Silurian S-type granite-related W-(Mo) mineralization in the Nanling Range, South China: A case study of the Pingtan W-(Mo) deposit

Abstract

The Pingtan deposit in southwestern Hunan Province is a newly-discovered, large-sized W-(Mo) deposit. This deposit is situated in the northwestern part of the Miao’ershan granite batholith, western Nanling Range. The tungsten mineralization is mainly hosted in biotite monzogranite, and the alteration related to mineralization is controlled by a NE-trending fault zone. In this paper, we present new molybdenite Re–Os and zircon U–Pb ages, zircon Lu–Hf isotope and REE geochemical data, aiming to constrain the W (Mo) mineralization age and ore-hosting granite petrogenesis in the Pingtan W (Mo) deposit. Molybdenite Re–Os dating of eight ore samples yielded a weighted average model age of 427.0 ± 5.4 Ma (MSWD = 0.24). The LA-ICP-MS Zircon U-Pb analysis of two biotite monzogranite yielded 206Pb/238U ages of 430.8 ± 2.4 Ma and 431.0 ± 1.8 Ma, respectively, suggesting that the W-(Mo) mineralization is spatial-temporally associated with the biotite monzogranite. The ore-related granites have high contents of SiO2 and K2O, belong to weakly to strongly peraluminous (A/CNK = 1.00–1.30), and geochemically classified as S-type affinity. Molybdenite Re contents (2.262–7.297 μg/g), zircon εHf(t) (−10.34–−5.87) and 176Hf/177Hf (0.282241–0.282376) values of the biotite monzogranite suggest that the ore-forming materials are predominantly derived from the crust. This is the first identification of tungsten mineralization related to Silurian S-type granites Caledonian granites in the Miao'ershan granite intrusion, indicating Caledonian is an important mineralization period of W in the western part of Nanling Range, South China.