Multiple dating and tectonic setting of the Early Cretaceous Xianglushan W deposit, Jiangxi Province, South China

Abstract

The Xianglushan W deposit in northwestern Jiangxi Province, South China, is one of numerous large-size W deposits along the northern margin of the Jiangnan Massif. The deposit comprises lenticular and stratiform-like orebodies, mainly along the contact between argillaceous limestone of the Cambrian Yangliugang Formation and a biotite granite pluton. The mineralization is zoned from proximal W greisen within the cupolas of the biotite granite, through W skarn and sulfide-scheelite bands near the pluton, to distal quartz-sulfide ± scheelite veins. The granitic pluton and an aplitic dyke in the mining area contain zircon grains with U–Pb ages of 123.8 ± 0.8 Ma and 117.3 ± 1.7 Ma, respectively. Six molybdenite samples collected from skarn ores yielded a Re–Os weighted mean age of 125.5 ± 0.7 Ma, and muscovite separates from greisen ores yielded a 40Ar/39Ar plateau age of 122.8 ± 0.78 Ma. The molybdenite Re–Os and muscovite Ar–Ar ages are consistent with the zircon U–Pb age of the hosting granite. The Xianglushan deposit is formed by an Early Cretaceous W–dominated polymetallic ore-forming event in the Jiangnan porphyry–skarn W belt. Zircon from biotite granites in the Xianglushan deposit has negative εHf(t) values, generally from − 5.7 to − 3.1, with corresponding two-stage Hf model ages of 1363–1218 Ma, reflecting derivation of magmas from a crustal source. Molybdenite has Re contents from 12.12 to 22.77 ppm, indicative of a mixed crustal-mantle source, but with a dominantly crustal component. A compilation of precise ages for magmatism and mineralization in the Jiangnan porphyry–skarn W belt shows that there are two stages of mineralization at 150–135 Ma and 130–120 Ma, respectively. Integrated with published data, our results suggest that the Xianglushan W deposit formed in an extensional tectonic setting during the Early Cretaceous.