Abstract:  The dolomitic rocks are developed in the Fengcheng Formation in WuXia area, Junggar basin and are considered to be the important reservoirs for further petroleum exploration and exploitation. Based on the core observation of 13 wells as well as the core sample tests, the dolomitic rocks petrological and geochemical characteristics were systematically analyzed, and the origin of dolomitic rocks with different occurrences were discussed. In this study, five types of rock textures were distinguished according to their macroscopic occurrence, including rippled, diffuse, flocculent ,random bedded, and massive dolomitic rocks. They are characterized by high δ13CPDB values (average 4.0‰) and high paleosalinity values (average 13.0%). Their geochemical characteristics and deepwater originated sedimentary structures together with evaporation indicate a lowenergy, reduction in deepwater, dryhot climate and high salinity deposition environment. The formation of rippled dolomitic rocks is considered to be of the brine delamination in salted lakes. In contrast, the single crystals of random bedded, massive, flocculent, and diffuse dolomitic rocks have fogged center and clear margin, which may be resulted from the metasomatism after burial. This study provides a scientific basis for further oil and gas exploration in the Fengcheng Formation of WuXia area and other dolomiterich areas.

Key words: penecontemporaneous dolomite, metasomatism dolomite, volcaniclassic rocks, Fengcheng Formation, WuXia area, Junggar basin