锡和钨:西藏冈底斯带潜在的优势矿种

Tin and tungsten: potential dominant mineral species in the Gangdise belt,Xizang

规模巨大的西藏冈底斯复合岩浆岩带近几年已被公认是我国又一个重要成矿带,拥有铜、铅、锌、金和富铁等优势矿种。除此之外,锡钨应是两个潜在的优势矿种。该带在中、新生代板块活动频繁而强烈,生成有弧花岗岩、碰撞造山花岗岩和后造山花岗岩。碰撞造山花岗岩源于陆壳的局部熔融,具有锡钨成矿专属性。它与弧花岗岩共同集中分布在南、中、北冈底斯3个花岗岩带中,时代以白垩纪至古近纪为主,数量每个岩带均有40个以上的岩体。据岩石学、岩石化学和稀土、微量元素地球化学特征可在每个壳熔花岗岩带中区分出期波下日、桑巴、雅唐那、鲁巴杠、鱼弄、更张等一批成锡花岗岩;据地层岩石的微量元素丰度判定出念青唐古拉岩群、下古生界、中上侏罗统和下白垩统等地层为锡、钨矿源层;加上众所周知的冈底斯带多期构造变动和发育的各种塑、脆性变形形迹,说明冈底斯带确有锡、钨成矿的优越条件。而已有的锡钨矿床、矿(化)点、找矿线索和找矿信息表明,在冈底斯带中确有这两种矿存在,且有进一步普查找矿前景。

The giant Gangdise compound magnatic belt in Xizang is known as another important metallogenic zone in China, in which copper, lead, zinc, gold and iron are hosted as dominant mineral species. In addition, tin and tungsten should also be potential dominant mineral species in the Gangdise belt. The frequent and severe plate movements during the Mesozoic and Cenozoic in the belt resulted in the formation of the arc granites, collisional orogenic granites and postorogenic granites. The collisional orogenic granites were originated from the partial melting of the continental crust, and thus have the metallogenic specialization of tin and tungsten. These granites coexist with the arc granites in the southern, central and northern Gangdise granite belts including more than 40 granite masses in each of the granite belts dated at the Cretaceous and Palaeogene. On the basis of petrographic, lithochemical, geochemical signatures of REE and trace elements, the Qiboxiari, Sangba, Yatangna, Lubagang, Yunong and Gengzhang tin-forming granitic masses are recognized in the crust-melted granitic belts cited above. The source beds of tin and tungsten include Nyainqentanglha Group Complex, Lower Palaeozoic, Middle - Upper Jurassic and Lower Cretaceous strata on the basis of the trace element abundances. The tin and tungsten mineralization is well documented by the features of multistage tectonic activities and plastic and brittle deformational, traces and exploration of the existing tin and tungsten deposits （mineralized localities） in the Gangdise belt.