Background As a crucial coal production base in Northwest China, Xinjiang holds 40% of the nation’s predicted coal reserves, primarily distributed in coal-bearing basins such as Junggar, Yili, Tuha, and Santanghu.
Method This paper initiates its analysis by focusing on strategic metals (including Lithium, Rare Earth Element, Zirconium, Hafnium, Niobium, and Tantalum), toxic metals (Arsenic, Mercury, and Sodium), radioactive metals (Uranium and Thorium), and other heavy metals (Iron and Manganese). The objective is to comprehensively explore the enrichment mechanisms and metallogenic potential of metal elements in coal within each coalfield of the typical coal-accumulating basins in Xinjiang.
Progress Research findings demonstrate that (1) the enrichment of metal elements in coal from Xinjiang is jointly regulated by multiple factors. Specifically, the abnormal enrichment of rare metals in the Lower Permian coal is intricately linked to volcanic activities and magmatic hydrothermal processes associated with the closure of the Paleo-Tethys Ocean. Regarding the Jurassic coal in the Junggar Basin, lithium is predominantly hosted in aluminosilicate minerals (such as kaolinite and illite). Moreover, the presence of sodium can be attributed to the long-term influence of deep, highly mineralized groundwater. In the Jurassic coal of the Yili Basin, the enrichment of uranium is governed by the variation in the subsequent redox environment. Additionally, the concurrent enrichment of arsenic, mercury, and thallium might be associated with sulfide minerals. In the Santanghu Basin, the abnormal enrichment of lithium is correlated with hydrothermal fluid activities. (2) the degree and mechanism of enrichment of the same metal element in different coal fields/basins also vary significantly. The lithium element enrichment in the Santanghu Basin(up to 923 μg/g) is significantly different from the Junggar (0.2~19 μg/g), Yili (2.56~27.2 μg/g) and Hami (29.6 μg/g) basins, which have similar lithium content in their coal; the arsenic and uranium elements in the Yili Basin (up to 234 μg/g and 7270 μg/g, respectively) are higher than those in the Junggar Basin (<5 μg/g and 82 μg/g, respectively).
Prospect Overall, the enrichment of metal elements in Xinjiang coal, especially strategic metal elements, has certain potential for mineralization. However, commercial development still faces multiple challenges: the spatial and temporal distribution of multi-metal combinations in the Permian-Jurassic coal is unclear, and the exploration level is low, etc. To address the aforementioned issues, it is necessary to integrate disciplines such as geophysics, geochemistry, and AI transparent geology to clearly determine the enrichment degree and mechanism of metal elements in the sedimentary coal seams of important coal-forming basins in Xinjiang region. This will promote the collaborative development of strategic metal elements in coal and form the "Xinjiang model" for comprehensive utilization of coal resources.
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