Gallium Abundance and Isotope Geochemistry in Coal and Mudstone from the Huainan-Huaibei Coalfield: Implications for...

This study conducted a systematic analysis of the abundance and isotopic geochemical characteristics of gallium (Ga) in coal and mudstone from the Huaibei region, aiming to reveal the distribution patterns, controlling factors, and geological significance of Ga in this area. Ten representative samples were selected from the Huainan-Huaibei Coalfield, and their Ga contents and isotopic compositions were accurately determined using advanced analytical techniques, including X-ray diffraction (XRD), inductively coupled plasma mass spectrometer (ICP-MS), and multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). The study revealed that the average Ga content in coal samples from the Huainan-Huaibei region was 9.4 ppm, while in mudstone samples, it was 30.2 ppm, indicating a relative enrichment of Ga in mudstone. The abundance differences stem from variations in mineral composition between coal and mudstone. Organic matter in coal predominantly limits Ga enrichment, whereas clay minerals in mudstone can adsorb and fix Ga. Significant differences were observed in the Ga isotope ratios (δ⁷¹Ga) between coal and mudstone, with coal samples averaging -1.32‰ and mudstone samples averaging -1.41‰. These differences may be related to the adsorption and bonding modes of organic matter, mineral composition, and diagenetic history. Further analysis revealed a certain correlation between the H/C ratio, an important indicator of coal metamorphism, and Ga content as well as its isotopic composition, reflecting the influence of metamorphism on the geochemical behavior of Ga. This study enhances our understanding of the geochemical behavior of Ga and provides a new tool for tracing regional geological events. Ga isotopes can reflect information on various geological processes, aiding in the understanding of sedimentary basin evolution and other aspects. This research holds significant implications for the development and utilization of Ga resources and geological studies.