Geochemistry and geochronology of the Banxi Sb deposit: Implications for fluid origin and the evolution of Sb mineralization in central-western Hunan, South China

摘要

AbstractCentral-western Hunan in South China hosts the largest antimony belt in the world with two types of Sb deposits identified: Sb-Au Woxi-type and Sb only Xikuangshan-type. Banxi is the most representative deposit in the region with vein-type Sb mineralization hosted in Neoproterozoic clastic rocks, stibnite developing in ores, and arsenopyrite mainly occurring in altered country rocks.Trace element contents (including rare earth elements; REE) and isotopic ratios (S, Pb, Sr, Nd, He and Ar) in stibnite and/or arsenopyrite were analyzed to determine the timing of ore formation and to elucidate fluid origin and evolution processes. Most sulfides have high ΣREE contents (45–103ppm), moderate fractionation between LREE and HREE (LREE/HREE=6.38–11.56) and slightly negative Eu anomalies (Eu/Eu*=0.53–0.72). The δ34S values are 3.88–5.81‰ for stibnite and 9.25–11.82‰ for arsenopyrite. The206Pb/204Pb,207Pb/204Pb and208Pb/204Pb ratios range from 18.617 to 18.635, 15.695 to 15.739, and 38.965 to 38.981 for stibnite, and from 18.594 to 18.609, from 15.587 to 15.698, and from 38.893 to 38.926 for arsenopyrite. The87Rb/86Sr and87Sr/86Sr ratios are 0.3016–3.538 and 0.711463–0.717591, respectively for stibnite, and 0.2251–2.214 and 0.711244–0.711565, respectively for arsenopyrite. The147Sm/