Thermal and Compositional Structure of Antarctica from Probabilistic Joint Inversion of Seismic, Gravity, and Topography Data and Petrological Modelling

根据地震、重力、地形数据和岩石学模型的概率联合反演南极洲的热力和成分结构

• 批准号: 2203487
• 负责人: Walid Ben Mansour
• 金额: $ 19.16万
• 依托单位: Washington 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: 2022-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2203487&HistoricalAwards=false
• 关键词: Thermal; Compositional; Structure; Antarctica; Probabilistic; Thermal; Compositional; Structure; Antarctica; Probabilistic

Non-Technical abstractThe physical state of the mantle beneath the Antarctic Ice Sheet plays a key role in the interaction between the Antarctic ice cover and the solid earth, strongly influencing the glacial system's evolution. Generally, mantle temperature profiles are determined by analyzing rock samples from the mantle to determine pressure-temperature conditions, and/or by conversion of seismic velocity anomalies to temperature anomalies. However, mantle rocks have been found only in a very few places in Antarctica, and seismic anomalies reflect not only thermal anomalies but also compositional variations. In this project, the investigators will (1) use the most recent geophysical datasets sensitive to temperature and composition (high-resolution seismic velocity model, topography, satellite gravity), (2) Combine the sensitivity of these datasets in a to retrieve the most reliable model of thermal and compositional structure, (3) translate the results into 2-dimensional maps of temperature slices and the composition of iron in the mantle,(4) compare the results with results from other continents to better understand Antarctic geological history, and (5) use the new thermal model along with established rock relationships to estimate mantle viscosity. Technical abstract The thermochemical structure of the lithosphere beneath Antarctica is fundamental for understanding the geological evolution of the continent and its relationship to surrounding Gondwana continents. In addition, the thermal structure controls the solid earth response to glacial unloading, with important implications for ice sheet models and the future of the West Antarctic Ice Sheet. However, it is challenging to get an accurate picture of temperature and composition from only sparse petrological/geochemical analysis, and most previous attempts to solve this problem geophysically have relied on seismic or gravity data alone. Here, we propose to use a probabilistic joint inversion (high resolution regional seismic data, satellite gravity data, topography) and petrological modelling approach to determine the 3D thermochemical structure of the mantle. The inversion will be carried out using a Markov-chain Bayesian Monte Carlo methodology, providing quantitative estimates of uncertainties. Mapping the 3-dimensional thermochemical structure (thermal and composition) will provide a comprehensive view of the horizontal (50-100 km resolution) and vertical (from the surface down to 380 km) variations. This new model will give us the temperature variation from the surface down to 380 km and the degree of depletion of the lithospheric mantle and the sub-lithospheric mantle. This new model will also be compared to recent models of Gondwana terranes 200 Myrs to build a new model of the thermochemical evolution of the cratonic mantle. The new thermal and chemical structures can be used to better understand the geothermal heat flux beneath the ice sheet as well as improve glacial isostatic adjustment and ice sheet models.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.

非技术抽象的地幔的物理状态在南极冰盖下面在南极冰盖与固体土之间的相互作用中起着关键作用，从而强烈影响冰川系统的进化。通常，通过分析地幔中的岩石样品来确定压力温度条件和/或通过将地震速度异常转化为温度异常来确定地幔温度曲线。但是，仅在南极洲的极少数地方发现地幔岩石，地震异常不仅反映了热异常，还反映了组成变化。在该项目中，研究人员（1）将使用对温度和组成敏感的地球物理数据集（高分辨率地震速度模型，地形，地形，卫星重力），（2）将这些数据集的敏感性结合在A中，以检索最可靠的热结构和组成结构的模型，并将其转化为2 d-dimens opsiontion and Slaps and Slaps and Slaps MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAPS MMAP （4）将其与其他大陆的结果进行比较，以更好地了解南极地质历史，（5）使用新的热模型以及既定的岩石关系来估算地幔粘度。技术摘要南极下岩石圈的热化学结构对于理解大陆的地质演化及其与周围冈瓦纳大陆的关系至关重要。此外，热结构控制着对冰川卸载的固体响应，对冰盖模型和南极冰盖的未来具有重要意义。但是，仅从稀疏的岩石学/地球化学分析中准确地了解温度和成分是一项挑战，并且以前大多数试图在地球物理上解决此问题的尝试仅依赖于地震或重力数据。在这里，我们建议使用概率关节反转（高分辨率区域地震数据，卫星重力数据，地形）和岩石学建模方法来确定地幔的3D热化学结构。反转将使用马尔可夫链贝叶斯蒙特卡洛方法进行，从而提供不确定性的定量估计。映射3维热化学结构（热和成分）将提供水平（50-100 km分辨率）和垂直（从表面向下至380 km）的全面视图。这个新模型将使我们从表面降低到380 km的温度变化，以及岩石圈地幔和下层地幔的耗竭程度。该新模型也将与冈瓦纳Terranes 200 MYRS的最新模型进行比较，以构建一个新模型，以构建Cratonic地幔的热化学演化。新的热和化学结构可用于更好地了解冰盖下方的地热热通量，并改善冰川等静态调整和冰盖模型。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来获得支持的。