铌与钽的某些地球化学问题

被引:118
作者
赵振华
熊小林
王强
乔玉楼
机构
[1] 中国科学院广州地球化学研究所
关键词
铌; 钽; 地球化学; 金红石分配系数; 基性岩墙群; 大火成岩省; 高演化花岗岩;
D O I
10.19700/j.0379-1726.2008.04.003
中图分类号
P595 [元素地球化学];
学科分类号
070902 ;
摘要
针对地球圈层之间Nb、Ta质量不平衡的难题,较系统收集分析了我国基性岩墙(脉)群、太古宙基性火山岩、碱性岩、大火成岩省火山岩,俯冲带中富Nb玄武岩、高压变质岩、花岗岩类的Nb、Ta含量、比值、相关同位素组成以及Nb、Ta实验地球化学资料。这些资料表明,Nb、Ta在这些岩类中的分布呈现非常不均匀变化,除花岗岩外,上述岩石的Nb/Ta比值均高于或近于球粒陨石值17.5。花岗岩中的幔源斜长花岗岩及与裂谷、热点环境有关的碱性花岗岩Nb/Ta比值近于地球平均值,而普通S型及I型花岗岩,特别是高演化花岗岩,Nb/Ta比值均明显低于球粒陨石(<10),甚至呈现Nb/Ta≤1。这些资料表明,在不均匀的地幔中可能存在呈布丁状分布的Nb/Ta比值高于球粒陨石的储源。金红石的稳定性及Nb、Ta分配系数实验资料不支持地球深部存在高Nb/Ta比值的含金红石榴辉岩。
引用
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页码:304 / 320
页数:17
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