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 peri...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：H2O-CO2 inclusions,carbonic fluid inclusions,aqueous fluid inclusions,and daughter mineral-bearing fluid inclusions.Microthermometric studies show that solid CO2 melting temperatures（T（m,CO2）） of H2O-CO2 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 CO2-phase densities being 0.50-0.86 g/cm-3.H2O-CO2 inclusions in Q2 have T（m,CO2） 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 CO2-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.展开更多
基金funded by National Nature Science Foundation of China(41372096)
文摘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：H2O-CO2 inclusions,carbonic fluid inclusions,aqueous fluid inclusions,and daughter mineral-bearing fluid inclusions.Microthermometric studies show that solid CO2 melting temperatures（T（m,CO2）） of H2O-CO2 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 CO2-phase densities being 0.50-0.86 g/cm-3.H2O-CO2 inclusions in Q2 have T（m,CO2） 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 CO2-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.
