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

次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作用形成和改变的，最终影响了地球大陆和地幔的演化。该项目的目标是通过对岩石样本中一套完整的地球化学和微观结构数据的解释，评估在南极洲西部形成、改变和破坏次大陆地幔岩石圈的过程。新的数据将与现有的地震观测和玄武岩喷发的地球化学数据相结合。该项目将估计沿南极半岛、琼斯山、玛丽伯德地和罗斯岛的样带，次大陆地幔岩石圈的组成、结构、机械特性、温度和沉没潜力如何变化；代表不同构造和岩浆条件的区域。本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)地幔水化程度的时空变化及其对相关微观结构的影响，3)次大陆地幔岩石圈交代介质的时间和来源，4)地幔捕虏体数据与已有的玄武岩喷发地震观测和地球化学的联系。5)次大陆地幔岩石圈的有效黏度以及变形是否发生在水和融水的引入之前或受其影响；6)次大陆地幔岩石圈对整个西南极洲喷发玄武岩组成的贡献。该项目将解决的一个关键问题是，正常的俯冲作用、板块窗和大陆裂陷是如何在推断的密度和粘度结构中产生差异的；以及这种差异如何影响次大陆地幔岩石圈的稳定性，以及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和/或在西南极洲下方沉没。该奖项反映了美国国家科学基金会的法定使命，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。

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.