滇西保山地块铁厂中新世花岗岩成因与构造意义  

Petrogenesis and tectonic implications of the Tiechang Miocene granite in the Baoshan Block in western Yunnan

作　　者：叶雅琪 孙祥[1] 司晓博 苗珂 郑明俊 梁晓雅 YE YaQi;SUN Xiang;SI XiaoBo;MIAO Ke;ZHENG MingJun;LIANG XiaoYa(School of Earth Science and Mineral Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质大学地球科学与资源学院,北京100083

出　　处：《岩石学报》2024年第6期1870-1886,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金重大研发计划重点支持项目(92162215);高等学校学科创新引智计划(BP0719021)联合资助.

摘　　要：滇西保山地块新生代岩浆岩是理解印度-欧亚板块斜向碰撞带新生代构造演化和动力学背景的窗口。本文对保山地块铁厂地区中新世二云母花岗岩和含电气石二云母花岗岩开展了岩石地球化学、锆石U-Pb年代学和Hf同位素组成研究。结果表明二云母花岗岩和含电气石二云母花岗岩的岩浆锆石U-Pb年龄分别为18.1±0.1Ma和16.9±0.2Ma,反映岩浆岩形成于中新世。两类花岗岩具有高硅(SiO 2=73.7%~74.2%),富钾(K 2O=6.3%~6.7%,K 2O/Na 2O>1),且相对高碱(K 2O+Na 2O=8.8%~9.3%)的特征,属钾玄岩系列,为强过铝质S型花岗岩。两类花岗岩的CaO/Na 2O比值介于0.25~0.39,具有低Sr(56×10^(-6)~79×10^(-6))、低Ba(155×10^(-6)~211×10^(-6))、高Rb/Sr比值(4.6~6.2)特征。二云母花岗岩的锆石εHf(t)值为-12.1~-1.5。这些特征表明铁厂中新世花岗岩是变泥质岩脱水部分熔融的产物。结合同时代西南三江地区崇山剪切带淡色花岗岩和喜马拉雅淡色花岗岩的对比分析,表明铁厂中新世花岗岩可能形成于伸展构造环境。The Cenozoic magmatic rocks in the Baoshan Block in western Yunnan are a window to understand the tectonic evolution and dynamic setting of the India-Eurasia oblique collision zone during Cenozoic.This study presents petrogeochemical,zircon U-Pb geochronological,and Hf isotopic composition data on the Miocene two-mica granite and tourmaline-bearing two-mica granite in the Tiechang area in the Baoshan Block.The results show that the zircon U-Pb ages of the two-mica granite and the tourmaline-bearing two-mica granite are 18.1±0.1Ma and 16.9±0.2Ma,respectively,indicating that the granites were formed in the Miocene.Both types of granite have high Si(SiO 2=73.7%~74.2%),K-rich(K 2O=6.3%~6.7%,K 2O/Na 2O>1),and relatively high in alkali(K 2O+Na 2O=8.8%~9.3%),belonging to the potassium calc-alkaline series,and are strongly peraluminous S-type granites.The CaO/Na 2O ratios of the two types of granites range from 0.25 to 0.39,with low Sr(56×10^(-6)~79×10^(-6)),low Ba(155×10^(-6)~211×10^(-6)),and high Rb/Sr ratios(4.6~6.2).TheεHf(t)values of zircons from the two-mica granite range from-12.2 to 1.5.These characteristics indicate that the Tiechang Miocene granites are products of partial melting of dehydrated pelitic rocks.Comparative analysis of contemporaneous granites from the Chongshan shear zone in the Southwest Sanjiang area and the Himalayan leucogranite suggests that the Miocene granites of Tiechang may have formed in an extensional tectonic setting.

关 键 词：中新世花岗岩 地球化学 锆石U-PB年代学 锆石HF同位素 保山地块 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]