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Diagenesis and thermal maturation of the Eureka sound formation, Strand Fiord, Axel Heiberg Island, Arctic… Allen, David Peter Beddome 1986

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DIAGENESIS A N D T H E R M A L M A T U R A T I O N O F T H E E U R E K A S O U N D F O R M A T I O N , S T R A N D F IORD, AXEL HE IBERC I S L A N D , A R C T I C C A N A D A by D A V I D PETER B E D D O M E A L L E N A THESIS S U B M I T T E D IN PARTIAL F U L F I L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E C R E E O F M A S T E R O F S C I E N C E in T H E F A C U L T Y O F G R A D U A T E STUDIES (Depar tment of G e o l o g i c a l Sc iences ) W e a c c e p t this thes is as. c o n f o r m i n g to the r e q u i r e d standard T H E UNIVERSITY O F BRITISH C O L U M B I A Spr ing , 1986 © Dav id Peter B e d d o m e A l l e n , 1986 In p resen t ing this thesis in partial fu l f i lment of the requ i rements for an a d v a n c e d d e g r e e at the T H E UNIVERSITY O F BRITISH C O L U M B I A , I ag ree that the Library shall make it f reely avai lable for re fe rence a n d study. I further agree that pe rmiss ion for ex tens ive c o p y i n g of this thesis for scholar ly p u r p o s e s may b e granted by the H e a d of m y D e p a r t m e n t o r by his o r her representat ives . It is u n d e r s t o o d that c o p y i n g or p u b l i c a t i o n of this thesis for f inancia l gain shall n o t b e a l l o w e d w i t h o u t my wr i t ten p e r m i s s i o n ! ( D e p a r t m e n t of G e o l o g i c a l Sc iences ) T H E UNIVERSITY O F BRITISH C O L U M B I A 2075 W e s b r o o k Place V a n c o u v e r , C a n a d a V6T 1 W 5 Date : Spr ing , 1986 A B S T R A C T Near ly 3000 c o n t i n u o u s metres of Eureka S o u n d Fo rmat ion sandstones , shales and coa ls w e r e e x a m i n e d in o u t c r o p a l o n g Kanguk Peninsu la , A x e l H e i b e r g Island, N.W.T. , in the p resent study. F rom these rocks , d iagenet ic parameters s u c h as illite crystrall inity, 1.0 n m peak sharpness ratios, p r o p o r t i o n of illite in i l l i te /smect i te m i x e d layers, a n d s a n d s t o n e c e m e n t paragenesis have b e e n u s e d in c o m b i n a t i o n w i t h thermal m o d e l l i n g to make in fe rences about the t h e r m o c h e m i c a l e v o l u t i o n of the strata a n d the i r c o n t a i n e d p o r e waters . The f ind ings f r o m b o t h the thermal m o d e l l i n g and s a n d s t o n e p e t r o l o g y suggest that a s y n - o r p o s t - t e c t o n i c heat f l o w anomaly e x i s t e d w h e r e b y h e a t e d N a + - e n r i c h e d waters passed f r o m diapi r c o r e s (where hal ite d i s s o l u t i o n o c c u r r e d ) in to laterally ad jacent p e r m e a b l e l i tho log ies such as coa ls and arenites. This c o n c e p t is s u p p o r t e d by an offset in t h e p l o t o f vitr inite re f lectance versus d e p t h w h e r e b y the u p p e r s e g m e n t (based primari ly o n coals) has h igher re f lectance values than the l o w e r s e g m e n t (based main ly o n phytoc lasts ) , and o n the f o r m a t i o n of the s o d i u m rich phase d a w s o n i t e as the last auth igen ic phase p rec ip i ta ted in the po res o f the s a n d s t o n e s . A n e x a m i n a t i o n of the c h e m i c a l c o n d i t i o n s under w h i c h halite d isso lves a n d d a w s o n i t e prec ip i tates sugges ts that the N a * c o n c e n t r a t i o n may have b e e n as h igh as 105 g I " 1 . C l a y minera l analyses suggest that the major part of t h e clay var iat ion in the Eureka S o u n d Fo rmat ion can be at t r ibuted to changes in detr ital minerals rather than to d i a g e n e t i c react ions b e t w e e n the clay minerals and their c h e m i c a l env i ronment . Textura l re lat ionships b e t w e e n the six pr inc ipa l au th igen ic s a n d s t o n e c e m e n t s (calcite, anker i te , s ider i te, d a w s o n i t e , kaol in i te and quartz o v e r g r o w t h s ) and d i sso lu t i on features in the a luminos i l icates suggest that at least 7 e p i s o d e s of c h a n g i n g p o r e f lu id chemis t r y have o c c u r e d s ince the strata w e r e d e p o s i t e d . ii Table of C o n t e n t s I. G E N E R A L I N T R O D U C T I O N 1 A. G E N E R A L ' S T A T E M E N T . 1 B. S T U D Y A R E A , , . .2 C . G E O L O G I C SETTING 2 D. P R E V I O U S W O R K 7 II. O R G A N I C M A T U R A T I O N , 11 A . EXPERIMENTAL 12 1. S a m p l e Preparat ion . . . .12 a. C o a l Pellets 12 b. Phytoc last Pel lets : 13 2. Ana lyt ica l T e c h n i q u e s 13 a. E lementa l Analys is 14 b. T i m e - T e m p e r a t u r e M o d e l 14 B. RESULTS A N D D I S C U S S I O N 16 1. C o a l i f i c a t i o n Grad ients 16 a. Statistical C o n s i d e r a t i o n s 19 b. C o n s i d e r a t i o n of RQmax D i s t r i bu t ion w i t h D e p t h 20 c. C o n s i d e r a t i o n of Shifts in C o a l i f i c a t i o n Grad ient 22 2. P a l e o - d e p t h of Burial . 25 a. M a x i m u m Pressure C o n s i d e r a t i o n s 27 3. P a l e o - g e o t h e r m a l Grad ient 29 III. S A N D S T O N E P E T R O L O G Y A N D DIAGENESIS 35 A. RESULTS : . . . . . . . . . . . .35 1. P e t r o l o g y 35 2. D i s c r i p t i o n of A u t h i g e n i c M ine ra l s 41 a. Pr incipal A u t h i g e n i c M inera ls 41 b. A c c e s s o r y A u t h i g e n i c M inera ls 50 iii B. D I S C U S S I O N 55 1. Textural Re lat ionsh ips 55 2. Fluid C h e m i s t r y 67 a. D a w s o n i t e : C h e m i c a l Cons t ra in ts 71 IV. S H A L E M I N E R A L O C Y A N D D I A C E N E S I S 85 A . EXPERIMENTAL 85 1. C lay Samp le Preparat ion 85 a. O r i e n t e d Samp les 87 b. U n o r i e n t e d Samples 88 2. Instrumental T e c h n i q u e s 88 3. Analyt ica l T e c h n i q u e s 89 a. C lay M i n e r a l o g y 89 b. Semi -quant i ta t ive M i n e r a l o g y 90 c. M i x e d - l a y e r Ana lyses 92 d . Sharpness Ratios and Illite Crystal l in i ty Index 96 B. RESULTS 96 1. C lay M i n e r a l o g y 96 • 2. Semi -quant i ta t ive M i n e r a l o g y , 97 3. Percent Illite in I l l i te /Smectite M i x e d - l a y e r s 98 4. Illite Crystal l in i ty Index ~ 103 5. Sharpness Ratio 104 C . D I S C U S S I O N 104 1. D i a g e n e t i c Facies and Sub - fac ies 109 2. C o n s i d e r a t i o n of Shifts in C lay Parameters w i th D e p t h '. 113 3. C o n s i d e r a t i o n of Var iat ions in Samp le M i n e r a l o g y w i th D e p t h 115 V. S U M M A R Y A N D C O N C L U S I O N S 118 A . Genera l Summary 118 iv B. D i s c u s s i o n , 120 1. Subarial W e a t h e r i n g 120 2. S u b a q u e o u s A g g r a d a t i o n and N e o f o r m a t i o n 120 3. S e d i m e n t A V a t e r Interface React ions (D iagenes is A) 121 4. S h a l l o w Burial (D iagenes is B) 121 5. D e e p Burial (D iagenes is C ) . 123 6. Syn /Post O o g e n i c React ions (D iagenes is D) .125 VI. Re fe rences . . . . . . .128 VII. A p p e n d i c e s • ...141 A . A p p e n d i x 1: Po tass ium Saturated Clays . . . . .142 B. A p p e n d i x 2: M a g n e s i u m Saturated C lays 143 C . A p p e n d i x 3: N o n - S a t u r a t e d C lays .144 D. A p p e n d i x 4: Heat T reated C lays 145 v List of Tab les C H N E lementa l Analysis F ramework Pe t ro logy of Sands tones D i s t r i bu t ion of Sands tone C e m e n t s T h r o u g h the Strat igraphic S e c t i o n Heat C a p a c i t y C o e f f i c i e n t s and Standard State Enthalpy a n d Ent ropy of D a w s o n i t e N a m e s , C h e m i c a l Formulae and Free Energies of Fo rmat ion of the S o d i u m C a r b o n a t e s u s e d in the Inc luded Act iv i ty /Act iv i ty and Partial Pressure D iagrams React ions , Free Energies o f React ion a n d L o g K e g Va lues of React ions U s e d in the Sys tem: H + - A l + 3 - N a + - H z O React ions , Free Energies of React ion and L o g K e q V a l u e s of React ions U s e d in the System: H + - A l + 3 - H 2 0 - C 0 2 M i n e r a l A s s e m b l a g e s C o n s i d e r e d in the D is t r i bu t ion of S p e c i e s Ana lyses C o m p a r i s o n of Eureka S o u n d Fo rmat ion Fluid C h e m i s t r y w i t h the Fluid C h e m i s t r y of O t h e r Natural Systems Pos i t i ons of (002)10/ (003)17 Di f f ract ion Peaks for V a r i o u s % lll ite in I l l i te /Smect i te Va lues ( m o d i f i e d f r o m R e y n o l d s a n d H o w e r , 1970) Var iat ions in Smect i te (060) d - s p a c i n g T h r o u g h S e c t i o n Semi -quant i ta t i ve C lay M i n e r a l o g y of S t u d i e d S e c t i o n w i t h Und i f fe ren t ia ted ll l ite Semi -quant i ta t ive C lay M i n e r a l o g y of S t u d i e d S e c t i o n w i t h D i f fe rent ia ted l l l ite Var iat ions in ll l ite Crystal l in i ty w i t h D e p t h Var iat ions in Sharpness Ratios w i t h D e p t h vi List of Figures Figure 1- L o c a t i o n m a p s h o w i n g study area o n Kanguk Peninsu la , 3 A x e l H e i b e r g Island, N.W.T. . Figure 2- S impl i f ied g e o l o g i c m a p o f Kanguk Pen insu la s h o w i n g 4 t h e g e n e r a l i z e d structure in the study area. Figure 3 - G e n e r a l i z e d strat igraphic s e c t i o n s h o w i n g l i thofacies 6 interpretat ion (Ricketts ef. al, pers. comm.) and s e c t i o n subd iv i s ions (zones) . Figure 4 - A r i t h m e t i c p lo t of m e a n m a x i m u m re f lectance versus 17 d e p t h s h o w i n g regress ion l ines a n d c o r r e s p o n d i n g r -squared values t h r o u g h the 3 p o s s i b l e p o p u l a t i o n s . Figure 5- S e m i l o g p lot of m e a n m a x i m u m re f lectance versus d e p t h 18 s h o w i n g regress ion l ines and c o r r e s p o n d i n g r -squared va lues t h r o u g h the 3 p o s s i b l e p o p u l a t i o n s . Figure 6- Hydros ta t ic pressure d i s t r ibu t ion t h r o u g h s t u d i e d s e c t i o n 28 a s s u m i n g a m a x i m u m d e p t h of burial of 5500 metres . Figure 7- Representa t ion of the t e c t o n i c e v o l u t i o n of Eureka 30 S o u n d strata at Strand F iord a s s u m i n g a m a x i m u m d e p t h of burial of 6800 metres . Figure. 8- Representa t ion of the t e c t o n i c e v o l u t i o n of Eureka 31 S o u n d strata at Strand Fiord a s s u m i n g a m a x i m u m d e p t h of burial of 5500 metres . Figure 9- G e o t h e r m a l grad ient d e t e r m i n a t i o n us ing Lopat in 's (1971) 32 m e t h o d and assuming a m a x i m u m d e p t h of burial of 6800 metres. Figure 10- G e o t h e r m a l gradient de te rm ina t i on us ing Lopat in 's (1971) 33 m e t h o d and assuming a m a x i m u m d e p t h of burial of 5500 metres. Figure 11 - R A K - 2 5 rock clan p l o t t e d o n a m o d i f i e d G i lber t ' s (1954) 37 c o m p o s i t i o n tr iangle. Figure 12a - Energy d ispers ive s p e c t r o g r a p h of M g poor / f ree anker i te . 43 Figure 12b - Energy d ispers ive s p e c t r o g r a p h of M g p o o r anker i te . 43 Figure 13 - A p p r o x i m a t e ankerite c o m p o s i t i o n range p l o t t e d o n a 44 C a O - F e O - M g O - C 0 2 ternary d iagram. Figure 14a - Energy d ispers ive s p e c t r o g r a p h of s ider i te . 46 Figure 14b - Energy d ispers ive s p e c t r o g r a p h of d a w s o n i t e s h o w i n g 46 e q u a l p r o p o r t i o n s of N a and A l . vi i Figure 15 - Var iat ion in d a w s o n i t e a n d anker i te p r o p o r t i o n s w i t h 4 7 d e p t h . Figure 16 - D iagram of paragenet ic s e q u e n c e . 68 Figure 17 - D a w s o n i t e heat capac i ty f u n c t i o n fit to the data of 72 Ferrante et al. (1976). Figure 18- Plot of L o g [ A N A + /A|_] +] versus L o g [ A ^ | + 3/A+3H*] 74 Figure 19 - Plot of L o g [ A A | • a / A * 3 H + ] versus L o g P C Q z . 75 Figure 20 - Plot of L o g P c o 2 v e r s u s L o g A | - | 2 0 7 6 Figure 2 1 - Plot of variat ions in (002)10/ (003)17 illite peak l o c a t i o n 94 w i t h var iat ions in %i l l i te in i l l i te /smect i te m i x e d - l a y e r clays. Figure 22 - Plot of var iat ions in shale c o m p o s i t i o n w i t h d e p t h and 99 t h r o u g h ind iv idual p a l e o - e n v i r o n m e n t s w i th i l l ite's d is t r ibut ion b e i n g n o n d i f ferent iated . Figure 23 - Plot of var iat ions in shale c o m p o s i t i o n w i t h d e p t h and 100 t h r o u g h ind iv idual p a l e o - e n v i r o n m e n t s w i th i l l ite's d is t r ibut ion b e i n g d i f ferent iated . Figure 24- Plot of var iat ions in the p e r c e n t a g e of illite in 101 i l l i te /smect i te m i x e d - l a y e r e d clays w i t h d e p t h a n d t h r o u g h the indiv idual p a l e o e n v i r o n m e n t s of R A K - 2 5 . Figure 25 - Plot of variat ions in illite crystal l inity t h r o u g h s e c t i o n and 105 ind iv idual p a l e o - e n v i r o n m e n t s . Figure 26 - Plot of variat ions in the 1.0:1.05 n m peak sharpness 106 ratio t h r o u g h s e c t i o n and ind iv idual p a l e o - e n v i r o n m e n t s . Figure 27 - Plot of d iagenet ic f a d e s in P-T space . 111 Figure 28 - Summary d iagram of early stage s u b a q u e o u s agg reda t i on 122 and n e o f o r m a t i o n of clay minerals u n d e r h u m i d / t r o p i c a l s o u r c e c o n d i t i o n s . Figure 29 - Summary d iagram of d e e p burial d i agenet ic env i ronment . 124 Figure 30 - Summary d iagram of p o s t / s y n - t e c t o n i c d iagenet ic 126 env i ronment . vii i List o f Plates M o r p h o l o g y , Textural Re lat ionsh ips , and Back Scat te red E lect ron Image A p p e a r a n c e of D a w s o n i t e and A s s o c i a t e d M ine ra l s M o r p h o l o g y and O c c u r e n c e of Kaol in i te M o r p h o l o g y and O c c u r e n c e of Pyrite a n d Ruti le M o r p h o l o g y and Textura l Re lat ionsh ips B e t w e e n D a w s o n i t e and Q u a r t z O v e r g r o w t h s Textura l Re lat ionsh ips B e t w e e n Anker i te and Q u a r t z O v e r g r o w t h s Textura l Re lat ionsh ips B e t w e e n Ca lc i te , Anker i te , a n d Q u a r t z O v e r g r o w t h s Textural Re lat ionsh ips B e t w e e n D a w s o n i t e a n d o t h e r C a r b o n a t e s Textural Re lat ionsh ips B e t w e e n D a w s o n i t e and O t h e r Si l icates A c k n o w l e d g e m e n t s S incere thanks are e x t e n d e d to Dr. R. M a r c Bust in fo r o v e r s e e i n g this thesis, and for e n d u r i n g the many headaches and frustrat ions that w e r e e n c o u n t e r e d a long the w a y to c o m p l e t i n g the project . A d d i t i o n a l thanks are e x t e n d e d to Dr. W i l l i a m Barnes for o v e r s e e i n g the pro ject du r ing Dr. Bust in 's sabbat ica l leave. Financial s u p p o r t for the pro ject was o b t a i n e d f r o m a Natural S c i e n c e s and Eng ineer ing Research C o u n c i l of C a n a d a opera t ing grant to Dr. Bust in . Log is t ic s u p p o r t a n d add i t iona l f u n d i n g w e r e p r o v i d e d by the G e o l o g i c a l Survey o f C a n a d a (I.S.P.G.) under the g u i d a n c e of D r . D o n a l d K. Norr is . I am espec ia l l y grateful t o Dr. Nor r is , w h o was inst rumenta l in k ind l i ng my early interests in g e o l o g y a n d p r o v i d i n g m e w i t h the o p p o r t u n i t y to pursue my thesis t h r o u g h the G . S . C . Dr. Brian Ricketts , a lso of the G .S .C . , is t h a n k e d b o t h for his i n v o l v e m e n t in the f ie ld s tudy and fo r s u g g e s t i n g the or ig ina l thesis t o p i c . I am grateful fo r cr i t ical rev iews of t h e thes is by Drs. R .M . Bust in , W . C . Barnes, R. B e r m a n and B. Broster . M y w i fe , W i z , s o n , Ryan, and daughter , A ins ley p r o v i d e d a surp lus of m u c h n e e d e d mora l s u p p o r t and h e l p e d m e retain m y sanity dur ing t h o s e t imes w h e n it s e e m e d that this thesis w o u l d g o o n forever . A final n o t e of e x t r e m e apprec ia t ion is e x t e n d e d t o Rober t Fo rman for his pa t ience in " e x p e d i t i n g " the assembly and d is t r ibu t ion of this thesis to m y c o m m i t t e e m e m b e r s dur ing my a b s e n c e in Calgary. I am also grateful for the reprograph ics s u p p o r t that was p r o v i d e d by Esso Resources C a n a d a L im i ted . N o t e o n N o m e n c l a t u r e Dur ing the final stage of preparat ion of this thesis the fo rmal status of the Eureka S o u n d Fo rmat ion was c h a n g e d t o the Eureka S o u n d Group (Mia l l , in press). . Format ions w i th in the r e n a m e d Eureka S o u n d G r o u p rough ly c o r r e s p o n d to the in formal z o n e s u s e d in this thesis. D u e to the t im ing of the c h a n g e in the Eureka S o u n d n o m e n c l a t u r e it was no t p o s s i b l e t o re -o rgan ize this thesis t o i n c o r p o r a t e the n e w g r o u p status and , there fore , the author has reta ined the f o r m a t i o n status for the Eureka S o u n d strata t h r o u g h o u t . xi 1 GENERAL I N T R O D U C T I O N GENERAL STATEMENT Diagene t i c and thermal maturat ion stud ies are impor tan t aspects of s e d i m e n t o l o g y in that they p r o v i d e in fo rmat ion about the thermal and c h e m i c a l e v o l u t i o n of strata. A n u m b e r of character ist ics of the Late Cre taceous -Ear l y Tertiary Eureka S o u n d Fo rmat ion a l o n g Strand Fiord o n weste rn A x e l H e i b e r g Island make strata f r o m this l o c a t i o n of part icular interest fo r d iagenet ic analyses. First, the nearly 3000 m of c o n t i n u o u s s e c t i o n p r o v i d e s an exce l len t data base w i t h an o p p o r t u n i t y t o e x a m i n e c h a n g e s in d iagenet ic and thermal maturat ion parameters across a n u m b e r of d i f ferent p a l e o - e n v i r o n m e n t s . S e c o n d , the a b u n d a n c e of coa l t h r o u g h o u t the Eureka S o u n d Fo rmat ion a l o n g Strand F iord a l lows for c o m p a r i s o n s to b e m a d e b e t w e e n ino rgan ic d iagenet ic parameters and thermal matura t ion in fo rmat ion . Finally, l o c a l i z e d heat f l o w c o m p l e x i t i e s in the Strand Fiord area p r o v i d e an o p p o r t u n i t y to e x a m i n e the ef fects of h igh heat f l o w o n d iagenes is a n d thermal maturat ion . . The present s tudy l o o k s at var iat ions in coa l , s a n d s t o n e and clay d iagenet ic parameters w i th d e p t h and relates these variations to c h e m i c a l and thermal changes that o c c u r r e d dur ing the e v o l u t i o n of the Eureka S o u n d F o r m a t i o n at Strand Fiord. The pr imary parameters c o n s i d e r e d i nc lude illite crystall inity, sharpness ratio of illite peaks , p e r c e n t a g e of illite in i l l i te -smect i te m i x e d layer clays a n d vitr inite re f lectance . The pr imary ob ject i ves of this s tudy are to : 1) d e t e r m i n e var iat ions in b o t h shale and sands tone m i n e r a l o g y and d iagenes is t h r o u g h o u t the s tud ied s e c t i o n ; 2) d e t e r m i n e the paragenesis of auth igen ic minerals ; 3) est imate the g e o t h e r m a l grad ient and m a x i m u m d e p t h o f bur ial of strata in the s tudy area; 4) e x a m i n e the ef fect that c h a n g e s in p a l e o - e n v i r o n m e n t has o n d iagenes is and thermal matura t ion ; and 5) m o d e l the d iagenet ic p o r e f luids and c h e m i c a l env i ronments . S T U D Y A R E A Samp les f r o m the present s tudy w e r e c o l l e c t e d f r o m approx imate ly 3000 m of c o n t i n u o u s s e c t i o n of the Eureka S o u n d Fo rmat ion that c r o p s ou t a l o n g the s o u t h shore of Kanguk Pen insu la o n w e s t e r n A x e l H e i b e r g Island (Figure 1) The s t u d i e d s e c t i o n was m e a s u r e d a long the sou th l imb of a syncl ine e x p o s e d a long t h e t o p of a r idge e x t e n d i n g f rom 79°30'N lat i tude, 91°30'W l o n g i t u d e , t o 79°14'N lat i tude, 91°03' l ong i tude . Relief in the area never e x c e e d e d 600 m. Figure 2 is a g e n e r a l i z e d g e o l o g i c m a p of Kanguk Pen insu la s h o w i n g the l o c a t i o n of the s t u d i e d s e c t i o n and assoc i a ted g e o l o g y . G e o l p g i c a l Survey of C a n a d a m a p sheet 1301 A— Strand F iord , Distr ict of Franklin (Thors te inson , 1971) s h o u l d b e c o n s u l t e d f o r a smal ler scale m a p of t h e study area. G E O L O G I C S E T T I N G T h e Eureka S o u n d Format ion is a Late C r e t a c e o u s t o Late E o c e n e , p r e d o m i n a n t l y n o n - m a r i n e and nearshore mar ine clast ic s e q u e n c e that c o m p r i s e s the y o u n g e s t strata o f the Sverdrup Basin of the C a n a d i a n A rc t ic A r c h i p e l a g o . The Sverdrup Basin is a pe r ic ra ton ic structural d e p r e s s i o n o c c u r r i n g adjacent t o the nor thern margin of the N o r t h A m e r i c a n c ra ton (Balkwil l , 1978; M i a l l , 1984, in press). At its d e p o c e n t e r , the basin s u c c e s s i o n is u p to 13000 m thick. Regional ly , the Sverdrup Basin e x t e n d s for approx imate ly 1300 k m a long the nor th centra l part of Figure 1- Locat ion m a p s h o w i n g study area o n Kanguk Peninsula , A x e l H e i b e r g Island, N.W.T.. 4 I —I _ u -CO U. « C o E c o Z CS c E o — o to u . E w k_ o £ u. a o o co CO a m z to III X O 4-inoB3Bt*J3-| ~ E c *~ to o to c t/> to o a E o u . ID Q Foi pu up ^ •a 3 o to o o cn 9 c L L CO <1) 3 . ** O CO O l CO c 3 3 CS a o 111 1 ~ 1 CD ° 1 -f- 3 I 0 X 0 U S> 0 — - | - « Figure 2- Simpl i f ied g e o l o g i c map of Kanguk Pen insu la s h o w i n g the genera l l i zed structure in the s tudy area (mod i f i ed f rom T h o r s t e i n s o n , 1971). the A r c h i p e l a g o . Sed iments of t h e Sverdrup Basin range in age f r o m Late P a l e o z o i c (Visean) t o Early Tertiary and represent d e p o s i t s d e r i v e d in part f r o m Franklinian G e o s y n c l i n e strata up l i f ted by the El lesmerian O r o g e n y (Devon ian—Miss i ss ipp ian ) and craton ic s e d i m e n t s der i ved f r o m terrains t o the s o u t h and east of the Basin (Balkwil l and Bust in , 1980; Ricketts a n d M c l n t y r e , 7985, written pers. comm.) The Sverdrup ' Basin's s o u t h e r n and eastern margins c o r r e s p o n d rough ly t o El lesmer ian structural belts (Balkwi l l , 1978). The nor thern marg ins are r e p o r t e d by M e n e l e y ef al. (1975) to have b e e n d e f i n e d by an intermit tent ly pos i t i ve t e c t o n i c r idge. T h e s t u d i e d s e c t i o n has b e e n d i v i ded in to a n u m b e r of d i f ferent p a l e o - e n v i r o n m e n t s by Ricketts a n d M c l n t y r e (7985, written pers. comm.) w h i c h f o r m the f r a m e w o r k fo r the f o l l o w i n g d i s c u s s i o n . F igure 3 out l ines the genera l stratigraphy and c o r r e s p o n d i n g p a l e o - e n v i r o n m e n t a l in terpretat ions of the s t u d i e d s e c t i o n . The base of the s e c t i o n is m a r k e d by approx imate l y 235 m of mar ine shale of the Kanguk Fo rmat ion . The c o n t a c t b e t w e e n the Kanguk shales a n d the over ly ing Eureka S o u n d Fo rmat ion has b e e n s e l e c t e d at the base of the first major s a n d s t o n e unit. A p p r o x i m a t e l y 500 m of c o a r s e n i n g upwards sandstone -sha le s e q u e n c e s character ize the basal l i thofacies of the Eureka S o u n d Format ion . Each c o a r s e n i n g upwards unit w i th in the first 500 m of s e c t i o n is in terpreted as an ind iv idual p rog rad ing l o b e of a wave d o m i n a t e d de l ta strand plain . A thin i ron sta ined unit marks a major d i s c o n f o r m i t y b e t w e e n t h e t o p o f t h e wave d o m i n a t e d de l ta facies and the over l y ing 265 m of marine shale. A p p r o x i m a t e l y 1020 m of transitonal and fluvial d o m i n a t e d de l ta facies over l ie the mar ine shale. These de l ta ic and transit ional facies c o m p r i s e sandstone -sha le c o a r s e n i n g u p w a r d s e q u e n c e s w h i c h represent interdistr ibutary bay s u b d e l t a - l o b e s . The ent i re 1020 m represents a transit ional facies b e t w e e n the under ly ing w a v e d o m i n a t e d de l ta and over ly ing fluvial d o m i n a t e d de l ta AGE HEIGHT ABOVE BASE (Metres) G ENERAL STRATIGRAPHY ROCK STRATIGRAPHIC UNITS 1 IN TER VAL THICKNESS (Metres) PALEO-ENVIRONMENT 1 LITHOLOGIC DISCRIPTION > < I-CC 111 DC LD o 2780 2020 CO 3 o UJ o < r -UJ a. o rr ui a. a. 3 1000 235 770 Interbedded fine to medium grained quartz arenites, coal (vitrain) and dark grey, friable shale; sandstones are commonly crossbedded and contain abundant chert and organics; shales are commonly coaly; sandstone cements include dawsonite, magnesium-poor ankerite, siderite, calcite, and kaolinite; dawsonite proportion generally increases toward top of section; segment consists of approximately 30 fining- upwards sequences commonly capped with coals; fining upward packages range from 2 to 15 metres in thickness; coal seams are S3 metres in thickness. 