Rb mineralization during magmatic differentiation: Insight from mineralogical study on the Ganfang rare metal granite, Jiangxi Province

The Rb mineralization is associated -with rare metal granites. However, -widespread hydrothermal alteration in the late evolution of rare metal granites makes it difficult to distinguish the magmatic process from the hydrothermal process. It is still unclear whether the rare metal mineralization is dominated by magmatic differentiation or hydrothermal metasomatism. The Ganfang intrusion in the Jiangxi Province is an important rare metal metallogenic area, where a series of Li-Rb rare metal deposits (mineralization) have been discovered, and the mineralization mechanism of rare metals is not yet clear. This paper takes both granite-type Rb (Baiguo, Dagang, and Nanmukeng) and aplite-type Rb (Fuhua, Tongan) mineralization from the Ganfang intrusion for case studies. The detailed mineralogy texture and composition of feldspars and micas have been analyzed by automatic mineral scanning system, electron probe and LA-ICP-MS. The results show that micas are the main carriers of Rb (1683X10 -12047X10 ), and the contents of Rb in feldspars are lower. The Rb content of K-feldspar is 1683X10 -4051X10 , whereas albite contains almost no Rb concentration (1. 82 X 10 -89.94X10 ). The Rb-bearing micas transfer from muscovite, though Li-phengite and zinnwaldite, to lepidolite, in which substituted mechanisms for Li are 2Li + ,vSi4+- v,Al3++v,Al3++n andLi++Fe2+- V,A13++H, and for Rb is Rb+/ Na+ /Cs+ ~ K+. The mineral textures and compositions record both magma crystallization differentiation and fluid metasomatism for Ganfang granites; however, the former -was the key enrichment mechanism for Rb as •well as Li. © 2023 Geological Society of China. All rights reserved.