Zircons U-Pb ages of the Guanzizhen intermediate-basic igneous complex in Tianshui area, West Qinling, and their geological significance.
The Liushuigou meta-intermediate-basic igneous complex defined recently in the Guanzizhen area, Tianshui City, West Qinling, is mainly composed of metagabbro-metagabbro diorite-metadiorite. Its geochemical characteristics indicate that the complex formed in an island-arc environment. The TIMS single-zircon U-Pb age for the meta-intermediate-basic igneous complex is 507.5±3.0 Ma, which indicates that the formation age of island-arc-type magmatic rocks in the north zone of the West Qinling are Late Cambrian, and that the timing of subduction of the paleo-ocean basin represented by the Guanzizhen ophiolite and formation of the volcanic-magmatic island arc is Late Cambrian to Early Ordovician.