摘要
在哀牢山—金沙江新生代钾质碱性岩浆岩带的南端 ,云南金平县大平糜棱岩化钠闪石霓石花岗岩中锆石 ,主要为“变质锆石”和具有老核新壳的“变质复合型锆石” ,它们皆具不规则状和圆化的外形 ,并常高度的富集成堆和显示有一定层位。用ELA ICP MS和SHRIMP对锆石定年 ,结果表明 ,变质复合型锆石中老核年龄为 2 4 7.9± 6 .4Ma ,新壳和变质锆石年龄为 14 5 .7± 3.4Ma。薄片观察发现 ,在岩体发生糜棱岩化之前还有一次区域变质作用 ,呈现在糜棱岩化弱的地段岩石发育柱粒变晶结构和花岗变晶结构 ,而且残留有清楚的层理 。
The Daping mylonitized riebeckite-aegirine granite is located in the southern part of the Ailaoshan-Jinshajiang Cenozoic alkaline magmatic rock belt. The zircons for dating form this granite are of two types: the metamorphic zircons and the metamorphic composite zircons which have old cores and new shells. Their crystal morphology is irregular and/or rounded. The high-degree concentration and layering of zircons are observed in rock thin sections. The results of dating are as following: the old core U-Th-Pb age is 247 Ma by using ELA-ICP-MS and the new shell U-Pb age is 145 Ma by using SHRIMP in metamorphic composite zircons. At the same time, there was a regional metamorphic process before mylonitization. In the weakly mylonitized segments the rocks have prism-granular blastic texture and granoblastic texture. The rocks have clear layering, which suggests a sedimentary-metamorphic genesis of this granite.
出处
《高校地质学报》
CAS
CSCD
2004年第3期378-384,共7页
Geological Journal of China Universities
基金
中国科学院知识创新工程重要方向性项目 (KZCX2 -SW - 117
KZCX2 - 10 1)
