LA-ICP-MS ziron U-Pb isotopic age of alkali-rich magmatic rocks in the Midu-Weishan area,western Yunnan,and its tectonic setting

The Jixiangzhuang volcanic rock at Midu and the Dalianhuashan pluton at Weishan are the major parts of the Jinshajiang alkali-rich magmatic rock belt, with both distributed along near north-west direction and controlled by the Ailaoshan—Jinshajiang fault zone. In this article, authors investigated petrology and LA-ICP-MS zircon U-Pb geochronology of the rock samples collected from the Jixiangzhuang volcanic rock and Dalianhuashan pluton. The petrographic characteristic shows that the Jixiangzhuang volcanic rock is trachyte and the Dalianhushan pluton is quartz-diorite-porphyry. The LA-ICP-MS zircon U-Pb dating yields a ²⁰⁶Pb/²³⁸U weighted average age of 36.27 ±0.50 Ma for the Jixiangzhuang volcanic rock and an age of 37.02 ±0.46 Ma for the Dalianhushan pluton. It can be concluded that the Jixiangzhuang volcanic rock and Dalianhuashan pluton formed in a post-collision tectonic background in Early Himalayan period.