1020 Fine to medium grained quartz arenites interbedded with dark grey, friable shale; sandstones are well indurated and poorly to moderately sorted; shales consist primarily of kaolinite, illite and some chlorite; major sandstone cements are magnesium-poor ankerite, calcite and kaolinite; calcite proportion decreases toward top of section; minor coal seams of predominantly vitrain are present; section consists of approximately 45 coarsening upward packages ranging from 5 to 25 metres in thickness. 265 Moderately friable carbonaceous shale; blue-grey on weathered surface; minor sandstone horizons occur through out zone. 500 Interbedded very fine to medium grained, poorly sorted quartz wackes, dark grey siltstones and carbonaceous shales; sandstones are moderately to well indurated; shales consist primarily of kaolinite and illite. 235 Interbedded dark- grey shale shale is moderately friable. and siltstone; 1 R i c k e t t s a n d M c l n t y r e ( p e r s . c o m m . , 1 9 8 5 ) Figure 3- Generalized stratigraphic section showing lithofacies interpretation (Ricketts et al, pers. comm.) and section subdivisions (zones). systems. The final 770 m of the s e c t i o n are c o m p o s e d of a repet i t i on of f in ing u p w a r d s e q u e n c e s c o m m o n l y c a p p e d w i t h coa ls and vert ical a c c r e t i o n depos i t s . These l i tho log ies represent de l ta plain d e p o s i t s of a fluvial d o m i n a t e d de l ta . The Beaufort Fo rmat ion e l sewhere u n c o n f o r m a b l y over l ies the Eureka S o u n d Fo rmat ion a l though it is no t present in the study area. Local ly , in the area of Kanguk Peninsula , b r o a d nor thweste r l y t rend ing d o u b l y p l u n g i n g ant ic l ines and syncl ines d o m i n a t e the structure (Trettin, 1972; Tho rs te inson , 1971 ). C a r b o n i f e r o u s evapor i te diapirs o c c u r over m u c h of the area and are, for the m o s t part, l oca l i zed a l o n g the axes of ant icl ines ( C o u l d and D e M i l l e , 1964; T h o r s t e i n s o n , 1971 ; Balkwil l , 1978; Ricketts and M c l n t y r e , 7985, written pers. comm.). Gravity s tud ies by S o b c z a k et. al. (1963) or iginal ly s u g g e s t e d that the diapirs of the Sverdrup Basin may be c o r e d w i t h halite and , infact, later s tud ies by Davies (1973) c o n f i r m e d the p r e s e n c e of hal ite in the subsur face . Prev ious f ie ld invest igat ions , h o w e v e r , have b e e n unable t o f ind d i rect o r indi rect e v i d e n c e in o u t c r o p t o s u p p o r t the p r e s e n c e of hal ite c o r e s in the diapirs. P R E V I O U S W O R K The strat igraphy of the Eureka S o u n d Format ion t h r o u g h o u t the C a n a d i a n Arct ic Islands is d e s c r i b e d by Fortier. et al. (1963), Fr icker (1963), T o z e r and T h o r s t e i n s o n (1964), Stott (1969), Balkwi l l and Bustin (1975), Balkwi l l et al. (.1975), Bust in (1977), Balkwi l l et al. (1982), Re id iger (1985), and Ricketts and M c l n t y r e (1985, written pers. comm.). In prev ious studies the base of the Eureka S o u n d Format ion at Strand Fiord has b e e n c o n s i d e r e d Maast r icht ian (Bust in , 1977). Recent pa l yno log ica l analyses by Ricketts a n d M c l n t y r e (1985, written pers. comm.), however , have d e t e r m i n e d that the Eureka S o u n d sed iments at Strand F iord w e r e d e p o s i t e d as early as t h e M i d d l e a n d . poss ib l y Early C a m p a n i a n . Further east, at F o s h e i m Pen insu la , the base of the Eureka S o u n d Fo rmat ion may be as o l d as Late Santon ian -Ear ly C a m p a n i a n age, b a s e d o n the p r e s e n c e of the index fossi l Shenoceramus ci. patoontensiformis. C o a l i f i c a t i o n levels of the Eureka S o u n d Format ion have b e e n d e t e r m i n e d f r o m a n u m b e r o f local i t ies in the Arc t ic Islands by Bust in (1977; in press) and R ied iger (1985). A cursory e x a m i n a t i o n of variat ions in coa l i f i ca t ion levels w i t h d e p t h w a s d o n e by Bust in (in press) t h r o u g h a 2500 m th ick s e c t i o n at Strand F iord . Bust in 's (in press) results ind icate that n o systemat ic increase in R 0 m a x exists w i th d e p t h o v e r the interval e x a m i n e d . Bust in at t r ibuted this p h e n o m e n o n to the a b u n d a n c e of evapor i te diapirs in the area w h o s e h igh thermal conduct i v i t i es in ter fered w i t h the norma l thermal maturat ion of the coa l . Reg iona l coa l i f icat ion m a p p i n g o f t h e Canad ian A r c t i c A r c h i p e l a g o by Bustin (in press) revea led that v itr in ite re f l ec tance values vary f r o m a l o w of 0 .17% at M a k i n s o n Inlet t o a h igh of 0 . 7 0 % at Strand F iord . D i a g e n e t i c analyses of s a n d s t o n e s and shales have r e c e i v e d a great dea l of a t ten t ion o v e r the past f e w years. It has b e e n d e m o n s t r a t e d in n u m e r o u s stud ies of t h e . t e x t u r a l re lat ionsh ips b e t w e e n auth igen ic phases that it is p o s s i b l e t o infer f rom rocks i n f o r m a t i o n about c h a n g e s in p o r e w a t e r chemis t ry and phys ica l c o n d i t i o n s t h r o u g h t ime . M e r i n o (1975), Bo les and Franks (1979) and H u t c h e o n ef al. (1980), fo r e x a m p l e , u s e d textural re lat ionships to pred ic t d iagenet ic react ions s u c h as the kao l in i t i za t ion of ch lor i te , c o n v e r s i o n of d o l o m i t e and kaol in i te t o ch lo r i te and ca lc i te , c o n v e r s i o n of b iot i te t o ch lo r i te and the react ion of anor th i te w i t h s o d i u m t o p r o d u c e d i a g e n e t i c s o d i c p lag ioc lase . . Bo les (1978) a lso p r e d i c t e d the f lu id chemis t ry necessary to facil itate the anker i t i zat ion of calci te . Recent w o r k by Surdam (1984), M o n c u r e ef al. (1984), Seibert ef al. (1984), and C r o s s e y ef al. (1.984) have a d d r e s s e d the m e c h a n i c s of c reat ing s e c o n d a r y po ros i t y t h r o u g h the d i sso lu t i on of aluminosil icar.es. W e s c o t t (1983) u s e d d iagenet ic analyses t o , assess the reservoir qual i ty of the C o t t o n Val ley Fo rmat ion of east Texas. O t h e r recent papers o n s a n d s t o n e d iagenes is i nc lude t h o s e of W i l s o n and Pittman (1977), Hurst a n d Irwin (1982) arid H u t c h e o n (1983). T h e r m o d y n a m i c stud ies of au th igen ic assemblages a n d p o r e f lu id chemis t ry have prev ious ly b e e n d o n e o n strata f r o m other locat ions . M e r i n o (1975b) u s e d a d is t r ibut ion of s p e c i e s analysis to assess auth igen ic phase stabi l i t ies w i th respect to f lu id chemist ry f r o m Tertiary sands tones of Cal i forn ia . H u t c h e o n (1981) u s e d t h e r m o d y n a m i c s , in a general sense , t o examine clay and o t h e r auth igen ic minera l equ i l ib r ia . O t h e r papers that c o n s i d e r the chemis t ry and o r ig in of p o r e f lu ids i n c l u d e t h o s e of C h a v e (1960), Siever ef al. (1965), and W h i t e (1965). P r o b l e m s assoc ia ted w i th de f in ing a "s tab le s y s t e m " a n d in d e t e r m i n i n g the s t o i c h i o m e t r y of the clay phases i nvo l ved in l o w temperatu re d iagenet ic react ions have p r o m p t e d m a n y invest igators in the past to avo id similar analyses. Papers by Sarkisyan (1972), H o w e r ef al. (1976), H a n c o c k and Taylor (1978), F o s c o l o s and P o w e l l (1978), P o w e l l ef al. (1978), H o w e r (1981), Bruce (1984), F o s c o l o s (1984), and S r o d o n and Eberl (1984) represent just a f ract ion of the l iterature that has b e e n wr i t ten o n shale d iagenes is . D iagene t i c changes s u c h as the p rogress ive i l l i t izat ion of smect i te w i th d e p t h have b e e n d i s c u s s e d by Burst (1969), F o s c o l o s and K o d a m a (1974) and Bruce (1984). Re lated stud ies by Reyno lds and H o w e r (1970) a n d S r o d o n (1980) have d e v e l o p e d relatively soph is t ica ted ways of ca lcu la t ing the relative p r o p o r t i o n s of illite and smect i te in m i x e d - l a y e r e d clays based o n X R D analyses. C h a n g e s in 1.0 n m peak shape f r o m X R D analyses ( d e v e l o p e d by Weaver (1961) and Kubler (1966)) are commonly used (Foscolos et al., 1976) to index and predict diagenetic stages in strata. Clay diagenesis of the Eureka Sound Formation has been briefly examined by Bustin and Bayliss (1979) in the area of Fosheim Peninsula. • . . ORGANIC MATURATION Tradit ional ly , pressure and temperatu re i n fo rmat ion has b e e n ext racted f r o m strata by analys ing o rgan ic and inorgan ic maturat ion parameters . C lay mineral assemblages arid re lated d iagenet ic parameters w e r e o n c e t h o u g h t . to ref lect m a x i m u m tempera tu re and pressure c o n d i t i o n s atta ined (Burst, 1969) but it has s ince b e e n s h o w n ( D e S e g o n z a c , 1970; F o s c o l o s ef al., 1976, 1978; H o w e r ef al., 1976) a n d is n o w c o m m o n l y a c c e p t e d that clay minerals are equal ly as sensit ive t o thei r g e o c h e m i c a l e n v i r o n m e n t ( p H , Eh, ca t ion activit ies, etc . ) as they are to thei r physical e n v i r o n m m e n t (pressure and temperature) ; see f o l l o w i n g chapter . As a result, the use of stable(?) c lay assemblages as g e o t h e r m o m e t e r s a n d / o r g e o b a r o m e t e r s is l imi ted unless const ra in ts o n the g e o c h e m i c a l e n v i r o n m e n t are k n o w n ( H u t c h e o n ef al., 1980). The p re fe r red m e t h o d for ca lcu lat ing the m a x i m u m temperatu re at ta ined in a s e q u e n c e of strata is by measur ing the m e a n m a x i m u m re f lectance ( R 0 m a x ) of vitrinite and p e r f o r m i n g a t ime—temperature maturat ion analysis (after Lopat in , 1971 ; W a p l e s , 1980; M i d d l e t o n , 1982). Un l i ke minera l m e t a m o r p h i s m , vitr inite maturat ion d o e s no t u n d e r g o ret rograde m e t a m o r p h i s m and is, there fore , a relatively rel iable ind icator of the m a x i m u m atta ined temperatu re . Stud ies by Lopat in (1971), D o w (1977) and M i d d l e t o n (1982) have s h o w n that R 0 m a x increases linearally a n d exponent ia l l y w i t h increases, respect ively , in t ime and temperatu re . Recent studies by H u t t o n ef al. (1980), Fujii ef al. (1982) and Price ef al. (1985) have s h o w n that a l though coa l i f i ca t ion is general ly c o n s i d e r e d t o be una f fec ted by pressure ( H u t t o n ef al. (1980)), increases in the H / C ratio of vitr inite a n d assoc ia ted macerals may suppress the re f lectance of vitr inite. As a result, if v itr in ite re f lectance is t o be u s e d as a reliable paleothermometer close attention must be paid by the investigator to the variations in microlithotypes (i.e., increases in exinitic component) and vitrinite types with depth. This chapter examines the studied section for trends in coalification, estimates the maximum depth of burial of the strata and the geothermal gradient and makes inferences about the thermal and baric evolution of the section. E X P E R I M E N T A L S a m p l e P r e p a r a t i o n Forty samples were chosen for R 0 m a x analysis from the approximately 3000 m of section. Both kerogen concentrates (phytoclasts) and coals were examined. R 0 max measurements from the upper half of the studied section were taken primarily from coals that were grab—sampled at approximately 40—50 m intervals. The relative absence of true. coal seams from the lower half of the section required that R 0 m a x measurements be made on phytoclasts. Samples from the lower half of the section were collected from approximately 100—150 m intervals. Coal Pellets Coal pellets were prepared using methods modified from Bustin (1977). The samples were initially crushed with a mortar to reduce the coal fragment size to approximately 850 jum. The less than 850 fxm fraction was then separated from trie larger fraction. by sieving with a 60 U.S. mesh sieve. That portion that was finer than 60 U.S. mesh was collected and used in the pellets. A 1:3 mixture of the < 8 5 0 c o a l a n d Transoptic® p o w d e r was then p l a c e d in a hydraul ic Bueh le r P n e u m e t I® pe l le t press and h e a t e d for 12—15 minutes . O n c e a temperature of 100 ° C was attained a pressure of 3.5 KPa was a p p l i e d and the mixture was a l l o w e d t o c o o l under pressure f o r 15 minutes . Po l i sh ing was left until immed ia te l y be fo re the opera to r was p r e p a r e d t o p r o c e e d w i t h R 0 m a x m e a s u r e m e n t s in o r d e r t o m i n i m i z e the o x i d a t i o n o f the vitr inite. O n c e p o l i s h e d , t h e samples w e r e left in a d e s i c c a t o r under h e l i u m fo r n o longer than 48 hours p r io r to b e i n g analysed. Phytoclast Pellets Phytoc last concent ra tes w e r e p repa red us ing m e t h o d s m o d i f i e d f r o m Bost ick a n d A l p e r n (1977). Shale samp les w e r e initially c r u s h e d in a mortar to r e d u c e the f ragment s ize t o 1 m m 3 . Samples w e r e t h e n p l a c e d in 1 litre b u c k e t s c o n t a i n i n g 1 0 0 % h y d r o c h l o r i c ac id a n d left for 24 hours in o rde r t o r e m o v e any carbonates present . The H C I bath was f o l l o w e d w i t h 4 r inses w i th tap wate r separa ted by 24 h o u r set t l ing pe r iods . Si l ica was next r e m o v e d by leaving the samples in 4 8 % hydro f l uo r ic ac id for 3 days. A n y residual coarse sil ica was r e m o v e d by s iev ing the p r o d u c t a n d retain ing the f ine f ract ion . Pel let p reparat ion f o l l o w e d the t e c h n i q u e s o u t l i n e d in the p r e c e d i n g paragraph o n c o a l pe l let p reparat ion . Analytical Techniques Al l samples w e r e analysed in a c c o r d a n c e w i th A S T M p r o c e d u r e s ( A S T M D 2 7 9 7 , 1980). Po l i shed .pellets w e r e e x a m i n e d o n a Leitz M P V 2 m i c r o s c o p e e q u i p p e d w i t h a 50x o i l i m m e r s i o n ob jec t i ve , 10x ocular , stable vo l tage supply , p h o t o m u l t i p l i e r , and c o m p u t e r assisted data c o l l e c t o r . The s ize o f the l imit ing aperture u s e d was 8 urn . M e a s u r e m e n t s w e r e taken w h i l e the stage was rotated at a rate of app rox imate l y 360 °/7 s e c o n d s . Immers ion o i l w i t h a refractive index of 1.515 was u s e d . Fifty m e a s u r e m e n t s w e r e taken per samp le w i th the system b e i n g recal ibrated against the standard after every 25 measu rements . If the cal ibrat ion was out by m o r e than 0 .02% at the e n d of a run, the run was d i s c a r d e d and r e d o n e . M o s t R 0 m a x read ings w e r e taken f r o m te loco l l i n i te w i th d e s m o c o l l i n i t e b e i n g m e a s u r e d if t e loco l l i n i te p r o p o r t i o n s w e r e l o w . N o n - s p e c i f i c vitr inite was m e a s u r e d in the shale samples . For a deta i led d e s c r i p t i o n of the opt ica l p roper t ies of vitr inite, the theory b e h i n d measur ing vitr inite re f lectance , and the m e c h a n i c s of the ref lectance m i c r o s c o p e refer to Bustin et al. (1983). Elemental Analysis A representat ive sample f r o m b o t h the coa ls and the phytoc las ts was c h o s e n for C H N e lementa l analysis to d e t e r m i n e if variations exist in the H / C ratios of the t w o s a m p l e g r o u p s . Each sample was analysed t w i c e f r o m separate " m a s k e d " vials t o ensure accuracy w i th in 0 .5%. The t w o samples c h o s e n for e lementa l analyses are ind ica ted o n f igure 5. Time—Temperature Model O n e o f the m e t h o d s u s e d to calculate the m a x i m u m p a l e o t e m p e r a t u r e at ta ined in the s t u d i e d strata is Lopat in 's (1971) t ime—temperature m o d e l (Waples , 1980). In app ly ing Lopat in 's m o d e l to the Eureka S o u n d Strata at Strand Fiord a n u m b e r assumpt ions , w e r e m a d e regard ing the t e c t o n i c h istory and thermal p roper t ies of the strata. First, fo r the sake of s impl ic i ty the rates of s u b s i d e n c e and uplift are a s s u m e d t o b e un i fo rm . S e c o n d , heat f l o w a n d thermal conduct i v i t i es are a s s u m e d to b e constant (Lopat in , 1971). Th i rd , the act ivat ion energy for the ent i re range of maturat ion is a s s u m e d to be constant . The basic p remise of Lopat in 's TTl m o d e l states that k e r o g e n maturat ion is s imp ly a f u n c t i o n of t ime a n d temperatu re . A n increase in temperature of 10°C wi l l result in a d o u b l i n g of the maturat ion level , thus, de f in ing an exponent ia l re la t ionsh ip e x p r e s s e d by the e q u a t i o n : n 7 = r w h e r e , 7 = factor w h i c h relates the e x p o n e n t i a l d e p e n d e n c e of maturat ion to temperature . r = factor by w h i c h the rate o f maturat ion increases fo r every 10°C increase in temperatu re . r = 2 if o n e assumes that e a c h increase in temperature of 10°C p r o d u c e s a d o u b l i n g . i n the rate o f increase in maturat ion leve l (Waples , 1980). n = temperature interval i ndex value. A l inear re lat ionsh ip exists b e t w e e n maturat ion and the length of t ime that a sed imentary package has b e e n e x p o s e d to a g i ven a m o u n t of heat. D o u b l i n g the heat ing t i m e wi l l result in a t w o fo ld increase in maturat ion fo r any g i ven temperatu re . Lopat in 's e q u a t i o n fo r the total matur ity (TTl) of any s e d i m e n t is g iven by: nmax TTl = L ( A T ) <r n) n ; = n m m w h e r e , n m i n = smal lest n - index value e n c o u n t e r e d , nmax = largest n - index value e n c o u n t e r e d . A T ^ = length of t i m e spent by s e d i m e n t in tempera tu re interval /'. The c o m p u t e r m o d e l used in this s tudy uses the integrated f o r m of Lopat in 's (1971) m o d e l ; e x p r e s s e d as f o l l ows : TTI = f2(T(t ) -105) /10 dt w h e r e T(t) is the temperature ( ° C ) as a f u n c t i o n of t ime w i t h t 0 b e i n g t h e t ime of d e p o s i t i o n and t be ing the t i m e at present . R E S U L T S A N D D I S C U S S I O N C o a l i f i c a t i o n G r a d i e n t s C o a l rank was general ly f o u n d to increase w i th increas ing d e p t h f r o m s u b — b i t u m i n o u s A / h i g h volat i le b i t u m i n o u s C t o h igh volat i le b i t u m i n o u s B. At app rox imate l y 1400 m above the base of the s e c t i o n there is an apparent decrease in the re f lec tance values and c h a n g e in the coa l i f icat ion gradient . W h e t h e r this c h a n g e in the coa l i f icat ion gradient is real o r no t is d i s c u s s e d later. A n u m b e r of R 0 m a x versus d e p t h curves w e r e tes ted t o d e t e r m i n e the 'best f i t t ing ' coa l i f i ca t ion gradient fo r the m e a s u r e d gradients . B o t h ar i thmet ic (Fig. 4) and s e m i l o g (Fig. 5) p lo ts w e r e analysed. In e a c h case, the data w e r e t reated as rep resent ing first a s ingle p o p u l a t i o n and s e c o n d t w o separate p o p u l a t i o n s of po in ts ; namely coa ls in the u p p e r p o p u l a t i o n and phytoc lasts in the l o w e r p o p u l a t i o n . For b o t h the s e m i l o g and the ar i thmet ic t reatments it was f o u n d that curve—fits w e r e i m p r o v e d w h e n t h e . data w e r e a s s u m e d t o represent t w o separate p o p u l a t i o n s of po in ts . For e x a m p l e , the r 2 values fo r the data assuming a s ing le p o p u l a t i o n w e r e 0.172 fo r the s e m i l o g t reatment a n d 0.176 for the ar i thmet ic t reatment . By assuming 17 3 0 0 0 2 5 0 0 2 © to CO m © > o < cp X 2 0 0 0 -1 5 0 0 -1 0 0 0 5 0 0 -0.4 ^—*v~t \ \ * \ ^ \ \» A=C0AL -|- =PHYT0CLAST 4\ \ ' 2 : 0 - 4 9 9 \ \ \ A r 2 :0.340 N N \ V \ \ + \ \ + N \ \ \ \ \ \ + \ N + \ \ \ \ N i 1 1 i 1 1 r 0.5 0.6 1 1 1 1 1 T 1 1 1 0.7 0.8 0 R 0max F i g u r e 4- A r i t hmet ic p lot of mean m a x i m u m ref lectance versus d e p t h s h o w i n g regress ion l ines and c o r r e s p o n d i n g r -squared values t h r o u g h the 3 poss ib le p o p u l a t i o n s (upper p o p u l a t i o n c o n s i s t i n g primari ly of coa l , l o w e r p o p u l a t i o n cons i s t i ng of phytoclasts , s ingle p o p u l a t i o n cons i s t i ng of entire sect ion ) . 0.1 0.2 0.3 0.5 1.0 R Q max Figure 5- Semilog plot of mean maximum reflectance versus depth showing regression lines and corresponding r-squared values through - the 3 possible populations (upper population consisting primarily of coal, lower population consisting of phytoclasts, single population consisting of entire section). two separate populations, the r2 values for the semilog plot were 0.484 (upper population) and 0.318 (lower population). Corresponding arithmetic values were 0.49 and 0.34, respectively. Statistical Considerations Given the low coefficient—of—determination (r2) values and relatively small sample sizes, depth and thermal modelling of the studied strata using any of the above mentioned curves yield results with a good deal of uncertainty. The following sections, therefore, attempt to minimize this uncertainty by adjusting, where necessary, the various gradients such that they are in relative agreement with published local tectonic models. A literal interpretation of the r 2 statistic states that for an r 2 value of 0.49 (i.e., as seen in the arithmetic fit of the upper population) only 49.9% of the variability in R0max values can be explained by the depth values. From the present study this suggests that, at best, 50% of the variability in R0max must be explained in terms of some other variable(s). If the entire section was considered (r2 = 0.172, semilog) at least 82% of the variability in R0max would have to be explained in terms of some variable other than depth. The following sections discuss a number of factors which are believed to contribute to at least some of the remaining variability in observed R0max values. Consideration of R0max Distribution with Depth A r i t h m e t i c fits of the data w e r e f o u n d t o be cons is tent l y bet ter than s e m i l o g fits for any g iven d e p t h interval . Similar f ind ings have b e e n r e p o r t e d in s tud ies by England (1984) and Mof fa t (1985) in areas w i t h cons ide rab l y d i f ferent t e c t o n i c h istor ies than Strand F iord . In genera l , coa l i f icat ion gradients in these o t h e r areas w e r e f o u n d to be ar i thmet ic o n l y in areas w h e r e thermal d i sequ i l i b r i um w i t h b a s e m e n t heat f lux was s u s p e c t e d . In add i t i on , the ar i thmet ic re lat ionsh ip b e t w e e n R 0 m a x and d e p t h d id no t e x t e n d o v e r the full range of R 0 m a x values but was restr icted t o values b e l o w 0 . 