| The Dali Pb-Zn deposit is located in Dali town,Wuzhou,Guangxi,and southwest of Qinhang metalorganic belt,which is controlled by Dali-Pingxiang fault and its secondary fracture.The exposed strata are Cambrian Huangdongkou group and Xiaoneichong group,which is a typical terrigenous clastic rock.There is a Yanshan granite intrusion in west of the deposit.The main structure is NEE trending fault.Ore bodies host in NEE trending fault as veins.Ore minerals are mainly galena,pyrite and sphalerite,and gangue minerals are mainly quartz and a small amount of calcite and chlorite et al.Ore texture include medium-coarse grains,hypidiomorphic texture and anhedral texture.Structures are mainly massive,fine vein,net vein and breccia.Mineralization stages can be divided into pyrite-quartz???,pyrite-chalcopyrite-pyrrhotite-quartz???,quartz-polymetallic sulfide phase???and carbonate-quartz-pyrite???.Inclusions in sulfide quartz vein mainly are gas liquid two phase inclusion.Ore-forming fluid changes continuously from early to late.The early ore-forming fluid with characteristics of high temperature,salinity and NaCl-H2O,and homogenization temperature between 294?and 450?,salinity between 8.81%and 25.03%NaCleqv.Ore-forming fluid has obvious mutiperiodic activity,and the late fluid superimposed on the early.The metallogenic fluid is represent of low temperature,low salinity,and homogenization temperature and salinity are165?298?and 6.44%16.74%NaCleqv,respectively.Post metallogenic fluid is for low temperature and low salinity,homogenization temperature and salinity are in the order of110?158?and 2.78%8.15%NaCleqv.The hydrogen-oxygen isotope test of sulfide quartz veins in the ore-forming stage showed that the?18O?H2O?values are more concentrated and varied from 7.10to 7.91,which is the source of magma.The?D value is-54.9-61.2.In the equilibrium water?D-?18O diagram and falling into the magma water and metamorphic water superimposed area suggest that the initial ore-forming fluid for the magmatic water and late superimposed metamorphic water.Comprehensive analysis reveals,Dali-Pingxiang fault and its secondary faults have many times of activity during the past time,which make the magma fluid from deep underground upwelling along the fracture,and mix metamorphic fluid that rich in ore-forming material,at last ore-forming elements unloading along the fractures,and form the vein lead-zinc ore body.Therefore,Dali Pb-Zn deposit belongs to mesothermal hydrothermal vein deposit. |
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