Zircon U-Pb SHRIMP ages of eclogites from the North Qilian Mountains in NW China and their tectonic implication

Cathodoluminescence (CL) imaging and ion microprobe (SHRIMP) U-Pb dating were carried out for zircons from eclogites in the North Qilian Mountains. The results show weighted mean ages of 463 6 Ma and 468 13 Ma for two samples, respectively. These ages are the earliest record of Caledonian high-pressure metamorphism in the North Qilian Mountains, and they may represent the timing of eclogite-facies metamorphism when the oceanic crust was subducted to mantle depths in this orogenic belt.