Geology and geochronology of the Xingfengshan deposit, Jiangnan orogenic belt, South China: Implication for intrusion-related Au–W mineralization

The Xingfengshan is a slate-hosted Au–W deposit in the central part of the Jiangnan orogenic belt, South China. It comprises stratiform skarns and sheeted quartz veins, and both two types of mineralization have W and Au metal association. In this study, systematic geological investigation, together with TESCAN Integrated Mineral Analyzer (TIMA), and biotite ⁴⁰Ar/³⁹Ar analyses were performed to determine the geological features and mineralization age. Formation of skarn stage (Stage 1) is represented by three substages: (I) prograde skarn, (II) retrograde skarn, and (III) quartz–sulfide. Scheelite and minor native gold formed during substage II and III, respectively. TIMA results confirm the coexistence of skarn minerals such as garnet, pyroxene, actinolite, and biotite, and scheelite. Sheeted Au–W quartz veins (Stage 2) crosscutting skarns contain auriferous arsenopyrite, scheelite, pyrrhotite, quartz, and display coexistence of Au (arsenopyrite), W (scheelite), and biotite. Post-ore barren quartz veins (Stage 3) are mainly composed of quartz, muscovite and tourmaline. ⁴⁰Ar/³⁹Ar dating results of biotite from retrograde skarn and sheeted veins constraining the formation ages are 215.0 ± 1.7 Ma and 211.9 ± 1.7 to 209.8 ± 2.1 Ma, respectively. These ages are broadly contemporaneous with the surrounding granitoid intrusion (218.7 ± 1.5 to 204.5 ± 2.8 Ma). It is likely that mineralizing fluids responsible for Au–W mineralization are of magmatic in origin. Considering the temporal and spatial association of the widespread Late Triassic magmatism and Au–W mineralization in the central Jiangnan orogenic belt, an intrusion-related Au system could be established for genesis of the Xingfengshan Au–W deposit.