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.

地球上构造板的最古老的部分是在连续的内部，通常远离板边界的内部。连续板的这些所谓的“ cratonic”部分比平均水平厚，并且在数十亿年保持稳定，以抵抗内部变形。克拉通通常被年轻的构造板材料包围，并通过递送和碰撞的过程加上。但是，有地质证据表明，在某些地点，大陆板的厚实内部板的厚实内部已经不稳定和去除（例如，中国克拉顿和美国西南部）。一个基本的问题是：为什么有些克拉通区能够变形/去除，而另一些则可以稳定数十亿年？更具体地说，需要什么条件才能削弱连续构造板的内部以使其不稳定？为了调查这个问题，该项目将以西南北美作为自然实验室，以探索岩浆通过连续盘子渗透的作用，这可能在破坏克拉通的稳定中发挥作用。该研究区域具有广泛的新生代火山历史，表明一段时间的岩浆浸润时期（是由从北美大陆底部取出的Farallon板块的俯冲海壳触发的），此前是北部北部美国室内的巨大破坏性，导致了板块的层次和供应范围的特色，并构成了材料的特色。这项研究的一个关键特征是将有关火山岩的化学性质与实验室实验相结合，以实验岩浆穿过岩石样品和多孔材料中岩浆流动的数值模型。所有这些方法对于对岩浆的可能如何（a）在连续的构造板中移动以及（b）在移动时修改板上的所有这些方法都是必要的。我们的目标是检验以下假设：岩浆浸润可能在连续板的cratonic内部衰弱和不稳定中起重要作用。该团队（两名女性和一名男性）代表科学家在各个职业阶段，并建立了我们西南部两个重要的少数派服务机构之间的联系。在板块构造的理论中，通常缺乏连续岩石圈地幔弱和去除的动态过程的时间尺度的约束。通过重新评估年龄与地球化学数据之间的关系，特别是同位素和痕量元素抽象，我们提出了对北美西南部火山主义与构造之间关系的重新解释。这里的工作将检验以下假设：在与弧相关的岩浆中，以及Ignimbrite Flare的前后，预处理北美西南部岩石圈的关键过程发生了不稳定的：即区域规模的水合和上质主义，与远处/浅色角度分子板块的凹陷时期相关的区域水平和上质主义。在该项目中，我们通过对火山岩地球化学数据的详细时空组成分析以及两种高压多层多岩石学实验的套件来检验这一假设。两项努力都将为旨在研究CLM/熔体相互作用和/或原位融化对CLM的上升熔体组成和流变学的影响的数值实验提供信息。地球化学分析将包括NAVDAT数据库的数据挖掘以及新的样本收集，特别重要的是可用数据集中的一个关键差距，由连续内部的Laramide火山岩（特别是在新墨西哥州南部）表示。多安维尔实验的两个套件将研究（1）痕量元素在熔体rock界面上的扩散并确定相关的扩散常数； （2）代理CLM在熔体岩石界面处产生原位熔化的作用。数值实验将使用来自地球化学和多轴化数据集的数据来构建流动流量模型，以解决融化岩石相互作用，以解决从1D到3D多孔流量模型的热和化学分离式条件，该奖项反映了NSF的法定任务，并通过使用基金会的Merit和Broadial和广泛的评估来表达了珍贵的支持。