| Gangdese tectonic-magmatic belt is a huge tectonic-magmatic belt which located between Bangong-Nujiang and Brahmaputra ophiolite belt. It is about250km width and2500km long from east to west, and has the world-class mineralization potential in the Qinghai-Tibet plateau. At present, a huge amount of porphyry and skarn copper, two large copper (gold) mines (JaMa,Dong Ga),five small to medium-sized deposits(Qulong,LaKangE,TingGong,ChongJiang,NanMu)and a number of mine sites and mineralized point has been found. The dominant mineral of the Gangdese are copper, lead, zinc, gold and iron-rich etc, beside that, tungsten and tin are also the potential mineral. However, the research about tungsten and tin mineral in Tibet is still insufficiency, only four tungsten deposits and a certain numbers of tungsten tin points having been found. But the eastern section in the north Gangdese is the favorable geological conditions and the number of mineralization clues has been found.Geological structure of the study area is complex, which developed fractures with various sizes and nature.These fractures are intersected and parallel to each other, formed a relative complex fault structures and control the distribution of some parts of rock.The lithology of the rock in this area are mainly tonalite,granodiorite,biotite granite,monzogranite and K-feldspar granite.The tonalite,granodiorite and monzogran-ite show the balloon expansion emplacement characteristics, formed positiveemplac-ement in the surrounding rock.K-feldspar granite show dyke expansion and stopping emplacement characteristics,formed passive invasion in the surrounding rock.By studying the Petrology, petrochemistry and rare earth, trace element geochemistry features of the formation rock, tungsten-tin granite can be summarized. After doing that, the source of the ore is able to identify through the study of the trace element abundance characteristic of the formation rock.The North of Gangdese only has native snow-capped mountains of tungsten (molybdenum) deposit, two alluvial tin deposits (in BanGe) and a skarn-typecopper-tungsten deposit (in NaQu).There are also many mine sites and prospecting clues in the area. The main ore metallic minerals in these deposits are Wolfram-molybdenum, molybdenite, scheelite.The alteration of the surrounding rock is intensely, which includes silicification,greisenization, skarn,marbleization, calcilization, fluoritization, sericitization,kaolinization.By studying the mineralogical characteristics and the special structure, the existence of the magma-hydrothermal transitional stage in the process of magmatism of this region has been proven. During this stage, the element of W and Sn from the magma chamber moved into the volatile phase. So the main component of volatile phase, fluid phase, which was extruded from magma, were gathering at the top of the magma chamber shell. This process made the previously consolidation of mineral develop selfing (sodium,potassium). In the process of its evolution of the Gangdese S-type granites in the northern zone of the eastern section, the crystallization and differentiation plays a dominant role. The aquifer fluid isolated from the Crystallzati-on of magma migrated at the top of the intrusive rocks and through the channels of surrounding rock channel.With the decrease of temperature and pressure, and the presence of the channel, the fluid eventually moved into the surrounding rock and formed pegmatite dikes and vein, which made the mineral (W,Sn) processing repeatedly extraction, compensation, fractionation,and back into the fluid (including mine), and finally been mineralized.As a conclusion, the Gangdese northern zone of the eastern section has a superior geological condition for tungsten tin deposit, and possesses of a large number of tungsten-tin granite which providing main source of ore minerals, and the potential of tungsten and tin mineralization is high. |
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