Host minerals of Li–Ga–V–rare earth elements in Carboniferous karstic bauxites in southwest China

Abstract

The Carboniferous karstic bauxite-bearing rock series in central Guizhou Province in southwest (SW) China is rich in trace elements, particularly Li, Ga, V, and rare earth elements (REEs), which have potential for comprehensive utilization as independent deposits or associated resources. However, the host minerals of Li, Ga, V, and REEs are not well-constrained because the sedimentary rocks are characteristics by complex mineral composition and fine mineral particles. This situation considerably hinders the compressive utilization of these trace elements in bauxite. Herein, laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was successfully applied to element geochemistry analysis of hydrous minerals (diaspore/boehmite, kaolinite, and illite) in karstic bauxite samples, based on the principle that laser ablation data of all oxides were normalized to the sum of 100% minus the total volatile components of the mineral chemical formula. The analysis showed signal stabilization. Results indicated that the bivariate plots of selected elements had characteristics similar to statistical results of whole-rock samples from global bauxites, thereby indicating that the LA–ICP–MS analysis data were reliably but artificially herein. Combined with whole-rock geochemistry studies, the analysis results revealed that smectite may be the main host minerals of Li. Furthermore, Ga was enriched in diaspore/boehmite; V was mainly enriched in iron-bearing minerals, particularly chlorite; and REE-independent minerals, such as monazite, were the main host minerals of REEs in the Carboniferous karstic bauxite in SW China. This study contributed to the knowledge on the use of in-situ method for the element geochemistry investigation of hydrous minerals and sedimentary rocks.