Trace and minor elements in sphalerite from base metal deposits in South China: A LA-ICPMS study

摘要

Laser-ablation ICP mass-spectroscopy has been used to investigate the geochemistry of sphalerite in a range of nine Zn–Pb deposits in South China. The deposits, which are of different ages and belong to different metallogenic provinces, have been assigned to the following genetic types: skarn (Hetaoping, Luziyuan), syngenetic massive sulphide (Dabaoshan, Laochang and Bainiuchang) and Mississippi-Valley-type (Huize, Mengxing, Niujiaotang) based on the features of the ore, even though their origin is heavily debated based on other criteria. The giant Jinding deposit is considered separately. Sphalerite from each genetic class of deposit shows a distinct chemical signature. Sphalerite from the skarn deposits is characterised by elevated, latticebound concentrations of Co and Mn. The distal character of these skarn systems is reflected by the low In content of sphalerite. The three syngenetic massive sulphide deposits feature sphalerite strongly enriched in In, Sn and Ga, whereas the deposits of MVT-type are typically enriched in Ge, Cd, Tl and As. These divergent characters are reflected in absolute element abundances as well as in element ratios. Time-resolved depth profiles for sphalerite from the Chinese deposits confirm the presence of elements such as Co, In, Ge, Ga, and Cd in solid solution, but the dataset expands the understanding of sphalerite mineral chemistry by also indicating that other elements, whose ability to enter the crystal structure of sphalerite has been previously debated (Ag, Sn, Tl, Sb), may also be in solid solution. Sphalerite is a refractory mineral and trace element analysis of sphalerite shows promise as a tracer of ore genesis even in overprinted ores. Systematic work on larger sample suites may help define the geochemical signature of different metallogenic epochs in regions as geologically complex as South China and help resolve the mechanism by which many of the debated ore deposits were formed.