A suite of rocks from Borra Carbonate Granulite Complex (BCGC) in the Eastern Ghats granulite belt displays superposed structures
and overprinted mineral assemblages that reveal multiple episodes of tectonothermal reworking of the complex under granulite
facies condition. Five distinct episodes of deformation (D
1, D
2, D
3, D
4 and D
5) and four phases of metamorphism (M
1, M
2, M
3 and M
4) are recorded. The signature of the earliest tectonothermal event, D
1 is a gneissic foliation (S
1) denned by segregation of peak granulite facies mineral assemblages corresponding to prograde M
1 metamorphism. M
2 metamorphic overprint represents an episode of near-isobaric cooling of the complex under a static condition. D
2 represents an episode of ductile deformation manifested by isoclinal folding (F
2) and associated extensional structures, within a broad framework of coaxial bulk deformation. The present study reveals that
D
2 took place subsequent to M
2 - Subsequent deformation, D
3, produced F
3 folds and also deformations of boudins formed during D
2. M
3, which is synchronous with F
3, represents a near isothermal decompression of the BCGC. This was followed by a weak structural readjustment (D
4), producing E-W cross folds. The latter was not, however, associated with any recognizable petrological reworking. In the
terminal events, deformation (D
5) and mineral reactions (M
4) were localized along narrow intersecting shear zones. The latter acted as channelways for carbonic and still later hydrous
fluid infiltration. The available thermobarometric data from BCGC and other areas of the Eastern Ghats belt reveal that reworking
during M
2 and M
3 ensued in a thermally perturbed regime. The high thermal regime might also have persisted during carbonic fluid infiltration
related to terminal reworking (M
4).
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