ReOs and S isotopic constraints on the origins of two mineralization events at the Tangdan sedimentary rock-hosted stratiform Cu deposit, SW China

摘要: Abstract The Tangdan stratiform Cu deposit in the Kangdian region of South China is hosted sedimentary rocks late Paleoproterozoic to early Mesoproterozoic Dongchuan Group. Orebodies mainly occur dolostone and black shale above a thick sequence hematitic sandstone siltstone. Mineralization consists bedding-parallel ores, with minor amounts discordant vein-type ores. Both ores are composed bornite chalcopyrite chalcocite digenite, associated gangue minerals including ankerite, dolomite, calcite, quartz. Cu-sulfides from contain ~ 122–293 ppb Re, much higher than those (~ 0.6–14 ppb Re). They have highly radiogenic Os Re model ages ranging 1413 1457 Ma weighted mean age 1432 ± 19 Ma (2σ, MSWD = 0.30), which within uncertainty agreement isochron 1401 ± 30 Ma MSWD = 0.67) 1397 ± 71 Ma MSWD = 0.22) using 187 Re/ 188 versus Os/ regression, respectively. In contrast, sulfides did not yield meaningful due extremely low concentrations Os. However, studies shown that were likely formed at ~ 1700 Ma during diagenesis host strata. Sulfides δ 34 S values − 15‰ − 8‰, significantly lower (− 3‰ + 10‰), suggesting organic matter may been involved formation Contrasting isotopes suggest two types different ore-forming fluids. We propose precipitated basinal fluids evolution rift basin, whereas younger thermal event hydrothermal interacted overlying account for high negative values. This study demonstrates can be used origin system.