新疆磁海铁矿区镁铁-超镁铁岩地球化学特征及其地质意义

Geochemical characteristics of mafic-ultramafic rocks in the Cihai ore district, Xinjiang, and their geological significance

磁海铁矿床地处塔里木盆地北缘北山成矿带内,为一与镁铁-超镁铁岩有关的岩浆分异-矿浆贯入-热液交代型复成因铁矿床。对磁海矿区镁铁-超镁铁岩的岩石学特征和岩石地球化学特征等进行了较为系统的研究,认为这套镁铁-超镁铁岩石属于铁质钙碱性玄武岩系列。稀土及微量元素特征与原始地幔成分接近,表明岩浆上升侵位过程中局部遭受陆壳混染。结合前人的研究成果,认为该矿床形成于后碰撞拉张构造环境。原始岩浆的结晶分异和后期热液蚀变对磁海铁矿形成和富集起重要作用。

Cihai iron deposit, located in the Beishan metallogenic belt, the northern margin of the Tarim craton, is a multiple genesis deposit related to the mafic-ultramafic rocks, which experenced magmatic differentiation, ore magma injection and hydrothermal metasomatism. Based on systematic research on the petrology and geochemistry of mafic-ultramafic rocks in the Cihai area, it is considered that the suit of mafic-ultramafic rocks belongs to calc-alkaline series. The REE and trace element patterns are similar to the primary mantle but are partly contaminated by continental crust during the magma evolution and emplacement. Considering previous results, it is suggested that the deposit formed in an extensional environment in post-collisional stage. Both the magmatic differentiation and hydrothermal alteration played important roles in mineralization of the Cihai deposit.