Geology, isotope geochemistry, and geochronology of the Huamuqing carbonate-hosted Pb–Zn deposit, southwest China

Abstract

As a carbonate-hosted deposit, the Huamuqing Pb–Zn deposit is situated in the western margin of the Yangtze Block. The strata-bound, irregular or vein-type Pb–Zn orebodies of the Huamuqing Pb–Zn deposit are mainly hosted by carbonate rocks of the Sinian Dengying Formation or Cambrian Meishucun Formation. Ores metallic minerals include mainly sphalerite, galena, and pyrite, whereas non-metallic minerals include mainly quartz and calcite. The alteration/mineralization can be divided into three stages: (I) the pyrite-quartz stage, (II) the polymetallic sulfide-quartz stage, and (III) the pyrite-calcite stage. The C–O isotopes of stage III hydrothermal calcite and multi-isotopes (S, Pb, Rb, Sr) of stage II sulfides were analyzed to constrain the ore-forming material source and mineralization timing at Huamuqing. The ranges of δ13CPDB and δ18OSMOW values for the stage III calcites are from − 0.641 to + 0.180‰ and + 17.542 to + 18.443‰, respectively. This suggests that the carbon of stage III was mainly derived from the Sinian dolostone, and the O isotope signatures of stage III were probably in connection with water/rock (W/R) interactions between the δ18O-depleted fluids and δ18O-enriched Sinian dolostone. The stage II sulfide δ34SCDT values vary from + 13.037 to +20.696‰, indicating that the reduced sulfur was originated mainly from Sinian to Triassic evaporites. The stage II sulfide 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ranges are from 18.184 to 18.393, 15.575 to 15.691, and 38.325 to 38.436, respectively. This demonstrates multiple Pb sources, which may have included sedimentary rocks, basement rocks, and basalts. Initial 87Sr/86Sr ratios of eight sphalerite samples range from 0.70815 to 0.71399, indicating that the ore fluids most probably came from or percolated through basement rocks, basalts, and sedimentary rocks. The mineralization timing was sphalerite Rb–Sr dated to be Late Triassic (204 ± 2 Ma), reflecting the Huamuqing deposit formed during late Indosinian. Hence, the Huamuqing deposit is a carbonate-hosted, thrust fault–controlled epigenetic Pb-Zn deposit that has a mixed source of ore-forming metals and ore-forming fluids.