Abstract:Qiashikansayi Hollow early Paleozoic ophiolite section is from south to north, and located at the segment of Hongliuguo-Lapeiquan ophiolite belt in the North Altyn Tagh Mountains. The section to south of Hongliuquan includes two basalt rock slices: the north basalt rock slice and the south basalt rock slice. LA-ICP-MS Zircon U-Pb dating indicates that the formation age of basalts of the north slice was Middle-Late Ordovician, which was similar to the age (Late Ordovician) basalt of the south slice, shows that basalts formed in Middle-Late Ordovician. Ages of metamorphic ages of zircons suggest that basalt undergo metamorphism with collision and post-collision of the North Altyn Ocean . Based on geochemistry data, parent magma of basalts went through clinopyroxene fractionation, and suffered from slight hybridization of crust materials. Both of basalt rock slices derived from spinal-bearing mantle, the source of basalts from the north rock slice was plausible spinal lherzolite mantle, and that from the south one was plausible-depleted lherzolite mantle; moreover, the former were formed by higher partial meting. All basalts were tholeiite of E-MORB type and formed in convergent background. Together with regional geological published report, we suggest that closure progress of the North Altyn Ocean can be divided into 4 stages, ∈2-O1: early stage of subduction; O1-O3: late stage of subduction; O3-S2: tectonic environment transfer from subduction to collision; S3-D1: post-collisional orogenic period.