云南大平糜棱岩化碱性花岗岩的锆石特征及其地质意义

云南大平糜棱岩化碱性花岗岩的锆石特征及其地质意义

张玉泉, 夏斌, 梁华英, 刘红英, 林清茶

中国科学院广州地球化学研究所边缘海地质重点实验室广州 510640

收稿日期:2004-09-20 修回日期:2004-09-20 出版日期:2004-09-20 发布日期:2004-09-20

Characteristics of Zircons for Dating from Daping Mylonitized Alkaline Granite in Yunnan and Their Geologic Implications

ZHANG Yu-quan, XIA Bin, LIANG Hua-ying, LIU Hong-ying, LIN Qing-cha

Laboratory of Marginal Sea Geology, Guangzhou Institute of Geochemistry & South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510640, China

Received:2004-09-20 Revised:2004-09-20 Online:2004-09-20 Published:2004-09-20

摘要/Abstract

摘要： 在哀牢山一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247．9±6．4Ma，新壳和变质锆石年龄为145．7±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，由此表明该花岗岩的成因与沉积变质有关。

Abstract: 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.Th e 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.

张玉泉, 夏斌, 梁华英, 刘红英, 林清茶. 云南大平糜棱岩化碱性花岗岩的锆石特征及其地质意义[J]. J4.

ZHANG Yu-quan, XIA Bin, LIANG Hua-ying, LIU Hong-ying, LIN Qing-cha. Characteristics of Zircons for Dating from Daping Mylonitized Alkaline Granite in Yunnan and Their Geologic Implications[J]. J4.