Abstract: The Daolundaba deposit in the southern Great Xingan Range, Inner Mongolia is a medium-sized copperwolframtinsilver deposit. Ore bodies are hosted in faulted and shattered zones and host rocks are mainly the Permian sandstone and slate with minor amounts of Variscan biotite granite. The mineralization process can be divided into four stages: quartzfluoritemuscovitetourmalinecassiteritewolframite (stage Ⅰ), quartzfluoritewolframitechalcopyritearsenopyritepyrrhotite (stage Ⅱ), quartzfluoritechalcopyritepyritepyrrhotitesilver-bearing mineral (stage Ⅲ), and calcitefluoritepyrite (stage Ⅳ) stages. In this study, three types of fluid inclusions (FIs) have been distinguished in quartz, fluorite, and calcite veins including liquid-rich (WL type), gas-rich (WG type), and daughter mineral-bearing (S type) inclusions. The FIs in both stages Ⅰ and Ⅱ were  of WL-, WG-, and S-types, with homogenization temperatures and salinities varying from 309 to 389 ℃ and from 6.2 to 46.3 wt.% NaCleqv. in stage Ⅰ, respectively, and from 242 to 339 ℃ and from 5.3 to 41.4 wt.% NaCleqv. in stage Ⅱ, respectively. The FIs in stage Ⅲ contained mainly WL- and S-types, with  homogenization temperatures and salinities ranging from 153 to 268 ℃ and from 3.5 to 35.4 wt.% NaCleqv., respectively. Only WL-type FIs occurred in stage Ⅳ, and the homogenization temperatures and salinities varied from 114 to 188 ℃ and from 2.1 to 7.6 wt.% NaCleqv., respectively. In general, the ore-forming fluids of stages Ⅰ/Ⅱ, Ⅲ and Ⅳ were characterized by moderatehigh temperature/high salinity, moderatelow temperature/high salinity and low temperature/low salinity fluids, respectively. The δ18OH2O and δD values of the ore-forming fluids were between  -10.0‰ and 7.2‰, -127‰ and -81‰, respectively, demonstrating that, from the early to late stages, the ore-forming fluids of the Daolundaba deposit gradually evolved from magmatic fluids to mixtures of meteoric and magmatic waters. The δ34S values ranged from -7.4‰ to -1.2‰, indicating S came primarily from deep magma. The Pb isotopic composition (μ values 9.39.7) also indicated that Pb was mainly derived from the magma formed by partial melting of orogenic material. Thus, both S and Pb isotopic data suggest that the ore-forming materials originated mainly from magma. Overall, our study shows that the multi-stage boiling and mixing of the ore-forming magmatic fluids with meteoric water were the dominant mechanism for ore deposition.

Key words:  fluid inclusion, H-O-S-Pb isotopes, copper-polymetallic deposit, Daolundaba, southern Da Hinggan Ling