Geodynamic models of the relation of subduction under South America and plumes and Large Igneous Provinces in the South Atlantic, with constraints by seismology

南大西洋的海底扩张受到地幔柱的影响，地幔柱目前正在引起活跃的热点火山活动，并创造了海山小径、地震脊和大火成岩省（LIPs）。然而，是什么决定了热点羽流的位置，以及它们在多大程度上是由俯冲板块引发的，这些问题仍未得到解决。重建的大低剪切速度省（Large Low Shear Velocity province， LLSVP）的喷发位置大多位于最下端地幔的大低剪切速度省（Large Low Shear Velocity province， LLSVP）边缘以上，但迄今为止还没有一个动态模型能够自我一致地解释大低剪切速度省边缘上lip的产生。为了研究这些与俯冲、羽流和llsvp相互作用有关的未解决的问题，我们计划在这里设计一个与现代断层摄影近似匹配的板块重建和地幔动力学模型。然后，我们将使用这个模型来解决以下问题：板块是否触发了核心幔幔边界上方的羽流，如果是，在哪里？地幔最底层的llsvp能在几百年里保持稳定吗？负化学浮力在多大程度上是必要的或有助于实现长期稳定性？俯冲板块在多大程度上稳定或破坏了llsvp ？我们能否设计出一种羽流从LLSVP边缘而不是中心上升的模型，如果可以，需要什么样的建模参数？板块对于从llsvp边缘形成羽流是必要的还是有帮助的？在我们的模型中，羽流在哪里产生，它是否与实际的热点（和LIP）位置相对应，羽流/LIP的位置与白垩纪南大西洋开放的位置之间有什么关系？

Seafloor spreading in the South Atlantic is influenced by mantle plumes that are presently causing active hotspot volcanism and have created seamount trails, aseismic ridges and LargeIgneous Provinces (LIPs). Yet what determines the locations of hotspot plumes, and to what extent they are triggered by subducted slabs remains unsolved. Reconstructed eruption locations of most LIPs fall close to above the margins of the Large Low Shear Velocity Provinces (LLSVPs) in the lowermost mantle, yet to date no dynamic model exists that selfconsistently explains the generation of LIPs on LLSVP margins. In order to study these unresolved issues related to the interaction of subduction, plumes and LLSVPs, we plan to devise here a model of plate reconstructions and mantle dynamics that approximately matches presentday tomography. We will then use this model to address the following questions: Do slabs trigger plumes above the coremantle boundary, and if so, where? Can LLSVPs in the lowermost mantle be stable for hundreds of Myrs? To what extent is negative chemical bouyancy necessary or helpful to achieve longterm stability? To what extent do subducted slabs stabilize or destabilize LLSVPs? Can we devise a model in which plumes rise from LLSVP edges, rather than their centers, and if so, for what modeling parameters? Are slabs necessary or helpful to create plumes from the edges of LLSVPs? Where are plumes generated in our model, does it correspond with actual hotspot (and LIP) locations and what is the relation between the locations of plumes/LIPs and where the South Atlantic opened during the Cretaceous?