Hostname: page-component-78c5997874-s2hrs Total loading time: 0 Render date: 2024-11-11T03:16:27.542Z Has data issue: false hasContentIssue false

Crystal Chemistry of Layer Silicates of the Miocene Green Grain (Congo Basin) from Transmission Electron Microscopy (TEM) and Analytical Electron microscopy (AEM) Observations

Published online by Cambridge University Press:  28 February 2024

A. Wiewióra
Affiliation:
Institute of Geological Sciences, Polish Academy of Sciences, ul. Twarda 51/55, 00-818, Warszawa, Poland
P. Giresse
Affiliation:
Laboratoire de Sédimentologie et Géochimie marine, URA CNRS 715, LEA Sciences de la Mer, Université de Perpignan, Avenue de Villeneuve, 66860 Perpignan, France
A. M. Jaunet
Affiliation:
Laboratoire de Sédimentologie et Géochimie marine, URA CNRS 715, LEA Sciences de la Mer, Université de Perpignan, Avenue de Villeneuve, 66860 Perpignan, France
A. Wilamowski
Affiliation:
Institute of Geological Sciences, Polish Academy of Sciences, ul. Twarda 51/55, 00-818, Warszawa, Poland
F. Elsass
Affiliation:
Sciences du Sol, INRA, Route de Saint Cyr, 78026 Versailles, France
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Transmission electron microscopy (TEM) and analytical electron microscopy (AEM) methods were used to study the crystal chemistry of phyllosilicates occurring in green grains of Miocene sediments from the Congo continental shelf. Using diagrams based on wt. % K and the (Fe + Mg)/Al ratio, minerals were distinguished from mixed-layer phases. The most abundant detrital mineral is Fe-kaolinite. The morphology and composition identify this mineral as a component of ferralitic soils. This Fe-rich kaolinite has undergone a complex process of partial dissolution and recrystallization and further enrichment in Fe and, to a lesser extent, in Mg in the marine environment. The detrital mica observed with TEM retains the original morphology and chemistry of muscovite. Alteration processes resulted in the crystallization of 1:1 trioctahedral Fe2+ and Mg-rich minerals and interstratified phases with 1:1 and 2:1 layers in varying proportions observed with the aid of high-resolution transmission electron microscopy (HRTEM) imaging. Included among the newly formed 7-Å phases are those apparently containing excess Si. The smectites are apparently neoform, and chemical analyses showed that these marine K-smectites belong to the beidellite-nontronite series and have tetrahedral substitutions similar to muscovite. Their compositions are closer to beidellite than to nontronite, although the latter was observed in association with goethite. The TEM observations and crystallochemical data show that mineral alteration ceased after forming mixed-layer minerals, and alteration did not reach the glauconitization stage. Apparently, the Miocene assemblages experienced rapidly changing environmental conditions and high sedimentation rates that continue today.

