Field Investigation with their Textural Relationship of the Metapelites around Gopinathpur, East Singhbhum, India

ABSTRACT Proterozoic mobile belts are considered as fringing region of the Archaean-Proterozoic cratons and preserve the best evidence of sedimentation, magmatism, deformation, and metamorphism depending on the type of tectonic settings. The North Singhbhum Mobile Belt (NSMB) is a north-dipping ductile shear zone of Proterozoic age distinguished by multiple folded, low to mediumgrade metapelites and meta-igneous rocks sandwiched between the Archaean Singhbhum Craton in the South, and the Palaeo-Neo Proterozoic Chotanagpur Gneissic Complex (CGC) in the north. Since NSMB consists of a thick sequence of sediments that were deposited from Paleoproterozoic to Mesoproterozoic, it is therefore important for determining the syn- and post-orogenic processes to decode the time-space tectono-metamorphic history of this mobile belt. Field observations indicate the presence of an anticlinorium with an east-west trending fold axis, where rocks from greenschist facies (chlorite-biotite-garnet-schist) are commonly found at the limb, transitioning to amphibolite facies towards (garnet-staurolite-sillimanite gneiss) the hinge zone. Textural studies demonstrate the alignment of micaceous minerals that create the S1 schistosity plane overprinted by S2 crenulation cleavage in the chlorite-schist and mica-schist. The garnet and staurolite porphyroblast exhibit syn- to posttectonic growth, suggesting static growth conditions during the waning phase of metamorphism. Studies pertaining to mineral assemblages further imply that fibrolite formation is more favorable during the primary stages of metamorphism (M1) associated with D1 deformation.