Genesis of Rb mineralization of the Dongshang rare metal granite in Jiangxi Province

The Ganfang district in the Yifeng County, Jiangxi Province is an important rare metalmetallogenic area. A series of Li-Rb rare metal deposits (mineralization) have been discovered in the Ganfang intrusions, while the mineralization mechanism of rare metals is not clear yet. The detailed mineralogy texture and composition of feldspars and micas from the Dongshang granite have been analyzed by electron microprobe analysis. The results show that micas are the main carriers of Rb (Rb₂O <1.07%), and the contents of Rb in feldspars are lower (Rb₂O <0.11%), particularly in albite. The Rb-bearing micas are mainly phengite to zinnwaldite from muscovite granite, pegmatite, and granitic aplite. The substituted mechanism of Rb in micas is mainly coupled with Na for interlayer cation of K. The mineral textures record both magma crystallization differentiation and fluid metasomatism for the Dongshang granites, however, the former was the key mechanism of the Rb enrichment, while the later has less role on the accumulation of Rb in granites. Together with previous publications, this paper concluded that the Ganfang intrusions have a good metallogenic potential of rare metals, and the subsequent prospecting should focus on the Li, Rb, and other rare metals related to the Early Cretaceous to Late Jurassic (140~150 Ma) highly differentiated granites.