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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Subduction of the South Chile active spreading ridge: A17 Ma to 3 Ma magmatic record in central Patagonia (western edge of Meseta del Lago Buenos Aires, Argentina)
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Subduction of the South Chile active spreading ridge: A17 Ma to 3 Ma magmatic record in central Patagonia (western edge of Meseta del Lago Buenos Aires, Argentina)

机译：智利南部活跃扩散脊的俯冲：巴塔哥尼亚中部（阿根廷梅塞塔德尔拉戈布宜诺斯艾利斯的西边缘）A17 Ma至3 Ma岩浆记录

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摘要

The Chile Triple Junction is a natural laboratory to study the interactions between magmatism and tectonics during the subduction of an active spreading ridge beneath a continent. The MLBA plateau (Meseta del Lago Buenos Aires) is one of the Neogene alkali basaltic plateaus located in the back-arc region of the Andean Cordillera at the latitude of the current Chile Triple Junction. The genesis of MLBA can be related with successive opening of slabs windows beneath Patagonia: within the subducting Nazca Plate itself and between the Nazca and Antarctic plates. Detailed ~(40)Ar/~(39)Ar dating and geochemical analysis of bimodal magmatism from the western flank of the MLBA show major changes in the back-arc magmatism which occurred between 14.5 Ma and 12.5 Ma with the transition from calc-alkaline lavas (Cerro Plomo) to alkaline lavas (MLBA) in relation with slab window opening. In a second step, at 4-3 Ma, alkaline felsic intrusions were emplaced in the western flank of the MLBA coevally with the MLBA basalts with which they are genetically related. These late OIB-like alkaline to transitional basalts were generated by partial melting of the subslab asthenosphere of the subducting Nazca plate during the opening of the South Chile spreading ridge-related slab window. These basalts differentiated with small amounts of assimilation in shallow magma chambers emplaced along transtensional to extensional zones. The close association of bimodal magmatism with extensional tectonic features in the western MLBA is a strong support to the model of Patagonian collapse event proposed to have taken place between 5 and 3 Ma as a consequence of the presence of the asthenospheric window (SCR-1 segment of South Chile Ridge) below the MLBA area.
机译：智利三重交界处是一个自然实验室，用于研究在大陆下方活跃的扩张脊俯冲过程中岩浆作用与构造之间的相互作用。 MLBA高原（Meseta del Lago布宜诺斯艾利斯）是新近纪碱性玄武岩高原之一，位于安第斯山脉山脉的后弧区域，在当前的智利三结交界处。 MLBA的成因可能与巴塔哥尼亚以下的平板窗的连续打开有关：俯冲的纳斯卡板块内部以及纳斯卡和南极板块之间。 MLBA西侧的双峰岩浆的〜（40）Ar /〜（39）Ar年代学详细和地球化学分析显示，弧后岩浆的主要变化发生在14.5 Ma至12.5 Ma之间，由钙碱性转变而来。熔岩（Cerro Plomo）与碱性熔岩（MLBA）的关系与平板窗户的打开有关。第二步，在4-3 Ma时，将碱性长英质侵入体与与其遗传相关的MLBA玄武岩共置于MLBA的西侧。这些后期的OIB样碱性至过渡玄武岩是由南智利扩张脊相关平板窗口打开期间俯冲纳斯卡板块的软流下软流圈部分熔化而产生的。这些玄武岩在沿伸展带至伸展带的浅岩浆室中具有少量的同化作用。 MLBA西部地区双峰岩浆作用与伸展构造特征的紧密联系为巴塔哥尼亚崩塌事件的模型提供了有力支持，该模型被认为是由于软流层窗口（SCR-1区段）的存在而发生在5至3 Ma之间MLBA区域下方的南智利山脊）。

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  • 来源
    《Journal of Volcanology and Geothermal Research》 |2010年第4期|319-339|共21页
  • 作者

    E. Boutonnet; N. Arnaud; C. Guivel; Y. Lagabrielle; B. Scalabrino; F. Espinoza;

  • 作者单位

    CNRS-UMR 5243 Geosciences Montpellier, Universite Montpellier 2, CC 60, Place Eugene Bataillon, Montpellier Cedex5, 34095, France CNRS-MR 5570 Laboratoire des Sciences de la Terre, ENS-UCBL Lyon, Universite de Lyon1, 2 rue Raphaeel Dubois, Villeurbanne cedex, 69622, France;

    CNRS-UMR 5243 Geosciences Montpellier, Universite Montpellier 2, CC 60, Place Eugene Bataillon, Montpellier Cedex5, 34095, France;

    UMR 6112 Planetologie et Geodynamique, Universite de Nantes, Nantes, France;

    CNRS-UMR 5243 Geosciences Montpellier, Universite Montpellier 2, CC 60, Place Eugene Bataillon, Montpellier Cedex5, 34095, France;

    CNRS-UMR 5243 Geosciences Montpellier, Universite Montpellier 2, CC 60, Place Eugene Bataillon, Montpellier Cedex5, 34095, France;

    Departemento de Geologia, Universidad de Chile, Castilla 13518, Correo 21, Santiago, Chile;

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  • 正文语种 eng
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  • 关键词

    subduction; spreading ridge; bimodal back-arc magmatism; Patagonia;

    机译：俯冲蔓延的脊双峰弧后岩浆作用;巴塔哥尼亚;

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