Discovery of the large-scale Huangtian scheelite deposit and implications for the structural control of tungsten mineralization in southeastern Yunnan, south China

Abstract

The large-scale Huangtian scheelite deposit represents one of the most important such deposits discovered recently in southeastern Yunnan, China. Results of the geological, metallotectonic, and geochemical investigations indicate that this deposit formed in a magmatic hydrothermal system during the Yanshanian period. Its deposition is controlled by the ore-hosted structure of a secondary fold and by interlayer faults (F0-1 and F0-2), which are linked to the ore-guided structure of a secondary oblique strike-slip fault (F7) associated to the regional Maguan deep fault, and to an EW-trending tectonic zone that represents the main metallogenic tectonic system. The oblique strike-slip structure and the Tianchong granitic porphyries, located along the southern margin of the Laojunshan granite body, are primary ore-controlling structures, which directly controlled the movement of the ore-bearing fluid and its subsequent precipitation within the Huangtian scheelite deposit. The distribution of the orebodies is controlled by a group of metallogenic structural surfaces: the fold and fault systems, as well as a silicon-calcium surface. Silicification, fluoritization, and calcitization are the main hydrothermal alterations observed and exhibited a distinct alteration zonation. The hydrothermal mineralization process can be divided into three stages: the quartz-fluorite-(scheelite-tourmaline) stage, the scheelite-quartz-calcite- (fluorite) stage, and the calcite-pyrite-quartz-scheelite stage. The evolution of the mineralizing fluid proceeded as follows: medium-temperature and low-salinity fluid → medium- to low-temperature and low-salinity fluid → low-temperature and low-salinity fluid. The results concerning oxygen and hydrogen isotopic compositions demonstrate that the ore-forming fluids derived from a magmatic fluid mixed with a small amount of meteoric water. Overall, these features indicate that the Huangtian scheelite deposit represents a medium- to low-temperature magmatic hydrothermal deposit that is obviously controlled by the EW-trending tectonic zone. This study demonstrates the significance of such mineral exploration in similar geological regions.