Studies On Material Composition And Genesis Of The Jilinbaolige Deposit In Inner Mongolia

The newly discovered Jilinbaolige deposit is a Pb-Zn-Ag polymetallic deposit in the Dong Ujimqin Banner,Inner Mongolia,located in the Dong Ujimqin Banner Pb-Zn-W-Sn-Fe-Cu metallogenic belt in the northeastern part of China.Ore bodies mainly occur as vein type and they are hosted by the Upper Devonian Angeeryinwula Fm.The Angeeryinwula Fm is mainly composed of argillaceous slate with sand and tuffaceous pyroclastic rock.Field observation and mineralogic study indicate that there are mainly four types of metal sulfides formed by hydrothermal action in the deposit:?1?the common sulfide minerals:pyrite,arsenopyrite,chalcopyrite,sphalerite and galena;?2?sulphide minerals of bismuth:bismuthinite,cosalite and wittichenite;?3?sulphide minerals of tin:stannine and isostannite;?4?other sulfide minerals:tetrahedrite,chalcostibite,bournonite,robinsonite and digenite.Silver minerals are bismuthinite and stannine.According to the observation of the ore structure in the field and the observation of the mineral symbiotic assemblage and structural features under the indoor microscope,the mineralization is roughly divided into the hydrothermal period and the epigenetic period.The hydrothermal period can be divided into three stages:?stage??pyrite-arsenopyrite-chalcopyrite-sphalerite stage,?stage??galena-sphalerite-tetrahedrite-quartz and?stage??pyrite-calcite-quartz.The study of fluid inclusion shows that liquid-rich phase inclusions is main type.Temperature of Pb-Zn-Ag met allogenic stage is 149?²40?,the average value is 190?.The salinity w(NaCl_eqv)of ore forming fluid is measured in the range of 1.22%¹8.55%,the average value is 8.09%.There are two areas of concentration,respectively 1.22%³.71%and13.62%¹8.55%.The variation range of ore-forming fluid density is 0.87g/cm³⁰.94g/cm³,the average value is 0.90g/cm³.The ore forming fluid is a medium low temperature,medium low salinity and low density fluid.The laser Raman spectrum analysis of inclusions is mainly water.The results of hydrogen and oxygen isotope analysis show that the?D of Pb-Zn-Ag met allogenic stage is-146.0‰^-133.7‰,the average value is-139.9‰.?¹⁸O_water is range of-17.0‰⁰.2‰,the average value is-13.1‰.The plots of?D-?¹⁸O_water indicates that the met allogenic hydrothermal solution is a mixed source of magmatic water and atmospheric precipitation.The early middle and high temperature iron copper zinc mineralization stage in the early mineralization is mainly magmatic water,and the middle and late middle low temperature lead,zinc and silver mineralization stage in the middle and late metallogeny are mainly atmospheric precipitation.Sulfur isotopic compositions of metallic sulfide indicate that sulfur in the deposit is provided by the combined balance of sedimentary rock and magma.Lead isotopic compositions of metallic sulfide and sedimentary rocks and magmatic rocks indicate that lead is mainly derived from magmatic rocks and sedimentary rocks in the mining area.The comprehensive analysis shows that the boiling and mixing of fluid are important mechanisms leading to the enrichment and deposition of ore-forming elements.The Jilinbaolige Pb-Zn-Ag deposit belongs to the middle-low temperature hydrothermal vein type deposit.