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

受地震学约束的南美洲俯冲与南大西洋地幔柱和大型火成岩省关系的地球动力学模型

• 批准号: 172558136
• 负责人: Privatdozent Dr. Bernhard Steinberger
• 金额: --
• 依托单位: Sektion 2.2: Geophysikalische Abbildung des Untergrunds
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/172558136?language=en
• 关键词: Geodynamic; models; relation; subduction; under

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?

南大西洋的海底扩张受到地幔柱的影响，地幔柱目前正在造成活跃的热点火山活动，并形成了海山小径、海隆脊和大火成岩省。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触发的，这些问题仍然没有解决。重建的喷发位置的大部分LIPs下降接近以上的大低剪切速度省（LLSVP）在最低地幔的边缘，但到目前为止，没有动力学模型存在，自相矛盾的解释LIPs的产生LLSVP边缘。为了研究这些悬而未决的问题有关的俯冲，羽和LLSVP的相互作用，我们计划在这里设计一个模型的板块重建和地幔动力学，大致匹配现今的层析成像。然后，我们将使用这个模型来解决以下问题：板块触发地幔柱以上的核幔边界，如果是这样的话，在哪里？地幔底部的LLSVPs能稳定数百万年吗？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LLSVP？我们能否设计一个模型，使羽流从LLSVP边缘而不是中心上升，如果是这样，模型参数是什么？板是必要的或有帮助的创建羽从边缘的LLSVP？在我们的模型中产生的羽流，它是否与实际的热点（和LIP）位置相对应，羽流/LIP的位置与白垩纪期间南大西洋开放的位置之间的关系是什么？