Mineralogical Characteristics And Significance Of Mayuan Pb-Zn Deposit

In this thesis,the Nanmushu deposits of Mayuan in Shanxi province are taken as the study objects.By utilizing methods of mineralogy,petrology and geochemistry,a detailed analysis is about the geologic feature,the mineral typomorphism and isotope geochemistry and discussing the genesis of Namushu deposit.Nanmushu deposit is located in southern of the Qinling orogenic belt,northern of the Yangtze plate,eastern margin of the Micangshan uplift and southern of the Beiba dome.The ore-bearing strata is Sinian Dengying Formation brecciated dolomite and ore body is obviously controlled by strata,fracture zone.The mineral compositions are relatively simple.The main metallic minerals are sphalerite,galena,pyrite.The nonmetallic minerals are dolomite,quartz,barite,bitumen.The study of physical characteristics shows that sphalerites and galenas are high visual reflectances,and the microhardness values of sphalerites and galenas are low.Zinc element of sphalerite is a high level,Fe element is a level,and characteristics of other trace elements are similar to MVT deposits.The study of sphalerite's inclusion shows that homogenization temperature is higher than most of MVT deposits in China,and CH₄ is found.The study of galena's chemical composition shows that the deposit is in low-temperature hydrothermal type.Zn,Pb elements of bitumens suggest that organic matters might provide apart of ore-forming matters.And their S/Ni ratios indicate that most of bitumens transport from the Cambrian system,a part of bitumens generate in the Sinian system.The Pb isotopes of sphalerites and galenas suggest that ore-forming matters might transport from the crystalline basement,Dengying Formation or Guojiaba Formation.The S isotopes of sphalerites and galenas suggest that sulfur thermochemical reduction of sulfates from the sedimentary should be derived from the in suit strata.The C isotopes suggest that organic matter may be involved in the mineralization process.Formation age determined by Rb-Sr isochron methods for sphalerites and galenas,are 486.7±3.1Ma.The dating result is corresponding with the Nanzheng uplift.The minerogenetic mechanism is that the uplift movement drove thermal fluid,and organic matters reduced combined with metallic elements,converting to ore deposits.In conclusion,Nanmushu deposit has obvious metallogenetic characters,mineralogical features,metallogenic mechanism of MVT deposits.