地质科技通报 (Jul 2022)
Geological, geochemical and sulfur isotopic characteristics of critical metal-enriched pyritic ore in the Puyi area, northwest Guizhou Province: Constraints on the genesis of the deposit
Abstract
The study of the isotopic and elemental geochemical characteristics and genesis of critical metal-enriched pyritic ore in the Puyi area of Northwest Guizhou provides more abundant information for the exploitation of pyritic ore resources, comprehensive utilization and evaluation of associated beneficial elements, and understanding the mechanism of critical metal-enriched pyritic ore. Based on the comprehensive collection of existing geological and mineral data, combined with field investigation, the geochemical characteristics and genesis of pyrite in this area are studied by using element geochemistry and sulfur isotope analysis, and the metallogenic model is preliminarily established. The study shows that the critical metal-enriched pyritic ore mainly occurs in the crystalline tuff at the bottom of the Longtan Formation of the middle Permian(P2l), and the ore body is simple in shape and distributed in layers. The beneficial elements, such as REEs, Li, Nb, Zr, Li, Nb, Zr, Ga, can be comprehensively utilized. The results show that ΣREE usually ranges from 180×10-6 to 1 630×10-6, with an average of 431.24×10-6 and up to 1 634.57×10-6; Ga usually ranges from 25×10-6 to 120×10-6, with an average of 32.51×10-6 and up to 120.00×10-6; Nd generally ranges from 40×10-6 to 380×10-6, with an average of 103.29×10-6 and up to 380.00×10-6; and the maximum values of Li and Al2O3 are 1 366.00×10-6 and 42.17%. The REE distribution pattern of pyritic ore is characterized by enrichment in LREEs and relative depletion in HREEs. The ore-forming elements Ga, Li, Zr, Ti, Se, Cd, Nb, V and Hg are relatively enriched, while Ba, Sr, Zn and Te are relatively depleted. The δ34S of pyrite in pyritic ore mainly range from -33.90‰ to -18.60‰(on average of -16.04‰), which shows the characteristics of the enrichment of light sulfur. The sulfur source of critical metal-enriched pyritic ore was greatly affected by the reduction of biological bacteria. Pyritic ore is mainly formed in the sedimentary stage by microbial iron reduction, microbial sulfate reduction and chemical iron reduction. It is suggested that REEs in pyritic ore mainly occur in clay minerals in the form of similar isomorphic substitution, and the formation process can be divided into the weathering transportation stage, sedimentary mineralization stage and diagenetic epigenetic stage.
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