关键词: 稀有金属成矿；花岗岩与伟晶岩, 源区；岩浆分异

Abstract: Rare-metals are refered to elements with crustal abundances less than 100×10-6, or those that are difficult to be extracted and refineed in industry. Presently, rare-metal elements include lithium (Li), beryllium (Be), rubidium (Rb), cesium (Cs), niobium (Nb), tantalum (Ta), zirconium (Zr) and hafnium (Hf), and sometimes tungsten (W), tin (Sn), and rare earth elements (REEs). Rare-metal elements are mostly incompatible in geochemistry, and hence are concentrated in granites or pegmatites. The ongoing global transformation of green economy has created enormous demand for rare metals, which makes the granites and pegmatites critical subjects for current geological studies. In perspective of petrology, rare-metal granites and rare-metal pegmatites are kinds of rock that the rare-metal minerals exist as major or minor components, and then can be used for rock naming and classification, such as tourmaline granite, columbite granite, lepidolite granite, spodumene pegmatite, and pollucite pegmatite. It is generally accepted that the rare-metal granites come from the highly fractionation of granitic magmas, but it is much debated regarding formation of the rare-metal pegmatites. It is concluded in this paper that rare-metal pegmatites are similarly products of highly fractionation of granitic magmas, and there is currently no evidence for an independent origination of rare-metal pegmatitic magma derived from partial melting of rare-metal enriched source rocks. The different occurrences of rare-metal granites or rare-metal pegmatites are depend on their volatile components. The fluorine-rich granitic magmas tend to form rare-metal granites, and boronbearing granitic magmas mostly evolve into pegmatites, respectively, after a high degree of fractional crystallization. Therefore, whatever rare-metal granites or rare-metal pegmatites, they are products of granitic magmas after a highly degree of differentiation. Currently, the rare-metal granite and pegmatites can be divided into peraluminous and peralkaline type, but they cannot be simply classified into I- or A-type granites, since the highly fractionation makes it difficult to determine their petrogenetic types. Considering that the Nanling Mountain in southern China is the largest distribution area of rare-metal granites in the world, and China holds a significant portion of rare-metal pegmatites in the world, the future research for the Chinese scientists should focus on the dissolution capacity of rare-metals in granitic magmas under different kinds of volatile, such as fluorine, boron, lithium, phosphorus. Meanwhile, the mechanisms and conditions for a high degree of magmatic differentiation of granitic magmas should be carefully exminated. Realizing these works, a new breakthrough for the study of rare-metal granites and pegmatites in China is expected.

Key words: rare-metal metallogeny, granite-pegmatite, source rock, magmatic differentiation