Genesis of quartz veinlets in the Pangushan W-Bi deposit, South China: Implications for exploration of wolframite quartz vein-type mineralization

Abstract

Ore veins exhibit uniform dipping directions in a remarkable number of wolframite quartz vein-type (WQV-type) deposits. Discussions on whether their reversely dipping ore veins occur will better target this type of blind mineralization. The Pangushan W-Bi deposit is a famous large-scale WQV-type deposit located in the eastern Nanling region, South China. It yielded three groups of south dipping ore veins, namely, Southern Group (SG), Middle Group (MG), and Northern Group (NG). Recently, two groups of north dipping quartz veinlets (QV1 and QV2) were discovered in the ground to the south of SG. Whether QV1 and QV2 are indications of concealed north dipping ore veins remains unknown. This study carried out a geological profile survey of QV1 and QV2, and implemented element compositions, fluid inclusion temperature, and H-O isotope analysis. The dipping angle of QV1 is ~78°, and that of QV2 is 60°–70°, close to those of SG and MG, respectively. They contain quartz, wolframite, molybdenite, and muscovite. The maximum contents of their ore-forming elements are 1412 ppm W, 52.7 ppm Bi, and 1442 ppb Te, which are considerably higher than those in their surrounding rocks. The homogenization temperature, salinity, δDV-SMOW, and δ18OH2O of their fluid inclusions in quartz concentrate within 220 °C–280 °C, 8%–15%, −78.7‰–−86.1‰, and −1.2‰–1.62‰, respectively, indicating that QV1 and QV2 are post magmatic hydrothermal products evolved from granitic magma. They are forecast to convert into corresponding two groups (G1 and G2) of north dipping ore veins downward. Moreover, the third group (G3) of north dipping ore veins may occur to the south of G2. The three north dipping groups (G1, G2, and G3) and three south dipping groups (SG, MG, and NG) may be approximately symmetrical and centered at the buried granite tuber.