Neoproterozoic granitoids in the eastern Himalayan orogen and their tectonic implications

The Precambrian component and evolutionary history of the Greater Himalayan Sequence (GHS), forming the core of the Himalayan orogen, remain a subject of debate. Here, we report new geochronological and petrochemical data of the Neoproterozoic granitoids that occur as the orthogneisses of the GHS in Cona area, the eastern Himalaya orogen. The zircon U-Pb dating results reveal that these granitoids have crystallization ages of Neoproterozoic of 817-838 Ma, and metamorphic ages of ca. 31 Ma. The petrochemical data show that the granitoids are medium to high-K, peraluminous granodiorite and granite, display geochemical affinities with volcanic arc granitoids. The zircon Hf isotopic compositions show that the granitoids were probably derived from the partial melting of Paleoproterozoic crustal materials. These data, combined with previous results, indicate that an extensive Neoproterozoic magmatic belt may have existed in the Himalayan orogen, and that the Neoproterozoic granitoids resulted from the Andean type orogeny that formed along the northwestern margin of Rodinia supercontinent, and experienced the Cenozoic high-grade metamorphism during the Himalayan orogeny. (C) 2016 Elsevier B.V. All rights reserved.