摘要
系统研究了西秦岭下拉地超基性岩的地质与地球化学特征,结果表明:下拉地超基性岩具有低SiO_2、富Mg和贫碱特点;变质原岩主要属于橄榄岩类;不同岩石类型之间微量元素及稀土元素的分布具有一定差异;下拉地岩体的原生超基性岩岩浆主要起源于上地幔,成因类型属于俯冲带地幔橄榄岩;岩浆演化过程中受到壳源物质的加入和海相碳酸盐物质的加入,造成下拉地超基性岩高Al_2O_3、高CaO的特殊地球化学组成特点。笔者对由于蚀变作用影响形成的地球化学特征的原因进行了初步探讨。
The geological and geochemical characteristics of Xialadi ultrabasic rock of western Qinling were studied systematically in this paper. The results show that the characterization of Xialadi ultrabasic rocks is low SiO2, Mg rich and alkaline poor, in which metamorphic preexisting rocks belongs to the class of peridotite. The distribution of trace elements and rare earth elements （REE） among various rock types is different. The primary magma of Xialadi ultrabasic rocks originates from upper mantle, whose genetic type belongs to the mantle peridotite of subduction zone. Materials of crustal source and marine carbonate were added to Xialadi ultrabasic magma during its evolution, which resulted in the special geochemical composition characteristics of Xialadi ultramafic rocks with high Al2O3 and CaO. In this paper, a preliminary discussion was carried out on the reasons of the differences in geochemical characteristics of Xialadi ultrabasic rocks due to the effects of alteration.
出处
《西北地质》
CAS
CSCD
2012年第3期48-56,共9页
Northwestern Geology
基金
国家科技重大专项(2011ZX05008-00W-X0)
甘肃国土资源厅项目(1:250000"岷县幅"地质矿产调查项目)
关键词
下拉地
超基性岩
地球化学
岩浆成因
构造意义
Xialadi
ultrabasic rock
geochemistry
magma genesis
tectonic implications