3 5 % re f lectance . S u c h c o n d i t i o n s w e r e s u g g e s t e d t o have b e e n c reated by rapid basin inf i l l ing and short s e d i m e n t r e s i d e n c e t imes. Thermal d i sequ i l i b r ium may b e p o s s i b l e at Strand Fiord but for reasons o t h e r than rapid s e d i m e n t load ing and u n l o a d i n g as, a l though s e d i m e n t a c c u m u l a t i o n rates w e r e relatively h igh (approx imate ly 120 m per mi l l i on years), r e s i d e n c e t imes w e r e genera l ly l o n g (Balkwil l , 1978). Therma l d i sequ i l i b r ium at Strand F iord , if it exists, is m o s t l ikely re lated t o the p r e s e n c e of the n u m e r o u s evapor i te diapirs in the study area. The c o n c e p t of h o t diapir int rus ions a f fect ing their su r round ing s e d i m e n t is no t u n i q u e as ind ica ted by Balkwil l (1973) w h e r e the fo rmat ion of horn fe ls adjacent t o diapirs is att r ibuted to s u c h a p h e n o m e n u m . At Strand Fiord, h o w e v e r , thermal d i sequ i l i b r i um b e t w e e n the diapirs and the coals is s u s p e c t e d and b e l i e v e d to have resu l ted in part f r o m rapid e m p l a c e m e n t and u n r o o t i n g of a diapir w h i c h w o u l d , theoret ica l ly , have a similar loca l e f fect as rapid d e p o s i t i o n and u n l o a d i n g of s e d i m e n t s . Heat der i ved f r o m d e p t h w h i l e the d iap i r r ema ined r o o t e d w o u l d be transfered t h r o u g h the diapir and into the s u r r o u n d i n g rock . U p o n b e c o m i n g u n r o o t e d , heat c o n d u c t i o n f r o m the s o u r c e at d e p t h w o u l d cease and the tempera tu re in the i so la ted d iapi r w o u l d d r o p . This theory is substant iated by Selig and Wa l l i ck (1966) w h o f ind that as the separat ion d is tance of an iso lated diapir f rom its s o u r c e increases, the geo the rma l grad ient in the sed iments over ly ing the diapir dec reases . If the p r o c e s s was suf f ic ient ly rapid , thermal equ i l i b r i um w i th the s u r r o u n d i n g rocks may never be atta ined. The result w o u l d be a general dev ia t ion o f the coa l i f icat ion gradient f r o m the p r e d i c t e d log—l inear d is t r ibut ion . A n o t h e r factor w h i c h may cont r ibu te to the dev ia t ion of the coa l i f icat ion gradient away f r o m a log—l inear d is t r ibut ion may b e s e e n in e x a m i n i n g the fundamenta l assumpt ions under l y ing the coa l i f icat ion p rocess . Karwei l (1956) d e f i n e d coa l i f i ca t ion as a t ime / tempera tu re p rocess w h i c h c o u l d be e x p l a i n e d in terms of first o r d e r react ion k inet ics , stat ing that maturat ion ( R 0 m a x ) rate varies log—l inear ly w i t h temperatu re . Lopat in (1971) also used first o r d e r react ion k inet ics t o p red ic t maturat ion level . Recent s tud ies by Price (1983) and Barker (1983) have sugges ted , • h o w e v e r , that the maturat ion p r o c e s s is not p rope r l y e x p l a i n e d us ing first o rde r k inet ics and that coa l i f icat ion is m o r e likely a 'mu l t i—order ' k inet ics p h e n o m e n a that is a f u n c t i o n of t ime on ly dur ing the early stages of the react ion . Barker 's (1983) f ind ings state that the thermal maturat ion p r o c e s s is m o r e s t rong ly temperature d e p e n d e n t than prev ious ly real ized and that maturat ion react ions may p r o c e e d to c o m p l e t i o n in as little as 1,000 t o 10,000 years. In short , v itr inite re f lectance is b e l i e v e d by these authors to be an abso lute , rather than a t ime d e p e n d a n t , g e o t h e r m o m e t e r . There never the less remains a g o o d dea l of c o n t r o v e r s y as to w h e t h e r vitr inite re f lectance is an abso lute rather than t ime d e p e n d e n t g e o t h e r m o m e t e r . If re f lectance is an abso lute g e o t h e r m o m e t e r , a log—l inear p lot of R 0 m a x versus d e p t h w o u l d on ly p r o d u c e a straight l ine plo.t if e a c h g i ven d e p t h i n c r e m e n t w e r e to c o r r e s p o n d to a constant t e m p e r a t u r e inc rement . This w o u l d on ly o c c u r u n d e r c o n d i t i o n s of a cons tan t g e o t h e r m a l grad ient and un i fo rm heat f l o w t h r o u g h o u t the s e c t i o n . As is d i s c u s s e d in the f o l l o w i n g paragraph, u n i f o r m e d thermal conduct i v i t i es and , there fore , a cons is tent g e o t h e r m a l gradient t h r o u g h the Strand F iord s e c t i o n is a p o o r a s s u m p t i o n and , there fo re , a log—l inear coa l i f i ca t ion grad ient is no t to be e x p e c t e d . Consideration of Shifts in Coalification Gradient A n examina t ion of the R 0 m a x d is t r ibut ion w i t h d e p t h reveals a s e c o n d e n i g m a w h i c h must be c o n s i d e r e d — h o w can the apparent shift in the coa l i f i ca t ion gradient at 1400 m and apparent ly r a n d o m d is t r ibut ion of R 0 m a x values b e l o w that d e p t h b e exp la ined? The f o l l o w i n g d i scuss ion r e c o g n i s e s f lu id migrat ion of h e a t e d d iap i r—der ived waters as b e i n g the pr imary factor in exp la in ing the o b s e r v e d shift in the coa l i f i ca t ion gradient . This theo ry is s u p p o r t e d by s a n d s t o n e d iagenes is f ind ings w h i c h are d i s c u s s e d in a later s e c t i o n . A n u m b e r of m i n o r factors w h i c h may c o n t r i b u t e t o p r o d u c i n g the o b s e r v e d offset in the coa l i f i ca t ion gradient are also i n c l u d e d in the f o l l o w i n g d i s c u s s i o n . Similar shifts in coa l i f icat ion gradients have b e e n e x p l a i n e d in o the r s tudy areas (Bust in , 1983 ; Eng land , 1985) by the p r e s e n c e of thrust faults. The o c c u r r e n c e of a major thrust fault in the s tudy area is highly i m p r o b a b l e for a n u m b e r of reasons. First, there is g o o d l i thostrat igraphic cont inu i ty b e t w e e n units b o t h a b o v e and b e l o w the R 0 m a x break (Ricketts and M c l n t y r e , pers. comm.). S e c o n d , there is n o structural e v i d e n c e that w o u l d suggest a thrust fault t h r o u g h the s t u d i e d s e c t i o n o r assoc ia ted g e o l o g y . Th i rd , a thrust fault w i th a c o n s i d e r a b l e amount of t h r o w w o u l d be requ i red t o p r o d u c e the o b s e r v e d shift in the R 0 m a x gradient . N o f ie ld e v i d e n c e in s u p p o r t of s u c h a st ructure was o b s e r v e d o r has b e e n prev ious ly reported in the literature.. Lithology and fracture controlled migration of fluids is believed to exert the primary control on the observed shift in the coalification gradient. The present model proposes selective horizontal migration of heated pore fluids from diapirs into stratigraphicaliy adjacent permeable lithologies. Studies by Hitchon (1984) and Nurkowski (1984) have suggested that the heat carried by ground waters has a significant effect on the maturation of vitrinite. Given that coal seams serve as better aquifers than shales (from which the phytoclasts were extracted) the maturation effect of the heated diapir—derived waters would be observed primarily in vitrinite from lithologies with the greatest permeabilities; specifically, fractured coals rather than the tight shales. Again, if thermal equilibrium was not attained, the result would be a shifting of the upper curve toward higher reflectance values and a deviation from a log—linear curve. The present study's results from the elemental analyses (Table 1) of the coal and phytoclast sample support the idea that the offset in the coalification gradient is of a chemical, rather than compositional, nature. In the past, it has generally been regarded that there is no appreciable difference in R 0 m a x values extracted from coals and R 0 m a x values obtained from associated phytoclasts, however, recent studies by Price ef al. (1985) and Fuji ef al. (1985) have shown that this is not always true. Increased exinitic components in coal and even increased proportions of H/C in the vitrinite can result in suppression of R 0 . In the present study the coal sample was found to have a higher H/C ratio than the phytoclast of lower reflectance. Although these findings do support the idea that the permeable coals have matured preferentially as a result of being in contact with heated waters they also suggest that oxidative degradation of the coals associated with the horizontal TABLE 1 C H N E lementa l Analysis of O r g a n i c M a t t e r (%) Sample C H_ H H / C R A K - 6 2 - 2 5 44 .09 3.51 1.39 0.079 44 .14 3.50 1.37 0.079 R A K - 2 7 - 2 5 69.95 4 .74 1.01 0.067 70.41 4 .85 1.02 0.068 migrat ion of wate r may have o c c u r r e d . . A final c o n t r i b u t i o n t o p r o d u c i n g the of fset in the coa l i f i ca t ion gradient may c o m e f r o m the d i f fe rences in thermal c o n d u c t i v i t i e s of the t w o s e g m e n t s of s e c t i o n (Gretener , 1981). W h e n c o m p l e t e sed imentary packages are c o n s i d e r e d , an average thermal c o n d u c t i v i t y may be ass igned to the package based o n t h e relative p r o p o r t i o n s of sands tone and shale (assuming, of course , that the average thermal c o n d u c t i v i t y of a package is a l inear c o m b i n a t i o n of the c o n d u c t i v i t i e s of the ind iv idua l l i thotypes (Mof fat , 1985)). A s s u m i n g that this is the case , the s e c t i o n o c c u r i n g b e l o w 1400 m, c o n s i s t i n g of app rox imate l y 8 0 — 9 0 % shale and o n l y about 10—20% s a n d s t o n e , w o u l d have a bu lk thermal c o n d u c t i v i t y of 1.8—2.0 W /m°C . A b o v e 1400 m, the s e c t i o n is c o n s i d e r a b l y r icher in coa l and s a n d s t o n e (approx imate ly 60—65%) than shale (35—40%) the reby p r o d u c i n g an average bulk thermal c o n d u c t i v i t y of a p p r o x i m a t e l y 2.8—2.9 W /m°C . This d i f fe rence in thermal c o n d u c t i v i t i e s w o u l d p r o d u c e d i f fe rence in the g e o t h e r m a l grad ients b e t w e e n the t w o packages of up to 20°C/km if it is a s s u m e d that heat f l o w is un i f o rm t h r o u g h o u t the s e c t i o n . If the primary heat s o u r c e is the diapir, w h i c h is stratigraphical ly adjacent to , rather than b e n e a t h , the s e c t i o n it is poss ib le to env isage an of fset in the coa l i f icat ion gradient resul t ing f r o m n o n — u n i f o r m ho r i zon ta l heat f l ow. The result is that the o b s e r v e d shift in the coa l i f icat ion gradient is m o r e l ikely a f u n c t i o n of the thermal conduct i v i t i es and permeabi l i t ies of the t w o packages rather than the t e c t o n i c history of the s e c t i o n . It was d e c i d e d t o m o d e l the coa l i f i ca t ion gradients d e t e r m i n e d f r o m the s e m i l o g p lo ts b e c a u s e the maturat ion m o d e l u s e d later in this s tudy assumes an e x p o n e n t i a l increase in maturat ion rate (i.e., R 0 m a x ) w i t h increas ing tempera tu re (i.e., depth ) . The coa l i f icat ion gradient f rom the s t u d i e d s e c t i o n was, there fore , f o u n d t o be 0 .127 % l o g R 0 m a x / k m ( r 2 =0 .484 ) as d e t e r m i n e d f r o m a s e m i l o g analysis of the u p p e r p o p u l a t i o n of po ints . P a l e o — d e p t h o f B u r i a l The p r e — t e c t o n i c th ickness of s e d i m e n t f rom a s e c t i o n of strata has b e e n ca lcu la ted by ext rapo lat ing the coa l i f icat ion gradient to a d e p t h w h i c h c o r r e s p o n d s to a zero—matur i ty level . This zero—matur i ty leve l usually c o r r e s p o n d s to an R 0 m a x value of 0 . 15% o r 0 . 2 0 % ( M i d d l e t o n , 1982). The present s tudy uses a zero—matur i ty value of 0 . 1 5 % R 0 m a x as a prev ious s tudy by Bust in (in press) has d e t e r m i n e d that R 0 m a x values as l o w as 0 .15% d o o c c u r t h r o u g h o u t the C a n a d i a n A r c t i c A r c h i p e l a g o . P a l e o ^ J e p t h of burial ca lcu lat ions d e t e r m i n e d that as m u c h as 4100 m of s e d i m e n t may have b e e n e r o d e d f r o m a b o v e the s t u d i e d s e c t i o n at Strand F iord (Figure 9). This w o u l d suggest a p re—tec ton ic th ickness of the Eureka S o u n d Format ion at Strand Fiord o f up to 6800 m. Prev ious ly r e p o r t e d p r e t e c t o n i c th icknesses of s y n — a n d p o s t — E u r e k a S o u n d s e d i m e n t s are r e p o r t e d by Bust in ef al. (1977) f r o m F o s h e i m Pen insu la and M a y Po in t w h e r e values of 3500 and 2500 m, respect ive ly , w e r e d e t e r m i n e d . Bust in (/n press) reports Eureka S o u n d Fo rmat ion d e p t h s of burial of u p to 6000 m f rom M e i g h e n Island. A t Strand F iord p rev ious studies w e r e unab le t o d e t e r m i n e a coa l i f i ca t ion gradient and , there fo re , a p r e — t e c t o n i c th ickness b e c a u s e of a general lack of data. Bust in (1977) e s t i m a t e d a M i d E o c e n e th ickness of approx imate l y 3200 meters b a s e d o n his p a l e o — r e c o n s t r u c t i o n of the area. The p resent s tudy 's f ind ings, if c o r r e c t e d for the d iap i r— induced maturat ion , are in partial a g r e e m e n t w i t h Bust in 's (1977) m o d e l . T h e gradient was c o r r e c t e d for d i a p i r — i n d u c e d maturat ion by shi f t ing the coa l i f icat ion curve t o the left unt i l an R 0 m a x value of 0 . 5 0 % c o r r e s p o n d e d t o a p o s i t i o n in the s e c t i o n of 1400 m a b o v e the base of the s e c t i o n . This was d o n e in o rde r t o align the u p p e r coa l i f i ca t ion gradient w i th the l o w e r coa l i f icat ion gradient . In m o d e l l i n g the c o r r e c t e d gradient it was a s s u m e d that o n l y the position, rather than the slope, of the grad ient was a f fected by the diapir . Sixty e ight h u n d r e d metres of burial w o u l d represent the abso lu te m a x i m u m p o s s i b l e d e p t h of burial if the ef fects of h igh heat f l o w and , there fore , d iap i r -Wnduced thermal maturat ion w e r e abso lute ly m in ima l . A m i n i m u m , a n d perhaps m o r e real ist ic value f o r . the m a x i m u m d e p t h of burial c o u l d be est imated by e x a m i n i n g the c o r r e c t e d gradient w h i c h attr ibutes the p o s i t i o n i n g of the u p p e r coa l i f i ca t ion gradient to heat f l o w anomal ies . The adjusted d e p t h of burial , f r o m w h i c h the sha l lowest poss ib le d e p t h of burial was d e t e r m i n e d , was ca lcu la ted to be approx imate l y 2500 meters , w h i c h gives a tota l p r e — t e c t o n i c th ickness of 5200 m. This ad justed va lue is in bet te r a g r e e m e n t than the n o n — c o r r e c t e d value of 6800 m w i t h p rev ious ly p u b l i s h e d p a l e o — r e c o n s t r u c t i o n s of the Sverd rup Basin. Maximum Pressure Considerations A n u m b e r of assumpt ions regard ing the dens i ty a n d pressure d is t r ibut ion of the over l y ing strata make it p o s s i b l e to est imate the pressure at the base of the s e c t i o n . First, b e c a u s e s e d i m e n t a c c u m u l a t i o n rate w a s relatively h igh (Balkwi l l , 1978) and the m o d e l l e d heat s o u r c e is d iap i r—der ived waters it was a s s u m e d that the pressure at d e p t h was w h o l l y hydrostat ic . By m o d e l l i n g the pressure t o b e entirely hydrostat ic it is a s s u m e d that t he re has b e e n a re laxat ion of all c r e e p related shear ing st resses at d e p t h ( H o b b s et a / . , 1976). T h e hydrostat ic p ressure at d e p t h (h) is e q u a l t o p g h w h e r e p is the dens i ty of the over ly ing rock and g is the acce le ra t ion d u e to gravity. As the l i t ho log ic p r o p o r t i o n s of the r e m o v e d s e c t i o n are u n k n o w n t h e hydrostat ic pressure was ca lcu lated a s s u m i n g that the 5200 m of s e d i m e n t c o n s i s t e d first of 1 0 0 % s a n d s t o n e w i th 1 0 % p o r o s t i y ( p = 2.5 c m 3 (Clark, 1967)) and s e c o n d of 1 0 0 % shale ( p = 2.25 c m 3 at 2500 m d e p t h , 2.38 c m 3 at 4100 m d e p t h and 2.42 c m 3 at 5200 m d e p t h (Clark, 1967)). G i v e n t h e n that the actual strata c o n s i s t e d of s o m e c o m b i n a t i o n of the t w o l i tho log ies , the actual p ressure w o u l d l ie s o m e w h e r e b e t w e e n these t w o va lues (Figure 6). The results ind icate that t h e total hydrostat ic p ressure at the 1400 m mark ranges f r o m 95 M P a f o r p u r e shale to 100 M P a fo r pure s a n d s t o n e . Va lues f r o m the t o p of the s e c t i o n are 55 M P a and 61 M P a fo r pure shales a n d s a n d s t o n e s , respect ive ly . M a x i m u m pressures at the base of the Eureka S o u n d Fo rmat ion are 123 M P a (pure shale) and 127 M P a (pure sands tone ) . 28 40 0.0 -*-Hydrostat ic P r e s s u r e in M e g a p a s c a l s 60 80 1 0 0 1 2 0 1 40 Figure 6- Hydros ta t ic pressure d is t r ibut ion t h r o u g h s tud ied s e c t i o n assuming a m a x i m u m d e p t h of burial of 5500 metres . Pressure brackets w e r e ca lcu la ted using saturated bulk dens i t ies for 1 0 0 % pure s a n d s t o n e and 1 0 0 % pure shale. P a l e o — g e o t h e r m a l G r a d i e n t T o m o d e l the p a l e o - g e o t h e r m a l gradient us ing Lopat in 's m e t h o d the burial h istory of the strata must be k n o w n . At Strand Fiord the basal strata of the Eureka S o u n d Format ion w e r e d e p o s i t e d app rox imate l y 70 M a wi th basin inf i l l ing and s u b s i d e n c e o c c u r r i n g up unti l 35 M a . B e t w e e n 62 and 66 M a d e p o s i t i o n c e a s e d , as s h o w n by the d i s c o n f o r m i t y b e t w e e n unit 2 (the wave d o m i n a t e d de l ta strand plain) a n d unit 3 (the marine shale) (Ricketts a n d M c l n t y r e , pe rs . c o m m . ) . G o i n g d o w n s e c t i o n at approx imate ly 35 M a reg iona l upli ft and e r o s i o n te rm ina ted the inf i l l ing of the Sverdrup Basin at Strand F iord . Figure 7 out l ines the t e c t o n i c h istory u s e d t o ca lcu late g e o t h e r m a l gradients (using Lopat in 's (1971) m e t h o d ) of the Eureka S o u n d F o r m a t i o n at Strand F iord . Figure 8 out l ines the t e c t o n i c h istory us ing the c o r r e c t e d d e p t h of burial . P r e d i c t e d curves (geotherma l gradients) gene ra ted f r o m Lopat in ' s m o d e l b a s e d o n the a b o v e m e n t i o n e d d e p o s i t i o n a l and t e c t o n i c history of the Eureka S o u n d Fo rmat ion at Strand F iord are s h o w n in f igures 9 ( n o n — c o r r e c t e d ) and 10 (cor rected) . . The ca lcu la ted g e o t h e r m a l gradient f r o m the study area is also p l o t t e d in Figures 9 and 10. A numer ica l value for the ca lcu la ted g e o t h e r m a l gradient (18.3°C/km) was d e t e r m i n e d by p e r f o r m i n g a least squares reg ress ion analysis of the g e o t h e r m a l gradient (GTG) versus c o r r e s p o n d i n g l og coa l i f icat ion gradients ( l o g C G ) . T h e re lat ionship b e t w e e n G T G and l o g C G at Strand Fiord is as fo l l ows : G T G = 1 6 0 . 4 0 * ( l o g C G ) - 2 . 0 4 1 1 , r 2 = 0.98 U s i n g the prev ious ly ca lcu la ted g e o t h e r m a l gradient , the m a x i m u m atta ined pa leo—tempera tu re was 75 ° C at the po in t w h e r e the shift o c c u r s in the coa l i f icat ion grad ient (i.e., 1400 m f r o m the base of the sect ion ) and 45 ° C at the top . The Tectonic History M a B P 7.0 J Figure 7- Representat ion of the t e c t o n i c e v o l u t i o n of Eureka S o u n d strata at Strand Fiord assuming a m a x i m u m d e p t h of burial o f 6800 metres. Figure 8- Representat ion of the t e c t o n i c e v o l u t i o n of Eureka S o u n d strata at Strand Fiord assuming a m a x i m u m d e p t h of burial o f 5500 metres. F i g u r e 9- G e o t h e r m a l gradient de te rm ina t i on us ing Lopat in 's (1971) m e t h o d and assuming a m a x i m u m d e p t h of burial of 6800 met res . Corrected Geothermal Gradients % R o M a x 0.1 0.2 0.3 O.S 1.0 2.0 3.0 5.0 F i g u r e TO- C e o t h e r m a l gradient de te rm ina t i on using Lopat in 's (1971) m e t h o d and assuming a m a x i m u m d e p t h of burial of 5500 met res . m a x i m u m tempera tu re at the base o f the s e c t i o n was 95 °C us ing Lopat in 's (1971) TTl m o d e l . C o r r e s p o n d i n g m a x i m u m temperatures us ing Barker 's (1983) m e t h o d are 14°C (0 .50% R 0 m a x ) at the t o p of the s e c t i o n and 83°C (0 .80% R 0 m a x ) at the 1400 m mark. D i sc repanc ies in the temperature values d e t e r m i n e d f r o m the t w o m o d e l s can be att r ibuted to a n u m b e r of factors. First, c o n s i d e r i n g the p o o r fits f r o m the coa l i f i ca t ion gradients (i.e., r 2 = 0 . 4 8 ) the d e p t h of burial va lue is accurate at best to w i th in ± 1 k m . As a result, the temperature va lue o b t a i n e d f rom Lopat in ' s g e o t h e r m a l gradient wi l l a lso b e s u b j e c t e d t o add i t i ona l error. S e c o n d , the bas ic d i f fe rences in the assumpt ions of Barker's (1983) a n d Lopat in 's (1971) m o d e l s wi l l p r o d u c e o b v i o u s d i sc repanc ies in the r e p o r t e d temperatu res . S A N D S T O N E P E T R O L O G Y A N D D I A G E N E S I S A n examina t ion of textural re lat ionships b e t w e e n auth igen ic phases has b e e n u s e d t o d e t e r m i n e the paragenet ic s e q u e n c e of c e m e n t s and est imate the f lu id chemis t ry in the sands tones of the Eureka S o u n d Fo rmat ion f r o m Strand F io rd . Textura l i n fo rmat ion was o b t a i n e d f r o m b o t h S E M — E D S of g o l d c o a t e d , f ractured s a m p l e s a n d the op t ica l e x a m i n a t i o n of th in sec t i ons . M i n e r a l ident i f icat ion of the coarse r phases was based o n op t ica l examina t ion of th in sec t i ons , S E M — E D S (energy d ispers ive spect romet ry ) e x a m i n a t i o n of c a r b o n c o a t e d p o l i s h e d th in s e c t i o n s and X R D analyses of the < 2 0 Mm f ract ion of the sands tones . R E S U L T S P e t r o l o g y P e t r o l o g y of the Eureka S o u n d Format ion was d e t e r m i n e d f r o m the analysis of 16 th in sect ions of h igh ly c o n s o l i d a t e d , f ine a n d m e d i u m gra ined sandstones . S a n d s t o n e samples f rom the l o w e r 1000 m of s e c t i o n w e r e c o l l e c t e d f r o m major s a n d s t o n e h o r i z o n s w i t h o u t o b s e r v i n g any spec i f ic samp le interval . This samp l i ng p r o c e d u r e was d o n e b e c a u s e of the relative scarcity of sands tones t h r o u g h the l o w e r part of the sec t i on . A b o v e 1000 m, samples w e r e taken at app rox imate l y 80 m intervals o r as e x p o s u r e and d e g r e e of c o n s o l i d a t i o n pe rm i t ted . De ta i l ed sampl ing of i so la ted h o r i z o n s was no t d o n e as the samples u s e d in this s tudy w e r e not c o l l e c t e d speci f ica l ly for this study. M o d a l analysis of f ramework grains was d o n e by p o i n t c o u n t i n g a m i n i m u m of 400 grains per samp le to ensure that a statistically s igni f icant grain p o p u l a t i o n was o b t a i n e d ( S o l o m o n , 1963). C e m e n t and po ros i t y w e r e ca lcu la ted by ident i fy ing 400 gr id po in ts pe r samp le as e i ther f ramework , po re , o r c e m e n t . R o u n d n e s s and spher ic i ty de te rm ina t ions w e r e d o n e by c o m p a r i n g the shapes of 25 grains per samp le w i t h the tables of K r u m b e i n ef al. (1963) and R i t tenhouse (1943). Ave rage grain s izes w e r e d e t e r m i n e d by measur ing the l o n g axis of 25 grains per samp le . Seven o f the m o s t textural ly var ied samples w e r e c h o s e n fo r S E M — E D S analysis w h i l e 6 of the m o r e c o m p o s i t i o n a l l y c o m p l e x samples w e r e c h o s e n fo r X R D w h o l e — r o c k analysis. Th in s e c t i o n analysis of the 16 samples revealed that all of the s t u d i e d rocks are c o m p o s i t i o n a l l y very mature . Fi f teen of the samples are quartz arenites, and o n l y o n e is a quartz w a c k e w i t h app rox imate l y 1 5 % clay in its matrix. Table 2 out l ines the f r a m e w o r k c o m p o s i t i o n of e a c h samp le a long w i t h the n u m b e r of grains c o u n t e d pe r sample . Figure 11 d e m o n s t r a t e s the c o m p o s i t i o n of the rock clan f r o m the Strand Fiord s e c t i o n us ing G i lbe r t ' s (1954) c lass i f icat ion s c h e m e (Wi l l iams et al., 1982). The major i ty of the quartz is monocrys ta l l i ne (77% of f ramework o n average) and po lycrysta l l ine (14% of f ramework o n average) grains. C h e r t , a lso i n c l u d e d w i t h quartz, makes up o n average 5 % of the f r a m e w o r k material . C h e r t grains c o m m o n l y appear a l tered in th in sec t i on . Q u a r t z — q u a r t z grain contacts range f rom f loat ing grains (RAK—40) t o su tu red con tac ts (occur r ing primari ly t h r o u g h the l o w e r 1800 m of the sect ion ) . The bulk of the samples , h o w e v e r , d isplay primari ly c o n c a v o - c o n v e x and l o n g c o n t a c t s ind icat ing m o d e r a t e a m o u n t s of pressure so lu t i on b e t w e e n b o t h quartz o v e r g r o w t h s and detrital quartz grains (Adams, 1964). Textural ly, samples are mature to submatu re as is re f lec ted by grain r o u n d n e s s e s and spher ic i t ies w h i c h range f r o m 0 . 3 - 0 . 6 ( m o d e = 0.5) ( K r u m b e i n ef al., 1963) and 0 . 5 3 - 0 . 9 1 ( m o d e = 0.75) (R i t tenhouse, 1943) , respect ively . Gra in sor t ing is primari ly m o d e r a t e . In genera l , grain spher ic i ty and r o u n d n e s s appears t o i m p r o v e as the sor t ing increases. 