滇西南南澜沧江构造岩浆岩带早侏罗世火山岩的发现——兼论云南省境内印支构造旋回的上限  

The discovery of Early Jurassic volcanic rocks along the Southern Lancangjiang tectonic magmatic belt in southwest Yunnan, with a discussion on the upper limit of Indosinian tectonic cycles in Yunnan Province

作　　者：吕留彦 李静[1,3] 曾文涛 俞赛赢 孙载波 王晓峰 LÜLiuyan;LI Jing;ZENG Wentao;YU Saiying;SUN Zaibo;WANG Xiaofeng(Kunming University of Science and Technology,Kunming 650093,Yunnan,China;Guizhou Institute of Geological Survey,Guiyang 550081,Guizhou,China;Yunnan Institute of Geological Survey,Kunming 650216,Yunnan,China)

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093 [2]贵州省地质调查院,贵州贵阳550081 [3]云南省地质调查院,云南昆明650216

出　　处：《中国地质》2019年第6期1270-1283,共14页Geology in China

基　　金：中国地质调查局项目（1212011120593、1212011120595）资助~~

摘　　要：采用锆石激光剥蚀法(LA-ICP-MS)对滇西南南澜沧江火山岩带普洱市江桥—那澜一带的流纹岩进行了年代测定,获得了(196.7±2.3)Ma、(198.1±3.5)Ma的同位素年龄;表明该地区的流纹岩形成于早侏罗世,而非前人划分的晚三叠世,填补了该地区早侏罗世的火山-沉积记录。从岩石的主元素、稀土元素及微量元素资料分析,南澜沧江构造岩浆岩带早侏罗世的火山岩形成于碰撞后的伸展构造背景,可能与西侧昌宁—孟连古特提斯洋盆关闭后,俯冲岩石圈板片或造山带山根的拆沉作用相关,属后碰撞—后造山阶段岩浆活动的产物。具有典型后造山花岗岩或“A”型花岗岩的特征,其指示了印支构造旋回在滇西南地区最终结束的时间上限。The ages of rhyodacite in Jiangqiao—Nalan area of Pu'er City was determined by utilization of zircon-LA-ICP-MS in south Lancangjiang zone,and the result of U-Pb dating yielded(196.7±2.3)Ma and(198.1±3.5)Ma,which indicates that rhyolite in this area was formed in early Jurassic instead of in Late Triassic.The data fill in the record of volcanic-sedimentary activity in Jurassic's geological history.The analysis of the major elements,REE and trace elements of rocks shows that the volcanic rocks of lower Jurassic in South Lancangjiang zone were formed under the extensional tectonic background after collision,and were probably related to the subducted lithosphere plates or orogenic belt of Yamane delamination,and that they occurred after the closure of the western side of the Changning-Menglian Paleo-Tethyan oceanic basin,thus belonging to the products of lava.The features of lower Cretaceous in this area were typically associated with the POG(post-orogenic granite)or A2 granite.These data constrain the final time of Indosinian cycle.The granite has the feature of post-orogenic granite or"A"type granite,and it indicates the termination time of Indo-Chinese cycle in southwestern Yunnan.

关 键 词：滇西 南澜沧江带 流纹岩 U-Pb年龄 地球化学 构造环境 

分 类 号：P542[天文地球—构造地质学]