Abstract
Mineralogical and chemical investigations (<2μm clay separates) of shale samples from the Neogene-age Surma Group obtained from four wells (Habiganj-11, Shahbazpur-1, Titas-11, Titas-15) in the Bengal basin, Bangladesh, were carried out in order to reveal the clay mineral composition as reservoir exploration and exploitation requires a good understanding of the clay minerals. The samples were analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-Ray fluorescence spectrometry (XRF). Mineralogically, the sub-surface Surma Group shales comprise predominantly quartz, plagioclase, illite, chlorite, kaolinite, with lesser amounts of K-feldspar, dolomite and smectite, and minor to trace amounts of calcite, siderite and pyrite. The chemical composition of the <2 μm clay separates also suggests an illite and chlorite-rich composition. With increasing burial depth, the Surma Group shales are enriched in illite. The gradual decreasing of the smectite clays with depth and ultimate disappearance at greater depths (≥ 3000 m) may have been responsible for the presence of the diagenetic illite. Based on the mineralogical composition it is most likely that the illite-chlorite associations together with quartz and feldspar were predominantly detrital in origin and thus reflect the presence of a rapidly-rising source terrain not subjected to intense weathering.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Alam, M. (1989) Geology and depositional history of Cenozoic sediments of the Bengal Basin of Bangladesh, Palaeogeor., Palaeoclimetol., Palaeoecol., v.69, pp.125–139.
Alam, M., et al. (2003) An overview of the sedimentary geology of the Bengal Basin in relation to the regional tectonic framework and basin-fill history, Jour. Sediment. Geol., v.155, pp.179–208.
Azzaro, E., Bellanca, A. and Neri, R. (1988) Clay mineral studies of the Tripoli Formation (Lower Messinian), Sicily. Clay Minerals, v.23, pp.309–321.
Brindley, G.W. and Brown, G. (1980) Crystal structures of clay minerals and their X-ray identification. Mineral. Soc. London, Monograph 5, 495p.
Curray, J.R. and Moore, D.G. (1974) Sedimentary and tectonic processes in the Bengal deep sea fan and geosynclines. In: C.A. Burke and C.L. Darke (Eds.), The Geology of Continental Margins, Springer, New York, pp.617–628.
Hiller, K. and Elahi, M. (1984) Structural development and hydrocarbon entrapment in the Surma Basin, Bangladesh (north-east Indo-Burman fold belt). In: Proc. 5th Offshore South Asia Conference Singapore.
Hower, J., Eslinger, E.V., Hower, M. & Perry, E.A. (1976) Mechan-ism of burial metamorphism of argillaceous sediments: I. Mineralogical and chemical evidence. Geol. Soc. Amer. Bull., v.87, pp.725–737.
Imam, M.B. and Shaw, H.F. (1987) Diagenetic controls on the reservoir properties of gas bearing Neogene Surma Group sandstones in the Bengal Basin, Bangladesh. Marine Petrol. Geol., v.4, pp.103–110.
Imam, M.B. (1989) Clay minerals in sandstone from Bhuban and BokaBil Formations: Implications in petroleum geology. Bangladesh Jour. Geol., v.8, pp.1–11.
Imam, M.B. (1994) X-ray diffraction study on Neogeneshales from the Patharia anticline, eastern Bangladesh, with emphasis on smectite clay dehydration and implications. Jour. Geol. Soc. India, v.44, pp.547–561.
Jahren, J.S. and Aagaard, P. (1989) Compositional variations in diagenetic chlorites and relationships with formation-water chemistry. Clay Minerals, v.24, pp.157–170.
JCPDS, (1986) Mineral Powder Diffraction File Data Book. Swarthmore PA., 1396p.
Johnson, S.Y. and Alam, A.M.N. (1991) Sedimentation and tectonics of the Sylhet trough, Bangladesh. Geol. Soc. Amer. Bull., v.103, pp.1513–1527.
Moore, D.M. and Reynolds, R.C. (1997) X-ray diffraction and the identification and analysis of clay minerals. Oxford, 378p.
Perry, E. and Hower, J. (1970) Burial diagenesis in Gulf coast pelitic sediments. Clays and Clay Minerals, v.18, pp.165–177.
Rahman, M.J.J. and Suzuki, S. (2007) Composition of Neogene Shales from the Surma Group, Bengal Basin, Bangladesh: Implications for Provenance and Tectonic Setting. Austrian Jour. Earth Sci., v.100, pp.54–64.
Schultz, L.G. (1964) Quantitative interpretation of mineralogical composition from X-ray and chemical data for the Pierre shale. USGS Prof. Paper, 391-C.
Uddin, A. and Lundberg, N. (1998) Cenozoic history of the Himalayan-Bengal system: Sand composition in the Bengal basin, Bangladesh. Geol. Soc. Amer. Bull., v.110, pp.497–511.
Weaver, C.E. and Beck, K.C. (1971) Clay-water diagenesis during burial: How mud becomes gneiss. Geol. Soc. Amer. Spec. Paper, no.134, 96p.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rahman, M.J.J., Yeasmin, R. & McCann, T. Mineralogy and chemical composition of the clay fraction of Neogene shales from the Surma Group in the Bengal basin, Bangladesh. J Geol Soc India 88, 705–710 (2016). https://doi.org/10.1007/s12594-016-0537-z
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s12594-016-0537-z