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

Rajib Kar ¹

Affiliations
1 Department of Geology, J K College, Purulia - 723 101, IN

Abstract

The granulite complex around Jenapore, Orissa bears the imprints of three deformations, of which first two (D₁ and D₂,) are strong events and related to pervasive deformational fabrics S₁, and S₂, respectively. Sector-wise structural analyses reveal that regional F₁ folds, product of D₁ deformation, are isoclinal, reclined, while the regional F₂, folds, product of D₂, deformation, are upright with overall gentle easterly plunges. Also, the polyclinal and non cylindrical nature of regional F₂ prior to F₃ folding is evident. This geometrical relation and certain key features such as (1) transposition/cross-cutting of early deformation fabric by later ones, (2) different modes of recrystallization during separate deformation episodes, (3) distinct deformational regime and response of materials related to deformation fabrics and (4) recrystallization of early fabric to a new one under granulite facies condition, definitely indicate a hiatus between D₁ and D₂ deformations.

Keywords

Fold Geometry, Deformation Fabrics, Hiatus, Structural History, Eastern Ghats Granulite Belt.

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Rajib Kar ¹, S. Bhattacharya ²

Affiliations
1 Department of Geology J K College, Puruha - 723 101, IN
2 Geological Studies Unit, Indian Statistical Institute 203 B T Road Kolkata 700035, IN

Abstract

Two types of high Mg-Al sapphirie granulites are noted from the area In and around Paderu, Eastern Ghats GranulIte belt, IndIa One is relatIvely more mafic, coarse gramed variety with crude internal foliation (type I) and the other is relatively fine grained, more fe/SiC and migmatitic variety wIth a promment foliation (type II) In thIs granulte belt Impress of three phases of folding could be detected, with corresponding fabric development Enclaves of type I varIety are preserved with in charnockite In the low stram zone core of mesoscopic F₂ folds, defined by S₁, streaky gneissIc fohation The crude mternal foItatIon m the enclave, dIscordant to S₁ of the host could be pre S₁ The bands of type II vanety together wIth mternal foItation, S₂ define F₂ folds Thus the high Mg Al sapphirine granulites preserve the Imprints of the early deformational fabric The mineral growth in them along with this fabric, indicating ultra high temperature metamorphism is correlatable to this early compressive deformation.

Keywords

Sapphirine Granulites, Deformation Structures, Fabric, Mineral Growth, Paderu, Eastern Ghats.

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