Geophysical investigations of the geology and structure of the Pangushan-Tieshanlong tungsten ore field, South Jiangxi, China-Evidence for site-selection of the 2000-m Nanling Scientific Drilling Project (SP-NLSD-2)

The Pangushan-Tieshanlong tungsten ore field, located in the center of southern Jiangxi Province, eastern Nanling region, contains many granitic plutons, both exposed and concealed, and hosts numerous tungsten-polymetallic ore deposits. Despite many previous geological studies, the deep geology and structure of the field are poorly known because few geophysical measurements have been undertaken. In this study, we carried out a variety of geophysical measurements, including gravity, magnetic field detection, magnetotelluric sounding (MT) and high-resolution seismic reflection to better outline the nature of the ore field and to aid in site selection for the 2000-m Nanling Scientific Drilling Project (SP-NLSD-2), to be carried out by the Chinese SinoProbe Program. Four granitic intrusives, the Tangcun, Pangushan, Huangsha and Bai'e plutons, crop out independently at the surface but were found to be parts of a large batholith at depth. The Tangcun composite pluton, which at the surface consists chiefly of Caledonian granite and minor Early Yanshanian intrusive material, was found to be chiefly Early Yanshanian granite concealed beneath the lower part of the Caledonian granite. The Bai'e pluton initially decreases in size with depth and then expands as it merges with the major batholith. The Pangushan and Huangsha plutons are domes on the inferred batholith. Four granitic magma channels and a considerable number of faults have been identified. Due to its favorable geological conditions, the top of the Pangushan pluton is predicted to be the best candidate for ore prospecting. It is basically a granite cupola with many cross-cutting and parallel faults. In addition, it is characterized by a high gravity anomaly, a high magnetic anomaly and locally a low electrical resistivity anomaly.