Decompression-induced fluid immiscibility triggers Triassic gold mineralization at the Maquan deposit, West Qinling, China
Ore Geology Reviews, cilt.193, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 193
- Basım Tarihi: 2026
- Doi Numarası: 10.1016/j.oregeorev.2026.107305
- Dergi Adı: Ore Geology Reviews
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, Geobase, Directory of Open Access Journals, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Anahtar Kelimeler: Carbonate U-Pb dating, Maquan orogenic gold deposit, Ore-forming fluid evolution, West Qinling Orogen
- Karadeniz Teknik Üniversitesi Adresli: Evet
Özet
The Maquan gold deposit, situated within the West Qinling Orogen, is characterized by the presence of carbonate-sulfide veinlets that are hosted within fracture zones of Carboniferous slate. The genesis of these quartz-carbonate-sulfide veins is attributed to infilling and replacement processes, leading to the formation of generated high-grade orebodies. However, the fluid evolution and genetic model of these veins remain poorly constrained, necessitating further research. This study investigates the physicochemical evolution of ore-forming fluids through petrographic analysis, cathodoluminescence, fluid inclusion studies of quartz and calcite, and U-Pb geochronology of calcite. Mineralization is divided into three stages (1) early quartz stage, (2) middle pyrite-quartz-carbonate stage, and (3) main gold-bearing pyrite-arsenopyrite-pyrrhotite-hessite-galena-quartz-carbonate stage. Calcite U-Pb dating constrains the timing, with calcite from stage 2 yielding a lower-intercept age of 222.2 ± 4.0 Ma (n = 53, MSWD = 2.1) and calcite from stage 3 giving 212.4 ± 8.5 Ma (n = 48, MSWD = 3.1). These ages indicate that mineralization consistent with the Late Triassic (ca. 222–212 Ma), synchronous with the collisional setting of the orogen. The analysis of fluid inclusions has provided definitive evidence that the ore-forming fluid belongs to the H2O-NaCl system, which can be grouped into three types: (1) aqueous-rich two-phase H2O-NaCl ± CO2; (2) aqueous-rich two-phase H2O-NaCl ± CO2 ± CH4; and (3) vapor-rich two-phase H2O-NaCl ± CO2. Homogenization temperatures, salinities and pressure: Stage 1, 343–378 °C, 7.17–9.86 wt% NaCl eqv, 143–215 bar; Stage 2, 321–358 °C, 6.16–8.41 wt% NaCl eqv, 110–172 bar; Stage 3, 272–359 °C, 5.71–7.86 wt% NaCl eqv, 54–175 bar. Stage 3 contains coexisting vapor-rich and aqueous-rich fluid inclusions that record fluid immiscibility induced by tectonic pressure release. The ore-forming fluids experienced sustained pressure reduction due to continuous tectonic activity, leading to fluid immiscibility and a significant decrease in temperature and pressure conditions. This process led to the rapid exsolution of CO2 and the destabilization of sulfide-gold complexes, which significantly reduced gold solubility and resulted in gold precipitation.