Muscovite 40Ar/39Ar Age and H-O-S Isotopes of the Shimensi Tungsten Deposit (Northern Jiangxi Province, South China) and Their Metallogenic Implications

The Shimensi deposit (Northern Jiangxi, South China) is a recently discovered super-large tungsten deposit. Muscovite 40Ar/39Ar dating yielded a plateau age of 145.7 ± 0.9 Ma, with normal and inverse isochronal ages being 145.4 ± 1.4 Ma and 145.3 ± 1.4 Ma, respectively. The muscovite 40Ar/39Ar age, which can represent the mineralization age, coincides well with the published zircon U–Pb ages (143–148 Ma) of the ore-hosting granites, which indicates that the tungsten mineralization was syn-magmatic. The new age reported here confirms that the Shimensi tungsten deposit is part of a large Early Cretaceous (147–136 Ma) tungsten-polymetallic belt in South China. Measured and calculated sulfur isotopic compositions (δ34Sminerals = −3.0‰ to 1.1‰, average −1.3‰; δ 34 S H 2 S = −4.5‰ to +1.2‰, average −1.8‰) of the Shimensi ore-forming fluids indicate that the sulfur was mainly magmatic-derived. The calculated and measured oxygen and hydrogen isotopic compositions ( δ 18 O H 2 O = 4.1‰ to 6.7‰, δD = −62.7‰ to −68‰) of the ore-forming fluids indicate a dominantly magmatic source with a meteoric water input. Oxygen isotopic modelling of the boiling/mixing processes indicates that the Shimensi tungsten mineralization was caused mainly by fluid mixing of magmatic hydrothermal fluid with meteoric water.