The Early Paleozoic ophiolite melanges in Hongliugou of Altun fault belt (AFB) is composed of mantle peridotites, gabbros, diabases, basaltic dykes, pillow lavas, silicalites and flysches. Two types of basalt have been recognized in the ophiolite melanges: T_MORB and OIB, whose REE distribution patterns are flat_type and LREE_rich_type respectively. The presence of such rock assemblages indicates the existence of an ocean basin in this region in Early Paleozoic. This rock combination is comparable with its counterparts in northern Qilian Mountains.