Banks, D. A.

Yardley, B. W. D.

English

Yardley B. W. D.

Banks D. A.

University of Szeged

Acta Mineralogica-Petrographica, Abstract Series 2, Szeged, 2003 INTERPRETING THE CHEMICAL COMPOSITION OF FLUID INCLUSIONS: THE CONNECTION TO BULK WATER ANALYSES Y A R D L E Y . B. W. D. ' , BANKS, D. A.1 1 School of Earth Sciences, University of Leeds, Leeds LS2 9JT, UK. E-mail: B.Yardley@earth. leeds.ac.uk Analyses of the cation and anion concentrations in fluid inclusions have become relatively widespread in the literature, and greatly extend the range of crustal environments for which the fluid chemistry is known. W e have compiled a da tabase of both saline fluid inclusion analyses, ranging f rom low-grade metamorphic to magmatic systems, and bulk fluid analyses f r o m oilfield and geothermal drilling. Many chemical trends are similar for both data sets. For example, suites of high-T (magmat ic) fluid inclusion analyses (obtained by both single inclusion and bulk crush-leach techniques) show similar relationships between transition metal concentrations and chloride to oilfield brines, indicating similar speciation despite very different temperatures and absolute metal levels (Figure 1). 100000 E Q. Q. N 10000 1000 --1 0 0 1 0 - -0.1 0.01 10000 o • o -o o " - / - — 1 o • • w * 100000 CI (ppm) • Mole Granite (Audetat et al., 2000) O o Offshore Louisiana brines (Land et al. 1988) Cornwall (BottrellS Yardley 1988, Smith et al 1996) Alberta Basin Brines (Connolly et al. 1990) • ZnCI4-- slope • ZnCI2o slope 1000000 Figure 1: Relationship between CI for fluids f rom 2 contrasting settings. Circles, oilfield brines, d iamonds , magmat ic fluid inclusions. Transition metals vary in concentration systematically with temperature as well as salinity, and these trends also are continuous f rom low-T oilfields through metamorphic fluid inclusions, geothermal brines and magmat ic f luid inclusions. (Figure 2). W e conclude f rom these results firstly that the analytical techniques applied to fluid inclusions today are suff ic ient ly robust to yield reliable results at a useful level for interpretation. However the consistent trends over such a wide range of crustal conditions are themselves a remarkable demonstration of the relatively narrow range of chemical envi ronments in the crust. Common rock assemblages must limit f02, pH and a H 2 S within rather narrow limits for salinity and temperature to emerge as such dominant controls on metal levels in fluids. 228 Acta Mineralogica-Petrographica, Abstract Series 2, Szeged, 2003 - 1 . 5 - 2 . 5 t - 3 . 5 "5 r o E g) -4 .5 -5 .5 -6 .5 4 O t 2 - »93 Q D O o o o • Shield Brines (Fritz & Frape, 1987; Moller et al. 1997)) • Mole Granite (Audetat et al., 2000) A Pyrenees (McCaig et al. 2000) A Columbian Emerald deposits (Banks et al. 2000) o Capitan Ruton (New Mexico) (Campbell et al 1995) O Salton Sea geothermal brines (Williams et al. 1988) A Variscides (SW Ireland) (Meere et al 1997) A ModumComplex (Norway) (Munz etal 1995) o Cornwall (BoftrellS Yardley 1988, Smith et al 1996) o Central Mssissippi brines (Carpenter et al. 1974) • Offshore Louisiana brines (Land et al. 1988) o Alberta Basin Brines (Connolly et al. 1990) X Alston Block Pb Ores (Banks, unpub) • Industrialnoe Tin Deposit ( Kamenetsky et al. 2002) - + - « " • x u • 0 . 0 0 0 5 0 . 0 0 1 0 . 0 0 1 5 0 . 0 0 2 0 . 0 0 2 5 1 / T ( K ) 0 . 0 0 3 0 . 0 0 3 5 0 . 0 0 4 F igu re 2 : Re la t i onsh ip b e t w e e n Zn/Cl of o i l f ie ld and geo the rmal br ines , and f lu id inc lus ions , p lot ted aga ins t m e a s u r e d or e s t ima ted t e m p e r a t u r e of the f luid ( t r app ing T fo r inc lus ions) . Squa re s - shield br ines , c i rc les - o i l f ie ld br ines , t r iangles -m e t a m o r p h i c f lu id inc lus ions , d i a m o n d s - m a g m a t i c f lu id inc lus ions and geo the rma l b r ines R e f e r e n c e s AUDETAT, A. , GUNTER, D. & HEIRRICH, C . A. ( 2 0 0 0 ) : C a u s e s for la rge-sca le metal zona t i on a round minera l i sed p lu tons : F lu id inc lus ion L A - I C P - M S e v i d e n c e f r o m the M o l e grani te , Aust ra l ia . E c o n o m i c G e o l o g y , 95 , 1563-1581 . BANKS, D . A. , GUILIANI, G . , YARDLEY, B. W . D. & CHEILLETZ, A. (2000) : E m e r a l d minera l i sa t ion in C o l u m b i a : F lu id c h e m i s t r y and the ro le of b r ine mixing. M i n e r a l i u m Depos i t a , 35 , 699 -713 . BOTRELL, S. H. & YARDLEY, B. W . D. (1988) : T h e c o m p o s i t i o n of a p r imary g ran i t e -de r ived o r e f lu id f r o m S W E n g l a n d , d e t e r m i n e d b y fluid inc lus ion analysis . 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(2002) : E x t r e m e chemica l he te rogene i ty of g ran i te -der ived hyd ro the rma l fluids: an e x a m p l e f r o m inc lus ions in a s ingle crysta l of miaro l i t i c quar tz . G e o l o g y , 30 , 4 5 9 - 4 6 2 . LAND, L. S. , MCPHERSON, G. L . & MACK, L. E. (1988) : T h e g e o c h e m i s t r y of sa l ine f o r m a t i o n waters , M i o c e n e o f f s h o r e Lou i s i ana . Gul f C o a s t Assoc ia t ion of Geo log i s t s T ransac t ions , 38 , 503 -511 . McCAlG, A. M . , TRITLLA, J. & BANKS, D . A. (2000) : F lu id mix ing and recyc l ing du r ing P y r e n e a n thrus t ing: e v i d e n c e f r o m F lu id inc lus ion h a l o g e n ra t ios . G e o c h i m i c a et C o s m o c h i m i c a Acta , 64 , 3 3 9 5 - 3 4 1 2 . MEERE, P. A. & BANKS, D . A. (1997) : U p p e r crus ta l f lu id migra t ion: an e x a m p l e f r o m the Var i sc ides of S W Ire land. Journa l of the Geo log ica l Soc ie ty , L o n d o n , 154, 9 7 5 - 9 8 5 . MUNZ, I. A. , YARDLEY, B. W . 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Interpreting the chemical composition of fluid inclusions : the connection to bulk water analyses

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Interpreting the chemical composition of fluid inclusions: : The connection to bulk water analyses

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