Abstract:

The  Mineralized Zone NoI at the Halasu copper deposit in Qinghe County is situated in Kalaxiangeer porphyry copper belt. The copperbearing minerals mainly occur in the form of heterogeneous gobbets, veinlets and veinletdisseminated in the granodiorite porphyry, quartz diorite porphyry, basalt and pyroxene phenocrysts basalt. Two types of fluid inclusions, namely H₂O-NaCl and H₂O-CO₂ (±CH4/N2)NaCl types, have been recognized in quartz and calcite from the ore. Homogenization temperatures of fluid inclusions vary from 120 to 431  ℃, with three temperature peaks at 390,290 and 190 ℃. Salinity ranges from 053% to 6676 ％ NaCleqv, with four peaks at 19.5％ NaCleqv, 12.5％ NaCleqv, 9.5％ NaCleqv and 1.5％ NaCleqv. Ore fluid densities range from 055 to 1.11 g/cm3. The δ18OSMOW values of quartz and calcite in the ore vein range from 2.9‰ to 12.3‰ with corresponding δ18Ofluid values of -5.81‰ to 4.83‰ and δD values of fluid inclusions between -129‰ and -80‰. The isotopic data imply that the oreforming fluids of the Halasu copper deposit were mainly derived from magmatic fluids, with some contributions from meteoric water. The δ13CPDB values of calcite define a narrow range of -2.4‰ to -1.4‰ and δ18OSMOW values range from 8.3‰ to 9.2‰ indicating that the carbon in the ore fluids was mainly derived from magma. ReOs dating was performed on molybdenite from molybdenite vein, which yielded isochron ages of (378.3±5.6) Ma. This isochron age is coincident with the age of 381375 Ma from granodiorite porphyry pluton within error range. Early mineralization formed in the Middle Devonian, which was closely related to porphyry systems. The LateMiddle tectonicmagmatichydrothermalmineralization overlapped the early porphyry mineralization in the Halasu copper deposit.

Key words: Re-Os age, fluid inclusions, stable isotopes, copper deposit, Halasu, Xinjiang