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Pressure-Temperature-Composition of Illite/Smectite Mixed-Layer Minerals: Niger Delta Mudstones and other Examples

Published online by Cambridge University Press:  02 April 2024

B. Velde ,
T. Suzuki  and
E. Nicot
B. Velde
Affiliation:
Laboratoire de Géologie, ER 224 CNRS, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris, France
T. Suzuki
Affiliation:
Laboratoire de Géologie, ER 224 CNRS, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris, France
E. Nicot
Affiliation:
Laboratoire de Géologie, ER 224 CNRS, Ecole Normale Supérieure, 46 rue d'Ulm, 75230 Paris, France
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Abstract

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X-ray powder diffraction (XRD) studies of the clay fraction of Upper Cretaceous mudstones from a shallow (2.5 km) drill hole in the Niger delta indicate a high geothermal gradient (about 100°C/km) during diagenesis. The mineralogy of the clays is similar to that observed elsewhere and consists of interstratified illite/smectite (I/S), kaolinite, and chlorite. Detrital mica and K-feldspar are also present throughout the section. The composition-depth relationship of the I/S is different from that observed in deeply buried Gulf Coast shales. The Niger delta rocks show a linear change in composition of the I/S as a function of depth in the drill hole from 60 to 10% smectite layers. The I/S ordering is R=0 in shallower samples and progresses to R=1 in deeper samples. The I/S in the deepest samples has R=3 ordering. No R=1 I/S showing a first-order 27-Å XRD reflection was found. The Niger delta sequence differs from the Gulf Coast sequence b. (1) a lack of R=1 I/S showing a 27-Å XRD reflection (which are common in Gulf Coast samples and contain 20% smectite layers), an. (2) the existence of a simple, continuous linear relation between the composition of the R=1 and R=0 I/S and depth.

A comparison of composition-temperature curves for I/S formed under different diagenetic regimes shows different types of I/S ordering in which the presence of R=1 I/S showing a 27-Å reflection and R=3 I/S types changes the composition-depth (and thus, composition-temperature) relations. These changes suggest a difference in the energy necessary to form the various ordering types. Also, geothermal gradient during burial appears to be responsible for different composition-temperature gradients found for the same type of I/S ordering.

Keywords

DiagenesisGeothermal gradientIllite/smectiteOrderingSmectite
Type
Research Article
Information
Clays and Clay Minerals , Volume 34 , Issue 4 , August 1986 , pp. 435 - 441
Copyright
Copyright © 1986, The Clay Minerals Society

References

Barker, C. E., 1983 Influence of time on metamorphism of sedimentary matter in liquid-dominated geothermal systems, western North America Geology 11 384–388.2.0.CO;2>CrossRefGoogle Scholar
Boles, J. R. and Franks, S. G., 1979 Clay diagenesis in Wilcox sandstones of southwest Texas J. Sed. Petr. 49 55–70.Google Scholar
Bruce, C. H., 1984 Smectite dehydration—its relation to structural development and hydrocarbon accumulation in northern gulf of Mexico basin Amer. Assoc. Petrol. Geol. 68 673–683.Google Scholar
Brusewitz, A. M., 1982 A filtering device for oriented X-ray mounts Clay Miner. 17 263–265.CrossRefGoogle Scholar
Dunoyer de Segonzac, G. (1969) Les minéraux argileux dans la diagenèse, passage au metamorphisme: Mem. Ser. Carte Als. Lorr. 29, 320 pp.Google Scholar
Eberl, D. D. and Hower, J., 1976 Kinetics of illite formation Bull. Geol. Soc. Amer. 87 1326–1330.2.0.CO;2>CrossRefGoogle Scholar
Freed, R. L., 1981 Shale mineralogy and burial diagenesis of Frio and Vicksburg Formations in two geopressured wells, McAllen Ranch area, Hidalgo County, Texas Trans. Gulf Coast Assoc. Geol. Soc. 31 189–293.Google Scholar
Hower, J. (1981) Shale diagenesis: in Clays and the Resource Geologist: Min. Assoc. Canada, Short Course Notes, 4, 199 pp.Google Scholar
Hower, J., Eslinger, E. V., Hower, M. E. and Perry, E. A., 1976 Mechanism of burial metamorphism of argillaceous sediments; 1. Mineralogical and chemical evidence Bull. Geol. Soc. Amer. 87 725–737.2.0.CO;2>CrossRefGoogle Scholar
Jennings, S. and Thompson, G. R., 1986 Diagenesis in Plio-Pleistocene sediments in the Colorado River delta, southern California J. Sed. Petr. 56 89–98.Google Scholar
McDowell, S. D. and Elders, W. A., 1980 Authigenic layer silicate minerals in borehole Elmore 1, Salton Sea geothermal field, California Contr. Min. Petr. 74 293–310.CrossRefGoogle Scholar
Nwachkwu, S. ùO., 1976 Approximate geothermal gradients in Niger delta sedimentary basin Amer. Assoc. Petr. Geol. Bull. 60 1073–1077.Google Scholar
Perry, E. and Hower, J., 1972 Late stage dehydration in deeply buried pelitic sediments Bull. Amer. Assoc. Petr. Geol. 56 2013–2021.Google Scholar
Reynolds, R. C., Brindley, G. W. and Brown, G., 1980 Mixed layer clays Crystal Structure of Clay Minerals and Their X-ray Identification .CrossRefGoogle Scholar
Reynolds, R. C. and Hower, J., 1970 The nature of inter-layering in mixed-layer illite-montmorillonite Clays & Clay Minerals 18 25–36.CrossRefGoogle Scholar
Schmidt, B., 1973 Interstitial water composition and geochemistry of deep Gulf Coast shales and sandstones Bull. Amer. Assoc. Petr. Geol. 57 321–337.Google Scholar
Short, K. C. and Stauble, A. J., 1967 Outline of the geology of the Niger delta Amer. Assoc. Petr. Geol. 51 761–779.Google Scholar
Środoń, J., 1980 Precise identification of illite/smectite interstratification by X-ray powder diffraction Clays & Clay Minerals 28 401–411.CrossRefGoogle Scholar
Steiner, A., 1968 Clay minerals in hydrothermally altered rocks at Wairakei, New Zealand Clays & Clay Minerals 16 193–213.CrossRefGoogle Scholar
Teichmüller, M., 1979 Die Diagenese den Gesteinen des Tertiars und Mesozoikums des mittelern Oberrhein-Grabens Forschr. Geol. Reinld. Westf. 27 19–49.Google Scholar
Velde, B., 1985 Possible chemical controls of illite/smectite composition during diagenesis Mineral. Mag. 49 387–391.CrossRefGoogle Scholar
Velde, B., 1985 Clay Minerals: A Physico-chemical Explanation of Their Occurrence Amsterdam Elsevier.Google Scholar
Weaver, C. E. and Beck, K. C. (1971) Clay-water diagenesis during burial: how mud becomes gneiss: Geol. Soc. Amer. Spec. Paper 134, 96 pp.Google Scholar
Yeh, H.-W. and Savin, S. M., 1977 Mechanism of burial metamorphism of argillaceous sediments, 3. O-isotope evidence Bull. Geol. Soc. Amer. 88 1321–1330.2.0.CO;2>CrossRefGoogle Scholar