Isotope Drift Characteristics in Ordovician Limestone Karst Water Caused by Coal Mining in Northern China

Samples from different areas near the Fengfeng Mine in northern China were analyzed for H-2 and O-18 isotopes. In the southern areas, the H-2 and O-18 isotopes exhibited no significant drift off the background. However, in the eastern area, the H-2 isotope drifted remarkably, although H-2 and O-18 both drifted in some samples. In the northern area, the H-2 and O-18 both obviously drifted. The H-2 drift is attributed to deuterium equilibrium due to water-rock interactions between the Ordovician limestone (OL) karst water and silicate minerals. The O-18 drift probably came from water-rock reactions between OL water and carbonate minerals, along with the O-18 equilibrium reaction. It was demonstrated that the dual drift were connected to water-rock reactions between the OL water, carbonate, and silicate minerals. Therefore, the drift was actually due to equilibrium exchange of OL water-rock interactions during the water level descent and ascent, which was closely related to the mining activities.