The scientific literature publishes data on measurements of anomalously high oxygen concentrations near the seabed in the world's oceans. There is evidence of oxygen anomalies in the waters of the Black Sea containing hydrogen sulfide. Oxygen was detected by two methods at the same time (Winkler method and gas chromatography method). The places of detection of abnormally high concentrations of oxygen in water are confined to tectonic faults. How can minerals in the earth's crust be a source of oxygen?