Abstract: The Daping mylonitized riebeckite-aegirine granite is located in the southern part of the Ailaoshan-Jinshajiang Cenozoic alkaline magmatic rock belt.The zircons for dating form this granite are of two types:the metamorphic zircons and the metamorphic composite zircons which have old cores and new shells.Their crystal morphology is irregular and／or rounded.Th e high-degree concentration and layering of zircons are observed in rock thin sections.The results of dating are as following:the old core U-Th-Pb age is 247 Ma by using ELA-ICP-MS and the new shell U-Pb age is 145 Ma by using SHRIMP in metamorphic composite zircons.At the same time,there was a regional metamorphic process before mylonitization.In the weakly mylonitized segments the rocks have prism-granular blastic texture and granoblastic texture.The rocks have clear layering,which suggests a sedimentary-metamorphic genesis of this granite.