l l have a p p a r e n t Rb-Sr ages o f 6 0 0 - 9 0 0 m. y r . Campbell ( 1973) b e l i e v e s t h a t the d e f o r m a t i o n i n the Cmineca C r y s t a l l i n e B e l t and M a i n Ranges i s dominated by v e r t i c a l movements o f the e n t i r e c r u s t and t h a t a t r a n s i t i o n from p l a s t i c t o b r i t t l e s t r u c t u r e s i n v o l v i n g the basement t r e n d s outwards from t h e a x i s o f t h e core zone. T h i s i s i n c o n t r a s t t o the 15 d e f o r m a t i o n i n the F r o n t Ranges and F o o t h i l l s w h i c h i n v o l v e s m a j o r h o r i z o n t a l movements ( i . e . , e a s t e r l y d i r e c t e d o v e r -t h r u s t i n g ) o f c o v e r r o c k s o v e r a p a s s i v e basement. THEORIES OF ORIGIN OF THE GNEISS DOMES Opposing v i e w s r e g a r d i n g the o r i g i n s o f the g n e i s s dome complexes a l o n g the e a s t e r n m a r g i n o f t h e Shuswap Complex have been put f o r t h by Ross (Ross, 1 9 6 8 ; Ross, 1970; Ross and K e l l e r h a l s , I 9 6 8 ) and Re.esor ( R e e s o r , 1 9 ? 0 ; Reesor and Moore, 1971). Ross has i n t e r p r e t a t e d t h r e e phases of d e f o r m a t i o n i n the Kootenay A r c and the e a s t e r n Shuswap Complex. B e f o r e o r v e r y e a r l y i n the f i r s t phase, basement, p o s s i b l y H u d s o n i a n i n age, became i n v o l v e d i n the d e f o r m a t i o n o f t h e c o v e r s e d i m e n t a r y r o c k s , The e v i d e n c e f o r t h i s i s given, i n t h e n e x t s e c t i o n i n c o n j u n c t i o n w i t h a d e t a i l e d d i s c u s s i o n o f t h e s t r u c t u r a l r e l a t i o n s w i t h i n and around the C l a c h n a c u d a i n n G n e i s s , The f i r s t o r main phase of d e f o r m a t i o n began a t some tim e a f t e r t h e l a t e E a r l y Cambrian ( p o s t - e a r l y L a r d e a u Group) and prod u c e d l a r g e e a s t e r l y - v e r g i n g recumbent f o l d s o r nappes, c o r e d i n t h e i r a n t i c l i n a l p a r t s by basement g n e i s s . Phase 2 d e f o r m a t i o n , dated as p o s t - ( ? ) E a r l y P e r m i a n ( p o s t -M i l f o r d Group) and p r e - L a t e T r i a s s i c ( p r e - S l o c a n G r o u p ) , caused r e f o l d i n g o f the nappes about d i f f e r e n t a x i a l p l a n e s . T h i s second phase of d e f o r m a t i o n i s b e l i e v e d t o have d e v e l o p e d as a r e s u l t o f c r o w d i n g o f phase 1 nappes a g a i n s t 16 t h e more r i g i d P u r c e l l basement. Ross has p r o p o s e d t h a t t h e i n t e r f e r e n c e o f phase 1 and phase 2 f o l d i n g causes the major s t r u c t u r e s t o c u l m i n a t e and depress a l o n g s t r i k e t o produce a s e r i e s o f b a s i n s and domes. E r o s i o n has subsequently-exposed basement i n the core zones o f the g n e i s s domes. The t h i r d phase o f d e f o r m a t i o n r e s u l t i n g i n b a c k f o l d i n g o f t h e nappes, th e f i n a l s t a g e o f r e a c t i o n o f e a s t e r l y - m o v i n g nappes a g a i n s t the P u r c e l l A n t i c l i n o r i u m . The t i m i n g o f t h i s l a s t phase i s p o s t - L a t e T r i a s s i c ( S l o c a n Group) but b e f o r e the i n t r u s i o n o f the N e l s o n B a t h o l i t h . Each of the above phases o f d e f o r m a t i o n was accompanied by metamorphism, the main r e g i o n a l a m p h i b o l i t e f a c i e s metamorphism accompanying phase 2 . Reesor has p r o p o s e d a d i f f e r e n t o r i g i n f o r the g n e i s s domes. H i s v i e w of the s c e n a r i o of e v e n t s began w i t h the appearance of a narrow, n o r t h t o n o r t h w e s t e r l y - t r e n d i n g zone o f h i g h heat f l o w . High-grade r e g i o n a l metamorphic c o n d i t i o n s , accompanied by m i g m a t i z a t i o n , were t h u s p r e s e n t d u r i n g the e a r l i e s t r e c o g n i z e d phase o f d e f o r m a t i o n . The f i r s t event i n t h e s t r u c t u r a l development of the core zone was the i n t e r -f o l d i n g o f core zone g n e i s s e s and m i g m a t i t e s w i t h o v e r l y i n g m a n t l i n g g n e i s s e s on a s c a l e o f thousands of f e e t (see F i g u r e I I - 3 a ) . The f o l d s p e r m i t t e d l o c a l u p w e l l i n g of h o t , m o b i l i z e d core zone m a t e r i a l beneath e a s t e r l y - t r e n d i n g a n t i f o r m s . A p r o g r e s s i v e i n c r e a s e i n the m o b i l i t y o f the core zone l e a d t o a second s t a g e o f movement i n v o l v i n g a d i a p i r i c 17 mm 5$ a. End of phase I interfolding of core-zone and mantling gneiss 1.5 ml. I I Mantling zone rvV'"v;--;] Core zone i \ X X V Augen granodiorite gneiss FIGURE II-3» D i a g r a m m a t i c p o r t r a y a l o f the development o f t h e core zone, T h o r - O d i n g n e i s s dome ( a f t e r R e e s o r , 1970). 18 u p r i s e , s e v e r a l m i l e s i n e x t e n t , o f m i g m a t i t e and g r a n i t i c g n e i s s beneath the a n t i f o r m s (see F i g u r e I I - 3 b ) . T h i s l a s t phase o f movement c o r r e s p o n d e d w i t h b o t h the maximum i n t e n s i t y o f s t r u c t u r a l d i s r u p t i o n and g r e a t e s t e x t e n t o f metamorphism and was r e s p o n s i b l e f o r p r o d u c i n g the domes. R e s s o r f e e l s t h a t the boundary between the core g n e i s s e s and the m a n t l i n g g n e i s s e s c o u l d r e p r e s e n t the c o n t r a s t i n g s e d i m e n t a r y s u c c e s s i o n s o f l a t e P r e c a m b r i a n (Windermere H o r s e t h i e f Greek Group) and E a r l y Cambrian ( H a m i l l Group and above) age seen i n the Kootenay A r c t o the e a s t . He t h u s s u g g e s t s t h a t the core zone g n e i s s e s r e p r e s e n t r e g i o n a l l y metamorphosed and m i g m a t i z e d s e d i m e n t s o f the H o r s e t h i e f Creek Group. Reesor and Wanless have r e c e n t l y completed some z i r c o n work on some g n e i s s e s i n the core zone o f the Thor-O d i n g n e i s s dome (Re e s o r , 197^, p e r s o n a l c o m m u n i c a t i o n ) . A l t h o u g h t h e z i r c o n s are d i s c o r d a n t , a c h o r d drawn on a number o f f r a c t i o n s from a s i n g l e sample g i v e s an age o f 1900 m. y r . w i t h l o w e r i n t e r c e p t a t about 150 m. y r . T h i s r e s u l t , however, s t i l l l e a v e s u n c e r t a i n the age o f t h e core g n e i s s e s . The z i r c o n s c o u l d be d e t r i t a l i n o r i g i n and p r e s e n t i n metamorphosed Windermere o r P u r c e l l s t r a t a but o r i g i n a l l y d e r i v e d from P r e c a m b r i a n Hudsonia.n( ?) r o c k s o r t h e y c o u l d be d i r e c t l y p r e s e n t i n metamorphosed K u d s o n i a n ( ? ) basement. Cam p b e l l ' s (1973) i d e a s o f f e r the p o s s i b i l i t y t h a t the core g n e i s s e s r e p r e s e n t n e i t h e r metamorphosed Windermere 19 sediments ( R e e s o r ) n o r metamorphosed K u d s o n i a n basement ( R o s s ) , but r a t h e r metamorphosed P u r c e l l s t r a t a . H i s s t r u c t u r a l model f u r t h e r o f f e r s the p o s s i b i l i t y t h a t d i a p i r i s m o f t h e core g n e i s s e s was t h e i r p r i n c i p a l mechanism of d e f o r m a t i o n i n the c e n t e r o f the core zone o f the Columbian Orogen (as s u g g e s t e d by Reesor f o r the V a l h a l l a , T h o r -Odin and p o s s i b l y Frenchman's Cap domes); whereas, outward from the core zone, more b r i t t l e g n e i s s wedges (the C l a c h n a c u d a i n n , M a l t o n , and Quesnel Lake g n e i s s e s ) were t e c t o n i c a l l y emplaced as suggested by Ross. I n summary, the two major q u e s t i o n s t h a t must be answered t o r e s o l v e the o r i g i n o f the g n e i s s domes and g n e i s s wedges a r e J what i s t h e i r age and what were t h e i r dominant mechanisms o f d e f o r m a t i o n ? GEOLOGY OF THE REVELSTOKE-AL3ERT CANYON AREA D e t a i l e d g e o l o g i c a l and s t r u c t u r a l mapping o f the C l a c h n a c u d a i n n G n e i s s and i t s s u r r o u n d i n g metasediments has been c a r r i e d out by b o t h Ross(l968) and G i l m a n (1972). Ross mapped the n o r t h e r l y p a r t of the g n e i s s s h e e t and G i l m a n the s o u t h e r l y p a r t , Ross's (1968) g e o l o g i c a l map i s seen i n F i g u r e I I - 4 and G i l m a n * 3 (1972) i n F i g u r e I I - 5 . The a r e a o f o v e r l a p between the two maps i s i n d i c a t e d . The m ajor s t r u c t u r e i s a r e f o l d e d recumbent f o l d w i t h g n e i s s l y i n g i n i t s c o r e , Ross (1968, 1970) has i n t e r p r e t a t e d t h r e e e p i s o d e s o f d e f o r m a t i o n i n the a r e a . The f i r s t o r main r\3 o FIGURE L i t h o i o g i c map o f the R e v e l s t o k e - A l b e r t Canyon a r e a ( a f t e r Ross, 1968). Each f o l i a t i o n r e a d i n g r e p r e s e n t s an average o f 25 t o 30 measurements. See F i g u r e I I - 2 f o r the l o c a t i o n o f t h e map-area. 21 ~ y C l a c h n a c u d a i n n Schematic lection parallel !o the Tram - Canada Highway FIGURE I I - 5 i G e o l o g i c map o f the I l l e c i l l e w a e t V a l l e y n e a r A l b e r t Canyon ( a f t e r G i l m a n , 1972). See F i g u r e I I - 2 f o r the l o c a t i o n o f t h e map-area. 22 phase produced th e dominant s t r u c t u r e ; i . e . , a l a r g e n o r t h e r l y - t r e n d i n g recumbent f o l d c o r e d by g r a n i t o i d g n e i s s . Phase 2 f o l d i n g caused r e f o l d i n g o f the phase 1 s t r u c t u r e i n t o open f o l d s a l o n g s o u t h e a s t e r l y axes. Thus, the d i p of t h e west l i m b o f the g n e i s s i n the n o r t h w e s t o f the a r e a (see F i g u r e I I - 4 ) i s d o m i n a n t l y t o the e a s t , but as one comes s o u t h , t h i s d i p changes from e a s t t o west (see L a u r e t t a i n F i g u r e I I - 5 ) . T h i s i s because the s t r u c t u r e has a c u r v i l i n e a r h i n g e due t o the i n t e r f e r e n c e of phase 1 and phase 2 f o l d i n g and i s c u l m i n a t i n g and d e p r e s s i n g a l o n g s t r i k e t o form a s e r i e s o f b a s i n s and domes (Ross, 1974, p e r s o n a l communicat-i o n ) . At about L a u r e t t a t h e s t r u c t u r e i s a domal f e a t u r e , whereas i n the n o r t h w e s t o f the a r e a , the two arms of the g n e i s s are e a s t e r l y - v e r g i n g and form a b a s i n s t r u c t u r e . E r o s i o n t h r o u g h the o v e r l y i n g g n e i s s has exposed the 'lower l e v e l ' m e t a s e d i m e n t a r y r o c k s i n the core o f the L a u r e t t a dome. T h i s i s b e s t u n d e r s t o o d by comparing c r o s s - s e c t i o n G-C (see F i g u r e I I - 5 ) a c r o s s the domal f e a t u r e t o c r o s s -s e c t i o n A-A' (see F i g u r e s I I - 2 , I I - 6 ) a c r o s s the b a s i n f e a t u r e . The s w i t c h i n d i p o f the g n e i s s from e a s t t o west i s t y p i c a l o f s t r u c t u r e s i n the Kootenay Arc which change t h e i r d i p from e a s t t o west i n a r e g u l a r f a s h i o n as one goes s o u t h a l o n g s t r i k e (Ross, 1970; Ross, 1974, p e r s o n a l c o m m u n i c a t i o n ) . Phase 3 f o l d i n g was a l o n g s o u t h e a s t e r l y s t r i k i n g a x i a l p l a n e s t h a t d i p p e d s t e e p l y t o the n o r t h e a s t 23 A' I i I I Ventego S y l i . I 4-i l l e c i l l e w a e t Syn. D e v i l l e Syn. NE FIGURE I I - 6 t S c h e m a t i c c r o s s - s e c t i o n A-A' a c r o s s t h e R e v e l s t o k e segment o f the K o o t e n a y A r c ( a f t e r Ross,1970). I t s * l o c a t i o n i s shown i n F i g u r e I I - 2 . The c o l o u r code i s t h e same as i n p r e v i o u s d i a g r a m s , B B' FIGURE I I - 7 t I d e a l i z e d b l o c k d i a g r a m a l o n g t h e l i n e B-B' i n d i c a t e d i n F i g u r e I I - 6 ( a f t e r R o s s , 1968). The g n e i s s l i e s i n t h e c o r e o f a f o l d h a v i n g an e a s t e r l y c l o s u r e and n o r t h e r l y a x i a l t r e n d . A c c o r d i n g t o Ross t h i s f o l d i s an e a s t e r l y c l o s i n g a n t i c l i n e . G n e i s s i n t h e c o r e c u t s a c r o s s the s t r a t a and i n t e r s e c t s t h e H a m i l l Group towards th e h i n g e l i n e . 24 ! and t h u s caused t i g h t e n i n g - u p o f t h e p r e v i o u s l y formed f o l d s . Three main t y p e s o f i n t r u s i v e r o c k s c u t the grano-d i o r i t e g n e i s s and the metasediments. L e u c o g r a n i t e and r e l a t e d p e g m a t i t e o c c u r as d i k e s , s i l l s and i r r e g u l a r masses. Two samples o f t h i s (G4, G6-2) were t a k e n from o u t c r o p s a l o n g the Trans-Canada Highway. D i o r i t e i s seen by G i l m a n (1972) i n the 'upper l e v e l ' metasediments on the n o r t h s i d e o f the Trans-Canada Highway (see F i g u r e I I - 5 ) . Ross has mapped a q u a r t z d i o r i t e - g r a n o d i o r i t e s y n - k i n e m a t i c i n t r u s i v e a l o n g the w e s t e r n m a r g i n o f h i s map-area (see F i g u r e .11-4). He f e e l s t h a t t h i s d i o r i t e i s p o s t - p h a s e 2 but pre-phase 3- Two samples o f q u a r t z d i o r i t e ( B l 4 , B15) were c o l l e c t e d a l o n g the B i g Bend Highway. A s m a l l body o f q u a r t z monzonite i s seen i n the c e n t e r o f the map-area and i s c o n s i d e r e d p o s t - t e c t o n i c . The ages o f the m e t a s e d i m e n t a r y r o c k s composing the upper and l o w e r l i m b s o f the major f o l d s t r u c t u r e are i m p o r t a n t i n d e t e r m i n i n g the p r o p e r sequence o f e v e n t s i n the a r e a . Ross (1968) o r i g i n a l l y mapped some H o r s e t h i e f Creek Group ( l a t e Precambrian-Windermere) metasediments as w e l l as Hamill. Group ( L a t e Cambrian) metasediments i n b o t h the upper and l o w e r l i m b s o f the s t r u c t u r e . More r e c e n t l y (Ross,. 1974, p e r s o n a l c o m m u n i c a t i o n ) , he has c o n c l u d e d t h a t most i f not a l l o f the metasediments s u r r o u n d i n g the g n e i s s b e l o n g t o the H a m i l l Group. (Thus the metasediments s u r r o u n d i n g t h e g n e i s s have a l l been c o l o u r e d the same i n 1 25 F i g u r e I I - 4 ) . G i l m a n (1972) has a l s o c o n c l u d e d t h a t the 'upper l e v e l 1 metasediments b e l o n g t o the H a m i l l Group, However, he f e e l s t h a t , because o f t h e i r c o n t r a s t i n g l i t h o l o g i c c h a r a c t e r , the 'lower l e v e l ' metasediments are d i f f e r e n t and c o u l d p o s s i b l y be p a r t o f the H o r s e t h i e f Creek Group. He s u g g e s t s t h a t t h e y may be u n d e r l a i n by a d d i t i o n a l g n e i s s as i n the case o f the V a l h a l l a Dome ( R e s s o r , 19&5). G i l m a n t h u s l e a v e s room f o r an a l t e r n a t e s t r u c t u r a l i n t e r p r e t a t i o n d i f f e r e n t from the p r e v i o u s l y p r e s e n t e d views o f Ross. He p o i n t s out t h a t t h e r e i s no d e f i n i t e e v i d e n c e as y e t as t o the c o r r e l a t i o n o f the 'lower l e v e l * metasediment-a r y r o c k s , and t h a t u n c e r t a i n t i e s s t i l l e x i s t c o n c e r n i n g d e t a i l e d s t r a t i g r a p h i c c o r r e l a t i o n s o f the 'upper l e v e l ' m e t a s e d i m e n t a r y r o c k s . Ross (1968) has i n t e r p r e t e d the g n e i s s as a s l i c e o f basement t h a t was t e c t o n i c a l l y emplaced as the core of an e a s t e r l y c l o s i n g nappe. On the b a s i s o f the r e l a t i o n s h i p between the g n e i s s and a s s o c i a t e d a m p h i b o l i t i c i n t r u s i o n s , Ross (1968) s u g g e s t e d t h a t the g n e i s s had a metamorphic h i s t o r y p r i o r t o phase 1 d e f o r m a t i o n and p r i o r t o the emplacement o f the a m p h i b o l i t e s as b a s i c d i k e s . I n a d d i t i o n , i n d i c a t i o n s o f a 1500-1700 m. y r . basement beneath the Kootenay A r c ( S i n c l a i r , 19&6) l e a d Ross t o s u g g e s t t h a t the g n e i s s c o u l d be basement o f Hudsonian age upon which m e t a s e d i m e n t a r y r o c k s now f o u n d i n the Shuswap Complex were 26 o r i g i n a l l y d e p o s i t e d . G i l m a n ( 1972) makes no c o n c l u s i o n s as t o the g n e i s s ' s g e n e s i s based on a v a i l a b l e g e o l o g i c and s t r u c t u r a l i n f o r m a t i o n o t h e r t h a n t o s a y t h a t i t was emplaced e i t h e r p r i o r t o o r contemporaneous w i t h the r e g i o n a l Shuswap metamorphism. The c o n t a c t s o f the g n e i s s are a p p r o x i m a t e l y c o n c o r d a n t w i t h t h e metasedimentary l a y e r i n g but are s h a r p . Gilman f e e l s t h i s f a c t p l u s the g e n e r a l homogeneity o f t h e g n e i s s argue a g a i n s t i t s g e n e r a t i o n i n s i t u d u r i n g metamorphism. However, he f e e l s t h a t c o n c l u s i v e r a d i o m e t r i c age d e t e r m i n a t i o n s are needed t o s u p p o r t Ross's i n t e r p r e t a t i o n , DETAILED DESCRIPTION OF THE CLACHNACUDAINN GNEISS Because o f the g e n e r a l homogeneous c h a r a c t e r o f t h e g n e i s s , i t was d e c i d e d t o d e s c r i b e i t as a s i n g l e e n t i t y , s u m m a r i z i n g the o b s e r v a t i o n s o f t h e w r i t e r , Ross ( 1 9 6 8 ) , and G i l m a n ( 1 9 7 2 ) , r a t h e r t h a n p r o v i d e i n d i v i d u a l m e s o s c o p i c and m i c r o s c o p i c d e s c r i p t i o n s o f the samples t h a t were d a t e d . The g n e i s s i s a m a s s i v e , g r a y t o w h i t e , medium t o c o a r s e g r a i n e d r o c k w i t h a w e l l d e v e l o p e d metamorphic f o l i a t i o n . The m i n e r a l assemblage i n c l u d e s v a r i o u s c o m b i n a t i o n s o f q u a r t z ( 1 0 - 5 0 ^ ) , p l a g i o c l a s e (An-^-Zj-o) ( 2 5-70$), K - f e l d s p a r ( 0 - 1 5 $ ) , p e r t h i t e , b i o t i t e ( 5 - 1 5 $ ) , h o r n e b l e n d e ( 0 - 1 0 $ ) and m u s c o v i t e ( 0 - 5 $ ) w i t h m i n o r q u a n t i t i e s o f sphene, z i r c o n , a p a t i t e , e p i d o t e and c a l c i t e . The v a r y i n g p r o p o r t i o n s o f f e l s i c m i n e r a l s were e s t i m a t e d by 27 s l a b - s t a i n i n g samples. T a b l e I I - 2 g i v e s the c h e m i c a l c o m p o s i t i o n o f a r e p r e s e n t a t i v e sample of the g n e i s s . SiC-2 68.77 68.13 T i 0 2 .32 .31 A 1 2 0 3 15.3^ 15.07 CaO 3.87 3.83 K 2 0 1.61 1.58 MgO .84 .88 Fe t o t a l as Fe20-^ 2.65 2.62 T o t a l s t - 93.^0 92.42 TABL5 II-2> D u p l i c a t e whole r o c k a n a l y s e s i n w e i g h t fo o x i d e s o f sample Rl-T-2. Rl-T-2 i s a sample of the C l a c h n a c u d a i n n G n e i s s c o l l e c t e d by B l e n k i n s o p (1972). I n some exposures the g n e i s s i s u n i f o r m and homogeneous, but more o f t e n i t has a pronounced banded appearance caused by b o t h v a r i a t i o n s i n g r a i n s i z e s and v a r i a t i o n s i n the p r o p o r t i o n s o f f e l s i c t o m a f i c m i n e r a l s . The m a f i c m i n e r a l s are p r e s e n t i n d i s c o n t i n u o u s l a y e r s , l e n s e s and s t r e a k s and g i v e the r o c k i t s p r i m a r y f o l i a t i o n . A weaker second f o l i a t i o n , making a h i g h a n g l e w i t h the main one, i s a l s o p r e s e n t . I n p l a c e s , the g n e i s s has a w e l l d e v e l o p e d p e n e t r a t i v e l i n e a t i o n t h a t i s o u t l i n e d by e l o n g a t e g r a i n s o f q u a r t z and f e l d s p a r . The g n e i s s i c l a y e r i n g i s 28 g e n e r a l l y c o n s t a n t o v e r l a r g e e x p o s u r e s but l o c a l l y i t i s d i s t o r t e d i n t o s m a l l f o l d s o u t l i n e d by a s w i r l e d p r i m a r y f o l i a t i o n . Such zones o f s w i r l e d g n e i s s s u g g e s t t h a t p o r t i o n s o f the g n e i s s have undergone d u c t i l e f l o w . One a r e a o f s w i r l e d g n e i s s i s marked on Ross's (1968) g e o l o g i c map seen i n F i g u r e F i g u r e s I I - 8 t o 11-12 show t y p i c a l examples o f the g n e i s s and i l l u s t r a t e i t s g e n e r a l c h a r a c t e r and some o f i t s v a r i a t i o n s t h e r e o f . W i t h i n t h e g n e i s s are s e v e r a l b o d i e s o f a m p h i b o l i t e v a r y i n g i n t h i c k n e s s from a few i n c h e s t o about t e n f e e t . Ross (1968) has i n t e r p r e t a t e d t h e s e as metamorphosed igneous i n t r u s i o n s ( v o l c a n i c d i k e s ) which were emplaced w i t h i n the g n e i s s p r i o r t o phase 1 f o l d i n g . S m a l l f i n e - g r a i n e d v e i n s and l e n s e s o f l e u c o g r a n i t e c u t the g n e i s s and the a m p h i b o l i t e s . Of p a r t i c u l a r i n t e r e s t was the degree o f a l t e r a t i o n p e t r o g r a p h i c a l l y r e v e a l e d i n the v a r i o u s r o c k samples. There i s good e v i d e n c e o f retrogra.de a l t e r a t i o n o f hornblende (and p o s s i b l y b i o t i t e ) t o e p i d o t e and b i o t i t e t o c h l o r i t e . E p i d o t e i s seen f o r m i n g r e a c t i o n r u n s around some hor n b l e n d e (and p o s s i b l y b i o t i t e ) g r a i n s and c h l o r i t e i s f o u n d i n c o n j u n c t i o n v/ith and i n t e r s t i t i a l t o (between the c l e a v a g e p l a n e s ) b i o t i t e f l a k e s . Some p l a g i o c l a s e g r a i n s have a d u s t y , s p e c k l e d t e x t u r e i n d i c a t i v e o f s a u s s e r i z a t i o n and s e r i c i t i z a t i o n . C a l c i t e g e n e r a l l y o c c u r s as s m a l l i n c l u s i o n s 29 FIGURE .11-9,« Exposure o f s w i r l e d , g r a n o d i o r i t e g n e i s s a t sample l o c a t i o n B 6 - 3 . 30 FIGURE 11-11i Hand specimen sample 36-1. T h i s sample c o n t a i n s a t l e a s t 10$ h o r n b l e n d e . The s c a l e i s 1 cm. 31 FIGURE 11-12t Hand specimen sample o f R3-T. T h i s i s one o f B l e n k i n s o p ' s (1972) L a Forme Creek samples and i s s i m i l a r t o some o f t h e w r i t e r ' s samples (B8 t o B12). The s c a l e i s 1 cm. FIGURE II-13« C a l c i t e a l t e r a t i o n i n sample R3-T ( x - n i c o l s , 3x l e n s e ) . The s c a l e i s a p p r o x i m a t e l y 1 i n c h = .54 mm. 32 i n f e l d s p a r g r a i n s o r a l o n g g r a i n b o u n d a r i e s . I n g e n e r a l , i t i s t h e L a Forme Creek samples (338 t o B12) which show the most s i g n i f i c a n t a l t e r a t i o n and t h u s the l a r g e s t q u a n t i t i e s o f c h l o r i t e , e p i d o t e and c a l c i t e . Amounts of each o f t h e s e t h r e e m i n e r a l s range up t o 5 $ . Trans-Canada Highway samples c o n t a i n from t r a c e amounts up t o about 2% o f each. M u s c o v i t e i s f o u n d almost e x c l u s i v e l y i n the L a Forme Creek samples. M y r m e k i t e , an i n t e r g r o w t h o f p l a g i o c l a s e and q u a r t z w h i c h g e n e r a l l y r e p l a c e s p o t a s s i u m f e l d s p a r , i s seen i n minor q u a n t i t i e s ( l e s s t h a n 2fo) i n some Trans-Canada Highway samples. I t i s b e l i e v e d t o have formed d u r i n g m y l o n i t i z a t i o n o f t h e r o c k by r e c r y s t a l l i z a t i o n o f f i n e g r a i n s o f f e l d s p a r and q u a r t z . Examples o f a l t e r a t i o n are seen i n F i g u r e s 11-13 t o 1 1 - 1 5 . E v i d e n c e o f d e f o r m a t i o n i n c l u d e s k i n k e d and d i s t o r t e d m i c a g r a i n s , r a gged g r a i n b o u n d a r i e s , p r e s s u r e shadows of q u a r t z and f e l d s p a r g r a i n s , and s h r e d d e d and g r a n u l a t e d m i n e r a l s t h a t are s t r e a k e d out i n a pronounced g n e i s s i c b a n d i n g . I n summary, t h e r e i s c o n s i d e r a b l e e v i d e n c e t o s u g g e s t t h a t t h e g n e i s s has not remained a c l o s e d system t o i s o t o p i c m i g r a t i o n on a m i c r o s c o p i c s c a l e . The q u e s t i o n a r i s e s as t o the e f f e c t o f any i s o t o p i c exchange on the r e l i a b i l i t y o f the t o t a l r o c k t o r e m a i n a c l o s e d system. I t i s perhaps i n d i c a t e d t h a t l a r g e whole r o c k samples s h o u l d be used. 33 FIGURE I I - l 4 t E p i d o t e r e a c t i o n r i m around a b i o t i t e o r amphibole g r a i n i n sample B3 ( p l a n e p o l a r i z e d l i g h t , l O x l e n s e ) . The s c a l e i s app r o x -i m a t e l y 1 i n c h m ,16 mm. FIGURE I I - l 5 i M y r m e k i t i c t e x t u r e seen i n sample B6-3 ( x - n i c o l s , l O x l e n s e ) . The s c a l e i s a p p r o x -i m a t e l y 1 i n c h = ,16 mm. 34 CHAPTER III K-AR GEOCHRONOLOGY Seven samples were dated by the K-Ar method.i four of the Clachnacudainn Gneiss, one from a leucogranite dike intruding the gneiss, and two of the syn-kinematic quartz d i o r i t e - g r a n o d i o r i t e i n t r u s i v e seen along the western margir of Ross's ( 1968) map-area (see Figure II-4). The basic theory of K-Ar geochronology i s given i n Appendix B and a n a l y t i c a l d e t a i l s and data are given i n Appendices G and H. The r e s u l t s are l i s t e d i n Table I I I - l , Sample dated Apparent Age (m. yr.) Clachnacudainn Gneiss samplest B2-1, b i o t i t e 5 3 . 