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Study On The Characteristics Of Metallogenic Fluids And Fluid-Geological Mapping In The Weishan-Yongping Copper-Gold-Polymetallic Mineralization District, Yunnan

Posted on:2004-06-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:1100360092496465Subject:Mineral - rock - deposits
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The Weishan-Yongping copper-gold-polymetallic mineralization district in Yunnan is tectonically located in the southern part of Lanping basin in the middle part of Changdu-Simao block between Lanchangjiang fault and Jinshajiang-Ailaoshan fault. More than 140 deposits and occurrences of gold, copper (cobalt), stibium, mercury, lead, zinc, iron etc. have been found in the area studied, and there are 4 medium-sized deposits among them.Based on the studies of microthermometry, gas composition, liquid composition, rare earth elements, ore-forming elements and 13C, D, 18O of fluid inclusions from the mineralization district and the representative deposits, such as Zacun gold deposit, Shuixie copper-cobalt deposit, Shiyancun stibium deposit and Bijiashan stibium deposit, two metallogenic fluid systems have been distinguished,i. e. , Zijinshan metallogenic fluid system and Gonglang Metallogenic fluid system in Weishan-Yongping mineralization district. The two fluid systems respectively correspond to Zijinshan-Bijiashan middle-low temperature metallogenic belt of gold, stibium, mercury, arsenic and Shuixie-Xinmin middle-high temperature metallogenic belt of copper and cobalt.The main types of fluid inclusions for Zijinshan metallogenic fluid system are liquid-rich inclusions (I a),H2O-rich inclusions(II a) and subordinate vapor-rich inclusions ( I c). Their temperatures of total homogenization are in a range from 130 癈 to 280C. Their salinities are in a range from 0. 1 wt%NaCl to 18 wt%NaCl. The gas phase is mainly composed of H2O and CO2. The main anions in the liquid composition are Cl-, F-and SO42-, and the cations are Na+, K+ and Ca2+. It belongs to NaCl-H2O-CO2 system. The ore-forming element assemblage is As-Sb-Cu-Ni-U with high contents of As and Sb. The stable isotope data show the metallogenic fluid comes from the mixture of magmatic water with meteoric water and stratum water. The pressure of mineralization is in a range from 30 MPa to 130 MPa, the corresponding temperatures of mineralization are about 228-255 C, and the depths of mineralizatoin are about 1.05-6.67 km.The main types of fluid inclusions for Gonglang metallogenic fluid system are liquid-rich inclusions (I a),H2O-rich inclusions(II a), CO2-rich inclusions and daughter-mineral-bearing multiphase inclusions(III). The temperatures of total homogenization ranged from 190 C to 340 C, and from 370 C to 410 C. The salinities ranged from 22 wt%NaCl to 26 wt%NaCl, and from 30 wt%NaCl to 35 wt%NaCl. The main composition of gas are H2O and CO2. The main anions in the liquid composition are Cl- and S042-, and the cationsare Ca2+, Na+ and K+. It belongs to NaCl-H2O-CO2 system. The ore-forming element assem-blage is Cu-Co-As-Ni-Ag with high content of Cu, Co and As. The stable isotope data show the metallogenic fluid comes mainly from the magmatic water mixed with some meteoric water and stratum water. The pressure of mineralization is in a range from 100 MPa to 225 MPa, the corresponding temperatures of mineralization are about 317-346C, and the depths of mineralization are about 3.51-7.89 km.The Zijinshan fluid system and the Gonglang fluid system were driven by the stress of extrusion nappe onto the basin and the thermal driving force of magmatism. When the fluids cycling in the basin encountered the boundary of reduction-oxidation or underwent fluid mixing, phase separating and fluid boiling caused by fault-induced pressure reducing, the physical chemistry condition abruptly changed and mineralization then took place.The fluid-geological map was made by combination of the characteristics of metallogenic fluids and the metallogenic conditions in terms of structural, stratigraphic and magmatic constraints. It shows the nature and state of metallogenic fluids and the basic characteristics of the two metallogenic fluid systems. The range of drainage area and seven concentration centers (Zijinshan, Zacun, Shiyancun, Bijiashan, Shuixie, Xinmin and Yongcui)of the two metallogenic fluid systems are delineated. The distribution of concentra...
Keywords/Search Tags:metallogenic fluid, fluid inclusion, gold deposit, cobalt deposit, copper deposit, stibium deposit, Geological Mapping, Lanpin Basin, Weishan county, Yongping county, Yunnan province
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