新疆塔克札勒蛇绿混杂岩中安山岩的地球化学特征及其构造环境

塔克札勒的中性熔岩有两种:一为玄武安山岩;二为安山岩。主元素判别安山岩类属于亚碱性玄武岩类。两者具有完全一致的LREE相对于HREE富集的分配型式,亦具有同样明显的Eu负异常。微量元素蛛网图显示其均具Nb-Ti负异常,与Grenada和LAntilles那种碱性玄武岩类相当,且与塔克札勒蛇绿岩带中的玄武岩有成因联系。据构造环境判别图判别,安山岩类又具洋岛碱性玄武岩的特征。据此推测该安山岩类属蛇绿岩成员,其可能产于俯冲带之上(SSZ)的岛弧环境。而该蛇绿岩则属于某种弧间构造背景的蛇绿岩。

ANDESITE OF TAKEZHALE OPHIOLITE COMPLEX IN XINJIANG: GEOCHEMICAL CHARACTERISTICS AND TECTONIC SETTING

The intermediate lava in Takezhale can be subdivided into two groups, i.e., basaltic andesite and andesite. Major elemental analysis shows that the andesite belongs to the subalkaline basalt, and is completely compatible with the enrichment of the LREE relative to the HREE and shows obvious Eu negative anomaly. The trace element spider diagrams clearly display Nb-Ti negative anomalies, which is similar to the cases with the alkaline basalts in Grenada and L. Antilles. The andesite is linked to the basalt of Takezhale ophiolite belt. In the light of tectonic discrimination diagrams, the andesite is characterized by alkaline basalt of ocean-island setting. It is suggested in this paper that the andesite is a member of the ophiolite suits, which were most probably formed in an island-arc environment of supra-subduction zone (SSZ) and the ophiolite belongs to the type of arc tectonic setting.