7 + 3 . 2 B 6 - 3 , b i o t i t e 5 4 . 0 + 3 . 2 B 6 - 3 A , b i o t i t e 5 7 . 9 + 3 . 7 B12, b i o t i t e 5 5 . 6 + 3 . 3 Leucogranite intr u s i v e 1 -G 6 - 2, b i o t i t e 52.1 + 3.1 Quartz d i o r i t e i n t r u s i v e t B14, b i o t i t e 5 0 . 9 + 3 . 4 B15, hornblende 145 .5 + 11.8 TABLE I I I - l ; K-Ar r e s u l t s . A n a l y t i c a l data i s given i n Appendix H, Tables H - l l and H-12. Uncertainties quoted are 95$ confidence l i m i t s . 35 Two K-Ar ages have previously been reported from rocks within the Clachnacudainn S a l i e n t . These are a b i o t i t e age of 57 m. yr. f o r the syn-kinematic i n t r u s i v e mentioned above (Baadsgaard et a l . , 1961) and a b i o t i t e age of 110 m. yr. f o r the post-kinematic monzonite intr u s i v e present just north (see Figure II-4) of the Clachnacudainn Snowfield (Wheeler, 1965). The 57 m.. yr. age and the f i r s t s i x ages seen i n Table I I I - l a l l r e f l e c t the same T e r t i a r y event. K-Ar data from within the Shuswap Terrane (Gabrielse and Reesor, 1964; Wanless, 1969; Medford, 1974; Ross, 1974, and others) substantiates an Early T e r t i a r y thermal event (40-65 m. yr.) i n southeastern B r i t i s h Columbia accompanied by i n t r u s i o n and extrusion. Rock and mineral K-Ar ages within the Shuswap Complex have been d i f f e r e n t i a l l y (variably) reset by t h i s event and thus a smearing of K-Ar age dates i s seen. The r e s u l t s i n Table I I I - l indicate that the K-Ar ages of the b i o t i t e samples analyzed have been completely reset. Thus the 110 m. yr. b i o t i t e age reported by Wheeler (1965) appears to be an exception i n t h i s area. It i s interpreted as a minimum age f o r the monzonite i n t r u s i v e . D i f f e r e n t i a l r e s e t t i n g ( i . e . , p a r t i a l argon loss) i s the easiest explanation of the discordant b i o t i t e and hornblende ages of the quartz d i o r i t e - g r a n o d i o r i t e i n t r u s i v e , as hornblende i s more r e s i s t a n t to a post-formation thermal event than b i o t i t e . It i s concluded that the emplacement age of t h i s 36 i n t r u s i v e i s very l i k e l y e a r l i e r than 146 m. yr. ago. Ross's (1968, 1970) hypothesis i s that i t i s probably Late T r i a s s i c (180-210 m. yr.) i n age; i . e . , post-phase 2 deformation and pre-phase 3 deformation. The data f o r the four samples of the Clachnacudainn Gneiss are plotted on an isochron diagram i n Figure I I I - l (see Appendix B f o r theory). It i s concluded that the gneiss cooled below the argon retention temperature of b i o t i t e 55 m> \Yr> a g ° - This compares with b i o t i t e and hornblende K-Ar cooling ages of 60 to 70 m. yr. f o r the core zone of the Thor-Odin gneiss dome (Reesor, 1970). o o " o i 1 1 1 1 r 1 1 1 0.0 100.0 200.0 300.0 400.0 500.0 600.0 700.0 800.0 K40(sample)/Ar36(atmos.) (>rl0 3 ) FIGURE K-Ar i s o c h r o n p l o t f o r C l a c h n a c u d a i n n G n e i s s b i o t i t e samples. W e i g h t i n g the f o u r d a t a p o i n t s e q u a l l y and c o n s t r a i n i n g t he i s o c h r o n t o pass t h r o u g h the a t m o s p h e r i c p o i n t (as t h e o r y d i c t a t e s ) g i v e s an age o f 55.5 + 1.8 m. y r . ( Y o r k , I966 95% c o n f i d e n c e l i m i t s ) . A s t r a i g h t average o f t h e f o u r i n d i v i d u a l K-Ar ages would g i v e 55.3 i 1.9 m. y r . 38 CHAPTER IV RB-SR GEOCHRONOLOGY INTRODUCTION Due to the f a i l u r e of the K-Ar method to 'penetrate' the Early T e r t i a r y thermal event seen i n the rocks of the Shuswap Metamorphic Complex, i t was suggested (Gabrielse and Reesor, 1964; Wheeler, 1970) that zircon and/or whole rock Rb-Sr i s o t o p i c age determinations, be attempted. It was hoped that 'absolute' ages of older orogenic and metamorphic events might be preserved and seen by either of these methods. Subsequently, Blenkinsop (1972) carried out a whole rock Rb-Sr study on samples from the Malton Gneiss, the Quesnel Lake Gneiss and the Clachnacudainn Gneiss. He obtained an age of 680 ! 80 m. yr. from a whole rock isochron f o r seven out of eight samples from the Malton Gneiss, and an age of 740 * 150 m. yr. from a whole rock isochron f o r eight out of eleven samples from the Quesnel Lake Gneiss. He also obtained two whole rock isochrons of 7^0 t 30 m. yr. and 240 + 30 m. yr. f o r th i r t e e n out of f i f t e e n samples from the Clachnacudainn Gneiss. Scatter of data about the isochrons exceeds experimental error f o r a l l three gneiss bodies; thus, the calculated ages and uncertainties must be viewed with caution. The writer's main objective i n undertaking the present 39 study was to provide further insight into the i n t e r p r e t a t i o n of R b-Sr data from the Clachnacudainn Gneiss. Eighteen new whole rock samples, lar g e r than those obtained by Blenkinsop ( 1 9 7 2 ) , were c o l l e c t e d . Rb-Sr whole rock analyses were performed on f i f t e e n of these. In addition, analyses were car r i e d out on b i o t i t e and potassium feldspar mineral separates from s i x of the samples. Detailed a n a l y t i c a l data i s contained i n Appendix H. The r e s u l t s are summarized i n Graphs A and B contained i n the pocket at the back of t h i s t h e s i s . * The basic theory of Rb-Sr geochronology and the basic ground rules whereby one can interpret Rb-Sr data are outlined i n Appendix B. Appendix C describes the instrument-ation and operation of one of the two s o l i d source mass spectrometers at U.B.C. used f o r strontium is o t o p i c analyses. Rubidium and strontium concentrations were determined by the x-ray fluorescence (XRF) method. Details about sample preparation and about various a n a l y t i c a l procedures and techniques used during the course of XRF work and mass spectrometric work are given i n Ryan (1973) and Blenkinsop ( 1 9 7 2 ) . Additional information f o r the XRF and Rb-Sr methods i s contained i n Appendices D and E res p e c t i v e l y . The data reduction techniques used f o r mass spectrometric data are described i n Blenkinsop ( 1 9 7 2 ) . An Interdata minicomputer * I t i s intended that these be opened up and looked at as t h i s chapter i s read. 40 controls the on-line collection and reduction of data. The version of the strontium computer program which was used by the writer is contained in Appendix F. Appendix I describes some of the statistical techniques used in treating the data. PREVIOUS RESULTS The locations of samples collected by Blenkinsop (1972) are shown in Figure IV-1. XRF data used to calculate Rb/Sr weight ratios is shown in Table IV-1. The precision of the XRF analyses is estimated to be 3$ at the 95$ confidence level (Ryan, 1973; also see Appendix D). Rubidium and strontium isotopic data is seen in Table IV-2 and on a BPI plot in Figure IV-2. One immediately notes that there is a rather limited variation in the Rb/Sr and Sr87/Sr86 ratios exhibited by the suite. It therefore follows that precise measurements of Sr87/Sr86 ratios are required in order to apply the Rb-Sr method. Blenkinsop (1972) estimates the precision of his strontium analyses to be 0.02$ at the 95$ confidence level. He obtained two isochrons from his data (see Figure IV-2), one with an age of 740 + 30 m. yr. (York, 1969 uncertainty2) and the other with an age of 240 + 30 m. yr. (York, 1966 uncertainty2). Blenkinsop (1972) tentatively interpretated these results as representing the time of the Kootenay Orogeny and time of the regional 2A11 Rb-Sr age uncertainties mentioned in this thesis are 95$ confidence limits and are calculated by either the method of York, 1966 (Yl) or York, 1969 (Y2). Appendix I discusses when and how either uncertainty is used. FIGURE I V - 1 t L o c a t i o n s of samples of the Clachnacudainn Gneiss c o l l e c t e d by Blenkinsop (1972). 42 Sample Sample Location Rb(ppm) Sr(ppm) Weight Ratio Rb/Sr Average Rb/Sr Rl-T-l.WR TC 101. 201. 0.502 0.505 101. 199. 0.508 R1-T-2.WR TC 64.2 277. 0.232 0.232 Rl-l.WR TC 55.5 342. 0.162 0.162 R1-2.WR TC 113. 225. 0.502 0.502 R1-4.WR TC 76.1 266. 0.286 0.283 76.5 271. 0.282 75.6 272. 0.278 75.7 266. 0.285 R1-5.WR TC 86.7 205. 0.423 0.423 R2-1,WR TC 79.7 427. 0.187 0.186 '. 79.9 432. 0.185 R3-1.WR TC 85.0 228. 0.373 0.373 •-85.6 229. 0.374 R4-T.WR TC 92.3 217. 0.425 0.425 R5-T.WR LA 86.5 217. 0.399 0.399 R5-1»WR LA 85.9 195. 0.441 0.441 R5-2.WR LA 86.5 210. 0.412 0.414 87.4 210. 0.416 87.2 211. 0.413 R6-1,WR LA 84.9 211. 0.402 0.402 R6-2.WR LA 104. 183. 0.568 O.568 TABLE IV-11 XRF Rb and Sr concentration results for Blenkinsop (1972) samples of the Clachnacudainn Gneiss. WR = whole rock sample TC = Trans-Canada Highway sample La = La Forme Creek sample 43 Sample Sample Location Sr8?/Sr86 Uncertainty* (.02%) Rb87/3r86 Uncertainty* (3*> Rl-T-l.WR TG 0.7148 i 1.46 0.044 0.7149 Rl-T-2,WR TC 0.7120 O.67I 0.020 Rl-l.WR TG 0.7095 0.470 0.014 R1-2.WR TC 0.7147 1.45 0.044 R1-4.WR TC 0.7137 0.818 0.025 Rl-5fWR TC 0.7139 1.23 0.037 R2-1.WR TC 0.7101 0.00014 0.537 0.016 0.7099 R3-T,WR TC 0.7130 0.926 0.028 R3-1,WR TC 0.7131 1.08 0.032 R4-T,WR TC 0.7139 I.23 0.037 R5-T.WR LA 0.7168 1.15 0.034 R5-1,WR@ LA 0.7175 1.28 0.038 R5-2.WR LA 0.7170 1.20 O.036 R6-1,WR LA 0.7173 1.17 0.035 R6-2,V/R@ LA 0.7176 1.65 0.049 0.7178 > * 9 5 % confidence limits @ not used for isochron calculation TABLE IV-21 Rb and Sr isotopic ratios for Blenkinsop (1972) Clachnacudainn Gneiss whole rock samples. These results are plotted in Figure IV-2 and Graph A. .70951.0009(Yl) _ m I — Or- ' O ft cr " r UJ <D CC cn \ 00= air. in .7044+.0007(Yl) FIGURE iv - 2 i D R T f l FOR BLENKINSOP WHOLE ROCK SRMPLES 740 + 30(Y2) m. yr. 240 + 30(Y1) m. yr. •p-point not used for isochron calculation 1 1 1 1 1 0.0 0.2 0.4 0.6 0.B 1.0 1.2 R887/SR66 ATOMIC RATIO 1.4 1.8 i.e 2.0 —I 2.2 FIGURE IV - 2 i BPI plot f o r Blenkinsop whole rock samples ( a f t e r Blenkinsop, 1972) . For i d e n t i f i c a t i o n of the data points, see Graph A. Uncertainties are 95$ confidence l i m i t s calculated a f t e r York, 1966 (Yl) or York, 1969 (Y2). ^5 Shuswap metamorphism res p e c t i v e l y . As a means of q u a l i t y c o n t r o l l i n g his own data, the writer reanalyzed some of Blenkinsop*s samples. XRF analyses of Rl-T-1, R-5-T, and R5-2 are compared with Blenkinsop's (1972) r e s u l t s i n Appendix H, Table H-9. There i s excellent agreement, well within the stated p r e c i s i o n of the method. Strontium i s o t o p i c analyses of Rl-T-1 and R5-2 are compared with Blenkinsop's (1972) r e s u l t s i n Appendix H, Table H-6. Agreement i s within experimental error. The writer recalculated Blenkinsop's (1972) isochrons including the above data and including sample R5-1 i n the older isochron c a l c u l a t i o n (see Figure IV-3). The two ages obtained were 721 + 61(Yl) m. yr. and 238 + 44(Y1) m. yr. NEW RESULTS The r e s u l t s of f i f t e e n new Rb-Sr whole rock analyses are summarized i n Table IV-3 and pl o t t e d i n Figure IV-4. D e t a i l s of i n d i v i d u a l mass spectrometric runs are contained i n Appendix H, Tables H-l and H-2. The average p r e c i s i o n of whole rock analyses was 0.03% at the 95% confidence l e v e l . Duplicate analyses of several samples and r e p l i c a t e analyses of a strontium reference standard, SRM 987, are seen i n Tables H-6 and H-7 respectively. XRF data i s presented i n Table H-8. Looking at the data i n Figure IV-4, one i s i n i t i a l l y struck by how d i s s i m i l a r the exhibited pattern i s compared .7096J .0008(Y1) .70^51.0007(Y1) — in O f ' • X o ~2 to FIGURE I V - 3 I DflTfl FOR BLENKINSOP WHOLE ROCK SAMPLES 721 + 61(Yl) m. yr. 238 + 4 M Y 1 ) m. yr. * point not used f o r isochron c a l c u l a t i o n 1 1 1 1 1 i 1— 0 0 0.2 0.4 0.B 0.8 1.0 1.2 1.4 RB87/SR86 ATOMIC RATIO 1.6 —\ 1.6 2.0 2.2 FIGURE IV- 3 t BPI plot f o r Blenkinsop whole rock samples showing re c a l c u l a t e d isochrons using additional data from t h i s study. For i d e n t i f i c a t i o n of the data points, see Graph A. Uncertainties are 95$ confidence l i m i t s . ^7 Sample Sample Location Sr87/3r86 Uncertainty Rb87/Sr86 Uncertainty (3%) B2-1.WR TC 0 .71453 0.00014 1.128 0 .034 B3.WR TC 0 .71203 0.00028 0 .697 0.021 B6-1.WR TC 0.70862 0.00014 0 .415 0.012 B6-2.WR TC 0.7H82 0.00014 0 .857 0 .026 B6-3.WR TC 0.71^35 0 . 0 0 0 5 8 1.288 0 .039 B6-3A.WR TC 0 .71517 0.00014 1.476 0.044 37-1tWR TC 0.71332 0 . 0 0 0 3 4 0 .769 0 .023 B7-2.WR TC 0.71307 0.00014 0.642 0.019 B7-3.WR TC 0.71346 0.00022 0.864 0.026 B8, WR LA 0.71698@ 0.00014® 1 .405 0.042 B9.WR LA 0.71472 0.00014 0 .955 0 .029 BI0,WR LA 0.71489 0 . 0 0 0 2 6 0.941 0.028 B11,WR LA 0.71608 0 . 0 0 0 3 0 1.128 0.034 B12.WR LA 0.71992 0.00031 2 .302 O.O69 BI3,WR LA O.7IO66 0.00020 O.298 0 .009 B5-1,WR TC 0.73108 0 . 0 0 0 2 6 2.121 0.064 * 95% confidence limits. Individual uncertainties were used for Sr87/Sr86 ratios. @ weighted average of two isotopic analyses * * sample of 'lower level' metasediments (see Figure 1-2) TABLE IV-3i Rb and Sr isotopic ratios for Clachnacudainn Gneiss whole rock samples collected for this study. These results are plotted in Figure IV-4 and Graph A. One sample of the 'lower level' metasediment was analyzed and the result plotted in Graph B. O r . -£8 .70741.0016(Y1) FIGUREiv-4» DRTfl FOR BIRNIE WHOLE ROCK SAMPLES 57^ m. yr. 00 0.0 I— 0.2 — 1 — 0.4 0.8 RB87/SR86'ATOMIC RATIO 1.4 l'.B l.B ~I— 2.0 —T— 2.2 —I 2.4 FIGURE IV-4: BPI plot f o r whole rock samples c o l l e c t e d f o r t h i s study. A straight line f i t t e d to the data and two l i n e s representing 95% confidence limits (Yl) are plotted. For i d e n t i f i c a t i o n of the data points, see Graph A. 49 to Blenkinsop's (1972) r e s u l t s . A str a i g h t l i n e f i t t e d to the points gives an age of 451 + 123(Y1) m. yr. Reference isochrons f o r 451 m. yr. and f o r the 95$ confidence l i m i t s are plotted. One i n t e r e s t i n g observation consistent with Blenkinsop's r e s u l t s i s that samples of the gneiss c o l l e c t e d along La Forme Creek plot higher on the diagram; i . e . , given a c e r t a i n Rb/Sr r a t i o , La Forme Creek samples have higher Sr87/Sr86 r a t i o s (see Graph A). Mineral isochrons were determined f o r six sets of b i o t i t e , potassium feldspar, and whole rock samples. Details of analyses are presented i n Appendix H. The r e s u l t s are summarized i n Table IV -4 and plot t e d i n Graph B. B i o t i t e strontium concentrations and Sr87/Sr86 r a t i o s were determined by the isotope d i l u t i o n method. The average precisions of b i o t i t e analyses and potassium feldspar analyses were 0.043$ and 0.068$ resp e c t i v e l y at the 95$ confidence l e v e l . An enlargement of the lower l e f t hand portion of Graph B i s seen i n Figure IV-5. Age uncertainties f o r two isochrons were calculated a f t e r York, i 9 6 0 (Yl) and f o r the rest a f t e r York, 1969 ( Y 2 ) . INTERPRETATION AND SIGNIFICANCE OF RESULTS The s i x Rb^-Sr mineral isochron ages are i n excellent agreement with the K-Ar re s u l t s presented i n Chapter I I I . A comparison of ages obtained by the two methods i s seen i n Table IV - 5 . The re s u l t s indicate that the 55 m, yr. old 50 Sample Sample Location Sr87/3r86 Uncertainty Rb87/Sr86* •a Uncertainty (3$) B2-1.WR TC 0.71 5^3 0.00014 1.128 0.034 B2-1.KF 0 .71579 @ 0.00014@ 2 . 5 3 6 O . 0 7 6 B2-1.BT 0 . 7 6 9 4 0 0.00022 6 9 . 5 0 2.09 B6-3.WR TC 0 . 7 1 4 3 5 0.00058 1.288 0.039 B6-3,KF 0 . 7 1 5 9 8 0.00032 2.380 0.071 B6-3.BT 0 . 8 4 0 6 9 0.00034 156.1 4.7 B6-3A,WR TC 0.71517 0.00014 1.476 0.044 B6-3A.KF 0 . 7 1 7 4 2 0.00044 2.601 0.078 B6-3A,BT O . 9 0 7 2 8 0.00054 2 3 8 .O 7.1 B7-2.WR TC 0.71307 0.00014 0.642 0.019 B7-2.KF 0 . 7 1 3 4 4 0.00028 1.375 0.041 B7-2,BT 0.74848 0.00022 4 3 . 8 0 1.31 B8,WR LA 0 . 7 1 6 9 8 @ 0 . 0 0 0 l 4 @ 1.405 0.042 B8,KF 0.71822 0.00024 1.907 0.057 B8.BT 0.74578 0.00038 3 9 . 7 9 1.19 B12.WR LA 0.71992 0.00031 2. 302 O .O69 B12.KF 0.72154 0.00042 3 .700 0.111 B12.BT O . 7 8 8 6 7 O.OOOoO 8 6 . 7 0 2.60 * 95$ confidence limits. Individual uncertainties were used for Sr87/Sr86 ratios. 0 Biotite Rb87/Sr86 ratios were calculated using XRF Rb concentrations and mass spectrometric Sr concentrations. @ weighted average of two isotopic analyses TABLE IV-4i Rb and Sr isotopic ratios for Clachnacudainn Gneiss mineral samples« KF = potassium feldspar sample, BT = biotite sample. These results are plotted in Graph B. ,7182 t .0003(Y2) .7162 + .0008(Y1) i .7141 ± . 0 0 0 8 ( Y l ) ? r .7139 i . 0 0 0 3 ( Y 2 ) f 2 .7137 + . 000KY2)- / g .7125 + ,0001(Y2) o FIGURE iv-5i WHOLE ROCK AND POTASSIUM FELDSPAR DATA AND MINERAL ISOCHRONS BiZ.KF r-oi vr Age (m. vr . J ^ B12t 55 .4 + 1 .8(Y2) B8« 50 .9 + 10.6(Y1) B6-3A1 55 .5 + 9.6(Y1) B6-3« 55 .3 ± 1.7CY2) B2-li 5^.7 + 1.7(Y2) B7-3« 55.8 + 1 .7(Y2) 8 FIGURE IV-51 1 1 1 1 1 1 1 1— 0 0 0.4 0.8 1.2 1.6 2.0 2.4 2.6 3.2 R887/SR86 ATOMIC RATIO 3.8 4.0 —1 4.4 Rb-Sr mineral isochrons f o r the Clachnacudainn Gneiss. This diagram i s an enlargement of the lower l e f t portion of Graph B. Uncertainties are 95% confidence l i m i t s . 52 Sample K-Ar age (m. y r . ) Rb-Sr age (m. y r . ) fo d i s c r e p a n c y o f K-Ar age v e r s u s Rb-Sr age B2-1 53.7 + 3.2 5^.7 + 1 .7 -1.8 B6 - 3 5^.0 + 3.2 55.3 t 1 .7 -2.4 B6-3A 57.9 + 3.7 55.5 1 9 .6 +4.3 B12 55.6 + 3 .3 5 5 . ^ t 1.8 +0.4 B7-3 — 55.8 + 1 .7 — B8 — 50.9 1 10 . 6 — Average a b s o l u t e % d i s c r e p a n c y 2.2 Averages 55.3 5^.6 +1 .3 TABLE IV-5» Comparison o f K-Ar age da t e s and Rb-Sr ages from m i n e r a l i s o c h r o n s . A l l u n c e r t a i n t i e s are 95 % c o n f i d e n c e l i m i t s . T e r t i a r y t h e r m a l e v e n t was i n t e n s e enough t o b r i n g about complete h o m o g e n i z a t i o n o f S r 8 7/Sr86 r a t i o s on a l o c a l s c a l e f o r the m a j o r m i n e r a l s . T h i s c o n c l u s i o n was n o t une x p e c t e d c o n s i d e r i n g t h e p e t r o g r a p h i c e v i d e n c e p r e s e n t e d i n C h a p t e r I I o f i s o t o p i c movement on a t l e a s t a m i c r o s c o p i c s c a l e . P roblems r e l a t i n g t o the r e d i s t r i b u t i o n o f r u b i d i u m and s t r o n t i u m d u r i n g metamorphism have been c o n s i d e r e d by Lanphere e t a l . (1963)1 V/asserburg e t a l . (1964) , A r r i e n s e t a l . (1966) , Brooks (1968), and Ryan, and B l e n k i n s o p (1971) among o t h e r s . S t r o n t i u m i n a r o c k i s bound v/ith c a l c i u m -53 b e a r i n g m i n e r a l s and r u b i d i u m w i t h p o t a s s i u m - b e a r i n g m i n e r a l s . There i s g e n e r a l agreement t h a t d u r i n g metamorphism r u b i d i u m - r i c h , s t r o n t i u m - p o o r m i n e r a l s such as the m i c as and p o t a s s i u m f e l d s p a r l o s e r a d i o g e n i c s t r o n t i u m t o t h e s t r o n t i u m - r i c h m i n e r a l s such as p l a g i o c l a s e , e p i d o t e , a p a t i t e , and c a l c i t e . The hope i s t h a t , a t l e a s t f o r g r a n i t i c r o c k s , no s t r o n t i u m w i l l be l o s t from the t o t a l r o c k system and the r o c k w i l l r e t a i n i t s o r i g i n a l age. B oth the w r i t e r ' s and B l e n k i n s o p ' s whole r o c k r e s u l t s a re p l o t t e d i n F i g u r e I V - 6 and Graph A, A s t r a i g h t l i n e f i t t e d t o t h e d a t a g i v e s an age of 509 - 9^(Y1) m. y r . R e f e r e n c e i s o c h r o n s f o r 5 °9 rn. y r . a n d f o r the 95$ c o n f i d e n c e l i m i t s are p l o t t e d . The s c a t t e r o f t h e d a t a i s c o n s i d e r a b l e and s e v e r a l p o s s i b i l i t i e s e x i s t f o r e x p l a i n i n g i t . The f i r s t i s t h a t i n o b t a i n i n g samples of v a r i o u s s i z e s from v a r i o u s l o c a t i o n s , a s pectrum r a n g i n g from c o m p l e t e l y open t o c o m p l e t e l y c l o s e d systems has i n r e a l i t y been sampled. V a r i a b l e metamorphism t h r o u g h o u t the a r e a may have caused a v a r i a b l e r e d i s t r i b u t i o n o f r u b i d i u m and s t r o n t i u m w i t h i n the r o c k s ; i n p a r t i c u l a r , r a d i o g e n i c s t r o n t i u m may have been l o s t from th e g n e i s s . P e t r o g r a p h i c and f i e l d e v i d e n c e e x i s t s f o r a l t e r a t i o n , r e c r y s t a l l i z a t i o n and m o b i l i z a t i o n w i t h i n the g n e i s s . A l l s u p p o r t the h y p o t h e s i s t h a t t h e c l o s e d system a s s u m p t i o n i s n o t v a l i d . A n o t h e r p o s s i b i l i t y f o r t h e s m e a r i n g o f the d a t a i s t h a t v a r i a b l e c o n t a m i n a t i o n o f the f a i r l y low CO 03 cn 00= OTr-.'' . 7 0 6 5 i . 0 0 1 3 ( Y l ) FIGURE I V - 6 I BEST FIT LINE THROUGH ALL WHOLE ROCK DRTfl 415 m. y r . 0 \ -p-1 1 1 1 1 1 1— 0.0 0.2 0.4 0.6 o.s 1.0 1.; 1.4 RB87/SR86 ATOMIC RATIO 1.6 1.8 2.0 2.2 2.4 FIGURE IV-6 i BPI plot f o r a l l whole rock data f o r the Clachnacudainn Gneiss. A l i n e f i t t e d to the data and two l i n e s representing 95% confidence are plotted. For i d e n t i f i c a t i o n of the data points, see Graph A. s t r a i g h t l i m i t s (Yl) 55 strontium gneiss with country rock strontium has occurred, Armstrong (1974, personal communication) has obtained s i m i l a r s c a t t e r plots to Figure IV-6 f o r Rb-Sr whole rock data from g r a n i t i c rocks i n Idaho. He has suggested that 10 to 20$ digestion and as s i m i l a t i o n of country rocks by injected magmas and/or migmitizing juices would be s u f f i c i e n t to account f o r the scatter i n his data. In the case of the Clachnacudainn Gneiss the contaminant would be approximately 600 m. yr. old metasedimentary rocks v/hich may have been p a r t i a l l y assimilated during the emplacement of the gneiss and/or during the regional metamorphism and accompanying migmitization of rocks within the Shuswap Complex. The strontium i s o t o p i c analyses would thus represent points on mixing l i n e s between the o r i g i n a l i s o t o p i c composition' of the gneiss and the contaminants' i s o t o p i c compositions. A l l eleven La Forme Creek samples have higher Sr87/Sr86 r a t i o s , given a c e r t a i n Rb/Sr r a t i o , than the nineteen Trans-Canada Highway samples have. K/Rb r a t i o s (see Chapter V) also appear to be s t a t i s t i c a l l y higher f o r t h i s group. It i s thus possible that they have l o s t rubidium v/ith respect to Trans-Canada Highway samples and t h i s has caused t h e i r positions on a BPI plot to s h i f t to the l e f t , therefore accounting f o r t h e i r r e l a t i v e l y higher positions f o r the same Rb/Sr r a t i o s . A l t e r nately, one can argue that Trans-Canada Highway samples have gained rubidium with respect to La Forme Creek samples. 