37 90-10-0 80-20-0 F e l d s p a r s Q u a r t z + C h e r t 100-0-0 9 0-0-10 80-0-20 R o c k F r a g m e n t s X - Y - Z : % Q u a r t z - % F e l d s p a r - % R o c k f r a g m e n t s | | : E n l a r g e d A r e a F i g u r e 11- R A K - 2 5 rock clan p l o t t e d o n a m o d i f i e d G i lber t ' s (1954) c o m p o s i t i o n triangle. TABLE 2 F ramework P e t r o l o g y of Sandstones Sample M x t l Q P x t l Q Plag Kspar SRF O r g s C h e r t C o u n t s R A K - 7 66 19 Tr 1 9 Tr 4 414 R A K - 1 0 64 32 Tr 1 2 Tr Tr 407 R A K - 1 3 74 12 2 Tr 2 3 6 436 R A K - 1 8 82 16 Tr 0 0 Tr 1 525 R A K - 2 6 90 8 Tr 0 0 1 0 410 R A K - 3 4 A 75 7 1 0 1 9 7 532 R A K - 4 0 90 4 Tr 0 0 3 2 411 R A K - 4 9 88 9 Tr Tr 1 Tr 2 453 R A K - 6 3 88 7 Tr Tr Tr Tr 3 404 R A K - 6 6 72 18 Tr t r . Tr 0 9 413 R A K - 9 0 71 16 Tr Tr Tr 3 10 452 R A K - 9 6 72 14 1 Tr 0 3 10 412 R A K - 9 7 72 14 1 Tr 0 1 3 402 R A K - 1 1 8 88 14 1 Tr 0 Tr 1 422 R A K - 1 2 7 77 20 0 0 Tr 2 Tr 410 M x t l Q (monocrys ta l l i ne quartz) , P x t l Q (polycrystal l ine. quartz) , Plag (albite), Kspar (po tass ium feldspar) , SRF (sed imentary rock f ragments) , O r g s (o rgan ics /phytoc lasts ) Detr ital feldspars const i tu te n o m o r e than 3 % of the total f r a m e w o r k in any of the samples . P lagioclase is 3 t o 4 t imes as abundant as p o t a s s i u m feldspar. Al l p lag ioc lase grains display character ist ic albite tw inn ing . P lag ioc lase c o m p o s i t i o n s w e r e ca lcu la ted us ing the M i c h e l — L e v y m e t h o d (Kerr, 1977). A v e r a g e d ex t inc t ion ang le pairs range in value f r o m 12.5° t o 18° ind icat ing p lag ioc lase c o m p o s i t i o n s b e t w e e n A n 2 and A n , 0 . D e g r a d e d m i c r o c l i n e is the d o m i n a n t p o t a s s i u m feldspar, but never o c c u r s in a m o u n t s e x c e e d i n g 1 % of the tota l detrital f ract ion . A l l fe ldspars appear to b e h ighly d iagenet ica l ly a l tered s h o w i n g e v i d e n c e of kao l in i t i zat ion , m i n o r ser ic i t i zat ion a n d extens ive d i s s o l u t i o n . Phytoc lasts o c c u r as d i s s e m i n a t e d , o p a q u e f ragments in most of the 16 samples . Percentages range f r o m trace a m o u n t s in a f e w samples to as m u c h as 8% in o t h e r samples (i.e., RAK—34A) . Primary poros i ty is absent f r o m sands tones e x a m i n e d in this study. O v e r s i z e d , irregular s e c o n d a r y po res (Shanmugan, 1985) c o m m o n l y assoc ia ted w i th chert and highly a l tered fe ldspars are pervasive t h r o u g h ou t the s e c t i o n . These o v e r s i z e d pores are b e l i e v e d t o fo rm by the d i s s o l u t i o n of a luminos i l icates a n d poss ib l y m i c r o — p o r o u s cher t as is d i s c u s s e d in a later s e c t i o n . M a n y of these o v e r s i z e d pores have b e e n r e d u c e d in s ize by the s u b s e q u e n t g r o w t h of quartz ove rg rowths , kaol in i te and d a w s o n i t e crystal aggregates into the p o r e spaces . A d d i t i o n a l secondary poros i ty is p resent in t h o s e s a n d s t o n e s that c o n t a i n abundant ca rbonate c e m e n t . In these ca lca reous sandstones , the s e c o n d a r y po ros i t y appears in the f o r m of partially d i s s o l v e d carbonates (especia l ly calc i te and ankerite) . Total po ros i t y va lues range f rom virtually 0% in the f iner g ra ined , and m o r e p o o r l y so r ted sandstones (e.g. RAK—7) to as h igh as 2 5 % in the c leaner and bet ter s o r t e d sandstones (e.g. RAK—118) . C e m e n t s and matrix general ly c o n s t i t u t e b e t w e e n 1 % and 2 0 % of the total rock v o l u m e . Usual ly n o m o r e than one—s ix th of this 2 0 % is matrix material s u c h as detr i ta l clays. Table 3 out l ines the d is t r ibut ion of the o b s e r v e d c e m e n t s t h r o u g h the s e c t i o n . T h e f o l l o w i n g s e c t i o n examines the o c c u r r e n c e s and m o r p h o l o g y of the c e m e n t s and auth igen ic minerals in m o r e deta i l . TABLE 3 D is t r ibu t ion of Sands tone C e m e n t s T h r o u g h Sect ion S a m p l e Q O G C a r b o n a t e Pyrite C l a y O t h e r RAK 7 X , —. X •x, F e O , R A K 10 x, — — x, F e O , RAK 13 X(Tr ) , A n k e r i t e , C a l c i t e 1 — Kaol in i te , F e O , RAK 18 x, • — — ' — — R A K 26 x, — • — X(Tr ) , F e O , R A K 3 4 A — A n k e r i t e , 2 3 X X(Tr ) , F e O , C a l c i t e , 2 3 RAK 40 — • C a l c i t e , 2 3 X X(Tr ) , - F e O A n k e r i t e , 2 3 R u t i l e , RAK 49 x r C a l c i t e , 2 3 — X(Tr ) , — A n k e r i t e , 2 3 RAK 63 X i — — — — RAK 66 X i — — — — . R A K 90 C a l c i t e 1 2 3 — Kaol in i te 2 3 F e O , D a w s o n i t e , 3 Sider i te (Tr ) , 2 3 A n k e r i t e ( T r ) , 2 3 RAK 96 X (Tr ) , C a l c i t e ^ 2 3 X Kaol in i te 2 3 — Anker i te , 2 3 l l l ite 3 D a w s o n i t e , 2 3 Sider i te 2 RAK 97 C a l c i t e 2 — Kaol in i te 2 3 A n a l c i m e O D a w s o n i t e , 3 l l l ite 3 Rutile 3 S i d e r i t e , 2 RAK 118 X(Tr ) , C a l c i t e , 2 3 X — — D a w s o n i t e , 2 3 A n k e r i t e , 2 3 R A K 127 x / D a w s o n i t e , — — — R A K 129 x, Fe—Calc i te , 2 — — Sider i te 2 1 = D e t e r m i n e d Opt ica l l y ; 2 = D e t e r m i n e d us ing X R D ; 3 = D e t e r m i n e d us ing S E M — E D S ; T r = T r a c e ; X = present ; — = a b s e n t D i s c r i p t i o n of A u t h i g e n i c M i n e r a l s A total of 13 auth igen ic phases w e r e o b s e r v e d in the Eureka S o u n d sandstones . O f the 13, on ly 6 w e r e p resent in p r o p o r t i o n s great e n o u g h to classify t h e m as pr inc ipa l auth igen ic minerals . The remain ing 7 au th igen ic minerals are c lass i f ied , f o r the p u r p o s e s of this paper, as accessory—auth igen ic minerals . Four of the 6 pr inc ipa l auth igen ic minerals are carbonates ; ca lc i te , anker i te , s ider i te , and d a w s o n i t e . The remain ing 2 p r inc ipa l au th igen ic phases cons is t o f kao l in i te , and quar tz ove rg rowths . The accesso ry—auth igen ic minerals o c c u r r i n g t h r o u g h the s e c t i o n are i l l i te, pyr ite, i ron o x i d e , ruti le, s p h e n e , analcime(?) and chabazite(?) . In genera l , a c c e s s o r y - ^ u t h i g e n i c minerals make up a less than 1 % of the tota l a m o u n t of c e m e n t . Pr incipal A u t h i g e n i c Minera ls Calcite C a C 0 3 — C a l c i t e o c c u r s primari ly as a v o i d a n d fracture f i l l ing c e m e n t t h r o u g h m o s t of the s e c t i o n . It was ident i f ied opt ica l l y by its e x t r e m e l y h igh b i re f r ingence (0.172) and character ist ic {0112} t w i n n i n g . S E M — E D S analyses revealed that m i n o r a m o u n t s of Fe are subst i tu ted for C a . W e l l d e v e l o p e d subhedra l crystals of ca lc i te w e r e a lso v is ib le in the po res of a n u m b e r of samples . C a l c i t e c e m e n t never e x c e e d s 1 0 % of the total c e m e n t . Ankerite C a ( M g , F e ) ( C O 3 ) 2 — Anker i te is the d o m i n a n t c e m e n t in a n u m b e r of samp les . For examp le , in RAK—13 ankerite c o m p r i s e s up to 9 0 % of the total c e m e n t . Like ca lc i te , ankerite o c c u r s as fracture and v o i d inf i l l ings. A n k e r i t e is d i s t i n g u i s h e d f r o m calcite by having genera l ly h igher b i re f r ingence and b r o w n i s h stains a r o u n d its cyrstal b o u n d a r i e s and w i th in the crystals as s e e n u n d e r p lane po la r i zed l ight. Fur thermore , w h e n v i e w e d in th in s e c t i o n ankerite crystals are general ly m o r e c o r r o d e d a n d anhedra l than assoc ia ted calcite crystals. S E M — E D S analyses s h o w ankerite t o be M g free o r p o o r and thus ext reme ly Fe r ich (Figure 12). A n k e r i t e ' s . c o m p o s i t i o n genera l ly p lo ts near the C a — F e m i d po in t o n the C a — F e — M g c a r b o n a t e ternary d iagram (Figure 13). Siderite F e C 0 3 — Discre te s ider i te was n o t r e c o g n i z e d opt ica l ly in thin sec t ions . S ider i te ident i f icat ion was b a s e d o n S E M - C D S analyses of p o l i s h e d thin sec t ions a n d X R D analyses. S ider i te displays character ist ic d i f f ract ion peaks at 0.279 and 0.173 nm a n d p r o d u c e s an EDS pattern as s e e n in f igure (14a). Like anker i te , s ider i te appears t o be m o r e anhedra l than assoc ia ted calc i te and o c c u r s in p r o p o r t i o n s less than 8% of the tota l c e m e n t . S ider i te o c c u r s as a pr imary p o r e f i l l ing c e m e n t (Plate 1a). Dawsonite N a A l C 0 3 ( O H ) 2 — D a w s o n i t e was initially di f f icult t o pos i t i ve ly ident i fy in part d u e to the relative lack of r e p o r t e d o c c u r r e n c e s in o t h e r s tudy areas. T h e best k n o w n and m o s t s t u d i e d o c c u r r e n c e of d a w s o n i t e is f r o m the G r e e n River Format ion o i l shales of C o l o r a d o w h e r e it occu rs w i th o the r lacustr ine saline ca rbonates such as nahco i i te ( M e d d a u g h and Salott i , 1983; Smi th and Y o u n g , 1975). O t h e r o c c u r r e n c e s of d a w s o n i t e appear in w e a t h e r e d syenite tuffs in O l d u v a i G o r g e , Tangany ika (Hay, 1963) and in rhyol i t ic ign imbr i tes near Ter lano, Italy ( C o r a z z a ef al., 1977). T h r o u g h the u p p e r third of the s e c t i o n d a w s o n i t e is the m o s t abundant s a n d s t o n e c e m e n t ; it c o m p r i s e s approx imate ly 1 0 0 % of the c e m e n t in samp le RAK—127 . D a w s o n i t e was on ly o b s e r v e d in the z o n e 5 and over ly ing sandstones . The vert ical d is t r ibut ion of d a w s o n i t e a n d anker i te appears t o be inversely re lated. In ~ 2 H o O O c 3 O O i H C a Mg p o o r / f r e e A n k e r i t e F e i i p 4 6 K e V —r 1 o Figure 12a- Energy d ispers ive s p e c t r o g r a p h of M g p o o r / v o i d anker i te . O O 4 ^ 3H X w 2 H co c 3 O O 1 H Mg p o o r C a A n k e r i t e F e 1 — 1 — i — i i i — i i 4 6 8 10 K e V Figure 12b- Energy d ispers ive s p e c t r o g r a p h of M g p o o r ankerite. 44 C a O - M g O - F e O - C 0 2 • Ankerite composit ion from this study Figure 13- A p p r o x i m a t e anker i te c o m p o s i t i o n range p l o t t e d o n a C a O - F e O - M g O - C 0 2 ternary d iagram. C o m p o s i t i o n s are on ly app rox imat ions as d e t e r m i n e d by EDS analyses. g e n e r a l / the d a w s o n i t e c o n t e n t per samp le increases f r o m the base of z o n e 5 t o w a r d the t o p of the s e c t i o n w h i l e the anker i te c o n t e n t c o r r e s p o n d i n g l y decreases o v e r the same range (Figure 15). The s ign i f icance of this t rend is b e l i e v e d to be re la ted t o the p rox im i ty of the diapirs as is d i s c u s s e d in a later s e c t i o n . U n d e r the opt ica l m i c r o s c o p e d a w s o n i t e is r e c o g n i z e d in p lane p o l a r i z e d l ight (ppl) as clear, c o l o r l e s s aggregates of radiat ing, acicular crystals. Its b i re f r i ngence is l o w e r than that of ca lc i te 's (0.172) but c o n s i d e r a b l y h igher than that o f kaol in i tes . S E M — E D S analyses are by far the m o s t usefu l t e c h n i q u e for ident i fy ing dawson i te . Figure (14b) s h o w s a typ ical EDS pattern for d a w s o n i t e , s h o w i n g rough ly equa l p r o p o r t i o n s of N a and A l . Plate 1b is a typical back scat tered image of d a w s o n i t e a n d quartz reveal ing the d i f fe rence in average a t o m i c n u m b e r of the t w o minerals . D a w s o n i t e ' s crystal and aggregate m o r p h o l o g y is s h o w n in Plate 2c, w h e r e it is s e e n o c c u p y i n g a p o r e throat. C o n f i r m a t i o n of d a w s o n i t e was m a d e us ing the X R D w h e r e character ist ic d i f f ract ion peaks o c c u r at 0 .570 and 0 .3385 n m . D a w s o n i t e is occas iona l l y o b s e r v e d w i th an ' i l l i t ic ' i n te rg rowth (plate 2d) w h o s e c h e m i c a l s ign i f icance is no t w h o l l y u n d e r s t o o d at this t ime. Quartz S i 0 2 — Syntaxial quartz o v e r g r o w t h s are m o s t c o m m o n in the m e d i u m g ra ined samp les w h i c h had e i ther relatively h igh pr imary p o r o s i t y o r o v e r s i z e d s e c o n d a r y poros i ty . Samples w i th greater amounts of clay in the matrix general ly had f e w e r and smal ler o v e r g r o w t h s than the c leaner arenites. The average th ickness of the quar tz o v e r g r o w t h s is approx imate ly 3—5 urn and the o v e r g r o w t h s can be f o u n d o n app rox imate l y 3 5 % of all detr ital quartz grains. O v e r g r o w t h s c o m p r i s e up to 1 0 0 % of the total c e m e n t in samples RAK—18 and 26. Ev idence fo r add i t iona l quartz c e m e n t is man i fes ted as e i ther o r b o t h c o n c a v o - c o n v e x and su tu red grain c o n t a c t s in m o s t samples . 2 ^ o o o CO c 3 o O F e S i d e r i t e Mn (A. 4 6 K e V 8 1 0 Figure 14b- Energy d ispers ive s p e c t r o g r a p h of s ider i te . 8 -O 7 -o o 8 " 5 -X w 4 -(0 3 -•*— C 2 -=> O 1 " o o-: A l N a D a w s o n i t e i 1 - i r 1 2 3 4 -I 5 K e V Figure 14a- Energy d ispers ive s p e c t r o g r a p h of d a w s o n i t e s h o w i n g equal p ropo r t i ons of N a and A l . 47 O O *- 0 2 0 4 0 6 0 8 0 1 0 0 P e r c e n t a g e of t o t a l c e m e n t Figure 15- Var iat ions in anker i te and dawson i te p r o p o r t i o n s wi th d e p t h . PLATE 1 Morphology, Textural Relationships, and Back Scattered Ellectron Image Appearence of Dawsonite and Associated Minerals A. Scanning electron micrograph of siderite (Sd) and quartz (Qu). Siderite occurs as a primary pore filling cement; polished thin section; back scattered electron image; RAK—97—25. B. Scanning electron micrograph of dawsonite (Dw), quartz (Qu), calcite (Cc) and plagioclase (Pg). Grey shade difference reflects the difference in average atomic number between these minerals; polished thin section; back scattered electron image; RAK—96—25. C. Scanning electron micrograph of acicular dawsonite (Dw) occupying a pore; calcite (Cc) occurs adjacent to an oversized pore; Dawsonite is associated with quartz (Qu) and potassium feldspar (Ks); secondary electron image; polished thin section; RAK—118—25. D. Scanning electron micrograph of dawsonite (Dw) intergrown with illite. Dawsonite (Dw) can also be seen replacing calcite (Cc) (see arrow); back scattered electron image; polished thin section; RAK—96—25. Kaolinite A l 2 S i 2 O s ( O H ) f l — Kaol in i te b o o k l e t s are v is ib le in many of the samples as revea led by S E M analysis. The b o o k l e t s c o m m o n l y o c c u r as p o r e f i l l ings (Plate 2a) a n d , in a n u m b e r of instances , are c lose ly assoc ia ted w i t h r e s o r b e d K—spar and N a — p l a g i o c l a s e . O p t i c a l ident i f icat ion of kaol in i te was b a s e d o n its v e r m i f o r m habit a n d very l o w b i re f r ingence (Plate 2b). Individual kao l in i te crystals range in s ize f r o m 3 to 4 Mm. A c c e s s o r y — a u t h i g e n i c Minera ls lllite— Like kaol in i te , illite is a late stage d iagenet ic mineral as revea led by its o c c u r r e n c e in po res and as s p o r a d i c grain coat ings . Individual illite crystals occas iona l l y o c c u r as grain dust ings . As was m e n t i o n e d prev ious ly , illite(?) also occas iona l l y o c c u r s as an inter g r o w t h w i t h d a w s o n i t e . Pyrite F e S 2 ^ Pyrite o c c u r s in o n l y a f e w samples t h r o u g h the s e c t i o n . Euhedral pyr i te crystals w e r e o b s e r v e d b o t h w i t h the b i n o c u l a r m i c r o s c o p e and in th in s e c t i o n . The crystals are general ly very smal l , rang ing in size f r o m 3 to 11 Mm. In p lane po la r i zed light the pyrite crystals appear sl ightly t ranslucent (Plate 3a). Iron Oxides/hydroxides F e O x — Redd ish b r o w n i ron o x i d e s / h y d r o x i d e s are r e c o g n i z e d in a n u m b e r of thin sec t ions u n d e r p lane p o l a r i z e d l ight. In m o s t cases it is c l o s e l y assoc ia ted w i t h anker i te . Rutile/Anatase(?)/Brookite(?) T i 0 2 — Rutile o c c u r s as smal l euhedra l crystals in assoc ia t ion w i t h ca lc i te and less c o m m o n l y w i th ankerite. Ident i f icat ion of rutile was based so le ly o n S E M — E D S analysis of p o l i s h e d thin sec t ions (Plate 3b). PLATE 2 M o r p h o l o g y and A p p e a r e n c e of Kaol in i te Scann ing e l e c t r o n m i c r o g r a p h of kaol in i te (Ka) l in ing p o r e s ; s e c o n d a r y e l e c t r o n image ; f ractured samp le ; g o l d c o a t e d image ; RAK—96—25. M i c r o g r a p h of auth igen ic vermicu lar kao l in i te (Ka) o c c l u d i n g a p o r e s p a c e ; assoc ia ted w i t h quartz (Qu) ; p lane p o l a r i z e d l ight; RAK—96—25. 53 PLATE 3 M o r p h o l o g y a n d O c c u r e n c e of Pyrite and Rutile A . C u b i c pyrite assoc ia ted w i t h d a w s o n i t e (Dw) and quar tz ( Q u ) as seen in p lane po la r i zed l ight; h o r i z o n t a l f ie ld = 0.19 m m ; R A K - 1 1 8 - 2 5 . B. S c a n n i n g e l e c t r o n m i c r o g r a p h of ruti le (Ru) assoc ia ted w i t h anker i te (Ak); p o l i s h e d th in s e c t i o n ; b a c k scat te red e l e c t r o n image ; RAK—96—25. 5V Analcime N a A l S i 2 O s ' 2 H 2 0 — Analcime has previously been reported in the study area by Bustin (1977). In the present study, however, the occurrence of analcime is uncertain as it was identified in only one sample based on an EDS pattern analysis from a single grain. Never was analcime observed in thin section or in SEM fracture samples. XRD analysis also failed to indicate the presence of analcime in any of the samples. Certainly, if analcime is present it only exists in extreme trace amounts. D I S C U S S I O N T e x t u r a l R e l a t i o n s h i p s Textural relationships between authigenic minerals, where present, are outlined below. Unfortunately, not all authigenic minerals display textural associations with all other authigenic phases and, therefore, some ambiguities exist in the paragenetic sequence. A number of relationships are, however, revealed by cement associations with quartz overgrowths. Syntaxial quartz overgrowths coated with kaolinite booklets or dawsonite crystals commonly project into pore spaces (Plate 4a, b) suggesting that quartz overgrowth formation pre-dated both kaolinite and dawsonite genesis. Quartz overgrowths are also seen projecting into the oversized pores created by the dissolution of feldspars and chert grains. Veneers of illite occur as coverings on quartz overgrowths. Strong evidence for calcite cementation post—dating quartz overgrowth formation can be seen in plate 5a,b, which shows calcite cement replacing a quartz overgrowth and its nucleus. Note that the clay dust rim between the overgrowth and the nucleus has not been replaced by the calcite. Both embayed contacts and quartz 'islets' within calcite and ankerite are extremely PLATE 4 Morphology and Textural Relationships Between Dawsonite and Quartz Overgrowths A. Scanning electron micrograph of dawsonite (Dw) post—dating quartz overgrowth formation. Note acicular and radiating habit of dawsonite; fractured sample; gold coated; secondary electron image;RAK—96—25. B. Thin section micrograph under crossed nicols showing same relationship as in plate 6a; dawsonite (Dw), quartz overgrowth; crossed nicols; horizontal field = 0.77 mm; RAK-90-25. c o m m o n . T h e relative t im ing o f f o r m a t i o n of s ider i te and ankerite is uncerta in due t o i n c o n c l u s i v e textural re lat ionsh ips . A n k e r i t e , h o w e v e r , m o s t l ikely f o r m e d after the f o r m a t i o n of quartz o v e r g r o w t h s as it rep laces calc i te crystals w i th in o v e r g r o w t h s (Plate 6a, b). It is there fore c o n c l u d e d that at least t w o stages of quartz o v e r g r o w t h f o r m a t i o n ex is ted d u r i n g the e v o l u t i o n of the s t u d i e d strata, early in the pa ragene t ic s e q u e n c e pr ior t o t h e p rec ip i ta t ion of calc i te and after the d i sso lu t i on o f the f r a m e w o r k a luminos i l icates but p r io r t o the p rec ip i ta t ion of kaol in i te and d a w s o n i t e . A d d i t i o n a l textural i n fo rmat ion is d rawn f r o m e x a m i n i n g the re lat ionships b e t w e e n the carbonates and the o the r d iagenet ic phases. Euhedral ca lc i te and F e O ^ w e r e c o m m o n l y o b s e r v e d in assoc ia t i on w i th anhedra l ankerite. A l t h o u g h no t c o n c l u s i v e , this re lat ionship suggests that a later stage calc i te a n d FeC»x are p r o d u c t s in an anker i te d i sso lu t i on react ion . Plates 7a & b s h o w s r e s o r b e d ca lc i te e n c a s e d in d a w s o n i t e crystals suggest ing that the t w o are e i ther c o n t e m p o r a n e o u s or, m o r e p robab ly , that the calc i te pre—dates the d a w s o n i t e . Kaol in i te b o o k l e t s w e r e also o c c a s i o n a l l y o b s e r v e d o n euhedra l ca lc i te crystals w i t h i n p o r e spaces . This e v i d e n c e suppo r ts the theory that calc i te p redates the kaol in i te . Anker i te p rec ip i ta t ion / fo rmat ion o c c u r r e d b e f o r e the d i s s o l u t i o n of the f ramework a luminos i l icates as anker i te c e m e n t b o u n d a r i e s are c o i n c i d e n t w i th " g h o s t " a luminos i l icate grain a n d o v e r s i z e d p o r e b o u n d a r i e s . Plate 8a demonst ra tes the re la t ionsh ip b e t w e e n illite and d a w s o n i t e . D a w s o n i t e can be s e e n b o t h w i t h an i l l it ic c o v e r i n g and as an in te rg rowth w i th illite(?). Kao l in i te b o o k l e t s and d a w s o n i t e can b e seen in Plate 8b. The o b s e r v e d re lat ionship b e t w e e n kaol in i te and d a w s o n i t e suggests that d a w s o n i t e and kaol in i te are e i ther syntaxial o r t h e kaol in i te pre—dates the d a w s o n i t e . Figure 16 ou t l i nes a paragent ic ( 59 PLATE 5 Textura l Relat ionships B e t w e e n Anker i te and Q u a r t z O v e r g r o w t h s A. M i c r o g r a p h of anker i te (Ak) r e p l a c i n g quar tz o v e r g r o w t h and the quartz n u c l e u s (Qu) . N o t i c e that the o v e r g r o w t h 'dust r im' (see arrow) is p rese rved in the c a r b o n a t e ; c r o s s e d n ico ls ; ho r i zonta l f ie ld = 0.77 m m ; R A K - 4 9 - 2 5 . B. En la rgement of p late 5a; ho r i zonta l f ie ld = 0.19 m m . 61 PLATE 6 Textural Relationships Between Calcite, Ankerite, and Quartz Overgrowths Ankerite (Ak) altering to Calcite (Cc) euhedra within a quartz overgrowth; crossed nicols; horizontal field = 0.58 mm; RAK—49—25. Enlargement of plate 13a; horizontal field = 0.19 mm. (2 PLATE 7 Textural Relat ionship B e t w e e n D a w s o n i t e and O t h e r C a r b o n a t e s Scann ing e lec t ron m i c r o g r a p h of d a w s o n i t e (Dw) s u r r o u n d i n g a c o r r o d e d ankerite (Ak) crystal . Textura l re lat ionship suggests that the anker i te predates the d a w s o n i t e ; g o l d c o a t e d f ractured samp le ; s e c o n d a r y e l e c t r o n image ; R A K - 9 6 - 2 5 . Th in s e c t i o n m i c r o g r a p h similar t o plate 14a s h o w i n g d a w s o n i t e (Dw) rep lac ing a calc i te ( C c ) crystal ; c r o s s e d n ico l s ; ho r i zonta l f ie ld = 0.85 m m ; RAK-96-25. PLATE 8 Textural Relationships Between Dawsonite and Other Silicates Scanning electron micrograph displaying textural relationship between kaolinite (Ka) and dawsonite (Dw). Relationship suggests that kaolinite is either pre— or syn—genetic with dawsonite; gold coated fractured sample-secondary electron image; RAK—96—25. Scanning electron micrograph of dawsonite (Dw) replacing both calcite (Cc) and plagioclase (Pg) and occurring with illite(?) (arrow), polished thin section; back scattered electron image; RAK—96—25. s e q u e n c e b a s e d o n in fo rmat ion d e r i v e d f r o m total c o m b i n e d textural in fo rmat ion . Fluid Chemistry C h e m i c a l cons ide ra t i ons o f the o b s e r v e d auth igen ic mineral assemblage suggest that n u m e r o u s e p i s o d e s of c h a n g i n g p o r e f lu id chemist ry have ex is ted in the Eureka S o u n d strata s i nce the t ime of their d e p o s i t i o n . The p r e s e n c e of s ider i te and pyrite, f o r e x a m p l e , suggests a p e r i o d w h e n Eh was l o w (i.e., < 0 . 