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-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,CO_(2)))of H2O-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,CO_(2)))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.H2O-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,CO_(2))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.Theδ-(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).TheδD values of fluid inclusions in Q2 range from-121.0‰to-100.8‰(SMOW),and theδ-(18)O(H2O)values calculated fromδ-(18)O of quartz range from-0.2‰to 8.3‰(SMOW).TheδD-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-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,CO_(2)))of H2O-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,CO_(2)))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.H2O-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,CO_(2))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.Theδ-(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).TheδD values of fluid inclusions in Q2 range from-121.0‰to-100.8‰(SMOW),and theδ-(18)O(H2O)values calculated fromδ-(18)O of quartz range from-0.2‰to 8.3‰(SMOW).TheδD-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.