56 I t i s p o s s i b l e t o e x t e n d B l e n k i n s o p ' s (1972) i n t e r -p r e t a t i o n o f h i s Rb-Sr whole r o c k d a t a t o a l l o f the whole r o c k d a t a . T h i s i n t e r p r e t a t i o n model i s shown i n F i g u r e I V - 7 . Three ' i s o c h r o n s ' were c a l c u l a t e d from the t h i r t y p o i n t s on t h e g r a p h . An age o f 736 t 4 3 ( Y l ) m. y r . was o b t a i n e d from a s t r a i g h t l i n e f i t t e d t o f i f t e e n p o i n t s . Ages 244 + 20(Y1) m. y r . and 273 t 43(Y1) m. y r . were o b t a i n e d from s t r a i g h t l i n e s f i t t e d t o e l e v e n Trans-Canada Highway samples and s i x L a Forme Creek samples r e s p e c t i v e l y . Three d a t a p o i n t s were no t used f o r ' i s o c h r o n ' c a l c u l a t i o n s . A l l the ' i s o c h r o n s ' show s c a t t e r o f d a t a beyond the l i m i t s o f e x p e r i m e n t a l e r r o r . The w r i t e r d i s a g r e e s w i t h t h i s i n t e r p r e t a t i o n f o r s e v e r a l r e a s o n s . F i r s t l y , t h e i n t e r p r e t a t i o n n e c e s s i t a t e s d r a w i n g i s o c h r o n s t h r o u g h s e l e c t e d d a t a . I n t h i s c a s e , i t was not done o b j e c t i v e l y ; r a t h e r i t was done i n such a way t h a t the r e s u l t s would b e s t s u p p o r t the i n t e r p r e t a t i o n . I f one l o o k s a t the d a t a i n Graph A i t i s c e r t a i n l y n ot i m m e d i a t e l y o b v i o u s how one o r more l i n e s c o u l d b e s t be drawn t h r o u g h most o r a l l o f the p o i n t s . The w r i t e r f e e l s t h a t i t i s v a l i d t o draw s e l e c t e d i s o c h r o n s t h r o u g h such d a t a o n l y i f the s e l e c t i o n i s based on some g e o g r a p h i c a l , g e o c h e m i c a l o r g e o l o g i c a l a s s o c i a t i o n ; i . e . , one b i g o u t c r o p o r one r o c k type o r one map u n i t o r s u b u n i t . I n t h i s c a s e , samples w h i c h l i e on the younger i s o c h r o n s are not d i f f e r e n t i a t e d i n any known way from samples wh i c h l i e on .7111+.0008(Y1) ,70951.0003(Y1) . 7 0 ^ 3 + . 0 0 0 5(Yl) in FIGURE iv-7«THREE ISOCHRON INTERPRETATION MODEL FOR WHOLE ROCK DATA 736 ± 43(Yi) 273 ± 43(Y1) m. yr. 244 +•20(Y1) m. yr. * point not used for isochron calculation 0.0 0.2 - 1 — 0.4 o.s I I 1 0.8 1.0 1.2 RB87/5R86 ATOMIC RATIO ^ — 1.4 - 1 — 1.6 —1— 1.8 - 1 — 2.0 — T — 2.2 — I . 2 . 4 FIGURE IV-7» Three isochron i n t e r p r e t a t i o n model f o r whole rock data. Uncertainties are 95$ confidence l i m i t s . For i d e n t i f i c a t i o n of the data points, particularly La Forme Creek samples, see Graph A. 58 the older isochron. It i s d i f f i c u l t to envisage how the strontium compositions of just various selected portions of the gneiss were completely homogenized about 250 m. yr. ago whereas the strontium compositions of other various selected portions of the gneiss were unaffected. The writer would agree, however, to d i v i d i n g the data up into two groupsJ La Forme Creek samples versus Trans-Canada Highway samples. If t h i s i s done and st r a i g h t l i n e s are f i t t e d to the two groups of data, the following r e s u l t s are obtained 1 (1) La Forme Creek samples Age« 403 + 88(Y1) m. yr. I n t e r c e p t 0 . 7 0 9 3 t 0 .0015(Y1) (2) Trans-Canada Highway samples Agei 430 + 106(Y1) m. yr. Intercept: 0 . 7 0 7 0 + 0 . 0 0 1 M Y 1 ) These 'ages' do not d i f f e r s i g n i f i c a n t l y from the 509 t 9 M Y 1 ) m. yr. 'age' (Figure IV-6) obtained from a l l the data or the 451 + 123(Y1) m. yr. 'age' (Figure IV - 4 ) obtained from the writer's data alone. Another reason f o r not agreeing with the three isochron i n t e r p r e t a t i o n model i s that f o r Blenkinsop's (1972) data alone (see f i f t e e n data points, Figure IV -2) the i n t e r p r e t -ation holds, whereas f o r the writer's data alone (see f i f t e e n data points, Figure IV - 4 ) the i n t e r p r e t a t i o n does not seem to hold; i . e . , f o r the same number of samples, the writer has 59 n o t r e p r o d u c e d B l e n k i n s o p ' s p a t t e r n . I n a d d i t i o n , t o t h e w r i t e r ' s knowledge, no p u b l i s h e d Rb-Sr d a t a from any o t h e r a r e a has e v e r been demonstrated t o e x h i b i t t h r e e s i g n i f i c a n t ages (two whole r o c k ages and one m i n e r a l age) from the same r o c k u n i t . Thus, a l t h o u g h t h e i n t e r p r e t a t i o n o f F i g u r e IV-7 g e n e r a t e s numbers which are v e r y a p p e a l i n g i n terms o f what i s known of r e g i o n a l t e c t o n i c h i s t o r y , the w r i t e r f e e l s t h a t c u r r e n t e v i d e n c e does not p r e s e n t l y s u b s t a n t i a t e i t . F o r a BPI p l o t , such as Graph A, the i n t e r p r e t e r must s e l e c t which p o i n t s t o f i t an ' i s o c h r o n ' t o . As mentioned p r e v i o u s l y , i t i s d i f f i c u l t t o do t h i s o b j e c t i v e l y i f one i s n o t g u i d e d by e x t e r n a l c r i t e r i a . I f no c r i t e r i a e x i s t s , i t i s s u g g e s t e d t h a t one p l o t the d a t a on a C o m p s t o n - J e f f e r y diagram (see Appendix B f o r t h e o r y ) . The Rb-Sr whole r o c k d a t a i n Graph A has been p l o t t e d on a C o m p s t o n - J e f f e r y diagram i n Graph C. I n t e r p r e t i n g t h i s diagram i n v o l v e s d e t e r m i n i n g the most l i k e l y i n t e r s e c t i o n p o i n t o r p o i n t s of i n d i v i d u a l sample l i n e s . T h i s was done i n Graph D. Graph D i s an e q u a l - a r e a d e n s i t y p l o t of the i n t e r s e c t i o n p o i n t s o f sample l i n e s i n Graph C (see Appendix I f o r a d e s c r i p t i o n o f how t h i s was done). M a j o r maxima o c c u r a t 715. 385 and 240 m. y r . and a minor maxima a t 14-0 rn. y r . F u r t h e r m o r e t h e s e maxima are not independent o f each o t h e r as i n d i v i d u a l sample l i n e s c o n t r i b u t e t o more t h a n one. The w r i t e r f e e l s t h a t i t i s o f some b e n e f i t t o l o o k a t 60 s c a t t e r e d Rb-Sr d a t a i n t h i s form as the mechanism o f p r e p a r i n g the diagram l e t s t he d a t a i t s e l f d e t e r m i n e i t s most l i k e l y age o r ages. The w r i t e r ' s p r e f e r r e d i n t e r p r e t a t i o n o f the v/hole r o c k d a t a i s t h a t the assumptions f o r d r a w i n g an i s o c h r o n are n o t met, v a r i a b l e i n i t i a l s t r o n t i u m r a t i o s b e i n g i n d i c a t e d . Thus, no m e a n i n g f u l Rb-Sr 'age' can be r e p o r t e d . T h i s c o n c l u s i o n t h e r e f o r e p r o v i d e s no i n s i g h t i n t o the pro b l e m o f d e t e r m i n i n g the o r i g i n o f the C l a c h n a c u d a i n n G n e i s s . T h i s i s c o n t r a r y t o the s u g g e s t i o n o f B l e n k i n s o p (1972) t h a t the Rb-Sr whole r o c k d a t a s u p p o r t e d the c o n c l u s i o n t h a t the g n e i s s i s d e m o n s t r a b l y o l d e r t h a n the e n c l o s i n g s e d i m e n t s . F u r t h e r m o r e , the above c o n c l u s i o n has i m p o r t a n t i m p l i c a t i o n s w i t h r e s p e c t t o the ' i s o c h r o n s * d e t e r m i n e d by B l e n k i n s o p (1972) f o r the M a l t o n G n e i s s and the Quesnel Lake G n e i s s . I f a d d i t i o n a l Rb-Sr d a t a i s o b t a i n e d f o r t h e s e two g n e i s s b o d i e s , i t i s s u g g e s t e d t h a t c o n s i d e r a b l e s c a t t e r w i l l become e v i d e n t . Thus, the r e p o r t e d 'ages' o f t h e s e b o d i e s m entioned e a r l i e r are perhaps s p u r i o u s . I n any e v e n t , a d d i t i o n a l d a t a i s needed t o c o n f i r m o r deny t h i s . 61 CHAPTER V GEOCHEMICAL CONSIDERATIONS The objective of t h i s chapter i s to look b r i e f l y at the varia t i o n s i n the amounts of potassium, rubidium and strontium i n the various whole rock samples of the Clachnacudainn Gneiss. Rubidium and strontium concentrations were determined by the XRF method and potassium concentrations by flame photometry. The r e s u l t s are l i s t e d i n Appendix H, Tables H-8 and H-14 and summarized i n Figures V - l to V-4, Figures V-l to V-4 are chemical v a r i a t i o n diagrams prepared f o l l o w i n g the suggestions of Pearce (1968) that molar and molar r a t i o comparisons of various components i n rocks be used, rather than weight percent comparisons. La Forme Creek samples are d i f f e r e n t i a t e d from Trans-Canada Highway samples on a l l diagrams. Figure V-l i s a comparison of strontium versus rubidium. I t e x hibits the general pattern that as the amount of rubidium increases, the amount of strontium decreases. This presumably r e f l e c t s the varying mineralogy of the gneiss. As the amount of potassium-bearing minerals, such as the micas and potassium feldspar, increase, the amount of calcium-bearing minerals, such as plagioclase, decrease. Figure V-2 shows the expected r e l a t i o n s h i p between rubidium and potassium; i . e . , the amount of rubidium increases with the amount of potassium. This r e l a t i o n s h i p also governs the CD in CD CO cn' co ® C D Q CD 0 CD ® 1 1.8 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Rubidium (micromoles/gram of sample) 1.6 FIGURE V-l» Plot of strontium versus rubidium for Clachnacudainn Gneiss whole rock samples. The points marked with a X a r e ^ a Forme Creek samples. CD C3 . CD fX) PH in 3 1 f"3 CO . CM ® ® o ® 0 CD 0 CD 0 0 0 ® - i 1 1 1 r— 0.6 0.8 1.0 1.2 1.4 Rubidium (micromoles/gram of sample) 1 1.8 0.2 0.4 1.6 FIGURE V - 2 i Plot of potassium versus rubidium f o r Clachnacudainn Gneiss whole rock samples. The points marked with a X are La Forme Creek samples. o o ID o • H - P o e o -p cd ?-< CO a CM ® © a CO O O ^ 0.1 FIGURE V-3 i 0.2 0.3 ® ON ® ®® O o® CD O 0.6 0 . 7 0 . 8 0 . 9 0.4 0.5 Rb/Sr atomic r a t i o Plot of K/Sr r a t i o s versus Rb/Sr r a t i o s f o r Clachnacudainn Gneiss whole rock samples. The points marked with a X a^e La Forme Creek samples. o NT. 12 o m a o • H - P o • r-l o -p 9H a fM. Cn a CM 0.0 CD ® * % ° O o ® 2.0 4.0 ON -1 1 1 6.0 8.0 10.0 Sr/Rb a t o m i c r a t i o 12.0 14.0 16.0 FIGURE V-4j P l o t o f K/Rb r a t i o s v e r s u s Sr/Rb r a t i o s f o r C l a c h n a c u d a i n n Gneiss whole r o c k samples. The p o i n t s marked w i t h a X are L a Forme Creek samples. 66 pattern seen i n Figure V - 3 , where K/Sr r a t i o s are plo t t e d against Rb/Sr r a t i o s . Figure V-4 i s a comparison of K/Rb r a t i o s versus Sr/Rb r a t i o s . No obvious pattern exists although there appears to be a s l i g h t upward trend to the rights The average K/Rb atomic r a t i o of eight La Forme Creek samples was 516 versus 444 f o r twelve Trans-Canada Highway samples. 67 CHAPTER VI CONCLUSIONS F o u r K-Ar b i o t i t e ages and s i x Rb-Sr m i n e r a l i s o c h r o n ages i n d i c a t e t h a t a 55 m. y r . T e r t i a r y t h e r m a l event has a f f e c t e d the C l a c h n a c u d a i n n G n e i s s . T h i s event i s w i d e s p r e a d o v e r much o f s o u t h e a s t e r n B r i t i s h C o l u m b i a and the n o r t h -w e s t e r n U n i t e d S t a t e s ( G a b r i e l s e and Re e s o r , 1964; M e d f o r d , 1974; Ross, 1974; A r m s t r o n g , 1974, p e r s o n a l c o m m u n i c a t i o n ) . The event was i n t e n s e enough t o r e s e t the K-Ar and Rb-Sr a t o m i c c l o c k s on a m i n e r a l s c a l e . The K-Ar r e s u l t s were o b t a i n e d w i t h a l o t l e s s e f f o r t t h a n the Rb-Sr r e s u l t s . I t i s t h e r e f o r e s u g g e s t e d t h a t the K-Ar method, b e i n g e a s i e r and f a s t e r , i s the one t o use t o s t u d y m i n e r a l ages i n and around the core zone o f the Columbian Orogen. Rb-Sr whole r o c k d a t a from the C l a c h n a c u d a i n n G n e i s s shows q u i t e a s p r e a d and i s not seen t o s u p p o r t B l e n k i n s o p ' s (1972) i n t e r p r e t a t i o n o f two ages, a 740 m. y r . o l d ev e n t and a 240 m. y r . o l d e v e n t . The p r e f e r r e d i n t e r p r e t a t i o n i s t h a t v a r i a b l e i n i t i a l s t r o n t i u m r a t i o s are i n d i c a t e d and t h u s the assumptions f o r d r a w i n g an i s o c h r o n are not met. The w r i t e r f e e l s t h a t some i n s i g h t i n t o the i n t e r p r e t a t i o n o f smeared and s c a t t e r e d Rb-Sr whole r o c k d a t a can be o b t a i n e d by l o o k i n g a t the d a t a on a C o m p s t o n - J e f f e r y diagram. 68 There i s s t i l l a p o s s i b i l i t y , o f c o u r s e , t h a t a 600-900 m. y r . o l d event ( E a s t Kootenay O r o g e n y ( ? ) ) i s i n d i c a t e d r e g i o n a l l y i n s o u t h e a s t e r n B r i t i s h C o l u m b i a . However, a t the p r e s e n t t i m e , t h e u n c e r t a i n t y due t o the s c a t t e r i n t h e Rb-Sr whole r o c k d a t a from the C l a c h n a c u d a i n n G n e i s s and from t h e Quesnel Lake and M a l t o n G n e i s s e s ( B l e n k i n s o p , 1972) does not p e r m i t t h i s e v ent t o be p i n n e d down r e l i a b l y on the b a s i s o f Rb-Sr d a t a . U n f o r t u n a t e l y no i n s i g h t has been g a i n e d i n t o the problem o f d e t e r m i n i n g the o r i g i n o f the C l a c h n a c u d a i n n G n e i s s . The g n e i s s may r e p r e s e n t metamorphosed Windermere se d i m e n t s o r metamorphosed P u r c e l l s t r a t a o r metamorphosed H u d s o n i a n ( ? ) basement. The e v i d e n c e t o date s t i l l does n o t d e f i n i t i v e l y p r e c l u d e any o f t h e s e p o s s i b i l i t i e s . I t seems h i g h l y l i k e l y t h a t l e a d i s o t o p i c a n a l y s e s o f z i r c o n s w i l l p r o v i d e the o l d e s t age date seen from the C l a c h n a c u d a i n n G n e i s s . A s t u d y o f z i r c o n s from m a t e r i a l sampled by t h e w r i t e r i s p r e s e n t l y under way (Ross, 1 9 7 5 i p e r s o n a l c o m m u n i c a t i o n ) . 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Phys., 44, 1079-1086. Y o r k , D. (1967). The b e s t i s o c h r o n . E a r t h P l a n e t . S c i . L e t t e r s , 2, 479-482. Y o r k , D. (1969). L e a s t - s q u a r e s f i t t i n g o f a s t r a i g h t l i n e w i t h c o r r e l a t e d e r r o r s . E a r t h P l a n e t . S c i . L e t t e r s , j>, 320-324. Y o r k , D., and R. M. F a r q u h a r (1972). The e a r t h ' s age and g e o c h r o n o l o g y . Pergamon P r e s s L t d . , O x f o r d . Youden, W. J. (1951). S t a t i s t i c a l methods f o r c h e m i s t s . J. W i l e y and Sons I n c . , New York. 75 0 . 0 0.3 APPENDIX A LOCATION OF SAMPLE SITES ) Trans-Canada highway outcropst A l l outcrops are located on the north side of the highway. Mileages are recorded driving east. Mileage Description bridge across Clachnacudainn Creek gate to Revelstoke National Park 2.4 picnic ground 3 . 0 outcrop of gneissi B7-3 west end B 7 -2 east end 3.3 outcrop of gneissi B 7 - 1 4.1 two creeks crossing highway 200 feet apart 4.6 outcrop of swirled gneiss« B6-3A,B6-3 west end B6-2 east end G6 - 2(granitic dike) east end 4 . 8 outcrop of gneissi B 6 - 1 5 . 8 creek crossing highway 6 . 2 - 7 . 1 outcrop of metasedimentary rockt B 5 - 1 7 . 4 picnic ground 8 . 4 5 bridge across Silver Creek 9 . 0 5 outcrop of gneiss» B4-X,B4-Y G4(granitic dike) 9 . 6 5 outcrop of gneisst B3 9 . 75 outcrop of gneissj B2-1 9 . 8 5 outcrop of gneissi Bl - 1 76 (2.) Big Bend highway outcropsi A l l outcrops are located on the east side of the highway. Mileages are recorded driving north. Mileage Description 0.0 Big Bend highway turnoff on the Trans-Canada highway just outside of Revelstoke 6.15 Silver Tip Falls 9.05 outcrop of quartz diorite 1 B15 9.8 outcrop of quartz diorite 1 Bl4 15.25 turnoff for La Forme Creek road on the east side of the highway (3.) La Forme Creek road outcropst A l l outcrops are located on the south side of the road. Mileages are recorded driving east. Mileage Description 0.0 start up the road 2.1 outcrop of gneiss i B13 2.55 outcrop of gneiss 1 B12 2.75 outcrop of gneiss« B l l 2.9 outcrop of gneiss« BIO 3.15 outcrop of gneiss 1 B9 3.55 outcrop of gneissJ B8 4.1 intersection of the road with La Forme Creek at an old mine 77 APPENDIX B BASIC THEORY OF RB-SR AND K-AR GEOCHRONOLOGY1 INTRODUCTION Both the rubidium-strontium and the potassium-argon age-dating methods are based on the radioactive decay equation P = Pje"*£ (1) where P = the number of radioactive parent atoms present at time t Pi= the i n i t i a l number of radioactive parent atoms at time t=0 A* = decay constant which represents the p r o b a b i l i t y of the decay of an atom i n unit time For geochronology one arranges (1) to get P i = P e X t ( 2 ) where P = the number of atoms of the radioactive parent i n a sample of rock at present t = the time period from the formation of the rock (t=0) to the present; i . e . , the age of the rock Define D = the number of daughter atoms i n a sample o f rock at present Di= the number of daughter atoms i n the sample o f rock when i t was formed (D-Di) i s thus the number of radiogenic daughter atoms pro-duced. I f neither parent nor daughter atoms are removed o r added from the rock system, then D + P = Di + P i (3) 1Adapted from Blenkinsop (1972) with additional information fronf Dalrymple and Lanphere (1969)» York and Farquhar (1972), and Lanphere et a l . (1963). 78 F r o m equation ( 2 ) , D-Di = e U - l . (if) ' ~P and t = i l o g e p + D-Di j (5) This i s known as the general age equation. RB-SR METHOD The Rb -Sr method i s based on the simple decay of Rb87 to Sr87. Thus t = 1 loge / l + Sr87* \ (6) \, [ R W j where Sr87* = Sr87 - Sr87i = the radiogenic Sr accumulated i n time t This equation was used for several years before the d i f f i c u l t y of evaluating Sr87i was f u l l y appreciated. Equation (4) can be rearranged, and each side divided by a suitable index isotope (one that i s neither radioactive nor radiogenic). For Rb-Sr geochronology, Sr86 i s the most useful index isotope because i t occurs in about the same abundance as Sr87. Equation (4) then becomes Sr87 - /Sr87\ + Rb87 . ( e ^ - l ) ( 7 ) sFSo" ( S?B%/i sFSt V ' The quantities Sr87/Sr86 and Rb87/Sr86 are measurable i n the lab-oratory, and X is known (with some uncertainty), leaving only t 79 and (Sr87/Sr86)i to be determined. The evaluation of the two quantities requires, of course, data from at least two oogenetic samples. In practice, several samples from each rock unit are analyzed, and the results are presented graphically. The f i r s t method of graphical presentation, proposed by Gompston and Jeffery (1959)$ made use of the identity Sr§7 = /Sr87\ + Rb87 Sr87* Sr86 ISrSoJi Sr86 ' Rbo7 Rearranging terms leads to Sr87* = Sr86 (Sr8? - /Sr8?\ 1 (8) Rb87 Rb87 (Sr86 \Sr86jiJ which is the equation of a straight line between Sr87*/Rb87 and (Sr87/Sr86)i. A sample thus defines a straight line on the graph (Figure B-l), with the intercept on the Sr87*/Rb87 axis being the measured Sr87/Rb87 ratio of the sample, and the intercept on the (Sr87/Sr86)i axis being the measured Sr87/Sr86 ratio. The slope of the line is the negative of the Sr86/Rb87 ratio; i.e., i t i s always negative. Sr87* Rb87 (Sr87/Sr86)i FIGURE B-lt Compston-Jeffery plot. 80 Samples from a oogenetic suite w i l l define a number of l i n e s on such a graph, one l i n e f o r each sample. I f the closed system assumption has been s a t i s f i e d , the l i n e s w i l l i n t e r s e c t at a common point, the coordinates of which give the (Sr87*/Rb8?) and (Sr87/Sr86)i r a t i o s f o r the s u i t e . The age of the rocks can then be calculated jfrom the equation An a l t e r n a t i v e graphical presentation of Rb-Sr data was proposed by workers at the Bernard Price I n s t i t u t e (Hales, i 9 6 0 ) , and t h i s BPI plot i s the method i n common use today. They pointed out that equation (7) i s also an equation of a stra i g h t l i n e , i n t h i s case between S r 8 7 / S r 8 6 and R b 8 7 / S r 8 6 , where each sample defines a point on the graph (Figure B - 2 ) , If a l l samples are oogenetic, and i f the closed system assumption has been s a t i s f i e d , the points w i l l define a str a i g h t l i n e of slope e ^ - l and intercept (Sr87/3r86)^. The BPI plot i s generally preferred to the Compston-Jeffery plot because the s t a t i s t i c s of f i t t i n g points to a l i n e are easier and better understood than the s t a t i s t i c s of the i n t e r s e c t i o n of a series of l i n e s . Sr87* = e ^ - l Rb87 (9) Sr87 Sr86 isochron (Rb87/Sr86) FIGURE B-21 BPI p l o t . 81 The simplest model to interpret i s one i n which a suite of samples has recorded only one event, such as i t s intrusion or a severe metamorphism. As a result of the event, a l l t o t a l rocks and minerals i n the suite had the same strontium isotopic composition, but varied i n their Rb/Sr ratios. At this i n i t i a l time, a l l samples defined a horizontal line on the BPI diagram. As Rb87 decayed to Sr87, a l l points moved along lines with a slope of -1, but maintained their colinearity, as shown i n Figure B-3. Sr87 Sr86 isochron for time t, rtan"" 1 (e^' -l) /Sr87) (Rb87/Sr86) O i n i t i a l composition © f i n a l composition FIGURE B-3» Strontium evolution diagram (BPI plot) showing the time evolution of Sr87/Sr86 and Rb87/Sr86 (after Lanphere et al . , 1 9 6 3 ) . After a time t, , the points, both total rocks and minerals, l i e on an isochron of slope e ^ ' - l . A more complicated model is required i f a second, less intensive, event has affected the samples. This situation is 82' shown i n Figure B-4. For s i m p l i c i t y i t i s assumed that the t o t a l rock system has remained closed. Sr87 Sr&6 SrB6 isochron f o r time t, W )=tan" 1(e 7 L t' - l ) Sr isotopic rehomogenization in minerals At (Rb8?/Sr86) Closed system i n the i n t e r v a l 0 to t t followed by rehomogenization of Sr i n minerals. The adjustment of Rb/Sr r a t i o s at time t, i s represented by arrows with a r b i t r a r y d i r e c t i o n ending on horizontal l i n e S £. isochron f o r time t x isochron f o r time ( t ^ - t , ) Bt (Rb87/Sr86) Closed system i n the i n t e r v a l t, to t^,. O i n i t i a l composition 9 f i n a l composition I • intermediate compositions FIGURE B-4 Strontium evolution diagrams showing the .effects of i s o t o p i c homogenization f o r a two episode model f o r a t o t a l rock r and four of i t s constituent minerals mi , rri2» mo, and ra^ (after Lanphere et a l . , 19o3). 83 This i s one possible effect of a metamorphic event during which the minerals in a rock exchanged strontium and possibly rubidium, but the total rock system, considered in a large enough sample, did not lose or gain either strontium or rubidium. If exchange was complete, the minerals lost a l l memory of their previous history and once again lay on a horizontal l i n e . Under the stated assumptions, the angle oc (see Figure B-4) determines the time of the secondary event (e.g., metamorphism) and of strontium rehomogenization in mineral samples. The angle cxx for the total rock system determines the time of the original event (e.g., formation) and of original strontium homogenization in the rock system. If we now consider a two episode model for a group of similar total rock samples, then we w i l l obtain the pattern exhibited (Rb67/Sr86) ^ FIGURE B-5« Strontium evolution diagram for mineral phases and total rocks of different i n i t i a l Rb87/Sr86 for a two episode model (after Lanphere et a l . , 1963) . 