3 5 v (Curt is and Spears, 1968)) and F e 2 * activity relatively h igh . In o rde r to facil itate the f o r m a t i o n of b o t h pyrite and sider i te , h o w e v e r , sul f ide activity had to vary w i th t ime and /o r d e p t h . For examp le , pyrite is r e p o r t e d t o f o r m under c o n d i t i o n s of non—res t r i c ted water c i rcu la t ion a n d e levated sulfur activity (Curt is and Spears, 1968) w h i l e s ider i te f o r m a t i o n is favored by c o n d i t i o n s of restr icted water c i rcu la t ion , e levated F e 2 * : C a 2 * , and very l o w sul f ide activity ( M a t s u m o t o ef al., 1981). Pyrite is, the re fo re , s u g g e s t e d t o b e an earl ier phase than sider i te, a l t h o u g h textural i n fo rmat ion in s u p p o r t of this is i n c o n c l u s i v e . It is be l i eved that the anaerob ic r e d u c t i o n of sulfate, in the p r e s e n c e of e x c e s s F e 2 + , near the s e d i m e n t / w a t e r interface c reated c o n d i t i o n s favorable for pyrite fo rmat ion . Pyrite fo rmat ion is be l i eved to give w a y to s ider i te f o r m a t i o n w i t h increas ing d e p t h as C 0 2 activity increases and sul f ide activity decreases . C h a n g e s in b o t h the C 0 2 and sul f ide activit ies are b e l i e v e d to be mainly c o n t r o l l e d by the b i o c h e m i c a l degradat ion of o rgan ic matter d u r i n g , early d iagenes is . Initial quartz o v e r g r o w t h p rec ip i ta t ion is t h o u g h t to have o c c u r r e d at relatively sha l low d e p t h s early in the paragenet ic s e q u e n c e w h e n si l ica so lub i l i ty is general ly low. A t the l o w temperatures of s h a l l o w burial the solubi l i ty of quar tz is approx imate l y 6 m g I" 1 , s igni f icant ly l o w e r than the a m o u n t of s i l ica p resent in P a r a g e n e t i c S e q u e n c e Q u a r t z O v e r g r o w t h C a l c i t e mm S i d e r i t e _ ? A n k e r i t e P y r i t e • F e l d s p a r D i s s o l u t i o n -. D a w s o n i t e K a o l i n i t e Figure 16- Diagram of paragenetic sequence near sur face and fluvial waters . U n d e r these sha l l ow burial c o n d i t i o n s w h e r e si l ica so lub i l i ty is l o w quartz wi l l genera l ly p rec ip i ta te in quant it ies p r o p o r t i o n a l t o the v o l u m e of f lu id m o v e d t h r o u g h the rock . W i t h increas ing d e p t h and temperature , h o w e v e r , m o r e s i l ica is requ i red to be in s o l u t i o n to prec ip i ta te quartz as the so lub i l i ty of quartz increases by an o r d e r of magn i tude f r o m 6 m g I" 1 at 20 °C to 63 m g I " 1 at 100°C (Ehlers and Blatt, 1980 (original s o u r c e n o t referenced) ) . The first e p i s o d e of quartz o v e r g r o w t h p rec ip i ta t i on is, there fore , b e l i e v e d t o have o c c u r r e d du r ing sha l l ow burial w h e n temperatu res w e r e < 2 0 ° C a n d near surface water c i rcu la t ion relatively unrest r ic ted . A l t h o u g h the si l ica necessary to prec ip i ta te the early quar tz o v e r g r o w t h s is be l i eved t o have b e e n de r i ved f r o m external f luids, later stage o v e r g r o w t h s are t h o u g h t t o have prec ip i ta ted f r o m loca l ly d e r i v e d si l ica w h i c h may have b e e n p r o d u c e d by a c o m b i n a t i o n of s o u r c e s i n c l u d i n g : 1) the d i s s o l u t i o n o f f ramework a luminos i l icates and m i c r o — p o r o u s chert ; 2) s i l ica re leased dur ing c o m p a c t i o n as a result of pressure s o l u t i o n ; 3) s i l ica re leased dur ing the i l l i t izat ion o f smect i te in adjacent shales. The d i s s o l u t i o n of the f r a m e w o r k a luminos i l icates , p rec ip i ta t ion of kaol in i te arid d a w s o n i t e a n d the p r e s e n c e of calc i te may be e x p l a i n e d by c o n s i d e r i n g the effects of o rgan ic d iagenesis o n ino rgan ic d iagenes is . The thermal maturat ion of o rgan ic matter is n o w c o m m o n l y a c c e p t e d t o result in the c leav ing of funct iona l g r o u p s f r o m p h e n o l s , vo lat i les , c a r b o x y l i c acids , and short c h a i n e d al iphatics f r o m the larger aromat ic , al iphatic and al icycl ic parent m o l e c u l e s . In rocks w h e r e there are large a m o u n t s o f c o a l and d i s s e m i n a t e d organ ics , such as t h o s e wi th in the Eureka S o u n d Fo rmat ion , carboxy l ic ac id c o n c e n t r a t i o n s can be e x c e e d i n g l y h igh . For e x a m p l e , Ca ro the rs and Kharaka (1978) d e m o n s t r a t e d that ca rboxy l i c ac id c o n c e n t r a t i o n s can e x c e e d 5000 m g I" 1 in s o m e o i l f ie ld f o rmat ion waters . C a r b o x y l i c acids , w h e n in the p r e s e n c e of A l 3 *, are k n o w n to b o n d w i t h the A l 3 * t o f o r m wate r s o l u b l e c o m p l e x e s . The mob i l i t y o f A l 3 + in s o l u t i o n is e n h a n c e d by an o r d e r of m a g n i t u d e w h e n c o m p l e x e d w i t h acet ic ac id and by 3 o rders of m a g n i t u d e w h e n c o m p l e x e d w i t h oxa l ic ac id (Surdam et al., 1984). The net ef fect of increas ing the mob i l i t y of A l 3 * in s o l u t i o n is t o e n h a n c e the remova l of a q u e o u s A l 3 * f r o m the system and , thereby , destab i l i ze the a luminos i l icates t o a po in t w h e r e they b e g i n t o d isso lve . A s these A l 3 + — c o m p l e x e d f luids migrate t h r o u g h the r o c k they eventual ly e n c o u n t e r z o n e s w h e r e t h e A l 3 * c o m p l e x is b e l i e v e d t o destab i l i ze (poss ib ly d u e to changes in s o l u t i o n p H (Surdam et al., 1984) and result in the p rec ip i ta t ion of kaol in i te and p o s s i b l y d a w s o n i t e (see f o l l o w i n g s e c t i o n o n Dawsonite: chemical constraints). Surdam ef al. (1984) have also d e m o n s t r a t e d that the p r e s e n c e of o rgan ic acids in s o l u t i o n has a p r o f o u n d ef fect o n the carbonate chemist ry . W h i l e the p r e s e n c e of ca rboxy l i c ac ids tends to destab i l i ze a luminos i l icates the same acids can decrease the so lub i l i ty of ca lc i te w i t h increas ing P by buf fe r ing the p H . ln the C O 2 a b s e n c e of ca rboxy l ic acids the reverse is true: calcite so lub i l i ty increases wi th increas ing P^Q ( H o l l a n d and Borcsik , 1976). The p r e s e n c e of d i sso lu t i on features in t h e a luminos i l icates and p r e s e n c e o f p re—a luminos i l i ca te—d isso lu t i on carbonates (ankerite and Fe—calcite) in the Eureka S o u n d sands tones suggests that the P C O 2 w a s relat ively h igh (Surdam ef al., 1984) and that ca rboxy l i c ac ids w e r e buf fer ing c a r b o n a t e p rec ip i ta t ion and des t roy ing a luminos i l icates . The i ron necessary for the f o r m a t i o n of anker i te may have a n u m b e r of sources : Fe re leased du r ing the t rans format ion o f smect i te t o illite, the d i s s o l u t i o n of s ider i te , the r e d u c t i o n of. c o l l o i d a l i ron o x i d e s , and the d i s s o l u t i o n of b io t i te and a m p h i b o l e . F o l l o w i n g the d i s s o l u t i o n of the a luminos i l icates it is be l i eved that e n o u g h organica l ly c o m p l e x e d A l 3 * rema ined in the system to favor the p rec ip i ta t ion of pos t—a luminos i l i ca te—d isso lu t i on kaol in i te and dawson i te . D a w s o n i t e : C h e m i c a l Const ra in ts T h e t h e r m o c h e m i c a l data necessary t o ca lcu late the stabil ity o f d a w s o n i t e are d r a w n f r o m a n u m b e r of sources . First, the heat capac i ty (Cp ) data u s e d t o der ive coe f f ic ien ts for the Ma ie r—Ke l l y heat capac i ty f u n c t i o n : C p = a + b T + c / T 2 w e r e taken f r o m Ferrante ef al. (1976). Figure 17 s h o w s the heat capaci ty f unc t ion fit t o Ferrante ef al's data. The mo la r v o l u m e of d a w s o n i t e was ca lcu la ted us ing the crysta l lographic data of C o r a z z a ef al. (1977). The standard state (298.15°K, 0.1 M P a ) entha lpy of fo rmat ion (H° ) a n d e n t r o p y (S°). w e r e taken f r o m Rob ie ef al. (1978). Free energ ies of fo rmat ion ( C ° ) for the add i t iona l s o d i u m ca rbonate phases c o n s i d e r e d in the partial pressure and activity—activity d iagrams w e r e c o l l e c t e d f rom Carre ls a n d Chr ist (1965). T h e r m o c h e m i c a l data for all rema in ing phases w e r e d rawn f r o m H e l g e s o n (1969; 1978). Be fo re the H ° of d a w s o n i t e c o u l d be u s e d w i t h the H e l g e s o n data set it had to be ad justed in o rde r to p rov ide c o n s i s t e n c y w i t h the o t h e r phases in the data set. H e l g e s o n a d o p t e d a value for the H ° of c o r u m d u m of - 1661655 .0 jnsupminus, Sup1, . in contrast t o the ca lor imetr ica l ly d e r i v e d value of - 1675700 .0 j n " 1 (Robie ef al., 1978). In o rde r to p r o v i d e fo r internal c o n s i s t e n c y , the d a w s o n i t e H ° was ad justed by this d i f fe rence . Tab le 4 presents the t h e r m o c h e m i c a l data for d a w s o n i t e u s e d in the f o l l o w i n g d is t r ibut ion of spec ies 72 O o CM o CO o o CO • 3 o >» o aci N . -a ca O ca o <D CO -I o Data of Ferrante et al. (1976) o T ^"298 320 3 4 0 3 6 0 3 8 0 4 0 0 4 2 0 4 4 0 4 6 0 4 8 0 T e m p e r a t u r e ( K e l v i n ) Figure 17- D a w s o n i t e heat capaci ty funct ion fit t o the data of Ferrante et al. (1976). calcu lat ions . The stabil ity of d a w s o n i t e relative t o o t h e r s o d i u m carbonates was e x a m i n e d in a series o f activity—activity and partial pressure d iagrams pr ior t o p e r f o r m i n g the d i s t r ibu t ion o f s p e c i e s ca lcu lat ions . D u e to the a b s e n c e of heat capac i ty coe f f ic ien ts for the s o d i u m ca rbonates c o n s i d e r e d these stabi l i ty analyses are l im i ted to 298.15°K and 0.1 M P a (Table 5). Ba lanced react ions , l o g K values a n d t h e f ree energ ies of the var ious react ions r e p r e s e n t e d in Figures 18, 19 a n d 20 are l isted in Tables 6 and 7. F igures 18 t h r o u g h 20 d e m o n s t r a t e the c o n t r o l that var iat ions in A l 3 + / H + ratios, P c q , N a * / H + ratios, and activity of wate r have o n the t o p o l o g y of the d a w s o n i t e stabil ity f ie ld . Figures 18 t h r o u g h 20 may, in fact, suggest that d a w s o n i t e is m o r e c o m m o n u n d e r l o w temperature g e o l o g i c P , a , , ~ , a . , 3 + , a . . + CO 2 ri2vJ Al N a c o n d i t i o n s than prev ious ly rea l i zed (see f o l l o w i n g s e c t i o n re: d i s t r i bu t ion of spec ies ) . For e x a m p l e , a recent pe rsona l c o m m u n i c a t i o n (B. Rottenfuser) has s h o w n that p rev ious ly u n d e t e c t e d d a w s o n i t e has b e e n ident i f i ed in the samples o f the G e t h i n g Fo rmat ion of the Peace River O i l Sands. O t h e r factors , h o w e v e r , s u c h as the a u c n u n d o u b t e d l y have s o m e con t ro l l i ng e f fect o n the d is t r ibut ion of d a w s o n i t e , but this has not b e e n p u r s u e d in this study. Stabil ity c o n d i t i o n s of d a w s o n i t e are, h o w e v e r , s t rong ly i n f l u e n c e d by p H a n d the activity o f A l 3 *. Figure 19 t o 21 d e m o n s t r a t e that an increase in 1 l o g a ^ + unit reults in a s igni f icant increase in t h e size of the d a w s o n i t e f ie ld w i th respect t o P and a u „ . The chemis t ry of sea c o 2 r i 2 ( J wate r a n d the f lu id chemis t ry of a n u m b e r of f o r m a t i o n waters are p l o t t e d o n f igures 18, 19 a n d 20 t o i l lustrate the c h e m i c a l d o m a i n of a f e w natural systems w i th in P — a . , a . , 3 + — a . . + — H * space . c o 2 H 2 0 A l J N a r The reason fo r p e r f o r m i n g a d is t r ibut ion of spec ies o n the auth igen ic a s s e m b l a g e was to a p p r o x i m a t e the activities of a q u e o u s s p e c i e s a n d gases in o q o o • «vi CO • *" Z| I o) 2 O r-o 6 — : — : ••'/ / / N a 2 c o 3 / / / / . —-// // Thermonatrite // / / . _ _ _ y 7 / I / / •I / / N a X O . 7H-0 / // ' - . / / . - J i t * ! ™ 7 ' Dawsonite Trona o o> o q Nahcolite 0.0 I 1.0 — I — 2.0 —r— 3.0 a H 2 0 * 1 4.0 -r 5.0 — p — 6.0 SL 1 - i " 7.0 8.0 9.0 10.0 Log »|l8* a H + Figure 18- Plot of L o g ( A N A + / A [ H • ] versus L o g [ A A | • 3 / A 3 H • ]. 1 = Shannon Sandstone, 2 = Ocean water, Star=Eureka Sound Formation. 75 Figure 19- Plot of L o g [ A A | • 3 / A 3 ^ + ] versus LogPco2- 1= S h a n n o n and Bla i rmore S a n d s t o n e s , 2 = O c e a n water , S ta r= Eureka S o u n d Fo rmat ion . Nahcolite o Dawsonite j X — v. V. N s V Trona s N a 2 C 0 3 N ^ ! ' \ 1 i / i o OJ Z N . <?' o CO z -2.20 -1.76 -1.32 -0.88 -0.44 0.00 Log a H 2 Q F i g u r e 2 0 - Plot of L o g P c o versus L o g A H z 0 . 1 = S h a n n o n Sands tone , 2 = Bla i rmore S a n d s t o n e , 3 = O c e a n water , S ta r=Eureka S o u n d Fo rmat ion . T A B L E 4 Standard Enthalpy and Ent ropy of Fo rmat ion of D a w s o n i t e w i th a, b and c Heat C a p a c i t y C o e f f i c i e n t s AH°(298) ) /N S° j /NK° _a_ b_ _c_ - 1 9 5 6 9 4 7 . 5 132.0 14 .8213156 . 0 .37051717 1563478.4 Heat capac i ty f u n c t i o n : C p = a + b T + c / T 2 equ i l i b r i um w i t h the rock. D is t r ibu t ion of s p e c i e s ca lcu lat ions w e r e d o n e us ing a c o m p u t e r p r o g a m ( T H B 2 : P A T H . O , B r o w n and Perkins) that treats the c h e m i c a l system as a- g rand matrix of i n t e r — d e p e n d a n t react ions and so lves all e q u a t i o n s s imul taneous ly . A fo rmal d e s c r i p t i o n of the theory is p r e s e n t e d in Perkins (Masters Thesis) . L imitat ions d o exist , h o w e v e r , regard ing the versiti l ity of the c o m p u t e r p r o g r a m . For e x a m p l e , non—tr iv ia l factors s u c h as react ion k inet ics are n o t c o n s i d e r e d in the c o m p u t e r p r o g r a m , in a d d i t i o n , so l i d s o l u t i o n phases s u c h as alb i te—anorth i te and ankerite c a n n o t b e h a n d l e d d i rect ly by the p r o g r a m . W h e n c o n s i d e r e d , the free energ ies of s u c h phases had to be hand ca lcu la ted a n d a d d e d to the p r o g r a m separately. D is t r ibu t ion of s p e c i e s ca lcu la t ions at temperatu res h igher ' than 298 .15 °K w e r e also not p o s s i b l e w i th albite and anker i te w i t h o u t est imat ing thei r respect i ve C p values. S u c h a t reatment was b e y o n d the s c o p e of this pro ject . A s a result , runs at 298.15 °K served as first a p p r o x i m a t i o n s for a q u e o u s spec ies activit ies u s e d at h igher temperatures . Pure albite and pure ca lc i te r e p l a c e d A n ^ ^ a n d anker i te for runs at temperatu res greater than 298.15°K. The free energ ies of A n n and ankerite at 298.15 °K w e r e ca lcu la ted us ing the f o l l o w i n g f o r m u l a of ideal TABLE 5 N a m e s , C h e m i c a l Formulae , a n d Free Energies of Format ion of the S o d i u m C a r b o n a t e s C o n s i d e r e d in the Inc luded Act iv i ty /Act iv i ty and Partial Pressure D iagrams M i n e r a l N a t r o n T r o n a Thermonat r i te S o d i u m C a r b o n a t e N a h c o l i t e (?) D a w s o n i t e Fo rmu lae N a 2 C 0 3 . 1 0 H 2 O N a 3 H ( C 0 3 ) 2 « 2 H 2 0 * N a 2 C O a « H 2 0 N a 2 C 0 3 N a H C 0 3 N a 2 C 0 3 ' 7 H 2 0 N a A l ( C 0 3 ) ( O H ) 2 Free Energy (Kcals) - 8 1 9 . 5 4 2 - 5 7 0 . 4 0 3 - 3 0 7 . 4 9 2 - 2 5 0 . 4 , - 2 0 3 . 6 , - 6 4 9 . 1 2 2 -426.86„ * T r o n a also c o m m o n l y r e p o r t e d as N a 2 C O 3 • N a H C 0 3 • 2 H 2 0 1. Rossin i et al. (1952) 2. Saegusa (1950) 3. Carre ls a n d T h o m p s o n , u n p u b l i s h e d (Carrels and Chr ist , 1965) 4. R o b i e et al. (1978) m i x i n g : u = Z u .x. + nRT(Zx .Inx.) I I . I I w h e r e : ^. = the free energy of the e n d m e m b e r i x . = the m o l e f ract ion o f e n d m e m b e r i i n = n u m b e r of so lu t i on sites (?) R = 8.417 j o u l e s / m o l e °K T = 298.15 °K Al l c o m p u t e r runs are isothermal and isobar ic w i th pressures restr icted t o 0.1 M P a . Equ i l ib r ium w i th in the c o n s i d e r e d system is a s s u m e d to exist b e t w e e n all phases a n d s p e c i e s w i th in that sys tem. It is impor tant t o n o t e that the f o l l o w i n g t reatment is o n l y i n t e n d e d as a first approximation ca lcu la t ion as the f luid chemist ry o f the TABLE 6 Sys tem: H + — A l + 3 - N a + - H z O React ion A C L o g K e g T r o n a + N a * ( a q ) = 2 N a 2 C 0 3 + H + (aq) + 2 H 2 0 ( l ) 18 .809 - 1 3 . 7 9 0 T r o n a + N a * (aq) = 2Thermonatr i te + H * (aq) 18.009 - 1 3 . 2 0 3 T rona + N a + (aq) + 1 8 H 2 O(l ) = 2 N a t r o n + H + (aq) 14 .329 - 1 0 . 5 0 5 T r o n a + N a + (aq) + 1 2 H 2 0 ( l ) = 2 N a 2 C 0 3 • 7 H 2 O H - H + ( a q ) 15 .029 - 1 1 . 0 1 8 T r o n a + 2 A l + 3 (aq) + 2 H 2 O(l ) = 2 D a w s o n i t e + N a + (aq) + 5 H + (aq) - 2 . 5 2 9 1.854 N a h c o l i t e + N a + ( a q ) = N a 2 C O 3 + H + (aq) 15 .789 - 1 1 . 5 7 6 N a h c o l i t e + N a + ( a q ) + H 2 O ( l ) = T h e r m o n a t r i t e + H * (aq) 15 .389 - 1 1 . 2 8 2 N a h c o l i t e + N a + ( a q ) + 1 0 H 2 O ( l ) = N a t r o n + H + (aq) 13 .549 - 9 . 9 3 3 N a h c o l i t e + N a + ( a q ) + 7 H 2 O( l ) = N a 2 C O 3 • 7 H 2 O + H * (aq) 13 .899 - 1 0 . 1 9 0 N a h c o l i t e + A l + 3 (aq) + 2 H - 2 O ( l ) = D a w s o n i t e + 3 H * (aq) 5.120 - 3 . 7 5 4 N a 2 C 0 3 + H 2 0 ( l ) = Thermonat r i te - 0 . 4 0 0 0.293 N a 2 C 0 3 + 1 0 H 2 0 ( l ) = Nat ron - 2 . 2 4 0 1.642 N a 2 C 0 3 + 7 H 2 0 ( l ) = N a 2 C 0 3 » 7 H 2 0 - 1 . 8 9 0 1.386 N a 2 C 0 3 + A I + 3 ( a q ) + 2 H 2 0 ( l ) = D a w s o n i t e + N a + (aq) + 2 H + ( a q ) - 1 0 . 6 6 9 7.822 Thermonat r i te + 9 H z O ( l ) = N a t r o n - 1 . 8 4 0 1.349 T h e r m o n a t r i t e + 6 H 2 0 ( l ) = N a 2 C O 3 ' 7 H 2 0 - 1 . 4 9 0 1.092 T h e r m o n a t r i t e + A l + 3 ( a q ) + H 2 0 ( l ) = D a w s o n i t e + N a + (aq) + 2 H + (aq) - 1 0 . 2 6 9 7.529 Nat ron = N a 2 C 0 3 • 7 H 2 0 + 3 H 2 0 ( l ) 0 .350 - 0 . 2 5 7 Na t ron + A l + 3 ( a q ) = D a w s o n i t e + N a + (aq) + 2 H + (aq) + 8 H 2 O ( l ) - 8 . 4 2 9 6 .180 N a 2 C 0 3 • 7 H 2 0 + A I * 3 ( a q ) = D a w s o n i t e + N a + ( a q ) + 2 H *(aq) + 5 H 2 0 ( l ) - 8 . 7 7 9 6.436 Trona + H + ( a q ) = 2 N a h c o l i t e + N a + (aq) + 2 H 2 0 ( l ) - 1 2 . 7 6 9 9.361 c o n s i d e r e d sys tem is very p o o r l y cons t ra ined a n d m a n y of the t h e r m o d y n a m i c and c o m p u t e r p r o g r a m l imitat ions may r e d u c e the system to a state of unreal ist ic s impl ic i ty . By c o n s i d e r i n g the assemb lage l isted in Tab le 8 it was p o s s i b l e to const ra in the P , a . , 3 + , a . + / p H , a c . „ , and c a r b o n a t e s p e c i e s activit ies for c o 2 ™' Na D\KJ H any g iven mola l i ty of C a 2 + . C a l c i u m molal i ty was c h o s e n as the i n d e p e n d a n t variable b e c a u s e its activity was the on ly o n e of all the s p e c i e s c o n s i d e r e d that was not f ixed by the assemblage c o n s i d e r e d . By varying the mola l i ty of C a 2 * it was, there fore , p o s s i b l e to d e t e r m i n e a q u e o u s spec ies activit ies u n d e r c o n d i t i o n s w h e r e TABLE 7 Sys tem: A l + 3 - H + - H 2 0 - C 0 2 React ion A C LogKeqr T r o n a + C 0 2 ( g ) = 3 N a h c o l i t e + 1 H z O ( l ) - 2 . 8 3 1 2.076 2Trona = 3Thermonatr i te + 2 H 2 O ( l ) + C O 2 (g) 10.691 - 7 . 8 3 8 2 T r o n a + 2 5 H z O ( l ) = 3 N a t r o n + C O 2 (g) 5.171 - 3 . 7 9 1 2 T r o n a + 1 6 H 2 0 ( I ) = 3 N a 2 C 0 3 « 7 H 2 0 + C 0 2 ( g ) 6.221 ^ . 5 6 1 T r o n a + 3 A l + 3 (aq j + 5H 2 O( l ) + C O 2 (g) = 3 D a w s o n i t e + 9 H + (aq) 12 .529 - 9 . 1 8 5 N a h c o l i t e 4 - A l * 3 (aq) + 2 H 2 0 ( l ) = D a w s o n i t e + 3 H * (aq) 5 .120 - 3 . 7 5 4 N a 2 C 0 3 + H 2 0 ( l ) = T h e r m o n a t r i t e - 0 . 4 0 0 0.293 N a 2 C O 3 - r - 1 0 H 2 O ( l ) = N a t r o n - 2 . 2 4 0 1.642 N a 2 C 0 3 + 7 H 2 0 ( l ) = N a 2 C 0 3 « 7 H 2 0 - 1 . 8 9 0 1.386 N a 2 C 0 3 + 2 A I + 3 ( a q ) + 5 H 2 0 ( l ) + C 0 2(g) = 2 D a w s o n i t e + 6 H * ( a q ) 4 .380 - 3 . 2 1 8 Thermonat r i te + 9 H 2 O(l ) = N a t r o n - 1 . 8 4 0 1.349 Thermonat r i te + 6 H 2 O ( l ) = N a 2 C O 3 • 7 H 2 O - 1 . 4 9 0 1.092 Thermonat r i te + 2Al 3 (aq) + C O 2 ( g ) + 4 H 2 O(l ) = 2 D a w s o n i t e + 6 H * (aq) 4 .789 - 3 . 5 1 1 N a t r o n = N a 2 C O 3 • 7 H z O + 3 H z O ( l ) 0 .350 - 0 . 2 5 7 N a t r o n + 2 A l + 3 ( a q ) + C O 2 ( g ) = 2 D a w s o n i t e + 6 H + (aq) + 5 H 2 0 ( l ) 6.629 - 4 . 8 6 0 N a 2 C 0 3 • 7 H 2 0 + 2 A I + 3 ( a q ) + C 0 2 ( g ) = 2 D a w s o n i t e + 6 H + ( a q ) + 2 H 2 0 ( l ) 6 .279 - 4 . 6 0 3 2 N a h c o l i t e = N a 2 C 0 3 + C 0 2 ( g ) + H 2 0 ( l ) 5.851 - 4 . 2 9 0 2 N a h c o l i t e + 9 H 2 0 ( l ) = N a t r o n + C O 2 ( g ) 3.611 - 2 . 6 4 7 2 N a h c o l i t e + 6 H 2 0 ( l ) = N a 2 C O 3 • 7 H z O + C O 2 ( g ) 3.961 - 2 . 9 0 4 Thermonat r i te + C O 2 (g ) = 2 N a h c o l i t e - 5 . 4 5 1 3.996 2 T r o n a = 3 N a 2 C O 3 + C O 2 ( g ) + 5 H 2 O ( l ) 11.891 - 8 . 7 1 8 hal i te (i.e., the s o u r c e of N a * fo r dawson i te ) beg ins to g o into s o l u t i o n (i.e., w h e r e ' 0 § Q n a | j t e ' > ' 0 8 ' < ' n a | j t e ) a n c ^ thereby a p p r o x i m a t e an u p p e r l imit o n so lu t i on salinity. . Post tec ton ic / l a te stage p o r e waters w i th in the Eureka S o u n d Fo rmat ion at Strand F iord w e r e theoret ica l ly d e t e r m i n e d to b e h ighly sal ine. Results f r o m the analysis are p r e s e n t e d in Table 9. S o d i u m c o n c e n t r a t i o n s as h igh as 95 to 105 g I" 1 are p r o p o s e d at m i d s e c t i o n w i th P va lues as h igh as 0.14 atm. Similarity T A B L E 8 C o m p o n e n t s C o n s i d e r e d in D is t r ibu t ion of S p e c i e s Ana lyses T=298.15°K P = 0.1 M P a C o m p o n e n t s D a w s o n i t e A l p h a Q u a r t z Kaol in i te A n k e r i t e A l b i t e - 9 0 C a l c i t e W a t e r C a l c i u m i on Fo rmu la N a A l ( C 0 3 ) ( 0 H ) 2 S i 0 2 A l 2 S i 2 0 5 ( 0 H ) 2 C a F e ( C 0 3 ) 2 N a g C a j A l i i S i 2 9 O B 0 C a C 0 3 H z O C a 2 + T=333.15°K C o m p o n e n t s D a w s o n i t e A l p h a Q u a r t z Kao l in i te L o w A lb i te C a l c i t e W a t e r C a l c i u m i on P = 0.1 M P a Fo rmu la N a A l ( C 0 3 ) ( 0 H ) 2 S i O z A l 2 S i 2 0 5 ( 0 H ) 2 N a A l S i 3 0 8 C a C 0 3 H z O C a 2 + h igh N a + c o n c e n t r a t i o n s are c o m m o n primari ly in sal ine lakes a n d fo rmat ion water b r ines f o r m e d f r o m such lakes. S o d i u m e n r i c h m e n t in the Eureka S o u n d strata is b e l i e v e d t o result f rom the l iberat ion of N a * u p o n the d i s s o l u t i o n of halite f r o m adjacent d iapi r co res . The p r e s e n c e of d a w s o n i t e is, there fore , b e l i e v e d t o be at t r ibuted t o the e n r i c h m e n t of N a * in c o m b i n a t i o n w i th relatively h igh P , l o w si l ic ic ac id activit ies, and the eventua l destab i l i zat ion of the c a r b o x y l i c a c i d — A l 3 * c o m p l e x . D is t r i bu t ion of s p e c i e s results also ind icate that for e a c h run the IOBQ .. > l o g K .. i r respect ive of temperature . Reasons must , there fore , ° paragon i te ° paragoni te r r be c o n s i d e r e d t o expla in paragon i te ' s a b s e n c e f r o m a system w h i c h thermodynamically favours its p r e s e n c e . As was n o t e d earlier, the p r o g r a m u s e d in this s tudy d o e s not take react ion k inet ics in to c o n s i d e r a t i o n . React ion k inet ics may, in this case, exert s o m e c o n t r o l o n the a b s e n c e of paragon i te a l though quant i f icat ion of this theory is b e y o n d this study. O r g a n i c inh ib i tors , as w e l l , may in s o m e w a y retard the nuc lea t ion of paragoni te f r o m so lu t i on . Results f r o m the p r e c e d i n g t h e r m o d y n a m i c analysis suggests 2 p o s s i b l e insights. First, d a w s o n i t e may be m o r e c o m m o n . in sed imenta ry rocks than is s u g g e s t e d by its relative scarcity f r o m the literature. T h e p r e c e d i n g activity /activity and partial pressure d iagrams have s h o w n that the c h e m i c a l c o n d i t i o n s necessary t o p r o m o t e the prec ip i ta t ion of d a w s o n i t e at standard state tempera tu re and pressure (STP) are f o u n d in a range of present day sed imentary and surficial env i ronments . Barring the effects that t h o s e c h e m i c a l factors no t c o n s i d e r e d in this s tudy (i.e., Eh, si l icic ac id activity, etc) have o n the stabil ity of d a w s o n i t e it appears reasonab le t o assume that d a w s o n i t e is m o r e abundant in the rock r e c o r d than prev ious ly b e l i e v e d . It may be qu i te p o s s i b l e that d a w s o n i t e ' s p r e s e n c e has prev ious ly b e e n e i ther d i s regarded , mis ident i f ied o r c o m p l e t e l y o v e r l o o k e d . This s ta tement is substant iated by persona l c o m m u n i c a t i o n s w i th o the r invest igators w h o have ident i f ied d a w s o n i t e in strata w h e r e it has prev ious ly b e e n o v e r l o o k e d . T A B L E 9 C o m p a r i s o n of Eureka S o u n d Fo rmat ion Fluid C h e m i s t r y w i th the Fluid C h e m i s t r y of o t h e r Natural Systems (mg I" 1 ) L o c a t i o n N a * A l 3 + L o g A l 3 * p H H C 0 3 - L o g P "—CO 2 Ref. O c e a n W a t e r 10,560 1.9 0.27 8.1 140 - 3 . 0 7 2 Great Salt Lake, U t a h 83,600 ' — ? 7.4 251 ? 1 D a n b y Lake, Cal i f . 137 ,580 • — ? — tr ? 1 Sal ine Val ley, Cal i f . 103,000 — ? 7.35 614 . ? 1 Frio S a n d s t o n e 9 ,450 ' 1.7 0.23 7.0 415 ? 2 B la i rmore S a n d s t o n e 3 1 , 5 0 0 4.1 0.61 6.8 140 - 2 . 5 . 2 S h a n n o n S a n d s t o n e 6,300 0.6 - 0 . 2 2 7.6 1.01 - 1 . 7 2 * * * * * * * U p p e r Eureka S o u n d 117,000 0.0 - 8 . 8 3 7.1 66.1 - 1 . 9 9 Exp. M i d Eureka S o u n d 99,000 0.0 - 6 . 