SIGNIFICANCE AND CHARACTERISTICS OF OPHIOLITE SUITE IN LAJI SHAN, SOUTHERN QILIAN MOUNTAINS, QINGHAI PROVINCE,CHINA

Laji Shan is located in the eastern part of Qinghai Province,sandwiched between Xining and Hualong Basins.It is about 250km long and 10～20km wide from Riyueshan in the west to Minheguanting in the east.Laji Shan belongs to the Caledonian orogenic belt.Its basement consists of the rocks of Palaeo\|Protero zoic Hualong Group (Pt 1 hl ) and Neo\|Proterozoic Huangzhong Group (Pt\-3 h ).There are ptygmatic folds,closely linear type folds,strongly structural d ifferentiation and schistosity developed,suggesting that the basement underwent deep seated ductile deformation.The main part of Laji Shan is composed of Early\|Palaeozoic marine facies volcanic rocks and clastic sedimentary rocks,and suffered greenschist facies metamorphism and brittle\|ductile deformation.Others are composed of Ea rly\|Palaeozoic basic and ultrabasic rocks,intermediate\|acidic intruded rocks a nd dike rocks.Devonian molasse formation in Laji Shan is in uncomfortable contac t with underlying strata.Jurassic and Cretaceous systems are intermont basin dep osits,corresponding to a cover.