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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Constructing the upper crust of the Mid-Atlantic Ridge: A reinterpretation based on the Puna Ridge, Kilauea Volcano
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Constructing the upper crust of the Mid-Atlantic Ridge: A reinterpretation based on the Puna Ridge, Kilauea Volcano

机译：构造大西洋中脊的上地壳：基于基拉韦厄火山普纳岭的重新解释

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摘要

The volcanic morphology of a number of segments of the slow spreading Mid-Atlantic Ridge (MAR) have been reinterpreted based on our understanding of dike emplacement, dike propagation, and eruption at the East Rift Zone of Kilauea Volcano, Hawaii and its submarine extension, the Puna Ridge. The styles of volcanic eruption at the submarine Puna Ridge are remarkably similar to those of the axial volcanic ridges (AVRs) constructed on the median valley floor of the MAR. We use this observation to relate volcanic processes occurring at Kilauea Volcano to the MAR. We now consider that volcanic features (e.g., seamounts and lava terraces) built on the flanks of the AVRs are secondary features that are fed from lava tubes or channels, not primary features fed directly from an underlying dike. We examine simple models of pipe flow and conclude that lava tubes can transport lava down the flanks of submarine rifts to build all of the volcanic features observed there. In addition, deep water lava tubes are strong enough to withstand the pressures of a few megapascals that the building of a volcanic structure 150 m high at the end of the tube would generate. The volumes of individual volcanic terraces and seamounts on the Puna Ridge and at the MAR are large (0.1-1 km~3) and similar to the volumes of lava flows that are broadly distributed at the subaerial East Rift Zone of Kilauea. This striking difference in the volcanic morphology on a scale of 1-2 km (producing terraces and seamounts underwater and low-relief flows on land) must be related to the enhanced cooling and to the greater mechanical stability of tubes in the submarine environment. We suggest that at the MAR a crustal magma reservoir, most likely located beneath shallow, flat sections of the segment, provides magma to the rift axis through dikes that propagate laterally tens of kilometers. The zone of dike intrusion, at least in the neighborhood of the magma body, is likely narrower than the width resurfaced by flows, yielding a crustal structure that has a rapid vertical transition from lavas to sheeted dikes. At segment ends the zone of dike intrusion is likely to be wider, giving a resulting structure with a more gradual transition from lavas to dikes.
机译：我们根据对夏威夷基拉韦厄火山东纵谷带的堤防，堤防传播和喷发及其海底扩展的理解，重新解释了缓慢扩散的中大西洋海脊（MAR）多个部分的火山形态，普纳岭。海底的普纳山脊上的火山喷发样式与MAR中间谷底构造的轴向火山山脊（AVR）的样式非常相似。我们使用这一观察结果将基拉韦厄火山发生的火山过程与MAR关联起来。我们现在认为，在AVR侧面建造的火山地貌（例如海山和熔岩阶地）是从熔岩管或渠道注入的次要特征，而不是直接从地下堤坝获得的主要特征。我们研究了管道流动的简单模型，并得出结论，熔岩管可以将熔岩沿着海底裂谷的侧面运输，从而建立在那里观察到的所有火山特征。此外，深水熔岩管的强度足以承受几兆帕的压力，以至于在管端高150 m的火山结构会产生。普那岭和MAR的单个火山阶地和海山的体积很大（0.1-1 km〜3），与基拉韦厄的东陆裂谷带广泛分布的熔岩流体积相似。 1-2公里范围内火山形态的显着差异（在水下产生阶地和海山，以及陆地上的低浮流）必须与增强的冷却以及海底环境中管道的更大机械稳定性有关。我们建议在MAR的地壳岩浆储集层，最有可能位于该段浅而平坦的部分之下，通过沿横向传播数十公里的堤坝向裂谷轴提供岩浆。至少在岩浆体附近的堤防侵入区可能比流动重铺的宽度要窄，产生的地壳结构具有从熔岩到片状堤防的快速垂直过渡。在段的尽头，堤防侵入的区域可能会更宽，从而使最终构造从熔岩过渡到堤防。

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