The transition from normal subduction to slab window, unraveling its effect on the subcontinental lithospheric mantle of southern Patagonia

该团队计划评估创造、修改和摧毁地球大陆的过程。他们还将估计大陆根的组成和机械性能的变化如何影响其稳定性。这项建议主要集中在巴塔哥尼亚南部，那里的大陆根是由过去5000万年来喷发的熔岩采集的。最近的地震学数据也显示出大陆根部被清除的明显证据。这项研究与新的地震学观测将提供必要的信息，以评估南巴塔哥尼亚大陆根的演化和稳定性，以及它的移除可能如何影响附近地球内部的组成。这项工作的结果将为正在进行的对西南极大陆根的类似研究提供参考。这些项目加在一起，对曾经是一块大陆的巴塔哥尼亚和西南极的稳定具有全球影响。研究团队将在国内和国际上进行合作，该项目支持美国三家研究机构的五个分析设施。该提案支持布朗大学的一名早期研究人员、一名毕业生和一名本科生。拟议工作的目标是了解俯冲过程如何影响南巴塔哥尼亚次大陆岩石圈地幔(SCLM)的稳定性。这项提议旨在收集巴塔哥尼亚南部地区地幔捕捉体的新的地球化学和显微结构数据。在过去的5000万年里，这些捕虏体是由喷发的熔岩采集的；这一次包括了从纳斯卡大洋板块的正常俯冲到智利海脊-南美海沟碰撞期间板片窗口的形成的构造转变。这项研究的主要目的是确定在这一转变过程中SCLM的P-T条件、水化程度、参照和变形。它将能够估计岩石圈地幔的有效粘度和稳定性，并评估变形是在水/熔体引入之前发生还是受到水/熔体的影响。此外，拟议的新数据将与新的地震学观测相结合，以评估这些地质过程如何影响南巴塔哥尼亚地区的地震性质(速度、各向异性)。由于新的地震学数据显示了岩石圈地幔移动的明确证据，地幔包体的地球化学特征将有助于验证这样一种假设，即移动的岩石圈地幔不仅对巴塔哥尼亚南部的火山活动有贡献，而且对智利山脊系统的火山活动也有贡献。最后，这项建议将与正在进行的对南极洲西部岩石圈地幔的研究结合在一起，在德雷克通道开放之前，该地幔与巴塔哥尼亚南部形成了一个单一的大陆区块。这一裁决反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This team plans to evaluate the processes that create, modify and destroy the Earth’s continents. They will also estimate how changes in composition and mechanical properties of the continental roots affect its stability. This proposal focuses on Southern Patagonia, where the continental roots have been sampled by lavas erupted over the last 50 million years. Very recent seismological data also shows clear evidence of continental root removal. This research together with the new seismological observations will provide the necessary information to evaluate the evolution and stability of the Southern Patagonia continental root and how its removal might affect the composition of the nearby Earth’s interior. The results of this work will inform a similar ongoing study of the continental roots of West Antarctica. Combined, these projects have global implications for the stability of Patagonia and West Antarctica, which were once a single continent. The research team will collaborate nationally and internationally, and this project supports five analytical facilities in three US research institutions. The proposal supports an early-career researcher and a graduate and an undergraduate student at Brown University.The goal of the proposed work is to understand how subduction processes have affected the stability of the Southern Patagonia subcontinental lithospheric mantle (SCLM). This proposal aims to collect new geochemical and microstructural data on mantle xenoliths from across Southern Patagonia. The xenoliths have been sampled by erupted lavas over the last 50 million years; this time encompasses the tectonic transition from normal subduction of the Nazca oceanic plate to the formation of a slab window during the Chile Ridge-South America trench collision. The main objectives of this study are to determine the P-T conditions, extent of hydration, refertilization and deformation of the SCLM during this transition. It will allow estimation of the effective viscosity and stability of the lithospheric mantle and evaluation of whether the deformation occurred prior to or was affected by the introduction of water/melt. Furthermore, the proposed new data will be combined with new seismological observations to evaluate how these geologic processes affected the seismic properties (velocities, anisotropy) of the Southern Patagonia SCLM. Because the new seismological data show clear evidence of lithospheric mantle removal, the geochemical characterization of the mantle xenoliths will help test the hypothesis that the removed lithospheric mantle contributed to the composition of the volcanism not only in Southern Patagonia, but also in the Chile Ridge system. Finally, this proposal will be combined with an ongoing study of the lithospheric mantle of West Antarctica, which formed a single continental block with Southern Patagonia before the opening of the Drake passage.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.