摘要
The terrestrial lacustrine dolomite with dolomite content ranging from 15%~80% and 24% in average was found in Fengcheng area in northwestern margin of Junggar basin,which belongs to dolomitic rock or dolomite-contained rock,being greatly different from the typical dolomite in rock composition and genetic mechanism. Based on the rock mineral,paleontological and geochemical characteristics of the dolomitic rocks,it is suggested that the dolomite of the Fengcheng formation was formed in the sedimentary environment with high salinity,high Mg/Ca ratio and strong reduction. The laminated dolomite was formed in the penecontemporaneous period; while the dolomites in Xiazijie formatin and Wuerhe formation were formed by the fact that their magnesium ions were originated from the deep hydrotherm and the metasomatism caused with calcium ion in the early carbonate cements.