Characteristics And Ore-forming Fluids Of Saxi Tungsten Deposit In Laojunshan,Southeastern Yunnan Province

The Saxi tungsten deposit is typical deposit in the tungsten- polymetallic ore concentration area in Laojunshan SE Yunnan Province It mainly lies in the metamorphic rock of Saxi series Pt1s).Thrust- nappe structures with SE-NW direction shown is principal tectonic in the region.The ore body is divided into disseminated type and quartz-vein one. Disseminated type fairly simple in shape, is largely conistent with the strata occurrence controlled by stata and structure.Quartz-vein type, on the one side, which interludes the earlier disseminated type ore body, with mineralization enriched locally. On the other side it can form high grade ore independently. The formation of quartz-vein type tungsten deposit experienced a period composed of silicate stage, oxide-sulfide stage and calcite stage. Tungsten mineralization probably occurred at the silicate stageand oxide-sulfide stage.Systematic measurement of fluid inclusions and sulfur-oxygen-hydrogen(H-O-S)stable isotopes analysis of ore body were conducted From the silicate stage to the calcite stage both homogenization temperatures(360-230℃) and salinities show a downward trend. Ore- forming fluid in Saxi tungsten deposit is a two phase immiscibility Na Cl-H2 O system with poor CO2 content, low salinity most <10% and moderated temperature.The sulfur-oxygen-hydrogen(H-O-S) stable isotopes data hows that the major ore-forming fluid was magmatic water mixed with construction and meteoric water. Isotopic and chemical analysis of elements data suggest that mineralizing materials are mainly from intrusive granitic rock. and strata with high tungsten content. Saxi tungsten mineralization tooks place in Early Cretaceous. The thrust- nappe structure is one of the ore body control factor.content. In principle, The genetic type of Saxi tungsten deposit belongs to moderated temperature hydrothermal scheelite one.