Constraints of multiple dating of the Qingshan tungsten deposit on the Triassic W(-Sn) mineralization in the Nanling region, South China

Abstract

The Qingshan tungsten deposit is a quartz-vein type ore deposit in the Nanling region, South China, and consists of orebodies along the contact between Ordovician sandstone and the Mesozoic Keshuling granitic pluton. There are more than 54 ore-bearing quartz veins, controlled by NE- and NNE-trending faults. The principal ore minerals are wolframite and cassiterite with subordinate molybdenite, which formed dominantly during the early oxide and oxide-sulfide ore-forming stage together with extensive greisenization adjacent to the W-bearing quartz veins. The gangue minerals are mainly quartz and muscovite. Zircon grains from the Keshuling pluton have a U-Pb age of 231.9 ± 1.0 Ma (MSWD = 4.0). Molybdenite separates from the ore-bearing quartz veins have a well-defined 187Re/187Os isochron age of 228.7 ± 2.5 Ma (MSWD = 0.36), with model ages ranging from 227.6 ± 3.3 to 229.7 ± 3.2 Ma. Hydrothermal muscovite from the greisen between the granite and country rocks has a flat 40Ar/39Ar plateau age spectra, yielding a 40Ar/39Ar plateau age of 229.4 ± 1.4 Ma (MSWD = 0.34). The U-Pb, Re-Os and 40Ar/39Ar ages are nearly identical within analytical uncertainties, and these ages, together with the field relationships, provide tight constraints on the W(-Sn) mineralization at around 230 Ma. This multiple dating study reflects that the duration of the hydrothermal activity could be less than several million years. Our new results suggest that the Triassic large-scale W(-Sn) mineralization occurred throughout the Nanling region.