Geology, fluid inclusion and isotope constraints on ore genesis of the post-collisional Dabu porphyry Cu–Mo deposit, southern Tibet

摘要: Abstract The Dabu Cu-Mo porphyry deposit is situated in the southern part of Lhasa terrane within post-collisional Gangdese copper belt (GPCB). It one several deposits that include Qulong and Zhunuo deposits. processes responsible for ore formation can be divided into three stages veining: stage I, quartz–K-feldspar (biotite) ± chalcopyrite ± pyrite, II, quartz–molybdenite ± pyrite ± chalcopyrite, III, quartz–pyrite ± molybdenite. Three types fluid inclusions (FIs) are present: liquid-rich two-phase (L-type), vapor-rich (V-type), solid bearing multi-phase (S-type) inclusions. homogenization temperatures FIs from I to III ranges 272–475 °C, 244–486 °C, 299–399 °C, their salinities vary 2.1 49.1, 1.1 55.8, 2.9 18.0 wt% NaCl equiv., respectively. coexistence S-type, V-type L-type quartz II with similar but contrasting salinities, indicate boiling major factor controlling metal precipitation deposit. ore-forming fluids this characterized by high temperature salinity, they belong a H2O–NaCl magmatic–hydrothermal system. H–O–S–Pb isotopic compositions metals came primarily magmatic source linked Miocene intrusions Sr/Y ratios, other GPCB. forming were rich Na Cl, derived metamorphic dehydration subducted oceanic slab through which NaCl-brine or seawater had percolated. inheritance ancient subduction-associated arc chemistry, without shallow level crustal assimilation and/or input meteoric water, was generation fertile magma, as well CO2-poor halite-bearing associated estimated mineralization depths Qulong, 1.6–4.3 km, 0.5–3.4 km 0.2–3.0 km, respectively, displaying gradual decrease eastern western Gangdese. Deep accounted giant-sized deposit, because exsolution aqueous large fraction water chlorine deep pressure systems extract more melts than those formed systems. However, small-sized explained single event additional replenishment S, metal, thermal energy. In addition, conditions Cu–Mo GPCB comparable Cu ± Au ± Mo subduction-related continental island arcs, differ Mo Dabie-Qinling collisional orogens. depth features primary magma two controls on ore-fluid these