Strongly Peraluminous Highly Fractionated I-Type Granite from Bangong–Nujiang Metallogenic Belt, Tibet: Implications for Continental Evolution and Evaluation of Economic Potentiality

Abstract

The research on highly fractionated granite has significant implications for both the evolution and compositional maturation of the continental crust and metallogenic exploration. As a means of further understanding crustal evolution and promoting ore exploration in the Bangong–Nujiang metallogenic belt (BNMB), we present the petrography, zircon LA–ICP–MS U–Pb age, and Hf isotopic data, along with the whole-rock geochemical and Sr–Nd isotopic composition on Kese highly fractionated granite in the Baingoin area within the BNMB, central Tibet. The results show that Kese granite possesses a zircon U–Pb age of 127.8 ± 1.7 Ma and a relative enrichment in zircon Hf isotopic composition (−12.8~+0.3) with a two-stage Hf model age of 1.2~2.0 Ga. This granite belongs to the high-K calc-alkaline series, characterized by a strongly peraluminous feature, and is enriched in large-ion lithophile elements (LILEs) and Nd isotopes (−7.86~−7.74). The granite was likely to have been derived from the mixed melts derived from 40%~45% juvenile basaltic lower crust, 15%~20% ancient lower, and 40% middle–upper, following intense fractional crystallization processes involving amphibole, biotite, plagioclase, and some accessory minerals during the magma’s evolution. We infer that Kese highly fractionated granite can be formed from the continental collision of the Lhasa–Qiangtang terranes initiated before 128 Ma. The reworking of pre-existing juvenile and ancient crustal materials drove the composition of the northern Lhasa terrane to that of a mature continental crust. Moreover, the distinctive geochemical features have shown that the high degree of differentiation led to intense magmatic–hydrothermal interaction during the formation of Kese granite. A comparison of the geochemical characteristics of mineralized and barren granites suggests that the highly fractionated granites in Baingoin from the BNMB have a high economic potential and are suitable for preliminary exploration of Sn–W-(U) deposits.