Lithium occurrences and enrichment of granite regolith-hosted Li deposits in Jiangxi Province, South China: An example of the Xikeng Li deposit

The muscovite granite regolith in Jiangxi Province, with thickness up to 30 m, exhibits significant lithium (Li) enrichment, which holds promising potential as an economically viable alternative source of Li. However, host minerals and enrichment mechanism of Li in such regolith are poorly understood. Herein, mineralogy and geochemistry of the Xikeng granite-hosted regolith Li deposit were investigated. The studied regolith has Li2O grade up to 1.0 wt%, which showcases an approximately twofold increase in Li content compared to that found in the bedrock. Enrichment of Li in the parent granite facilitates the formation of granite regolith-hosted Li deposits. The dominant minerals observed in the studied weathering profile are derived from the parent granite through inheritance and/or transformation. The incipient stage of weathering is characterized by dissolution of K-feldspar and plagioclase and accumulation of quartz and muscovite, whereas the subsequent stage of weathering is characterized by the development of clay minerals, particularly kaolinite. The predominant reservoir for Li in the regolith is proposed to be the residual muscovite, as suggested by positive correlation between Li concentrations and muscovite content, a dominance of over 90 % in the residual phase compared to other phases from the extraction experiment, and element mapping. Adsorption of kaolinite formed through the weathering of muscovite is insufficient to effectively retain released Li, resulting in its loss with fluids. The deficiency of Li enrichment in the upper part of regolith can be attributed to this factor. The central part of regolith exhibits the most important enrichment, characterized by absence of feldspars, presence of minor clay minerals, and massive gathering of muscovite without obviously chemical weathering. This study provides confirmation that granite regolith represents a commercially viable Li resource.