Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

T. K. Ghosh ¹

Affiliations
1 Department of Geology, University of Calcutta, Calcutta-700 019, IN

Abstract

In the course of systematic palynological investigation of the Lower Gondwana (Permian) coals from Darjeeling district, West Bengal, 36 miospore genera are recorded. The two coal-bearing Lower Gordwana slices, referred to as Rongtong or Lower unit and Tindharia or upper unit in this paper, differ both in qualitative and quantitative distribution of miospore genera and miospore groups. It is also possible to divide each unit into zones on the basis of frequency distribution of some miospore genera and this zonation may prove helpful in the correlation of the coal seams of the area. Miospore assemblage of the coal is comparable with those from the Lower Gondwana of Peninsular India and suggests that Rongtong unit is equivalent to the upper Barakar, and Pankhabari-Bagrakote unit to the Raniganj assemblages respectively of Peninsular Lower Gondwana.

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S. C. Patel ¹, B. R. Frost ², I. Faizan ¹, R. Dey ³, T. K. Ghosh ⁴

Affiliations
1 Department of Earth Sciences, Indian Institute of Technology, Bombay, Powai, Mumbai - 400076, IN
2 Department of Geology and Geophysics, University of Wyoming, Laramie, WY 82071, US
3 MR Division, R & C Directorate, ACC Ltd., LBS Marg, Thane - 400 604, IN
4 University Science Instrumentation Centre, University of Roorkee, Roorkee - 247667, IN

Abstract

Massif type anorthositic rocks in Bolangir area of the Eastern Ghats belt contain garnet porphyroblasts, which are surrounded by reaction coronas. The corona usually comprises a vermicular intergrowth, which in one instance consists of radial orthopyroxene and anorthite-rich plagioclase, and in another of radial chlorite and anorthite-rich plagioclase. Some of the anorthositic rocks are layered with thin discontinuous mafic layers of clinopyroxene and biotite. Notable is the presence of retrograde ferro-anthophyllite in the mafic layers of some of the rocks. Thermobarometric calculations using assemblage in the orthopyroxene corona indicate decompression from minimum peak P-T condition of 8 kbar and 700°C.

Keywords

Anorthosite, Metamorphism, Corona, Decompression, Bolangir, Eastern Ghats.

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T. K. Ghosh ¹

Affiliations
1 Geology Department, Calcutta University, Calcutta - 700 019, IN

Abstract

Striated structure has been .recorded in some coal seams of Darjeeling and Rangit Valley Coalfields. This structure is generally restricted within the vitrain bands which range in rank from Iignitous to anthracite. The structure is fonned mainly due to brittle deformation with or without little rise in temperature.

Keywords

Coal Petrology, Rangit Valley Coalfield, Himalaya.

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