Experimental Study On Hydrogeochemical Mechanism Of Pyrite In The Coal-Water-Bearing Fracture

Pyrite is charactermatic mineral which deposited in the organic-rich sedimentary and it is treated as an important indicator of recovery depositional environment. In the Permian coalfield of South Huanghuai plains, the phenomenon that pyrite mural crystal growth is widespread exist in the water conducting fracture of coal mine. Study on the formation of pyrite in coal-bearing fissure not only has certain analysis of metallogenic significance, also there are important theoretical and practical significance both understanding hydrogeochemical processes in coal measure strata and analyzing hydraulic conductivity fractured sediments filling closure effect.According to a routine chemical analysis for the groundwater quality of representative coal mine, we found that in the areas of pyrite crystal growth, groundwater quality was characterized by high K++Na+, HCO3- ion content and low SO42- ion content. The water samples which were taken from Huainan Coalmining area Zhangji mine containing Desulfotomaculum genus and Sulfur Bacillus genus, after they were sequenced by Shanghai Sangon. Combined with the physiological characteristics of the two strains, we cultured water samples and found the metabolites of the two bacteria were ferrous sulfide and elemental sulfur.In order to ascertain the mechanism of pyrite growth in coal water conducting fracture, pure chemical experiments and microbial experiments which simulate the actual conditions of the mine were carried out. According to microbial experiments and pure chemical experiments, it can be concluded that the nature of the mine pyrite is produced by purely chemical means, reaction required substrates such as ferrous sulfide and elemental sulfur are provided by microbial metabolism. Formation of pyrite in coal water conducting fracture has gone through three stages, there are two types of bacteria to participate. First stage:SRB bacteria reducing haxavalent sulphur of sulfate in coalfields groundwater into negative two prices of FeS and H2S by off sulfuric acid effect. Second stage:SOB bacteria oxidize negative divalent sulfur into sulphur of zero-valent. Third stage:FeS and elemental sulphur produce pyrite of negative price by pure chemical reaction.