Fluid evolution and genesis of the Changchunling Pb–Zn deposit in the Southern Great Xing'an Range, Northeast China: Constraints from fluid inclusions and H–O–S–Pb isotopes

Abstract

The southern Great Xing'an Range (SGXR), an important polymetallic metallogenic province in the eastern Central Asian Orogenic Belt (CAOB) in Northeast China, containing numerous ore deposits of Cu, Fe, Pb, Zn, Au, and so forth. The Changchunling Pb–Zn deposit, located in the eastern segment of the SGXR, is primarily hosted by a Permian conglomerate and siltstone unit. The paragenetic sequence of the deposit can be divided into three stages involving arsenopyrite–quartz (stage I); pyrite–sphalerite–galena–quartz (stage II); and barren quartz–carbonate (stage III). Fluid inclusion (FIs) microthermometric studies revealed that only liquid‐rich aqueous inclusions (VL‐type FIs) are observed in the ore‐bearing quartz veins. The FIs of stages I, II, and III yield homogenization temperatures of 190–314, 170–268, and 140–195°C with salinities of 9.73–13.44, 7.86–10.74, and 4.94–5.99 wt% NaCl eqv., respectively. The ore‐forming fluids are characterized by low temperature and low salinity of the H2O–NaCl fluid system. The δ18OH2O and δD values range from −11.8‰ to 0‰ and −120.4‰ to −99.9‰, respectively, indicating that the source of the fluids was primarily derived from a mixed fluid of magmatic water and meteoric water. Fluid cooling, mixing and fluid‐rock reactions were the major ore precipitation mechanisms at Chanchunling. Sulfur‐lead isotopes of pyrite and sphalerite (δ34S = 2.3‰–3.7‰, 206Pb/204Pb = 18.259–18.285, 207Pb/204Pb = 15.544–15.57, and 208Pb/204Pb = 38.136–38.215) indicate that ore metals had a magmatic source. Integrating the available geological, mineralization, fluid inclusion, and H–O–S–Pb isotope evidence, we conclude that the Changchunling Pb–Zn deposit is an epithermal system, which shares many similar features with the regional Pb–Zn polymetallic deposit.