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

从正常俯冲到板片窗口的转变，揭示了其对巴塔哥尼亚南部次大陆岩石圈地幔的影响

• 批准号: 2242269
• 负责人: Alberto Saal
• 金额: $ 33.54万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-07-01 至 2026-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2242269&HistoricalAwards=false
• 关键词: transition; normal; subduction; slab; window

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.

该团队计划评估创造、改变和破坏地球大陆的过程，他们还将估计大陆根的成分和机械特性的变化如何影响其稳定性。该提案重点关注对大陆根进行采样的南巴塔哥尼亚。最近的地震数据也显示了大陆根被移除的明确证据，这项研究与新的地震观测将为评估巴塔哥尼亚南部的演化和稳定性提供必要的信息。大陆根及其去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西南极洲大陆根的类似研究提供信息，这些项目对巴塔哥尼亚和西南极洲的稳定性具有全球影响。该研究团队将在国内和国际上进行合作，该项目支持布朗大学的三个研究机构的五个分析设施。的拟议的工作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。该提案旨在收集有关南巴塔哥尼亚地幔捕虏体的新地球化学和微观结构数据。这些捕虏体是通过喷发的熔岩进行采样的。过去5000万年；这段时间涵盖了从纳斯卡洋板块正常俯冲到智利时期板片窗口形成的构造转变本研究的主要目的是确定 SCLM 在此转变期间的 P-T 条件、水合程度、再肥化和变形，从而估计和评估岩石圈地幔的有效粘度和稳定性。此外，所提出的新数据将与新的地震观测相结合，以评估这些地质过程如何影响地震特性。南巴塔哥尼亚 SCLM 的（速度、各向异性）由于新的地震数据显示了岩石圈地幔去除的明确证据，因此地幔捕虏体的地球化学特征将有助于检验以下假设：去除的岩石圈地幔不仅有助于火山活动的成分。最后，该提案将与正在进行的对南极洲西部岩石圈地幔的研究相结合，形成一个单一的岩石圈地幔。该奖项反映了 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。