埃达克岩研究现状

    A REVIEW ON ADAKITE

    • 摘要: 埃达克岩是一套钙碱系列岩浆岩,其主要地球化学特征为SiO2 ≥ 56%,Al2O3 ≥ 15%,MgO通常小于3%,低重稀土元素和Y(Y ≤ 18×10-6,Yb ≤ 1.9×10-6),高Sr(多数大于400×10-6),无Eu异常或有轻微的负Eu异常,其成因主要有两类,一种为由俯冲板片的熔融形成,另一种由底侵玄武质下地壳熔融形成,埃达克岩具有重要的成矿意义。

       

      Abstract: Adakite was proposed over a decade ago. It is a kind of acid-intermediate and calc-alkaline igneous rock, with the stickup characteristics of SiO2 ≥ 56%, Al2O3 ≥ 15%, relatively depletive HREE and Y(Y ≤ 18×10-6, Yb ≤ 1. 9×10-6), high Sr(> 400×10-6), La/Yb and Sr/Y, as well as positive Sr anomaly but absent or slightly negative Eu anomaly. There are two types of adakites with different petrogenesis:one is formed by the melting of subducting young(≤ 25-30 Ma) slab, and the other is formed by the partially melting of basaltic lower crust under the continental accretion setting. Adakites are important indicators of ore deposits.

       

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