Deformational and crystallization history of the Precambrian rocks in north-central Aravalli Mountain, Rajasthan, India

Sharma, Ram S. (1977) Deformational and crystallization history of the Precambrian rocks in north-central Aravalli Mountain, Rajasthan, India Precambrian Research, 4 (2). pp. 133-162. ISSN 0301-9268

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Official URL: http://www.sciencedirect.com/science/article/pii/0...

Related URL: http://dx.doi.org/10.1016/0301-9268(77)90044-4

Abstract

Large-scale structures, textures and mineral assemblages in the Precambrian rocks of the Banded Gneissic Complex and the overlying Delhi Group in north-central Aravalli Mountain reveal a complex deformational-crystallization history. In the basement Gneissic Complex at least three deformational events, D0, D1 and D2, and two separate episodes of metamorphism, M1 and M2, are recognized. The supracrustal Delhi Rocks display only two phases of deformation, D1 and D2, associated with a single protracted period of metamorphism, M2. The first phase of deformation (D1) of the Delhi orogeny (1650-900 m.y.) produced large isoclinal folds that are overturned towards the southeast and have gentle plunges in NE and SW directions. The second phase of deformation (D2) gave rise to tight open folds on the limbs and axial-plane surfaces of the D1 folds. These folds generally plunge towards the N and NNW at 30°-80°. In the Basement Complex one more deformation (D0) of the Pre-Delhi orogeny (> 2000 m.y.) is recorded by the presence of reclined and recumbent folds with W to WNW trending fold axes. The D0 folds were superimposed by D1 and D2 folds during the Delhi orogeny. The three deformational events have been correlated with the crystallization periods of minerals in the rocks and a setting in time is established for this part of the Aravalli range.

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