84 It i s quite possible that the total rock systems w i l l gain or lose rubidium and strontium as well, in which case i t w i l l be d i f f i c u l t or impossible to date the primary event. If strontium in the minerals is not properly homogenized, the mineral data w i l l not provide a useful determination of the secondary event. The above interpretation models have established the ground rules whereby one can study rock systems that have undergone a polymetamorphic history. More complicated models than those considered, such as continuous diffusion or multiple event models, are possible, but there is seldom enough information to apply them usefully. The effects of contamination can seriously disrupt theoretical or predicted patterns as seen on a strontium evolution diagram. Figure B-6 shows these effects. r r o o/contam. (Rb8?/Sr86) FIGURE B-6t Strontium evolution diagram showing effects of contamination (after Lanphere et a l . , 1963). 85 K-AR METHOD The K-Ar method i s based on the branching decay of K40 to Ar40 and K40 to Ca40. Because of the widespread abundance of Ca40, only the K40-Ar40 branch of the decay i s useful f o r the age dating of rocks. The dual decay requires that one calculate the K-Ar age of a mineral or rock from a modified form of equation (5 ) i "t = i l o g e f 1 + ( 1 + R ) Ar40*l (10) X I R *"K5o j where X - t o t a l decay constant = Xt + Xp % b - decay constant of K40-Ar40 Xi- decay constant of K40-Ca40 R#= branching r a t i o = X(JT^^ Ar40 = radiogenic argon accumulated i n time t It i s generally assumed that Ar^O^ can be neglected, and the large number of concordant ages i n the l i t e r a t u r e suggest that t h i s assumption i s v a l i d f o r most rock systems. Thus, one may obtain a K-Ar age date from a single sample, provided, of course, that the sample system did not lose or gain e i t h e r potassium or argon during the i n t e r v a l from the event to be dated to the present. The problem of extraneous argon i s discussed i n Dalrymple and Lanphere ( 1 9 6 9 ) . One may rewrite equation (10) as follows, Ar40* = _R_ . K40.. ( e x t - l ) (11) (1+R) In order to demonstrate the concordance of several age-dates from samples from the same geological u n i t , one may plot a 86 graph of Ar40* versus K40. This should be a straight line plot with an Ar40* intercept of zero and a slope of R/U+R) . ( e x t - l ) . (see Figure B-7) Ar40* K40 FIGURE B-7i Plot of K-Ar data for several samples from a oogenetic suite of rocks. Measuring the Ar40* i n a rock involves the use of a gas source mass spectrometer. The argon present i n the gas handling system w i l l be a mixture from three sourcest (1) Ar40* expelled from the sample (2) any contaminating atmospheric argon (Ar40^, Ar38 A, Ar36^) introduced during the experiment (3) any tracer argon (Ar^ O r p , Ar38T, Ar36T) introduced via the isotopic dilution technique. If one corrects for the composition of the tracer, one may write Ar^ Ojyi = Ar40 A + Ar40* where A r 4 % = the mixture of Ar40 A and A r 4 0 * 87 Dividing both sides by Ar36^. and substituting equation (11), As an alternate to Figure B-7, one may present data from a oogenetic suite of samples by plotting a graph of (Ar4o/Ar36)M versus Y^Q/kv^6^. One should obtain a straight line plot with an intercept of (Ar4o/Ar36)^ (independently known) and a slope of R/dHRMe**-!). (see Figure B-8) (12) (IrlSJ / Ar40\ M (K40/Ar36A) FIGURE B-8i Alternative plot of K-Ar data for several samples from a oogenetic suite of rocks. 88 APPENDIX C MASS SPECTROMETRY INTRODUCTION The argon isotopic analyses reported in Appendix H were performed by the writer on a gas-source mass spectrometer (M.S.10) designed and built by G. P. Erickson and operated by J . Harakal of the Geology Department, U.B.C. The strontium isotopic analyses reported in Appendix H were performed by the writer on two solid-source mass spectrometers, hereafter referred to as M.S.2 and M.S.3i located in the isotopes lab at the Department of Geophysics and Astronomy, U.B.C. M.S.2 i s the older machine and has been used extensively since 1968 for lead and strontium work, M.S.3 was built during 1973-74. The system used for measuring strontium isotopic ratios was set up by J. Blenkinsop and R.D. Russell and is described in Blenkinsop (1972) and in Russell et a l . (1971). The writer was involved, during his research, in the i n i t i a l building and operation phases of M.S.3. This appendix outlines and describes M.S.3. particularly the options and instrumentation not previously used on mass spectrometers at U.B.C. GENERAL CONFIGURATION OF M.S.3 M.S.3 i s a 12 inch (30 cm,), 90 degree, single-focusing mass spectrometer designed by R.D. Russell and J.M, Ozard for use as a solid-source machine for lead and strontium analyses. 89 A schematic diagram i d e n t i f y i n g the various components i s shown i n Figure C - l . A primary consideration i n the design of M.S.3 was a low background pressure and a quick pump-down time to a t t a i n t h i s pressure. This i s necessary because a solid-source machine must be exposed to atmospheric pressure every time a new sample i s to be loaded. The pump-down period of M.S.3 when the whole machine has been brought up to atmospheric pressure i s one to two days. For a sample loading, only the source hat i s brought up to atmospheric pressure; hence, operating pressures can be reached i n 2-4 hours. The operation of the vacuum system i s described as follows. M.S.3 i s roughed out by an Edwards backing pump to about 10~3-10""^ t o r r (10 minutes). A Varian d i f f u s i o n pump, located on the source end of the instrument, i s then connected to the system v i a an a i r -operated valve (see Figures C-l and C - 2 ) . When the pressure f a l l s to les s than 10"5 t o r r (20-30 minutes), an ion pump, located on the c o l l e c t o r end of the instrument, i s switched on. The writer used a Dirvac 30 l i t e r / s e c . ion pump, but t h i s t has since been replaced by a Vaclon Model 912-7006, 110 l i t e r / s e c . ion pump. Ultimate vacuum reached (to June 1974) was 1 X 10~7 t o r r . Operating pressure was generally between I X 10""7 t o r r and 3 x l 0 " 7 t o r r . When a new sample i s to be loaded, an air-operated valve i s closed, thus i s o l a t i n g the source hat from the rest of the system under vacuum. The source hat can then be ion guage ^ sglass port m m " feedthrough roughing •pump FIGURE C - l i Schematic diagram of M.S.3. The scale i s approximately 116. compressed air n manually actuated valves California Physics Products a i r -operated valves < 5 closed open Source valve clLoseq open Diffusion valve closed Beam valve FIGURE C-2i Configuration of air-operated valves on M.S.3. See Figure C-l for the location of the valves. 92 independently brought up to atmospheric pressure. The beam tube and the c o l l e c t o r end of the instrument are pumped only by the ion pump at t h i s stage. Samples are loaded through a glass-covered port located i n the source hat. The hat i t s e l f i s sealed to the baseplate by a Viton O-ring and i s only removed when the source assembly i s to be cleaned. The configuration of the source and c o l l e c t o r assemblies, as used by the writer, are shown i n Figures C-3 and C-4 r e s p e c t i v e l y . The ion source used was the Loveless and Russell (1969) version of the b a l l assembly design. The thick electrodes i n the x and ^ d i r e c t i o n s give t h i s source strong focusing properties. The c o l l e c t o r configuration i s s i m i l a r to previous designs used, the only difference being the r e l a t i v e spacing of the suppressor plates. The filament current supply, the magnet current supply and the vacuum guage supply are based on those described i n Russell and B e l l i s (1971) . These supplies, as used by the writer, d i f f e r e d only s l i g h t l y from the o r i g i n a l published designs. The t r i g g e r board c i r c u i t has since been redesigned by R.D. Meldrum and the above supplies modified ( l a t e 1974). The ion pump supply and the high voltage supply are new and were designed by R.D. Meldrum and R.D. Russell. The measuring system (see Figure C-5) on M.S.3, used by the writer, involved the a p p l i c a t i o n of a Teledyne P h i l b r i c k #1702 parametric amplifier as an ion current amplifier. The use of t h i s amplifier on mass spectrometers at U.B.C. i s <1 * S l i t Widths dire c t i o n ) Plate Inches No, (X10-3) 3 4.2.7*0.5 10 .5*0 .5 5 30.2±0 .5 6 10 . 4±0 . 5 FIGURE G-3» M.S.3 source and mounting assembly drawn approximately to scale. baseplate FIGURE G-4i M.S.3 c o l l e c t o r and mounting assembly drawn approximately to scale. VO i o n beam At F i r s t amplification stage at the mass spectrometer. shunt selector 0.33Af to d i g i t a l voltmeter 10K 100K boost chart recorder Bt Ladder attenuator and second amplification stage at the control console. FIGURE C-5t Measuring system on M.S.3. The ladder attenuator gives a factor of three attenuation per switch position,, It i s custom made by Electro Scient i f i c Industries to a precision of 0 .025$. 96 described i n Russell and Ahern (1974). It replaced the electrometer tubes previously used on the solid source machines. The f i r s t amplification stage of the measuring system (see Figure C-5) has since been redesigned (late 1974) and presently consists of a Bendix continuous dynode electron multiplier (CDEM) instead of a faraday cup and parametric amplifier. OPERATION OF THE MEASURING SYSTEM The #1702 parametric amplifier and the I O ^ J L feedback resistor are mounted on a circ u i t board inside the collector hat (as indicated i n Figure C-4). The output of this amplifier is fed from the mass spectrometer back to the control console and into a ladder attenuator, a secondary amplification stage, and a d i g i t a l voltmeter (or chart recorder) respectively. The shunt coefficients for the ladder have been measured and are l i s t e d i n Table C-l. The theory of operation of the measuring system i s given as follows (see Figure C-6)t F i r s t Amplification Stagei from Figure C-6A, i = 1. jwC2 e + ( e - e a ) R / > C i R + U / j w C l ) substituting e=-e0/G, 97 s i g n a l out shunt 1 2 3 4 5 1 1 3.00044 +0.00014 9.0021 +0.0008 27.012 +0.007 81.103 10.066 2 \0>33X3285* \+o.o.oooi5N \ \ \ "\ 1 3.00044 +0.00014 9.0009 10.0012 26.998 I0 .007 lal in 3 s 0;li ' 1085 N+o;ooooi \ \ \ \ 0.3 n33285*N lo.000015 \ '• 1 3.00021 +0.00009 9.0009 10.0008 S. •H W 4 0.37020 \ io.ooooi \ \ \ •  \ ,0/11110 ^  +0.000015 \ \ \ 0.33331* +0.00001-\ \ 1 3.00021 lo.00009 5 \ o . 01233 N \+0.00001 -\ ^ N. \ \ \ \0>03704X\ lc\ooooV \ \ \ x .0.11110 +0.00001 . \ \ x •o.3333i-* +0.00001 . \ \ "\ ' • 1 The shaded area indicates measured q u a t i t i e s . Uncertainties quoted are estimated possible errors. Using the four indicated measurements (*) above, the shunt factors f o r the measuring system i n Figure C-5 were calculated! shunt shunt f a c t o r 1 % uncertainty % difference from nominal value 1 1 0 2 '(1/3.00044) 1 0.0045% - (0.0145 1 0.0045)% 3 (1/9.00261) 1 0.0065% - (0.029 1 0.0065)% 4 (1/27.0097) 1 0.007% - (0.0360 1 0,007)% 5 (1/81.0348) 1 0.0075% - (0,0430 1 0.0075)% TABLE C-lt Shunt c o e f f i c i e n t s f o r the ladder attenuator i n M.S.3 r Cl +-R 6 e; e„ Ai F i r s t a mplification stage i = ion current e = input voltage (theoretically= 0 ) e„ = output voltage of f i r s t stage ej_= e-e 0 G = open loop dc gain = -e»/e R = feedback r e s i s t o r = lO^-^jv Bt Second a m p l i f i c a t i o n stage v^ = input voltage of second stage = output voltage of ladder attenuator R„ = 3 OK Jl Ri = 330Kj\. R2 = 10K JV C 3 = 0.33Af v 0 = output voltage of second stage Q varies from 1 to 0 i n increments of 0.1 and i s set by the boost switch FIGURE C-6i D e f i n i t i o n of terms used i n developing the theory of operation of the measuring system shown i n Figure C-5. 99 I = -e 0 j * C 2 - e . J H (1/G)} ; R j ^ C i R + 1 l = - e £ G L ^ - " " — R — cr i -e 0/ j*CiR i = -e Q - ) + (jwCjR+l) since G^IO^ from the manufacturer where zi=Cj| R thus e 0 = ^ i z l (1) I f gain, G i s i n f i n i t e , then e=0. A rough estimate of G was made using a 1.5 v o l t battery across a I K r e s i s t o r i n the feedback loop. The input voltage e (=e 0+1.5v.) determined using an oscilloscope was 0.5nrv. This corresponds to G = - e . > - ( - 1 . 5 ) = 3000 e 0.5*10-3 The closed loop DC gain = -G0 = e 0 Go = 1 - e from (2) , 1 y G0 > 1 - 0.0005 1.5 1 > 0 o > 0.9996? Second Amplification Stage> I f the ladder attenuator m u l t i p l i e r = 9, then the input to the second a m p l i f i c a t i o n stage may be expressed as 100 V i = _eo_ (2) 011-1 where n = the shunt number we are on 9 = 3 ± 0 . 0 2 5 $ from Table C-l from Figure C-6B, v i + v o 3W&3 + V2 = 0 RT IT s u b s t i t u t i n g - <^v0 , v 0 ( ^ 3 % + <p)= -v iR 1 X o = -Rj (3) v i <?R0^1 + JWC3R1 j <Q varies from 1 to 0 i n increments of 0.1 and i s set by the boost switch. For no boost, =1 and = -Ri 1 R e ( l + j ^ C 3 R 1 ) = do gain of -R\ R7 30Kjv-- -11 CjRi = 0.33/uf • 330K = 0.11 sec. This i s the s i t u a t i o n f o r normal measurements. In pr a c t i c e , the boost switch i s only used i n searching f o r and i d e n t i f y i n g small peaks such as Rb85. Since v 0 cannot exceed 1.4 v o l t s 101 (the largest voltage the di g i t a l voltmeter can handle), the value of <p must exceed 0 .5 while on shunt 1 . In summary, the output voltage vtf from the measuring system can be expressed as a function of the ion current i as follows i v e = R l i (4) iRsZjSn-lU+.Wc^) <? PERFORMANCE OF M.S.3 Calculations were made on the resolution and peak shape characteristics of M.S.3. These quantities are defined in Figures C-7 and C-8. Experimental measurements on mass spectrograms such as that in Figure C-9 are summarized in Table C-2. The averages for wc and w^  determined experimen-t a l l y agree well with the measured collector and source s l i t widths quoted in Figures C-3 and C-4. Stability problems due to line voltage fluctuations have been a cause for concern in the isotopes lab. Measurements of the noise on the high voltage supply and the magnet current supply were made to see how significant line voltage variations were. It was found that over the time span (about 5 minutes) required for one strontium scan, ^ _1_ (5) AB Al B I < 10000 5000 where B = magnetic f i e l d strength I = magnet current V = accelerating voltage 102 COLLECTOR M e R 2B 2 2V D = dispersion - 2<fR = RfM where M «= mass of ion e = charge of ion Y - accelerating voltage R = radius of path in magnet . B = magnetic f i e l d strength FIGURE C-7» F i r s t order direction focusing mass analyzer. : (after Kollar, i 9 6 0 ) . Define K = wc+wi = R Resolution = J D_ R <JM wc+wi WC+WJ_ = image or ion beam width «= ws+R«.a + misc. w s = source s l i t width w c " « collector s l i t width resolution Then wc = ^ i±£^ K » w i s ( ¥ ) K and A = wc-v;^  wc+wi FIGURE C-81 Mass spectrogram with two peaks representing '. atomic masses M and M+iM (after Kollar, i960) 104 (1) Peak shape« Theo r e t i c a l peak shape i s determined from actual measure-ments of the source e x i t s l i t and the c o l l e c t o r d efining s l i t . ws = 0.010410.0005 = o . 4 8 : t o . 0 5 w c 0.0216+0.0010 J also, wc-ws wc+ws = 0 . 3 5 ± 0 . 0 6 Actual peak shape was determined at various times f o r a strontium spectrum scanning with the magnet current. Date 1974 Number of Measurements w i + wc m W c " W i +2s wC+wi " m Feb. 19 8 0.38+0.03 0.45+0.03 Mar. 3 8 0.37^0.02 0.46+0.02 Mar. 22 7 0.44+0.03 0 . 3 9 ± 0 . 0 3 (2) Resolution! The r e s o l u t i o n of M.S.3 i n the range of the strontium spectrum (masses 84-88) was empi r i c a l l y determined. Measurements were made on downmass scans as well as upmass scans to avoid the influence of hystersis i n the magnet. Date Number of Resolution t 2 s m 1974 Measurements Feb. 19 12 428+33 Mar. 3 12 423±17 Mar. 22 12 393±13 (3) C a l c u l a t i o n of ion beam and c o l l e c t o r s l i t widths» Date 1974 Resolution K=wc+wi (inches) A=w c-W£ w c + w i w c (inches) wi (inches) Feb. 19 428 0.0280 0.45 0.0203 0.0077 Mar. 3 423 0.0284 0.46 0.0207 0.0080 Mar. 22 393 0.0305 0.39 0.0212 0.0093 Average 1 415 0.0290 0.43 0.0207 0.0083 (4) Dispersion from mass 86 to mass 871 D = res o l u t i o n , £M . wc+wi ~ 415 . 1 . 0.0290 = 0.140 i n . M 'Ho' TABLE C-2» Peak shape, r e s o l u t i o n and dispersion of M.S.3 i n the range of the strontium spectrum. 2s r a = two standard deviations of the mean. 105 C s / These numbers are believed to represent the worst possible v a r i a t i o n s i n B and V expected. One should recognize that changes i n the magnetic f i e l d strength (AB) may not exactly r e f l e c t changes i n the magnet current ( A l ) , due to e f f e c t s such as eddy currents i n the magnet. The e f f e c t of the above noise may be considered as follows! From Figure C-7, M R 2B 2 (6) e " 2V Rearranging terms leads to Assuming R = f(V,B), dR =/PR\dV +/£R\dB U W 1<?B/ hence dR = RdV - RdB (7) 2V B The movement M i n the ion beam i n response to the changes dV and dB i s M « 2dR In the worst case of dV and dB r e i n f o r c i n g each other; i . e . , acting i n opposite d i r e c t i o n s , M = R / dV + 2dB) \ V B / From ( 5 ) , M = 12 / 1_ + 1_ ) inches \ 5000 5000 J M = 0.0048 inches 106 One should note that changes i n the l i n e voltage would normally d e f l e c t B and V i n the same d i r e c t i o n , thus leading to p a r t i a l compensation of the two e f f e c t s . In p r a c t i c e , while scanning, one only stays on an in d i v i d u a l peak top f o r twenty seconds. A rough estimate can be made of the worst possible movement i n the ion beam during t h i s time span. Assume a maximum possible v a r i a t i o n of 0.0048 inches i n a f i v e minute period and assume t h i s v a r i a t i o n has smooth fu n c t i o n a l r e l a t i o n s h i p with time, such as, dR = 0.0024 s i n cot It follows that slope = d(dR) = 0.0024 oo cos wt dt = maximum value of 0.0024u? The movement M (=2dR) i s worst i n the twenty second i n t e r v a l within which the slope of dR i s a maximum. Thus, M x 0.0024 • c*> • t = 0.0024 . 2-TT . 1 mih. 5 min. 3 = 0.001 inches Comparing t h i s with a peak top width of 0.0125 inches, one can see that M i s small but not n e g l i g i b l e . D u r i n g the f i n a l s t a g e s of t h i s s t u d y , the w r i t e r s w i t c h e d t o a n a l y s i n g samples on M.S.2. T h i s was e s s e n t i a l l y 10? a p r a c t i c a l d e c i s i o n so t h a t p r o d u c t i o n o f d a t a would not be d e l a y e d u n t i l t he c o m p l e t i o n o f the r e c o n s t r u c t i o n o f M.S.3. I n g e n e r a l , s t r o n t i u m i s o t o p i c a n a l y s e s r u n on M.S.3 f o r t h i s s t u d y were o f p o o r e r q u a l i t y t h a n t h o s e r u n on M.S.2. I t t o o k a g r e a t e r number of scans (and a l s o more t i m e ) t o complete a r u n on M.S.3 such t h a t the a n a l y s i s had a comparable p r e c i s i o n t o the t y p i c a l M.S.2 s t r o n t i u m a n a l y s i s . I n a d d i t i o n , a much g r e a t e r . p e r c e n t a g e o f d a t a was r e j e c t e d from M.S.3 runs t h a n from M.S.2 r u n s . ( C r i t e r i a f o r r e j e c t i o n o f d a t a are d i s c u s s e d i n Appendix H.) C o n t r i b u t i n g f a c t o r s t o t h i s s i t u a t i o n w erei (1) Peak shape c h a r a c t e r i s t i c s were s u p e r i o r on M.S.2 due t o the use o f a 0.040 i n c h c o l l e c t o r s l i t i n s t e a d o f the 0.020 i n c h s l i t used on M.S.3 (2) I n s t a b i l i t y problems a s s o c i a t e d w i t h one o r more s u p p l i e s on M.S.3 were u n s o l v e d a t the time a n a l y s e s were performed. ( 3 ) The n o i s e - l e v e l o f the m e a s u r i n g system on M.S. 3 was h i g h e r t h a n the n o i s e l e v e l on M.S.2. D e s p i t e t h e s e c o n d i t i o n s , good a n a l y t i c a l d a t a was o b t a i n e d . R e p l i c a t e a n a l y s e s o f the s t r o n t i u m c a r b o n a t e s t a n d a r d SRM 9 8 ? are i n e x c e l l e n t agreement as are d u p l i c a t e analyses. of whole r o c k sample 3 8 on M.S.2 and M.S.3 (see Appendix H). 108 APPENDIX D X-RAY FLUORESCENCE METHOD INTRODUCTION C o n c e n t r a t i o n s o f Rb and S r were d e t e r m i n e d by XRF a n a l y s e s u s i n g t h e t e c h n i q u e d e s c r i b e d i n d e t a i l i n Ryan (1973) and B l e n k i n s o p (1972). The method used a t U.B.C. i s s i m i l a r t o t h a t i n use i n o t h e r l a b o r a t o r i e s , f o r example, the U n i v e r s i t y o f A r i z o n a ( L i v i n g s t o n , 1969). T h i s appendix d i s c u s s e s some d e t a i l s o f the method n ot e x p l a i n e d e l s e w h e r e , and d e m o n s t r a t e s t h a t t h e r u b i d i u m and s t r o n t i u m c o n c e n t r a t i o n s and t h e Rb/Sr r a t i o s r e p o r t e d i n t h i s t h e s i s were d e t e r m i n e d w e l l w i t h i n t h e s t a t e d p r e c i s i o n and a c c u r a c y o f the method (Ryan, 1973) o f 3% a t the 95% c o n f i d e n c e l i m i t s , THEORY The method i s based on the f o l l o w i n g e q u a t i o n from R e y n o l d s (1963) and L i v i n g s t o n (1969)« C i = / t t j I j (1) K i where C i = c o n c e n t r a t i o n o f element i i n the sample / ^ i = mass a b s o r p t i o n c o e f f i c i e n t f o r the sample a t t h e wav e l e n g t h o f t h e K - a l p h a f l u o r e s c e n c e peak o f element i I i = i n t e n s i t y o f the f l u o r e s c e n c e peak g e n e r a t e d by element i i n the sample K i = g e n e r a l c o n s t a n t which i n c l u d e s a l l o t h e r f a c t o r s a f f e c t i n g t h e measurement o f C i ( o p e r a t i n g c o n d i t i o n s , e t c . ) / ( i i s a s i m p l e f u n c t i o n o f the c h e m i c a l c o m p o s i t i o n o f the 109 sample and t h e w a v e l e n g t h o f the r a d i a t i o n i n c i d e n t upon the sample. I t s p r e s e n c e i n e q u a t i o n ( 1 ) i s an attempt t o n e u t r a l i z e t h e e f f e c t t h a t t h e c o m p o s i t i o n o f a sample has on I i . I f a s t a n d a r d sample s i s a n a l y z e d w i t h an unknown sample x, t h e n one can show t h a t G i x _ • ^ i x I i x c i s / ^ i s l i s CALCULATION OF /<-Hower ( 1 9 5 9 ) showed t h a t t h e mass a b s o r p t i o n c o e f f i c i e n t of a sample a t a g i v e n w a v e l e n g t h i s p r o p o r t i o n a l t o t h a t a t a n o t h e r w a v e l e n g t h p r o v i d e d t h a t no major element a b s o r p t i o n edges i n t e r v e n e . A c c o r d i n g t o Ryan ( 1 9 7 3 ) t h i s means t h a t f o r any w a v e l e n g t h between 0 . 4 angstroms and 1 , 7 angstroms, the r a t i o o f JUL* v a l u e s f o r any two r o c k samples i s a c o n s t a n t i n d e p e n d e n t o f w a v e l e n g t h . Thus, • ^ • i x ^ A o . 7 3 5 x _ ^ 0 . 7 5 x ( 3 ) / * i s ~ ^ 0 . 7 3 5 s ^ 0 . 7 5 s where M.± = mass a b s o r p t i o n c o e f f i c i e n t a t t h e w a v e l e n g t h o f the K - a l p h a r a d i a t i o n o f the element i one i s a n a l y z i n g f o r c ^ 0 . 7 3 5 = m a s s a b s o r p t i o n c o e f f i c i e n t a t X= 0.735A wh i c h i s th e w a v e l e n g t h o f the Mo K - a l p h a Compton-s c a t t e r e d peak. F o r each sample / ^ m e a s u r e d ) i s d e t e r m i n e d a t t h i s w a v e l e n g t h . „ Mr^^rje = mass a b s o r p t i o n c o e f f i c i e n t a t X = 0 . 