Seismic imaging of magma sills beneath an ultramafic-hosted hydrothermal system
Seismic imaging of magma sills beneath an ultramafic-hosted hydrothermal system
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DOI：
10.1130/g38795.1
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发表时间：
2017-05-01
期刊：
影响因子：
5.8
通讯作者：
Sohn, Robert A.
中科院分区：
文献类型：
--
作者：
Canales, J. Pablo;Dunn, Robert A.;Sohn, Robert A.
大洋中脊火山段的热液循环从地壳岩浆体中提取热量。然而，驱动超镁铁岩露头（地幔岩在低岩浆供应环境中被折返）中热液循环的热源仍然是个谜。在这里，我们使用一个三维P波速度模型来自主动源广角折射反射海底地震仪数据和叠前深度偏移图像来自多道地震反射数据调查的内部结构的彩虹超镁铁质岩，这是位于大西洋中脊的非转换不连续。地震成像显示，构成彩虹地块的超镁铁质岩已被大量岩浆岩床侵入，分布在整个地块的深度约2-10公里处。这些岩床，这似乎是在不同阶段的结晶，可以提供所需的热量，以驱动高温热液循环，从而提供了一个解释，在这个超镁铁质设置中观察到的热液放电。我们的研究结果表明，高温热液系统可以驱动的热量来自深源岩浆，即使在折返超镁铁岩岩石圈非常低的岩浆供应。
Hydrothermal circulation at mid-ocean ridge volcanic segments extracts heat from crustal magma bodies. However, the heat source driving hydrothermal circulation in ultramafic outcrops, where mantle rocks are exhumed in low-magma-supply environments, has remained enigmatic. Here we use a three-dimensional P-wave velocity model derived from active-source wide-angle refraction-reflection ocean bottom seismometer data and pre-stack depth-migrated images derived from multichannel seismic reflection data to investigate the internal structure of the Rainbow ultramafic massif, which is located in a non-transform discontinuity of the Mid-Atlantic Ridge. Seismic imaging reveals that the ultramafic rocks composing the Rainbow massif have been intruded by a large number of magmatic sills, distributed throughout the massif at depths of similar to 2-10 km. These sills, which appear to be at varying stages of crystallization, can supply the heat needed to drive high-temperature hydrothermal circulation, and thus provide an explanation for the hydrothermal discharge observed in this ultramafic setting. Our results demonstrate that high-temperature hydrothermal systems can be driven by heat from deep-sourced magma even in exhumed ultramafic lithosphere with very low magma supply.