Magmatic epidote in the Grenvillian granitoids of North Purulia Shear Zone, Chhotanagpur Gneissic Complex, India and its significance

摘要

Magmatic epidotes of granitoid pluton from North Purulia Shear Zone, eastern India, are identified by textural and chemical criteria. The accessory sphene, epidote, allanite and magnetite in the granitoid indicate high fO(2) during crystallization. Hornblendes were crystallized between 1.2 and 4.8 kbar, 753 degrees C and 783 degrees C as well as high fO(2) (>Ni-NiO buffer). Preservation of magmatic epidote in pluton emplaced at low pressure is due to rapid magma ascent (>3.1 km/year). Fast upward transportation of parental magma of the pluton took place through extensional voids along the regional shear zone.