7 5 A w h i c h i s th e w a v e l e n g t h a t w h i c h MX c a l c u l a t e d ) i s d e t e r m i n e d (see T a b l e D - l ) To d e t e r m i n e t h e v a l u e o f y C t f o r each sample, t h e e m p i r i c a l 110 r e l a t i o n s h i p (Reynolds„ 1963) between the i n t e n s i t y o f the Mo K - a l p h a C o m p t o n - s c a t t e r e d peak and^/Uo,735 i s u s e d i _ i ~ aC^O.735 *MoKCS t h u s _ I — = alAo.735 = a2/(D.75 = ayUi (^) . iMoKCS where % o K C S = i n t e n s i t y of the Mo K - a l p h a C o m p t o n - s c a t t e r e d peak a t A,=0.735A a,a^ , a 2 = c o n s t a n t s f o l l o w i n g t he c o n d i t i o n s o f Rey n o l d s (1963) and Hower (1959) A gra p h o f M Q ^ ^ v e r s u s l/lMoKCS f o r s e v e r a l chosen s t a n d a r d s o f known / to 1 7 5 v a l u e s w i l l t h u s d e f i n e a s t r a i g h t l i n e o f s l o p e a-2. U s i n g t h i s c a l i b r a t i o n l i n e , the/Uo,75 v a l u e o f an unknown ( p r o p o r t i o n a l t o i t s v a l u e ) may be d e t e r m i n e d , once the q u a n t i t y IjyioKCS measured. The X I Q ^ ^ v a l u e s o f the s t a n d a r d s can be o b t a i n e d e i t h e r by c a l c u l a t i o n , u s i n g p u b l i s h e d t a b l e s o f the /A v a l u e s o f c o n s t i t u t e n t e l e m e n t s , o r by e x p e r i m e n t a l methods. V a l u e s o f /U0.75 u s e d by the w r i t e r are l i s t e d i n Tab l e D-l and were c a l c u l a t e d from the c h e m i c a l a n a l y s e s of s t a n d a r d r o c k s and m i n e r a l s p u b l i s h e d by F l a n a g a n (1973) and R o u b a u l t e t a l . (1970) and t h e t a b l e s o f Ao.75 p u b l i s h e d by J e n k i n s and De V r i e s (1969). The e f f e c t s o f a l l m a j o r elements and C l , F, S, Rb, Ba, S i , L i , and Zn were t a k e n i n t o a c c o u n t . The c a l i b r a t i o n l i n e s were f i t t e d u s i n g the l e a s t - s q u a r e method of York (1969) ( s e e Appendix I ) . Graphs of/{Q.75 E x p e r i m e n t a l C a l c u l a t e d S t a n d a r d Source M a t e r i a l D e t e r m i n a t i o n Ryan (1973) Ryan (1973) B l e n k i n s o p (1972) T h i s s t u d y G-2 USGS g r a n i t e 6.08 5.99 6.04 5.96 GSP-1 USGS g r a n o d i o r i t e 6.76 6.58 6.67 6.56 BCR-1 USGS b a s a l t 9.61 9.43 9.50 9.39 AGV-1 USGS a n d e s i t e 7.41 7.31 7.33 7.29 W-l USGS dia b a s e 9.23 - - 8.92 NBS-70a NBS po t a s s i u m f e l d s p a r - - - 5.73 Mica-Fe CRPG b i o t i t e m i c a - - - 13.11* Mica-Mg CRPG p h l o g o p i t e m i c a - - - 8.47* * Chemical analyses f o r Mica-Fe and Mica-Mg which were used to calculate ^Ao.75 values are not as well known as the chemical analyses f o r the other standards. TABLE D-l» / ^ v a l u e s c a l c u l a t e d a t A.=0.75A which have been used a t U.B.C. f o r v a r i o u s s t a n d a r d s . The e f f e c t o f u s i n g one s e t o f ,0k v a l u e s v e r s u s a n o t h e r changes the a u t h o r ' s r e s u l t s ^-0.4%. Sources o f s t a n d a r d s are USGS - U n i t e d S t a t e s G e o l o g i c a l Survey,^NBS - N a t i o n a l Bureau of S t a n d a r d s , CRPG - Centre de Recherches P e t r o g r a p h i q u e s e t Geochimiques. 112 ( c a l c u l a t e d ) v e r s u s 1 /IMOKCS f o r s t a n d a r d s a n a l y z e d by the w r i t e r are shown i n F i g u r e s D-l and D -2 . D a t a p o i n t s were w e i g h t e d assuming an a r b i t r a r i l y c hosen c o n s t a n t p e r c e n t a g e e r r o r i n t h e / t o , 7 5 ( c a l c u l a t e d ) and 1 /IMOKCS v a l u e s ; i . e . , p o i n t s i n F i g u r e s D-l and D-2 are w e i g h t e d p r o g r e s s i v e l y l e s s from l e f t t o r i g h t . The c a l i b r a t i o n l i n e s were c o n s t r a i n e d t o pass n e a r t h e o r i g i n by i n c l u d i n g (0 ,0) w i t h a h i g h w e i g h t i n g f u n c t i o n as one of the p o i n t s t o whi c h the l i n e s were f i t t e d . The c h o i c e o f wh i c h s t a n d a r d s t o use f o r the c a l i b r a t i o n l i n e was made a f t e r c o n s i d e r i n g t h r e e f a c t o r s : (1) t h e range o f Rb and S r c o n c e n t r a t i o n s o f v a r i o u s unknowns, (2) t h e a c c u r a c y w i t h w h i c h the Rb and S r c o n c e n t r a t i o n s o f the v a r i o u s s t a n d a r d s are known, (3) t h e d e s i r e t o keep the w r i t e r ' s r e s u l t s on a com p a r a t i v e b a s i s t o the r e s u l t s o f B l e n k i n s o p (1972) . F a i r b a i r n and H u r l e y (1971) i n v e s t i g a t e d the r e l a t i o n -s h i p o f jm v e r s u s 1 /IMOKCS a n d - r e a c h e d the c o n c l u s i o n t h a t i t was l i n e a r o n l y o v e r s e l e c t e d segments o f the p l o t . F o r the r a n g e s o f whole r o c k unknowns ( g r a n i t e , g r a n o d i o r i t e , and q u a r t z d i o r i t e c o m p o s i t i o n s ) and p o t a s s i u m f e l d s p a r unknowns c o n s i d e r e d i n t h i s s t u d y , the /tc- v e r s u s l / l ^ o K C S r e l a t i o n s h i p i s q u i t e l i n e a r as the quoted u n c e r t a i n t i e s i n the s l o p e s o f the l i n e s i n F i g u r e s D - l and D-2 d e m o n s t r a t e . F o r the range o f b i o t i t e unknowns t h i s l i n e a r r e l a t i o n s h i p i s not as c l e a r . a> +> rH o rH ro o 13.-12 -11 -10 9 -8 -7 -6 -5 4 December 8, 1973 d a t a 90 unknowns 35 s t a n d a r d s M ica-Fe ® .range o f whole r o c k unknowns BCR-1 range o f p o t a s s i u m f e l d s p a r unknow: W-l l i c a - M g range o f • • • b i o t i t e - * unknowns AGV-1 TJSP-1 s l o p e o f c a l i b r a t i o n l i n e = 107400+1300 i n t e r c e p t = 0.152610.1418 0."4 0 .5 0.6 0.7 0.8 0.9 1.0 I n v e r s e o f Compton s c a t t e r (XI 0 ~ ^ ) 1.1 1.2 FIGURE D - l t P l o t of / t o . 7 5 \ c a l c u l a t e d ) v e r s u s l/lMoKCS f o r s t a n d a r d s r u n on Dec. 8 , 1973. Doubly c i r c l e d d a t a p o i n t s i n d i c a t e w h i c h s t a n d a r d s were used t o d e f i n e the c a l i b r a t i o n l i n e . The ranges w i t h i n w h i c h v a r i o u s unknowns f e l l are shown. U n c e r t a i n t i e s q u o t e d are one s t a n d a r d d e v i a t i o n . CO 4-> CC H O rH o o 13 -12 -11 -10 9 -8 -7 -6 -5 F e b r u a r y 9, 1974 d a t a 45 unknowns 3 0 s t a n d a r d s ca-Fe range o f whole 'rock unknowns -* ge o f po t a s s i u r j i f e l d s p a r unknowns BCR-1 range.. o f k b i o t i t e - * unknowns W-l Mica-Mg 'G- 2 'NBS - 7 0 a s l o p e o f c a l i b r a t i o n l i n e = i n t e r c e p t = 1 2 7 0 0 0 1 1 6 0 0 0 . 1 9 2 7 + 0 . 1 4 0 5 0 ^ 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 . 0 I n v e r s e o f Compton s c a t t e r (-Y10-4) 1.1 1.2 FIGURE D - 2 i P l o t o f AQ.75(calculated) v e r s u s l/lMoKCS f o r s t a n d a r d s r u n on Feb. 9. 1974. Doubly c i r c l e d d a t a p o i n t s i n d i c a t e w hich s t a n d a r d s were used t o d e f i n e t h e c a l i b r a t i o n l i n e . The ranges w i t h i n w h i c h v a r i o u s unknowns f e l l are shown. U n c e r t a i n t i e s quoted are one s t a n d a r d d e v i a t i o n . 115 (Mica-Fe and Mica-Mg s t a n d a r d s p l o t s l i g h t l y o f f t h e c a l i b r a t i o n l i n e s . ) CALCULATION OF RB AND SR CONCENTRATIONS Rb and S r c o n c e n t r a t i o n s are c a l c u l a t e d from the XRF d a t a i n the f o l l o w i n g sequence t (a) A l l c o u n t s are c o r r e c t e d f o r the dead-time o f the c o u n t e r , (b) Chosen s t a n d a r d s are used t o d e f i n e a / i ^ . y ^ v e r s u s l/l-MoKCS c a l i b r a t i o n l i n e . (c) /^o,75 v a l u e s f ° r t h e unknowns are c a l c u l a t e d u s i n g t h e i r measured l/lr>ioKCS v a l u e s and t h e c a l i b r a t i o n l i n e i n ( b ) . (d) I n t e n s i t i e s o f Rb and S r peaks are c o r r e c t e d f o r background. (e) I n t e n s i t i e s o f c o r r e c t e d Rb and S r peaks f o r chosen s t a n d a r d s are m u l t i p l i e d by t h e i r r e s p e c t i v e y U o „ 7 5 ( c a l c u l a t e d ) v a l u e s t o g i v e a d j u s t e d peak i n t e n s i t i e s . ( f ) A d j u s t e d peak i n t e n s i t i e s c a l c u l a t e d i n (e) are p l o t t e d a g a i n s t known Rb and Sr c o n c e n t r a t i o n s t o dete r m i n e Rb and S r c a l i b r a t i o n l i n e s . ( T h i s i s done f o l l o w i n g t he same p r o c e d u r e d e s c r i b e d p r e v i o u s l y f o r the v e r s u s 1/IMOKCS c a l i b r a t i o n l i n e ) . (g) V a l u e s of JHQ 73. f o r the unknowns d e t e r m i n e d i n ( c ) are loo H December 8, 1973 d a t a 90 unknowns 35 s t a n d a r d s i o > 5 -P •H W C CO -p •H cd ft T J 0) -P to 80 i 60 H 40 H 20 range of potassium^ ' f e l d s p a r unknowns range o f vhole r o c k unknpwns range o f b i o t i t e unknowns except. Mica-Mg, M i c a - F e , and G6-2 s l o p e = 0.01024+0.00004 i n t e r c e p t = 0.00016+0.00898 100 200 300 400 500 600 Rb c o n c e n t r a t i o n (ppm) 700 800 900 FIGURE D-3 8 Rb c a l i b r a t i o n l i n e used by the w r i t e r f o r Dec. 8, 1973 d a t a . The range s ~ o f Rb c o n c e n t r a t i o n o f t h e v a r i o u s unknowns are i n d i c a t e d . U n c e r t a i n t i e s quoted are one s t a n d a r d d e v i a t i o n . F e b r u a r y 9» 1 9 7 4 d a t a I o >> -p •H Ui CD •¥> •H Cd CD ft T3 CO •P CO •rs < looH 8 0 A 6 0 4o 2 0 0 range o f whole r o c k unknowns 4 5 unknowns 3 0 s t a n d a r d s range o f p o t a s s i u m ' f e l d s p a r unknowns N B S - 7 0 a GSP -1 ^ range o f b i o t i t e unknowns e x c e p t W - l BCR-1 Mica-Mg, M i c a - F e , and G6 - 2 s l o p e = 0 . 0 0 8 4 5 + 0 . 0 0 0 0 3 i n t e r c e p t = 0 . 0 0 0 1 5 * 0 . 0 1 1 3 0 1 0 0 2 0 0 3 0 0 400 5 0 0 6 0 0 Rb c o n c e n t r a t i o n (ppm) 7 0 0 8 0 0 9 0 0 FIGURE D-4» Rb c a l i b r a t i o n l i n e used by the w r i t e r f o r Feb. 9»1974 d a t a . The range s of Rb c o n c e n t r a t i o n o f the v a r i o u s unknowns are i n d i c a t e d . U n c e r t a i n t i e s quoted are one s t a n d a r d d e v i a t i o n . J o > 5 " P •H W -P C •H Cd CD ft Tf CO -p CO T 3 100 December 8, 1973 d a t a 90 unknowns 35 s t a n d a r d s CO s l o p e = 0.00825+0.00002 i n t e r c e p t = 0 .00003+0.01140 300 400 500 S r c o n c e n t r a t i o n (ppm) 600 700 800 FIGURE D - 5 t quoted are one s t a n d a r d d e v i a t i o n . i n d i c a t e d . U n c e r t a i n t i e s 0 -F 1 1 1 1 1 1 1 r o 100 200 300 4oo 500 6oo 700 800 S r c o n c e n t r a t i o n (ppm) FIGURE D-61 S r c a l i b r a t i o n l i n e used by the w r i t e r f o r Feb. 9, 1974 d a t a . The ranges o f Sr c o n c e n t r a t i o n o f the v a r i o u s unknowns are i n d i c a t e d . U n c e r t a i n t i e s quoted are one s t a n d a r d d e v i a t i o n . 1 2 0 multiplied by their respective Rb and Sr corrected peak intensities to give adjusted peak intensities, (h) Using the adjusted Rb and Sr peak intensities determined in (g) and the calibration lines determined in (f), the Rb and Sr concentrations of the unknowns are determined. The Rb and Sr calibration lines used by the writer are shown in Figures D-3 to D-6. The Rb and Sr concentration results determined for various unknov/ns are listed in Appendix H. There is a recognized problem in determining Rb and Sr concentrations for biotites because of their very high Rb and very low Sr concentrations. To provide some control over the ranges of Rb and Sr concentration indicated by biotite unknowns, NBS-70a was used as a primary calibration standard and Mica-Fe and Mica-Mg were run as checks. Also, the Sr concentrations of six biotites were determined by the isotopic dilution method and this provided an independent means of assessing the accuracy of the XRF results. ACCURACY OF THE METHOD Table D-2 is a compilation from the recent literature of the best determined Rb and Sr concentrations for the eight standards used in this study. Table D-3 lists the concentration and absorbance values used by the writer as Rb(ppm) Sr(ppm) Rb/Sr S t a n d a r d Source Weight R a t i o a 171+1.8* 4 8 0 * 5 0 . 356310 .0075 G-2 b 1 6 7 . 6 4 7 4 . 8 0 . 3 5 3 0 c 168 479 0 . 3 5 0 7 d 1 6 9 . 3 ± 0 . 7 * * 4 7 6 . 3 ± 1 . 3 0.3554+0.0024 a 2 5 3 ± 1 . 2 23512 .5 1 .077+0.017 GSP-1 b 2 5 4 . 5 2 3 3 . 2 1 .091 c 254 233 1 . 0 9 0 d 2 5 4 . 7 ± 0 . 7 2 3 3 . 1 + 0 . 4 1 . 0 9 3 + 0 . 0 0 3 a 6 7 . 7 + 0 . 8 663+7 0 . 1 0 2 1 + 0 . 0 0 2 3 AGV-1 b 6 6 . 6 656.5 0.1014 c 6 7 . 0 6 5 1 0 . 1 0 2 0 d 6 7 . 1 + 0 . 5 662+1.2 0.1014+ 0 . 0 0 0 9 a 4 8 . 2 + 0 . 4 331+2 0 . 1 4 5 6 + 0 . 0 0 2 1 BCR-1 b 4 6 . 9 3 3 1 . 5 0 . 1 4 1 5 c 46 . 6 330 0.1412 d 4 7 . 3 * 0 . 2 3 2 2 . I+O . 6 0.1424+ 0 . 0 0 0 9 * U n c e r t a i n t i e s q u o t e d f o r s o u r c e a are $ e r r o r . ** U n c e r t a i n t i e s q u o t e d f o r s o u r c e d are two s t a n d a r d d e v i a t i o n s o f t h e mean. TABLE D-2> C o m p i l a t i o n from the l i t e r a t u r e o f b e s t d e t e r m i n e d Rb and S r c o n c e n t r a t i o n s f o r the e i g h t s t a n d a r d s used i n t h i s s t u d y . Sources of i n f o r m a t i o n are as f o l l o w s ! a F a i r b a i r n and H u r l e y (1971) b De L a e t e r and Abercrombie (1970) c F l a n a g a n (1973) d P a n k h u r s t and 0'Nions ( 1973) e Compston e t . a l , ( 1969) f R o u b a u l t e t . a l . ( 1970) 122 TABLE D-2 ( c o n t . Rb(ppm) Sr(ppm) Rb/Sr S t a n d a r d Source Weight R a t i o a 531+1 66.5+0.4 7.985+0.063 NBS-?Oa b 523.4 66.4 7.883 d 529.8+1.5 65.4+0.1 8.101+0.035 e 530 XR @ t 6 6 . 2 8.006 ID» 6 5 . 1 8.141 W-l b 21.5 189 . 3 O . I I 3 6 c 21.0 190 0.1105 Mica-Mg c 1250 25 50.00 f 1318®® 26.4®® 49.92 Mica-Fe c 2300 6 383 f 2 2 3 7 @ @ 5.6®® 399 @ XR = X - r a y , ID = i s o t o p e d i l u t i o n @@ averages o f two mass s p e c t r o m e t e r d e t e r m i n a t i o n s i n p u t d a t a t o t h e U.B.C. computer program w h i c h d e t e r m i n e s th e v a r i o u s c a l i b r a t i o n l i n e s ( F i g u r e s D - l t o D - 6 ) . F o r t h e sake o f c o n s i s t e n c y , t he same Rb and S r i n p u t v a l u e s as B l e n k i n s o p (1972) were us e d , as the w r i t e r was s t u d y i n g the same s u i t e o f r o c k s . Use o f o t h e r p o s s i b l e i n p u t v a l u e s changes t h e r e s u l t s <1%. The r e s u l t s of r u n n i n g r e p l i c a t e a n a l y s e s o f s t a n d a r d s as unknowns are l i s t e d i n T a b l e D -4 . The mean Rb/Sr w e i g h t r a t i o s d e t e r m i n e d f o r G -2 , GSP - 1 , 123 S t a n d a r d Rb(ppm) Sr(ppm) R e l a t i v e Absorbance Mo.75 Rb/Sr Weight R a t i o G-2 169 480 6 . 0 8 0 . 3 5 2 1 GSP-1 255 235 6 . 7 6 1 . 0 8 5 AGV-1 67.O 663 7.41 0.1011 BCR-1 48 .2 331 9 . 3 9 0 . 1 4 5 6 NBS - 7 0 a 530 6 5 . 4 5 . 7 3 8 . 1 0 3 TABLE D-3» I n p u t d a t a t o the U.B.C. computer program which d e t e r m i n e s the v a r i o u s c a l i b r a t i o n l i n e s ( F i g u r e s D - l t o D - 6 ) . AGV - 1 , BCR-1 and NBS - 7 0 a show d i s c r e p a n c i e s o f from - l . ? 8 % t o +1.40$ (mean d e v i a t i o n o f 1.02%) from t h e most r e c e n t and p r o b a b l y b e s t r e p o r t e d r a t i o s i n t h e s e r o c k s ( P a n k h u r s t and 0'Nions, 1 9 7 3 ) . V a l u e s f o r Mica-Mg and W-l show s i m i l a r d i s c r e p a n c i e s from t h e i r a c c e p t e d Rb/Sr r a t i o s . Mica-Fe i s the e x c e p t i o n because o f the u n c e r t a i n t y i n d e t e r m i n i n g i t s e x t r e m e l y low c o n c e n t r a t i o n o f S r . Comparison o f XRF S r r e s u l t s w i t h M.S.3 s p i k e d S r a n a l y s e s f o r s i x b i o t i t e unknowns i s shown i n Appendix H. D i s c r e p a n c i e s v a r y from - 2 . 8 2 % t o +6.70% w i t h a mean d e v i a t i o n o f 2,14% (Agreement between t h e two methods i s w e l l w i t h i n 3% f o r f i v e out o f the s i x s a m p l e s ) . S t a n d a r d G-2 GSP-1 AG V - l BCR-1 NBS-70a W-l Mica-Mg M i c a - F e N 7 4 12 5 3 2 4 2 10 2 1 3 3 3 Date 1 2 1 2 1 2 1 2 1 2 1 2 1 2 Rb(ppm) 169.0+0.5 167.0+0.3 255.9+0.3 253.7+0.8 66.2+0.4 65.8+0.2 48.0+0.2 47.9+1.3 533.5+1.6 21.7+0.1 21.3 136718 1374+4 2279+13 2307+8 Sr(ppm) 4 7 6 . 7 + 2 . 1 4 7 8 . 5 + 0 . 7 2 3 2 . 3 I 0 . 6 2 3 2 . 4 + 1 . 0 6 6 1 . 3 + 3 . 4 664.6+8.0 3 3 2 . 2 + 1 . 9 3 3 2 . 8 + 3 . 4 6 5 . 5 + 0 . 2 1 9 0 . 4 + 1 . 8 1 9 0 . 6 26.5+0.1 2 7 . 4 + 0 . 2 0 . 8 + 0 . 6 2 . 0 + 1 . 1 R e l a t i v e Absorbance Ao„75 5 . 9 6 0 + 0 . 0 1 5 5 . 9 3 4 + 0 . 0 1 1 6 . 5 2 4 I 0 . 0 0 9 6 . 5 2 6 + 0 . 0 1 6 7 . 2 6 0 + 0 . 0 4 5 7 . 2 6 3 + 0 . 0 2 5 9 . 4 o o+o . o 4 5 9 . 3 8 3 ± 0 . 0 5 3 5 . 7 6 2 + 0 . 0 1 3 8 . 9 9 7 + 0 . 0 3 0 8 . 9 4 7 8 . 3 2 5 i o . o 4 7 8 . 4 0 9 + 0 . 0 1 6 12.76to.08 1 2 . 9 7 + 0 . 0 2 Rb/Sr Weight R a t i o 0.354710.0013 0.3490+0.0008 1.101+0.003 1.092+0.007 0 .1001+0.0004 0.0991+0.0015 0.1446+0.0013 0.1441+0.0024 8.14810.026 0.1137+0.0006 0.1118 51.55+0.57 50.14+0.29 4211+3536 1479+1095 * N = the number of measurements 1 = Dec. 8 , 1973 data; 2 = Feb. 9 , 1974 data ™ ^ i n T a b l Y D ' - ^ ^ ^ - i n g the input values mean. uncertainties quoted are two standard deviations of the 125 PRECISION OF THE METHOD F i g u r e D-7 i s a p l o t o f Rb and S r c o n c e n t r a t i o n o f s t a n d a r d s v e r s u s p o p u l a t i o n s t a n d a r d d e v i a t i o n f o r the d a t a i n T a b l e D-4 and demonstrates t h a t the normal p r e c i s i o n i s w e l l w i t h i n t h e q u o t e d v a l u e o f 1.5$ at the one s t a n d a r d d e v i a t i o n l e v e l . Ryan (1973) m e n t i o n s 40 ppm as the sample c o n c e n t r a t i o n below w h i c h th e p r e c i s i o n b e g i n s t o d e t e r i o r a t e . The w r i t e r g e n e r a l l y a g r e e s w i t h t h i s s t a t e m e n t but acknowledges t h a t c o n c e n t r a t i o n r e s u l t s below 40 ppm may be used p r o v i d e d c a r e i s t a k e n ( f o r example by r e p l i c a t e measurements) t o ensure the q u a l i t y o f the d a t a . I n t o t a l , about 200 XRF Rb and S r c o n c e n t r a t i o n measurements were made o f v a r i o u s s t a n d a r d s and unknowns. Of t h e s e , a l a r g e number were r e p l i c a t e measurements. I n o r d e r t o c a l c u l a t e e s t i m a t e s o f the p r e c i s i o n o f the d a t a , the w r i t e r f o l l o w e d t h e method o f Youden (1951) o f p o o l i n g s t a t i s t i c a l i n f o r m a t i o n f u r n i s h e d by a group o f s h o r t s e t s o f u n e q u a l s i z e s . T h i s p r o c e d u r e i s d e s c r i b e d b r i e f l y i n Appendix I and the p e r t i n e n t r e s u l t s are shown i n T a b l e D -5 . A l l the e s t i m a t e s o f p r e c i s i o n are w i t h i n t h e q u o t e d v a l u e o f 1.5$ e x c e p t f o r the r e s u l t s c i r c l e d . I n f a c t , the e s t i m a t e d p r e c i s i o n o f Rb/Sr w e i g h t r a t i o s f o r the whole r o c k and p o t a s s i u m f e l d s p a r samples i s b e t t e r by about a f a c t o r o f two o v e r the q u o t e d v a l u e . The sou r c e o f the i n d i c a t e d low p r e c i s i o n e s t i m a t e s can be t r a c e d back t o the p r oblem o f me a s u r i n g th e low S r c o n c e n t r a t i o n s o f b i o t i t e samples. S r 6 region where $ •error at Is l e v e l i s >U5fo '12. a3 >2. 10 Legend © Dec. 8 , 1973 data o Feb. 9 , 1974 data ® Sr measurement o Rb measurement 0 4°PP m 1 0 0 200 —1 1 1 i — 300 400 500 600 Concentration (ppm) 700 800 900 FIGURE D-7> Plot of Rb and Sr concentration versus standard deviation f o r the data i n Table D-4. The number beside each data point indicates the number of measurements used to determine the point. Group o f d a t a c o n s i d e r e d No. o f s e t s o f r e p l i c a t e measurements E s t i m a t e d % e r r o r i n S r c o n c e n t r a t i o n d a t a E s t i m a t e d % e r r o r * i n Rb c o n c e n t r a t i o n d a t a E s t i m a t e d % e r r o r * i n Rb/Sr weight r a t i o s whole r o c k samples 14 0.36 0.80 0.80 p o t a s s i u m f e l d s p a r samples 7 1.32 1.35 0.69 b i o t i t e samples 20 © 1.04 a l l above samples 41 1.07 (2^08) s t a n d a r d s r u n as unknowns 10 0.48 0.47 0.56 * % e r r o r a t the one s t a n d a r d d e v i a t i o n l e v e l as c a l c u l a t e d by e q u a t i o n ( 2 ) , Appendix I TABLE D-5» P r e c i s i o n o f XRF d a t a as e s t i m a t e d by Youden's (1951) method o f p o o l i n g i n f o r m a t i o n from many s m a l l s e t s o f u n e q u a l s i z e s . 128 c o n c e n t r a t i o n s i n b i o t i t e s ranged from 10.7 ppm t o 161 ppm w i t h a median o f 27 ppm; i . e . , most b i o t i t e s had S r c o n c e n t r a t i o n s l e s s t h a n 40 ppm. C a r e f u l a n a l y s i s and r e p l i c a t e measurements are the o n l y ways t o combat t h i s p r o b l e m . The w r i t e r recommends c o m p a r i s o n w i t h mass s p e c t r o m e t e r s p i k e d S r a n a l y s e s as w e l l . I t i s w o r t h n o t i n g ( B l e n k i n s o p , 1972) t h a t the quoted u n c e r t a i n t y o f 3$ a t the 95$ c o n f i d e n c e l e v e l f o r the XRF r e s u l t s and t h e u n c e r t a i n t y o f about 0.04$ (see Appendix H) f o r the i s o t o p i c a n a l y s e s make comparable c o n t r i b u t i o n s t o the age u n c e r t a i n t y ( i . e . , t o the e r r o r i n the s l o p e of the i s o c h r o n ) . 129 APPENDIX E RB-SR METHOD The f o l l o w i n g c o n s t a n t s and e q u a t i o n s were used d u r i n g the cour s e o f t h i s s t u d y i (1.) Abundances o f i s o t o p e s t Rubidium Rb85 = 7 2 . 1 6 5 4+0 . 0 1 3 2 % ( C a t a n z a r o , 1969) R b 8 7 = 2 7 . 8 3 4 6+0 . 0 1 3 2 % ' Common S t r o n t i u m Sr84 = O.56 % Sr86 = 9 . 8 6 % ( C h a r t o f the S r 8 7 = 7.02 % N u c l i d e s , 1 9 6 6 ) Sr88 = 82 .56% From t h e above d a t a the f o l l o w i n g c o n s t a n t r a t i o s were u s e d i Rb85/Rb87 = 2.5 9 2 6 5 ±0. 00170% Sr86/Sr88 = 0.1194 Sr84/Sr86 = 0 . 0 5 6 8 Sr87/Sr86 f o r common s t r o n t i u m = 0.7120 (2.) Atomic w e i g h t s o f the i s o t o p e s : (Harvey, 1 9 6 9 ) Rb85 = 84.911800 t 0 .000005 Rb87 = 86.909186 + 0 .000003 Rb (based on above abundances) = 8 5 . 4 6 7 7 6 + 0 . 0 0 0 2 6 Sr84 = 83.91343 + 0.000004 Sr86 = 85.909285 + 0 .000005 Sr87 = 86.908892 t 0.000004 Sr88 = 87.905641 + 0 .000006 Common S r (based on above abundances) = 8 7 . 6 1 7 1 3 0 ( 3 . ) Rubidium c o r r e c t i o n ; ( Sr87 \ measured / 8? \ measured / A ^ - l ' ) unnormalized = — unnormalized • J — ; Sr86 / Rb-corrected \ 86 / r a t i o I A l , r a t i o (8? peak height • shunt f a c t o r ) „ where A 1 = — — ~ • 2 . 5 9 3 ( 8 5 peak height • shunt f a c t o r ) and shunt f a c t o r i 3 ( s h u n t n u m b e r " D (4.) N o r m a l i z a t i o n ( f r a c t i o n a t i o n c o r r e c t i o n ) ; This i s always done a f t e r c o r r e c t i n g the measured 8 7 / 8 6 r a t i o f o r any Rb present. fSr87 \ measured / S r 8 7 \ measured I normalized = I ) unnormalized • K S r 8 6 / r a t i o \ S r 8 6 / r a t i o where K * 1 f 0 - 1 1 ^ + ( S r 8 6 / S r 8 8 ) T n e a g u r e d ? 2 L 0.1194 J ( 5 . ) C a l c u l a t i o n of Rb87/Sr86 r a t i o t Rb87 Sr86 = { 2 . 6 9 2 9 5 + ( 0 . 2 8 3 0 3 9 - A)j- • B where A = (Sr87/Sr86) measured normalized r a t i o determined by mass spectrometry B = (Rb/Sr) weight r a t i o determined by the x-ray fluorescence method ( 6 . ) Sr84 spike equations 1 S76 = M?6 + (M76-T76) « (S46-M46) (M46-T46) Sr conce i n ppm T i t r a t i o n = ( — ^ ^ ^ 4 ^ ^ 8 2 6 . 8 9 + ( 8 6 . 9 0 9 • S?6 )| 131 where S,T,M denote sample S, t r a c e r T and m i x t u r e I.I ( o f S and T) r e s p e c t i v e l y 6 4 , 4 6 t ? 6 , 8 6 denote the n o r m a l i z e d r a t i o s S r 8 6 / 3 r 8 4 , Sr84/Sr86, Sr87/Sr86 and Sr88/Sr86 r e s p e c t i v e l y In o r d e r t o a p p l y the above two e q u a t i o n s an i t e r a t i v e scheme was used t o n o r m a l i z e the measured r a t i o s M46, M?6, M86. R u s s e l l ( p e r s o n a l communication, 1974) has s i n c e d e v e l o p e d a s o l u t i o n i n c l o s e d form f o r e a s i e r r e d u c t i o n o f s p i k e d S r a n a l y s e s . (7.) A v a l u e o f 4 . 