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.

次大陆地幔岩石圈是通过复杂多变的构​​造和岩浆过程在板块边界产生和改变的，最终影响地球大陆和地幔的演化。该项目的目标是通过解释来自岩石样本的一组完整的地球化学和微观结构数据来评估南极洲西部下方的次大陆地幔岩石圈的形成、修改和破坏过程。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。该项目将估计次大陆地幔岩石圈的成分、结构、力学性质、温度和沉没潜力如何沿着穿过南极半岛、琼斯山、玛丽伯德地和罗斯岛的横断面变化；代表不同构造和岩浆条件的区域。该项目评估了在南极洲西部收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）地幔水化程度随时间和空间的变化及其对地幔水化程度的影响。相关的微观结构，3）次大陆地幔岩石圈交代剂的时间和来源，4）地幔捕虏体数据与现有地震学之间的联系喷发玄武岩的观测和地球化学，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引入之前或受其影响，以及 6) 次大陆地幔岩石圈对地幔组成的贡献整个南极洲西部的玄武岩喷发。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烧蚀的可能性，以及由于挥发物和熔化导致的粘度降低和/或在西南极洲下方沉没的帮助。该奖项反映了 NSF 的法定使命，并已通过使用基金会的智力优点和更广泛的影响审查标准进行评估，认为值得支持。