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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Magma emplacement process zone preserved in the roof of a large Cordilleran batholith, Wallowa Mountains, northeastern Oregon
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Magma emplacement process zone preserved in the roof of a large Cordilleran batholith, Wallowa Mountains, northeastern Oregon

机译：俄勒冈东北部沃洛阿山脉的山脉山脉基岩保留在岩浆安置过程区

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摘要

The crestal portion of the upper-crustal Wallowa batholith, northeastern Oregon, provides an exceptional three-dimensional section through a flat batholith roof which rolls over into a steep wall at elevations of about 1600-2800 m. The roof-batholith margin is interpreted as representing the frozen-in' process zone of granodiorite magma which was arrested during its ascent, thus providing a direct view into processes that operate during construction of large, shallow-level Cordilleran-type batholiths. The batholith host rock records two principal and presumably coeval emplacement processes: ductile flow largely accommodated by Theologically weak and thus severely deformed marbles in the steep wall, and voluminous stoping of rhe-ologically stronger, bedded siliciclastic rocks along the flat roof. Structures preserved along the roof suggest that the stoping was a multi-stage process involving emplacement of up to hundred meters long sills along bedding planes and formation of short connecting dikes cutting across bedding to produce sill-dike networks along the batholith-roof contact. Portions of the sill-dike networks and enclosed large rectangular roof blocks were then stoped into and continued to be mechanically disintegrated in the magma chamber. This inferred mechanism departs from the commonly assumed mode of stoped block formation solely by thermal shattering. In our view, host rocks in the process zone are fractured by dike propagation. It follows that such process of roof disruption and subsequent block stoping could be extremely rapid. In combination with other processes (e.g., roof uplift, ductile flow in weak lithologies), such rapid stoping could contribute to emplacement of voluminous and mostly non-sheeted Cordilleran-type batholiths at upper crustal levels.
机译：俄勒冈州东北部的上地壳瓦洛拉岩基的地壳部分通过平坦的岩基屋顶提供了特殊的三维剖面，该岩顶在海拔约1600-2800 m处翻成陡峭的墙。屋顶-石板岩边缘被解释为代表花岗闪长岩岩浆的冻结过程区，该过程区在上升过程中被捕，因此可以直接观察到在建造大型浅层堇青石型岩基时所进行的过程。岩蜡基岩记录了两个主要的且可能是同时期的进位过程：韧性流主要由陡峭壁中的在理论上较弱并因此严重变形的大理石所容纳，以及在平坦屋顶上大量流变学上更强的层状硅质碎屑岩的阻挡。沿屋顶保留的结构表明，停止是一个多阶段的过程，包括沿顺层平面放置长达数百米的门槛，并形成跨过顺层的短连接堤坝，从而沿岩基-屋顶接触形成沿堤坝网络。然后，将门槛堤坝网络和封闭的大型矩形屋顶块的一部分停在岩浆室内，并继续进行机械分解。这种推测的机制仅通过热破碎就脱离了通常假定的块形成停止模式。我们认为，加工区的主岩由于堤坝的传播而破裂。随之而来的是，这种屋顶破裂和随后的堵块过程可能非常迅速。结合其他过程（例如，顶板隆起，弱岩性中的韧性流），这种快速停止作用可能有助于在上地壳水平上安置大量的且大部分为无片状的堇青石型岩基。

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  • 来源
    《Journal of Volcanology and Geothermal Research》 |2012年第15期|p.61-75|共15页
  • 作者

    Jifi Zak; Krystof Verner; Kenneth Johnson; Joshua J. Schwartz;

  • 作者单位

    Institute of Geology and Paleontology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic;

    Czech Geological Survey, Klarov 3, Prague, 11821, Czech Republic Institute of Petrology and Structural Geology, Faculty of Science, Charles University, Albertov 6, Prague, 12843, Czech Republic;

    Department of Natural Sciences, University of Houston-Downtown, 1 Main Street, Houston, Texas, 77002, USA;

    Department of Geological Sciences, California State University Northridge,18111 Nordhoff Street, Northridge, California, 91330, USA;

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  • 关键词

    emplacement; granite; pluton roof; process zone; magmatic stoping; wallowa batholith;

    机译：安置花岗岩;岩体屋顶加工区岩浆停止;瓦洛瓦岩床;

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