7 A - 1 0 1 0 yr. was used as t h e h a l f - l i f e o f the Rb-Sr decay scheme. The accompanying decay c o n s t a n t A- = 1 . 4? * 1 0 ~ n / y r . 13? APPENDIX F PROGRAM LISTING SR12 * STRONTIUM ISOTOPE PROGRAM VERSION 15/07/71 * LAST MODIFICATION DECEMBER 18 , 1973. B.D.BUSS ELL. * MARCH 26, 1974. R.D.RUSSELL. * APRIL 2, 1974. R.D.RUSSELL. ORG * + X' 1000 ' B IN I T THIS IS THE I N I T I A L ENTRY B CH2CKSW THIS IS THE UPDATE ENTRY RESTART B SUPERVIS THIS IS THE INTERRUPT ENTRY SPACE PRELIM LHI 15,SUPERVIS STH 15,RESTART+2 LH 11,T TYD SR LPSW * + 4 DC X'40 00' DC A(* + 2) BAL 15,DISPL ZERO DISPLAY DC A (ZERO) LHI 1 1 # X " t 1 F 0 ' RESET BAL INSTRUCTION STH 14,FCALC L H I 12,4 I N I T I A L I Z E SOME COUNTERS STH 12,L4 LHI 1 2, Ii ' 2 0 * STH 12,L2 LM 14,LIST1 BAL 10,OUPT CALL TO SET UP PRINT SPACE LH 15,12(11) WAIT FOR COMPLETION OF PRINT B M Z *-4 LHI 13,MAINS AVE LHI 1 4,L 4 + 2 BAL 15,INPT GET REPLY DC A(BTEMP) L4 DC H«4« LH 5,BT EKP CLHI 5 , C « Y E ' IS i r «YE« ? BN E ASKID LHI 5,X'4200» SUPPRESS NORMALIZATION IF SAMPLE * SPIKED STH 5,FCALC LHI 4,?ROUT2+1 JUST LF AND CR STH 4,PLlST3+2 ASKID LM 14,LIST2 BAL 10,ODPT CALL TO SET UP PRINT LH 15,12(11) WAIT FOR COMPLETION OF PRINT BNZ *-4 133 A p p e n d i x F P r o g r a m L i s t i n y LHI 1U,L2+2 BAL 15,1'JPT GET IT DC A(ID+1) L2 DC H'20« LK 14,LIST3 BAL 10,OUPT CALL TO SET UP PRINT XHR 12,12 ZERO SOME VARIABLES STH 12,CHECKPT STH 12,HPTS STH 12 FSW STH 12,PTR1 STH 12,PTH2 STH 12,PTR3 STH 12,NSCAN STH 12,TOTAL LHI 13,CRUDE L H I 14,2 LHI 15,BHU+8 CLEAR WORKING AREA STH 12,0(13) ZERO BUFFER BXLE 13,* - a L H I 12,X*2020' BLANK RATIO OUTPUT AREA LHI 13,RAT 101 -U L H I 15,PROUT2-2 STH 12,0 (13) BXLE 13,*-4 LHI 12,X'U200* I N I T I A L I Z E SWITCHES STH 12,CNTRL STH 12,BASES STH 12,HAXKIJ.M. LEi 0,12(11) BNZ *-4 LHI 0,ROUTINE STH 0,RESTART + 2 TO TERMINATE RESTART B SUPERVIS SPACE 2 ZERO DC 3X'3030» KESSO DC X'BDOAOAOA' D c C i * * * 3TRo;;riUE'i PROGRAM SR12 *** « MESS 12 DC X ' b D O A ' DC C I S SAMPLE SPIKED* DC X*8D0A8D3F* MESS3 DC X'BDOA' DC C P L EASE ENTER I . D . • DC X'8D0A8D3F* HESS 4 DC X ' dDOA * DC C THANKS. 5 DC X"*927UD20* DC C A L L READY 1 DC X ' BDOAOAOA* DS OH A p p e n d i x F Program Listing BT3MP DS 6C ID DC 6X'OG00OOO0 i ID LSD EQU *-2 L 1ST 1 DC A (MESSQ) DC A (MESS3-1) LIST2 DC A (MESS3) DC A (MESS4- 1) LIST3 DC A (MESS4) DC A (BTEMP- 1) SPACE 2 IN IT LH 1,TT YDSR LH 1 ,16 (1) ADDRESS OF OUTPUT DEVICE STH 1 ,INPT+20 TO SET INPUT DEVICE OC 1,HIDE SEP TO READ MODE • R DR 1,0 DUMMY READ TO CLEAR INTERFACE INIT1 LHI 0,SU PSRVIS STIi 0,RESTART+2 SET TO DISREGARD NEXT INTERRUPT BR 15 RETURN TO SUPERVISOR SPACE CH SCKSW LH 5,TT Y DS R I. H 5, 16(5) ADDRESS OF TELETYPE SSR 5,0 BTC 1,INIT1 TO PARK THE DSR BFCR 4,15 RETURN TO SUPERVISOR I F NOT 'BREAK XHR 0,0 STH 0 ,SW CLEAR ALL SWITCH BITS LHI 0,PR ELIM STH 0,REST ART+ 2 RESET TO I N I T I A L I Z E AGAIN BR 15 RETURN TO SUPERVISOR TTYDS R DC X« 04 FA * USING TT2 SPACE SUPER VIS LPS W * + 4 DC X '0000' TO DISABLE INTERRUPTS DC X '0084 • SPACE 8 *********************************************** SWITCH BIT CONVENTION: 0 2 4 6 8 10 12 14 •EOS' • C A L C : N T R Y ENTRY MISSING BASS LINE 1 3 5 7 9 1 1 13 15 'FRACT' ENTRY •PEAK* ENTRY 'PEAK' TROUBLE M A X T A B L E OVERFLOW S H U N T CHANGE OPERATOR REJECT BUTTON SCAN CHANGE * J j c * * * * * * * ^ * * * * * * * * * * * * ****************** *********************** EJECT *************************************************************** * * * THIS IS THE MAIN LINE PROGRAM *ROUTINE* * 135 Appendix F Program L i s t i n g ********************************* SPACE 1 ROUTINE LH 1, NPTS INCREMENT RAW POINT COUNTER A HI 1,1 STH 1,NPTS L H I 13,MAINSAVE LHI 14,*+12 BAL 1 5 , R EA D RBI N DS H DVM READING (BINARY) RSW DS H SCANB EQU *-1 LB 6,SCANB GET SCAN BYTE LH 5 , R BI N GET NEW POINT NOP 5, 1 TO KEEP ONE GUARD BITS LH 4 ,SW PREPARE TO ADJUST SW CLHI 1,2 BNL * + 12 BRANCH NOT FIRST POINT OHI 4,X«0003» BOTH BI T S ! B FLAG CL H 6,LAST BE CHECK LHR 7,6 XH 7,LAST N HI 7,X« 0007« MASK FOR SHUNT BZ * + 8 BRANCH NO SHUNT CHANGE OHI 4,X« C001 « LHR 7,6 XH 7,LA ST NHI 7,X'0030« MASK FOR DIRECTION BZ * + 8 OHI 4 ,X'0002« FLAG STH 6,LA ST STORE SCAN BYTE STH 1,RESET STORE NO. OF RAW POINTS STH 4 , SW :RECK SH 1 , RESET CLHI 1,H'6« 0 K TO RESET SW ? BL *+ 16 NO, BRANCH LH 4, SW YES, RESET SW NHI 4 , X' F F F C STH 4, SW BAL 15,C NT RL GO TO SCAN RATE CONTROL ROUTINE SSR 3,0 I S DVM OVER-RANGE ? BFC 4 ,* + 8 NO, BRANCH A HI 5,H« 10000 ' YES, ADD 10000 LH K 1 ,5 TO XMIT POINT TO FILTER BAL 10,FILTER GO TO FILTER CALLING ROUTINE LHI 13 , MAINS AVE STH 1 ,FILPT STORE FILTERED POINT LHI 14 ,* + 12 RSPURN 1 Appenf 1 i x F Program L i s t i n g BAL 15 ,SIBTOD CONVERT TO DECIMAL DC A ( F I L P T ) DC A ( BU F F 1) LH 4 ,SW IS SW ON ? N HI 4,X'0 00 1» BZ * + 8 MO, BRANCH OHI 6,X'0080' FLAG SCAN BYTE TO INDICATE SW ON BAL 10,SWITCH READ ROTARY SWITCH FOR DISPLAY OUTPUT LH 5,FILPT SPAC E 1 THE FOLLOWING SECTION ESTABLISHES MS STATUS LBK 7,6 GET SCAN BYTE N HI 7,X» 0007' SET UP SHUNT FOR INDEXING AHR 7,7 BZ * + 24 IGNORE CRUDE BASES I F SHUNT ZERO SHI 7,2 LH 8, CRUDE (7) GET CRUDE BASE BNZ * + 8 IF ZERO, THIS POINT IS CRUDE BASE STH 5,CR UDE(7) SO STORE I T SH 5 ,CRUDE (7) SUBTRACT CRUDE BASE L BR 7,6 CHECK SCAN CHARACTER NHI 7,X'0070 • SCANNING ? BNZ * + 20 YES, BRANCH LHI 1,X'4200 ' NO, SO RESET CNTRL AND BCALC STH 1,CN TRL SWITCHES AND BRANCH TO BASES STH 1 ,* + 8 B BASES BFC 0,*+24 FIRST NON-BASELINE POINT CAUSES BRANCH BAL 15,BCALC TO * BCALC' LHI 1,X '4300 » THEN BCALC SWITCH IS RESET STH 1 1 2 LHI 1,X'4200 ' AND MAXMUK SWITCH IS I N I T I A L I Z E D STH 1,MAXHUM CLHI 7,X'0070' CHECK FOR SCAN REJECT BE REJECT REJECT FOUND - REJECT SCAN CLHI 7,X» 0030 • CHECK FOR END OF SCAN BE SOS END OF SCAN FOUND B MAXMUM OTHERWISE GO TO KAXHDH SPACE 1 Z B YTE DS 2H NPTS DS H LAST DS H RESET DS H SW DS H FILPT DS H BUFF1 DS 6C SPACE 2 *******************************.****** ************************** * * * ' CONTRL* CALLED BY 'ROUTINE' VIA HI 5 * 1 3 ? A p p e n d i x F Program L i s t i n g *************** *******************************#*$*## fc******^^. SPACE 1 BTC 0 , H E R E NORMALLY BRANCH TO 'HERE' STH 5,PR EV EXECUTE THIS SEQUENCE AT START OF EACH LB 4,FAST SET RATE TO FAST STB 4,RATE LHI 9 , X« 4300 » SET CNTRL SWITCH STH 9,CN TRL LH 9 ,SW CHECK SW N HI 9,X« 0009' BZ *+14 BRANCH I F SW OFF LHI 9,X'4200' RESET CNTRL SWITCH STH 9,CNTRL BR 15 EXIT LH R 9,5 R5 CONTAINS NSW POINT SH 9, PREV R9 CONTAINS CHANGE IN DVM READING STH 5,PREV BP PLUS I F DIFFERENCE >0, MAY BE GOING UP PEA BM MINUS IF DIFFERENCE <0, MAY BE COMING DOWN PEAK LH 0,NPTS SH 0,CHECKPT SPEED WILL BE SET TO 'FAST • 16 SECS. CLHI 0,H« 64 » AFIER PEAK IS DETECTED BL * + 12 LB 0,FAST STB 0 , R A T E OC 3 ,SPEED SET FOR SCAN RATE CONTROL WD 3, RATE BR 15 SPACE 2 CLHI 9,H« 50 » IS DIFFERENCE SIGNIFICANT ? BL RTRN NO LB 4,RAT E CLHI 4,4 WAS RATE SET TO 'FAST* ? BL RTRN NO, PEAK ALREADY DETECTED LH 4, NPK YES, SO FIND OUT HOW MANY PEAKS SO FAR AH I NPK IS NO. OF PEAKS SO FAR STH 4, NPK LH 0,NPTS STORE TIMS OF SPEED CHANGE STH 0,CHSCKPT CLHI 4,2 BNL *+ 16 PAST FIRST PEAK, SO SPEED SHOULD EE ST. LB 4 , MED SPEED SHOULD BE MEDIUM STB 4,RATE SET RATE B RTRN , LB 4,SLOW SET SPEED TO SLOW STB 4,RATE B RTRN SPACE 2 8' 8 HHX IKnoo'Ol H I S l ' OL IHV IKHOD'OI HRI IIDIIMS wnwxvw i s s wnwxvw'o I HIS t 00£ !7 . X'01 I HI t?-*' c l 3 i x a V 3 H Y MHOH MfiWXVW QX'AZ (£l) O ' l l H I S i N n o o ' tu mi c"ei I H l H H M £ I i i n SKOIIDflHISNI I t ' l l HHX SNIflOTIOd v L S V d HDNVHff XTIVWHON waON ' o DI3 l HDVdS wnwxVH ****************************** ********************************* * * * laNIIOOHi A? Q i m V D t U Q U X V H i * * * *************************************************************** t; 3DVdS SIAH 3dDS e MS 'Z. HIS .8000 « X ' Z. IHO MS i n s MS '/„ HI isva'e a a ISV3 01 GSSdS HVDS ISS 032dS'c DO (OH3Z) V xviasia KO oaaz aiiaw •idsia'si ave t 3DVdS loaraa ************************************** ************************* * * * i3MIinOM. A0 G3HVD I I D 3 D 3 H I * * * *************************************************************** I D 30 3 H sa IdMDSHD H sa A38d II sa 3 i v a H sa MdN I -* noa M O T S i 1020 i X DO aaw • eotioi x oa I S V i z aovds NHia a axvH' ti a i s ISV3 01 HIVH I3S I S V3 'tj e i O N NO xa 1Q INVDI3IMDIS 3DN3H333I0 SI »00Z iH'b I HID 1'6 III V IHawaidWOD S i O M I 3MVJ. » J 3 3 3 i X ' 6 IHX sn.N iw BUT^ST'I uit jaBoad 3 xtpuaddv 1 3 9 A p p e n d i x F Program L i s t i n g LH 11,CRNT + 4(8) MOVE POINTS IN CRNT BUFFER STH 11,CRNT (8) LH 11,CRNT+6(8) STH 1 1 ,CRNT + 2 (8) AHI 8,4 CLHI 8 ,H'16• BL *-24 BRANCH I F NOT ALL MOVED STH 5,CRNT+16 ADD NEWEST POINT STH 6,CRNT+18 AND SCAN BYTE LH 9,CRNT+B AH 9 #CRHT+12 ADD LAST THREE POINTS AH R 9,5 STH 9,WRK+8 STORE SUM IN WORK AREA CLHI 10,5 I F < 5 POINTS, SKIP MAXIMUM CHECK BL SHIFT LH 10,NFPTS R10 CONTAINS TIME SPACE 2 MAXI XH R 4,4 LH 8,WRK+4 GET POINT TO BE TESTED LHR 13,8 (CENTRE POINT OF FIVE) SH 13,WRK(4) SUBTRACT ONE OF THE OTHER POINTS BM SHIFT I F < 0, NO MAXIMUM BNZ *+12 CENTRE POINT > OTHER POINT CLHI 4,4 I F POINTS ARE EQUAL, AND OTHER POINT BNL SHIFT COMES AFTER CENTRE POINT, BRANCH AH I 4,2 CLHI 4,4 DON'T COMPARE POINT WITH I T S E L F ! BE *-8 CLHI 4,10 DONE ? BL MAXI+6 NO, SO BRANCH B YES FOUND A MAXIMUM! SPACE 2 LH 4,SW OHI 4,4 TO FLAG ERROR STH 4,SW SHIFT XH R 4,4 LH 7,WRK + 2(4) STH 7,WRK(4) HOVE POINTS OVER IN WORK AREA A HI 4,2 CLHI 4,8 ALL DONE ? BL SHIFT+2 NO, CONTINUE B SUPERVIS SPACE 2 YES LH 9,NMAX GET MAXIMA COUNTER CLH 9,XS OVERFLOW TABLE ? BNL SHIFT-12 YES, SO SKIP IT X HR 11,11 LHI 12,4 LHI 13,8 LHI 14,-10000 140 Appendix F Program L i s t i n y MAXLP XS WRK CR NT COUNT LH 1,CRNT{11) S HR 1,14 BH *+10 LH 14,CRNT(11) LHR 2,11 BXLE 11,MAXLP LH 11,CRNT + 2(2) STB 11,SHMAX(9) A HR 9,9 LH 11 , C R NT (2 ) STH 11,MAX(9) SRHA 2,2 AH I 10,-3(2) STH 10,1 MAX (9) SRHA 9,1 AHI 9,1 STH 9,NMAX B SHIFT SPACE 2 DC H « 3 2 ' DS 5H DS 10H DS H SEARCH FOR MAXIMUM OF THE THREE POINTS SUBTRACT PREVIOUS MAXIMUM PREVIOUS MAXIMUM BIGGER THIS POINT BIGGER STORE MAXIMUM POINTER GET SCAN AND STORE GET POINT STORE BYTE IT OF MAXIMUM IT S E L F AND STORE TIME OF MAXIMUM INCREMENT COUNTER PREPARE TO EXIT EJECT ***************************************** * * * "EOS 1 CALLED BY 'ROUTINE" AS NORMAL EXIT * * * ********************* ***************************** ************* EOS SPACE 1 BAL 15,DISPL ZERO DISPLAY DC A (ZERO) LH 8, NFPTS CARRY-OVER FROM PREVIOUS SCAN ? CLHI 8 , H ' 1 0 » BNL * + 8 NO, SO BRANCH B SUPERVIS MULTIPLE SEPARATES LIKELY LH 9, SW SET SW TO INDICATE END OF SCAN OHI 9,X« 8000 • STH 9, SW LH 9 , TOTAL STH 9,TOTAL 2 LH 8 , NFPTS A HR 8,9 INCREMENT TOTAL POINT COUNTER STH 8 ,TOTAL X HR 8, 8 CLEAR CERTAIN COUNTERS STH 8,NPTS X HR 11,11 STH 11,NFPTS STH 1 1 , CRUDE (8) AHI 8,2 141 A p p e n d i x F Program L i s t i n g CLHI 8,10 BL *-12 LHI 9,X'4200» RESET SOME SWITCHES STH 9,CNTRL STH 9,BASES STH 9,MAX MUM LH 8,SW SKIP PROCESSING IF SCAN REJECTED NHI 8,X«0008» BNZ *+16 BAL 15,REFINE SUBTRACTS TRUE BASELINES BAL 15,PEAK PICKS PEAKS BAL 15,CALC CALCULATES RATIOS BAL 15,CONVERT PREPARE FOR PEAK PRINTOUT LH 8 f N S C A N INCREMENT SCAN NO. AHI 8,1 STH 8 , NSC A11 XHR 8,8 LHI 9,NMAX LHI 10,2 LHI 11,BHU+18 TOP OF ZERO-ED REGION STH 8,0(9) ZERO MAXIMUM TABLE BXLE 9,*-4 LHI 15,X«00C8» NH 15,SW LOOK FOR REJECT INDICATION BNZ PRINT FCALC BAL 15,FRACT CALCULATE NORMALIZED SR87/SR86 SPACE 1 PRINT LPSW * + 4 ENABLE INTERRUPTS ****** DC X'4000» DC A(*+2) LHI 13,MAIN SAVE LHI 1U,*+12 BAL 15,SIBTOD CONVERT SCAN NO. TO A S C I I DC A (NS CAN) DC A(BT EM P) LH 1,BTEMP + 4 LOAD NO. OF SCANS (MAX. OF 99) STH 1,PROUT+14 STORE IN PRINT OUTPUT AREA LH 11,ITYDSR LOAD R11 FOR OUTPUT SEQUENCES LM m,PLIST1 BAL 10,OUPT CALL TO SET UP PRINT LHI 1 5 , X « 0 0 C 8 ' CHECK FOR REJECTS XHR 1,1 N H 1 5, S W STH 1 ,SW RES ET SW BNZ SUPER VIS LH 15,12(11) WAIT FOR COMPLETION OF PRINT BNZ *-4 LM 14,PLIST2 BAL 10,OUPT CALL TO SET UP PRINT LH 15,12(11) WAIT FOR COMPLETION OF PRINT 142 Appendix F Program L i s t i n g BNZ *-4 LM 14,PLIST3 BAL 10,OUPT B SUPER VIS SPACE 2 SPACE 2 DS H DS H DS H EJECT CALL TO SET UP PRINT ***************************************** * 'BASES' CALLED BY 'ROUTINE' AS NORMAL EXIT * * * ********************************* ****************************** SPACE 1 BTC 0 , BYPASS SKIP FOLLOWING SECTION IF NOT FIRST X H R 11,11 LHI 1 2,T EMP ZERO BASELINE MATRIX LHI 13,2 LHI 14 ,BASE + 8 STH 11,0(12) BXLE 12 ,*-4 LHI 7,X'4300' SET SWITCH STH 7 , BASES LH 2,NFPTS LBR 7,6 NHI 7,X 'C007' GET SHUNT AND ADJUST FOR ADDRESSING AH R 7,7 BZ * + 8 TREAT ZERO-SHUNT AS ONE-SHUNT SHI 7,2 LH 4, NBASE (7) ANY POINTS ON THIS SHUNT YET ? BNZ *+ 12 YES, SKIP STH 2, FIRST (7) NO, SO STORE TIME B *+ 15 LHI 1,-1 (2) CLH 1 ,TEMP (7) ARE POINTS CONSECUTIVE? BNE SUPERVIS EXIT IF NOT! STH 2 ,TEMP (7) CLHI 4,H'50 1 MORE THAN 50 POINTS ON THIS EASE ? BNL SUPERVIS YES, SO RETURN AHI «,1 STH 4 , NBASE (7) INCREMENT NBASE AH 5, BA SE (7) STH 5 , BASE (7) B SUPER VIS SPACE 2 DS 5H DS 5H DS 5H 143 A p p e n d i x F Program L i s t i n g BASE DS 5H SPACE 2 ************************************** * * * 'BCALC 1 CALLED BY 'ROUTINE* VIA R15 * * * *************************************************************** SPACE 1 BCALC XHR 4,4 STH 4,NPK ZERO NPK IN CNTRL LH 2,NBASE(4) GET NO. OF BASELINE POINTS BNZ *+18 I F ZERO, NO POINTS ON THIS SHUNT AHI 4,2 CLHI 4,H»10» BNLR 15 EXIT POINT B BCALC+6 TRY ANOTHER S HUNT XHR 8,8 LH R 1,2 CALCULATE CORRECTION SR HA 1, 1 FOR ROUNDING LH 9, BASE (4) GET SUM OF POINTS BNM *+14 SKIP I F NUMBER POSITIVE LHI 8,X'FFFF» GENERATE 32 BIT NEGATIVE NUMBER SHR 9,1 B * + 6 AHR 9,1 DHR 8,2 DIVIDE SUM BY NUMBER OF POINTS AH 1,FIRST (4) CALCULATE TIME FOR POINT CLHI 7,X'0020' DETERMINE WHICH PART OF SCAN WE'RE IN BNE *+12 LHI 8,BHD SCANNING DOWN B * + 20 BNL *+12 LHI 8,BLO SCANNING UP B * + 8 LHI 8,BHU END OF SCAN SLHA 4,1 AHR 8,4 CALCULATE WHERE TO STORE RESULT SRHA 4,1 LH 10,2(8) SOMETHING ALREADY THERE ? BNZ *+12 YES, SO DON'T STORE THESE NUMBERS STH 9,0(8) STORE AVERAGED POINT STH 1 ,2 (8) STORE TIME XHR 2,2 STH 2,BASE(4) ZERO BASE AND NBASE FOR THIS SHUNT STH 2, NBASE (4) STH 2, FIRST (4) ALSO ZERO FIRST B BCALC+14 DO ANOTHER SHUNT SPACE 6 ************************************** * ***************:********* A p p e n d i x F Program L i s t i n g •CONVERT' CALLED liY 'EOS' VIA R15 *************************************** SPACE 1 SAVE R15 FOR RETURN CONVERT LHR LK LH CONV1 L H I SLHL ETC LHI STB BXLE L H I NH * BZ L H I STH BE LHI L H I LHI L H I STH BXLE 6,15 13,SWL1ST 1 2 , S W 1 , C 1 ' 12,1 8, *+ 8 1,C 0' 1,0(13) 13 ,C0NV1 7,X« OOFS' 7 ,SW FOR FUTURE * + m 1,PROHT+36 1,PLIST1+2 6 7 ,I!TS 8,2 9, PR OUT 1-2 1,X'2020 ' 1 ,0 (7) 7 , *- 4 CONVERT SW BITS TO A S C I I . ;HANGES, SHOULD I N I T I A T E OUTPUT HERE. * RETURN BLANK OUT OUTPUT AREA SPACE 1 L H I 13,EA1NSAVE FOR SUBROUTINE CALLS LHI 14,* +12 BAL 15, SIBTOD TO CONVERT AV'GE. TIME FCR SR86 DC A (MI DTI ME) DC A('TMEAN) LHI 1 5 , C (' STB 1 5,TM EA N SPACE 1 LH 12,NPEAKS APR 12,12 SHI 12,1 XH R 2,2 XHR 3,3 LHI 4,C ' L H I 11,HTS LHI 1,X'8D0A' SPACE 2 CONLOOP LH 7,MIDPEAK(3) L H I 14,*+8 B CONV STB 4,0(11) TO BLANK SIGN AHI 11,8 LH 7, DECAY (3) R12 CONTAINS NO. OF PEAKS FCUN: ADJUST R12 FOR ADDRESSING R3 WILL COUNT HALFWORDS S4 WILL BE USED TO BLANK SIGNS 14 5 A p p e n d i x F P r o g r a m L i s t i n g LHI 14,*+8 B CONV AHI 11,8 AHI 3,2 SPACE 2 CONLP LB 8,POINT (2) G E T POINTER BYTE LH 7,IHAX (8) GET TIME O F MAXIMUM AH 7,TOTAL2 CALCULATE TIME FROM START OF R U N LHI 14 r* + B RETURN ADDRESS FOR SIBTOD B CONV CONVERT TIME TO ASCII LH 7, MAX (8) GET M A A I M U M AHI 11,8 LHI 14,*+8 RETURN ADDRESS F O R SIBTOD B CONV CONVERT PEAK HEIGHT TO ASCII LHR 7,8 LB 8,POINT (12) G E T POINTER FOR UPMASS SECTION C LH R 7,8 D U N E [JPrlASS A N D D O W N H A S S PEAK ? BE KHERE+2 Y E S , S U BRANCH AHI 11,8 N O , SO D O UPKASS P E A K B CONLP+4 SPACE 6 CONV STH 7,BTEMP STH 1 1 , W H E R E B A L 1 5 , S I B T O D DC A (B T EMP) WHERE D S H SPACE 2 AHI 11,6 STH 1,0(11) INSERT CR/LF IN T O TEXT AHI 11,6 ADJUST REGISTERS TO D O NEXT PEAK AHI 2,1 SHI 12,1 CLHR 2,12 PEAKS ALL DONE ? BL CONLOOP N O , M O R E PEAKS TO D C SHI 11,4 STH 11,PLISTl+2 S T O R E ENDING ADDRESS OF FIRST BUFFER BR 6 RETURN FROM 'CONVRT' SPACE 2 PROUT DC X«8D0A' DC C'SCAN NUMBER « DS H DC C» 0000000000000000* DC X ' 8DO A8 DO A ' DC C* PEAK D A 1A • TMEAN DC C * ) : * DC X'BDOA' DC C » « HTS DC 135X'2020« PROUT1 DC X*8D0A* DC C RATIOS: ' Appendix F Program L i s t i n g DC X '8D0A • DS 2H RATI01 DS 12C RATI02 DS 12C BATI03 DS 12C RATI04 DS 12C PR0UT2 DC X' 8 DO A « DC C« NORMALIZED RATIO: • NRATI 0 DC 4X'2020 • DC X' 8D0A' PLIST1 DC A (PROUT) DS A TO US SET PLI ST2 DC A (PROUT 1) DC A (PROUT2- 1) PLIST3 DC A (PR OUT2) DC A(PROUT2+3 1) MAY BE RESET I F SPIKED SWLIST DC A(PR0UT+18) DC H * 1' DC A (PROUT + 3 3) EJECT * * *** * * * * ******** REFINE * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 1 REFINE' CALLED BY 'EOS' VTA R i 5 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * SLOOP SPACE 1 STH 3,RTEMP2 SAVE RJ AND R15 STH 15,RTEKP3 XHR 1 , 1 L H I 7,DELTD ZERO WORK AREA LHI 8,2 L H I 9,CORR+18 STH 1 , 0 (7) BXLE 7, *- 4 LHI 14,DELTD ADDRESS FOR STORING RESULT. LHI 10,BHD ADDRESS OF FIRST SET OF BA: LHI 11,3L0 ADDRESS OF SECOND SET XHR 4,4 LH R 12,10 SET UP REGISTERS FOR AD DR E AHR 12,4 LHR 13,11 AHR 13,4 LHR 15,14 AHR 15,4 LH 7,2 (12) GET TIME OF FIRST SET BZ NONE NO POINTS ON THIS SHUNT STH 7 ,TI MES (1 ) STORE TIME OF SET LH 8,2(13) GET TIKE OF S"CO: D SET BZ NONE I F ZERO, TROUBLE j SHR 8, 7 FIND DELTA T 1^7 A p p e n d i x F Pr o g r a m L i s t i n g STH 8,2 (15) STORE I T LH 7,0(12) GET BASELINE VALUE FOR FIRST SET STH 7,C0RR(1) LH 8,0(13) GET OTHER BASELINE VALUE SH R 8,7 FIND DELTA H STH 8,0(15) STORE I T NONE AHI 1,2 A HI 4,4 CLHI 4,H ,20» ALL S [HI NTS DONE ? BL SLOOP NO, CONTINUE CLHI 14,DELTU DONE BOTH BLOCKS ? BE SPIN YES LHI 14,DELTU SET UP TO DO UPMASS BLOCK LHR 10,11 LHI 11,DHU B SLOOP-2 GO AROUND AGAIN SPACE 2 SFIN XHR 11,11 LHI 12,1 MAX SET UP REGISTERS FOR PEAK HEIGHT L H I 13,M A X A D J US T M EN T LHI 14,SHMAX MORE LHR 8,12 AHR 8,11 R8 IS TIM E PO TNT ER LHR 9,13 AHR 9,11 R9 IS H DIG HT POINTER SR HA 11,1 LHR 10,14 AHR 10,11 RIO I S SCAN BYTE POINTER AHR 11,11 LB 7,0(10) GET BYTE NHI 7,X»000 7» GET SHUNT BZ DUN ZERO SHUNT MEANS ALL PEAKS DOME AHR 7,7 SHI 7,2 USE SHUNT FOR ADDRESSING LH 6,0(8) GET TIME FOR MAXIMUM CL H 6, TIMKS+10 (7) COMPARE TO TIME AT CENTRE OF SCAN BNL *+14 I F GREATER, WANT UPMASS BLOCK XHR 0,0 LHI 4,DELTD I F LESS, WANT DOWN MASS BLOCK B *+12 LHI 0,1 FLAG RO TO INDICATE BLOCK L H I 4,DELTU AHR 4,7 AHR 4,7 ADJUST POINTER LH 3 , 2 ( 4 ) GET DELTA T FOR BASELINES BZ NOBASE NO BASELINES FOR THIS MAXIMUM ! LI! R 0,0 S ET CO ii D IT ION CODE BNZ *+12 GET TIME OF RIGHT BLOCK SH 6,TIMES (7) CALCULATE DELTA T FOR MAXIMUM B * + 8 * s i a VIA .aost AR G:rn¥D .HVZJ. * OKIb'SiiOOHd HV3S d l H S SUSXSIMH HMOIS:^ voc IOEL'ELI os 'MViid v aod S;INI'I3SVO OK 7 u 30VdS not sa HOI sa sa 35 sa 3D YdS (SI) 8 HI i n HS'L HIS « 0800 tY.' L I HO HI I 3.~>VdS 3 HOD S3WIX a n s a asvnoN t 8 0 3 8 3 U O i 5 1 3 V ™ A, c ™ . A S ¥ G 0 N . : I.IXd 2 33VdS SHEIST:^:H a MO A sr. a oa OJ, s j i i i o u snow NOTIDHHHOD AlddV WflNIXVW .IPIt) 3AI1V05K 3 A H I S O d l o n a o a d JO NOTS jioano a o i o v j i i o - a N o o a IN3WISIira\f o i i u vn i ou rD s i 3KOH a Z * t L THY ( 6) 0' I IUS t ' l HHS (6) 0' L HI (/.) oi+aaoo't HV 8+* a (/L)HH03'£ HV o' o a m ( t j ) z ' z Ha TIN'2 HOV 9*£ HHV 01 +* 3 H N ' Z HOS 9 J £ ans tii +* w N a z'z mi i ' 9 vnas ( i j)2'9 HI (fi) 0 ' 2 HH 9'C a m (/.) 0 L + S3WII'9 IIS N DO fiut^sTi u m j 6 o j d J x xpuec l dv A p p e n d i x F Program L i s t i n g SPACE 1 PEAK LHI 10,X'1000' OH 10,SW STH 10,SW XHH 10,10 STH 10,NPEAKS ZERO NPEAKS STH 15,PEAKEXIT+2 FOR RETURN LH 9, KM AX BZ ERRET NO MAXIMA ! A HR 9,9 XH R 2,2 X HR 1,1 MAJOR LP 7,MAX (10) GET A MAXIMUM BM *+12 CLHI 7,Ii'25' BIG ENOUGH ? BNL OK YES AHI 10,2 NO CLHR 10,9 DONE ALL MAXIMA ? BL MAJOR B DONE YES OK STB 10,POINT (2) STORE MAXIMUM POINTER LH 0 , IM AX (10) GET T1 K E 0 F M A XIM U M SHR 0,1 FIND TIME DIFFERENCE FROM PREVIOUS LH 1,IMAX(10) MAXIMUM CLHI 0 , H « 1 2 ' BL FIX TWO MAXIMA CN ONE PEAK ! AHI 2 , 1 ALL OK LH 4,NPEAKS INCREMENT NPEAKS AHI 4,1 STH 4, NPEAKS B MAJOR+16 CONTINUE FIX LHR 4,2 SHI 4,1 P4 NOW POINTS TO PREVIOUS MAXIMUM LB 8,POINT (4) CLH 7,MAX (8) COM PAR E THE MAXIMA BL MAJOR+16 PREVIOUS MAXIMUM IS BEST BE MAJOR+16 STB 10,POINT (4) USE NEW MAXIMUM B MAJOR+16 SPACE 2 DONE LH 12,NPEAKS GET NUMBER OF PEAKS BZ ERRET NO PEAKS ! SRHA 12,1 DIVIDE BY TWO BFC 8,*-+20 EVEN NO. OF PEAKS ERRET LH 9,SW SET SW FOR REJECT -OHI 9,X»0040» ERROR HAS OCCURRED STH 9,SW B 4(15) SKIP REST OF PROCESSING STH 12,NPEAKS A HR 12,12 Appendix F Program L i s t i n g SHI 12,1 LB 8,P0INT+2 GET POINTERS FOR SR86 PEAK LB 9 , POINT-2 (12) R8 FOR DCWNMASS PEAK, R9 FOR UPMASS LH 13,IKAX(8) AH 13,1 MAX (9) AIII 13,1 SRHA 13,1 R13 HOLDS TIME FOR SR86 PEAK LHR 11,13 AH 11,TOTAL2 ADD BAS ETIM E FOR THIS SCAN STH 11,M iDTIME XHR 11,11 XHR 2,2 PLOOP LB 8,POINT (2) LB 9, POINT (12) LH 5,MAX (8) GET DOW KM ASS PEAK HEIGHT LH 7,MAX (9) GET UPMASS PEAK HEIGHT SRHA 8,1 SRHA 9,1 * THIS PART REPLACED BY R.D.R. DECEMBER 1, 1973 * TO IMPROVE NUMBER OF SIGNIFICANT FIGURES. * SCALING AFTER MULTIPLYING BY SHUNT FACTORS IS * S-23:8 IN A FULL '..'OR I) LB 1,SHMAX(8) DOWN MuSS SHUNT N HI 1,7 AHR 1,1 MH 4,FACT-2(1) MULTIPLY BY SCALED SHUNT FACTOR LHR 15,4 START TO ADJUST FDR NON-NOMINAL VALUES MH 14,CORRN-2 (1) AHR 5,15 ACHR 4,14 LB 1,SHMAX(9) UP MASS SHUNT N HI 1,7 AHR 1,1 MH 6,FACT-2(1) MULTIPLY BY SCALRD SHUNT FACTOR LHR 15,6 START TO ADJUST FOR NON-NOMINAL VALUES MH 14,CORRN-2 (1) AHR 7,15 ACHR 6, 14 AHR 8,8 AHR 9,9 SHR 7,5 FIND HEIGHT DIFFERENCE BETWEEN PEAKS SCHR 6,4 LH 0 ,1 M A X (8 ) T IM E O F DOW N M AS S P E AK LH 14, IK AX (9) TIME OF UPMASS I' E A K SHR 14,0 FTND TIME DIFFERENCE LHR 15,13 TIME OF SR86 PEAK SHR 15,0 TIME DIFFERENCE FROM SR86 PEAK DHR 6,14 CALCULATE (DH/DT) STH 7 ,DER IV4 2 R7 ~ uii/DT *FACT M HR 6,15 Appendix F Program L i s t i n g AHR 5,7 ACHR 4,6 STH 4, PEAKS (11) STORE PEAK HEIGHT ( 32 BITS ) STH 5,PEAKS+2 (1 1) CALCULATED AT MIDPOINT OF SR86 DH 4, FACT-2 ( 1) DIVIDE BY SHUNT (SCALED) FOR OUTPUT SRHL 11,1 STH 5, MIDPEAK (11) XHR 6,6 DEB IV LHI 7,0 DI!/DT*rACT WAS STORED HERE B N M * + 8 LHI 6,X'FFFF« 32-BIT CONVERSION FOR NEGATIVE NO. LH 0,FACT-2 (1) SHUNT FACTOR 8:8 SRHL 0,8 16:0 DH R 6,0 R7=DH/DT 8:8 SL HA 7,2 6:10 MH 6,CONST CO!lST= 10**6/2** 10=977 DHR 6,5 R7=DH/DT/H*10**6 STH 7, DECAY (1 1) A HI 11,4(11) R11=2*R11+U A HI 2,1 SHI 12,1 CLHR 2 ,12 DONE ALL PEAKS ? BL PLOOP NO, GO ROUND AGAIN LH 4 , NPEAKS SL HL PLO0P2 LM 14,PEAKS+8 LHR 14,14 BNZ *+10 LHR 15,15 PEAKEXIT BKM 0 LHR 5,4 LM 14 ,PEAKS-4 (5 ) BAL 1 ,DBLESHFT STM 14 ,PEAKS-4 (5) SHI 5,4 BP *-16 B PLOOP2 SPACE DBLESHFT SRHL 15,1 SRHL 14 ,1 BFC 8, *+8 OHI 15 ,X'8000• BR 1 SPACE 2 POINT DS 10C PEAKS DS 5F NP EAKS DS H MI DTI ME DS H MILPEAK DS 5H DECAY DS 5H 0001 = HOIDVJ 31VDS S 3 D V l d I V U I D a a 33HSiI ON i oe > iwvd H S D S I K I 0 0001 = HO!DV,>] 3/1VDS S S D V l d IVWIDSa HflOd ON I £ > IHVd H3D3 IK I H 3 (1M IV [•! 