Super-enrichment of lithium and niobium in the upper Permian Heshan Formation in Pingguo,Guangxi,China

The upper Permian Heshan Formation in Pingguo,Guangxi,China,is strongly enriched in lithium(Li)and niobium(Nb).The lower bauxite layer contains 0.02–0.04 wt.%Nb_(2)O_(5)(averaging 0.035 wt.%),and the overlying clay rock layer contains 0.06–1.05 wt.%Li_(2)O(averaging 0.44 wt.%),both of which exceed the cut-off grades for independent Li and Nb deposits and are therefore highly prospective.In this study,a preliminary discussion of the genesis of the Li and Nb enrichment is presented to serve as a reference for the investigation,evaluation,and prospecting for clay-and sedimentary-type Li and Nb ores in other regions.The preliminary conclusions are that:(1)The bauxite ore contains abundant anatase,which positively correlates with the whole-rock concentrations of TiO_(2) and Nb,indicating that the Nb is hosted mainly in the anatase;(2)the cookeite content in the clay rock positively correlates with the whole-rock Li concentration,indicating that cookeite is the main carrier mineral of Li,and its genesis can be attributed to reactions between clay minerals(e.g.,pyrophyllite and illite)and Li-Mg-rich underground brine or pore water and groundwater in coastal areas;and(3)provenance analysis of immobile elements(Al,Ti,Nb,Ta,Zr,Hf,and rare earth elements)suggests distinct sources for the Nb-rich bauxite and the overlying Li-rich clay rocks,with the bauxite and Nb originating largely from alkaline felsic rocks in the Emeishan Large Igneous Province,and the clay rocks being derived from peraluminous or moderately fractionated felsic rocks associated with Permian Paleo-Tethyan magmatic arcs.