Abstract:

The Tugurige gold deposit is a large-scale gold deposit which is located in the Xing’an-Mongolia Orgenic Belt(XMOB). In order to investigate the source of its ore-forming fluids, a systematic study of the carbon and oxygen isotopes of the deposit was conducted. Results show that the average carbon isotope δ13CV-PDB value of the green calcite is -8.85‰, while the average oxygen isotope δ18OV-SMOW value is 11.65‰. The trends in δ13C and δ18O reflect a transformation of calcite from low to high enrichment levels, indicating two distinct mineralization stages. On the basis of previous research, this study proposes that the origin and composition of ore-forming fluids differ across these stages of mineral deposit formation: In the stage Ⅱ, the ore-forming fluids mainly originated from deep-seated magmatic water, whereas in the stage Ⅲ, seawater-derived carbonates were mixed. Comparing the C-O isotope compositions between the Baoyintu Group and regional formations revealed significantly depleted oxygen isotopes, indicating water-rock interactions during the ore-forming process. Simulations of water-rock reactions indicate that soluble carbon in the ore-forming fluids mainly existed in the form of HCO3-. The simultaneous δ13C and δ18O values of the ore-forming fluid, -9.2‰ and 8‰ respectively, imply that the initial fluid originated from magma and subsequently interacted with marine carbonate rocks in the surrounding rocks during the evolution process. Comprehensive research on the Tugurige gold deposit highlights it typical characteristics of a magmatic hydrothermal gold deposit, with geological features, mineral symbiosis, and fluid characteristics all indicating a close relationship with magmatic hydrothermal activity.

Key words: Tugurige gold deposit, calcite, C-O isotopes, ore-forming fluid, magmatic hydrothermal gold deposit