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.

该团队计划评估创建，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特性的变化如何影响其稳定性。这项建议的重点是南巴塔哥尼亚，那里的大陆根已经被过去5000万年爆发的熔岩采样。最近的地震学数据也显示了大陆根迁移的明确证据。这项研究加上新的地震观测将提供必要的信息，以评估南巴塔哥尼亚大陆根的演变和稳定性，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关于西南极洲大陆根的类似研究提供信息。这些项目结合起来，对巴塔哥尼亚和南极洲西部的稳定产生了全球影响，这两个地区曾经是一个大陆。该研究团队将在国内和国际上开展合作，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职业研究人员和一名研究生和一名本科生。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。该提案旨在收集南巴塔哥尼亚地幔捕虏体的新地球化学和显微结构数据。捕虏体已被采样喷发熔岩在过去的5000万年，这段时间包括从正常俯冲的纳斯卡海洋板块的构造过渡到形成的板状窗口在智利海脊南美洲海沟碰撞。本研究的主要目的是确定P-T条件，水化程度，再施肥和变形的SCLM在此过渡期间。它将允许估计岩石圈地幔的有效粘度和稳定性，并评估变形是否发生在水/熔体引入之前或受到水/熔体引入的影响。 此外，拟议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南巴塔哥尼亚SCLM的地震特性（速度，各向异性）。由于新的地震学数据显示了岩石圈地幔去除的明确证据，地幔捕虏体的地球化学特征将有助于检验这一假设，即被去除的岩石圈地幔不仅有助于南巴塔哥尼亚火山活动的组成，而且在智利海岭系统。最后，该提案将与正在进行的南极洲西部岩石圈地幔研究相结合，该研究在德雷克通道开通之前与南巴塔哥尼亚形成了一个单一的大陆块。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。