EARLY PROTEROZOIC CRUSTAL EVOLUTION OF THE EAST LIAONING PENINSULA
辽东半岛早元古宙地壳的演化

The evolution of the Early Proterozoic strata in the East Liaoning Peninsula is divided into early, middle and late stages. During the early stage, the strata were split on the sliding plane in the sial, leaving behind a rift geosyncline that was much wider than the existing Early Proterozoic sequence and characterized by contemporaneous heteropic facies. In the middle-stage evolution, the stratified accumulations were made up of Dashiqiao and Gaixian formations. The former consists of dominant thick-bedded carbonate rocks of four km thick, while the latter is composed of clayey and sandy rocks of five km thick. The late-stage evolution was limited within some locations in the southern part of the Peninsula, where quartz sandstone, quartz-ite and feldspathic quartz sandstone predominate with a thickness of more than 10 km. According to the isotopic age determination, the lower limit of the Early Proterozoic geosyncline ranges from 2,300 to 2,500 Ma., and the upper limit is probably around l,700Ma. At about 2,000 Ma. before present occurred a mediumscale geological event. The crustal evolution in the area is featured by the Archaean complex as bed rocks, and the Early Proterozoic geosyncline of tensile nature in the early stage, being intensely compressed during the middle stage and uplifted in the northern part in the late stage, with the emplacement of granite-gabbro series and local piedmont deposits formed in the southern part. The geosynclines of different patterns control individual ore deposits and ore associations.