In fossil subduction zones associated with massive exhumation of (ultra)high-pressure ((U)HP) rocks such as the Western Alps, the geometry and behavior of subduction-channel and mantle-wedge rocks during exhumation are still poorly constrained by independent geophysical observations. Here we use a new local earthquake tomography model of the entire fossil subduction zone of the Western Alps based on data collected during the CIFALPS and CIFALPS2 passive seismic experiments, and the first receiver-function profile across the Ligurian Alps, to investigate the styles of subduction-channel and mantle-wedge exhumation as a function of increasing upper-plate divergence motion. In the northern Western Alps (low divergence), a thickened subduction channel can be detected, but no exhumed mantle wedge is found beneath the Gran Paradiso (U)HP dome. In the southern Western Alps (intermediate divergence), an exhumed mantle wedge is detected beneath the Dora-Maira (U)HP dome above a serpentinized subduction channel. In the Ligurian Alps (high divergence), an exhumed mantle wedge and a former subduction channel are detected at much shallower levels beneath the Voltri-Valosio (U)HP dome, and above a shallow-dipping lower-plate Moho. In this latter case, the lower boundary of the exhumed subduction channel is the most evident seismic-velocity interface, which may be easily misinterpreted as a true Moho. Similar Moho-like interfaces are found beneath the exhumed (U)HP domes of eastern Papua New Guinea and the Dabie Shan, which suggests that the results of the CIFALPS experiments may be used as a reference case for the interpretation of other (U)HP terranes worldwide.

中文翻译：

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地震断层扫描揭示了受上板发散运动控制的俯冲通道和地幔楔形挖掘的截然不同风格


在与西阿尔卑斯山等（超）高压 （（U）HP） 岩石大规模挖掘相关的化石俯冲带中，挖掘过程中俯冲通道和地幔楔形岩石的几何形状和行为仍然受到独立地球物理观测的不良约束。在这里，我们根据 CIFALPS 和 CIFALPS2 被动地震实验期间收集的数据，使用西阿尔卑斯山整个化石俯冲带的新局部地震层析成像模型，以及整个利古里亚阿尔卑斯山的第一个接收器功能剖面，来研究俯冲通道和地幔楔形挖掘的风格作为上板发散运动增加的函数。在西阿尔卑斯山北部（低发散度），可以检测到增厚的俯冲通道，但在 Gran Paradiso （U）HP 圆顶下没有发现挖掘出的地幔楔。在西阿尔卑斯山南部（中间发散），在蛇纹岩化俯冲通道上方的 Dora-Maira （U）HP 穹顶下方检测到一个挖掘出的地幔楔形。在利古里亚阿尔卑斯山（高发散度），在 Voltri-Valosio （U）HP 穹顶下方和浅倾下板 Moho 上方的较浅层检测到挖掘的地幔楔形和前俯冲通道。在后一种情况下，挖掘出的俯冲通道的下边界是最明显的地震速度界面，很容易被误解为真正的莫霍。在巴布亚新几内亚东部和大别山挖掘的 （U）HP 穹顶下发现了类似的类似 Moho 的界面，这表明 CIFALPS 实验的结果可以用作解释全球其他 （U）HP 地层的参考案例。