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Polyphase deformation and garnet growth in pelitic schists of Sausar Group in Ramtek area, Maharashtra, India: A study of porphyroblast-matrix relationship

2007; Springer Science+Business Media; Volume: 116; Issue: 5 Linguagem: Inglês

10.1007/s12040-007-0041-3

2347-4327

Anupam Chattopadhyay, Nandita Ghosh,

Rock Mechanics and Modeling

Polyphase deformation and metamorphism of pelitic schists of Chorbaoli Formation of Sausar Group in and around Ramtek area, Nagpur district, Maharashtra, India has led to the development of garnet and sataurolite porphyroblasts in a predominantly quartz-mica matrix. Microstructural study of oriented thin sections of these rocks shows that garnet and staurolite have different growth histories and these porphyroblasts share a complex relationship with the matrix. Garnet shows at least two phases of growth — first intertectonic between D1 and D2 (pre-D2 phase) and then syn-tectonic to post-tectonic with respect to D2 deformation. Growth of later phase of garnet on the earlier (pre-D2) garnet grains has led to the discordance of quartz inclusion trails between core and rim portion of the same garnet grain. Staurolite develops only syn-D2 and shows close association with garnet of the later phase. The peak metamorphic temperature thus coincided with D2 deformation, which developed the dominant crenulation schistosity (S2), regionally persistent in the terrain. The metamorphic grade reached up to middle amphibolite facies in the study area, which is higher than the adjoining southern parts of Sausar Fold Belt.