Study On The Geological Characteristics And Metallogenic Regularity Of Pegmatite Type Rare Metals In Northeast Guangxi

Northeast Guangxi is the most densely developed area of pegmatite dikes in Guangxi,which has a good prospecting potential for pegmatite type rare metal deposits.However,in addition to the limited rare metals investigation and mineral exploration work of the pegmatite dikes in some parts of the area,the predecessors have not yet grasped the overall understanding of the geological characteristics of the development of the pegmatite dikes and the rules of rare metals mineralization in the whole area.For service pegmatite type rare metal ore prospecting work in the area,based on the system of data collection and field geological investigation,the integrated use of rock ore appraisal and testing means such as rare metal elements,mineralogical analysis,them had collected form Maoershan-Yuechengling mountains to giant crystal compound rock mass dike rock types,distribution,and rare metal mineralization characteristic has carried on the detailed study,The next prospecting direction is predicted,and the understandings are as follows:(1)Field investigation shows that there are more than 2000 pegmatite dikes in the Maoershan-Yuechengling complex rock mass in northeast Guangxi,and the Xinzi fault and Jiebo fault are concentrated in the west of Yuechengling rock mass.In terms of spatial distribution,it is closely related to the ductile shear zone.The NNE strike is in the shape of dike or dike and intersperse into the Caledonian granite or the Proterozoic strata.From north to south,six main concentrated development zones are formed,namely Maoantang,Guali,Xianshuidong,Tongzuo,Qinjiatang and Tonghe.(2)The analysis of the geological occurrence law of pegmatite dikes shows that the pegmatite dikes in the study area have short extension(50?200m),narrow width(< 1m),relatively uniform lithology,and not common internal lithofacies zonation.The simple "two-phase" or "three-phase" structure and mineral zoning phenomenon can be found only in the local swelling part of pegmatite dikes.Among them,the "two-phase" zoning is the vein quartz core zone and the coarse-grained microplagioclase/albite lateral zone;The "three-phase" zoning is characterized by the core zone of quartz,the middle zone of coarse-grained mica feldspar,and the outer zone of potassic feldspar/albite.(3)According to the rock-forming mineral assemblage,the pegmatite in the northeast of Guangxi can be divided into six main rock types,including biotite-potassium feldspar type,two mica-potassium feldspar type,Muscovite-potassium feldspar type,Muscovite-potassium feldspar-albite type,Muscovite-albite type,potassium feldspar type.Among them,Muscovite-potassium feldspar type is the most common,widely distributed in Xianshuitong,Tongzuo,Guali and other areas,while Muscovite-potassium/albite type is mainly distributed in Mao 'antang,and potassium feldspar type is mainly distributed in Tonghe and Lengyuan.In the muscovite-potassium/albite type pegmatite,accessory minerals are most abundant,and tourmaline and garnet are common.(4)The analysis of rare metal elements shows that the ore-forming elements in the pegmatite are mainly Ta,Nb,Be and Rb,while the contents of Li and Cs are generally low.The rich Ta-Nb pegmatites are mainly concentrated in Maoantang and Guali,while Be mineralization occurs locally in the pegmatites in Maoantang area.Most of the pegmatites associated with Ta-Nb-Be mineralization belong to muscovite-potassium/albite type.Rb-rich pegmatite is widely distributed in the northeast of Guangxi,and the content of Rb in most pegmatite dikes in the area is close to or above the boundary grade,especially the content of Rb in muscopic-potassium feldspar pegmatite or potassic feldspar pegmatite often reaches industrial grade.(5)Correlation analysis of rare metal mineral elements in the pegmatite dikes shows that there is a good positive correlation between Nb and Ta,and the two often increase or decrease synchronously,especially in the pegmatite dikes in Maoantang and Meixi.At the same time,there is a positive correlation between the contents of Nb+Ta and Rb in many pegmatite dikes,often forming co-mineralization phenomenon,but the correlation between Nb,Ta and Li,Cs is low.(6)Metallogenic prediction analysis shows that the Muscovite-albinite type and Muscovite-potassium feldspar type pegmatite dikes can Be used as the favorable lithologic markers to search for pegmatite type Nb-Ta-Be deposit and Rb deposit in the area,respectively.Pegmatite has high content of albite,tourmaline,cassiterite and other minerals and strong metasomatism,which is a good mineralogical indicator for the mineralization of rare metals.In addition,according to the geochemical anomaly of rare metal elements and the content of rare metal elements in the pegmatite dikes in the area,four areas,such as Guali,Maoantang,Xianshuidong-Tongzuo and Qinjiatang-Lengyuan,are delineated as the favorable prospecting target areas for the next exploration work.