Spliting continental lithosphere during rifting in the South Atlantic with emphasis on the role of magmatism.

裂谷和破裂的最大问题之一是可用的力可能不足以分离正常的大陆岩石圈（力悖论）。现今大多数大陆边缘都与裂谷初期的大规模火山喷发有关。热浮力地幔的上升羽流可以解释羽流头部上方受限区域内岩石圈的热减弱，但不能解释可能从羽流延伸数千公里的裂谷轴上的裂谷和大陆分裂。这一建议遵循了一个工作假设，即除了地幔黏度的热还原外，岩石圈的分离还有另外两个重要的过程。(1)基岩事件可能传播到大陆岩石圈，从而使岩浆在远低于断裂的拉张应力下容纳伸展；(2)裂谷尖端的应力集中可能使裂谷持续传播。我想研究是否需要大量与羽状柱相关的火成岩省和相关的巨大岩壁事件来解决力悖论，或者是否需要在裂谷尖端与被动上涌相关的应力集中和岩壁就足够了。南大西洋是这一争议的典型地区。在这里，我提出了一系列的数值二维和三维实验来研究这个问题。在边缘构造、沉降演化和岩浆历史方面的实验预测将与南大西洋的相同数据进行比较。反之亦然，南大西洋的情况将有助于进行实验。

One of the largest problems in rifting and breakup is that the available force might not be sufficient to part normal continental lithosphere (force paradox). Most present-day continental margins are associated with massive volcanic outflows during initial rifting. A rising plume of hot buoyant mantle would explain thermal weakening of the lithosphere in a confined area above the plume head but not rifting and continental breakup along a rift axis that might extend thousands of kilometers away from the plume. This proposal follows the working hypothesis that besides thermal reduction of mantle viscosity two further processes are important in parting the lithosphere. (1) Diking events might propagate into continental lithosphere allowing for magmatic accommodation of extension at much lower extensional stresses than faulting and (2) stress concentrations at the tip of a rift might allow for continuous propagation of the rift. I would like to study whether massive plume-related igneous provinces and associated huge diking events are required to solve the force paradox or if stress concentrations and diking associated with passive upwelling at a rift tip might suffice. The Southern Atlantic is a classic area for this controversy. Here, I propose a series of numerical 2D- and 3D-experiments to study this problem. Predictions of the experiments in terms of margin architecture, subsidence evolution and magmatic history will be compared with the same data from the South Atlantic. Vice versa, the situation in the South Atlantic will help to build the experiments.