矿床地球化学国家重点实验室知识库

The Shimensi deposit (Northern Jiangxi, South China) is a recently discovered super-large tungsten deposit. Muscovite Ar-40/Ar-39 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 Ar-40/Ar-39 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 (delta S-34(minerals) = -3.0 parts per thousand to 1.1 parts per thousand, average -1.3 parts per thousand; delta S-34(H2S) = -4.5 parts per thousand to + 1.2 parts per thousand, average -1.8 parts per thousand) of the Shimensi ore-forming fluids indicate that the sulfur was mainly magmatic-derived. The calculated and measured oxygen and hydrogen isotopic compositions (delta O-18(H2O) = 4.1 parts per thousand to 6.7 parts per thousand, delta D = -62.7 parts per thousand to 68 parts per thousand) 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.