Neoproterozoic tungsten mineralization and associated granitic magmatism in the western Yangtze Block, South China: Mineralization age, petrogenesis and geodynamic implications

Abstract

Neoproterozoic granitic magmatism and associated mineralization in the western Yangtze Block (WYB), South China, records the assembly and breakup of the Rodinia supercontinent, making it a key window for understanding the tectonic evolution and associated dynamic process of the Rodinia supercontinent. In this paper, we present an integrated study on petrology, petrography, geochemistry, zircon U-Pb-Hf isotope, vesuvianite U-Pb and muscovite Rb-Sr geochronology for the W-rich granitic plutons (Xiacun and Shunhe plutons) and ore-bearing granitic dikes from the newly discovered Neoproterozoic Huili tungsten deposit in the WYB. Our objective is to provide vital constraint on the mineralization age and metallogenic geodynamic setting of the Neoproterozoic Huili tungsten deposit in the WYB. The ore body is characterized by skarn-type and quartz vein-type mineralization with main ore mineral of scheelite and gangue minerals of vesuvianite, muscovite and diopside. Zircon U-Pb dating indicates the granitic plutons and granitic dikes emplaced at ca. 845 Ma and 824 Ma, respectively. The vesuvianite U-Pb age and muscovite Rb-Sr isochron age are ca. 826–818 Ma and 822 Ma, respectively, indicating the tungsten mineralization was coeval with the crystallization of the granitic dikes. Petrology and geochemical studies reveal that the granitic dikes and the Shunhe pluton are highly fractionated S-type granite, while the Xiacun pluton belongs to unfractionated S-type granite. The granitic plutons have uniform and weakly enriched zircon Lu-Hf isotopes (εHf(t) = -3.08 ∼ -0.22), while the granitic dikes have varied zircon Hf isotopes (εHf(t) = -10.57 ∼ 4.64). Zircon Lu-Hf isotopes, as well as their varied whole-rock geochemical compositions, indicate that the Xiacun and Shunhe granitic plutons mainly originate from partial melting of Middle Paleoproterozoic crust, while the ore-bearing granitic dikes are mainly derived from the melting of heterogeneous Middle Paleoproterozoic crust, followed by significant fractional crystallization of feldspar, biotite and accessory minerals. Petrological, geochronological and geochemical data compilation reveals that the studied ca. 845 Ma granitic plutons and ca. 824 Ma W-mineralized granitic dikes were formed in a progressive subduction and a back-arc extension setting, respectively, and the Neoproterozoic back-arc extension-related granitic magmatism during the breakup of Rodinia supercontinent may be beneficial for the tungsten mineralization.