Isotope and fluid inclusion geochemistry of the Cangyuan Pb-Zn-Ag polymetallic deposit in Yunnan, SW China

摘要

Graphical abstractDisplay OmittedHighlights?The ore forming fluids of the deposit are CO2-bearing, NaCl-H2O, magmatic fluids. It evolved from high temperature and salinity to mesothermal and low salinity during the sulfide stage.?The metals were transported as chloride complex and precipitated due to cooling, fluid mixing, decompression and boiling.?Sulfur isotopic compositions indicate a magmatic source for the sulfur.?Lead compositions suggest that the metals in the ore-forming fluids are derived from the mantle mixed with the crust.AbstractThe Cangyuan Pb-Zn-Ag polymetallic deposit is located in the Baoshan Block, southern Sanjiang Orogen. The orebodies are hosted in low-grade metamorphic rocks and skarn in contact with Cenozoic granitic rocks. Studies on fluid inclusions (FIs) of the deposit indicate that the ore-forming fluids are CO2-bearing, NaCl-H2O. The initial fluids evolved from high temperatures (462–498°C) and high salinities (54.5–58.4 wt% NaCl equiv) during the skarn stage into mesothermal (260–397°C) and low salinities (1.2–9.5 wt% NaCl equiv) during the sulfide stage. The oxygen and hydrogen isotopic compositions (δ18OH2O: 2.7–8.8‰; δD: ?82 to ?120‰) suggest that the ore-forming fluids are mixture of magmatic fluids and meteoric water. Sulfur isotopic compositions of the sulfides yield δ34S values of ?2.3 to 3.2‰; lead isotopic compositions of ore sulfides are similar to those of granitic rocks, indicating that the sulfur and ore-metals are derived from the granitic magma. We propose that the Cangyuan Pb-Zn-Ag deposit formed from magmatic hydrothermal fluids. These Cenozoic deposits situated in the west of Lanping-Changdu Basin share many similarities with the Cangyuan in isotopic compositions, including the Laochang, Lanuoma and Jinman deposits. This reveals that the Cenozoic granites could have contributed to Pb-Zn-Cu mineralization in the Sanjiang region despite the abundance of Cenozoic Pb-Zn deposits in the region, such as the Jingding Pb-Zn deposit, that is thought to be of basin brine origin.]]>