Computational Geodynamics Laboratory, Centro de Geociencias, Universidad Nacional Autónoma de México, Juriquilla, C.P. 76230 Querétaro, Mexico.
Department of Earth Science, Rice University, 642 Cumbre Vista, Santa Fe, New Mexico 87501, USA.
Nat Commun. 2014 Oct 24;5:5095. doi: 10.1038/ncomms6095.
For some volcanic arcs, the geochemistry of volcanic rocks erupting above subducted oceanic fracture zones is consistent with higher than normal fluid inputs to arc magma sources. Here we use enrichment of boron (B/Zr) in volcanic arc lavas as a proxy to evaluate relative along-strike inputs of slab-derived fluids in the Aleutian, Andean, Cascades and Trans-Mexican arcs. Significant B/Zr spikes coincide with subduction of prominent fracture zones in the relatively cool Aleutian and Andean subduction zones where fracture zone subduction locally enhances fluid introduction beneath volcanic arcs. Geodynamic models of subduction have not previously considered how fracture zones may influence the melt and fluid distribution above slabs. Using high-resolution three-dimensional coupled petrological-thermomechanical numerical simulations of subduction, we show that enhanced production of slab-derived fluids and mantle wedge melts concentrate in areas where fracture zones are subducted, resulting in significant along-arc variability in magma source compositions and processes.
对于一些火山弧，喷发于俯冲海洋断裂带之上的火山岩的地球化学特征与弧岩浆源中较高的异常流体输入相一致。在这里，我们使用火山弧熔岩中硼（B/Zr）的富集作为评估阿拉斯加、安第斯、喀斯喀特和墨西哥湾转换断层弧沿走向相对板块衍生流体输入的指标。显著的 B/Zr 峰值与俯冲带中显著的断裂带相一致，在相对较冷的阿拉斯加和安第斯俯冲带中，断裂带的俯冲会局部增强流体在火山弧下的输入。俯冲的地球动力学模型以前没有考虑断裂带如何影响板块上方熔体和流体的分布。我们使用俯冲的高分辨率三维耦合岩石学-热力学数值模拟表明，增强的板块衍生流体和地幔楔熔体的产量集中在俯冲断裂带的区域，导致岩浆源成分和过程在弧上具有显著的变化。
