LA-ICP-MS analyses of trace elements in base metal sulfides from carbonate-hosted Zn-Pb deposits, South China: A case study of the Maoping deposit

摘要

The Sichuan-Yunnan-Guizhou metallogenic province (SYGMP) contains over 400 different size Zn-Pb deposits hosted in late Ediacaran to early Permian carbonate sequences and accounts for approximately 27% of the total Zn-Pb production in China. The Maoping deposit is a typical example that is not only mainly hosted in two different strata i.e., Devonian Zaige Formation (Fm.) and Carboniferous Baizuo Fm. but also shows a close spatial relationship with the Emeishan flood basalt. However, its ore genesis is poorly constrained. In this study, LA-ICPMS trace element maps and spot analyses were generated on the sphalerite and galena selected from Maoping, aiming to establish tarce element partitioning behavior in co-crystallized sphalerite-galena, constrain the possible controls on the variation of trace element, and provide new insights into the ore genesis. The results show that Mn, Cd, Fe, Ge, Cu, In and Sn concentrations in sphalerite are higher than coexisting galena, yet galena is the preferential host for As, Ag, Sb, Tl, and Bi. The sphalerite from Carboniferous Baizuo Fm. is more concentrated in Cu, Ge, As, Ag and Sb than that of Devonian Zaige Fm., but has comparable trace element compositions to many other SYGMP Zn-Pb deposits hosted within the same sediment strata such as Huize and Tianqiao. This difference may be thought to have been controlled by host rock chemical composition with limited effect by physicochemical conditions and/or source(s) of metal elements. Sphalerite from the Maoping deposit is characterized by enrichments in Cd, Ge but depletions in Mn, Fe, In and Co, which are markedly distinct from that of the magma-related hydrothermal system (e.g., high-temperature (high -T) magmatic-hydrothermal, VMS and skarn deposits) but consistent with that of MVT deposits. Based on these results, together with the geological and geochemical features of the deposit, we considered that the Maoping Zn-Pb deposit belong to a MVT deposit.