BACKGROUNDOMS-2 has shown great significance in ion exchange, catalyst, energy and environment, but the research of natural OMS-2 mineral material cryptomelane is still lacking in the detailed characterization of the composition, structure and genetic research. Annulus and core-rim structures are representative in the structure of manganese oxide minerals. It is of great significance to clarify the mineral species and explore its composition characteristics, its origin and develop the application of manganese oxides. The Mn ore resource of Guangxi account for 23% of the manganese ore resource reserves in China. The Xialei Mn deposit located in Southwest Guangxi is the earliest super-large Mn deposit discovered in China, with an average grade of about 30% for the manganese oxide ore.
OBJECTIVESTo explore the annulus and core-rim texture and its composition of cryptomelane in the Xialei Mn deposit.
METHODSQuantitative analysis and element mapping of EPMA and microscopy were carried out.
RESULTSThe element intensity of the cryptomelane with annulus texture was Mn, K, Mg, Al, Zn, Ba, P, Fe in order of average from strong to weak. The average element intensity of the cryptomelane with core-rim texture was Mn, K, Ca, Mg, Zn, Ba, P, Fe from strong to weak. The K content gradually increased (2.31%-4.17%, 0.38-0.62 atoms per formula unit) from the middle to the rim of the cryptomelane, indicating K enrichment during oxidization and the stable status of Mn oxides.
CONCLUSIONSThe change in the trend of K and Mn ions is the direct cause of the formation of the annulus and core-rim texture, reflecting the changes of oxidation environment. Potassium content gradually increases from the inner to outer zone, which may indicate the enrichment of potassium during the oxidation process, and also reflects manganese oxide gradually tending to the most stable state.