THE LATE CAMBRIAN MAGMATIC TECTONIC THERMAL EVENTS IN LUXI AREA, WESTERN YUNNAN: A New Understanding

A large number of Early Paleozoic intrusive rocks represented by Pinghe pluton are developed on the western margin of Baoshan block-an important part of Gondwana. However, due to the lack of field survey data, its geological significance has long been disputed. Based on the 1:50 000 regional geological survey, the detailed field contact relationship has confirmed the existence of two stages of intrusive rocks in Pinghe pluton, and sedimentation, chronology and petrogeochemistry have endowed it with new geological implication. The early intrusive rocks in Luxi area are mainly monzogranites, with the LA-ICP-MS zircon U-Pb age of 488.3±3.9 Ma. The major and trace element analysis results show that the rock belongs to high-temperature biotite-rich cordierite-bearing peraluminous granite of high-K calc-alkali series, with REE characteristics of medium negative Eu anomaly, classified as the Nanling type of granite. Combined with sedimentation and regional geological tectonic background, it is considered that the intrusive rock is the product of upper crust partial melting after the collision of Baoshan block and Tengchong block in the Late Cambrian.