The Transition from Back Arc to Slab Window to Continental Rifting, Evidence from the Subcontinental Lithospheric Mantle of West Antarctica

从弧后到板窗再到大陆裂谷的转变，来自西南极洲次大陆岩石圈地幔的证据

• 批准号: 2139709
• 负责人: Alberto Saal
• 金额: $ 32.21万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-15 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2139709&HistoricalAwards=false
• 关键词: Transition; Back; Arc; Slab; Window

The subcontinental mantle lithosphere is created and modified at plate boundaries through a complex and variable mix of tectonic and magmatic processes that ultimately affect the evolution of the Earth's continents and mantle. The project goal is to evaluate the processes that create, modify, and destroy the subcontinental mantle lithosphere beneath Western Antarctica through the interpretation of a well-integrated set of geochemical and microstructural data from rock samples. The new data will be integrated with already existing seismological observations and geochemistry of erupted basalts. The project will estimate how the composition, structure, mechanical properties, temperature, and foundering potential of the subcontinental mantle lithosphere change along a transect through the Antarctic Peninsula, Jones Mountain, Marie Byrd Land and Ross Island; areas that represent different tectonic and magmatic conditions. This project assesses the geochemistry and microstructure on mantle xenoliths collected in West Antarctica to establish: 1) the xenolith pressure-temperature conditions of the tectono-magmatic events, 2) the variations in the degree of mantle hydration in time and space and its effect on the associated microstructure, 3) the time and source of the subcontinental mantle lithosphere metasomatic agents, 4) the link between mantle xenolith data and the already existing seismological observations and geochemistry of erupted basalts, 5) the effective viscosity of the subcontinental mantle lithosphere and whether the deformation occurred prior to or was affected by the introduction of water and melt, and 6) the contribution of the subcontinental mantle lithosphere into the composition of the erupted basalts across West Antarctica. A key question the project will address is how normal subduction, slab window and continental rifting have produced differences in the inferred density and viscosity structures; and how such difference affected the stability of the subcontinental mantle lithosphere and its potential for ablation by mantle wedge flow, aided by reductions in viscosity due to volatiles and melt, and/or foundering beneath West Antarctica.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.

大陆地幔岩石圈是在板块边界通过复杂多变的构造和岩浆过程的混合而产生和改变的，这些过程最终影响地球大陆和地幔的演化。该项目的目标是通过对岩石样品的一套完整的地球化学和微结构数据的解释，评估南极洲西部下的次大陆地幔岩石圈的形成、改变和破坏过程。新数据将与现有的地震观测和喷发玄武岩的地球化学相结合。该项目将估计如何组成，结构，机械性能，温度和下沉潜力的次大陆地幔岩石圈的变化沿着一个横断面通过南极半岛，琼斯山，玛丽伯德地和罗斯岛，代表不同的构造和岩浆条件的地区。该项目评估了在南极洲西部采集的地幔捕虏体的地球化学和微观结构，以确定：1）构造-岩浆事件的捕虏体压力-温度条件; 2）地幔水化程度的时空变化及其对相关显微构造的影响; 3）陆下地幔岩石圈交代剂的时间和来源; 4）地幔捕虏体数据与已存在的地震学观测和喷发玄武岩的地球化学之间的联系，5）次大陆地幔岩石圈的有效粘度以及变形是否发生在水和熔体的引入之前或受其影响，（6）西南极大陆地幔岩石圈对玄武岩成分的贡献。该项目将解决的一个关键问题是，正常俯冲、板片窗和大陆裂谷作用如何在推断的密度和粘度结构中产生差异;以及这种差异如何影响次大陆地幔岩石圈的稳定性及其被地幔楔流消融的可能性，以及由于挥发物和熔体导致的粘度降低，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。