6 3 5.8 297 0.14 Exp. 1. Eugster and Hard ie , 1978 2. W h i t e , 1965 The s e c o n d imp l icat ion of the p r e c e d i n g t h e r m o d y n a m i c t reatment is that the p r e s e n c e of d a w s o n i t e in the Eureka S o u n d strata suppo r ts the f ind ings of o t h e r invest igators w h o suggest that the evapor i te diapirs in the A r c t i c A r c h i p e l a g o are c o r e d w i th hal i te . In this study, halite is m o d e l l e d as the s o u r c e of N a for the d a w s o n i t e . As t h e s tud ied s a n d s t o n e s c o n t a i n on ly 1 auth igen ic N a - r i c h phase it was p o s s i b l e to ca lcu la te the prevai l ing c h e m i c a l c o n d i t i o n s w h i c h a l l o w e d d a w s o n i t e to prec ip i ta te w h i l e k e e p i n g all o ther N a - r i c h phases in s o l u t i o n (i.e., halite). The results s h o w that at the po in t w h e r e halite beg ins to g o into s o l u t i o n and d a w s o n i t e p rec ip i ta tes the N a c o n c e n t r a t i o n in s o l u t i o n is as h igh as that in many present day sal ine lakes a n d fo rmat ions . In add i t i on , o n l y those phases w h i c h are present in the s a m p l e s have t h e r m o d y n a m i c stabil ity u n d e r the c o n d i t i o n s ca lcu la ted by the d i s t r ibu t ion of s p e c i e s p r o g r a m . In o t h e r w o r d s , w i th the e x c e p t i o n of py rophy l l i te , t h e c h e m i c a l c o n d i t i o n s ca lcu la ted in the d i s t r ibu t ion of s p e c i e s p r o g r a m d o no t favor the p rec ip i ta t ion of any phases o the r than t h o s e observed in the samples . S H A L E M I N E R A L O G Y A N D D I A G E N E S I S C lay minera l analyses may y ie ld va luable g e n e t i c and d iagenet ic in fo rmat ion a b o u t strata. In s tud ies by Burst (1969), D e S e g o n z a c (1970), M i l l o t (1970), F o l s c o l o s ef al, (1976) and H o w e r ef al, (1976) it has b e e n s h o w n that re lat ionsh ips exist b e t w e e n d e p t h of burial and var ious d iagenet ic parameters relat ing to clays. For e x a m p l e , studies by Burst (1969), F o s c o l o s (1973), Eberl and H o w e r (1976), a n d F o s c o l o s ef al (1976) have s h o w n that as d e p t h o f bur ial increases s o d o e s the sharpness ratio and crystal l inity of i l l ite. Perry (1969), Reyno lds a n d H o w e r (1970), a n d H o w e r (1981) have s h o w n that as d e p t h of burial increases the p e r c e n t a g e of smect i te p resent in i l l i te /smect i te m i x e d layers genera l ly decreases . In o t h e r s tud ies ( W i l s o n and Pi t tman, 1977; Perry and G i l lo t , 1979; S e d i m e n t o l o g y Research G r o u p , 1981 ; A l m o n and Davies, 1981), the de t r imenta l e f fects of detrital a n d au th igen ic clay minerals o n reservoir recovery character ist ics have inc reased the n e e d to bet te r unders tand the ro le that clays play in reservoir m e c h a n i c s . This chapte r examines the clay m inera logy and variations in a n u m b e r of , d i agenet ic parameters t h r o u g h the s t u d i e d s e c t i o n . E X P E R I M E N T A L C l a y S a m p l e P r e p a r a t i o n T w e n t y five shale samples w e r e c h o s e n f r o m 100 m intervals for x—ray d i f f ract ion analyses. Each s a m p l e was initially g r o u n d in a rock c rusher to r e d u c e r o c k f ragment s ize to app rox imate l y 5 m m 3 . The samples w e r e t h e n w a s h e d in d e — i o n i z e d wate r to r e m o v e any clay con taminants w h i c h may have b e e n i n t r o d u c e d by the rock crusher . A l t h o u g h care was taken w h e n c lean ing t h e c rusher b e t w e e n samples , the d e s i g n of the rock c rusher m a d e it i m p o s s i b l e . t o guarantee that s o m e clays w e r e no t p a s s e d f r o m o n e samp le t o the next dur ing s a m p l e preparat ion . O n c e dry, each s a m p l e was g r o u n d t o a f ine p o w d e r in an agate mortar and p l a c e d in a o n e litre b u c k e t f i l led w i t h d e — i o n i z e d water. The clays w e r e d ispersed in the wate r by st irr ing and t h e n a l l o w e d t o sett le for a p e r i o d of 8 hours . Af ter e ight hours the t o p 8 c m of supernatant , c o n t a i n i n g the < 2 . 0 u m f ract ion (Jackson, 1969), w e r e s y p h o n e d off into a separate con ta ine r and left t o stand for 10 t o 14 days. O n c e the clays had sett led c o m p l e t e l y out of the s o l u t i o n the supernatant was d i sca rded a n d the remain ing slurry was set aside for c a t i o n e x c h a n g e t reatment and further s ize f ract ionat ion . Be fore the clays w e r e saturated w i t h a cat ion each s a m p l e was separated in to coarse (0.2 t o 2 .0 j im) and m e d i u m ( < 0 . 2 y m ) s ize f ract ions via cent r i fugat ion . O n e h u n d r e d m l plast ic test t u b e s w e r e f i l led to 1 c m w i t h the clay sample s o l u t i o n and t o p p e d to 10 c m w i th d e — i o n i z e d water. Samples w e r e t h e n c e n t r i f u g e d at 2000 rpm for 50 m inu tes us ing an IEC® cen t r i f uge wi th a n u m b e r 240 head (after B r o w n , 1965 a n d Jackson , 1969). A f te r cen t r i f ug ing , the supernatant , c o n t a i n i n g the less than 0.2 um f ract ion was s y p h o n e d off a n d reserved for later t reatments . The coa rse f ract ion of e a c h s a m p l e was again separated into three por t ions that w e r e subsequent l y : 1) left unt reated ; 2) saturated w i t h K + a n d ; 3) saturated w i t h M g 2 + . C a t i o n e x c h a n g e was a c c o m p l i s h e d by f o l l o w i n g t e c h n i q u e s o u t l i n e d by B r o w n (1965) and Jackson (1969). Twenty t o 25 m g of samp le was p l a c e d in a 15 m l test tube a n d f l o c c u l a t e d in a 1 N c a t i o n — c h l o r i d e so lu t i on (i.e., KCI o r M g C I 2 ) . C a t i o n saturat ion was c o m p l e t e d by success i ve l y cent r i fug ing a n d d e c a n t i n g the s u s p e n s i o n four t imes in the 1 N c a t i o n — c h l o r i d e so lu t i on . Finally, e x c e s s salts w e r e r e m o v e d f r o m the sample by w a s h i n g in 5 0 % m e t h a n o l , 9 5 % m e t h a n o l and t w o success i ve w a s h i n g s in 9 5 % a c e t o n e . It w a s necessary w h e n saturat ing a sample w i t h M g 2 + t o first acidi fy the s o l u t i o n in o r d e r t o avo id p rec ip i ta t ing M g ( O H ) 2 ou t of s o l u t i o n u p o n a d d i t i o n of M g 2 * . A c i d i f i c a t i o n was a c c o m p l i s h e d by a d d i n g 0 .1N HCI d r o p w i s e t o the initial so lu t ion until the p H was b e t w e e n 3.5 and 4. T e n N m a g n e s i u m acetate was u s e d in p lace of M g C I 2 in the first c a t i o n — s o l u t i o n bath. Oriented Samples O n c e c a t i o n saturat ion was c o m p l e t e an equal v o l u m e of w a t e r was a d d e d to the remain ing v o l u m e of the clay slurry. This t h i n n e d slurry was t h e n p i p e t t e d o n t o a glass s l ide and a l l o w e d to dry at r o o m temperature . O n c e dry, each s l ide was x—rayed and then g i y c o l a t e d . C lay samp les w e r e g i yco la ted by p l a c i n g the sl ides face—up in a v a c u u m d e s i c c a t o r o v e r e thy lene g l y c o l for app rox imate l y 24 hours . T h e samp les were x—rayed i m m e d i a t e l y after b e i n g r e m o v e d f r o m the des icca to r in o r d e r t o m in im i ze the a m o u n t of inter layer g l y c o l lost t h r o u g h evaporat ion (Kunze , 1955 ; S r o d o n , 1980).. Finally, clays saturated wi th K* w e r e p l a c e d in an e lect r ic fu rnace and hea ted fo r 2 hours at 500 °C. At the e n d of this t i m e the samples w e r e r e m o v e d and p l a c e d in a d e s i c c a t o r w h e r e they w e r e left t o c o o l . This p r o c e d u r e m i n i m i z e d the a m o u n t of a t m o s p h e r i c wate r r e s o r b e d by clays u p o n c o o l i n g . O n c e c o o l the samples w e r e again x—rayed . Unoriented Samples U n o r i e n t e d samples w e r e p repa red by scrap ing the d r i e d material off of o r i e n t e d s a m p l e m o u n t s w i t h a razor b lade and re—crush ing the clays t o create a f ine p o w d e r . This p o w d e r was t h e n p o u r e d into a " w e l l e d " a l u m i n u m sample h o l d e r and x—rayed . I n s t r u m e n t a l T e c h n i q u e s A l l c lay samples w e r e x—rayed o n a Philips® x—ray d i f f rac tometer us ing a C u K a s o u r c e a n d N i filter. The scan s p e e d u s e d o n all samp les o the r than t h o s e saturated w i t h M g 2 * was 2 ° p e r m i n u t e w i t h a t i m e cons tant of 2 s e c o n d s . V o l t a g e and amperage w e r e set at 4 0 kV and 20 mA , respect ive ly . A l l o r i e n t e d sample preparat ions w e r e s c a n n e d b e t w e e n 3—18° 28. T h o s e samples that had b e e n e x c h a n g e saturated wi th M g 2 * a n d g l y c o l w e r e s c a n n e d b e t w e e n 3—18° 28 and 42—48° 2 d at a scan s p e e d of 1 0 per m inu te w i t h a t ime constant of 1 s e c o n d . These samp les w e r e also s c a n n e d at 1/2° per m inu te b e t w e e n 17 and 18° 28 in o rde r t o d e t e r m i n e a m o r e p rec ise (002)10/ (003)17 re f lect ion l o c a t i o n for ca lcu lat ing the p e r c e n t a g e of illite in i l l i te / smect i te m i x e d layer clays. The K* saturated samples w e r e u s e d t o examine fo r var iat ions th rough the s e c t i o n in the illite crystall inity index (Kubler , 1966) and sharpness ratio of the 1.0 n m peaks (Weaver , 1961). M g 2 * — g l y c o l saturated samples w e r e u s e d for p e r c e n t illite de te rm ina t ions and d iscrete layer si l icate ident i f icat ion . U n o r i e n t e d samp le preparat ions w e r e s c a n n e d b e t w e e n 50—58° 29 at 2 ° per m i n u t e in o r d e r t o examine the (060)10 re f l ec t ion . T h e p o s i t i o n of this re f lect ion was u s e d t o di f ferent iate b e t w e e n d i — and t r ioctahedra l 2:1 si l icates (Jackson, 1956). Analytical Techniques Analyt ica l t e c h n i q u e s u s e d for spec i f i c clay mineral analyses have b e e n d iv ided into the f o l l o w i n g categor ies : — C l a y minera logy . — Semi—quant i tat ive minera logy . — M i x e d layer analyses. — Sharpness ratio and illite crystall inity index . Clay Mineralogy Ident i f icat ion of clay minerals was b a s e d o n changes in d i f f ract ion peak l o c a t i o n s f o l l o w i n g di f ferent samp le t reatments . Ident i f icat ion cr i ter ia w e r e as f o l l o w s : 1) K a o l i n i t e — has (00/) d—spacings of 0.715 n m and 0.35 n m w h i c h are unaf fected by ca t ion saturat ion and g lyco la t ion . T h e s e peaks d issappear u p o n heat ing at 500 °C f o r 2 hours . 2) I l l i te— has a (001) d — s p a c i n g of 1.0 n m w h i c h varies sl ightly d e p e n d i n g o n the a m o u n t o f s m e c t i t e present (Reynolds & H o w e r , 1970). The 1.0 n m peak increases in intensity and sharpness u p o n saturat ion w i th K + . H e a t i n g t o 500 °C leaves this peak unaf fected . Jackson (1956) reports that d i o c t a h e d r a l illite p r o d u c e s a (060) re f lect ion at 0.15 n m w h i l e t r ioctahedra l i l l ite has a (060) peak in the 0 . 1 5 2 5 - 0 . 1 5 3 4 n m range. 3) C h l o r i t e — has (00/) spac ings of 1.4 and 0.715 n m w h i c h can be c o n f u s e d w i t h ve rmicu l i te a n d kaol in i te . It is d i s t i ngu ished f r o m all but n o n — A l 3 * ve rmicu l i te (B rown , 1969) by saturating w i t h K * . U p o n t reatment w i t h K * , n o n — A l 3 * ve rmicu l i te co l l apses t o 1.0 n m w h i l e ch lo r i te and A l 3 * ve rmicu l i te persist at 1.4 n m . A f te r heat ing t o 500 °C for 2 hours all 1.4 n m vermicu l i te wi l l co l lapse t o 1.0 n m w h i l e the 1.4 n m ch lo r i te peak wi l l increase in intensity. 4) V e r m i c u l i t e — has a (001) d — s p a c i n g of 1.4 n m w h e n saturated w i t h M g 2 * at a relative h u m i d i t y of approx imate ly 4 0 % (Brindley, 1980). This d—spac ing increases to rough ly 1.52 n m w h e n g i yco la ted and c o l l a p s e s t o 1.0 n m w h e n heated t o . 500°C fo r 2 hours . 5) S m e c t i t e — like vermicu l i te , smect i te co l lapses to 0 .95—1.0 n m w h e n hea ted for 2 hours at 500°C. Br ind ley (1980) d e m o n s t r a t e s h o w saturat ion w i th d i f ferent cat ions w i l l result in di f ferent (00/) d—spac ings . For the p u r p o s e of this study, smect i te (001) d—spac ings at 4 0 % relative humid i t y are approx imate l y 1.1—1.25 n m a n d 1.1 n m fo r M g 2 * and K * saturated samp les , respect ive ly . G i y c o l a t e d samp les e x p a n d t o approx imate l y 1.69 n m . 6) . M i x e d layer c lays— the ident i f icat ion of i l l i te /smect i te m i x e d layers is d i s c u s s e d in a later s e c t i o n . Semi—quantitative M i n e r a l o g y Semi—quant i tat ive est imates of the relative p r o p o r t i o n of e a c h clay type in each sample was d e t e r m i n e d by m e t h o d s o u t l i n e d by Bayliss ef al. (1970). The he ight of the re f lect ions at 0.7 n m (kaolinite) , 1.0 n m (illite), 1.4 n m (vermicul i te) , 1.4 n m (chlor i te) , and 1.7 n m (smect i te) w e r e m e a s u r e d o n M g 2 * saturated samples . A c o r r e c t i o n factor of 8:8:2:2:2 was t h e n m u l t i p l i e d by the respect ive peak he ights to c o m p e n s a t e for Lorentz po la r i zat ion (Bustin and Bayliss, 1979). The a b o v e m e n t i o n e d p r o c e d u r e quant i f ies on ly the p r o p o r t i o n s of each clay type p resent in a sample but says n o t h i n g about h o w t h o s e clays are d is t r ibuted b e t w e e n m i x e d layered and d i sc re te clays. T o quanti fy the d is t r ibu t ion of d iscrete smect i te , d i sc re te i l l ite, and m i x e d layer i l l i te /smect i te p resent the f o l l o w i n g t e c h n i q u e was e m p l o y e d : 1) D i f f ractograms of M g saturated clays w e r e e x a m i n e d for re f lect ions in the 15.65—17.65° 26 range. If d i sc re te s m e c t i t e and illite w e r e p resent there w o u l d be re f lect ions at 15.78° a n d 17.65° 26, respect ive ly (Reyno lds and H o w e r , 1970). 2) The ratio of illite t o s m e c t i t e in i l l i te /smect i te m i x e d layers (see f o l l o w i n g sect ion) was ca lcu la ted for each sample . This value was t h e n n o r m a l i z e d to 1 smect i te (i.e., X . j | . t e : 1 ) . The X - | j j t e va lue o f this te rm wil l be referred t o as ' X j ' . 3) If, f r o m the di f f ractograms, it w a s d e t e r m i n e d there was n o d iscrete smect i te p resent it was a s s u m e d that of all the smect i te f r o m the total clay ca lcu lat ions was t i ed u p in the i l l i te /smect i te m i x e d layers. This value of total smect i te (S,. J ' tot was then mu l t i p i ed by X| t o d e t e r m i n e the pe rcen tage of illite ( l m j x ) in the l/S m i x e d layers. The s u m of I . and S . (the p e r c e n t a g e of smect i te in l/S) ' m ix mix r ° gave the tota l pe rcen tage of l/S m i x e d layers present . The d i f fe rence b e t w e e n 'mix a n c ' ^ e t o t a ' P e r c e n t a 8 e ° f 'H ' t e i n the sample 0 t o t ) r e p r e s e n t e d the p e r c e n t a g e of illite that o c c u r s as d isc re te illite. 4) If l m ) . x was greater than I I was ass igned c o m p l e t e l y t o l/S m i x e d layers and a n e w S . was ca lcu la ted . Intuitivly, the n e w S . w o u l d have to be less mix 7 mix than o r equa l S 4 .. The d i f fe rence in S . and S^ . w o u l d , there fore , be ^ tot mix tot u n a c c o u n t e d for if it had b e e n p rev ious ly d e t e r m i n e d that d iscrete smect i te was not p resent . This ' res idual ' smect i te w o u l d have t o be att r ibuted t o error, o t h e r s m e c t i t e m i x e d layers (i.e., ch lo r i te / smect i te ) o r the p resence of d iscrete smect i te in s u c h smal l p r o p o r t i o n s that the (002)10/ (003)17 re f lect ion was t o o w e a k t o be r e c o g n i s e d . Th is a p p r o a c h p r o d u c e d values for the maximum p o s s i b l e p e r c e n t a g e of b o t h l/S m i x e d layers and d iscrete smect i te and a minimum p o s s i b l e p e r c e n t a g e of d iscrete illite that c o u l d have b e e n present in e a c h sample : Mixed layer Analyses B o t h m i x e d layer i l l i te /smect i te and m i x e d layer c h l o r i t e / s m e c t i t e w e r e ana lysed in the current study. It was a t t e m p t e d to de te rm ine the p e r c e n t a g e of ch lo r i te in m i x e d layer c h l o r i t e / s m e c t i t e by us ing the t e c h n i q u e s of Reyno lds and H o w e r (1970), w h o u s e d shifts in the l o c a t i o n of s e c o n d and th i rd o r d e r peaks as a measure of % ch lo r i te in g i yco la ted samples . D u e to the p r e s e n c e of ve rm icu l i t e at approx imate ly 1.4 n m a n d kaol in i te at 0.71 n m the true p o s i t i o n s of the ch lo r i t e / smect i te peaks w e r e m a s k e d a n d the de te rm ina t i on of %" ch lo r i te in c h l o r i t e / s m e c t i t e m i x e d layers was, there fore , not poss ib le in this study. T w o di f ferent m e t h o d s w e r e c o n s i d e r e d fo r d e t e r m i n i n g the p e r c e n t a g e of il l ite in the i l l i te /smect i te m i x e d layers. The first f o l l o w e d the m e t h o d of S r o d o n (1980) w h e r e the d i f fe rence in 28 b e t w e e n t w o ref lect ions in the 42—48° 28 r e g i o n was u s e d as a measure of the p r o p o r t i o n of illite. The s e c o n d m e t h o d d e t e r m i n e s the p r o p o r t i o n of illite based o n the p o s i t i o n i n g of the (002)10/ (003)17 peak (Reyno lds and H o w e r , 1970). The fo rmer m e t h o d is be l i eved by the au tho r to be a m o r e accurate measure of %—i l l i te as the latter neg lects to take 'smal l d o m a i n s ize ' i n to a c c o u n t ( d o m a i n size b e i n g that v o l u m e o f ' a st ructure w h i c h scatters x—rays coheren t l y ( S r o d o n , 1980)). S r o d o n (1980) repor ts that a smal l d o m a i n s ize w i l l con t r i bu te t o shi f t ing of the (002)10/ (003)17 peak l o c a t i o n and thus i n t r o d u c e add i t iona l error t o the analysis. P r o b l e m s assoc ia ted w i t h S r o d o n ' s (1980) m e t h o d are that for m i x e d layers c o n t a i n i n g > 8 0 % illite t w o ref lect ions in the 42—48° 28 range c a n n o t b e d i f fe rent iated d u e t o over lap o f the peaks. U s i n g Reyno ld a n d H o w e r ' s (1970) m e t h o d , the p r o p o r t i o n of il l ite in i l l i te /smect i te m i x e d layers was d e t e r m i n e d by c o m p a r i n g the d i f f ractograms o b t a i n e d f r o m the clay analyses w i th the data of Reyno lds and H o w e r (1970) (Table 10). This m e t h o d requ i red p e r f o r m i n g a l inear i n te rpo la t ion of Reyno lds and H o w e r ' s data . The ob ject i ve of this in te rpo la t ion was to express the i r data as a series of l inear equa t ions f rom w h i c h il l ite p r o p o r t i o n s c o u l d be d e t e r m i n e d g i ven the p o s i t i o n of the (002)10/ (003)17 peak. A l t h o u g h the data of Reyno lds and H o w e r (1970) appears t o have a s igmo ida l d is t r ibut ion w i t h respect to il l ite p r o p o r t i o n a n d the p o s i t i o n i n g of the s e c o n d and th i rd o r d e r re f lect ion peaks there is n o theoretical just i f icat ion for f itt ing h igher o rder po l ynomia l s (i.e., cub ic ) t o the data, in add i t i on , as the exper imenta l error assoc ia ted w i th the data was not r e p o r t e d it can on ly b e a s s u m e d that the re lat ionsh ip is at best linear. Examp le A d i f f ractogram indicates that n o re f lect ions o c c u r at 15.78° 28, therefore , n o d iscrete smect i te is present . M i x e d layer percent—i l l i te ca lcu lat ions reveal that m i x e d layers are c o m p o s e d of 8 5 % illite and 1 5 % smect i te . There fore , I l l i te /smectite ratio = 85:15 N o r m a l i z e d ratio = 5.66:1 %ll l i te in l/S M i x e d - L a y e r s Figure 21- Plot of var iat ions in (002)10/(003)17 illite peak l o c a t i o n w i th variations in %i l l i te in i l l i te /smect i te mixed - layer clays. TABLE 10 Pos i t ions of the (002)10/(003)17 Di f f ract ion Peak for Var ious % ll l ite in I l l i te /Smectite Va lues % ll l ite in l/S (002)10/ (003)17: 2 0 0 15 .78 20 15 .87 40 16.15 60 16 .58 80 17 .19 90 17 .50 100 17.65 Data of Reyno lds and H o w e r , 1970 X | = 5.66 Total—clay ca lcu la t ions reveal that the samp le is c o m p o s e d of: 5 5 % kao l in i te 40% i l l ite 4% smect i te 1 % vermicu l i te there fore , l t o t = 40 ^ t a t - S m i x - 4 ' m i x = S m j x * X | = 23 and , there fo re , Tota l % l/S m i x e d layers = I m j x + S m j x = 2 7 % Tota l % d iscrete illite = l t o t — l m j x = 1 7 % Sharpness Ratio and Illite Crystallinity Index T w o 1.0 n m peak shape parameters are u s e d in this study t o app rox imate t h e deg ree of shale d iagenes is in the s t u d i e d s e c t i o n . T h e s e parameters are W e a v e r ' s (1961) sharpness ratio w h i c h c o m p a r e s the he ight o f the peak at 1.0 n m t o the he ight of the re f lect ion at 1.05 n m and illite crystall inity, w h i c h is m e a s u r e d us ing Kubler 's (1964) ' i l l i te crystal l inity index ' w h e r e t h e (001) peak w i d t h is m e a s u r e d at half height . A s scan s p e e d s and chart s p e e d s can vary f rom o n e study to another it is m o r e c o n v e n i e n t t o report illite crystal l inity va lues in d e g r e e s A20 rather than mi l l imeters . RESULTS Clay Mineralogy A p p e n d i c e s 1—3 s h o w the d i f f ract ion peak l o c a t i o n s f o r all samples w i t h each di f ferent t reatment . F rom an e x a m i n a t i o n of these tables the clay minera logy of each sample and the sect ion in genera l was d e t e r m i n e d . The results indicate that kaol in i te , i l l ite, and poss ib ly ve rmicu l i te persist t h r o u g h the ent i re sec t i on . There is, however , , s o m e var iat ion in the relative p r o p o r t i o n of il l ite (see f o l l o w i n g sect ion ) . C h l o r i t e is apparent ly restr icted t o z o n e 4 whi le smect i te is apparent ly less abundant t h r o u g h z o n e 4 than e l sewhere . D i — o c t a h e d r a l 2:1 si l icates persist t h rough the entire s e c t i o n (Table 11). T A B L E 11 Var iat ions in Smect i te (060) d - s p a c i n g (in nm) T h r o u g h S e c t i o n H e i g h t D i—octahedra l Tr i—octahedral ( 0 . 1 4 9 - 0 . 1 5 1 ) ( 0 . 1 5 2 - 0 . 1 5 3 ) 656 0.149 748 0.1505 — 8 9 2 0 .1510 — 919 0 .1507 •. — 1058 0 .1496 . — 1070 0 .1499 — 1120 . 0 . 1 5 1 2 — 1268 0 .1497 — 1330 — — 1551 0.1511 1699 0 .1510 — 1830 0 .1507 • —• 2100 0.1502 — • 2173 0 .1505 — 2243 0 .1510 • — . 2358 — ' — 2419 0 .1492 — 2967 0.1501 — Semi—quantitative M i n e r a l o g y Semi—quant i tat ive results of tota l—clay percentages t h r o u g h the s tud ied s e c t i o n are l is ted in Tab le 12. Genera l t rends ind icate that as the p e r c e n t a g e of kaol in i te d e c r e a s e d w i t h increas ing d e p t h t h r o u g h z o n e 4, the p e r c e n t a g e of total illite i nc reased . At the boundary b e t w e e n z o n e s 3 and 4 there is a sharp reversal in their relative, p ropo r t i ons . T h r o u g h z o n e s 2 and 3, kaol in i te a n d illite p r o p o r t i o n s r e m a i n e d approx imate ly constant . The major po int of interest w i t h respect to s m e c t i t e is that t h rough the u p p e r 2/3 of the s t u d i e d s e c t i o n the p e r c e n t a g e o f s m e c t i t e was l o w (<2%) and rema ined app rox imate l y cons tan t w i th increas ing d e p t h . B e l o w z o n e 4 there was a sharp increase in the p e r c e n t a g e of tota l smect i te t o app rox imate l y 4%, w h i c h rema ined h igh to the base. Figure 22 d e m o n s t r a t e s graphical ly h o w the sample c o m p o s i t i o n s vary w i t h d e p t h . Tab le 13 out l ines the d is t r ibut ion of c lay—types t h r o u g h the the s t u d i e d s e c t i o n . The main t rend t o n o t e here was that b o t h d iscrete il l ite a n d ch lor i te w e r e rest r ic ted t o z o n e 4. M i x e d layer i l l i te /smect i te was relatively absent t h r o u g h this same interval . Figure 23 ind icates graphical ly h o w the the relative p r o p o r t i o n s of clay vary w i th d e p t h . Percent Smectite in lllitel Smectite Mixed layers A n examina t ion of the d i f f ractograms f r o m the present s tudy revea led that o n l y o n e peak was present in the 42—48° 26 range in all samples . The a b s e n c e of t w o peaks in this range s u g g e s t e d , us ing S r o d o n ' s (1980) m e t h o d , that n o w h e r e in the s e c t i o n d i d the % — s m e c t i t e in i l l i te /smect i te m i x e d layers e x c e e d 15%. In a separate at tempt t o de te rm ine a va lue for the % — s m e c t i t e it was a s s u m e d that the d o m a i n size o f all samples t h r o u g h the s e c t i o n was large e n o u g h to m i n i m i z e t h e a m o u n t of error attr ibutable t o smal l d o m a i n s ize . This a s s u m p t i o n p e r m i t t e d the app l icat ion of Reyno ld and H o w e r ' s (1970) m e t h o d of %—i l l i te d e t e r m i n a t i o n . Figure 24 illustrates the variat ions in the pe rcentage of il l ite w i t h d e p t h that w e r e ca lcu la ted t h r o u g h the s e c t i o n us ing Reyno lds and H o w e r ' s (1970) m e t h o d . In 99 F i g u r e 22- Plot of var iat ions in shale c o m p o s i t i o n w i th d e p t h and th rough ind iv idual pa l eo - env i ronments . K = kaol in i te , 1 = total und i f ferent iated il l ite, V = vermicu l i te , C = ch lor i te and /o r n o n - A l ve rmicu l i te , S = total smect i te . 