Distribution And Enrichment Mechanism Of Gallium In Carboniferous Permian Coals In Ningwu Basin

Gallium(Ga)is a key resource in the fields of microbiology,pharmacology,medical devices and new materials,and has been in great demand in recent years.Ga is very dispersed in the Earth’s crust and cannot be independently formed.It is mainly associated with bauxite,lead-zinc ore and coal type metal ore.The study on the distribution,occurrence and enrichment mechanism of Ga in coal is an important basis for the comprehensive development and utilization of Ga in coals and coal by-products.In this thesis,the coal quality,element content and mineralogical characteristics of the coal in the study area are studied by means of statistics and coal geochemical experiments,especially the content,enrichment and distribution of Ga in the coal.Combined with the geological and geochemical information of Ningwu Basin,the material sources of Ga in coal and the main controlling factors of Ga enrichment in coal are discussed,and the enrichment mechanism of Ga in coal in the study area is revealed The main conclusions of this study are as follows:(1)Content characteristics and distribution of Ga in coal: Ga in coals of Ningwu Basin is at a slightly enriched level on the whole.Regionally,Ga contents in coals are higher in the west part of the central north and lower in the south and east part.The distribution of stratum profile from top to bottom is first decreasing and then increasing.Ga contents is higher in upper No.2 coal seam(30.93 μg/g)and bottom No.11 coal seam(37.73 μg/g),and lower in middle No.4 coal seam(27.60 μg/g),No.5 coal seam(21.33μg/g)and No.9 coal seam(22.66 μg/g).The longitudinal distribution of Ga in different coal seams is mainly enriched in the roof and floor of coal seams and gangue.(2)Occurrence state of Ga in coal: Through Ga content in coal and coal quality,major elements and trace elements in coal of correlation analysis,combined with sequential chemical extraction experimental results,it is concluded that Ga in the coal,the main occurrence in clay minerals in the form of inorganic material(mainly for kaolinite)and iron ore or sulfide minerals.There are a few state of Ga in the coal may be associated with organic matter in coal,and the content of Ga in coal under other conditions is very little.(3)Enrichment mechanism of Ga in coal: Based on provenance and sedimentary environment analysis,it can be seen that weathering products of sedimentary rocks and granite series in Yinshan Paleocontinent and Lvliang Peninsula provided provenance basis for Ga in coal of Ningwu Basin,and the sedimentary environment in peat accumulation period promotes Ga further enriched in coal.Humid paleoclimate,weak reduction-reducing sedimentary water and high salinity sedimentary media are favorable conditions for Ga enrichment in C-P coals in Ningwu Basin.The tectonic evolution of Ningwu Basin led to the change of sedimentary environment,and the Marine and continental overfacies depositional system promoted the further enrichment of gallium in coal.