DERIVATION OF SOME MODERN ARC MAGMAS BY MELTING OF YOUNG SUBDUCTED LITHOSPHERE
DERIVATION OF SOME MODERN ARC MAGMAS BY MELTING OF YOUNG SUBDUCTED LITHOSPHERE
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DOI：
10.1038/347662a0
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发表时间：
1990-10-18
期刊：
影响因子：
64.8
通讯作者：
DRUMMOND, MS
中科院分区：
文献类型：
--
作者：
DEFANT, MJ;DRUMMOND, MS
现代岛弧和大陆弧中的大多数火山岩可能来自地幔楔的熔融，这是由俯冲岩石圈脱水反应过程中释放的含水流体引起的。弧拉斑玄武岩和钙碱性玄武质岩浆是由地幔部分熔融产生的，然后通过晶体分馏（有或没有同化和岩浆混合）演化为更多的岩浆2-玄武岩，安山岩，英安岩和流纹岩套。虽然大多数弧岩浆是由这些成岩过程中产生的，岩石的地球化学特征的熔体直接来自俯冲岩石圈中存在于一些现代弧相对年轻和热的岩石圈正在俯冲。这些安山岩、英安岩和钠质流纹岩（英安岩似乎是最常见的产物）或它们的侵入等价物（英云闪长岩和奥长花岗岩）通常不与母体玄武岩浆有关3。在这里，我们表明，这些岩浆（称为埃达克岩）的微量元素地球化学是一致的，由部分熔融的俯冲板片的派生，特别是俯冲岩石圈年龄小于25万年似乎需要板片熔融发生。
MOST volcanic rocks in modern island and continental arcs are probably derived from melting of the mantle wedge, induced by hydrous fluids released during dehydration reactions in the subducted lithosphere1. Arc tholeiitic and calc-alkaline basaltic magmas are produced by partial melting of the mantle, and then evolve by crystal fractionation (with or without assimilation and magma mixing) to more silicic magmas2—basalt, andesite, dacite and rhyolite suites. Although most arc magmas are generated by these petrogenetic processes, rocks with the geochemical characteristics of melts derived directly from the subducted lithosphere are present in some modern arcs where relatively young and hot lithosphere is being subducted. These andesites, dacites and sodic rhyolites (dacites seem to be the most common products) or their intrusive equivalents (tonalites and trondhjemites) are usually not associated with parental basaltic magmas3. Here we show that the trace-element geochemistry of these magmas (termed 'adakites') is consistent with a derivation by partial melting of the subducted slab, and in particular that subducting lithosphere younger than 25 Myr seems to be required for slab melting to occur.