Hydrothermally-altered coal from the Daqingshan Coalfield, Inner Mongolia, northern China: Evidence from stable isotopes of C within organic matter and C-O-Sr in associated carbonates

• DOI: 10.1016/j.coal.2023.104330
• Publication Date: 2023-08-09T02:07:50Z
• Authors: Qian Wang; Shifeng Dai; David French; Baruch Spiro; Ian Graham; Jingjing Liu

Igneous intrusions can bring hydrothermal fluids, metals, and ligands to the surrounding host sequences, changing their physical, textural chemical features some extent depending on degree of thermal exposure. However, regarding hydrothermally-altered coals, previous studies have predominately focused variations in coal quality, chemistry mineralogy, despite growing research stable radioactive isotopes within coal-bearing sequences. The Pennsylvanian from Daqingshan Coalfield, Inner Mongolia, China, was thermally affected by a granitic intrusion eastern part coalfield during Yanshanian Orogeny, between Late Jurassic Early Cretaceous. investigated Hailiushu, Datanhao, Adaohai mines present study are distributed Coalfield west east. Mine is located southwest point, at distance approximately 50 km. Hailiushu about10 km apart, Datanhao them. With decreasing intrusion, there an increase vitrinite reflectance values (from 0.84% through 1.17% 1.58%) decrease volatile matter content 44.57% 31.31% 19.60%) studied three mines. revealed that westernmost coals most negative δ13Corg −24.8 ‰ −23.5 ‰; −24.3 average). In contrast, with decreases, mine range (−24.2 easternmost −23.8 −22.8 ‰, (−23.3 average), about 1 less than those coals. It not just maceral composition causes difference organic carbon isotopes, but loss 12C-enriched volatiles due effects associated igneous intrusion. This hypothesis further supported Rock-Eval analysis matter: average Tmax increases generation hydrocarbons pyrolysable as approaching Moreover, fracture/cleat-filling carbonates more abundant δ13CPDB −14.2 1.7 ‰) δ18OPDB −16.9 −7.0 these vein all indicate origin. Hydrothermal fluids derived also responsible for elevated 87Sr/86Sr ratios (0.711392–0.717643) carbonate mineral altered