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Origin of Columbia River flood basalt controlled by propagating rupture of the Farallon slab

机译：Farallon平板的传播破裂控制了哥伦比亚河洪水玄武岩的成因

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摘要

The origin of the Steens-Columbia River (SCR) flood basalts, which is presumed to be the onset of Yellowstone volcanism, has remained controversial, with the proposed conceptual models involving either a mantle plume1"5 or back-arc processes. Recent tomo-graphic inversions based on the US Array data reveal unprecedented detail of upper-mantle structures of the western USA and tightly constrain geodynamic models simulating Farallon subduction, which has been proposed to influence the Yellowstone volcanism. Here we show that the best-fitting geodynamic model depicts an episode of slab tearing about 17 million years ago under eastern Oregon, where an associated sub-slab asthenospheric upwelling thermally erodes the Farallon slab, leading to formation of a slab gap at shallow depth. Driven by a gradient of dynamic pressure, the tear ruptured quickly north and south and within about two million years covering a distance of around 900 kilometres along all of eastern Oregon and northern Nevada. This tear would be consistent with the occurrence of major volcanic dikes during the SCR-Northern Nevada Rift flood basalt event both in space and time. The model predicts a petrogenetic sequence for the flood basalt with sources of melt starting from the base of the slab, at first remelting oceanic lithosphere and then evolving upwards, ending with remelting of oceanic crust. Such a progression helps to reconcile the existing controversies on the interpretation of SCR geochemistry and the involvement of the putative Yellowstone plume. Our study suggests a new mechanism for the formation of large igneous provinces.
机译：Steens-Columbia River（SCR）洪水玄武岩的起源（据推测是黄石火山爆发的起源）一直存在争议，提出的概念模型涉及地幔柱1“ 5或后弧过程。基于美国阵列数据的图形反演揭示了美国西部上地幔结构的前所未见的细节，并严格限制了模拟法拉隆俯冲作用的地球动力学模型，这已被建议影响黄石火山作用。大约在一千七百万年前的俄勒冈州东部，一块板块被撕裂，一个相关的软流圈子板块向上热侵蚀了Farallon板块，导致在浅深度形成了板块缝隙。在动态压力梯度的驱动下，裂缝破裂了迅速向北和向南移动，并在大约200万年内，沿着俄勒冈州东部和内华达州北部的整个地区约900公里一个。这种撕裂将与SCR-内华达裂谷北部洪水玄武岩事件在时空上发生的主要火山堤一致。该模型预测了洪水玄武岩的成因序列，其熔源从板的底部开始，首先是重熔岩石圈，然后向上演化，最后是重熔地壳。这样的进展有助于调和关于SCR地球化学的解释和推定的黄石羽流的存在的现有争议。我们的研究提出了形成火成大省的新机制。

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  • 来源
    《Nature》 |2012年第7385期|p.386-389|共4页
  • 作者

    Lijun Liu; Dave R. Stegman;

  • 作者单位

    IGPP, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, USA;

    IGPP, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California 92093, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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