Nanogeochemistry of karst-type bauxite from Jingxi, Guangxi, China: Revealing a new occurrence of Al, Si, Ti, Fe, and C by nanoparticles in karst-type bauxite deposit

Karst-type bauxite deposits are an essential source of bauxite. Due to their massive reserves, they have aroused the world's attention. However, there is still controversy about migrating critical elements (such as Si and Al) in bauxite. Various significant nano-mineral particles are discovered in the Jingxi bauxite deposit using transmission electron microscopy (TEM), revealing karst-type bauxite deposits' intricate metallogenic process. These nano-mineral particles provide insight into the occurrence state of ore-forming materials and the element's migration mechanisms using the microscopic nano-geosciences approach. The Jingxi deposit's bauxite samples were discovered to contain many nanoparticles of various shapes and sizes (30-50 nm and over 500 nm), including columnar, granular, and layered forms. These nanoparticles were identified through morphological, chemical, and lattice spacing analyses as scaly diaspore aggregates, columnar rutile particles, layered assemblages of graphite, and kidney-shaped goethite particles. The aluminium silicate mineral (Al, Si, and O) nanoparticles showed in-depth information about the origin of bauxite deposits' raw materials and endowed a nanometer basis for studying the difficult-to-migrate elements: Al and Si. These nanoparticles confirm an alkaline and reductive metallogenic environment and present nanogeoscience confirmation that igneous rocks are one source of ore-forming components for bauxite.