Study On The Cause Of Skarnization And Fluid Tracing In Dulong Manjiazhai Ore Section

In Yunnan province,Dulong Sn-Zn polymetallic deposit is the thir-d largest cassiterite-sulphide deposit of C hina.The Dulong deposit ismade up of several section,including Tongjie,Manjiazhai,Nandangcha-ng,Jinshipo,Lazizhai.Manjiazhai section is the superlarge one of them.In Manjiazhai section,stratiform skarnof Tianpeng Group developwidely and it's the major ore-host rock.We have gained new systematic knowledge from geological exploration,electronic probe and fluid inclusion study:1.Calcareous skarn took the leading type of the skarn in Manjiazhai.The mineral assemblages include calcium-garnet series(Andradite-Grossularite),Ca-Mg-Fe monoclinic pyroxene(Diopterite-Hedenbergite),Mafic-Calcareous hornblende se ries(Grunerite-Actinolite-Ferroactinolite),C hlorite,epidote series(epidote-pumpellyite),Mica series(Muscovite-Sericite).2.Its metallogenetic enviroment changes from slightly acidic-weak oxidation en viroment in the early stage to reducing environment in the later.3.Ore-forming fluid evoluted from high temperature and high salinity fluid to mid-dle and low temperature and low salinity fluid and had unmixing and ebu llitioncharacteristic.4.It is speculated that the skarn of Manjiazhai section is result of interactio n between magmatic hydrothermal fluids and wall rocks.