Skew of mantle upwelling beneath the East Pacific Rise governs segmentation

摘要

新海洋壳是随地幔上涌在中洋脊产生的，这个过程过去被假设在活跃 山脊下是对称的。但来自East Pacific Risee的新的地震成像数据表明， 事实不是这样：地幔上涌事实上是歪斜的。这也许是海洋扩散中心的 分割化的部分原因，并且也许还可解释为什么该山脊的一部分火山和 热液活跃、而另一部分却处于休眠状态。%Mantle upwelling is essential to the generation of new oceanic crust at mid-ocean ridges, and it is generally assumed that such upwelling is symmetric beneath active ridges. Here, however, we use seismic imaging to show that the isotropic and anisotropic structure of the mantle is rotated beneath the East Pacific Rise. The isotropic structure defines the pattern of magma delivery from the mantle to the crust. We find that the segmentation of the rise crest between transform faults correlates well with the distribution of mantle melt. The azimuth of seismic anisotropy constrains the direction of mantle flow, which is rotated nearly 10° anticlockwise from the plate-spreading direction. The mismatch between the locus of mantle melt delivery and the morphologic ridge axis results in systematic differences between areas of on-axis and off-axis melt supply. We conclude that the skew of asthenospheric upwelling and transport governs segmentation of the East Pacific Rise and variations in the intensity of ridge crest processes.