Collaborative Research: Voyage to the bottom of Arcs: interplay between water, deformation, and lower crustal stability

合作研究：弧底航行：水、变形和下地壳稳定性之间的相互作用

基本信息

批准号：
1855407
负责人：
Emily Chin
金额：
$ 26.48万
依托单位：
University of California-San Diego Scripps Inst of Oceanography
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-07-01 至 2022-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1855407&HistoricalAwards=false
关键词：
Collaborative Research Voyage bottom Arcs

项目摘要

The formation of continents is intimately linked to plate tectonics on Earth. Subduction zones are tectonic boundaries where oceanic plates sink back into the Earth's deep interior. This process triggers melting in the deep Earth, the formation of volcanic island arcs, and the building of continental crust over time. Arc volcanos are well-studied due to their exposure at the Earth's surface. However, the roots of island arcs are difficult to access and therefore, remain poorly studied. Deep arc roots play a critical role in controlling the evolution of continental crust and the Earth system as a whole. Due to their high density, arc roots are hypothesized to regularly detach (delaminate) from the shallow and less dense parts of the arc, and sink back into the Earth, modifying the composition of the bulk continental crust over time. Importantly, the viscous nature of deep arc roots, and hence their likelihood of being detached, depends on their composition, particularly water. This study will provide new constraints on how material is delaminated, or removed, from volcanic arc roots. The team will combine state-of-the-art volatile analyses with rheological measurements on natural samples, which will be integrated into numerical models. The formation and evolution of continents, without which no life on land could have developed, is an active topic of interest for the broad scientific community.The processes by which the Earth's crust, and in particular the continental crust, has been constructed over time have been debated since the observation that bulk continental crust is andesitic in composition, but mantle-derived parental melts are mostly basaltic. A number of studies have suggested that delamination, a process by which dense mafic rocks at the base of arcs regularly sink back into the mantle, could account for the chemical gap between bulk continental crust and mantle melts. Other studies have proposed that delamination alone is not sufficient to explain the discrepancy. Currently, numerical simulations of this process have two major limitations: (1) viscosities used in current models are not linked to water measurements on natural arc cumulates because these in-situ analyses have never been performed; and (2) it is assumed that the material that detaches is initially isotropic although natural cumulate samples show a wide range of textures and internal deformation. This is a novel interdisciplinary project that is focused on the chemical and rheological role of water in lower crustal cumulates from four arc settings. The goal is to examine the interplay between water, deformation, and lower crustal stability in subduction zones, using a unique combination of geochemical, rheological, and numerical approaches. This collaborative project will support two Ph.D. students and the training of a postdoctoral investigator. In addition, the PIs will design a tectonics class tailored for K-12 students at the Perkins School for the Blind (MA). They will also offer undergraduate internship opportunities and make an active effort to recruit promising minority students.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.

大陆的形成与地球上的板块构造密切相关。俯冲带是构造边界，海洋板沉入地球深内部。这一过程触发了深层融化，火山岛弧的形成以及随着时间的推移建造大陆地壳。弧火山因其在地球表面的暴露而进行了充分研究。但是，岛屿弧的根部很难进入，因此对研究很少。深弧根在控制大陆地壳和整个地球系统的演变中起着至关重要的作用。由于它们的高密度，假设弧根从弧的浅且密度较少的部分脱离（分层），然后沉入地球，随着时间的推移改变了大陆壳的组成。重要的是，深弧根的粘性性质，因此它们被脱离的可能性取决于它们的组成，尤其是水。这项研究将对从火山弧根分层或去除材料的方式提供新的限制。该团队将将最新的挥发性分析与天然样本的流变学测量相结合，这些测量将集成到数值模型中。大陆的形成和演变，没有哪个土地上无法发展的生命，这是广泛科学界的一个积极主题。随着时间的流逝，地球壳，尤其是大陆壳的过程已经建立了，自从观察到散装大陆壳是构成中，但是地幔是厚底的，但大多数是地层面的属于地衣的奉献的父母的基础。许多研究表明，分层是该过程，即在该过程中，弧形底部的密集的镁铁质岩石经常沉入地幔中，可以解释散装大陆壳和地幔融化之间的化学间隙。其他研究提出，仅分层就不足以解释差异。当前，此过程的数值模拟具有两个主要局限性：（1）当前模型中使用的粘度与自然弧累积的水测量无关，因为这些原位分析从未进行过；（2）假定脱离的材料最初是各向同性的，尽管自然累积样品显示出广泛的纹理和内部变形。这是一个新颖的跨学科项目，侧重于从四个弧形环境中累积的水在下层地壳中的化学和流变作用。目的是使用地球化学，流变学和数值方法的独特组合来检查俯冲带中的水，变形和较低地壳稳定性之间的相互作用。该协作项目将支持两位博士学位。学生和博士后调查员的培训。此外，PIS还将设计一个针对珀金斯盲人学校（MA）的K-12学生量身定制的构造课程。他们还将提供本科实习机会，并积极努力招募有前途的少数民族学生。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的影响审查标准通过评估来支持的。