Continents are created and destroyed at convergent margins but understanding the interconnectedness of this system—a complex interplay of subaerial and tectonic erosion, volatile exchange and metamorphism, partial fusion and melt evolution—is far from complete. Here we use geochemical data from the Mexican convergent margin to reveal a strong connectivity between subducted materials and typical orogenic andesites. We find that the along-strike isotopic variations of andesitic stratovolcanoes in Mexico are mirrored by those of riverine sediments sampled along the continental margin, which presumably represent the compositions of tectonically ablated forearc crust entering the subduction zone. Isotopic modelling further indicates that the Mexican andesites represent partial melts of subduction mélanges, constituted by mixtures of altered subducted ocean crust, forearc debris and mantle peridotite in similar proportions. Remarkably, the concentrations and ratios of incompatible trace elements in the volcanoes also correlate with the major element compositions of their corresponding forearc sediments. This suggests that the modal contents of key mineral phases in the partially molten mélanges control the trace element abundances of the andesitic magmas. These findings demonstrate that a significant proportion of tectonically eroded subducted crust is not lost to the deep mantle, but effectively reincorporated into arc magmas in a closely interlaced continental rock cycle.

大陆在汇聚的边缘处被创建和破坏，但了解该系统的相互联系（包括复杂的地下和构造侵蚀，挥发性交换和变质作用，部分融合和融化演化）是远远不够的。在这里，我们使用来自墨西哥会聚边缘的地球化学数据来揭示俯冲物质与典型造山安山岩之间的强连通性。我们发现，墨西哥安第斯平流层火山的沿震同位素变化反映了沿大陆边缘采样的河流沉积物的变化，这大概代表了进入俯冲带的构造消融前臂地壳的成分。同位素建模进一步表明，墨西哥安山岩代表俯冲混杂岩的部分熔体，由俯冲的地壳，前陆碎片和地幔橄榄岩的变化比例相似的混合物组成。值得注意的是，火山中不相容的微量元素的浓度和比例也与其对应的前臂沉积物的主要元素组成相关。这表明部分熔融混杂岩中关键矿物相的模态含量控制了安山岩浆的微量元素丰度。这些发现表明，在构造上受到侵蚀的俯冲地壳并没有丢失到深层地幔中，而是在紧密交织的大陆岩石循环中有效地重新结合到了弧形岩浆中。火山中不相容的微量元素的浓度和比例也与其对应的前臂沉积物的主要元素组成相关。这表明部分熔融混杂岩中关键矿物相的模态含量控制了安山岩浆的微量元素丰度。这些发现表明，在构造上受到侵蚀的俯冲地壳并没有丢失到深层地幔中，而是在紧密交织的大陆岩石循环中有效地重新结合到了弧形岩浆中。火山中不相容的微量元素的浓度和比例也与其对应的前臂沉积物的主要元素组成相关。这表明部分熔融混杂岩中关键矿物相的模态含量控制了安山岩浆的微量元素丰度。这些发现表明，在构造上受到侵蚀的俯冲地壳并没有丢失到深层地幔中，而是在紧密交织的大陆岩石循环中有效地重新结合到了弧形岩浆中。