100 3 0 0 0 ,500 H 1 1 1—-i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 — 1 — 5 0 60 70 8 0 90 100 Percent Figure 23- P lot of var iat ions in shale c o m p o s i t i o n w i th d e p t h a n d th rough ind iv idua l p a l e o - e n v i r o n m e n t s . K = kaol in i te , l = d iscrete illite, l / S= i l l i te /smect i te mixed- layers , S = d iscrete and undi f ferent iated smect i te , V = vermicu l i te , C = ch lo r i te a n d / o r n o n - A l ve rmicu l i te . ' 101 F i g u r e 24 - Plot of var iat ions in the percentage of i l l ite in i l l i te /smect i te m i x e d - l a y e r e d clays wi th d e p t h and th rough the indiv idual p a l e o e n v i r o n m e n t s of R A K - 2 6 . T A B L E 12 Semi—quant i tat ive M i n e r a l o g y of S tud ied S e c t i o n w i t h Und i f fe rent ia ted Illite (%) H e i g h a/b Kao J ! C h i V e r m S m e c 656 69 29 0 2 0 748 75 19 0 3 3 892 70 23 0 3 4 1058 76 18 0 3 3 1070 54 40 4 ? 2 1120 55 42 4 ? 0 1268 56 39 . 3 ? 2 1490 54 44 3 ? 0 1551 57 39 3 ? 1 1699 60 37 3 ? 0 1755 60 36 3 ? 1 1830 60 36 4 ? o 1866 62 35 3 ? 1 2100 79 18 1 ? 1 2173 84 13 0 2 1 2243 67 29 0 2 2 2419 71 27 0 1 1 2967 64 30 0 •3 2 eight aJb = height , a b o v e base (metres) . K a o = kaol in i te , l l l = total i l l ite, S m e c = total smect i te , V e r m = vermicu l i te , C h l = ch lor i te genera l , the pe rcen tage of il l ite at the t o p of the s e c t i o n (~88%) increases to approx imate ly 1 0 0 % at the base of z o n e 4. B e l o w z o n e 4 there is a - relatively sharp increase in the pe rcen tage of smect i te and decrease in the percentage of ill ite. W i t h i n z o n e 3 the illite p e r c e n t a g e again increases t o w a r d the base of the s e c t i o n . TABLE 13 Semi—quant i tat ive M i n e r a l o g y of S t u d i e d S e c t i o n w i t h D i f fe rent iated Illite (%) • H a/b Kao lll(d) Smec(d ) C h i V e r m Ill /Sm 656 69 29 0 0 2 0 748 75 20 0 0 3 0 892 70 0 4 0 3 23 1058 76 0 3 0 3 18 1070 54 41 0 4 ? 0 1120 55 42 0 4 0 1268 56 43 0 3 0 1490 54 44 0 3 . 0 1551 57 0 1* 3 39 1699 60 37 o 3 0 1755 60 0 1* 3 36 1830 60 36 0 4 0 1866 62 35 0 3 0 2100 79 0 1* 1 18 2173 84 0 1* 0 2 13 2243 67 0 2* 0 2 29 2419 71 0 1* 0 1 27 2967 64 0 2* 0 3 31 H a / b = height above base (metres) , K a o = kaol in i te , lll(d) = d iscrete il l ite, Smec(d ) = d isc re te smect i te , V e r m = vermicu l i te , C h l = ch lor i te , l l l / S m e c = i l l i te /smect i te m i x e d layers (*) ind icates maximum p o s s i b l e va lue i.e., (002)10/ (003)17 re f lect ion at 5 . 6 2 - 5 . 6 6 A was w e a k o r absent . Illite Crystallinity Index Illite crystall inity values w e r e f o u n d t o dec rease w i th increas ing d e p t h th rough the u p p e r 2/3 of . the s e c t i o n . Crystal l in i ty values d e c r e a s e d f r o m app rox imate l y 0.85 A 2 0 at the t o p of the s e c t i o n t o approx imate ly 0.33 A 2 0 at the base of z o n e 4 (Table 14). W i t h i n z o n e s 2 and 3, the crystall inity of illite appears t o s h o w n o re lat ionsh ip to increasing d e p t h (Figure 25). W h e t h e r this r a n d o m d is t r ibut ion of illite crystall inity t h r o u g h o u t z o n e s 2 and 3 is real o r no t is d i s c u s s e d in a later s e c t i o n . Sharpness Ratio Sharpness ratio values s h o w a simil lar t rend to that of illite crystall inity. The ratio increases m o r e or less l inearly f rom a p p r o x i m a t e l y 1.20 at the t o p of the s e c t i o n t o approx imate ly 1.60 c l o s e to the base of z o n e 4 (Table 15). B e l o w z o n e 4, h o w e v e r , the sharpness ratio decreases l inearly t o approx imate ly 1.05 at the base of z o n e 2 (Figure 26 ) . . D I S C U S S I O N Shale analysed f r o m the d o m a i n of d iagenes is usually conta ins b o t h a detrital and d iagenet ic clay c o m p o n e n t . O n l y after l o w grade m e t a m o r p h i c pressures and temperatu res are attained w i l l the majority of the detr ital clay c o m p o n e n t n o l onger exist in a f o r m w h i c h has b e e n unaf fected by its physical and c h e m i c a l e n v i r o n m e n t (i.e., i nc reas ing temperature and pressure, var iat ions in pore water chemist ry , etc. ) . Ca re must , there fore , be taken w h e n interpret ing clay analyses to di f ferent iate results attr ibutable to the detrital c o m p o n e n t f rom t h o s e attr ibutable to the d iagenet ic c o m p o n e n t . A n examina t ion of the shale c o m p o s i t i o n p lo ts (Figures 22 and 23) ind icates that p a l e o — e n v i r o n m e n t s and p rovenance , rather than auth igen ic minera logy , exert pr imary c o n t r o l o n p r o d u c i n g the o b s e r v e d d is t r ibut ion of clay minerals w i t h d e p t h . This d o e s not , however , total ly d ismiss the p r e s e n c e of a d iagenet ic c o m p o n e n t . F i g u r e 2 5 - Plot of var iat ions in illite crystallinity t h rough sec t ion and indiv idual p a l e o - e n v i r o n m e n t s . F i g u r e 26 - Plot of var iat ions in the 1.0:1.05 n m peak sharpness ratio t h r o u g h s e c t i o n and ind iv idual p a l e o - e n v i r o n m e n t s . TABLE 14 Var iat ions in ll l ite Crystal l in i ty w i t h D e p t h H e i g h t a b o v e base (m) lllite Crystal l in i ty Index 656 0.55 748 0.85 892 0.77 919 0.50 1058 0.65 1070 0.34 1120 0.45 1268 0.49 1330 0.46 1490 0.40 1551 0.50 1699 0.45 1755 0.49 1830 0.49 1866 0.50 2100 0.70 2173 0.75 2243 0.73 2358 0.67 2419 0.55 2967 0.65 In these p lo ts it can be s e e n that the gross c h a n g e s in m ine ra logy and reversals in clay p r o p o r t i o n t rends o c c u r pr imari ly at z o n e ( l i thofacies) boundar ies . For example , , ch lo r i te is rest r ic ted to z o n e 4, kao l in i te c o n t e n t dec reases t h r o u g h z o n e 4, a n d smect i te and kaol in i te p r o p o r t i o n s increase sharply at the b o u n d a r y b e t w e e n z o n e s 3 a n d 4. En igmat ic shifts in illite crystall inity values, sharpness ratios and the p e r c e n t a g e if ill ite in l/S m i x e d layers at z o n e b o u n d a r i e s (i.e., z o n e s 3 and 4) also suggests that l i thofacies exert c o n t r o l o n t rends in clay d iagenesis parameters . TABLE 15 Var iat ions in Sharpness Ratio w i th D e p t h H e i g h t •ove base (m) Sharpness Ratio 656 1.060 748 1.108 892 1.289 919 1.220 1058 1.429 1070 1.631 1120 1.444 1268 1.478 1330 1.444 1490 1.427 1551 1.316 1699 1.364 1755 1.383 1830 1.347 1866 1.324 2100 1.225 2173 1.194 2243 1.356 2358 1.291 2419 1.219 2967 1.219 C o n t r o l , in this case , c o m i n g f r o m var iat ions in e i ther detr i ta l m ine ra logy o r f lu id chemis t ry u n i q u e to e a c h z o n e (i.e., P . , P, - . - . , [cation]). 112*-' ' \—U 2 W i t h i n e a c h z o n e , and in s o m e cases t h r o u g h adjacent z o n e s , there is e v i d e n c e t o s u p p o r t the d iagenet ic overpr in t ing of the detr ital minera logy . For e x a m p l e , t h e increases in il l ite crystall inity, sharpness ratio va lues a n d %i l l i te in l/S f r o m the t o p of the s e c t i o n to the base of z o n e 4 suppo r ts d i a g e n e t i c alterat ion of i l l ite. Similarity, c o i n c i d e n t increases a n d decreases of d i f ferent c lay minerals o v e r spec i f ic intervals suggests that p o s s i b l e d i a g e n e t i c react ions may b e tak ing p lace . Be fore e x a m i n i n g the d iagenet ic t rends a n d s o m e of the assoc ia ted p r o b l e m s , h o w e v e r , it is first necessary t o identi fy the " d i a g e n e t i c f a d e s " that is r e p r e s e n t e d by the Eureka S o u n d strata a l o n g Kanguk Pen insu la . Diagenetic Fades and Sub—facies A l t h o u g h there exists n o universal ly a c c e p t e d de f in i t ion of d iagenes is the 1980 Glossary of Geology (Bates ef al., 1980) de f ines d iagenes is as: ' c h e m i c a l , phys ica l , and b i o l o g i c a l c h a n g e s u n d e r g o n e by a s e d i m e n t after its or ig ina l d e p o s i t i o n . . . e x c l u s i v e of surficial a lterat ion and m e t a m o r p h i s m . . . . It e m b r a c e s t h e p rocesses . . . that o c c u r u n d e r pressure (up to 1 ki lobar) and tempera tu re ( m a x i m u m range o f 100 ° C t o 300 °C) that are no rma l t o the surficial o r o u t e r part of the earth's crust. ' The temperatu re and pressure const ra ints u s e d in this de f in i t i on m a y be mis lead ing , h o w e v e r , b e c a u s e they imply that the l o w e r l imits of m e t a m o r p h i s m are abso lu te (i.e., P > 1 K b ) and d e f i n e d w i t h o u t regard t o phase stabil ity f ie lds. Because m e t a m o r p h i c facies are d e l i n e a t e d in P—T space by the minera l assemb lage stabil ity f ie lds, a pre fer red cr i teron for mark ing the d i a g e n e t i c / m e t a m o r p h i c boundary is g iven by W i n k l e r (1967). ' M e t a m o r p h i s m has b e g u n and d iagenes is has e n d e d w h e n a minera l assemb lage is f o r m e d w h i c h c a n n o t or ig inate in a sed imentary env i ronment . ' A l t h o u g h W i n k l e r ' s de f in i t ion may perhaps be pre fer red it is still n o t w i t h o u t fault. For e x a m p l e , if it is assumed that a ' sed imentary e n v i r o n m e n t ' e x t e n d s n o d e e p e r than the s e d i m e n t / w a t e r interface then d iagenes is has e n d e d o n c e pyrite beg ins t o prec ip i tate just b e l o w the s e d i m e n t / w a t e r interface. It, there fore , n o w b e c o m e s apparent that in having t o de f i ne a ' sed imentary env i ronment ' a certa in d e g r e e of cycl ic i ty is i n t r o d u c e d into t ry ing to de f ine d iagenes is . W i n k l e r ' s d e f i n i t i o n of d iagenes is c o u l d perhaps b e i m p r o v e d if it c o n t a i n e d a m o r e r igo rous de f in i t ion of a ' sed imenta ry e n v i r o n m e n t ' . Figure 27 ind icates the de l in ia t ion of d iagenes is in P—T s p a c e relative t o m e t a m o r p h i s m . A t t e m p t s to establ ish a p r e — m e t a m o r p h i c facies s u b d i v i s i o n s c h e m e (i.e., a n k i z o n e and d iagenes is ) b a s e d o n 1 .0nm peak m o r p h o l o g y parameters have b e e n relatively unsuccess fu l . This is pr imari ly d u e t o the fact that p rev ious invest igators have d e f i n e d p r e — m e t a m o r p h i c facies in terms of minera l assemb lages (i.e., a n k i z o n e = il l ite, l aumon i te , l awson i te , p rehn i te , pumpe l l y i te ) a n d t h e n a t t e m p t e d to de l ineate the facies in terms of s o m e o the r parameter that is a f u n c t i o n of m o r e than just temperatu re and pressure (i.e., illite crystal l inity values). As a result, a range of i l l ite crystal l inity va lues as var ied as the chemis t ry o f the units f r o m w h i c h they w e r e de r i ved have b e e n u s e d to mark the d i a g e n e s i s / a n k i z o n e b o u n d r y (i.e., O . 3 2 A 2 0 (Sagon and de S e g o n z a c , 1970), O . 4 3 A 2 0 ( is lam and H e s s e , 1983), O . 5 6 A 2 0 (Frey ef al, 1980), O . 6 4 A 2 0 ( C h e n n a u x ef al, 1970)). U s i n g the temperatures and pressures d e r i v e d f r o m the p rev ious c h a p t e r o n c o a l (i.e., m a x i m u m of 95 ° C and 1.27Kbars) the s t u d i e d strata appear to lie w i th in d iagenet ic , rather than a n k i m e t a m o r p h i c , P—T space (Figure 27). Tradit ional ly , the crystal l inity of ill ite, sharpness ratios and p r o p o r t i o n of s m e c t i t e in i l l i te /smect i te m i x e d layers have b e e n u s e d to de l ineate d iagenet ic substages . O n e n a n o m e t r e peak m o r p h o l o g y parameters , h o w e v e r , have recent ly b e e n s h o w n t o b e l e s s — t h a n - r e l i a b l e ind icators of pressure and tempera tu re d u e to their maturat ion d e p e n d e n c e o n factors s u c h as var iable c a t i o n activit ies (Eberl and H o w e r , 1978) . Inaccuracies are espec ia l l y prevalent in p r e — a n k i z o n e stages w h e r e water a n d c a t i o n c i rcu la t ion is less restr icted. For e x a m p l e , var iat ions in [ K V o t h e r F i g u r e 2 7 . Plot of d iagenet ic facies in P-T space. cat ions] are k n o w n to have a s igni f icant ef fect o n clay d iagenes is parameters . L o w [ K + / N a + + C a 2 + ] are s u g g e s t e d by Eberl and H o w e r (1978) to retard the i l l i t izat ion of smect i te w h i l e the crystall inity of illite is said by H o w e r et al (1976) to be d i rect ly , re la ted to the activity of K + in s o l u t i o n . A d d i t i o n a l p r o b l e m s arise w h e n us ing clay d iagenes is parameters t o de l ineate d iagenet ic sub—stages . A c c o r d i n g to F o s c o l o s ef al (1976) a n d F o s c o l o s (1980) variations in e x p a n d a b l e layer chemis t ry and s o u r c e rock c o n t r i b u t i o n s of m i c a c e o u s material may con t r i bu te to the 1.0 h m peak m o r p h o l o g y dur ing the early a n d m i d d l e stages o f d iagenes is . W e a v e r and Broekstra 's (1984) f ind ings s u p p o r t this observat ion n o t i n g that at temperatures less than 360 ° C the w i d t h of the (001) peak is a f fec ted by the a m o u n t and c o m p o s i t i o n of the l/S c o m p o n e n t p resent (S rodon , 1978 , 1984; W e a v e r ef al., 1984; S r o d o n and Eberl , 1984). It is, there fore , s u g g e s t e d that var iat ions in 1.0 n m peak m o r p h o l o g y parameters w i t h d e p t h are s imply re f lect ions of variat ions in the smect i te c o n t e n t of the m i x e d layers and , there fore , re f lect ions of variat ions in f o rmat ion f lu id a n d l i t ho logy chemist ry . Thus, because il l ite crystal l inity and sharpness ratios are a f u n c t i o n of m o r e than just temperature , ass ign ing rocks to a matura t ion—temperatu re based c lass i f icat ion s c h e m e based o n 1.0 n m peak m o r p h o l o g y parameters w o u l d b e in error. D i a g e n e t i c sub—fac ies are less c o m m o n l y d e l i n e a t e d us ing R 0 m a x criteria. Because of the ex t reme tempera tu re d e p e n d e n c e and cat ion i n d e p e n d e n c e of vitr inite maturat ion o n organ ic matter, a d iagenet ic sub—class i f i ca t ion s c h e m e d e f i n e d by R 0 m a x values appears to b e super ior . The present study, there fore , uses the classi f icat ion s c h e m e of F o s c o l o s ef al. (1970) to de f ine the d iagenet ic sub—fac ies at Strand F iord . As was m e n t i o n e d previously , the m e a n m a x i m u m re f lectance at the base of the s e c t i o n is approx imate ly 1.0%. Near the t o p of the s e c t i o n the R 0 m a x decreases t o a m i n i m u m " of app rox imate l y 0 .48%. These R 0 m a x brackets c o r r e s p o n d t o e o d i a g e n e s i s (i.e., w h e r e R 0 m a x <0 .5%) t o early m e s o d i a g e n e s i s (i.e., w h e r e R o m a x = 0 .5—1.5%). For compara t i ve p u r p o s e s the d iagenet ic stage d e f i n e d by the clay parameters (i.e., ill ite crystal l inity o f up to 0.4 A 2 0 ) c o r r e s p o n d to late m e s o — (i.e., R 0 m a x = 1.0—1.5%) to early t e l o — ( R 0 m a x > 1 . 5 % ) d iagenes is . A s was m e n t i o n e d earlier, b e c a u s e thermal d i sequ i l i b r i um w i th the coa ls exists the R 0 m a x values are b e l i e v e d t o b e sl ight ly re tarded . It, there fore , s e e m s reasonab le that the m e a s u r e d R 0 m a x values w o u l d c o r r e s p o n d t o a lower—than—true d i a g e n e t i c stage and that the clay parameters may, in this case, a p p r o a c h a m o r e accurate measure of the d iagenet ic stage. Consideration of Shifts in Clay Parameters with Depth A n e x a m i n a t i o n of f igures 24, 25 a n d 26 ind icate that a n u m b e r of p r o b l e m s exist regard ing clay d iagenes is parameters that must b e c o n s i d e r e d . These p r o b l e m s i nc lude : 1) W h y is there a decrease in the sharpness ratio and increase in illite crystall inity index b e l o w z o n e 4. (Such t rends are the o p p o s i t e t o w h a t is general ly e x p e c t e d w i t h increas ing depth ) . 2) H o w is the sharp dec rease in illite p r o p o r t i o n in the l/S m i x e d layers a c c o u n t e d for at the b o u n d a r y b e t w e e n z o n e s 3 and 4? B o t h of these q u e s t i o n s can be a n s w e r e d in part by c o n s i d e r i n g the ef fects of detr ital c lay var iat ion w i th d e p t h . The pr imary factors be l i eved to be r e s p o n s i b l e for p r o d u c i n g the o b s e r v e d shifts in clay d iagenes is parameters are h igher P ^ Q and P H Q in the z o n e 3 shales than in over ly ing units. Prev ious ly p r o p o s e d theor ies , s u c h as a shift f r o m d i o c t a h e d r a l smect i te to t r ioctahedra l s m e c t i t e b e t w e e n t w o units (Bust in , 1977) must b e d i s c o u n t e d in this case as an e x a m i n a t i o n of (060) peaks ind icates that t r i oc tahedra l 2:1 si l icates are absent f r o m the ent i re s e c t i o n . Late d iagenet ic d e c a r b o x y l a t i o n o f o r g a n i c matter is genera l ly a c c e p t e d t o increase the acidi ty of an e n v i r o n m e n t t h r o u g h the p r o d u c t i o n of C 0 2 . F o s c o l o s et al (1980), Hurst and Irwin (1982) a n d S r o d o n and Eberl (1984) suggest that illite r e s p o n d s to increas ing acidi ty by ' o p e n i n g ' its inter layer spaces . T h e result of ' o p e n i n g ' illite is that b o n d s b e t w e e n inter layer cat ions and tet rahedra l sheets are w e a k e n e d w h e r e b y inter layer K * may be lost o r s u b s t i t u d e d w i t h o t h e r cat ions. In o r d e r to preserve charge neutrality, e l ementa l rear rangement w i t h i n the t e t r a — and o c t a h e d r a l layers c o u l d favor the re t rograde c o n v e r s i o n of illite t o i l l i te—smect i te u n d e r suf f ic ient ly hydrated and s o d i u m — r i c h c o n d i t i o n s . A n increase in P. - . - . , C O 2 the re fo re , can p r o d u c e c h a n g e s in the illite crystal lattice w h i c h w i l l b e re f lected in i l l ite crystall inity, sharpness ratio and the p r o p o r t i o n of illite in l/S va lues g iven that the c a t i o n chemist ry is cor rect . The increase in kaol in i te p r o p o r t i o n s w i th in z o n e s 2 a n d 3 suppor ts the idea that the e n v i r o n m e n t was ac id ic and K + — p o o r as kaol in i te is k n o w n to be stable u n d e r l o w p H , l o w [K*7H + ] c o n d i t i o n s . A s e c o n d theory w h i c h may a c c o u n t fo r the o b s e r v e d shifts in clay pa ramete r t rends is the p r e s e n c e of a p o s s i b l e P u ~ di f ferent ial b e t w e e n z o n e s 3 n 2 U a n d 4. Stud ies by Eberl and H o w e r (1978) have s u g g e s t e d that s m e c t i t e wi l l resist i l l i t i zat ion u n d e r c o n d i t i o n s of e levated P . , ^ . D e n o y e r de S e g o n z a c (1970) also M 2 \ J n o t e s that u n d e r suf f ic ient ly hydrated c o n d i t i o n s smect i te w i l l resist b e i n g t r a n s f o r m e d to il l ite. L o w [K " / o t h e r cat ions ] , s u p p o r t e d by the pe rs i s tence o f kao l in i te t h r o u g h z o n e s 2 and 3, may also retard the i l l i t izat ion of smect i te . Consideration of Variations in Sample Mineralogy with Depth As was m e n t i o n e d prev iously , d u e to the c o i n c i d e n c e of clay b o u n d a r i e s and p a l e o - e n v i r o n m e n t s it is be l i eved that the t rends in bulk shale m ine ra logy represent t rends in detr ital m inera logy rather than the d iagenet ic p r o d u c t i o n of o n e clay at the e x p e n s e of another . C h e m i c a l m i c r o e n v i r o n m e n t s may, h o w e v e r , exist w h i c h p r o d u c e au th igenet ic variations in clays w i th in e a c h separate z o n e . L ikewise , int razonal t rends in minera logy w h i c h appear t o represent d i a g e n e t i c react ions w i t h d e p t h may b e n o t h i n g m o r e than c h a n g e s in p a l e o — e n v i r o n m e n t s u c h as d e e p e n i n g of the bas in , d iss ipat ion of f l o w energy and c o m p e t e n c e . A g o o d dea l of e v i d e n c e suggests that the ch lo r i te o c c u r r i n g t h r o u g h z o n e 4 is of detr ital rather than a u t h i g e n i c . o r ig in . First, au th igen ic ch lo r i te was no t d e t e c t e d in the z o n e 4 sands tones . G r a n t e d that the f lu id chemis t ry c o u l d have d i f fered s o m e w h a t b e t w e e n the s a n d s t o n e a n d adjacent shales, b o t h t h e a b s e n c e . of ch lo r i te f r o m , a n d p r e s e n c e of M g — p o o r / f r e e anker i te (see prev ious chapter ) in , the sands tones may suggest that the bulk f o r m a t i o n f lu id chemis ty was d e p l e t e d in M g . S e c o n d and th i rd , p rev ious ly r e p o r t e d d iagenet ic ch lo r i t i za t ion react ions are said t o o c c u r u n d e r c o n d i t i o n s o f h igher temperatu re and M g activity than o b s e r v e d at Strand F iord . For examp le , Bo les and Frank (1979) f o u n d , in a study of the W i l c o x G r o u p of s o u t h w e s t Texas, that the f o l l o w i n g ch lo r i t i za t ion react ion o c c u r r e d over a temperatu re range of 150—200°C vs the 54—100°C range at Strand F iord . 3 . 5 F e 2 + + 3 . 5 M g 2 + + 9 H 2 0 + 3 K a o = C h l o r i t e + 1 4 H + The M g 2 + and F e 2 * necessary for the c o n v e r s i o n of kaol in i te t o ch lo r i te was b e l i e v e d to b e d e r i v e d f r o m the i l l i t izat ion of smect i te . M a g n e s i u m c o n c e n t r a t i o n s in the Eureka S o u n d strata f r o m Strand Fiord are be l i eved to be t o o l o w to p r o m o t e the d i a g e n e t i c f o r m a t i o n of ch lo r i te as anker i tes f r o m the s e c t i o n are f o u n d to b e M g 2 + v o i d to ex t reme ly M g 2 + p o o r (i.e., < 5 % M g in F e — M g s o l u t i o n sites). A s e c o n d ch lo r i t i za t ion react ion w h i c h p r o d u c e s the o b s e r v e d t rends in clay minera logy t h r o u g h z o n e 4 is p r e s e n t e d by H o w e r et al (1976) w h e r e by s m e c t i t e is c o n v e r t e d t o i l l ite and ch lo r i te as f o l l o w s : s m e c t i t e + K + = illite + quartz + ch lor i te This r e a c t i o n , as w e l l , must b e d i s c o u n t e d as the p rev ious s e c t i o n m o d e l l e d that l o w K * activity m a y have c o n t r i b u t e d t o p r o d u c i n g the p r o b l e m s in clay d iagenes is parameters . A f inal factor w h i c h s u p p o r t s the detr ital or ig in of ch lo r i te is that the ch lo r i te is rest r ic ted to , and of cons tan t p r o p o r t i o n t h r o u g h , z o n e 4. The ch lor i te is also a s s o c i a t ed w i t h a lesser a m o u n t of kao l in i te than occu rs e l s e w h e r e t h r o u g h the s e c t i o n w h i c h m a y suggest a c h a n g e in e i ther s o u r c e r o c k o r p r o v e n a n c e f r o m h u m i d t o ar id o r tempera te c o n d i t i o n s (i.e., m in imal l each ing of the so i l , m o d e r a t e pH) . A d d i t o n a l kaol in i te , in this case , c o u l d c o m e f r o m n e o f o r m a t i o n in a an e n v i r o n m e n t of l o w [ K * ] and a h igh A l :S i ratio (Zen, 1959; Rex and Mart in , 1966). A n alternat ively h u m i d s o u r c e terrain c o u l d a lso p r o d u c e the o b s e r v e d t rends in ch lo r i te a n d kaol in i te t h r o u g h z o n e 4 if the ch lor i te s o u r c e terrain was c l o s e to the d e p o s i t i o n a l e n v i r o n m e n t w h e r e b y transport t i m e and d istance w o u l d be short . A l ternat ively , if t ransport d is tances w e r e greater and d e g r a d e d 2:1 s i l icated w e r e de l i ve red to a M g — e n r i c h e d e n v i r o n m e n t ch lor i te c o u l d still f o r m f r o m the aggradat ion o f M g 2 + by the d e g r a d e d 2:1 si l icates. A study by Perry and H o w e r (1970) f o u n d a t rend in m inera logy similar t o that t h r p u g h z o n e 4 in a w e l l f r o m the Gul f coas t that was in te rp re ted as re f lect ing only detrital m inera logy . Basically, 117. an increase in the ch lor i te a n d d iscrete illite c o n t e n t was f o u n d to c o r r e s p o n d to a c h a n g e in d e p o s i t i o n a l e n v i r o n m e n t f r o m m i d d l e and oute r ner i t ic t o o f fshore . S U M M A R Y A N D C O N C L U S I O N S General Summary The major c o n c l u s i o n s d r a w n f r o m the present study are as fo l l ows : 1) The of fset in the coa l i f icat ion gradient in the s tudy area is at t r ibuted pr imari ly t o the preferent ia l ho r i zon ta l m ig ra t ion of heated N a + — e n r i c h e d waters into p e r m e a b l e units (coal seams a n d sands tones ) f r o m strat igraphical ly adjacent d iapi rs . A d d i t i o n a l m i n o r c o n t r i b u t i o n s t o p r o d u c i n g the o b s e r v e d offset are t h o u g h t t o c o m e f r o m bulk thermal c o n d u c t i v i t y d i f fe rences b e t w e e n the l i tho log ies that c o n t a i n the o rgan ic matter . 2) L o w r 2 values f r o m the coa l i f icat ion grad ients are att r ibuted t o the cessat ion o f h igh heat f l o w f r o m t h e diapirs b e f o r e thermal equ i l i b r i um w i t h the organ ic matter w a s atta ined. This r e d u c t i o n in heat f l o w is thought to be assoc ia ted w i t h the u n r o o t i n g of diapirs w i t h thei r s o u r c e at d e p t h . 