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Compositional variations in diagenetic chlorites and illites, and relationships with formation-water chemistry

Published online by Cambridge University Press:  09 July 2018

J. S. Jahren  and
P. Aagaard
J. S. Jahren
Affiliation:
Department of Geology, University of Oslo, PO Box 1047, Blindern, N-0316 Oslo 3, Norway
P. Aagaard
Affiliation:
Department of Geology, University of Oslo, PO Box 1047, Blindern, N-0316 Oslo 3, Norway
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Abstract

Authigenic illites and chlorites from clastic reservoirs, offshore Norway, have been studied by analytical transmission electron microscopy (ATEM). Present-day reservoir conditions range from 1600 m burial depth and 70°C to 4400 m and 160°C. The reservoir units have experienced continuous subsidence since early Cretaceous, and are presently at maximum burial. Textural and morphological evidence indicates that the authigenic illites and chlorites investigated are late diagenetic products, except for an early-formed berthierine in the shallowest reservoir. While the illites show very limited chemical variability at temperatures between 140° and 160°C the chlorites exhibit definite compositional trends with increasing temperatures. Tetrahedral Al increases substantially from 100°–160°C, and the octahedral vacancy decreases correspondingly. These observations indicate that continuous recrystallization of authigenic clays has taken place. This is also supported by the chemical composition of present-day porewaters, which are close to equilibrium with the clay mineral assemblage.

Type
Research Article
Information
Clay Minerals , Volume 24 , Issue 2 , June 1989 , pp. 157 - 170
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1989

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References

Aagaard, P. & Helgeson, H.C. (1983) Activity/composition relations among silicates and aqueous solutions: II, Chemical and thermodynamic consequences of ideal mixing of atoms on homological sites in mont- morillonites, illites, and mixed-layer clays. Clays Clay Miner, 31, 207–217.CrossRefGoogle Scholar
Bjorlykke, K., Aagaard, P., Dypvik, H., Hastings, D.S. & Harper, A.S. (1986) Diagenesis and reservoir properties of Jurassic sandstones from the Haltenbanken area, offshore mid Norway. Pp. 275–286 in: Habitats of Hydrocarbons on the Norwegian Continental Shelf (Spencer, A. M. et al., editors). Norwegian Petroleum Society and Graham & Trotman, London.Google Scholar
Cathelineau, M. & Nivea, D. (1985) A chlorite solid solution geothermometer. The Los Azurfres (Mexico) geothermal system. Cont. Mineral Petrol. 91, 235–244.Google Scholar
Cliff, G. & Lorimer, G.W. (1975) The quantitative analysis of thin specimens. J. Microsc. 103, 203–207.Google Scholar
Curtis, C.D., Hughes, C.R., Whiteman, J.A. & Whittle, C.K. (1985) Compositional variations within some sedimentary chlorites and some comments on their origin. Mineral. Mag. 49, 375–386.CrossRefGoogle Scholar
Egeberg, P.K. & Aagaard, P. (1989) Formation water chemistry in relation to the stability of detrital and authigenic minerals in clastic reservoirs from offshore Norway. J. Sed. Petr, (in press).Google Scholar
Hayes, J.B. (1970) Polytypism of chlorite in sedimentary rocks. Clays Clay Miner. 18, 285–306.CrossRefGoogle Scholar
Helgeson, H.C., Delany, J.M., Nesbitt, H.W. & Bird, D.K. (1978) Summary and critique of the thermodynamic properties of rock forming minerals. Am. J. Sci. 267, 729–804.Google Scholar
Helgeson, H.C., Kirkham, D.H. & Flowers, G.C. (1981) Theoretical predictions of the behavior of aqueous electrolytes at high pressures and temperatures IV. Calculations of activity coefficients, osmotic coefficients and apparent molal and standard and relative partial molal properties to 600 °C and 5 Kb. Am. J. Sci. 281, 1249–1516.Google Scholar
Helgeson, H.C. & Aagaard, P. (1985) Activity/composition relations among silicates an aqueous solutions. I. Thennodynainics of intrasite mixing and substitutional order/disorder in minerals. Am. J. Sci. 285, 769–844.Google Scholar
McDowell, D.S. & Elders, W.A. (1980) Authigenic layer silicate minerals in borehole Elmore 1, Salton Sea Geothermal field, California, USA. Cont. Mineral. Petrol, 74, 293–310.CrossRefGoogle Scholar
Ransom, B. & Helgeson, H.C. (1988) Hydration states and 3-dimensional order: A new theory of the constitution of mixed-layer clays. Terra Cogrtita, 8, 174.Google Scholar
Srodon, J. & Eberl, D.D. (1984) Illite. Pp. 495–544 in: Micas (Bailey, S. W., editor). Mineralogical Society of America, Reviews in Mineralogy 13.CrossRefGoogle Scholar
Stoesseix, R.K. (1979) A regular solution site-mixing model for illites. 43, 1151–1159.Google Scholar
Stoessell, R.K. (1981) Refinements in a site-mixing model for illites: local electrostatic balance and the quasichemical approximation. Geochim. Cosmoschin. 45, 1733-1741.Google Scholar
Stoessell, R.K. (1984) Regular solution site-mixing model for chlorites. Clays. Clay Miner. 32, 205–212.Google Scholar
Tardy, Y. & Fritz, B. (1981) An ideal solid-solution model for calculating solubility of clay minerals. Clay Miner. 16, 361–373.CrossRefGoogle Scholar
Veblen, D.R. (1983) Microstructures and mixed layering in intergrown wonesite, chlorite, talc, biotite, and kaolinite. Am. Miner. 68, 566–580.Google Scholar
Velde, B. (1985) Clay Minerals: a Physico-Chemical Explanation of their Occurrence. Elsevier, Amsterdam & New York.Google Scholar
Velde, B. & Medhioub, M. (1988) Approach to chemical equilibrium in diagenetic chlorites. Cont. Mineral. Petrol. 98, 122–127.CrossRefGoogle Scholar