利用地球化学方法判别大陆玄武岩和岛弧玄武岩
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P588.145 P595

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国家自然科学基金资助项目(40472044);中国地质调查局综合研究项目(1212010611804)


The discrimination between continental basalt and island arc basalt based on geochemical method
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    摘要:

    大陆地壳或岩石圈的混染作用可以给出似消减带信号,并导致将受到混染的大陆玄武岩误判为岛弧玄武岩。没有受到混染的软流圈(或地幔柱)源大陆玄武质岩石通常是以(Th/Nb)N〈1、Nb/La≥1、低^87Sr/^86Sr(t)比值、高εNd(t)值及La/Nb和La/Ba比值与洋岛玄武岩相似并以具有缺乏Nb、Ta、Ti负异常的“隆起”状多元素地幔标准化分配型式为特征。当在所研究的火山岩系中发现有未受到混染的软流圈(或地幔柱)源玄武质岩石存在,基本上就可以排除它们有属于岛弧或活动大陆边缘火山岩系的可能。对于那些具有消减带信号的基性熔岩,可以根据Zr含量和Zr/Y比值,或利用Zr/Y—Zr图解,判断它们是否真正是岛弧或活动大陆边缘玄武岩。

    Abstract:

    Contamination by continental crust or lithosphere can yield subduction-type signatures and lead to the misidentification of contaminated continental basalts as arc related ones. Uncontaminated asthenosphere (or plume) -generated continental basaltic rocks are normally characterized by (Th/Nb)N<1,Nb/La≥1, low87Sr/86Sr(t) ratios, high εNd(t)values, similar La/Nb and La/Ba ratios to ocean island basalts (OIB) and “hump=shaped”mantle-normalized multi-element patterns without negative Nb, Ta and Ti anomalies. As the uncontaminated asthenosphere (or plume) -generated basaltic rocks have been found in the studied volcanic successions, the possibility can be basically excluded that they belong to island-arc or active continental margin volcanic rocks. For the basic lavas with subduction-type signatures, we can judge whether they are really island-arc or active continental margin basalts by studying Zr contents and Zr/Y ratios or Zr/Y[CD*2]Zr diagram.

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夏林圻 夏祖春 徐学义 李向民 马中平,2007,利用地球化学方法判别大陆玄武岩和岛弧玄武岩[J].岩石矿物学杂志,26(1):77~89. XIA Lin-qi, XIA Zu-chun, XU Xue-yi, LI Xiang-min, MA Zhong-ping,2007,The discrimination between continental basalt and island arc basalt based on geochemical method[J]. Acta Petrologica et Mineralogica,26(1):77~89.

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  • 最后修改日期:2006-08-08
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