In the northern Qilian Mountains, Middle-Late Ordovician backarc basin m arine vo lcanic rocks are distributed as a narrow belt on the north side of the Zoulang Nanshan (the sou th mountains across the Corridor)， characterized by both oceanridge besalt an d isla nd arc volcanic rocks, comprise mainly basic and partly intermediate and intermediatea cidic volcanic rocks, most of which are lavas and some pyroclastic rocks. Extensive Cyprustype copperenriched mineralization has been discovered in t he ba ckarc volcanic rocks, featuring intensive backarc basin extension. The typic al case is the Shijuligou Cuenriched Massive Sufide deposit in Gausu. It show s t hat the orebodies are controled by primary fractures constrained by t he volcanic appar atus，and that the convection circulation of hot saline （hydrothermal) solution plays an important role in the formation of the orebodies formed just after th e volcanism.