Type
Research Article
Copyright
Copyright © 1999, The Clay Minerals Society

References

Amouric, M. and Parron, C., 1985 Structure and growth mechanism of glauconite as seen by high-resolution transmission electron microscopy Clays and Clay Minerals 33 473482 10.1346/CCMN.1985.0330601.CrossRefGoogle Scholar
Amouric, M. Parron, C. Casalini, L. and Giresse, P., 1995 A (1:1) 7-Å Fe phase and its transformation in Recent sediments: An HRTEM and AEM study Clays and Clay Minerals 43 446454 10.1346/CCMN.1995.0430408.CrossRefGoogle Scholar
Bailey, S.W., 1988 Odinite, a new dioctahedral-trioctahedral Fe3+-rich 1:1 clay mineral Clay Minerals 23 237247 10.1180/claymin.1988.023.3.01.CrossRefGoogle Scholar
Elsass, F. Beaumont, A P M Jaunet, A.-M. and Tessier, D., 1998 Changes in layer organization of Na- and Ca-exchanged smectite materials during solvent exchanges for embedment in resin The Canadian Mineralogist 36 14751483.Google Scholar
Giresse, P., 1985 Le fer et les glauconies au large du fleuve Congo Sciences Geologiques, Bulletin 38 293322 10.3406/sgeol.1985.1711.CrossRefGoogle Scholar
Giresse, P. and Odin, G.S., 1973 Nature minéralogique et origine des glauconies du plateau continental du Gabon et du Congo Sedimentology 20 457488 10.1111/j.1365-3091.1973.tb01626.x.CrossRefGoogle Scholar
Giresse, P. Wiewióra, A. and Lacka, B., 1988 Mineral phases and processes within green peloids from two Recent deposits near the Congo River mouth Clay Minerals 23 447458 10.1180/claymin.1988.023.4.11.CrossRefGoogle Scholar
Giresse, P. Oualembo, P. Wiewióra, A. Łącka, B. and Zawidzki, P., 1992 Compositions polyphasées des grains verts du bassin du Congo; Comparaison de dépôts Récents, Holocènes (103–104 ans) et Miocènes (107 ans) Archiwum Mineralogiczne 47 1749.Google Scholar
Herbillon, A.J. Mestdagh, M.M. Vielvoye, L. and Derouane, E.G., 1976 Iron in kaolinite with special reference to kaolinite from tropical soils Clay Minerals 11 201220 10.1180/claymin.1976.011.3.03.CrossRefGoogle Scholar
Jepson, W.B., 1988 Structural iron in kaolinites and in associated ancillary minerals Iron in Soil and Clay Minerals 217 467536 10.1007/978-94-009-4007-9_15.CrossRefGoogle Scholar
Malengreau, N. Muller, J.P. and Calas, G., 1994 Fe-speciation in kaolins: A diffuse reflectance study Clays and Clay Minerals 42 137147 10.1346/CCMN.1994.0420204.CrossRefGoogle Scholar
Maley, J., 1996 The African rain forest—main characteristics of changes in vegetation and climate from the Upper Cretaceous to the Quaternary Proceedings of the Royal Society of Edinburgh 104B 3173.Google Scholar
Mestdagh, M.M. Vielvoye, L. and Herbillon, A.J., 1980 Iron in kaolinite, II. The relationship between kaolinite crystallinity and iron content Clay Minerals 15 113 10.1180/claymin.1980.015.1.01.CrossRefGoogle Scholar
Muller, J.P. Calas, G., Murray, H.H. Bundy, W.M. and Harvey, C.C., 1993 Genetic significance of paramagnetic centers in kaolinites Kaolin Genesis and Utilization Boulder, Colorado Clay Minerals Society of America 261289.Google Scholar
Nahon, D., 1981 Modes de répartition des métaux dans les solutions solides des altérations tropicales; applications aux concentrations supergènes ferrugineuses Valorisation des Ressources du Sous-Sol 47 254264.Google Scholar
Odin, G.S. Bailey, S.W. Amouric, M. Fröhlich, F. Waychunas, G.A. and Odin, G.S., 1988 Mineralogy of the facies verdine Green Marine Clays Amsterdam Elsevier 159206.CrossRefGoogle Scholar
Oualembo-Mophawe, P.A., 1992 Les successions de grains verts argileux méso-cénozoïques du bassin marin congolais; paléoenvironnement, sédimentologie, minéralogie et géochimie .Google Scholar
Parron, C., 1989 Voies et mécanismes de cristallogénèse des minéraux argileux ferriferes en milieu marin. Le processus de glauconitisation: évolutions minérales, structurales et géodynamiques .Google Scholar
Porrenga, D.H., 1967 Glauconite and chamosite as depth indicators in the marine environment Marine Geology 5 495501 10.1016/0025-3227(67)90056-4.CrossRefGoogle Scholar
Poumot, C., 1989 Palynological evidence for eustatic events in the tropical Neogene Centre Recherche Exploration Elf-Aquitaine Bulletin 13 437453.Google Scholar
Sakharov, B.A. Besson, G. Drits, V.A. Kameneva, Y.U. Salyn, A.L. and Smoliar, B.B., 1990 X-ray study of the nature of stacking faults in the structure of glauconites Clay Minerals 25 419435 10.1180/claymin.1990.025.4.02.CrossRefGoogle Scholar
Séranne, M. Séguret, M. and Fauchier, M., 1992 Seismic super-units and post-rift evolution of the continental passive margin of southern Gabon Société Géologique de France Bulletin 163 135146.Google Scholar
Siesser, W.G., 1978 Leg 40 results in relation to continental shelf and onshore geology Deep Sea Drilling Project, Internal Reports 40 965979.Google Scholar
Stucki, J.W., 1988 Structural iron in smectites Iron in Soils and Clay Minerals 217 625675 10.1007/978-94-009-4007-9_17.CrossRefGoogle Scholar
Środoń, J. Andreoli, C. Elsass, F. and Robert, M., 1990 Direct high-resolution transmission electron microscopic measurement of expandability of mixed-layer illite/smectite in bentonite rock Clays and Clay Minerals 38 373379 10.1346/CCMN.1990.0380406.CrossRefGoogle Scholar
Von Gaertner, H.R. and Schellmann, W., 1965 Rezente Sedimente in Küstenbereich der Halbinsel Kaloun, Guinea Tschermaks Mineralogische und Petrographische Mitteilungen 10 349367 10.1007/BF01128639.CrossRefGoogle Scholar
Warren, E.A. and Ransom, B., 1992 The influence of analytical error upon the interpretation of chemical variations in clay minerals Clay Minerals 27 193209 10.1180/claymin.1992.027.2.05.CrossRefGoogle Scholar
Wiewióra, A., 1990 Crystallochemical classifications of phyllosilicates based on the unified system of projection of chemical composition: I. The mica group Clay Minerals 25 7381 10.1180/claymin.1990.025.1.08.CrossRefGoogle Scholar
Wiewióra, A., 1990 Crystallochemical classifications of phyllosilicates based on the unified system of projection of chemical composition: III. The serpentine-kaolin group Clay Minerals 25 9398 10.1180/claymin.1990.025.1.10.CrossRefGoogle Scholar
Wiewióra, A. Łącka, B. and Giresse, P., 1996 Characterization and origin of 1:1 phyllosilicates within peloids of the Recent, Holocene and Miocene deposits of the Congo Basin Clays and Clay Minerals 44 587598 10.1346/CCMN.1996.0440502.CrossRefGoogle Scholar