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

Amitava Kundu ¹, Santanu Bhattacharjee ¹

Affiliations
1 Geological Survey of India, Faridabad, IN

Abstract

No Abstract.

Full Text

   

V. Ravikant ¹, Amitava Kundu ¹

Affiliations
1 Antarctica Division, Geological Survey of India, NH-5P, N.I.T., Faridabad - 121001, IN

Abstract

A retrograde path inferred for the Schirmacher Hills granulites involves near ITD path following post-peak granulite facies metamorphism (M1/D1), preserved only in enclaves, followed by near IBC path, M3, post dating M2/D2 granulites facies metamorphism and deformation. Final uplift and cooling of the terrain occurred in the upper amphibolite facies metamorphic conditions, M4, syntectonic with respect to D3 deformation and emplacement of large volume of syntectonic granitoids. Fluids released during cooling and crystallization of these granitoids probably caused the large scale retrogression of granulite facies rocks to amphibolite facies gneisses.

Keywords

Petrology, Granulites, Geothermobarometry, Antarctica.

Full Text

     

D. Jayapaul ¹, Amitava kundu ², M. P. Gaur ¹, K. V. Krishnamurthy ³

Affiliations
1 Antarctica Division, Geological Survey of India, NH 5P, NIT, Faridabad- 121001., IN
2 EPMA Laboratory, Geological Survey of India, NH SP, Faridabad- 121001., IN
3 AMSE, Geological Survey of India, Bangalore-560078, IN

Abstract

The Skorvestallen batholith intrusive into granulitic crust consists of dominant coarse-grained pink granite, small rounded bodies of greenish grey fayalite granite, stocks of grey porphyritic biotite granite and porphyritic fayalite granite. These weakly peraluminous granites show A-type signatures with characteristic high Fe/(Fe + Mg), TilMg, HFSE such as Y and Zr, LREE and Zn. The granites crystallized at high temperatures and were emplaced at mid-crustal pressures. The paper discusses their possible mode of origin based on petrochemical studies.

Keywords

A-type granites, Petrology, Petrochemistry, Genesis, East Antarctica.

Full Text

     

N. C. Pant ¹, Amitava Kundu ¹, Sonalika Joshi ¹

Affiliations
1 Geological Survey of India, NH-5P, N I T, Faridabad-121001, IN

Abstract

The subcalcic Fe-Mg amphibole rocks (anthophyllite-cummingtonite schist) are exposed in the Bayal area of Mahendragarh district in southern Haryana. These are considered to be hydrothermally altered mafic volcanic rocks metamorphosed to amphibolite facies. Monazite is present in association with cordienite and quartz in the anthophyllite-cummingtonite schist and texturally defines the metamorphic event in these rocks. In the present study two grains of Monazite from anthophyliite cummingtonite schist have been dated. Monazite grain in sample no 135 yielded an age 952±16 Ma while sample no 277 gave an age ot 945±14 Ma. This is inferred to be the age of metamorphism of rocks of Delhi Supergroup in Haryana.

Keywords

Delhi Supergroup, Monazite, EPMA Ages, Haryana.

Full Text

     

Amitava Kundu ¹, M. J. D'souza ¹, Anand Mohan ²

Affiliations
1 Antarctica Division, Geological Survey of India, Faridabad, IN
2 Department of Geology, Banaras Hindu University, Varanasi, IN

Abstract

Preliminary study of metamorphic reaction textures coupled with thermobarometry suggests that the metapelites. garnet-clinopyroxene gneisses. calc-silicate gneisses and orthopyroxene bearing quartzo-feldspathic gneisses exposed in Dallmannfjellet-Conrad area, central Dronning Maud Land, East Antarctica were metamorphosed to granulite grade. Peak metamorphic conditions evaluated from core thermobarometry are ~900 - 1050°C and pressure ~9 kbar. Sillimanite and garnet growth over spinel in metapelites suggests cooling of the rocks to 800°C, followed by a mild decompression inferred on the basis of orthopyroxene+plagioclase moats around garnet in metanorite pods within metapelite. The metanorite pods record P-T conditions of 7-10 kbar and 750-850°C. Late component of the P-T segments is represented by cooling stage and eventual exhumation of the terrain.

Keywords

Petrology, Reaction Textures, Thermobarometry, Metamorphic History, East Antarctica.

Full Text