Mineral Chemistry and Petrochronology of Zircon from Dudhi Group, Northwestern Chhotanagpur Granite Gneiss Complex, India

ABSTRACT The study analyzes zircons in granites and uraniferous pegmatoid leucosome mobilizates in the Dudhi Group in the northwestern part of the Chhotanagpur Granite Gneiss Complex (CGGC) of Sonbhadra District. The results show that the granites are strongly evolved with low Zr/Hf values and high Hf contents. The Dubha granite and all pegmatoid leucosomes are moderately evolved, with Zr/Hf values between 55 and 25. The Riebeckite granite of Jaurahi exhibits theoretical fractionation, while the Dubha granite doesn’t show fractionation. The study also finds that the Riebeckite granite, Barhaur granite, Dubha granites, and uraniferous pegmatoid leucosomes have inherited zircons with high and fluctuating M values and highly anomalous Zr. The granites and uraniferous pegmatoid leucosomes have formed at high temperature and high-pressure conditions. The study also shows that the chemical ages of the granites and uraniferous pegmatoid leucosomes of the Dudhi Group show chemical age peaks at 3485 Ma, 2974 Ma, 2680 Ma, 2634 Ma, 2509 Ma, 2365Ma, 2250Ma, 2147 Ma, ~1850 Ma, ~1650 Ma, 1000-800 Ma, 200-600 Ma, corresponding to magmatic cores, orogenies, metamorphism, and deformation and supercontinents building and breakups i.e. Sclavia, Ur, Nuna-Columbia to Rodinia, and Pangea-Amasia.