In plate tectonic theory a weak asthenosphere is required to facilitate the motions of the rigid plates. Partial melt could weaken the mantle, in turn impacting convection, but to date the existence of persistent melt has remained controversial. A wide range of scenarios has been reported in terms of the location, amount and pathways of melt. Here we use data collected by 39 ocean bottom seismometers deployed near the equatorial Mid-Atlantic Ridge on 0 to 80 Myr old seafloor. We calculate S-to-P (Sp) receiver functions and perform waveform modeling. We jointly interpret with shear-wave velocity tomography from surface waves and magnetotelluric (MT) imaging to take advantage of a range of resolutions and sensitivities and illuminate the structure of the oceanic lithosphere and the underlying asthenosphere. We image a tectonic plate thickness that increases with age in one location but undulates in another location. We infer thin and slightly thicker melt channels and punctuated regions of ascending partial melt several hundred kilometers off the ridge axis. This suggests melt persists over geologic timescales, although its character is dynamic, with implications for the lithosphere–asthenosphere boundary (LAB) and the driving forces of the plates. Ascending melt intermittently feeds melt channels at the base of the plate. The associated melt-enhanced buoyancy increases the influence of ridge-push in driving plate motions, whereas the channelized melt reduces the resistance of the plates to motion. Therefore, melt dynamics may play a larger role in controlling plate tectonics than previously thought.

在板块构造理论中，需要弱的软流圈层来促进刚性板块的运动。部分融化会削弱地幔，进而影响对流，但迄今为止，持久性融化的存在仍存在争议。关于熔体的位置，数量和途径，已经报道了各种各样的情况。在这里，我们使用39台海底地震仪收集的数据，这些仪器部署在0至80迈尔旧海底赤道中大西洋海脊附近。我们计算S-to-P（Sp）接收器功能并执行波形建模。我们结合表面波的剪切波速度层析成像技术和大地电磁（MT）成像技术，以利用各种分辨率和敏感度，并阐明海洋岩石圈和潜在软流圈的结构。我们对一个构造板块的厚度进行成像，该板块厚度在一个位置随年龄增长而增大，而在另一位置则呈波状。我们推断出较薄和稍厚的熔体通道以及距山脊轴线几百公里处的局部熔体上升的点状区域。这表明熔体在地质时标上仍然存在，尽管其特征是动态的，但对岩石圈-软流圈边界（LAB）和板块的驱动力有影响。熔体上升间歇地在板的底部进料熔体通道。相关的熔体增强浮力增加了推动板运动时脊推力的影响，而带通道的熔体降低了板运动的阻力。因此，熔体动力学可能在控制板块构造方面起着比以前认为的更大的作用。