Abstract—The study area is dominantly made up of pelitic, semipelitic schists, amphibolites and quartzite. The metasedimentary sequence has been intruded by granitic rocks in two phases. Signatures of polyphase deformation are clearly discernible in these rocks. The first phase of deformation (D1) produced schistosity (S1) with downdip lineation. Mesoscopic isoclinical folds are rarely seen. The second phase deformation (D2) produced asymmetric folds on S1 and axial planar crenulations cleavage (S2). In the northern part S2 has almost completely obliterated the earlier schistosity and the regional schistosity is here combined (S1/S2). The last deformation episode D3 gently folded S1 and S2 on transverse axial planes. Mylonites, ultramylonites and phyllonites are confined to the southern part of the area which represents the western extension of the Singhbhum Shear Zone. Mylonitic foliation within the feldspathic schist and micaceous phyllonite is parallel to S1. Isolated late stage shear zones occur throughout the area. Evidences suggest that shearing started during D1 and occurred during different stages in the deformation history. The deformation events comprising D1, D2, D2A and ductile shearing are parts of the same deformation cycle with N-S compression combined with simple shear with top-to-the-south sense of movement. Late stage longitudinal compression occurs during D3.

Index Terms—Pressure solution bands, Transposed schistosity, Differentiated crenulation cleavage, Extensional crenulation cleavage, Progressive shearing, Conjugate shear planes

Cite:Dr. Chandrabali Mukhopadhyay, "Structural Analysis in the Central Sector of the North Singhbhum Fold Belt in and around Sini, Jharkhand District, Bihar, India," International Journal of Geology and Earth Science, Vol. 3, No. 3, pp. 10-22, September 2017.