3) T h e p r e — t e c t o n i c th ickness of Eureka S o u n d , and poss ib ly Beafort , Strata is t h o u g h t t o lie b e t w e e n 5200 a n d 6800 m. L o w r 2 values f r o m the coa l i f i ca t ion grad ients sub ject these th ickness values t o a m o d e r a t e d e g r e e o f uncerta inty , h o w e v e r , these th icknesses are in relative a g r e e m e n t w i th p rev ious ly p r o p o s e d t e c t o n i c m o d e l s . 4) T i m e - t e m p e r a t u r e m o d e l l i n g of the coa l i f i ca t ion gradients suggest that a g e o t h e r m a l grad ient of 18.3°C/km is r e c o r d e d in the s t u d i e d strata. Temperatu res at the t o p of the s e c t i o n w e r e ca lcu la ted us ing m e t h o d s o f Lopat in (1971) and Barker (1983) t o be 45°C and 14°C, respect ive ly . M i d — s e c t i o n m a x i m u m . temperatu res of 75 °C a n d 83 °C , respect ive ly , w e r e ca lcu la ted us ing these same m e t h o d s . A g a i n , d u e to the l o w r 2 va lues f r o m the coa l i f i ca t ion gradients these ca lcu la ted temperatures o n l y serve as first a p p r o x i m a t i o n s o f actual temperatures . 5) Six pr inc ipa l au th igen ic phases w e r e d e t e c t e d in the s a n d s t o n e s f r o m the s t u d i e d s e c t i o n . These inc lude : d a w s o n i t e , anker i te , ca lc i te , s ider i te , kaol in i te and quartz o v e r g r o w t h s . A l s o p resent are a n u m b e r of accesso ry au th igen ic phases w h i c h i n c l u d e pyrite, F e O x , i l l ite, ruti le a n d s p h e n e . 6) T w o generat ions of quartz o v e r g r o w t h s are r e c o g n i z e d in the s t u d i e d sandstones . The first f o r m e d early in the d iagenet ic s e q u e n c e pr ior t o the initial p rec ip i ta t ion of ca lc i te . The s e c o n d f o r m e d after the d i s s o l u t i o n of the f ramework a luminos i l icates but pr ior t o the p rec ip i ta t ion of kao l in i te and d a w s o n i t e . 7) T w o generat ions of ca lc i te p rec ip i ta t ion are also r e c o g n i z e d . Initial calc i te p rec ip i ta t ion o c c u r r e d relatively early in the d iagenet ic s e q u e n c e after the p r e c i p i t a t i o n . of first gene ra t i on quartz o v e r g r o w t h s but p r io r t o the p rec ip i ta t ion of anker i te . S e c o n d gene ra t i on ca lc i te f o r m e d late in the d i a g e n e t i c cyc le (poss ib ly post tecton ica l ly ) pr ior to the p rec ip i ta t ion of kaol in i te and d a w s o n i t e but after the p rec ip i ta t ion of anker i te . 8) The p rec ip i ta t ion of d a w s o n i t e is s y n c h r o n o u s w i th the p rec ip i ta t ion of kaol in i te . B o t h minerals are t h o u g h t to p rec ip i ta te as the A l * 3 — o r g a n i c c o m p l e x e s r e s p o n s i b l e fo r the d i s s o l u t i o n of the a luminos i l icate eventual ly destab i l i ze and re lease free A l + 3 back in to s o l u t i o n ! The N a * necessary fo r the p rec ip i ta t ion of d a w s o n i t e is t h o u g h t to or ig inate f r o m the d i sso lu t i on of halite in adjacent diapirs. 9) The d i s t r i bu t ion of clay minerals w i t h d e p t h is be l i eved to ref lect pr imari ly detrital and c h e m i c a l var iat ions b e t w e e n l i thofacies rather than the d iagenet ic alterat ion of clay minerals . H o w e v e r , within the separate l i thofacies there is e v i d e n c e to s u p p o r t the d iagenet ic a l terat ion of i l l ite and i l l i te /smect i te m i x e d layers w i t h d e p t h . These a b o v e m e n t i o n e d c o n c l u s i o n s are u s e d in the f o l l o w i n g s e c t i o n to s u m m a r i z e the d iagenet ic and s e d i m e n t o l o g i c d e v e l o p e m e n t of the Eureka S o u n d Fo rmat ion at Strand F iord . D i s c u s s i o n D i a g e n e t i c analyses f r o m the p rev ious 3 chapters suggest that 6 separate b i o -and p h y s i o c h e m i c a l events are r e c o r d e d in . the Eureka S o u n d strata at Strand Fiord. T h e s e events i nc lude : 1) S u b a e r i a l W e a t h e r i n g — A l t h o u g h p o o r c o n t r o l is had o n the p a l e o g e o g r a p h y of the Eureka S o u n d Format ion s o u r c e area at Strand F iord it is be l i eved , d u e to the h igh pe rcentage of kaol in i te in the shales, that e r o s i o n of the s e d i m e n t s o u r c e o c c u r r e d u n d e r p r e d o m i n a n t l y h u m i d c o n d i t i o n s . As a result, the o n l y major clay types o t h e r than kaol in i te to be de l i ve red to the basin w o u l d have b e e n d e g r a d e d 2:1 and 2:1:1 si l icates. A p o s s i b l e e x c e p t i o n , h o w e v e r , is seen in z o n e 4 w h e r e the ch lor i te may be of detr ital or ig in if its t ransport d i s tance had b e e n relatively short and subaerial degradat ion min imal . 2) S u b a q u e o u s A g g r a d a t i o n a n d N e o f o r m a t i o n - Prior to the d e p o s i t i o n and burial of the d e g r a d e d clay minerals w i th in the di f ferent sed imentary env i ronments a n u m b e r o f mod i f i ca t i ons o c c u r r e d to these minerals w h i l e still in the wate r 121 c o l u m n and at the s e d i m e n t / w a t e r interface. First, in z o n e s 2, 3, and 5 aggredat ion of N a + , K + , and C a + 2 by t h e d e g r a d e d 2:1 si l icates o c c u r r e d to f o r m s m e c t i t e a n d illite in M g + 2 - p o o r , K + + N a + e n r i c h e d e n v i r o n m e n t s . S e c o n d , in z o n e 4 aggredat ion of M g + 2 by the d e g r a d e d 2:1:1 si l icates in a M g + 2 e n r i c h e d K + d e p l e t e d e n v i r o n m e n t lead t o t h e p r o d u c t i o n of ch lo r i te . Rapid f l o c c u l a t i o n a n d p o s s i b l e n e o f o r m a t i o n of kaol in i te a lso o c c u r r e d in z o n e 4 there was a h igh A l * 3 / S i * 4 ratio and l o w K + / H + ratio (Figure 28). 3) Sediment/Water Interface Reactions (Diagenesis A)- B o t h pyrite and sider i te f o r m e d d u r i n g d iagenes is A u n d e r near sur face c o n d i t i o n s w h e r e the Eh was relatively l o w ( < 0 . 3 5 v and F e * 2 activity relatively h igh . Pyrite and sider i te d id not f o r m synchronous ly , h o w e v e r , but rather the fo rmer gave way to the latter w i th d e p t h as sul f ide activity d e c r e a s e d a n d P. - . - . i nc reased o n pass ing f r o m the z o n e of. sulfate r e d u c t i o n to the z o n e o f m e t h a n o g e n e s i s . Eventually, as the c o n c e n t r a t i o n of Fe d e c l i n e d the prec ip i ta t ion of s ider i te c e a s e d . 4) Shallow Burial (Diagenesis B)- A s s e d i m e n t c o m p a c t i o n p r o g r e s s e d pressure so lu t i on resu l ted in the the early m o b i l i z a t i o n of si l ica and , in this case, the s u b s e q u e n t f o rmat ion of first genera t ion quar tz ove rg rowths . A l s o du r ing the early stages of s h a l l o w burial t he smect i te - i l l i te t rans format ion was still pr imari ly in the first stage of smect i te d e h y d r a t i o n w h e r e little or n o lattice rear rangement was o c c u r r i n g . A s a result very little, if any, F e * 2 was b e i n g l iberated by the illite in to the f o r m a t i o n waters at this t ime. First genera t ion ca lc i te w h i c h p rec ip i ta ted at this t i m e f o r m e d , there fore , under c o n d i t i o n s of r e d u c e d F e + 2 activity and elevated C 0 2 partial pressure. Subaqueous Aggradation and Neoformation Ul o z < z UJ > o CC Q. z E < 2 H u m i d / T r o p i c a l K a o l i n i t e , C h l o r i t e a n d d e g r a d e d 2:1:1 a n d 2:1 s i l i c a t e s F l o c c u l a t i o n a n d r a p i d d e p o s i t i o n o f K a o l i n i t e A g g r a d a t i o n o f N a , C a , a n d M g b y d e g r a d e d s i l i c a t e s K a o l i n i t e C h l o r i t e ( z o n e 4 o n l y ) D e g r a d e d l l l i t e S m e c t i t e C h l o r i t e ( z o n e 4) Figure 28- Summary d iagram o f early stage s u b a q u e o u s aggradat ion and n e o f o r m a t i o n o f clay minerals u n d e r h u m i d / t r o p i c a l s o u r c e c o n d i t i o n s . 5) Deep Burial (Diagenesis C)- D u r i n g the d e e p burial d iagenet ic stage, just pr ior to the o n s e t of the Eurekan O r o g e n y , the s t u d i e d strata w e r e bu r ied to a m a x i m u m d e p t h of b e t w e e n 5500 and 6800 m. Hydrostat ic pressures at this t ime w e r e c l o s e to 127 M P a at the base of the s e c t i o n w i th temperatu res of up to 95 °C. It was u n d e r these c o n d i t i o n s that p o r o s i t y e n h a n c e m e n t w i th in the sands tones b e g a n to o c c u r as i nc reased ca rboxy l i c ac id activity resu l ted in the d i s s o l u t i o n of the f ramework a luminos i l icates t h r o u g h o rgan ic c o m p l e x i n g w i th A l * 3 . S e c o n d genera t ion ca lc i te c e m e n t a t i o n a lso o c c u r r e d d u r i n g this stage in assoc ia t ion w i t h the f ramework a luminos i l icate d i sso lu t i on (Figure 29). Prior t o the d i s s o l u t i o n of the a luminos i l icates , h o w e v e r , anker i te p rec ip i ta ted at the e x p e n s e of the p rev ious generat ion carbonates in r e s p o n s e to increas ing F e * 2 assoc ia ted w i th the i l l i t izat ion of smect i te and c o n t i n u e d h igh C 0 2 partial pressures . W i t h i n the shales dur ing d iagenes is C , int ra -zonal var iat ions in f lu id chemis t ry a n d permeab i l i ty lead to the f o l l o w i n g p h e n o m e n a : a) Z o n e s 2 and 3- retardat ion of smect i te - i l l i te t rans format ion d u e t o e levated P.. and l o w [ K * / N a * 2 + C a + 2 ] , Poss ib le re t rograde c o n v e r s i o n of smect i te to n 2 U i l l ite d u e t o e levated P , ~ ~ and [ H * / K * ] . b) Z o n e s 4 a n d 5 - c o n v e r s i o n of s m e c t i t e t o illite d u e to l o w e r P than in H 2U the p rev ious stages. C o n v e r s i o n of p rev ious carbonates t o ankerite t h r o u g h the l iberat ion of F e * 2 in the smect i te - i l l i te t rans format ion . T o w a r d the e n d of d iagenes is C s e c o n d genera t ion quartz o v e r g r o w t h s f o r m e d as s i l ica c o n t i n u e d , to be re leased into so lu t i on t h r o u g h the progress ive i l l i t izat ion of s m e c t i t e in the assoc ia ted shales. 124 Deep Burial (Diagenesis C) UJ z o H CO Q Carboxylic acids - » -A I -* -A I - complex Dissolution of . framework aluminosilicates Calcite+Fe—Ankerite+Ca F i g u r e 29 - Summary d iagram o f d e e p burial d iagenet ic env i ronment . 6) SyiWpost Orogenic Reactions (Diagenesis D)- It is t h e s y n - a n d p o s t - o r o g e n i c d iagenet ic events that leave the m o s t p r o m i n e n t impr in t o n the many d iagenet ic parameters of the Eureka S o u n d Fo rmat ion at Strand F iord . U p unti l this po int , the thermal maturat ion of the strata had b e e n relatively un i f o rm a n d free f r o m c o m p l i c a t i o n s c reated by heat f l o w anomal ies . H o w e v e r , w i th the p r o g r e s s i o n of the Eurekan O r o g e n y and a s s o c i a t e d d iapi r m o b i l i z a t i o n d i a g e n e t i c c o n d i t i o n s w e r e c rea ted in the strata w h i c h a l tered the strata's relatively s imp le paragenet ic history. Heat f l o w a n o m o l i e s c r e a t e d by p rox im i ty of the strata t o the diapirs in the area p r o d u c e d a s igni f icant alterat ion o f the maturat ion s ignature o n the o rgan ic matter. N o t - o n l y d i d t h e c i rcu la t ion of the heated waters f r o m the diapir t e n d t o se lect ive ly mature that vitr inite in the s e q u e n c e w h i c h was assoc ia ted w i t h the m o s t p e r m e a b l e strata (i.e., the coa ls v .s . the phytoc lasts ) but the waters a lso left a m i n e r a l o g i c t race of thei r p r e s e n c e in the s a n d s t o n e s . D u e t o the water 's s o u r c e of o r ig in (i.e., the hal i te c o r e of the diapirs) they w e r e greatly e n r i c h e d in N a *. A l u m i n u m c o n c e n t r a t i o n s as w e l l b e g a n to increase as the organica l ly c o m p l e x e d A l + 3 p r o d u c e d dur ing the d e e p bur ial d iagenes is stage b e g a n to destab i l i ze w i th c h a n g i n g p H and l iberate A l * 3 back into s o l u t i o n . The net result was to create an e n v i r o n m e n t that was e n r i c h e d in b o t h N a + and A l + 3 u n d e r a suff ic ient ly h igh P _ _ t o favor the near s y n c h r o n o u s p rec ip i ta t ion of d a w s o n i t e and kaol in i te (Figure 30). Hydros ta t ic pressure du r ing d iagenes is D was l o w e r than dur ing d iagenes is C as upl i ft and e r o s i o n resu l t ing f r o m the Eurekan O r o g e n y t e n d e d to reduce the th ickness of the over ly ing strata. 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F., 1976, Pet rogenes is of m e t a m o r p h i c rocks : Fourth e d i t i o n , Spr inger -Ver lag , 334 P. 140 Z e n , E., 1959, C lay m inera l - ca rbonate re lat ions in sed imentary rocks : A m e r i c a n Journal of S c i e n c e , v. 257, p. 29 -43 . 141 A P P E N D I C E S P r e p a r a t i o n : K s a t u r a t e d S A M P L E 7 . 0 - 7 . 9 8 . 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - 1 0 . 9 1 1 . 0 - 1 1 . 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - • 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 R A K 9 - 2 5 7 . 1 9 - 1 0 . 1 0 - - 1 4 . 0 2 - -R A K 1 5 - 2 5 7 . 2 2 - 1 0 . 0 4 - - - - -R A K 2 0 - 2 5 7 . 2 5 - 1 0 . 1 0 - ' - - . - -R A K 2 3 - 2 5 7 . 1 9 - 1 0 . 4 6 - 1 2 . 9 9 - - -R A K 3 0 - 2 5 7 . 1 5 - 1 0 . 1 6 - - - - -R A K 3 3 - 2 5 7 . 1 7 - 1 0 . 1 0 - - 1 4 . 2 5 - -R A K 3 8 - 2 5 7 . 2 2 - 1 0 . 1 0 - - 14 . 2 5 - . -R A K 4 2 - 2 5 7 . 1 8 - 1 0 . 1 1 - - 1 4 . 2 5 - -R A K 4 3 - 2 5 7 . 2 2 - 1 0 . 1 0 - - 1 4 . 2 5 - -R A K 4 5 - 2 5 7 . 1 8 - 1 0 . 1 0 - - - - -R A K 4 6 - 2 5 7 . 2 2 - 1 0 . 1 0 - - 1 4 . 14 - . -R A K 5 0 - 2 5 7 . 2 2 - 1 0 . 1 0 - - 1 4 . 2 5 - -R A K 5 3 - 2 5 7 . 2 0 - 1 0 . 1 0 - - 14 . 2 5 - • -R A K 5 7 - 2 5 7 . 1 0 - 1 0 . 1 0 - - 14 . 2 5 - -R A K 6 0 - 2 5 7 . 1 9 - 1 0 . 1 0 - - 1 4 . 4 8 - -R A K 6 7 - 2 5 7 . 1 9 - 1 0 . 1 0 - - - - -R A K 6 8 - 2 5 7 . 2 2 - 1 0 . 5 2 - '- - - -R A K 7 1 - 2 5 7 . 2 2 - 1 0 . 16 - -. - - -R A K 7 6 - 2 5 7 . 1 9 - 1 0 . 1 0 11 . 0 5 - - - -R A K 7 8 - 2 5 7 . 2 2 1 0 . 1 0 - • - -• - -R A K 1 1 2 - 2 5 7 . 0 5 9 . 5 0 - - - -R A K 1 2 5 - 2 5 7 . 1 9 - 1 0 . 1 0 - - - -P r e p a r a t i o n : K s a t u r a t e d + e t h y l e n e g l y c o l S A M P L E 7 . . 0 - • 7 . 9 8 . 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - 1 0 . 9 11 0 1 1 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 R A K 9 - 2 5 7 . 2 2 - 1 0 . 1 0 - - - - - -R A K 1 5 - 2 5 7 . 2 2 - 1 0 . 0 4 - - - -R A K 2 0 - 2 5 7 . 2 5 - 1 0 . 16 - - - - 1 5 . 3 6 -R A K 2 3 - 2 5 7 . 2 5 - 1 0 . 2 2 - - - 1 4 . 2 5 - - • R A K 3 0 - 2 5 7 . 1 9 - 1 0 . 16 - - - - - . -R A K 3 3 - 2 5 7 . 1 7 - 1 0 . 1 0 - - - 1 4 . 2 5 _ -R A K 3 8 - 2 5 7 . 2 2 - 1 0 . 1 0 - - - 1 4 . 2 5 - -R A K 4 2 - 2 5 7 . 1 9 - 1 0 . 1 0 - - - 1 4 . 2 5 - -R A K 4 3 - 2 5 7 . 2 2 - 1 0 . 1 0 - - - 1 4 . 2 5 - -R A K 4 5 - 2 5 7 . 1 9 - 1 0 . 1 0 - - - 1 4 . 2 6 - • -R A K 4 6 - 2 5 7 . 2 2 - 1 0 . 1 0 - - 1 4 . 2 5 - -R A K 5 0 - 2 5 7 . 2 2 1 0 . 1 0 - - - 1 4 . 4 8 - ' -R A K 5 3 - 2 5 7 . 1 0 - 1 0 . 1 0 - - 1 4 . 4 8 - • -R A K 5 7 - 2 5 7 . 2 2 - 1 0 . 11 - - - 1 4 . 3 7 - -R A K 6 0 - 2 5 7 . 2 0 - 1 0 . 1 0 - - - 1 4 . 2 5 - -R A K 6 7 - 2 5 7 . 2 5 1 0 . 11 - - _ _ -R A K 6 8 - 2 5 7 . 2 0 - 1 0 . 1 0 1 1 . 4 0 - - -R A K 7 1 - 2 5 7 . 2 8 - 1 0 . 16 - - - 1 4 . 4 8 - -R A K 7 6 - 2 5 7 . 2 0 - 1 0 . 1 0 - - - _ _ -R A K 7 8 - 2 5 7 . 1 9 - 1 0 . 1 0 - - _ _ R A K 1 1 2 - 2 5 7 . 0 5 - , 1 0 . 1 0 - _ - -R A K 1 2 5 - 2 5 7 . 2 5 - 1 0 . 1 0 - " - - - -•v o ft> (/> c' > 3 T 3 T 3 UI (D 01 3 c g. —1 x ' ST —k C L n ft) -< P r e p a r a t i o n : M g s a t u r a t e d S A M P L E 7 . 0 - 7 . 9 8 . 0 - 8 . 9 9 : 0 - 9 . 9 1 0 . 0 - 1 0 . 9 1 1 . 0 - 1 1 . 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 1 7 . 0 - 1 7 R A K 9 - 2 5 7 . 1 9 - - 1 0 1 1 11 . 6 3 - - 1 4 . 2 5 - - -R A K 1 5 - 2 5 7 . 1 9 - - 1 0 . 1 0 - 1 2 . 6 2 - 1 4 . 2 5 - - -R A K 2 0 - 2 5 7 . 2 5 - - 1 0 . 3 4 - - - 1 4 . 7 2 - - -R A K 2 3 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 3 0 - 2 5 7 . 1 9 - - 1 0 . 1 6 - - - 1 4 . 7 2 - - -R A K 3 3 - 2 5 7 . 1 9 - - 10 1 0 - - - 1 4 . 2 5 - - -R A K 3 8 - 2 5 7 . 2 2 - - 1 0 . 1 0 - . - - 1 4 . 2 5 - - -R A K 4 2 - 2 5 7 . 1 9 - - 1 0 . 1 0 - 1 2 . 8 1 - 1 4 . 2 5 - - -R A K 4 3 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 4 5 - 2 5 7 . 2 1 - - 1 0 . 1 0 - 1 2 . 2 7 - 1 4 . 2 5 - - -R A K 4 6 - 2 5 7 . 2 2 - - 1 1 . 7 8 - - 1 4 . 7 3 - - -R A K 5 0 - 2 5 7 . 1 9 - - 1 0 . 1 0 11 . 0 5 1 2 . 6 2 - 1 4 . 4 8 - - - ' R A K 5 3 - 2 5 7 . 2 0 - - 1 0 . 1 0 11 . 7 8 - 1 4 . 4 8 - - -R A K 5 7 - 2 5 7 . 1 9 - - 1 0 . 11 - - 1 4 . 3 7 - - -R A K 6 0 - 2 5 7 . 2 0 - - 1 0 . 1 0 - 1 2 . 2 7 • 1 4 . 2 5 - - -R A K 6 7 - 2 5 7 . 1 9 - - 1 0 . 1 0 11 . 9 4 1 2 . 8 0 - 1 4 . 7 2 - • - -R A K 6 8 - 2 5 7 . 2 0 - - . 1 0 1 0 11 . 7 8 1 4 . 7 2 - - . -R A K 7 1 - 2 5 7 . 1 9 - - 1 0 . 1 0 • 1 2 . 2 7 - 1 4 . 2 5 - - -R A K 7 6 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 7 8 - 2 5 7 . 2 0 - - 1 0 . 0 4 1 1 . 7 8 - - t 4 . 2 5 - - -R A K 1 1 2 - 2 5 - - - - r - • . - - - -R A K 1 2 5 - 2 5 7 . 2 2 - - 1 0 . 1 0 ' • - 1 2 . 6 2 - 1 4 . 9 7 - - -P r e p a r a t i o n : M g s a t u r a t e d + e t h y l e n e g l y c o l S A M P L E 7 . 0 - 7 . 9 8 . 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - - 1 0 . 9 1 1 . 0 - 1 1 . 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 1 7 . 0 - 1 7 . R A K 9 - 2 5 7 . 1 9 - 9 . 4 0 1 0 0 4 - - - 1 4 . 7 2 • - - -R A K 1 5 - 2 5 7 . 2 2 - - 1 0 0 4 - - . - 1 5 . 2 3 1 6 . 3 6 1 7 . 6 7 R A K 2 0 - 2 5 7 . 2 5 - - 1 0 2 8 - . - - 1 6 . 9 9 1 7 . 6 7 R A K 2 3 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 3 0 - 2 5 7 . . 2 0 - - 1 0 . 1 9 - - - 1 5 . 3 6 1 6 . 9 9 -R A K 3 3 - 2 5 7 . 2 0 - - 1 0 1 6 - - 14 . 6 0 - 1 6 . 8 3 -R A K 3 8 - 2 5 7 . 2 2 - - 1 0 . 1 0 - - - 1 4 . 2 5 - - -R A K 4 2 - 2 5 7 1 9 - - 1 0 0 4 - - - 1 4 . 2 5 1 5 . 7 8 - -R A K 4 3 - 2 5 - - - - -R A K 4 5 - 2 5 7 . . 1 9 - - 1 0 . 1 0 - • - , - 1 4 . 2 2 - - -R A K 4 6 - 2 5 7 2 3 - - 1 0 11 - - 1 4 . 4 8 1 6 . 9 9 -R A K 5 0 - 2 5 7 . 1 0 - - 1 0 1 0 - - - 1 4 . 4 8 - 1 6 . 0 6 -R A K 5 3 - 2 5 7 . 1 9 - - 1 0 1 0 - - - 1 4 . 1 4 - - 1 7 . 6 7 R A K 5 7 - 2 5 7 . 2 2 - - 1 0 1 0 - - . 1 4 4 8 - - -R A K 6 0 - 2 5 7 . . 1 9 - - 1 0 . 1 1 - - - 1 4 . 7 2 - 1 6 . 9 9 -R A K 6 7 - 2 5 7 . . 1 0 • - - 1 0 1 0 - . - - 1 4 . 7 2 - , 1 6 . 0 9 -R A K 6 8 - 2 5 7 . 2 2 - - 1 0 . . 1 0 - - - 1 4 7 2 1 5 . 2 3 1 6 . 9 9 -R A K 7 1 - 2 5 7 . 2 2 - - 1 0 1 0 - - 1 4 2 5 - - 1 7 . 3 2 R A K 7 6 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 7 8 - 2 5 7 . . 2 0 - - 1 0 0 4 - 1 2 . 2 7 - 1 4 . 2 5 - 1 6 . 9 9 -R A K 1 1 2 - 2 5 - - - - -• - - -R A K 1 2 5 - 2 5 7 . . 1 8 - - 1 0 1 0 - - - - 1 6 . 9 9 -P r e p a r a t i o n : N o n - c a t i o n s a t u r a t e d S A M P L E 7 . 0 - 7 . 9 8 . 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - 1 0 . 9 1 1 . 0 - 1 1 : 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 1 7 . 0 - 1 7 . 9 R A K 9 - 2 5 7 . 1 9 8 . 8 4 10 . 16 - - 14 . 14 - - -R A K 1 5 - 2 5 - 10 . 2 8 11 . 7 8 - - - - -R A K 2 0 - 2 5 7 . 1 9 10 . 10 - - 14 . 4 8 - - -R A K 2 3 - 2 5 7 . 1 9 - - 10 . 16 - - 14 . 7 2 - - ' -R A K 3 0 - 2 5 7 . 1 9 - • - 10 . 16 - - 14 . 14 - - -R A K 3 3 - 2 5 7 . 1 0 10 . 10 - - 14 . 4 8 - -R A K 3 8 - 2 5 7 . 1 9 - - 10 . 10 - - 14 . 2 5 . - - -R A K 4 2 - 2 5 7 . 2 2 10 . 10 - - 14 . 2 5 - • - -R A K 4 3 - 2 5 7 . 2 5 10 . 11 - - 14 . 2 5 - - -R A K 4 5 - 2 5 7 . 1 9 10 . 0 4 - - 14 - 2 7 - - -R A K 4 6 - 2 5 7 . 2 2 10 . 11 - - 14 . 14 - - -R A K 5 0 - 2 5 7 . 1 9 10 . 10 - - 14 . 4 8 - - -R A K 5 3 - 2 5 7 . 2 0 10 . 10 - 14 . 4 8 - - -R A K 5 7 - 2 5 7 .15 10 . 10 - - 14 . 3 7 - - -R A K 6 0 - 2 5 7 . 1 9 10 . 10 - - 14 . 2 5 - - -R A K 6 7 - 2 5 7 .20 - 9 . 6 0 10 . 10 - - - - . - -R A K 6 8 - 2 5 7 .20 10 . 10 11 . 33 - - - - -R A K 7 1 -25 7 . 2 0 10 . 1 0 - 12 . 27 14 . 2 5 - - -R A K 7 6 - 2 5 7 . 2 0 10 . 11 - - - • - -R A K 7 8 - 2 5 7 . 2 2 - - 10 . 10 11 . 7 8 - - - - -R A K 1 1 2 - 2 5 - - - - - -R A K 1 2 5 - 2 5 7 . 2 0 to . 10 - - - - -P r e p a r a t i o n : N o n - c a t i o n s a t u r a t e d • e t h y l e n e g l y c o l S A M P L E 7 . 0 ^ 7 . 9 8 . 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - 1 0 . 9 1 1 . 0 - 1 1 . 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 1 7 . 0 - 1 7 . 9 R A K 9 - 2 5 7 . 16 - 10. 0 4 - - - - -R A K 1 5 - 2 5 7 . 2 2 10. 0 4 1 1 . 0 5 - 14 . 4 8 - - -R A K 2 0 - 2 5 7 . 19 - 10. 10 - 14 . 7 2 - 1 6 . 8 3 - • R A K 2 3 - 2 5 7 . 22 - - 10. 10 - 1 4 . 7 2 - 1 6 . 0 6 -R A K 3 0 - 2 5 7 . 19 - 10. 16 - 1 4 . 0 2 1 5 . 5 0 -R A K 3 3 - 2 5 7 . 10 - . - 10. 0 4 - 1 4 . 2 5 - - -R A K 3 8 - 2 5 7 . 11 10. 1 1 - 1 4 . 2 4 - - -R A K 4 2 - 2 5 7 . 2 2 1 0 . 1 1 1 1 . 4 8 - 1 4 . 2 5 • - - -R A K 4 3 - 2 5 7 . 19 - 1 0 . 10 - - 1 4 . 2 5 - - -R A K 4 5 - 2 5 7 . 19 1 0 . 10 - - 1 4 . 2 5 - -R A K 4 6 - 2 5 7 . 2 2 - 1 0 . 0 9 - - 1 4 . 14 - - -R A K 5 0 - 2 5 7 . 10 1 0 . 1 1 - - 14 . 4 8 - - -R A K 5 3 - 2 5 7 . 2 0 1 0 . 10 - - 1 4 . 4 8 - - -R A K 5 7 - 2 5 7 . 15 - - 1 0 . 10 - . - 1 4 . 2 5 - - •-R A K 6 0 - 2 5 7 . 2 0 - 1 0 . 10 - 1 4 . 4 8 - - -R A K 6 7 - 2 5 7 . 2 0 - 1 0 . 11 1 3 . 19 1 4 . 7 2 - - -R A K 6 8 - 2 5 7 . 2 2 - 1 0 . 10 - 1 2 . 27 - - - - -R A K 7 1 - 2 5 7 . 2 0 - 1 0 . 10 - - - - - 1 6 . 9 9 -R A K 7 6 - 2 5 7 . 2 5 - 1 0 . 10 - - - - - 1 6 . 3 6 -R A K 7 8 - 2 5 7 . 2 2 - i o . ' 0 - 12 . 8 0 - - - - ' -R A K 1 1 2 - 2 5 - - - - - - _ _ - -R A K 1 2 5 - 2 5 7 . 2 0 - - 1 0 . 10 • - - - - - - -z o •? > cr TJ C fD 3 2 2.* •< .U P r e p a r a t i o n : K s a t u r a t e d + 5 0 0 d e g r e e s C f o r t w o h o u r s S A M P L E 7 . 0 - 7 . 9 8 . . 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - 1 0 . 9 11 . 0 - 1 1 . 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 1 7 . 0 - 1 7 . 9 R A K 9 - 2 5 - - 1 0 . 1 1 - - - 1 4 . 14 - - -R A K 1 5 - 2 5 - - - 1 0 . 0 4 - - - - - -R A K 2 0 - 2 5 - - - 1 0 . 1 6 - - - - -R A K 2 3 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n/s R A K 3 0 - 2 5 - - 1 0 . 1 6 - - - - - - ~ R A K 3 3 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 3 8 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s n / s R A K 4 2 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 2 5 - - -R A K 4 3 - 2 5 n / s n / s n / s n / s n / s n / s n / s n / s n / s . n / s n / s R A K 4 5 - 2 5 - - - 1 0 . 1 0 - ' - - 1 4 . 2 5 - - -R A K 4 6 - 2 5 - ' - - 1 0 . 1 0 - - '. - 1 4 . 1 5 - - -R A K 5 0 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 4 8 - -R A K 5 3 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 4 8 - - -R A K 5 7 - 2 5 n / s n / s n / s n/s n / s n / s n / s n / s n / s n / s n / s R A K 6 0 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 2 5 - • - -R A K 6 7 - 2 5 n/s n/s n / s n/s n / s n/s n / s n / s n / s n / s n / s R A K 6 8 - 2 5 n/s n / s n / s n/s n / s n / s n / s n / s n / s n / s n / s R A K 7 1 - 2 5 n/s n / s n / s n/s n/s n / s n / s n / s n / s n / s n / s R A K 7 6 - 2 5 n / s n / s n / s n/s n / s n/s n / s n / s n / s n / s n / s R A K 7 8 - 2 5 n / s n / s n / s n / s n / s n / s n / s h / s n / s n / s n / s R A K 1 1 2 - 2 5 - - - 1 0 . 1 0 - - - - - - -R A K 1 2 5 - 2 5 - - -" • P r e p a r a t i o n : K s a t u r a t e d + e t h y l e n e g l y c o l + 5 0 0 d e g r e e s C f o r t w o h o u r s S A M P L E 7 . 0 - 7 . 9 8 0 - 8 . 9 9 . 0 - 9 . 9 1 0 . 0 - 1 0 . 9 11 . 0 - 1 1 . 9 1 2 . 0 - 1 2 . 9 1 3 . 0 - 1 3 . 9 1 4 . 0 - 1 4 . 9 1 5 . 0 - 1 5 . 9 1 6 . 0 - 1 6 . 9 1 7 . 0 - 1 7 . 9 R A K 9 - 2 5 7 . 2 2 - - 1 0 . 1 0 - - - _ _ R A K 1 5 - 2 5 T ' - - 1 0 . 0 4 - - - _ _ _ R A K 2 0 - 2 5 - - 9 . 9 9 - - - • _ _ _ _ R A K 2 3 - 2 5 - - ' - 1 0 0 4 - - - _ _ _ R A K 3 0 - 2 5 n/s n/s n/s n/s n/s n / s n / s n / s n / s n/s n/s R A K 3 3 - 2 5 - - 1 0 . 1 0 - - 1 4 ' . 0 2 - _ R A K 3 8 - 2 5 7 . 2 1 - - - - - - 1 4 . 2 4 _ R A K 4 2 - 2 5 - - - 1 0 1 0 - - 1 4 . 2 5 -R A K 4 3 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 2 5 _ _ R A K 4 5 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 2 5 _ _ R A K 4 6 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 1 4 _ _ _ R A K 5 0 - 2 5 n / s n / s n/s n / s n / s n / s n / s n / s n / s n/s n/s R A K 5 3 - 2 5 - - - 1 0 . 1 0 r • - - . 1 4 . 4 8 _ - _ R A K 5 7 - 2 5 - - - 1 0 . 12 - - - 1 4 . 4 8 _ _ _ R A K 6 0 - 2 5 - - - 1 0 . 1 0 - - - 1 4 . 2 8 _ R A K 6 7 - 2 5 - . - - 1 0 . 1 0 - - _ _ R A K 6 8 - 2 5 - - - 1 0 . 1 0 - - _ _ _ _ _ R A K 7 1 - 2 5 - - - 1 0 . 1 0 _ _ _ R A K 7 6 - 2 5 - • - - 1 0 . 1 0 _ _ _ _ R A K 7 8 - 2 5 - - - 1 0 . 1 0 _ - _ _ _ R A K 1 1 2 - 2 5 - - - 1 0 1 0 - _ _ _ _ R A K 1 2 5 - 2 5 - - • - 1 0 . 1 0 - - - - - -

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