Insights into ore genesis of the Jinding Zn–Pb deposit, Yunnan Province, China: Evidence from Zn and in-situ S isotopes

摘要

AbstractThe Jinding Zn–Pb deposit located in the Mesozoic-Cenozoic Lanping Basin of southwest China has ore reserves of ?220Mt with an average grade of 6.1% Zn and 1.3% Pb. The mineralization is hosted by sandstone in the Early Cretaceous Jingxing Formation and limestone breccia in the Paleocene Yunlong Formation. Mineralization in both types of host rocks is characterized by a paragenetic sequence beginning with marcasite–sphalerite (Stage 1) followed by pyrite–marcasite–sphalerite–galena (Stage 2), and then galena–sphalerite–pyrite–sulfate–carbonate (Stage 3). Pyrite from these stages have different δ33S compositions with pyrite from Stage 1 averaging ?9.6‰, Stage 2 averaging ?8.9‰, and Stage 3 averaging +0.3‰. Sphalerite hosted by the sandstone has similar δ66Zn values ranging from 0.10 to 0.30‰ in all stages of the mineralization, but sphalerite samples from the limestone breccia-hosted ore show variable δ66Zn values between ?0.03 and 0.20‰. Our data on sphalerite precipitated during the earlier stages of mineralization has a constant δ66Zn value and cogenetic pyrite displays a very light sulfur isotope signature, which we believe to reflect a sulfur source that formed during bacterial sulfate reduction (BSR). The Stage 3 sphalerite and pyrite precipitated from a late influx of metal-rich basinal brine, which had a relatively constant variable δ66Zn isotopic composition due to open system isotope fractionation, and a near zero δ33S composition due to the influence of abiotic thermochemical sulfate reduction from observed sulfates in the host rock.Graphical abstractDisplay OmittedHighlights?We interpret the variability of the zinc and sulfur isotopes, and sources of sulfur.?We demonstrate the precipitation of sulfides in the two types of mineralization.?We provide new insights into ore genesis of MVT deposits in the Lanping Basin.]]>