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

Igneous intrusions can bring hydrothermal fluids, metals, and ligands to the surrounding host sequences, changing their physical, textural and chemical features to some extent depending on the degree of thermal exposure. However, regarding hydrothermally-altered coals, previous studies have predominately focused on variations in coal quality, chemistry and mineralogy, despite the growing research on stable and radioactive isotopes within coal-bearing sequences.