Participation of the Granite Gneiss in the Crustal Anatexis of the Himalayan Orogeny: Insights From the Zircon U–Pb and Whole‐Rock Geochemistry of the Granitic Gneiss From the Gurla Mandhata Dome

ABSTRACT Granitic gneisses have been widely observed from gneiss domes within the Tethyan Himalaya Sequence and from the Higher Himalayan Crystalline, but whether these granitic gneisses were involved in crustal anatexis is not well constrained. In this paper, sensitive high resolution ion micro‐probe (SHRIMP) zircon U–Pb and Sr–Nd isotopic analysis and geochemical studies were performed on granitic gneiss and muscovite granite from the Gurla Mandhata dome to investigate the potential of granitic gneiss to have participated in the crustal anatexis of the Himalayan orogen. Zircon U–Pb dating of the granitic gneiss reveals Proterozoic cores and oscillatory zoning rims with concordant 206 Pb/ 238 U ages of 483.7 ± 4.8 Ma, which indicate an Early Palaeozoic magmatism event. Zircon U–Pb dating of the muscovite granite reveals Proterozoic cores, oscillatory zoning mantles with 206 Pb/ 238 U ages of 466.8 ± 5.0 Ma. The zircon rims of muscovite granite yield a weighted mean age of 16.0 ± 0.2 Ma, representing the time of the anatectic event. The Sr–Nd isotopic compositions and geochemical data of the muscovite granite indicate that the muscovite granite may have been derived from fluid‐fluxed melting of muscovite from the Higher Himalayan Crystalline (including metasedimentary rocks and granitic gneisses). Thus, we believe that the Early Palaeozoic granitic gneiss participated in the crustal anatexis of the Himalayan orogen.