滇西“三江”南段几个花岗岩的锆石SHIRMP U-Pb定年及其地质意义  

Zircon SHRIMP dating of several granites and geological significance in southern part of"Sanjiang"area,western Yunnan province.

作　　者：喻学惠[1] 肖晓牛[1] 杨贵来 莫宣学[1] 曾普胜 王晋璐[1] 

机构地区：[1]中国地质大学,地质过程与矿产资源国家重点实验室及岩石圈构造、深部过程及探测技术教育部重点实验室,北京100083 [2]云南省地质矿产勘查局,昆明650215 [3]云南省财贸大学,昆明650221

出　　处：《岩石学报》2008年第2期377-383,共7页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(编号：2002CB412603);国家自然科学基金面上项目(编号：40572046)。

摘　　要：工浪二长花岗岩及芒哈和湖广寨似斑状花岗闪长岩分布在滇西"三江"褶皱带南段,大地构造上位于冈底斯-念青唐古拉褶皱系南段昌宁-孟连褶皱带与南腊-西盟褶皱束的临昌-澜沧复背斜南部。本文提供了这三个花岗岩的岩石学特征、主量元素和微量稀土元素地球化学分析数据,并对这三个岩体中分离出的锆石进行了SHRIMP U-Pb同住素定年。结果显示,该花岗岩的全岩化学具有偏铝值花岗岩特征,其形成时代非常相近,在40.9～40Ma范围,与整个滇西地区新生代岩浆作用的高峰期(45～30Ma)一致。结合花岗岩产出的大地构造背景,提出该花岗岩的成因很可能与扬子块体和印缅地块相对俯冲和斜向碰撞引发的地幔上涌及地壳熔融作用以及壳源和幔源岩浆的混合作用有关。该SHRIMP U-Pb定年结果进一步证明,在滇西"三江"地区喜马拉雅期构造运动的影响范围远比以往的认识要宽得多。因此,重新厘定喜马拉雅期构造运动在"三江"广大地区的表现形式及动力学条件是非常必要的。Gonglang granite, Manghao and Huguangzai like-porphyritic granodiorites distributed at the south end of Changning-Menglian folded belt and Nanna-Ximeng folded belt, which are subtectonic unit of the Gangdisi-Nianqingtangula folded belt. This paper provide the petrological characteristics and analysis on the major elements, REE and trace elements, and SHRIMP isotopic dating of the Zircon separated from three granite. The research showed that, the granite chemistry of the whole rocks has the characteristics like peraluminous granite, the formed time of three granites is very closely, 40.9 -40.0Ma, consistent with high peak period of Cenozoic magmatism of the ＂Sanjiang＂ area of Western Yunnan. For this reason, combining SHRIMP U-Pb dating with tectonic setting, we suggested, the genesis of the granites may be related to mantle upwelling and mixing coming from crustal and mantle magma caused by collision and subduction of the Yangtze block and India-Burma block. The SHRIMP dating of the granites further proved, the scale of Himalaya orogeny may be very extensive than that before in Western Yunnan. Therefore, to determine again the forms and dynamics of Himalaya orogeny in ＂sanjiang＂ area, Western Yunnan would be required.

关 键 词：滇西“三江”地区 花岗岩 锆石SHRIMP U—Pb定年 

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