新疆西天山备战铁矿成矿作用初探

Primary Study on Mineralization of Beizhan Iron Deposit in Xitianshan Area

摘要:

该文在野外地质调查基础上，对备战铁矿区内的火山岩和矿石进行了详细的矿物学和岩石地球化学研究，并深入讨论了矿床成因。研究表明，该区的主要赋矿围岩为火山岛弧玄武岩，其与磁铁矿有着类似的稀土元素配分模式，说明二者有成因上的联系。成矿物质可能来源于北天山洋块向伊犁板块之下俯冲过程中软流圈上涌形成的富铁玄武质岩浆。受洋块俯冲作用影响，富铁玄武质岩浆沿北天山压扭性深大断裂底侵，并经历了一定的结晶分离或同化混染作用，最后在中地壳形成一套演化的玄武质（安山质）岩浆，并在岩浆晚期阶段发生富铁岩浆和硅酸盐岩浆的分离，此时，火山岩中的普通辉石受岩浆晚期的热液作用影响蚀变为透辉石，发生了Si，Ca，Mg的富集和Fe，Al，Ti的缺失，一定程度上促进了含铁矿浆的富集。

Abstract:

On the basis of geological field survey, mineralogy and rock geochemistry of magmatic rocks and ore bodies have been studied in detail, and the origin of this deposit has been discussed as well. It is showed that main orehosting rocks are volcanic island arc basalts, which have similar REE patterns with magnetite. It indicates that there is a relation between them. Oreforming materials may be ironrich basaltic magma which were formed by asthenosphere during the subduction period of Beitianshan ocean to Yili plate. Affected by the subduction of oceanic blocks, ironrich basaltic magma intruded along Beitianshan deep shear belt, and experienced a certain amount of separation or crystallization assimilation effect. Finally, a series of evoluted basaltic crust(andesitic) magma has been formed in the middle crust, and the separation of ironrich silicate magma and lava magma occurred in the late stage. Meanwhile, augite in magmatic rocks turned into diopside affected by late magmatic hydrothermal alteration impact, occurred the absence of Si, Ca, Mg and enrichment of Fe, Al, Ti. It has promoted the enrichment of iron orebearing magma in a certain extent.