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首页> 外文期刊>GSA Bulletin >Geochemistry of Mississippian tuffs from the Ouachita Mountains, and implications for the tectonics of the Ouachita orogen, Oklahoma and Arkansas
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Geochemistry of Mississippian tuffs from the Ouachita Mountains, and implications for the tectonics of the Ouachita orogen, Oklahoma and Arkansas

机译：沃希托山脉密西西比凝灰岩的地球化学及其对沃希托造山带，俄克拉荷马州和阿肯色州构造的影响

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摘要

The Ouachita orogeny was the result of plate convergence at the southern margin of the North American continent, although the nature of the converging southern plate and the direction of subduction remain uncertain. The presence of areally extensive tuff layers interbedded with shale in the Mississippian Stanley Group of the Ouachita Mountains, Oklahoma and Arkansas, provides the potential to define the tectonic environment of volcanism from the geochemistry of the tuffs and thereby delimit the subduction configuration. The tuffs contain relic primary magmatic quartz, plagioclase, and alkali feldspar and range from crystal- to vitric-rich. Mineralogical sorting and diagenetic effects have caused chemical variability within individual tuff units, but overall the tuffs have retained their primary igneous geochemical characteristics. The Beavers Bend and Hatton tuffs are geochemically very similar and are more evolved (higher SiO2, Rb, Th, REE; lower Sr, Ba) than the Mud Creek tuff. The stratigraphically equivalent Sabine Rhyolite is geochemically distinct from the tuffs, having less fractionated rare earth element (REE) patterns and different trace element ratios. Both the Ouachita tuffs and Sabine Rhyolite have the geochemical characteristics of subduction-related magmas (for example, strong depletion of Nb and Ta relative to other incompatible trace elements). Consideration of trace element systematics in the tuffs compared to those of modern high-silica volcanic rocks from different subduction-related tectonic settings suggests a continental arc origin and implies southward subduction beneath a southern continent during Carboniferous ocean basin closure.
机译：瓦希托造山运动是北美大陆南缘板块收敛的结果，尽管南极板块收敛的性质和方向 组中，页岩夹杂着面积很大的 凝灰岩层，提供了 定义潜力从凝灰岩的地球化学中了解火山活动的构造环境，从而界定俯冲构造。凝灰岩包含遗迹初级岩浆石英， 斜长石和碱金属长石，范围从富含晶体的玻璃到 玻璃。矿物学分类和成岩作用已在单个凝灰岩单位内引起化学变异，但 总体上凝灰岩保留了其主要的火成地球化学 特征。海狸弯头和哈顿凝灰岩在地球化学上非常相似，并且演化程度更高（SiO 2 ，Rb，Th，REE较高； Sr，Ba较低）比泥溪凝灰岩。地层上等价的萨宾流纹岩在地球化学上不同于凝灰岩，具有较少的稀土元素（REE）格局和不同的微量元素比率。瓦希塔凝灰岩 和Sabine流纹岩都具有与 俯冲有关的岩浆的地球化学特征（例如， Nb和Ta相对于其他物质而言强烈消耗不兼容的跟踪元素）。与不同俯冲相关构造环境中的现代高硅火山岩中的凝灰岩中微量元素系统的考虑相比，表明大陆弧石炭纪 海洋盆地封闭期间，南部大陆下方的成因和暗示 向南俯冲。

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  • 来源
    《GSA Bulletin》 |1994年第9期|1158-1171|共14页
  • 作者

    JENNIFER LOOMIS; BARRY WEAVER; HARVEY BLATT;

  • 作者单位

    School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019|Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131;

    School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019;

    School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019;

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