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SEGMENTATION OF MID-OCEAN RIDGES WITH AN AXIAL VALLEY INDUCED BY SMALL-SCALE MANTLE CONVECTION

机译:小尺度地幔对流诱发的带有轴谷的海中脊段

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THE small-scale segmentation of mid-ocean ridges with an axial rise has been modelled by considering each ridge segment as a giant crack in the lithosphere with a tip propagating along the ridge axis(1,2). For ridges with an axial valley, however, this type of model fails because the lithosphere is too thick to tear(3). Yet such ridges are clearly segmented, as defined by morphology, gravity and structure at the 50-100 km length scale. The-ridge offsets are large(4,5), and vary dramatically with time. This type of segmentation is commonly related to a three-dimensional, small-scale mantle flow occurring in the partially molten asthenosphere below the ridge(6-8). Here we propose a model for segmentation in such ridges, in which the convective flow below the ridge favours an asymmetrical breaking of the axial-valley lithosphere. This leads to the development and separation of ridge segments in a pattern that mimics the observed geometry and temporal evolution of the segmentation of most ridges,vith an axial valley, If our model is correct, it implies that coupling of oceanic lithosphere to small-scale convection controls the dynamics of mid-ocean ridges. [References: 31]
机译:通过将每个脊段视为岩石圈中的一个巨大裂缝,其尖端沿着脊轴传播(1,2),从而模拟了洋中脊具有轴向上升的小规模分割。但是,对于具有轴向谷的山脊而言,这种类型的模型会失败,因为岩石圈太厚而无法撕裂(3)。然而,根据形态,重力和结构,在50-100公里长的尺度上,这些山脊被清楚地分割了。脊偏移量很大(4,5),并且随时间变化很大。这种类型的分割通常与在山脊下方的部分熔融软流圈中发生的三维小规模地幔流有关(6-8)。在这里,我们提出了一种在这种脊中分割的模型,其中脊下方的对流有利于轴谷岩石圈的不对称破裂。这导致了脊段的发展和分离,该模式模仿了观察到的几何形状和大多数脊的分段的时间演变(通过轴向谷),如果我们的模型是正确的,则意味着海洋岩石圈与小尺度的耦合对流控制洋中脊的动力学。 [参考:31]

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