Imaging slab-transported fluids and their deep dehydration from seismic velocity tomography in the Lesser Antilles subduction zone
Imaging slab-transported fluids and their deep dehydration from seismic velocity tomography in the Lesser Antilles subduction zone
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DOI：
10.1016/j.epsl.2022.117535
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发表时间：
2022-04-15
影响因子：
5.3
通讯作者：
Maunder, Benjamin
中科院分区：
文献类型：
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作者：
Bie, Lidong;Hicks, Stephen;Maunder, Benjamin
挥发物在俯冲带的演化中起关键作用，但它们的途径仍然受到限制。研究较小的安列斯俯冲带可以产生新的限制，其中旧的海洋岩石圈由缓慢的俯冲慢慢形成。在这里，我们使用临时Voila记录的局部地震（在较小的安特列斯群岛中的挥发性回收）部署了海底地震仪在前后弧中的海底地震仪，以表征中北部中部较小的安特列斯（Antilles）俯冲区的3-D地震结构。沿着平板顶部的地震映射，我们发现低VP延伸到130-150公里的深度，比岩浆海洋壳的预期要深。平板最突出的，升高的VP/VS异常位于前后北岸瓜德罗普群岛和多米尼加的下方，那里有两个俯冲的断裂带，位于原始加利福尼亚和赤道大西洋大西洋岩石裂之间的倾斜俯冲边界。因此，这些结构在形成和发展时增强了海洋岩石圈的水合，并在俯冲时随后的地幔蛇纹石脱水。在平板上方，我们将小圈楔形物映像为高VP/VP和中等VP功能，表明平板脱水的流体通过上覆的冷边界层上升，可能会导致向西融化。我们的结果为空间可变的海洋板形成过程对平板脱水和地幔楔挥发性转移的影响提供了新的证据，最终会影响地表的火山过程，例如较小的安提莱斯群岛中中北岛上观察到的相对较高的岩浆输出。 （c）2022作者。由Elsevier B.V.出版
Volatiles play a pivotal role in subduction zone evolution, yet their pathways remain poorly constrained. Studying the Lesser Antilles subduction zone can yield new constraints, where old oceanic lithosphere formed by slow-spreading subducts slowly. Here we use local earthquakes recorded by the temporary VoiLA (Volatile recycling in the Lesser Antilles) deployment of ocean-bottom seismometers in the fore-and back-arc to characterize the 3-D seismic structure of the north-central Lesser Antilles subduction zone. Along the slab top, mapped based on seismicity, we find low Vp extending to 130-150 km depth, deeper than expected for magmatic oceanic crust. The slab's most prominent, elevated Vp/Vs anomalies are beneath the fore- and back-arc offshore Guadeloupe and Dominica, where two subducted fracture zones lie with the obliquely subducting boundary between Proto-Caribbean and Equatorial Atlantic lithosphere. These structures, therefore, enhance hydration of the oceanic lithosphere as it forms and evolves and the subsequent dehydration of mantle serpentinite when subducted. Above the slab, we image the asthenosphere wedge as a high Vp/Vs and moderate Vp feature, indicating slab-dehydrated fluids rising through the overlying cold boundary layer that might induce melting further to the west. Our results provide new evidence for the impact of spatially-variable oceanic plate formation processes on slab dehydration and mantle wedge volatile transfer that ultimately impact volcanic processes at the surface, such as the relatively high magmatic output observed on the north-central islands in the Lesser Antilles. (C) 2022 The Author(s). Published by Elsevier B.V.