昌都地块小苏莽一带二叠纪变玄武岩地球化学特征及其构造环境

被引:5
作者
周会武
机构
[1] 甘肃省地质调查院
关键词
变玄武岩; 锆石U-Pb年代学; 地球化学; 裂谷; 昌都地块; 小苏莽;
D O I
10.19700/j.0379-1726.2013.02.006
中图分类号
P588.145 [];
学科分类号
摘要
宁多岩群作为北羌塘昌都地块的变质岩系之一,其形成时代的有效限定便显得至关重要。通过高精度的LA-ICP-MS(激光剥蚀等离子体质谱)锆石微区原位U-Pb同位素测年,在青海省玉树县小苏莽乡宁多村北原划为中新元古代宁多岩群的变玄武岩中获得原岩形成年龄为(272.88±0.48)Ma,将该套变玄武岩从宁多岩群中解体出来,划归中二叠统。变玄武岩具有高Ti、富Fe、偏碱的特征,呈现无Eu异常、轻稀土富集的右倾型稀土元素分布模式,微量元素分布模式为部分大离子亲石元素和高场强元素不同程度富集的大隆起型曲线。综合判断,该变玄武岩形成于大陆裂谷环境,可能与地幔柱活动有关,是羌塘地区二叠纪大规模陆内裂谷作用的地质记录。
引用
收藏
页码:153 / 165
页数:13
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