新疆塔克札勒蛇绿混杂岩中玄武质熔岩地球化学特征及其成因讨论

GEOCHEMICAL CHARACTERISTICS AND TECTONIC SETTINGS FOR BASALTS IN TAKEZHALE OPHIOLITE IN EAST JUNGGAR, XINJIANG

塔克札勒蛇绿混杂岩玄武岩的SiO2 和MgO高,同时较富集Cr、Ni及Co等过渡族元素,具有玻安岩特征;微量元素以富集LILE(Ba,Rb,Sr等)而亏损HFSE(Nb、Ta、Zr、Hf等)为特征;该玄武岩具LREE平坦或弱亏损、HREE亏损的分配型式;构造环境判别图解指示该玄武岩形成于弧前环境。地球化学特征与其它地质特征表明该蛇绿岩代表了古亚洲洋消亡过程中的洋壳残片。

The basalts in Takezhale ophiolitic mélange show the characteristics of boninite, i.e., being characterized by high SiO_2, MgO and enrichment in transition elements such as Cr, Ni and Co etc. The spider diagram for trace elements indicates that they are enriched in LILE (Ba, Rb, Sr etc.) but are depleted in HFSE (Nb, Ta, Zr, Hf etc.). The REE distributions show flat LREE trends but HREE-depleted patterns. Discrimination diagrams demonstrate that the basalts were formed in forearc in terms of tectono-environment. Geochemical and other geological features suggest that the ophiolitic mélange represents the ocean crust tags resulted from the withering away of the Palaeo-Asian ocean.