Origin of the Daping gold deposit in the Ailaoshan metallogenic belt, SW China: Insights from geology, isotope geochemistry and geochronology

The Daping gold deposit, the most representative gold deposit in the Ailaoshan metallogenic belt, is located between the southeast Sanjiang region (three rivers: Jinshajiang, Lancangjiang and Nujiang) and the western Yangtze block. Ore bodies in the Daping gold deposit are mainly vein types, hosted in the Late Proterozoic diorite and Silurian limestone, and controlled by NW-trending faults. LA-ICP-MS zircon U-Pb dating of granodiorite yielded a late Eocene age of 36.76 ± 0.38 Ma, constraining the upper limit of the main mineralization. Quartz has δD values ranging from −80‰ to −50.4‰ (average: −63.1‰) and δ18Ofluid values ranging from 7.29‰ to 8.29‰ in the early stage of mineralization; In the late stage, quartz has δD values ranging from −87‰ to −67‰ (average: −77.4‰) and δ18Ofluid values ranging from −0.24‰ to 3.86‰. Carbonate minerals have δ13CPDB and δ18OSMOW values ranging from −2.3‰ to −7.6‰ (average: −5.1‰) and + 9‰ to + 14.9‰ (mean: +12.6‰). The sulfides have a narrow range of δ34S values (+0.2‰ to +6.7‰, average + 3.51‰) in the main stages of mineralization. The 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of the sulfides range from 18.685 to 18.765, 15.653 to 15.728 and 39.014 to 39.280. In general, according to the H-O-C-S-Pb isotopic compositions, the ore-forming fluids are dominated by metamorphic fluids, and the ore-forming fluids and materials might have been mainly derived from the mantle and lower crust, with a small input of wall rock material; they were affected by meteoric water in the late stage of mineralization. Given the regional geology, ore geology, ore-forming fluids, material features, and ore-forming age, the Daping gold deposit can be classified as a typical orogenic gold deposit.