大别山中生代地壳从挤压转向伸展的时间:花岗岩的证据

被引：136

作者：

马昌前

杨坤光

明厚利

林广春

机构：

[1] 中国地质大学地球科学学院

[2] 中国地质大学地球科学学院武汉

[3] 武汉

[4] 武汉

来源：

中国科学(D辑:地球科学) | 2003年 / 09期

关键词：

锆石U-Pb年龄; 花岗岩; 伸展塌陷; 大别山;

D O I：

暂无

中图分类号：

P542 [构造运动];

学科分类号：

摘要：

采用颗粒级锆石U-Ph定年和角闪石-黑云母的Ar-Ar定年方法,测得大别山超高压变质带内刘家洼高Sr/Y花岗岩的结晶锆石年龄为135.4±2.7Ma,分流铺高Sr/Y花岗岩的角闪石和黑云母的40Ar-39Ar坪年龄分别为139.0±1.0和125.3±0.2Ma。这些岩体侵位之后,又有与伸展作用有关的铁镁质岩体和具负Sr和Eu异常的花岗岩类侵入,其同位素年龄在105～130Ma之间。两类花岗岩的地球化学对比表明,从早到晚,岩石的碱性增强,K2O含量升高,FeO/（FeO+MgO）比值增大,Sr/Y比值降低,表明从早到晚地壳岩浆房深度变浅。从早白垩世开始的地壳尺度的流变学分层以及地壳岩石的熔融与流动,促进了地壳伸展作用和深埋岩石剥露。形成于135Ma前的高Sr/Y花岗岩,是加厚地壳开始减薄以及地壳从挤压向伸展转换过程的产物。

引用

页码：817 / 827

页数：11

共 28 条

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