哀牢山构造带南段马玉花岗闪长岩地球化学特征及其锆石U-Pb年龄

Petrogeochemistry and zircon U-Pb age of the Mayu granodiorite in the southern section of Ailaoshan tectonic belt

摘要: 对云南墨江县马玉花岗闪长岩进行了锆石U-Pb年龄和岩石地球化学分析。LA-ICP-MS锆石U-Pb测年显示，马玉花岗闪长岩年龄为263.6±2.4Ma，形成于晚二叠世。岩石地球化学显示，马玉花岗闪长岩SiO₂含量为59.56%~70.50%，全碱(Na₂O+K₂O)含量为5.16%~7.92%，且Na₂O>K₂O；岩石富集轻稀土元素，负Eu异常明显(δEu=0.84~1.32)，相对富集Sc、Hf，相对贫化Sr、Zr、Th、U。构造环境判别图解显示，马玉花岗闪长岩形成于碰撞期后板内构造环境，说明哀牢山构造带的古特提斯支洋或弧后盆地在晚二叠世(263.6±2.4Ma)已经闭合。

Abstract: This study presents bulk petrogeochemistry and zircon U-Pb dating results for the Mayu granodiorite in Mojiang, Yunnan. LA-ICP-MS zircon U-Pb dating results show that the Mayu granodiorite was formed in the Late Permian period (263.6±2.4Ma). The Mayu granodiorite is characterized by SiO₂ content of 59.56%~70.50%, alkali (Na₂O+K₂O)5.16%~7.92%, and Na₂O higher than K₂O. It is enriched in LREE and Sc, Hf, and depleted in Sr, Zr, Th, U, with negative Eu anomalies (δEu:0.84~1.32). According to the diagrams, the Mayu granodiorite was formed in a tectonic environment of island arc-continent or continental-arc collision, indicating that the branch of Paleo-Tethys Ocean or arc basin in Ailaoshan tectonic belt may have been closed in the Late Permian (263.6±2.4Ma).