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

摘要

The Shimensi deposit (Northern Jiangxi, South China) is a recently discovered super-large tungsten deposit. Muscovite 40 Ar/ 39 Ar 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 40 Ar/ 39 Ar 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 (???′ 34 S minerals = ?￠????3.0?￠???° to 1.1?￠???°, average ?￠????1.3?￠???°; ???′ 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 ( ???′ 18 O H 2 O = 4.1?￠???° to 6.7?￠???°, ???′D = ?￠????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.