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

D. K. Bhattacharya ¹, S. Dasgupta ²

Affiliations
1 Department of Geology, Ranchi University, Ranchi - 834 008, IN
2 Department of Mines and Geology, Ranchi - 834 002, IN

Abstract

Apatite mineralisation occurs in the host rock chlorite phyllite which grades into chlorite schist and is granitised. Discontinuous veins of apatite within apatite-magnetite rock exhibit many morphological types. The apatites also contain tantalum, niobium, titanium, molybdenum and vanadium. Studies reveal that apatite mineralisation is controlled by both structure and lithology.

Keywords

Apatite Mineralisation, Purulia Dist, West Bengal.

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K. C. Prashra ¹, S. Dasgupta ²

Affiliations
1 306 F, Sector 7A, Chandigarh - 160019, IN
2 129. D. J. Road, Bhadrakali, Hooghly (W.B.) - 712232, IN

Abstract

The Miyar glacier is a 28 km. long valley-type galcier with a number of transverse tributary glaciers, encompassing an area of about 110 sq. km of ice and snow in its basin. It has retreated by about 325 m between 1963 and 1983 with an average annual retreat of about 16 m. This phenomenon is comparable with similar recessionery trends of other galciers of Lahaul, which indicates deglaciation period still prevalent in this part of the Himalaya.

Keywords

Glaciology, Geomorphology, Lahaul- Spiti, Himachal Pradesh.

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S. S. Thakur ¹, S. C . Patel ¹, S. Dasgupta ¹

Affiliations
1 Department of Earth Sciences, Indian Institute of Technology, Powai, Mumbai- 400 076, IN

Abstract

The Precambrian Sukma supracrustal sequence near Nagaras, southern Bastar Craton, has been mapped as two quartzite lithounits and an intervening undifferentiated unit comprising Mg-Al rich granulite, mafic granulite, amphibolite and hornblende schist. The rocks bear imprints of three phases of deformation. The structures of the first generation are represented by rarely occurring small isoclinal folds(F₁) on bedding (S₀), and pervasive axial planar foliation (S₁). The folds of second generation (F₂) vary from open to close, and upright to locally overturned with NNWSSE to NNE-SSW striking axial planes Gentle warps with ESE-WNW striking axial planes represent folds of the third generation (F₃) Superposition of F₃ folds on F₂ folds has resulted in Dome-and-Basin interference pattern in both small and large scales. The map pattern is elongated in the N-S direction because of control by F₂ folds, and slight concave geometry towards west is the result of F₃ folding.

Keywords

Structural Geology, Sukma Supracrustals, Granulite, Bastar, Chhattisgarh.

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