Deformational History of the Metamorphic Tectonites in and around Bangsar area, Kamrup District, Assam

Abstract

The structural analysis of the Precambrian rocks around Bangsar area, has unfolded at least four phases of deformation associated with amphibolite facies metamorphism. The earliest phase of deformation (D₁) has produced close to tightly appressed, intrafolial fold (F₁) and is accompanied with a pervasive planar structure (S₁) of regional extent. The second phase of deformation (D₂) was responsible for layer parallel shortening (buckling) of the mechanically active S₀ and S₁ fabrics in the NW-SE longitudinal compressive tectonics leading to the formation of NE-SW trending up and down facing folds of probable plane non- cylindrical nature. The Second phase of deformation (D₂) developed the Bhringeshwar Synform. The third phase(D₃)of deformation was responsible for open, warp type fold (F₃) which reflect dome and basin structures (interference pattern 1). The intensity of D₃ gradually decreases and the fourth deformational (D₄) impact is related to brittle phase in the form of minor faulting and fracturing.

Keywords: Tectonites, Synform, Interference pattern.