Late Carboniferous to Early Permian was an important period of tectonic changes and ocean-continent transformation in northern Xinjiang area. Deposition of moderately deep lacustrine sediments of the Lucaogou Formation occurred during Middle Permian in the area. The sediments include thick dark colored shale, tuffaceous shale, and dolomite shale, intercalated with dolomitic micritic limestone, tuff, dolomite, and volcanic rocks. The dolomite is composed of interlaminated ankerite, cryptocrystalline quartz and organic matter. The distribution of dolomite is consistent with that of the underlying Upper Carboniferous volcanic rocks. Preliminary analysis indicates that dolomites were related to magmatism and mantle hydrothermal fluid, and formed as lacustrine eruptive hydrothermal dolomites.