|Abstract:The Lajishankou ophiolitic mélange, which formed during the evolution of Proto-Tethyan Ocean, locates between the Central and the South Qilian tectonic belts and crops out discretly along Yaocaotai, Liudaigou, Qingshashan, and Lajishankou areas. It contains varities of lithological units showing typical of block-in-matrix texture. Results on regional surveying and geological mapping show that the blocks of Yaocaotai mélange consist of lherzolite, harzburgite, serpentinite, and amphibolite, which are encased in the matrix of serpentinite and intruded by dolerite dykes. The Liudaogou ophilitic mélange can be subdivided into two belts. The southern belt is dominated by trachytic, andesitic and foliated basaltic and andesitic matrix, but the northern belt is characterized by blocks with serpentinite or basaltic and doleritic matrix. The blocks in the basaltic and doleritic matrix comprise gabbro, dolerite, pillow basalt, plagiogranite, but these in the serpentinite matrix include peridotite, pyroxenite, dolerite, and plagiogranite. Qingshashan mélange is composed of pillow basalt, limestone, volcaniclastic rocks, chert, and siliceous mudstone. Lajishankou ophiolitic mélange can be subdivided into serpentinite mélange and broken formation. The former consists of serpentinite matrix and blocks of peridotite, serpentinite, cumulate gabbro, dolerite, pillow and massive basalt, and chert, but the latter is characterized by thinner beds of mudstone, shale, chert, and limestone and blocks of conglomerate, pebbly sandstone, quartzarenite, sandy limestone, and chert. These characters demonstrate that serpentinite mélange is the major type of the Lajishan mélange.