Monazite and zircon U-Pb and muscovite 40Ar/39Ar geochronology constraints on the timing of magmatism and mineralization in the Huxingshan tungsten deposit, South China

The Huxingshan W deposit (0.21 Mt. WO3 @ 0.3 %) in northeastern Hunan province is located at the western margin of the Jiangnan tungsten belt (JNB), South China. It consists of a series of magma-derived scheelite-quartz-muscovite (SQM) veins in the F1 fault (which contains over 60 % of the W resource), beneath Niutitang Formation (Fm.) carbonate rocks, and above Yijiaqiao Fm. slate (sub-economic), distal from the concealed two-mica granite, which is thought to be responsible for the tungsten mineralization. In this study, we employ LA-ICP-MS zircon and monazite UPb, and muscovite Ar-40/Ar-39 dating to constrain the timing of magmatism and W mineralization at the Huxingshan deposit. Monazite and zircon dating yield coeval ages of 137.6 +/- 0.5 Ma and 138.0 +/- 0.5 Ma, respectively. Our muscovite Ar-40/Ar-39 dating yielded well plateau ages of 132.9 +/- 0.6 Ma, 132.2 +/- 0.6 Ma, 130.7 +/- 0.5 Ma, and 129.7 +/- 0.6 Ma for four representative SQM vein ore samples occurring in the Niutitang Fm. carbonate, F1 fault, and Yijiaqiao Fm. slate, indicating multiple pulses of ore-forming fluid infiltration at Huxingshan. Our age data demonstrate that the two-mica granite emplaced at similar to 137.6 Ma, significantly earlier than the pulsed W mineralization at ca. 132.9-129.7 Ma. The lack of spatial and temporal association precludes any genetic link between them. Thus, we infer that the ore-forming fluids likely originated from undiscovered deep plutons and ascended through the F1 fault. Besides, our reliable ages coincide with the two periods of large-scale Mesozoic magmatism and W mineralization phases in the JNB, with the 137.6 Ma magmatism falling within the first phase (150-135 Ma), while the W mineralization (ca.132.9-129.7 Ma) falls within the second phase (130-125 Ma). Of which, the second phase, including the Huxingshan, Xianglushang, Dongping, and Jianfengpo deposits, are situated in the western JNB and show further potential in this region.