Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8910375 | Chemical Geology | 2018 | 65 Pages |
Abstract
The Wulantuga No. 6 coal seam is extremely enriched in Hg, varying from 0.37 μg/g in middle coal benches to 40-90 μg/g in the upper most and lowest coal benches. Approximately 2.5â° variation in mass dependent fractionation (MDF, â 3.07â° to â 0.58â° in δ202Hg) is observed. δ202Hg vs. 1/[Hg] diagram suggests a mixture of three Hg end-members: original hydrothermal fluids, fractionated hydrothermal fluids and native coal-forming materials. In addition, Wulantuga coals all show positive mass independent fractionation (MIF) of odd isotopes, up to 0.87â° in Î199Hg and 0.66â° in Î201Hg. The Î199Hg/Î201Hg ratios range from 1.3 to 3.3, suggesting that a large fraction of photodegraded methylmercury was likely incorporated into the coal deposit. The magmatic-intruded Wolonghu No. 8 coal seam is only slightly to intermediately enriched in Hg, varying from 0.10 μg/g to 0.40 μg/g. The coals near the contact sill (â¤Â 5 cm, â 1.81â° to â 1.52â°) have similar δ202Hg as the magmatic sill rocks (â 2.05â° to â 1.80â°), both with insignificant MIF values. Coals far from the contact sill (â¥Â 15 cm) have δ202Hg values varying from â 3.40â° to â 1.61â° and Î199Hg varying from 0.26â° to 0.58â°, which are significantly enriched in light and odd Hg isotopes compared to coals near the contact sill. Î199Hg and Î201Hg in Wolonghu coals far from the contact sill resemble those of meteoritic waters and seawater in both magnitude and Î199Hg/Î201Hg ratio. Our two case studies show significant MDF and MIF of Hg isotopes, which inform on Hg migration and sequestration in the magmatic rocks and coal deposits, and on the roles of meteoric water and hydrothermal fluid circulation.
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Liugen Zheng, Ruoyu Sun, Holger Hintelmann, Jianming Zhu, Ruwei Wang, Jeroen E. Sonke,