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柴达木北缘奥陶系海相火山岩（洋脊及洋岛火山岩组合）是柴北缘奥陶纪古洋盆存在的重要证据。奥陶纪末期，柴北缘洋盆逐渐闭合，洋壳自南向北下插到祁连陆块之下。大洋消失后，俯冲作用携带柴达木陆块继续下插，祁连陆块则自北向南道冲到柴达木陆块之上，柴北缘成为陆－陆碰撞型造山带。从而在柴达木北缘地区，自北而南形成了祁连超叠壳楔、柴北缘碰撞混杂岩带以及柴达木俯冲壳楔的三单元结构模式。
The Ordovician marine volcanic rocks (oceanic ridges and oceanic volcanic assemblages) on the northern margin of Qaidam are important evidences for the existence of Ordovician paleo-oceanic basins on the northern margin of Qaidam Basin. At the end of Ordovician, the oceanic basins in the north margin of Qaidam gradually closed, and the oceanic crust was inserted below the Qilian landmass from south to north. After the disappearance of the ocean, the subduction led to the Qaidam block to continue the plug-in. The Qilian block rushed to the Qaidam block from north to south, and the northern margin of the Qaidam became the land-continental collision type orogenic belt. Thus, in the northern margin of Qaidam, the three-unit structure model of the Qilian overlying wedges, the Qaidam collision melange belt and the Qaidam subduction shell wedge has been formed from north to south.