Collaborative Research: Investigating the Role of Mantle Metasomatism and Melt-Rock Interaction During Evolution of Continental Lithosphere Mantle

合作研究：研究大陆岩石圈地幔演化过程中地幔交代作用和熔岩相互作用的作用

• 批准号: 2052909
• 负责人: Mousumi Roy
• 金额: $ 22.55万
• 依托单位: University of New Mexico
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2052909&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Role; Mantle

The oldest parts of tectonic plates on Earth are found in the interiors of continents, usually far from plate boundaries. These so-called “cratonic” portions of continental plates are thicker than average and remain stable for billions of years, resisting internal deformation. Cratons are usually surrounded by younger tectonic plate material, added on through the processes of accretion and collision. However, there is geologic evidence that in some locations the thick cratonic interior portion of continental plates has been destabilized and removed (e.g., the North China Craton and the southwest U.S.). A fundamental question is: why are some cratonic regions able to be deformed/removed while others are stable for billions of years? More specifically, what conditions are needed to weaken and prime the interior of a continental tectonic plate for destabilization? To investigate this question, this project will use southwest North America as a natural laboratory to explore the role that magmas infiltrating through continental plates may play in destabilizing cratons. The study area has an extensive Cenozoic volcanic history that shows that a period of voluminous magma-infiltration (triggered by the removal of subducting oceanic crust of the Farallon plate from the base of the North American continent) preceded a dramatic destabilization of the interior part of southwest North America, leading to thinning of the plate and deformation characteristic of the present-day Basin and Range Province. A key feature of this study is to combine information on the chemistry of the volcanic rocks with laboratory experiments on magma moving through rock samples and numerical models of the flow of magma inside a porous material. All of these approaches are necessary to arrive at a process-oriented understanding of how magma might (a) move through continental tectonic plates and (b) modify the plate as it moves. Our goal is to test the hypothesis that magma-infiltration may play an important role in the weakening and destabilization of the cratonic interiors of continental plates. The team (two female and one male) represents scientists at various career stages and forges a connection between two important minority-serving institutions within the southwestern US. Within the theory of plate tectonics, constraints for the timescales of the dynamic process of continental lithospheric mantle weakening and removal are generally lacking. By reassessing the relationship between age and geochemical data, in particular isotopic and trace element abundances, we propose a reinterpretation for the relationship between volcanism and tectonism in southwest North America. The work here will test the hypothesis that the key processes that preconditioned the southwest North America lithosphere for destabilization took place after arc-related magmatism, and before and during the ignimbrite flare-up: namely, regional-scale hydration and metasomatism associated with the amagmatic period of flat/shallow angle subduction of the Farallon plate beneath SWNA. In this project, we test this hypothesis through detailed space-time-composition analyses of volcanic rock geochemical data and through two suites of high-pressure multianvil petrologic experiments. Both efforts will inform numerical experiments designed to investigate the effects of CLM/melt interaction and/or in situ melting on ascending melt compositions and rheology of the CLM. Geochemical analysis will consist of data mining of the NAVDAT database as well as new sample collection, of particular importance is a critical gap in the available data set is represented by Laramide volcanic rocks in the continental interior, specifically in southern New Mexico. The two suites of multianvil experiments will investigate (1) the diffusion of trace elements across the melt-rock interface and determine the relevant diffusion constants; and (2) the role of metasomatized CLM in generating in situ melting at the melt-rock interface. Numerical experiments will use the data combined from the geochemical and multianvil datasets to build fluidized flow models for melt-rock interactions that address both thermal and chemical disequilibrium conditions building from 1D to 3D porous flow 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.

地球上最古老的构造板块是在大陆内部发现的，通常远离板块边界。大陆板块的这些所谓的“克拉通”部分比平均厚度厚，并且在数十亿年的时间里保持稳定，抵抗内部变形。克拉通通常被年轻的构造板块物质所包围，这些物质是通过吸积和碰撞过程添加的。然而，有地质证据表明，在某些地方，大陆板块的厚克拉通内部部分已经不稳定和移除（例如，华北克拉通和美国西南部）。一个基本的问题是：为什么有些克拉通区域能够变形/移动，而其他克拉通区域却能稳定数十亿年？更具体地说，需要什么条件来削弱大陆构造板块内部的不稳定？为了研究这个问题，这个项目将把北美西南部作为一个自然实验室，探索岩浆渗透穿过大陆板块可能在破坏克拉通稳定中发挥的作用。研究区域具有广泛的新生代火山历史，表明大量岩浆渗透时期（由法拉龙板块从北美大陆底部俯冲海洋地壳的移除引发）先于北美西南部内部的剧烈不稳定，导致板块变薄和现今盆地和山脉省的变形特征。这项研究的一个关键特征是将火山岩的化学信息与岩浆在岩石样本中移动的实验室实验和岩浆在多孔材料内流动的数值模型结合起来。所有这些方法都是必要的，以便以过程为导向，理解岩浆如何(a)穿过大陆构造板块，(b)在移动过程中改变板块。我们的目标是验证岩浆渗透可能在大陆板块克拉通内部的削弱和不稳定中起重要作用的假设。这个团队（两女一男）代表了处于不同职业阶段的科学家，并在美国西南部两个重要的少数民族服务机构之间建立了联系。在板块构造理论中，通常缺乏对大陆岩石圈地幔弱化和移动动力学过程时间尺度的约束。通过重新评估年龄与地球化学数据之间的关系，特别是同位素和微量元素丰度之间的关系，我们提出了对北美西南部火山作用与构造作用关系的重新解释。这里的工作将验证一个假设，即为北美西南部岩石圈不稳定做好准备的关键过程发生在弧相关岩浆活动之后，以及在火成岩爆发之前和期间：即与西南西南地区法拉龙板块平/浅角度俯冲的岩浆期相关的区域尺度水化和交代作用。在本项目中，我们通过详细的火山岩地球化学数据的时空组成分析和两套高压多砧岩石学实验来验证这一假设。这两项努力将为数值实验提供信息，这些实验旨在研究CLM/熔体相互作用和/或原位熔化对CLM熔体成分和流变性的影响。地球化学分析将包括对NAVDAT数据库的数据挖掘以及新的样本收集，特别重要的是现有数据集中的一个关键缺口是大陆内部的Laramide火山岩，特别是在新墨西哥南部。两组多砧实验将研究(1)微量元素在熔融岩界面上的扩散，并确定相关的扩散常数；(2)交代CLM在熔体-岩石界面产生原位熔融中的作用。数值实验将使用来自地球化学和多铁块数据集的数据来建立熔体-岩石相互作用的流化流动模型，以解决从1D到3D多孔流动模型的热和化学不平衡条件。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。