 Late Neoarchean rocks spread over the whole Eastern Block.High to medium-grade gneiss and ultramafic extrusive rocks, especially komatiites occur in eastern Hebei, eastern Shandong, northern Liaoning and southern Jilin areas, whereas low to medium-grade granite-greenstone terranes are seen in western Shandong, southern Liaoning and Anshan areas.All rocks were formed in a geologically brief period, between 2.55 and 2.5 billion years ago.