3 H 3A0W OliYa 3 0 J,H¥d >?30^NI aivumvo 31V ii ilSIIIO 13 D II10I311 MV3d 130 HSJjHflOD d O O l SI L i a vaav i n d i n o 30 s s a a a a v BKiasnoa aoa iNawisnrav MV3d 98US £ 2 0 vaav indino ouva MNVIQ ************************************ * si a V I A »S03» ************** * ****** *************** 0 1 * * Z / 9 * * 0 l waso'tj m E ' 8 I H 1 9L+* I R Q I O E I H ' I I1I3D 31V3S 8 WN3l'h 111 n'8 i i n 9L + * I N S E ' l I H 1 3 o'E a m EL'O ana ( S ) Z ' l H I (s)o'o in asfloav I ' l l I H S SMVSdM'U H I 9'9 8HX l o n v a ' z i i i n \'L V H 3 S i i ' L a H I (S)0l'£t H I S U V 3 d ' S I H I t f - * ' E i aixe. (EL) O'Zl H I S I O Z O Z I X ' Z I I H 1 z - z m o u d ' s i i i n Z ' t r l I H 1 b-ioiiva'ei n n M S ' S I H I S M S ' S I HO I O O O Z I X ' S I I I I 1 S d M j i a ' S L H I S 3 1 V C L aovds *************************** J3 G371V3 I O I V O I * * * * * * * * * * * * * * * * * * * * * * * * * * * * i D a r a 9 U * Z * a o i 3 V d Naaoo 8 * * z * aoiova » Lib i l l i 0 i 11 1O1H i 0 i H IO iH • 0 iH • 9 E L 0 Z a H • Z l fa9iH « hOEZiH » 8 9/. iH i 9 SZ i H oa oa oa oa Da oa oa oa oa oa 5UT}STI uiB.i6oJd J XTyueddv 153 Appendix F Program L i s t i n g B S C A L E C L H I 1 , H « 3 0 0 « I N T E G E R P A R T < 3 0 0 ? B N L * + 1 6 NO L H I 8 , 2 TWO D E C I M A L P L A C E S L H 4 , O N E C S C A L E F A C T O R = 1 0 0 B S C A L E C L H I 1, IP 3 0 0 0 * I N T E G E R P A R T < 3 0 0 0 ? B N L * + 1 6 NO L H I 8 , 1 O N E D E C I M A L P L A C E L H I , T E N S C A L E F A C T O R = 1 0 B S C A L E X H R 8 , 8 I N T E G E R P A R T > 3 0 0 0 ! B * + 1 3 S C A L E F A C T O R - 1, S O S K I P S C A L I N G S C A L E MHR 0 , 4 S C A L E I N T E G E R P A R T O F R A T I O MHR 2 , 4 S C A L E F R A C T I O N A L P A R T AHR 3 , 7 F O R R O U B D I K G A C H 2 , N I L DHR 2 , 1 3 C A L C U L A T E F R A C T I O N A L P A R T O F R A T I O A H R 1 ,3 S T H 8 , N D E C ( 6 ) S T O R E NO. OF D E C I M A L P L A C E S S T H 1 , B I N S T H 1 , B ? A T I O ( 6 ) S T O R E B I N A R Y R A T I O S T H 1 3 , P I X U P + 2 S A V E in 3 L H I 1 3 , M A I N S A V E L H I 14,*+16 R E T U R N S T H 1 2 , * + 1 0 B A L 1 5 , S I B T O D C O N V E R T R A T I O TO D E C I M A L N U M B E R DC A ( B I N ) D S H A D D R E S S O F A S C I I R A T I O F I X U P L H I 1 3 , 0 R E S T O R E R 1 3 L H R 8,8 B Z NO D E C NO D E C I M A L P O I N T L H R 1 0 , 1 2 D L O O P L B 9 , 5 ( 1 0 ) MOVE B Y T E S TO R I G H T O F D E C I M A L P O I N T C L H I 9,X« 0 0 2 0 * A B L A N K ? B N E * + 8 NO L H I 9 , X ' 0 0 3 0 * Y E S , R E P L A C E BY Z E R O S T B 9 , 6 ( 1 0 ) S H I 8 , 1 D E C R E M E N T C O U N T E R BZ * + 1 2 M O V E D A L L B Y T E S S H I 1 0 , 1 B D L O O P MORE TO MOVE L H I 9 , X « 0 0 2 E « A D E C I M A L P O I N T S T B 9 , 5 ( 1 0 ) N O D E C A H I 5,4 C L H I 5 , P E A K S + 8 NO N E E D TO C A L C U L A T E S R 8 6 / S R 8 6 R A T I O ! B E * - 8 A H I 6 , 2 A H I 1 2 , 1 2 S H I 1 1 , 1 D O N E A L L P E A K S ? aoiova ssvw-aNO aao-aNnoa aaow I I aZTTVk'HOK Q M V 01IVii 9RHS/Z.RHS 13 L) am SMIVIKOD KGN ba HOSIATQ aanaaooaa aao-aNnoa a iv.os ID varans o u v a 98as/8sas aaansvaw o u v a 9 0 H S / 8 8 H S aaidasov 333ana vsav oiivaN MMvia indino O I N I iie-ws s i m z + o n v a a ' i H I S wNai'o Ha IIS '0 HOV I O O O S I H ' I IHV 6'o an H z+onvaa ' L H I WHSI'6 HV OL'O ana 0 l ' 0 l HH V 7 I N ' 8 HDS oi '6 mis OL +* 8 I I N ' 8 HOV 0 L'6 MHV f 7 l + * HQ 8 ' 8 a HI K M a I ' 8 HW onvaa'6 HS OL'6 an 1 i 9 / . £ 8 i H f 0 t IH1 9+OIIVHM'OL HIS •OZOZiX'OL IH1 bL+xnoad 'SL ais i l I O ' S L IHl MS'Sl HIS MS' 51 HO lOOOtuX'Sl I H l zawaia'si HIS I D V H J L aovds ************************************** * * * sia V I A isoa» m aanvo iiovadi * * * *************************************************************** Z aovds Hti sa DaaN Ht7 sa oiivag H sa m a * 0 0 0 0 L i H oa wuai i00 01iH oa W3N0 i 0 01 i H oa D3NO i 0 I i H oa N3I z aovds Mania a ' sa A SL aa Sduaia'si HI a N i i / N a n i a a aoviaavo a aois (Zl) l L L HIS as a aaaana ao ssa auv Z+ZISIld'Z L HIS I'Zt IHS sai iV0G8 » X ' LL IHl ON ON noav da B U X ^ S T I uiBa6oad 3 xxpueddv 155 Appendix F Program L i s t i n g D S H I F T LHI 1 3, MA IN SAVE LHI 14,*+ 12 BAL 15,SIBTOD DC A (BRATIO + 2) DC A (HRATIO) LH 8,NDEC+2 BNZ DSHIFT LH 15,BTEMP 2 BH 15 LHI 10,NRATIO LB 9,5 (10) CLHI 9,X* 0020 • BNE * + 8 LHI 9,X'0030' STB 9,6 (10) SHI 8, 1 BZ * + 12 SHI 10,1 B DSHIFT+4 LHI 9,X«002K ' STB 9,5 (10) LHI 9,PROUT2+31 STH 9,PLIST3+2 B DSHIFT-6 SPACE 2 RETURN CONVERT NORMALIZED RATIO TO A S C I I NUMBER OF NOT ZERO, 5 EXIT POINT DECIMAL PLACES SO BRANCH MOVE BYTES TO INSERT ZEROES IF NEEDED RIGHT OF TO RIGHT DECIMAL POINT CF DECIMAL POIN LOOP COUNTER ALL DONE CONTINU E DECIMAL POINT STORE IT IN NUMBER ADDRESS OF GO TO EXIT BUFFER END POINT *************************************************************** * * * 'DISPL' CALLED BY 'SWITCH' VIA R15 * * * *************************************************************** SPACE 1 IN DC X '0809 • DC X 'OAOB ' DC X*OCOD' DC X 'OEOF ' OUT DC X ' 0 0 01' DC X '0203 ' DC X'0405' SPEED DC X '06 07 • BUFF DC X» 2B30' DS 8C SPACE 2 DISPL LH 1,0 (15) ADDRESS OF NUMBER TO BE OUTPUT LHR 2, 1 AH I 2,5 ENDING ADDRESS XHR 4,4 DISLP LB 0,0(1) GET BYT E TO BE DISPLAYED CLHI 0,X'002E' IS IT A DECIMAL POINT ? BE DECOUT YES OC 3,OUT (4) OUTPUT DIGIT Appendix F Program L i s t i n g K DR 3,0 SEND BYTE TO DISPLAY AHI 4,1 A HI 1,1 CLHR 1,2 DONE ? BL DISLP NO, CONTINUE B 2(15) YES, RETURN (I NTER D AT A ) LHR 0,1 GET ADDRESS OF CURRENT BYTE SH 0,0(15) CALCULATE DECADE FOR DECIMAL OC 3,OUT+5 W DR 3,0 WRITE DECIMAL POINT AHI 2,1 B DECOUT- 14 CONTINUE POINT EJECT * a t e * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 'SWITCH* CALLED BY 'ROUTINE* VIA R10 * * * ***************$*********************************************** SPACE 1 2,ESW 2,1 2,8 * + 8 2, 1 5 , 10 2,2 LB SHI CLHI BL LHI LHR AHR BNP LH LHI OC WDR STH BAL DS BR SPACE LM STM LB OHI STH L H I LUX LH BAL LHI B SPACE DC DC S H OW 14, POS (2) 15 ,5 3,OUT+5 3,15 1 4 , * + 8 15, DISPL H 5 1 14 14 ,BUFF1+2 ,SHOWAREA+4 15,BUFF 1 + 1 15,X'0A00« OVER-WRITE 15,S HOK ARE A + 2 14,SHOWAREA +1 15,SHOWAREA+7 1 1 ,TTYDSR 1 0 ,OUPT 14,BUFF 1 + 1 BIGPOS-10 1 A (FU F F1 + 1 ) P 1 : A(bUFF1 + 1) P2: MOVE TO FORMAT AREA SIGN WITH LINE FEED TART OF TEXTTO BE PRINTED FILT ERED FILTERED POINT/PRINT POINT A p p e n d i x F 157 Program L i s t i n g DC A (RATI01 + 1) P3: FIRST RATIO DC A (RATI02+ 1) P4: SECOND RATIO DC A(NRATIO+1) P5: N 0 R Ii. 2ND RATIO DC A (RATI03+1) P6: THIRD RATIO DC A (ZERO) DC A (RATI04+1) P8: FOURTH RATIO DC X« OAOD' DS 3H SHOWAHEA EJECT ********************************** * * * 'FILTER' CALLED BY 'ROUTINE• VIA R10 * * * *************************************************************** FILTER FILREGS PT R 1 PTR2 PTR3 SPACE 1 LH 1 4 , S W CHECK FOR SHUNT CHANGE NIII 14 ,3 BZ FILR EGS + 6 BRANCH AROUND RESET LM 13, FILR EGS STH 1,0(13) BXLE 13 ,*-4 B SUPERVIS SKIP FILTER ARITHMETIC DC A (WSPI ) STAR? OF FILTER REGION DC H« 2' INCREMENT DC A (VIS P3 + 8) END OF REGION LHI 14,PTR1+2 LH 5 , X» 0DC0 « A (FILTER ROUTINE) BALR 15,5 THREE POINT FILTER DC A (w'S P1 ) DC A ( WSP 1+6) DC H' 02 ' KEEP EVERY SECOND POINT DS H LH R 15,15 BNZ SUPERVIS SPACE 2 LHI 14,PTR2+2 BALR 15,5 TWO POINT FILTER DC A (WSP 2) DC A(WSP2+4) DC H ' 01 • KEEP ALL POINTS DS II SPACE 2 LHI 14 ,PTR3 + 2 BALR 15,5 FIVE POINT FILTER DC A (WS P3) DC A (WSP3+10) DC H' 02 ' KEEP EVERY SECOND POINT DS H LHR 15,15 BNZ SUPERVIS 158 Appendix F Program L i s t i n g SPACE 2 ADDN LH 15,NFPTS AHI 15,1 STH 15,NFPTS BE 10 SPACE 4 WSP1 DS 7H WSP2 DS 3H WSP3 DS 5H SPACE 6 ***************************************** ********************** * * * LIBRARY ROUTINES OF GENERAL USE * * * *************************************************************** SPACE 1 INPT INPT 2,98A49400 SPACE 6 SIBTOD BTOD SPACE 6 READ M SR D SPACE 6 SILTOB DTOB SPACE 6 OUPT STM 14,12(11) LH 14,16 (11) LHI 15,X »0058 • OCR 14,15 BR 10 SPACE 6 MAINSAVE DS 17H NI L DC H» 0 • RT FiiPO DS H R TEMP 1 DS H RT EMP 2 DS H RTSMP3 DS H RTEMP4 DS H R TEMP 5 DS H RTIMP 6 DS H RTEMP7 DS H CRUDE DS 5H NFPTS DS H NK AX DS H MA X DS 32H SHKAX DS 32C I MAX DS 32H BHD DS 10H BLO DS 10H BHD DS 10H END OUTPUT TO :r:?iA TELETYPE MAIN SAVE AREA FOR SUBROUTINES 159 APPENDIX G K-AR METHOD (1.) The techniques used f o r potassium and argon analyses are those i n common use i n many K-Ar l a b o r a t o r i e s (Dalrymple and Lanphere, 1969? White et a l . , 1 9 6 7 ) . (2 . ) Potassium concentrations were determined u s i n g the flame photometer and analyses were c a r r i e d out at l e a s t i n t r i p l i c a t e f o r a l l samples to be dated. (3.) An o r i f i c e or f r a c t i o n a t i o n c o r r e c t i o n was a p p l i e d to the Ar4o/Ar36 and Ar4o/Ar38 measured r a t i o s . (4 . ) The f o l l o w i n g constants were usedi Abundances of isotopes Ar40 99.600 % i n atmospheric argon Ar38 O .O63 % Ar36 0 . 0 3 7 % Abundances of isotopes Ar40 0 .500 $ i n spike argon Ar38 99.493 % A r 3 6 0 . 0 0 7 % Atomic abundance of K40 K 4 0 / K t o t a l = 1.19*10-^ mole/mole Decay constants of K40 x e = 0 .584 * io-i°/yr. fy= 4 . 7 2 * i o - 1 0 / y r . (5 . ) The f o l l o w i n g f a c t o r s were m u l t i p l i e d by the o r i f i c e -c o r r e c t e d i s o t o p i c r a t i o s to compensate f o r the f a c t 160 that U.B.C. analyses of muscovite P-207 give a s l i g h t l y d i f f e r e n t age than other laboratories (J. Harakal, 1974, personal communication)s f a c t o r f o r 40/38 = 0.9917 fa c t o r f o r 40/36 = 0.9834 161 APPENDIX H DETAILED EXPERIMENTAL DATA SOLID SOURCE MASS SPECTROMETRY Summary o f D a t a The f o l l o w i n g i s a summary o f d a t a p r e s e n t e d i n T a b l e s H - l and H - 2 i (2 . ) Dates p e r f o r m e d - March 6, 1974 t o June 11 , 1974 (3 . ) Rubidium c o r r e c t i o n was l e s s t h a n 0.05% f o r 45 out o f 50 r u n s . * WR = whole r o c k sample BT = b i o t i t e sample KF = p o t a s s i u m f e l d s p a r sample SRM = s t a n d a r d r e f e r e n c e m a t e r i a l sample (1 . ) 50 Runs 21 WR* a n a l y s e s 6 BT a n a l y s e s 8 KF a n a l y s e s 1 B l a n k a n a l y s e s 14 SRM 987 a n a l y s e s ( o f which 2 are s p i k e c a l i b r a t i o n s ) 162 Run No. S p i k e d Sample D e s c r i p t i o n Date© 1974 M. S* Scans Used Scans Re j e c t e d Mean R a t i o * * ( S r 8 7 / S r 8 6 ) N 1 no SRM 987 #5 3/06 3 41 12 0.71009 2 no B7-3.WR 3/11 3 37 0 0.71346 3 no B8,WR 3/16 3 34 20 0.71712 4 no B7-1.WR 3/18 3 47 9 0.71332 5 no SRM 987 #9 4/03 3 28 15 0.71017 6 no SRM 987 #10 4/04 3 30 4 0.71008 7 no SRM 987 #6 4/06 3 51 7 0.71016 8 yes SRM 987 #1 S p i k e c a l # l 4/06 3 27 14 O.7098O 9 no B12.WR 4/18 2 33 2 0.71992 10 no B11,WR 4/19 2 20 1 0.71608 11 no B3,WR 4/19 2 17 3 0.71203 12 no B6-3A.WR 4/20 2 15 0 0.71517 @ Date i n the form month/day * M.S. = Mass S p e c t r o m e t e r used ** mean n o r m a l i z e d r a t i o c o r r e c t e d f o r Rb i n sample TABLE H - l t D a t a from mass s p e c t r o m e t e r runs completed f o r t h i s s t u d y . A l l a n a l y s e s were done by the a u t h o r e x c e p t f o r nos, 44-50 done by P. L. LeC o u t e u r . 163 Run No. S p i k e d Sample D e s c r i p t i o n Date 1974 M.S. Scans Used Scans R e j e c t e d Mean R a t i o ( S r 8 7 / S r 8 6 ) N 13 no Rl-T-1,WR 4/23 2 16 0 0.71456 14 no B2-1,WR 4/29 2 15 0 0.71453 15 no B6-1.WR 4/30 2 15 0 0.70862 16 no B6-2.WR 5/03 2 15 0 0.71182 17 no B7-2,WR 5/04 2 16 0 0.71307 18 no SRM 987 #25 5/09 2 15 12 0.71014 19 no B9, WR 5/09 2 15 0 0.71472 20 no B5-1,WR 5/10 2 1.5 0 O.73IO8 21 no B8, WR 5/11 2 15 0 0.71693 22 no B10,WR 5/12 tC 18 0 0.71489 23 no B6-3.WR 5/13 2 14 2 0.71435 24 no B12,KF 5/14 2 20 1 0.72154 25 no B2-1,KF 5/15 2 8 1 0.71544 26 no B6-3A.KF 5/17 2 13 5 0.71742 27 no R5-2.WR 5/20 2 17 4 0.71665 28 no B13,WR 5/21 2 21 i 0.71066 29 yes SRM 988 o n l j B l a n k 5/22 2 5 0 Assumed 0.7120 30 no B6-3.KF 5/24 2 12 4 0.71598 31 no B2-1.KF 5/25 2 18 ' 1 0.71580 TABLE H - l ( c o n t . ) t D a t a from mass s p e c t r o m e t e r r u n s . 164 Run No. S p i k e d Sample D e s c r i p t i o n Date 1974 M.S. Scans Used Scans Re j e c t e d Mean R a t i o ( S r 8 7 / S r 8 6 ) N 32 no B7-2,KF 5/27 2 15 0 0 .71344 33 no B6 -3,KF 5/28 2 10 0 0 .71399 34 no B8,KF 5/29 2 15 0 0.71822 35 yes B2-1.BT 5/29 2 16 0 0.76940 36 yes B6-3,BT 5/31 2 16 0 0.84069 37 yes B8,BT 6/01 2 18 0 0.74578 38 yes B12.BT 6/02 2 12 0 0.78867 39 yes B7-2,BT 6/02 2 20 0 0.74848 40 yes B6-3A.BT 6/03 2 16 0 0.90728 41 no R5-T.WR 6/03 2 16 0 0 .71543 42 no B7-2,WR 6/04 2 15 1 0 .71126 43 yes SRM 987 #22 Spi k e cal#2 6/05 2 11 0 0.71052 44 no SRM 987 #11 4/02 2 16 0 0 .71006 45 no SRM 987 #12 4 /03 2 18 0 0.70972 46 no SRM 987 #13 4/04 2 21 1 0 .71002 47 no SRM 987 #13 4/08 2 18 1 0.71015 48 no SRM 987 #14 4/16 2 8 1 0 .71026 49 no SRM 987 #17 4/17 2 15 0 0 .71052 50 no SRM 987 #19 6/11 2 17 0 0.71008 TABLE H - l ( c o n t . ) > D a t a from mass s p e c t r o m e t e r r u n s . 165 Run Mean Ratio© I s * * * 2 s m * * % E r r o r a t R b 8 7 / S r 8 6 * No. (Sr8?/Sr86)N 2 s m L e v e l C o r r e c t i o n s 1 0 . 7 1 0 0 9 0 . 0 0 0 9 3 0 . 0 0 0 3 0 0.041 0 . 0 0 3 5 - 0 . 0 0 8 0 2 0 . 7 1 3 ^ 6 O .OOO67 0 . 0 0 0 2 2 0 . 0 3 1 0 . 0 0 0 7 5 - 0 . 0 0 2 1 3 0 . 7 1 7 1 2 0 . 0 0 0 7 0 0.00024 0 . 0 3 3 O.OOO35-O.OOIO 4 0 . 7 1 3 3 2 0 . 0 0 1 1 6 0 . 0 0 0 3 4 0 . 0 4 7 0 . 0 0 0 8 5 - 0 . 0 0 3 1 5 5 0 . 7 1 0 1 7 0 . 0 0 0 5 6 0 . 0 0 0 2 0 0 . 0 3 0 0 . 0 0 0 0 6 0 . 7 1 0 0 8 0 . 0 0 0 5 4 0 . 0 0 0 2 0 0.028 0 . 0 0 0 2 - 0 . 0 0 0 5 7 0 . 7 1 0 1 6 0 . 0 0 1 2 9 0 . 0 0 0 3 6 0 . 0 5 1 O . 0 0 0 5-O . O O 1 1 5 8 O . 7 0 9 8 O 0 . 0 0 0 8 4 0 . 0 0 0 3 2 0.046 0 . 0 0 0 1 5 - 0 . 0 0 1 0 5 9 0 . 7 1 9 9 2 0 . 0 0 0 8 8 0 . 0 0 0 3 1 0.042 0 . 0 0 0 3 5 - 0 . 0 0 0 5 5 10 0 . 7 1 6 0 8 O.OOO66 0 . 0 0 0 3 0 0.041 0 . 0 0 0 5 - 0 . 0 0 1 6 5 11 0 . 7 1 2 0 3 0 . 0 0 0 5 9 0.00028 0.040 0 . 0 0 0 5 5 - 0 . 0 0 1 2 12 0 . 7 1 5 1 7 0.00018 0 . 0 0 0 1 0 0 . 0 1 3 0 . 0 0 0 1 @ mean n o r m a l i z e d r a t i o c o r r e c t e d f o r Rb i n sample *** one s t a n d a r d d e v i a t i o n f o r the p o p u l a t i o n ** two s t a n d a r d d e v i a t i o n s o f the mean - 9 5 . 4 5 % c o n f i d e n c e l i m i t s f o r the mean * range i n R b 8 7 / S r 8 6 c o r r e c t i o n s a p p l i e d t o measured unnormal-i z e d 8 7 / 8 6 r a t i o s f o r scans used i n an i n d i v i d u a l r u n TABLE H-2t S t a t i s t i c s f o r ( S r 8 7 / S r 8 6 ) N r a t i o s c a l c u l a t e d f o r mass s p e c t r o m e t e r runs d e s c r i b e d i n T a b l e H - l . The p o p u l a t i o n s i z e f o r each r u n i s the number o f scans used. 1 66 Run No. Mean R a t i o ( S r 8 7 / S r 8 6)N I s 2 s m % E r r o r a t 2 s m L e v e l R b 8 7 / S r 8 6 C o r r e c t i o n s 13 0 . 7 1 4 5 6 0 . 0 0 0 2 9 0.00014 0 . 0 2 0 0 . 0 0 0 1 5 - 0 . 0 0 0 2 5 14 0 . 7 1 4 5 3 0 . 0 0 0 1 9 0 . 0 0 0 1 0 0.014 0 . 0 0 0 1 15 0 . 7 0 8 6 2 0 . 0 0 0 2 2 0 . 0 0 0 1 2 0 . 0 1 6 0 . 0 0 0 2 5 - 0 . 0 0 0 7 5 16 0 . 7 1 1 8 2 0.00018 0 . 0 0 0 1 0 0 . 0 1 3 0 . 0 0 0 2 17 0 . 7 1 3 0 7 0 . 0 0 0 2 7 0.00014 0 . 0 1 9 0 . 0 0 0 5 - 0 . 0 0 0 5 5 18 0 . 7 1 0 1 4 0 . 0 0 0 5 3 0 . 0 0 0 2 8 0 . 0 3 8 0 . 0 0 0 1 5 - 0 . 0 0 0 2 19 0.71472 0 . 0 0 0 1 7 0.00008 0 . 0 1 2 0 . 0 0 0 2 - 0 . 0 0 0 2 5 20 0 . 7 3 1 0 8 0 . 0 0 0 3 1 0 . 0 0 0 1 6 0 . 0 2 2 0 . 0 0 2 8 - 0 . 0 0 3 3 5 21 0 . 7 1 6 9 3 0 . 0 0 0 2 9 0.00014 0 . 0 2 1 0 . 0 0 0 3 5 - 0 . 0 0 0 4 5 22 0 . 7 1 4 8 9 0 . 0 0 0 5 3 0 . 0 0 0 2 6 0 . 0 3 5 0.0014 - 0 . 0 0 1 6 5 23 0 . 7 1 4 3 5 0 . 0 0 1 0 9 0 . 0 0 0 5 8 0 . 0 8 2 0 . 0 0 1 1 - 0 . 0 0 2 6 5 ' 24 0 , 7 2 1 5 4 0 . 0 0 0 9 2 0 . 0 0 0 4 2 0 . 0 5 7 0 . 0 0 1 2 5 - 0 . 0 0 1 4 5 25 0 . 7 1 5 4 4 0 . 0 0 1 3 5 0 . 0 0 9 6 0 . 1 3 4 0 . 0 0 9 6 - 0 . 0 1 4 7 5 26 0 .71742 0 . 0 0 0 7 8 0 . 0 0 0 4 4 0 . 0 6 1 0 . 0 0 1 6 5 - 0 . 0 1 2 3 5 27 0 . 7 1 6 6 5 0 . 0 0 0 5 8 0.00028 0 . 0 3 9 0 . 0 0 0 2 5 28 0 . 7 1 0 6 6 0 . 0 0 0 4 6 0 . 0 0 0 2 0 0 . 0 2 8 0 . 0 0 0 9 5 - 0 . 0 0 1 1 30 0 . 7 1 5 9 8 0 . 0 0 0 5 6 0 . 0 0 0 3 2 0 . 0 4 5 0 . 0 0 0 1 5 - 0 . 0 0 0 2 5 31 0 . 7 1 5 8 0 0 . 0 0 0 2 5 0 . 0 0 0 1 2 0 . 0 1 6 0 . 0 0 0 2 - 0 . 0 0 0 2 5 32 0 , 7 1 3 4 4 0 . 0 0 0 5 6 0.00028 0.040 0 . 0 0 0 7 - 0 . 0 0 1 1 5 TABLE H - 2 ( c o n t . ) \ S t a t i s t i c s f o r ( S r 8 7 / S r 8 6 ) N r a t i o s . 167 Run No. Mean R a t i o ( S r 8 7 / S r 8 6 ) N I s 2 s m % E r r o r a t 2 s m L e v e l R b 8 7 / S r 8 6 C o r r e c t i o n s 33 0 . 7 1 3 9 9 0.00182 0 . 0 0 1 1 6 0 . 1 6 0 0 . 0 0 9 9 5 - 0 . 0 1 5 4 34 0 . 7 1 8 2 2 0 . 0 0 0 4 7 0.00024 0 . 0 3 4 0 . 0 0 0 3 - 0 . 0 0 0 5 5 35 0 . 7 6 9 4 0 0 . 0 0 0 4 3 0 . 0 0 0 2 2 0.028 0 . 0 0 1 0 5 - 0 .0018 36 0 . 8 4 0 6 9 0.00028 0.00014 0 . 0 1 7 0 . 0 0 0 2 - 0 . 0 0 0 5 37 0 . 7 4 5 7 8 0 . 0 0 0 7 9 0 . 0 0 0 3 8 0 . 0 5 0 0 . 0 0 0 1 5 38 O .78867 0 . 0 0 1 0 3 0 . 0 0 0 6 0 0 . 0 7 5 0 . 0 0 1 0 - 0 . 0 0 9 6 39 0.74848 0 . 0 0 0 5 0 0 . 0 0 0 2 2 0 . 0 3 0 0 . 0 0 0 8 - 0 . 0 0 1 8 5 40 0.90728 0 . 0 0 1 0 9 0 . 0 0 0 5 4 0 , 0 6 0 0 . 0 0 1 8 5 - 0 . 0 0 3 3 5 41 0 . 7 1 5 4 3 0 . 0 0 0 3 1 0 . 0 0 0 1 6 0 . 0 2 1 0 . 0 0 0 1 42 0.71126 0 . 0 0 0 6 9 0 . 0 0 0 3 6 0 . 0 5 0 0 . 0 0 0 2 5 - 0 . 0 0 0 3 5 43 O .71052 0 . 0 0 0 5 7 0 . 0 0 0 3 4 0.049 0 . 0 0 0 6 - 0 . 0 0 0 7 5 44 0 . 7 1 0 0 6 0 . 0 0 0 5 3 0 . 0 0 0 2 6 0.040 0 . 0 0 0 0 45 0 . 7 0 9 7 2 0 . 0 0 0 4 3 0 . 0 0 0 2 0 0 . 0 2 9 0 . 0 0 0 6 - 0 . 0 0 0 8 46 0 . 7 1 0 0 2 0.00146 0 . 0 0 0 6 6 0 . 0 9 2 0 . 0 0 0 0 47 0 . 7 1 0 1 5 0 . 0 0 1 8 9 0 . 0 0 0 9 2 0 . 1 2 9 0 . 0 0 0 0 48 0 . 7 1 0 2 6 0 . 0 0 0 1 3 0 . 0 0 0 1 0 0.014 , 0 . 0 0 0 3 49 0 . 7 1 0 5 2 0 . 0 0 1 1 0 0 . 0 0 0 5 6 0 . 0 8 0 0 . 0 0 0 0 50 0 . 7 1 0 0 8 0 . 0 0 0 5 7 0.00028 0 . 0 3 8 0.0004 TABLE H - 2 ( c o n t . ) t S t a t i s t i c s f o r ( S r 8 7 / S r 8 6 ) N r a t i o s . 168 S p i k e and S t a n d a r d C a l i b r a t i o n s S p i k e used N a t i o n a l Bureau o f S t a n d a r d s (NBS) S t a n d a r d R e f e r e n c e M a t e r i a l No. 988, S t r o n t i u m - 84 S p i k e (SRM 988) S t a n d a r d used NBS S t a n d a r d R e f e r e n c e M a t e r i a l No. 987, S t r o n t i u m Carbonate (SRM 987) Both s p i k e and s t a n d a r d s o l u t i o n s were p r e p a r e d by the w r i t e r w i t h the a i d o f R.L. Arm s t r o n g . The s t a n d a r d SRM 987 S r c o n c e n t r a t i o n was c a l c u l a t e d from d a t a r e c o r d e d d u r i n g the p r e p a r a t i o n p r o c e s s ( i . e . , w e i g h t s o f sample and l i q u i d added, volume o f the c o n t a i n e r , e t c . ) p l u s d a t a from the NBS C e r t i f i c a t e o f A n a l y s i s . The s p i k e SRM 988 Sr84 c o n c e n t r a t i o n was d e t e r m i n e d i n two waysi (1) A c a l c u l a t i o n was made s i m i l a r t o t h a t d e s c r i b e d above f o r SRM 987. (2) D u r i n g t h e course o f the mass s p e c t r o m e t e r work two samples o f SRM 987 s p i k e d w i t h SRM 988 were r u n , one each on M.S.2 and M.S.3. The c o n c e n t r a t i o n s o f s p i k e which b e s t d e t e r m i n e d the known concen-t r a t i o n o f S r i n SRM 987 (as c a l c u l a t e d above) were t h e n d e t e r m i n e d . An o v e r a l l ' b e s t ' Sr84 c o n c e n t r a t i o n was t h u s f o u n d . T h i s v a l u e i s 0.01128 m i c r o m o l e s Sr84/gram o f s p i k e s o l u t i o n and has been used f o r a l l s p i k e d runs i n t h i s s t u d y . P e r t i n e n t d a t a f o r the SRM 987 and SRM 988 s o l u t i o n s used are summarized i n Ta b l e H-3. 169 (1.) SRM 98? Standard s o l u t i o n was prepared February 13» 1974 Sr concentration = ( 1 0 0 . 0 ^ 0 - 0 7 ? 4*. 3 r ml. of s o l u t i o n (100.2 5 + 0 . 0 7 ) / ^ . Sr g. of s o l u t i o n Molecular weight of Sr = 87.616 S r 8 6 concentration = (0.1129+0. 0001 ) A m o l e s S r 8 6 g. of s o l u t i o n S r 8 ? / 3 r 8 6 i s o t o p i c composition (normalized to S r 8 6 / S r 8 8 = 0.1194) from NBS C e r t i f i c a t e of Analysis = 0.71014+0.00020 ( 9 5 % confidence l i m i t s ) (2.) SRM 988 (a) Spike s o l u t i o n was prepared February 13» 1974 Sr concentration = ( 0 . 9 4 6 7 + 0 . 0 0 0 6 ) ^ . Sr ml. of s o l u t i o n = (0.9486+0.0006)yug. Sr gT of s o l u t i o n Molecular weight of Sr = 83.9165 c o n c e n t r a t i o n . ( 0 . 0 1 1 2 9 t o . 00001 ) ^ o l e s Sr84 (b) Spike c a l i b r a t i o n #1 (see data f o r run no. 8) Date of analysis = A p r i l 7, 1974 on M.S.3 Sr84 concentration which provides the best f i t f o r + H O Q T ? W I QOO _ (0.01127+0.OOOODyUmoles Sr84 the SRM 987 data q £ s o l u ( i o n  TABLE H-3» Data f o r the standard (SRM 987) and spike (SRM 988) solutions used f o r t h i s study. Uncertainties quoted are estimated possible errors unless otherwise indicated. 170 TABLE H-3 ( c o n t . ) t (c) Spike c a l i b r a t i o n #2 (see data f o r run no. 43) Date of a n a l y s i s = June 5 , 1974 on M.S.2 Sr84 c o n c e n t r a t i o n which provides the best f i t f o r +v,o CRM o « o - (0.01126+0.00001) yttmoles Sr84 the SRM 987 data - g. of s o l u t i o n Blank A n a l y s i s One blank was analyzed during the experimental work. The blank sample was spiked before d i s s o l u t i o n and run through the same chemical p r e p a r a t i o n as a l l other samples. I t was assumed to be composed of common Sr and y i e l d e d a contamination of 0.05 micrograms of t o t a l Sr. This i s n e g l i g i b l e f o r a l l whole rock and potassium f e l d s p a r samples run as gr e a t e r than 40 micrograms of t o t a l Sr was d i s s o l v e d i n each case. For b i o t i t e samples, g r e a t e r than 20 micro-grams of t o t a l Sr was d i s s o l v e d ; thus, a contamination of 0.05 micrograms of common Sr i s only s u f f i c i e n t i n the worst case (sample B6-3A) to change the r e s u l t i n g Sr87/Sr86 r a t i o by 0.0595. Data R e j e c t i o n Table H-4 l i s t s the o v e r a l l data r e j e c t i o n s t a t i s t i c s f o r M.S.2 and M.S.3. Data was r e j e c t e d when unstable c o n d i t i o n s were recognized d u r i n g a mass spectrometer run. 171 C r i t e r i a f o r i n s t a b i l i t y were e s t a b l i s h e d by t h e o p e r a t o r f o r t h e mass s p e c t r o m e t e r c o n c e r n e d and were a p p l i e d t o a l l r u n s . These i n c l u d e d * (1) peaks d e c a y i n g t o o f a s t , (2) peak h e i g h t s t o o s m a l l , (3) Rb85 peak i n c r e a s i n g , (4) Rb85 peak d e c r e a s i n g but s t i l l above a h e i g h t c o r r e s p o n d i n g t o the a c c e p t a b l e l e v e l o f Rb c o n t a m i n a t i o n . The r e l a t i v e change o f peak h e i g h t p e r u n i t time f o r each s e t o f peaks ( i . e . , downmass and upmass) measured d u r i n g one s c a n was a l s o m o n i t o r e d . T h i s q u a n t i t y was u s e f u l i n p o i n t i n g out when s t a b i l i t y problems had o c c u r r e d . D e s c r i p t i o n M.S.2 M. S. 3 T o t a l s scans u sed 688 268 956 scans r e j e c t e d 41 81 122 scans t a k e n 729 349 1078 % o f d a t a r e j e c t e d 5.W 23.2% 11.3% TABLE H-4> O v e r a l l d a t a r e j e c t i o n s t a t i s t i c s . A t l e a s t some d a t a was r e j e c t e d f o r 23 out o f 50 (46%) of t h e runs p e r formed. Problems w i t h M.S.3 are d i s c u s s e d i n Appendix C, 172 P r e c i s i o n and Accuracy-T a b l e H - 5 i s a summary o f a n a l y t i c a l p r e c i s i o n . C o n s i d e r i n g a l l a n a l y s e s p e r f o r m e d f o r t h i s s t u d y , % e r r o r a t the 2 s m l e v e l v a r i e d f rom 0 . 0 1 2 % t o 0 . 1 6 0 % . B l e n k i n s o p ( 1 9 7 2 ) used a p r e c i s i o n o f 0 . 0 2 % f o r a l l a n a l y s e s r e p o r t e d i n h i s s t u d y . The w r i t e r c o n s i d e r s 0 . 0 2 % as the r e a l i s t i c a l l y b e s t p r e c i s i o n o b t a i n a b l e on t h e s o l i d s o u r c e mass s p e c t r o -m eters a t U.B.C. Thus, t h e p r e c i s i o n o f the S r 8 7 / S r 8 6 r a t i o s u sed f o r each sample f o r i s o c h r o n c a l c u l a t i o n s (see C h a p t e r IV) was d e t e r m i n e d as f o l l o w s t ( 1 ) I f t h e p r e c i s i o n o f an a n a l y s i s was l e s s t h a n 0 . 0 2 % a t t h e 2 s m l e v e l , 0 . 0 2 % was used. ( 2 ) I f the p r e c i s i o n o f an a n a l y s i s was g r e a t e r t h a n 0 . 0 2 % a t the 2 s m l e v e l , t h a t p r e c i s i o n was used. (3) I f two o r more a n a l y s e s were made o f t h e sample, a w e i g h t e d average o f the r e s p e c t i v e S r 8 7 / S r 8 6 r a t i o s was c a l c u l a t e d and a r e s u l t i n g w e i g h t e d s t a n d a r d d e v i a t i o n o f the mean d e t e r m i n e d . T h i s s t a n d a r d d e v i a t i o n was used t o c a l c u l a t e a p r e c i s i o n w hich was c o n s i d e r e d i n e i t h e r o f c a t e g o r i e s ( 1 ) o r ( 2 ) above. The w e i g h t i n g f u n c t i o n used was the i n v e r s e - s q u a r e d s t a n d a r d d e v i a t i o n o f t h e mean f o r each r u n (see Appendix I ) . 