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The Wulasigou Cu-Pb-Zn deposit,located 15 km northwest of Altay city in Xinjiang,is one of many Cu-Pb-Zn polymetallic deposits in the Devonian Kelan volcanic-sedimentary basin in southern Altaids.Two mineralizing periods can be distinguished:the marine volcanic sedimentary PbZn mineralization period,and the metamorphic hydrothermal Cu mineralization period,which is further divided into an early bedded foliated quartz vein stage(Q1) and a late sulfide-quartz vein stage(Q2) crosscutting the foliation.Four types of fluid inclusions were recognized in the Q1 and Q2 quartz from the east orebodies of the Wulasigou deposit:H_2O-CO_2 inclusions,carbonic fluid inclusions,aqueous fluid inclusions,and daughter mineral-bearing fluid inclusions.Microthermometric studies show that solid CO_2 melting temperatures(T_(m,CO2)) of H_2O-CO_2 inclusions in Ql are from-62.3℃ to-58.5C,clathrate melting temperatures(T_(m,clath)l) are from 0.5 C to 7.5 C,partial homogenization temperatures(T_(h,CO2)) vary from 3.3℃ to 25.9℃(to liquid),and the total homogenization temperatures(T_(h,tot)) vary from 285℃ to 378℃,with the salinities being 4.9%-15.1%NaCl eqv.and the CO_2-phase densities being 0.50-0.86 g/cm~3.H_2O-CO_2 inclusions in Q2 have T_(m,CO_2) from-61.9℃ to-56.9℃,T_(m,clath)from 1.3℃ to 9.5℃,T_(h,CO2) from 3.4℃ to 28.7℃(to liquid),and T_(h,tot) from 242℃ to 388℃,with the salinities being 1.0%-15.5%NaCl eqv.and the CO_2-phase densities being 0.48-0.89 g/cm~3.The minimum trapping pressures of fluid inclusions in Q1 and Q2 are estimated to be 260-360 MPa and180-370 MPa,respectively.The δ~(34)S values of pyrite from the volcanic sedimentary period vary from2.3‰ to 2.8‰(CDT),and those from the sulfide-quartz veins fall in a narrow range of-1.9‰ to 2.6‰(CDT).The δD values of fluid inclusions in Q2 range from-121.0‰ to-100.8‰(SMOW),and theδ~(18)O_(H2O) values calculated from δ~(18)O of quartz range from-0.2‰ to 8.3‰(SMOW).The δD-δ~(18)O_(H2O)data are close to the magmatic and metamorphic fields.The fluid inclusion and stable isotope data documented in this study indicate that the vein-type copper mineralization in the Wulasigou Pb-Zn-Cu deposit took place in an orogenic-metamorphic enviroment.
The Wulasigou Cu-Pb-Zn deposit, located 15 km northwest of Altay city in Xinjiang, is one of many for Cu-Pb-Zn polymetallic deposits in the Devonian Kelan volcanic-sedimentary basin in southern Altaids. Two mineralizing periods can distinguished: the Wulasigou Cu- marine volcanic sedimentary PbZn mineralization period, and the metamorphic hydrothermal Cu mineralization period, which is further divided into an early bedded foliated quartz vein stage (Q1) and a late sulfide-quartz vein stage (Q2) crosscutting the foliation. Flow types of fluid inclusions were recognized in the Q1 and Q2 quartz from the east orebodies of the Wulasigou deposit: H_2O-CO_2 inclusions, carbonic fluid inclusions, aqueous fluid inclusions, and daughter mineral-bearing fluid inclusions. Microthermometric studies show that solid CO_2 melting temperatures (T_ (m , CO2)) of H 2 O-CO 2 inclusions in Ql are from-62.3 ° C. to-58.5 ° C., clathogenic melting temperatures (T_ (m, clath) 1) are from 0.5 C to 7.5 C, partial homogenization temperatures (T_ (h, )) vary fr om 3.3 to 25.9 ° C. (to liquid), and the total homogenization temperatures (T h (tot)) vary from 285 ° C. to 378 ° C. with the salinities being 4.9% -15.1% NaCl eqv and the CO 2 -phase densities being 0.50-0.86 g / cm ~ 3.H_2O-CO_2 inclusions in Q2 have T_ (m, CO_2) from -61.9 ℃ to-56.9 ℃, T_ (m, clath) ) from 3.4 ° C to 28.7 ° C (to liquid), and T h (tot) from 242 ° C to 388 ° C with the salinities being 1.0% -15.5% NaCl eqv and the CO_2 -phase densities being 0.48-0.89 g / cm ~ 3. The minimum trapping pressures of fluid inclusions in Q1 and Q2 are estimated to be 260-360 MPa and 180-370 MPa, respectively. The δ ~ (34) S values of pyrite from the volcanic sedimentary period vary from 2.3% to 2.8 ‰ (CDT), and those from the sulfide-quartz veins fall in a narrow range of-1.9 ‰ to 2.6 ‰ (CDT). The δD values of fluid inclusions in Q2 range from -121.0 ‰ to-100.8 ‰ (SMOW ), and the δ ~ (18) O_ (H2O) values calculated from δ ~ (18) O of quartz range from-0.2 ‰ to 8.3 ‰ (SMOW) are close to the magmatic and metamorphic fieldsThe fluid inclusion and stable isotope data documented in this study that that vein-type copper mineralization in the Wulasigou Pb-Zn-Cu deposit took place in an orogenic-metamorphic enviroment.