The 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 degrees C) and high salinities (54.5-58.4 wt% NaCl equiv) during the skarn stage into mesothermal (260-397 degrees C) and low salinities (1.2-9.5 wt NaCl equiv) during the sulfide stage. The oxygen and hydrogen isotopic compositions (delta O-18(H2O): 2.7-8.8 parts per thousand; SD: -82 to -120%.) suggest that the ore-forming fluids are mixture of magmatic fluids and meteoric water. Sulfur isotopic compositions of the sulfides yield delta S-34 values of -2.3 to 3.2 parts per thousand; 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. (C) 2017 Elsevier B.V. All rights reserved.

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