喜马拉雅稀有金属成矿作用研究的新突破

喜马拉雅地区淡色花岗岩广泛分布,但相关的稀有金属成矿问题长期被学术界忽略,因为传统观点认为,这些花岗岩是高喜马拉雅变质岩系原地部分熔融而成。但自提出该地区淡色花岗岩高度结晶分异成因模式后,与这些花岗岩演化相关的稀有金属成矿问题引起各方重视,并在铍和铌钽的矿化研究方面取得显著进展。尽管如此,锂的成矿作用研究和资源寻找并没有取得大的突破。本期《岩石学报》报道的喜马拉雅中部琼嘉岗和热曲锂辉石伟晶岩及珠峰前进沟锂电气石-锂云母伟晶岩的发现,充分说明喜马拉雅地区锂资源前景广阔,表明喜马拉雅有望在近期内成为我国稀有金属资源的大型接替基地。根据目前的进展,喜马拉雅地区未来稀有金属成矿作用应加强如下方面的研究：1）加大区内淡色花岗岩岩石学与岩石成因研究力度,厘定它们岩浆结晶分异的程度与成矿潜力;2）对北喜马拉雅穹窿和岩体开展接触变质与围岩蚀变研究,以寻找热液交代型稀有金属矿床;3）加强高喜马拉雅地区藏南拆离系与花岗岩侵位关系的研究,以判断分异岩浆及成矿伟晶岩的赋存部位。近期应集中力量围绕普士拉一带的藏南拆离系、韧性变形的肉切村群地层和淡色花岗岩-伟晶岩等开展联合攻关研究,以期在锂资源上取得更大的突破。

New breakthroughs in the studies of Himalayan rare-metal mineralization

The importance of rare-metal mineralization in the Himalayas was never highly thought since it was generally agreed that the widely distributed leucogranites there were generated by in situ partial melting of the Higher Himalayan metamorphic rocks. However, since the advent of highly fractionated model for these leucogranites, the associated rare-metal mineralization had attracted much attention, with discoveries of numerous beryllium-, niobium- and tantalum-bearing deposits. Nevertheless, no significant progress was obtained for the lithium mineral resource in the area. This issue of "Acta Petrologica Sinica" reports discoveries of a super-large Qiongjiagang lithium deposit, Rachu spodumene-bearing pegmatite, and Qianjingou elbaite/lepidolite-bearing pegmatite in the central Himalaya, indicating that the lithium resource in the area is highly expected, and the Himalaya is getting the potential to become a large strategic reserved base for rare-metal mineral resources in China. According to recent studies and progresses, the future works should be focused on the followings:1) Petrology and geochemistry of the leucogranites, to make clear their fractionation degree and rare-metal mineralization potential; 2) Metamorphic aureole and its fluid metasomatism of the northern Himalayan domes, to look for the hydrothermal metasomatic deposits; 3) Relationship between the movement of the South Tibetan Detachment System (STDS) and emplacement of the leucogranites, to locate the highly fractionated granites and related mineralized pegmatites. In the near future, a joint research should be carried out to the STDS, mylonized Rouqiecun Group strata and the associated leucogranites in the Pushila area, in order to get a greater breakthrough of lithium resource.