为了拓宽大家对这些基本地幔楔形过程的综合观点，课题组对小安的列斯弧下的地震衰减进行了成像，小安的列斯弧是一个缓慢俯冲旧的构造岩石圈的端元系统。高体积-剪切衰减比的间断异常(Qκ-1/Qμ-1大于0.6)和VP/VS (大于1.83)位于板块上方40公里处，代表滞留在冷边界层中的排出流体，将流体输送到弧后。最强的衰减(1000/QS 约为20)，是热地幔熔融的特征，位于弧后下方，揭示了弧后地幔是如何为弧火山提供能量的。熔池位于上板块下方，沿着早期弧后扩张的构造向弧渗透，研究结果显示，板块脱水、上板块性质、过去的构造以及由此产生的熔池路径共同影响了火山活动。
据悉，从俯冲板块中喷出的挥发物促进了上覆热地幔的熔化，为弧火山活动提供了养分。然而，关于控制熔体产生和传输的因素，以及这些因素如何决定火山的位置的争论仍在继续。
附：英文原文
Title: Slab to back-arc to arc: Fluid and melt pathways through the mantle wedge beneath the Lesser Antilles
Author: Stephen P. Hicks, Lidong Bie, Catherine A. Rychert, Nicholas Harmon, Saskia Goes, Andreas Rietbrock, Songqiao Shawn Wei, Jenny S. Collier, Timothy J. Henstock, Lloyd Lynch, Julie Prytulak, Colin G. Macpherson, David Schlaphorst, Jamie J. Wilkinson, Jonathan D. Blundy, George F. Cooper, Richard G. Davy, John-Michael Kendall, VoiLA Working Group
Issue&Volume: 2023-02-01
Abstract: Volatiles expelled from subducted plates promote melting of the overlying warm mantle, feeding arc volcanism. However, debates continue over the factors controlling melt generation and transport, and how these determine the placement of volcanoes. To broaden our synoptic view of these fundamental mantle wedge processes, we image seismic attenuation beneath the Lesser Antilles arc, an end-member system that slowly subducts old, tectonized lithosphere. Punctuated anomalies with high ratios of bulk-to-shear attenuation (Qκ-1/Qμ-1 > 0.6) and VP/VS (>1.83) lie 40 km above the slab, representing expelled fluids that are retained in a cold boundary layer, transporting fluids toward the back-arc. The strongest attenuation (1000/QS ~ 20), characterizing melt in warm mantle, lies beneath the back-arc, revealing how back-arc mantle feeds arc volcanoes. Melt ponds under the upper plate and percolates toward the arc along structures from earlier back-arc spreading, demonstrating how slab dehydration, upper-plate properties, past tectonics, and resulting melt pathways collectively condition volcanism.
DOI: add2143
Source: https://www.science.org/doi/10.1126/sciadv.add2143