滇西梁河地区钾长花岗岩锆石LA-ICP-MS U-Pb定年及其地质意义  

LA-ICP-MS Zircon U-Pb Dating for K-feldspar Granites in Lianghe Region,Western Yunnan and Its Geological Significance

作　　者：谢韬[1] 林仕良[1] 丛峰[1] 李再会[1] 邹光富[1] 李军敏[1] 梁婷[2] 

机构地区：[1]中国地质调查局成都地质调查中心,四川成都610082 [2]中国地质大学(武汉)地质过程与矿产资源国家重点实验室,湖北武汉430074

出　　处：《大地构造与成矿学》2010年第3期419-428,共10页Geotectonica et Metallogenia

基　　金：云南1:5万梁河县;江东;帕底幅区域地质调查项目(编号:1212010784007)的成果

摘　　要：在详细区域地质调查的基础上,对滇西梁河地区具有代表性的两件钾长花岗岩样品中的锆石进行了阴极发光图像、微区原位LA-ICP-MS微量元素分析和U-Pb定年。结果表明,梁河地区钾长花岗岩锆石显示振荡环带的内部结构,指示其岩浆成因;两件样品的锆石具有较高的Th、U含量,稀土元素总量较高,轻稀土亏损、重稀土富集,明显的的Ce正异常和Eu负异常的稀土配分模式,说明其壳源岩浆锆石特征;两件样品的锆石206Pb/238U加权平均年龄分别是(60.7±0.6)Ma和(115.8±1.0)Ma,属古新世和早白垩世花岗岩。结合区域地质特征,腾冲地块在中生代晚期-新生代早期发生多期岩浆作用,揭示滇西三江地区特提斯演化的岩浆响应,为青藏高原东缘地区地质演化的动力过程提供约束。CL imaging,LA-ICP-MS U-Pb dating and trace element analysis were carried out for the zircons from two representative K-feldspar granites in the Lianghe region,western Yunnan.The results show that the zircons display oscillatory zoning which suggests a magmatic origin.Zircons from two samples show similar REE patterns,which are high in Th,U,and REE,relative enrichment of HREE,and significant Ce positive anomalies and Eu negative anomalies.These are the characteristics of magmatic zircon of crustal origin.The weighted average 206Pb/238U ages for zircons from two samples are（60.7±0.6）Ma and（115.8±1.0）Ma,respectively,which show that the granites were formed in Paleocene and Early Cretaceous.Combined with regional geology,the multi-phases of magmatism in the Tengchong block took place in the late Mesozoic-early Cenozoic,which may be considered as magmatism response to the Tethys evolution in the Sanjiang region,western Yunnan.This offers constraints on the geological evolution in the eastern edge of Qinghai-Tibet plateau.

关 键 词：滇西 梁河 钾长花岗岩 锆石U-PB年龄 

分 类 号：P597[天文地球—地球化学]