Supernormal Enrichment Mechanism Of Lithium In Bauxite Series In Permian,Western Guangxi

As a genre of strategic rare metal,Li is applicated widely in the high-tech industry.The lithium ore deposits that have been found so far were divided into pegmatite type,brine type and clay type.The clay-type lithium ore,compare to the other two types,was at low level of exploration and utilization.However,the concentrations of lithium in coal or bauxite contained ore series are widespread,with a good prospect of application.Western Guangxi is one of the significant bauxites producing areas in China,with a huge number of deposits and a large scale.The enrichment of lithium in sedimentary bauxite ore series is impressive to be using as lithium resource–the content of Li₂O is 0.17%at average–which exceeds the level of comprehensive utilization(Li₂O?0.05%).The roof and floor of the Permian bauxite ore series in western Guangxi are limestone.The main section presents as conglomerate,high-Fe bauxite,bauxite ore(clastic,lentil and oolitic),bauxite with rhythmic layering and carbonaceous mudstone(or coal)from bottom to top.In order to figure out the enrichment mechanism of lithium in aluminous ore series,the sedimentary bauxite deposit in Upper Permian,western Guangxi is chosen as the research object.By finding out the occurrence state of lithium and the changes of sedimentary environment in the forming–depositing–mineralizing process,the enrichment of lithium is revealed.It can be concluded that lithium is concentrated in carbonaceous mudstone in the bauxite section,part of lithium can be found in bauxite,by the method of field investigation,X-ray Diffraction(XRD)analysis and lithium leaching experiment.Lithium is located in clay minerals with the form of isomorphism.Some Li-ions are adsorbed on the surface of clay due to the negative charge generated.There is still few of lithium exists as cookeite.The sedimentary environment of bauxite series is mainly sea-land interchange environment.The forming process experienced three stages:lagoon,tidal flat and swamp.The Li-rich clay stones were mainly deposited in tidal flat and coastal swamp.The enrichment of lithium in bauxite series was closely related to the ore-forming process with sedimentary bauxite.Geochemical data show that the provenance of bauxite series was mainly weathered from aluminum silicate,while tuff might provide the major substance for depositing and mineralizing.The weathering products of the first stage were kaolinite and soluble silicate.The further weathering product of kaolinite is diaspore,which was the basic mineral of bauxite.Under the influence of biological actions,it formed carbonaceous mudstone.The bauxite series in Upper Permian,western Guangxi were formed in the semi-closed isolated platform,which was surrounded by reefs that can stop the loss of lithium into the vast marine.After the clay deposited,Li⁺was adsorbed on the surface of clay minerals by the negative charge,then Li⁺replaced out Al³⁺with Mg²⁺,or replaced out Si⁴⁺with Al³⁺.This process made Li⁺enter the lattice of clay and formed Li-rich clay stones.A few of clay transfer into cookeite,while a small amount of adsorbed lithium is preserved due to incomplete isomorphism substitution reaction.This research identified the Li enriched layers and occurrence state in the bauxite series section and revealed the enrichment mechanism of lithium in Li-rich clay stones initially.The significance of the study can be drawn that providing a basis for the exploration and industrial application of this classification of lithium resources.