173 Group C o n s i d e r e d No. o f Runs Average % E r r o r a t 2 s m L e v e l WR a n a l y s e s 21 0.030 BT a n a l y s e s 6 0.043 KF a n a l y s e s 8 0.068 SRM 987 a n a l y s e s 14 0.050 a l l a n a l y s e s 49 0.044 s p i k e d a n a l y s e s 8 0.044 u n s p i k e d a n a l y s e s 41 0.044 M.S.2 a n a l y s e s 41 0.045 M.S.3 a n a l y s e s 8 0.038 TABLE H-5* Summary o f a n a l y t i c a l p r e c i s i o n i n i n d i v i d u a l r u n s . I t i s i m p o r t a n t t o note t h a t t h e number o f scans p e r r u n was a t l e a s t double f o r M.S.3 r u n s i n o r d e r t o o b t a i n a comparable p r e c i s i o n w i t h M.S.2 r u n s . D u p l i c a t e a n a l y s e s o f s e v e r a l samples, i n c l u d i n g a few o f B l e n k i n s o p ' s (1972), are shown i n Tab l e H -6 . These a n a l y s e s are a more s t r i n g e n t t e s t o f p r e c i s i o n s i n c e t h e y i n c l u d e s e p a r a t e c h e m i c a l p r e p a r a t i o n o f samples. Three s e t s o f d u p l i c a t e s show l a r g e d i s c r e p a n c i e s . S i n c e a n a l y s e s 42, 33» and 41 a l l i n v o l v e d samples i n c l u d e d i n the same c h e m i c a l p r e p a r a t i o n b a t c h , t h e y were r e j e c t e d . The cause o f t h e low r a t i o s was assumed t o be c o n t a m i n a t i o n . The o t h e r f o u r s e t s o f d u p l i c a t e s agree w e l l w i t h i n s t a t e d 174 Sample Run No. Mean R a t i o ( S r 8 7 / S r 8 6 ) N 2 s m B8.WR 3 21 0.71712 0.71693 0.00024 0.00014 w e i g h t e d averages t 0.71698 0.00012 B2-1,KP 25 31 0.71544 0.71580 0.00096 0.00012 w e i g h t e d averages » 0.71579 0.00012 Rl-T-l/WR 13 JB JB 0.71456 0.7148 0.7149 0.00014 0.00014 0.00014 w e i g h t e d averages i 0.71475.. 0.00008 R5-2,WR • 27 JB O.71665 0.7170 0.00028 0.00014 w e i g h t e d averages t 0.71693 0.00012 B7-2,WR 17 O.71307 0.71126 0.00014 0.00036 B6-3.KF 30 0.71598 0.71399 0.00032 0.00116 R5-T,WR 41 * JB O.71543 0.7168 0.00016 0.00014 JB a n a l y s i s f r om B l e n k i n s o p (1972) * . a n a l y s i s not used TABLE H-6> D u p l i c a t e a n a l y s e s o f s e v e r a l whole r o c k and p o t a s s i u m f e l d s p a r samples. A c o m p a r i s o n w i t h some r e s u l t s o f B l e n k i n s o p (1972) i s shown. 175 p r e c i s i o n . R e p l i c a t e a n a l y s e s o f an i n t e r - l a b o r a t o r y s t a n d a r d , SRM 987» are shown i n T a b l e H-7. T h e i r average agrees v e r y w e l l ( w i t h i n 0.01%) w i t h the a c c e p t e d v a l u e o f Sr87/Sr86 i n SRM 987.. X-RAY FLUORESCENCE D e t a i l e d XRF Rb and S r c o n c e n t r a t i o n r e s u l t s are l i s t e d i n T a b l e H-8. T a b l e H-9 compares a n a l y s e s made by t h e w r i t e r o f s e l e c t e d samples o f B l e n k i n s o p ' s (1972) w i t h r e s u l t s r e p o r t e d i n B l e n k i n s o p (1972). D i s c r e p a n c i e s are w e l l w i t h i n the r e p o r t e d p r e c i s i o n (see Appendix D) of the method. Ta b l e H-10 compares XRF S r a n a l y s e s o f s i x b i o t i t e samples w i t h s p i k e d S r a n a l y s e s o f the same samples on M.S.2. The Rb/Sr w e i g h t r a t i o s used t o d e t e r m i n e Rb87/Sr86 r a t i o s (see C h a p t e r IV) f o r t h e s e s i x b i o t i t e samples were c a l c u l a t e d u s i n g XRF Rb r e s u l t s and M.S.2 S r r e s u l t s . 176 Run No. A l i q u o t No. Mean R a t i o ( S r 8 7 / S r 8 6 ) N 2 s m 18 25 0.71014 0.00028 43 22 0.71052 0.00034 44 11 0.71006 0.00026 45 12 0.70972 0.00020 46) 47 i 13 0.71008* 0.00056* 48 14 0.71026 0.00010 49 17 0.71052 0.00056 50 19 0.71008 0.00028 w e i g h t e d a v e r a g e s t 0.71016 0.00007 1 5 0.71009 0.00030 5 9 0.71017 0.00020 6 10 0.71008 0.00020 7 6 0.71016 0.00036 8 1 0.70980 0.00032 w e i g h t e d averages a 0.71008 0.00011 w e i g h t e d averages o f runs 46 and 47 TABLE H-7» R e p l i c a t e measurements o f SRM 987 s t a n d a r d . I t s a c c e p t e d Sr87/Sr86 i s o t o p i c c o m p o s i t i o n i s 0.71014+0.00020 (2s n). 177 Sample Sample D e s c r i p t i o n Rb(ppm) Sr(ppm) Weight R a t i o Rb/Sr Average Rb/Sr C l a c h n a c u d a i n n g n e i s s samples 1 Bl-l.WR 1 • * TC 111.0 235.8 0.4654 0.465 Bl - 1,BT 1 * TC 633.5 51.9 12.78 12.5 625.8 51.1 12.25 B2-1,WR 1 * TC 95.6 244 . 3 0.3913 0.390 2 * 95.2 245.3 0.3881 B2-1.BT 1 * TC 737.5 33.4 22.08 22.4 \ ** 746 . 2 • 32.9 22.68 B2 -1.KF 1 * TC 252.0 287.9 0.8753 O.876 1 * 253.0 288 . 0 0.8785 \ #"* 248 . 9 285 . 3 0.8724 1 ** 247 . 3 284 . 4 0.8695 2 * 254.8 288 . 5 0.8832 B3,WR 1 * TC 61.2 254.2 0.2408 0.241 B3,BT 1 * TC 445.9 42 . 2 10.57 10.4 440.1 42 . 9 10.26 B4-X,WR 1 * TC 66.0 291.6 0.2263 0.226 B4-X,BT 1 * TC 451.1 40 . 4 11.17 11.0 1 #* 444.3 40 . 9 10.86 B4-Y,WR 1 * TC 75.2 277.9 0.2706 0.271 2 * 75 .3 277.8 0.2711 B4-Y,BT 1 * TC 524.8 24 . 2 21.69 21.4 1 520.2 24 . 6 21.15 TABLE H-8t XRF Rb and S r c o n c e n t r a t i o n r e s u l t s . 1 = f i r s t p e l l e t 2 = second p e l l e t * = December 8 , 1973 a n a l y s i s ** = F e b r u a r y 9, 1974 a n a l y s i s TC = Trans-Canada Highway sample LA = L a Forme Creek sample BB = Big-Bend Highway sample 1?8 Sample Sample D e s c r i p t i o n Rb(ppm) Sr(ppm) Weight R a t i o Rb/Sr Average Rb/Sr B6-1.WR 1 * TC 4 9 . 7 3 4 6 . 6 0.1434 0.143 B6-1,BT 1 * TC 361.2 27.7 13.04 13.0 360.7 27.9 12.93 B6-2.WR 1 * TC 8 4 . 7 2 8 6 . 8 0.2953 0.296 2 * 85.9 289.0 O .2972 B6-2.BT 1 * TC 666.7 26.9 24 . 7 8 2 4 . 6 1 661.6 27.0 24 . 5 0 B6-2.KF 1 * TC 200.5 365.1 0.5492 0.545 1 * 208.9 381.0 0.5483 1 * 2 0 8 . 4 382.4 0.5450 1 * * 2 0 4 . 6 379.6 0.5390 B6-3.WR 1 * TC 94.1 211.6 0.4447 0.445 . 2 * 94.0 . 211.1 0.4453 B6 -3 ,BT' 1 * TC 777.8 1 4 . 3 1 54.39 52.6 1 * 777.3 1 4 . 7 52.88 1 * 779.3 1 4 . 4 54.12 766.3 15.3 50.08 1 •«•# 774.8 15.0 51.65 B6-3.KF 1 * • TC 269.5 326.5 0.8254 0.822 1 ## 273.7 334.5 0.8182 B6-3A.WR 1 * TC 83.3 163.9 0.5082 0.510 2 * 83.6 163.4 0.5116 B6 - 3A,BT 1 * TC 867.4 10.2 85.04 80.3 862.8 11.0 78.44 1 860.0 11.1 77.48 B6-3A.KF 1 *# TC 195.9 2 1 8 . 7 0.8957 0.898 1 196.2 217.9 0.9004 TABLE H-8 (cont.)> XRF Rb and S r c o n c e n t r a t i o n r e s u l t s . 179 Sample Sample D e s c r i p t i o n Rb(ppm) Sr(ppm) Weight R a t i o Rb/Sr Average Rb/Sr B7-1.WR 1 * TC 61.5 230.4 0.2669 0.266 1 * 60.9 230.5 0.2642 1 * 61.6 232.1 0.2654 B 7 - 1 tBT 1 * TC 434.3 16.4 26.48 25.7 430.6 17 .3 24.89 B7-2,WR 1 * TC 57.8 259.9 0.2224 0.222 1 * 57 .5 259.7 0.2214 B7-2.BT 1 * TC 444.3 29 .3 15.16 15.1 1 ## 443.2 29.5 15.02 447.7 29.9 14.97 B7-2,KF 1 * TC 214.8 452.4 0.4748 0.475 1 * 220.5 463.7 0.4755 221.6 466.4 0.4751 B7-3iWR 1 * TC 79.1 264.7 0.2988 0.298 77 .5 262.8 0.2949 2 * 79.9 264.9 0.3016 B7-3.BT 1 * TC 686.7 24.8 27.69 27.4 699.5 25.8 27.11 B8,WR 1 * LA 106.0 218.4 0.4853 0.485 B8,BT 1 * LA 602. 2 42.4 14.20 14.1 I *•«• 593.4 42.4 14.00 B8.KF 1 * LA 161.4 243.6 0.6626 0.659 1 * * 165.1 252.3 0.6544 B9,WR 1 * LA 87.1 264.0 0.3299 0.330 B9,BT 1 * LA 475.5 49.1 9.684 9.58 473.6 50.0 9.472 TABLE H-8 ( c o n t . ) t XRF Rb and S r c o n c e n t r a t i o n r e s u l t s . 180 Sample Sample D e s c r i p t i o n Rb(ppm) Sr(ppm) Weight R a t i o Rb/Sr Average Rb/Sr B10,WR 1 * LA 1 #•* 73.5 72.7 224 . 6 225.0 0.3272 0.3231 0.325 B10.BT 1 * LA 1 ## 415.5 412 . 6 43 .0 42 . 9 9.663 9.618 9.64 B11,WR 1 * LA 89.6 229.9 0.3897 0.390 B l l . B T 1 * LA 500.7 506.1 4 8 . 3 49 .3 10.37 10.27 10.3 B12.WR 1 * LA 1 #* 2 * 98.1 95.9 97.1 121.6 122.0 122.7 O.8067 0.7861 0.7914 0.795 B12,BT 1 * LA \ ** ^ #* 531.9 537.9 531.4 17.9 18 . 2 18 . 4 29.72 29.55 28 . 8 8 29.4 B12,KF 1 * LA 1 * 1 153.9 154.5 151.5 119 . 7 120.1 120.3 1.286 1.286 1.259 1.28 B13.WR 1 * LA 29.9 290.5 0.1029 0.103 G r a n i t i c d i k e samples i G4,WR 1 * TC 54.1 123.7 0.4373 0.437 G6-2.WR 1 * • TC 2 * 253.1 253.8 183 . 8 182 . 7 1.377 1.389 1.38 G6-2,BT 1 * TC 1 #* 1389. 1414. 10.2 11.4 136.2 124 . 1 130. TABLE H-8 ( c o n t . ) 1 XRF Rb and S r c o n c e n t r a t i o n r e s u l t s . 181 Sample Sample D e s c r i p t i o n Rb(ppm) Sr(ppm) Weight R a t i o Rb/Sr Average Rb/Sr G6-2.KF 1 * TG 1 * 1 * * 603.0 613.3 610.8 310.4 316.3 317.0 1.943 1.939 1.927 1.94 Q u a r t z d i o r i t e samples « Bl4,WR 1 * BB 2 * 72.1 72 .3 1649. 1647. 0.04372 0.04389 0.0438 B14,BT 1 * BB 248 . 7 243 . 7 I 6 0 . 9 160.6 1. 544 1.517 1.53 B15.WR 1 * BB 144 . 3 1228. 0.1175 0.118 B15,HB @ 1 * BB 35.8 37.2 70.7 73 .4 0.5064 O.5068 0.507 'Lower l e v e l ' metasediment samples » B5-1,WR 1 * TC 221.1 302.3 0.7314 0.731 B5-1,BT 1 * TC 1 2 * 2 * * 799.2 779.7 821 . 8 793.6 25.8 26.2 25.2 25.5 30.98 29.76 32.61 31.12 31.1 @ HB = ho r n b l e n d e sample TABLE H-8 ( c o n t . ) i XRF Rb and S r c o n c e n t r a t i o n r e s u l t s . 182 Sample Sample Description Rb(ppm) Sr(ppm) Weight Ratio Rb/Sr Average Rb/Sr Blenkinsop (1972) Clachnacudainn gneiss samples t Rl-T-1 -t,WR; R-5-T,WR R5-2,WR 1 * TC 102.8 199.5 0.515 JB 101. 201. 0.502 JB 101. 199. 0.508 1 * LA 86.6 217.1 0.399 \ ** 85.8 218.1 0.393 JB 86.5 217. 0.399 1 * LA 88.0 207.4 0.424 2 * 87.4 209.0 0.418 JB 86.5 210. 0.412 JB 87.2 211. 0.413 JB 8?*4 210. 0.416 0.508 0.397 0.417 JB analyses from Blenkinsop (1972) TABLE H-9> Comparison of XRF results with those of Blenkinsop (1972) . - XRF R e s u l t s M.S.; l R e s u l t s Sample No. o f Measurements Average Sr(ppm) No. o f Scans* Average Sr(ppm) I s 2 s m % E r r o r a t 2 s m L e v e l % D i s c r e p a n c y o f XRF R e s u l t s B12,BT 3 1 8 . 1 7 1 2 1 7 . 9 5 2 0 . 0 8 5 0 . 0 5 0 0 . 2 7 4 + 1 . 2 1 B6-3,BT 5 1 4 . 7 4 1 6 1 4 . 5 5 1 0.028 0.014 0 . 0 9 5 + 1 . 3 0 B6-3A,BT 3 1 0 . 7 7 1 6 1 0 . 7 0 0 0 . 0 3 9 0 . 0 2 0 0.182 + 0 . 6 5 B2-1,BT 2 3 3 . 1 5 1 6 3 1 c 0 6 8 0.043 0 . 0 2 2 0 . 0 6 9 + 6 . 7 0 B7 - 2,BT 3 2 9 . 5 7 2 0 2 9 . 5 1 6 0 . 0 5 7 0 . 0 2 6 0 . 0 8 7 + 0.18 B8, BT 2 4 2 . 4 18 4 3 . 6 2 9 0.143 0 . 0 6 7 0 . 1 5 4 - 2 . 8 2 a b s o l u t e averages 1 0.144 2.14 no scans were r e j e c t e d f o r any sample TABLE H - 1 0 > Comparison o f XRF S r d e t e r m i n a t i o n s w i t h s p i k e d Sr84 mass s p e c t r o m e t r i c S r d e t e r m i n a t i o n s * . 184 GAS SOURCE MASS SPECTROMETRY T a b l e H - l l l i s t s p e r t i n e n t d a t a f o r the seven samples t h a t were d a t e d by the K-Ar method. T a b l e H-12 g i v e s the r e s u l t s o f the argon a n a l y s e s . The b i o t i t e c o n c e n t r a t e s were e s t i m a t e d t o be b e t t e r t h a n 98% p u r e . G r e a t c a r e was t a k e n t o remove a l l b i o t i t e f r om the ho r n b l e n d e c o n c e n t r a t e . Age u n c e r t a i n t i e s were c a l c u l a t e d as f o l l o w s i 2.7% p l u s the % e r r o r a t the l s m l e v e l f o r % K a n a l y s e s ( J . H a r a k a l , 1974, p e r s o n a l c o m m u n i c a t i o n ) . T h i s was d o u b l e d t o g e t t h e 95% c o n f i d e n c e l i m i t s . FLAME PHOTOMETRY P o t a s s i u m a n a l y s e s were pe r f o r m e d by V. B o b i c u s i n g KY and KY - 3 flame p h o t o m e t e r s . A n a l y t i c a l p r o c e d u r e s are d e s c r i b e d i n White e t a l . (1967). T a b l e H-13 l i s t s a l l p o t a s s i u m a n a l y s e s o f m i n e r a l s e p a r a t e s . T a b l e H-14 l i s t s p o t a s s i u m c o n c e n t r a t i o n s and c a l c u l a t e d K/Rb r a t i o s f o r whole r o c k samples. E s t i m a t e d e r r o r i n t h e % K whole r o c k a n a l y s e s was c a l c u l a t e d u s i n g Youden's (1951) e x p r e s s i o n f o r the s t a n d a r d d e v i a t i o n o f m s e t s o f d u p l i c a t e measurements (see Appendix I , e q u a t i o n (3) ). The e s t i m a t e d s t a n d a r d d e v i a t i o n o f 23 s e t s o f d u p l i c a t e whole r o c k % K a n a l y s e s was 0.011. T h i s c o r r e s p o n d s t o about a 1% e r r o r a t t h e 95% c o n f i d e n c e l e v e l . Run No. Sample No. Sample D e s c r i p t i o n * M i n e r a l Dated** No. of % K A n a l y s e s Average % K % E r r o r a t l s m L e v e l 1 G6-2 g r a n i t i c d i k e b i o t i t e 3 7 . 0 0 0.28 2 B6 - 3 QFB gneiss-TG b i o t i t e 3 7.47 0.27 3 B12 QFB g n e i s s - L A b i o t i t e 3 7.61 0.27 4 B6-3A QFB gneiss-TG b i o t i t e 3 7 .54 0.48 5 B2-1 QFB gneiss-TG b i o t i t e 3 7.22 0.28 6 B l 4 q u a r t z d i o r i t e b i o t i t e 3 6.25 0.61 7 B15 q u a r t z d i o r i t e h ornblende 5 0.522 .1 . 3 4 QFB = q u a r t z - f e l d s p a r - b i o t i t e , TC = Trans-Canada Highway sample LA = L a Forme Creek sample mesh s i z e o f 28-48 was used TABLE H-ll» D e s c r i p t i o n o f samples d a t e d by the K-Ar method. Run No. Date o f A r A n a l y s i s * A r 4 0 ( r a d . ) A r 4 0 ( r a d . ) A r 4 0 ( r a d . ) A p p a r e n t Age (M.Y.) T o t a l Ar40 ( l 0 - 5 C c STP/g.) K40 1 l / l l 0 . 8 7 1 . 6 3 0 . 0 0 3 1 2 5 2 . 5 ± 3 . l 2 1/14 0.88 1.64 0 . 0 0 3 2 3 54.4+3.2 3 1/16 0 . 8 9 1.64 0 . 0 0 3 3 2 56.0+3.3 4 1/18 0 . 8 7 1.20 0 . 0 0 3 4 6 58.313.7 5 1/21 0.82 0 . 9 5 0 0 . 0 0 3 2 1 5 4 . l i 3 . 2 6 1/23 0 . 8 5 1 . 2 9 0 . 0 0 3 0 4 51.313.4 7 1/25 0 . 5 8 0 . 3 1 5 0.00891 146 .5+11.8 date i n t h e form o f month/day o f 1974 TABLE H-12t A n a l y t i c a l d a t a f o r K-Ar a n a l y s e s / U n c e r t a i n t i e s quoted are 95 % c o n f i d e n c e l i m i t s (see t e x t ) . 187 Sample i° K Measurements Average % K % E r r o r a t l s m L e v e l B15.HB 0 . 5 0 2 0 . 5 0 9 0 . 5 3 5 0 . 5 2 9 0 . 5 3 6 0 . 5 2 2 1 . 3 4 B l 4 , BT 6 . 3 2 6 . 1 9 6.24 6 . 2 5 0 . 6 1 G6-2,BT 6 . 9 6 7 . 0 2 7 . 0 2 7 . 0 0 0.28 B2-1.BT 7.18 7 . 2 5 7 . 2 3 7 . 2 2 0.28 B3,BT 7 . 2 9 7 . 3 2 7 . 3 3 7 . 3 1 0 . 1 6 B6-2.BT 6 . 8 7 6 . 9 1 7 . 0 9 6.82 7 . 1 6 7 . 1 6 7 . 0 0 1 .26 mesh s i z e 28-48 was used f o r a l l m i n e r a l s e p a r a t e s TABLE H-13» K c o n c e n t r a t i o n r e s u l t s o f m i n e r a l s e p a r a t e s . 188 Sample % K Measurements Average % K % E r r o r a t l s m L e v e l B6-3.BT 7.45 7.51 7.45 7.47 0.27 B6-3A.BT 7.61 7.52 7.49 7.54 0.48 B7-2.BT 5.52 5.41 5.58 5.49 5.50 0.74 B8.BT 7.05 7.12 6.95 7.04 0.70 B12,BT 7.57 7.61 7.64 7.61 0.27 TABLE H - l 3 ( c o n t . ) i K c o n c e n t r a t i o n r e s u l t s o f m i n e r a l s e p a r a t e s . 189 Sample % K Measurements Average $ K Average Rb(ppm) K/Rb R a t i o B1-1,WR 2 . 0 9 2 . 0 9 2 . 0 9 1 1 1 . 0 188. B2-1.WR 1 . 9 5 1 . 9 4 1 . 9 4 5 9 5 . 4 204. B3.WR 1 . 4 9 1.48 1 . 4 8 5 6 1 . 2 243. B4-X.WR 1 . 2 2 1 . 2 5 1 . 2 3 5 6 6 . 0 187. B4-Y.WR 1.18 1.14 1 . 1 6 7 5 . 3 1 5 4 . B6-1.WR 1 . 0 8 1 . 0 9 1 . 0 8 5 4 9 . 7 218. B6-2.WR 1 .66 1 . 6 5 1 . 6 5 5 8 5 . 3 1 9 4 . B6-3.WR 2 . 0 0 . 2 . 0 1 2 . 0 0 5 9 4 . 1 2 1 3 . B6-3A,WR 1 . 1 5 1 . 1 5 1 . 1 5 8 3 . 5 138. B7-1,WR 1 . 5 7 1 . 5 8 1 . 5 7 5 6 1 . 3 2 5 7 . B?-2,WR 1.48 1 . 4 7 1 . 4 7 5 5 7 . 7 2 5 6 . * mesh s i z e o f g r e a t e r t h a n 1 0 0 was used f o r a l l whole r o c k samples TABL5 H-l4> K c o n c e n t r a t i o n r e s u l t s and K/Rb r a t i o s o f whole r o c k samples. 190 Sample % K Measurements Average % K Average Rb(ppm) K/Rb R a t i o B8.WR 2.21 2 . 2 3 2.22 106. 209. B9,WR 1 . 85 . 1 . 85 1 . 85 87.1 212. B10,WR 1.68 1.71 1.695 73.1 232. Bll.WR 1.84 1.84 1.84 89 . 6 205. B12.WR 2.74 2 . 73 2.735 97.0 282. B13.WR. 0.848 0.845 0.8465 29.2 283. Rl-T-l.WR 1 . 94 1 . 95 1.945 101 . 6 191. ' R5-2fWR 1 . 98 2.00 1 . 99 87 . 3 228. R-5-T.WR 2.02 2.03 2 .025 86 . 3 235. G4,WR 1.21 1.22 1 .215 54.1 225. G6-2,WR 4.34 4 .35 4.345 253.5 171. B5-1»WR 2.37 2 . 39 2 . 38 221.1 108. TABLE H-14 (cont.)» K c o n c e n t r a t i o n r e s u l t s and K/Rb r a t i o s o f whole r o c k samples. 191 APPENDIX I STATISTICAL TECHNIQUES FITTING OF STRAIGHT LINES TO DATA Numerous p a p e r s have appeared i n the l i t e r a t u r e r e g a r d i n g t h e f i t t i n g o f a s t r a i g h t l i n e ( i s o c h r o n ) t o Rb-Sr e x p e r i m e n t a l d a t a on a BPI p l o t ( Y o r k , 1 9 6 6 ; M c l n t y r e e t a l . , 1 9 6 6 ; Y o r k , 1 9 6 7 ; W i l l i a m s o n , 1 9 6 8 ; York, 1 9 6 9 ; Brooks e t a l . , 1 9 7 2 ) . There are two b a s i c p h i l o s o p h i e s ( Y o r k , 1 9 6 6 v e r s u s Y o r k , 1 9 6 9 ) as t o how t o c a l c u l a t e e r r o r s i n the s l o p e and i n t e r c e p t (the age and i n i t i a l r a t i o ) o f a f i t t e d s t r a i g h t l i n e . York ( 1 9 6 6 ) c a l c u l a t e s e r r o r s i n t h e s l o p e and i n t e r c e p t based on the f i t o f t h e p o i n t s t o the l i n e , w i t h o u t t a k i n g i n t o a ccount the e x p e r i m e n t a l u n c e r t a i n t i e s o f the i n d i v i d u a l d a t a p o i n t s . York ( 1 9 6 9 ) . however, does t a k e i n t o a c c o u n t e x p e r i m e n t a l e r r o r s . T h i s t e n d s t o almost always make York ( 1 9 6 9 ) e s t i m a t e s o f u n c e r t a i n t i e s l o w e r t h a n t h o s e o f York (1966) . Brooks e t a l . ( 1 9 7 2 ) have s u g g e s t e d t h a t the York ( 1 9 6 9 ) u n c e r t a i n t i e s be used when Rb-Sr d a t a f i t t he l i n e w i t h i n e x p e r i m e n t a l p r e c i s i o n ("an i s o c h r o n " ) v/hereas York ( I 9 6 6 ) u n c e r t a i n t i e s be used when the s c a t t e r o f the Rb-Sr d a t a about the l i n e exceeds e x p e r i m e n t a l e r r o r ("an e r r o r c h r o n " ) . T h i s p r o c e d u r e has been f o l l o w e d f o r t h i s s t u d y . S l o p e s and i n t e r c e p t s were a l l c a l c u l a t e d by the method of York ( 1 9 6 9 ) . E r r o r s i n R b 8 7 / S r 8 6 and S r 8 7 / S r 8 6 r a t i o s were c o n s i d e r e d t o be u n c o r r e l a t e d . 192 ESTIMATES OF PRECISION FOR REPLICATE EXPERIMENTAL DATA I t i s o f t e n advantageous t o p o o l the i n f o r m a t i o n f u r n i s h e d by a group o f s h o r t s e t s o f d a t a o f u n e q u a l s i z e s T h i s s i t u a t i o n was e n c o u n t e r e d d u r i n g t h i s s t u d y where i t was d e s i r e d t o c a l c u l a t e e s t i m a t e s o f p r e c i s i o n f o r an e x p e r i m e n t a l t e c h n i q u e f o r v/hich the d a t a c o n s i s t e d o f u n e q u a l l y s i z e d s e t s o f r e p l i c a t e measurements o f v a r i o u s samples. E s t i m a t e s o f p r e c i s i o n t h a t can be made (Youden, 1951) a r e t e s t i m a t e d s t a n d a r d d e v i a t i o n j = l l v i = l m Z C n j-1) j = l (1 e s t i m a t e d % e r r o r a t t h e one s t a n d a r d d e v i a t i o n l e v e l = 100 x m n 0=1 1=1 J / x - i i - x m £ ( n j - l ) 0=1 (2 where m x m = number o f s e t s o f d a t a = number o f d a t a p o i n t s i n the j " t " s e t = . i t h d a t a p o i n t i n the j"th s e t = mean o f d a t a p o i n t s i n the j ^ h s e t j=l ( n . ; - l ) = t o t a l number o f degrees o f freedom 193 The d e c i s i o n t o use (1) o r (2) i s dependent on t h e c h a r a c t e r o f t h e e r r o r s f o r t h e p r o c e d u r e o r method one i s d e a l i n g w i t h ; i . e . , c o n s t a n t a b s o l u t e e r r o r o r c o n s t a n t p e r c e n t a g e e r r o r . O f t e n a l l t h e s e t s are d u p l i c a t e s . Then e q u a t i o n (1) r e d u c e s t o e s t i m a t e d s t a n d a r d d e v i a t i o n \ m 5~ d 2 j=l (3) 2m where m = number o f s e t s o f d u p l i c a t e measurements = number o f degrees o f freedom d = d i f f e r e n c e between the d u p l i c a t e s and i s t a k e n f o r m p a i r s I t s h o u l d be n o t e d t h a t m p a i r s o f d u p l i c a t e s f u r n i s h as much i n f o r m a t i o n as (m+1) measurements a l l i n one s e t . A good way t o e s t i m a t e the r e p r o d u c i b i l i t y ( i . e . , p r e c i s i o n ) o f S r i s o t o p i c a n a l y s e s i s t o make d u p l i c a t e Sr8?/3r86 measurements o f s e v e r a l samples. E q u a t i o n (3) would be t h e p r o p e r way t o e s t i m a t e the p r e c i s i o n o f such d a t a , p r o v i d e d t h a t i n d i v i d u a l Sr87/Sr86 measurements ( i . e . , i n d i v i d u a l mass s p e c t r o m e t e r r u n s ) were d e t e r m i n e d w i t h about the same p r e c i s i o n . T h i s was n o t the case f o r t h i s s t u d y . I t was d e c i d e d not t o use e q u a t i o n (3) s i n c e t h e p r e c i s i o n o f i n d i v i d u a l runs of d u p l i c a t e s v a r i e d c o n s i d e r -a b l y and n o t many s e t s o f d u p l i c a t e s were r u n . 194 WEIGHTING OF EXPERIMENTAL DATA The o b j e c t i v e i s t o a p p l y t h e ' b e s t ' s t a t i s t i c a l w e i g h t i n g f u n c t i o n t o a g i v e n s e t o f d a t a assuming n o n - e q u a l v a r i a n c e s f o r i n d i v i d u a l p o i n t s . Ahern (1975) d e t e r m i n e d by the method o f L a g r a n g i a n m u l t i p l i e r s t h a t the s t a t i s t i c a l l y • b e s t * w e i g h t i n g f u n c t i o n i s t h a t f u n c t i o n w^ such t h a t i f x = w^x^ + W 2 X 2 + W 3 X 3 + ... + w n x n t h e n WJ_ m i n i m i z e s x's r e s u l t i n g v a r i a n c e . I t t u r n s out t h a t 2 2 2 2 where s i » s 2 » s 3 » " " s n a r e 't'ne v a r i a n c e s c o r r e s p o n d i n g t o t h e s e t o f d a t a x^,X2,X3,..,,x n. I t i s w o r t h w h i l e t o note t h a t the e r r o r s a s s o c i a t e d w i t h a g i v e n d a t a p o i n t need o n l y be p r o p o r t i o n a l t o the v a r i a n c e o r s t a n d a r d d e v i a . t i o n . ANALYSIS OF RB-SR DATA ON A COMPSTON-JEFFREY PLOT The o b j e c t i v e was t o determine the ' b e s t ' common i n t e r s e c t i o n p o i n t o r p o i n t s o f the f a m i l y o f l i n e s i n Graph C. I t was d e c i d e d t o use an e q u a l - a r e a d e n s i t y p l o t o f the i n t e r s e c t i o n p o i n t s o f l i n e s i n Graph C i n o r d e r t o d i s p l a y t h e most l i k e l y common i n t e r s e c t i o n p o i n t s . The pr o c e d u r e used was as f o l l o w s i 195 (1) Any i n t e r s e c t i o n p o i n t between two l i n e s was count e d as one p o i n t . Thus, i f t h r e e l i n e s i n t e r -s e c t e d a t a common p o i n t , t h a t p o i n t was coun t e d t h r e e t i m e s . The t o t a l number o f p o s s i b l e i n t e r -s e c t i o n p o i n t s f o r n l i n e s = n ( n - l ) / 2 . I n t h i s case t h e t o t a l i s 435 p o i n t s f o r 30 l i n e s ( s a m p l e s ) . A good number o f t h e s e l i e o u t s i d e the a r e a o f i n t e r e s t as seen on Graphs C and D. (2) A g r i d s i z e was chosen c o n s i s t e n t w i t h the s a m p l i n g o f d a t a . The number o f p o i n t s w i t h i n each g r i d square was co u n t e d and t h a t t o t a l was a s s o c i a t e d w i t h the c e n t e r o f t h e g r i d s q u a r e . (3) The co u n t e d t o t a l s were t h e n c o n t o u r e d t o produce the r e s u l t s shown i n Graph D. No attempt was made t o e s t i m a t e age u n c e r t a i n t i e s . I t i s r e c o g n i z e d t h a t because o f t h e e x p e r i m e n t a l u n c e r t a i n t i e s i n t h e x and y - i n t e r c e p t s p l o t t e d i n Graph C, each sample s h o u l d a c t u a l l y be r e p r e s e n t e d by an envelope o f l i n e s w i t h i n w h i c h t h e ' t r u e ' l i n e f o r t h a t sample i s c o n t a i n e d . The u n c e r t a i n t i e s i n t h e x - i n t e r c e p t s (y=0) p l o t t e d are g i v e n i n C h a p t e r IV. The u n c e r t a i n t i e s i n the y - i n t e r c e p t s (x=0.699) p l o t t e d may be c a l c u l a t e d as f o l l o w s i D e f i n e y - i n t e r c e p t (x=0) = B ± b x - i n t e r c e p t (y=0) = A t a 196 E q u a t i o n o f a l l p o s s i b l e l i n e s i s y ^ - ] x + B l { { b ( A - x ) + -Sj*} (6) Thus the a s s o c i a t e d e r r o r o f the y - i n t e r c e p t when x=0.699 (Graph G) i s c + l { b ( A - o . 6 9 9 ) + ' ^ 2 p B ) (7) T h i s e r r o r can be c a l c u l a t e d f o r each sample from the d a t a i n C h a p t e r IV. 

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