The Xijir Ulan-Shexinggou and Gangqiqu ophiolitic melange belts were found in the Hoh Xil region, Qinghai Province, during the comprehensive scientific expendition in 1990. These ophiolitic melange belts and the Bayingchawuma ophiolitic melange belt are distributed along thrusts. The rocks discovered might be slices of a large ophiolitic melange belt buried deeply underneath very thick Triassic flysch which were thrust and exhumed. The melanges consist of blocks of harzburgite, gabbro, pillow basalt, massive basalt, picritic basalt, diabase, limestone, marble and chert as well as phyllite matrix. The age of the ophiolites has been determined to be Early Carboniferous-Early Permian by paleontological dating, stratigraphic unconformity and isotopic dating. The rock association in the ophiolites represents relict oceanic crust. The petro- chemical study suggests that mafic rocks, including basalts, gabbro and picritic basalt mainly formed in an ocean island environment, whereas cherts were mainly formed in abyssal or bathyal regions and partly in hydrothermally active areas near ocean islands or ocean ridge. The association of abyssal radiolarian cherts, abyssal red clay blocks and collapsed ocean island rocks as well as tectonic features show that the ophiolitic melanges belong to forearc ones and are an accretional wedge formed during subduction of the Paleotethyan oceanic crust. These data indicate that the Paleotethyan ocean had existed at least in the Early Carboniferous in the study region and that some ocean islands had existed in the ocean which largely closed at the end of the Early Permian.