Genesis of the Anle lead−zinc deposit in northwestern Yunnan Province: Evidence from in-situ sulfur isotopic and trace elements of sphalerite

Objective The Anle lead−zinc deposit in Shangri−La County, northwestern Yunnan Province, SW China, occures in the Upper Cambrian carbonate rock formation interbedded with clastic rocks, and the genesis of this deposit remains unclear.

Methods  Based on geological investigation and microfabric analysis, the origin of ore-forming fluid is traced by in-situ sulfur isotopic, major and trace elemental compositions of sphalerites, and the ore genesis was discussed.

Results The results show that the Anle lead−zinc deposit Based on geological investigation and microfabric analysis, the origin of ore-forming fluid is traced by in-situ sulfur isotopic, major and trace elemental compositions of sphalerites, and the ore genesis was discussed. The orebodies show the ore textures of massive, brecciated, banded, disseminated, and veinlet in shape, respectively, and present obvious spatial zonation of vent facies, proximal facies and distal facies ores, which is typical of a subseafloor sedimentary exhalative deposit. Sphalerites in brecciated, massive and banded ores are all anhedral, characterized by enrichment in Mn, In, Cd, and Fe, and depletion of Co, Ni, and Cu. The δ³⁴S_V−CDT values of the sphalerite range from −0.8‰ to 10.57‰. Combined with the variations in the ratios of Cd/Fe, Cd/Mn, along with Ge content, the sulfur in the ore−forming fluids may originates from the reduction of sulfate in paleo−seawater, and involved influx of a magmatic−related hydrothermal solution. The Fe and Zn content, Ge/In, Ga/In, and Ga/Ge ratios, along with lg(Ga/Ge) −T diagram plot of sphalerites indicate that it is formed under the medium and low temperature condition of 160~220℃.

Conclusions Therefore, the Anle lead−zinc deposit is inferred to be a sedimentary exhalative (SEDEX) -type deposit, and the mineralization contribution of magmatic hydrothermal fluids cannot be excluded. This result significantly expands the exploration space of this orefield and its adjacent areas, and also provides a new insight into understanding the regional geological evolution.