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    新疆尾亚矿区3期岩浆混合作用的初步研究

    Three-stages magma mixing in the Weiya ore district, Xinjiang

    • 摘要: 提要:新疆东天山的尾亚钒钛磁铁矿矿区,发育3期岩浆混合作用。第一期为辉长质与花岗质岩浆混合,并生成闪长质岩石;第二期为闪长质与花岗质岩浆的混合,生成了石英二长质岩浆;第三期为石英二长岩浆与闪长质岩浆的混合。在各类岩石氧化物对SiO2的哈克图解上,尾亚3期岩浆混合岩石的投影点分别呈相关的线性关系。在稀土和微量元素方面,3期岩浆混合作用形成的岩石分别表现出相近的地球化学特征,配分曲线形态各自相似,形成的过渡岩石──岩浆混合岩类与各自的端元岩石具有继承关系。3期岩浆混合作用之间具有明显的继承性:第一期形成的岩浆混合岩,成分相当于闪长岩,与第二期岩浆混合的基性端元属同类岩石,且与第二期各类岩石具有相似的地球化学特征;第二期形成的石英二长闪长岩,与第三期的端元岩石石英二长斑岩体完全可以对比。尾亚地区的3期岩浆混合作用表明,混合作用可以是多阶段、多期次的,本区火成岩类最初的母岩浆是酸性的陆壳硅铝质和基性的幔源铁镁质岩浆,岩浆混合作用反映了本区壳幔相互作用的本质。

       

      Abstract: Abstract:Three-stage magma mixing occurred in the Weiya vanadium-bearing titianomagnetite ore district, East Tianshan, Xinjiang. The first stage was mixing of gabbroic and granitic magmas, which formed dioritic rock; the second stage was mixing of dioritic and granitic magmas, which formed quartz monzonitic rock; the third stage was mixing of quartz monzonitic and dioritic magmas. The data points of the rocks produced during the third stage of magma mixing show a linear relation in the Hake diagrams of main oxides vs. SiO2. The rocks formed in three stages of magma mixing show similar geochemical characteristics in terms of REE and trace elements and their distribution patterns are also similar, and the transitional rocks-hybrid rocks formed during magma mixing have inheriting relations with their respective end-member rocks. The inheriting relations of the three stages of magma mixing are as follows: the first stage gave rise to hybrid rock with a composition equivalent to that of diorite, which belongs to the same type of rock as the basic end-member rock of the second stage and displays similar geochemical characteristics to those of various types of rock formed in the second stage; and the quartz monzodiorite formed in the second stage can be completely correlated with the end-member rock—quartz monzonite-porphyry—of the third stage. The three stages of magma mixing in the Weiya area might suggest that magma mixing can occur in multiple stages and that the primary parent magma of igneous rocks in the area was derived from continental crustal acid sialic magma and mantle-derived mafic magma, and magma mixing reflects the essence of crust-mantle interaction in this area.

       

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