哀牢山构造带南段扭只二长花岗斑岩地球化学特征及其锆石U-Pb年代学研究  

Petrogeochemistry and zircon U-Pb chronology of the Niuzhi monzonitic porphyry in southern segment of Ailao Mountain tectonic belt

作　　者：孙崇波[1,2] 李忠权[1] 王道永[1] 许远平 李友余 

机构地区：[1]成都理工大学沉积地质研究院,四川成都610059 [2]四川冶金地质勘查局水文工程大队,四川成都611730 [3]四川冶金地质勘查局606大队,四川成都611730

出　　处：《中国地质》2016年第1期111-119,共9页Geology in China

基　　金：中国地质调查局项目(1212010880406;1212011120582)资助~~

摘　　要：本文对云南墨江县扭只二长花岗斑岩进行了锆石U-Pb年代学、岩石地球化学分析。LA-ICP-MS锆石U-Pb测年显示扭只二长花岗斑岩年龄为（263.5±1.7）Ma,形成于晚二叠世。岩石地球化学分析显示：扭只二长花岗斑岩Si O2含量为55.30%-74.37%,全碱（Na2O＋K2O）含量2.56%-7.57%,且Na2O〉K2O;岩石富集轻稀土,负铕异常明显（δEu：0.74-1.06）,相对富集Sc、Co、Cs、As等元素,亏损Cr、Ni、Zn、Rb、Sr、Ba、Zr、Ta、Th、U、W等元素。根据图解显示扭只二长花岗斑岩形成于岛弧向陆陆碰撞或者陆弧碰撞的构造环境,表明哀牢山构造带的古特提斯支洋或弧后盆地在晚二叠世（（263.5±1.7）Ma）可能已经闭合。This study presents bulk petrogeochemistry and zircon U- Pb dating results for the Niuzhi monzonitic porphyry in Mojiang, Yunnan. LA-ICP-MS zircon U-Pb dating results show that the Niuzhi monzonitic porphyry formed in the Late Permian（263.5 ±1.7Ma）. The Niuzhi monzonitic porphyry is characterized by Si O2 content of 55.30%-74.37%, alkali（Na2O＋K2O） 2.56%-7.57%, and Na2 O higher than K2 O. It is enriched in LREE and Sc, Co, Cs, As, and depleted in Cr, Ni, Zn, Rb, Sr, Ba, Zr, Ta, Th, U,W, with negative Eu anomalies（δEu 0.74-1.06）. According to the diagrams, the Niuzhi monzonitic porphyry formed in the tectonic environment of island arc-continent or continental-arc collision,indicating that the branch of Paleo-Tethys Ocean or arc basin inAilaoshan tectonic belt may have been closed in the Late Permian（263.5 ± 1.7Ma）.

关 键 词：二长花岗斑岩 锆石U-PB年代学 岩石地球化学 同碰撞期花岗岩 

分 类 号：P597.3[天文地球—地球化学] P588.13[天文地球—地质学]