Genesis of the newly discovered rubidium deposit in Hami, Xinjiang: evidence from deposit geology and geochemistry

The newly discovered Zhangbaoshan rubidium deposit,located in Hami,Xinjiang,is a typical super-large,rare metal deposit in the East Tianshan area. Based on geological field surveys,mineralogy petrology,and geochemistry studies were conducted to study the granite mineralization and guide the prospecting of rare metals in this region to reveal the ore genesis. Research around the geochemical analysis of major and trace elements,rare earth elements (REE) shows that the petrochemical composition of rock mass was characterized by high silicon,alkali rich,Na₂O>K₂O,high F (>2%),high Rb,and ∑REE contents ranging from 21.4×10^-6 to 190.4×10^-6,with strong negative Eu anomaly. The distribution pattern of lanthanon has an "M" type REE tetrad effect. The trace elements are characterized by rich rare and scattered elements such as Li,Rb,Cs,W,Sn,Nb,Hf,Th,and Ga,which provide a material basis for rare metal mineralization. Element F,hosted in mica,has a high content in different phase bands of the magmatic evolution stage. F and rare metal elements form a series of complex compounds,which will migrate to the rock mass. Electron probe analysis indicates that element Rb presents isomorphism in the rock-forming minerals potassium feldspar and muscovite. The concentration of Rb in the veinis positively connected with the amount of potassium feldspar and muscovite. The rubidium-bearing rock body successively invaded the light granite,amazonite-bearing granite,amazonite granite,topaz-bearing amazonite granite,topaz albite granite,and amazonite-bearing granite pegmatite veins. The comprehensive analysis argues that the Zhangbaoshan rubidium deposit experienced multi-stage evolution and belongs to the magmatic crystallization and differentiation along with the metasomatismgenesis. The deposit type is a magmatic-hydrothermal deposit,whose formation era is in the late Indosinian period.