ABR: Experimental Studies of Hydrous Mantle Melting

ABR：含水地幔熔化的实验研究

• 批准号: 1551321
• 负责人: Timothy Grove
• 金额: $ 43.9万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1551321&HistoricalAwards=false
• 关键词: ABR; Experimental; Studies; Hydrous; Mantle

This project focuses on understanding how the Earth?s mantle melts in subduction zones. H2O is a key ingredient in the formation of subduction zone magmas that erupt at arc volcanoes, volcanoes that form above subducted oceanic plates. This study will use experimental petrology to understand how magmas are formed when H2O is involved in the melting process. The experiments will consist of melting rock (the Earth?s mantle) in the presence of H2O at the temperatures and pressures equivalent to those experienced at depth below the volcanic chains. Very little is known about how H2O influences the temperature and chemical compositions produced by mantle melting. By understanding water?s influence on the temperature, melt composition and chemical reactions of this magma generation process, we will gain new fundamental knowledge of where and how the Earth?s continental crust has been generated through geologic time. This new knowledge will advance basic science by providing a quantitative framework for understanding the recycling of water through the Earth over the 4.5 billion years of our planet?s history.This Accomplishment Based Renewal requests support for a program of experimental petrology studies that will quantify the influence of water on melting processes in subduction zones. The experiments will systematically investigate (1) H2O-undersaturated mantle melting from 1.6 to 2.8 GPa and (2) H2O-undersaturated reaction of deeper mantle melts with shallower mantle wall rock at 1.2 GPa. Very little is known about hydrous melting in the pressure range of 1.6-2.8 GPa, so the experiments will provide new information on the process of hydrous melting in this pressure range. The proposed reaction experiments between deeper mantle melt and shallower mantle wall rock will be the first hydrous reaction experiments ever performed at pressures between 0.5 and 2 GPa. These experiments will allow a quantitative understanding of the effects of reaction within the mantle wedge, a process that is widely acknowledged but one that currently lacks experimental exploration. For both sets of experiments, the goal is to assess the influence of H2O on melt composition and to use the new data to develop quantitative models for mantle melting as well as models of melt-rock reaction in the sub-arc mantle. The magmatic processes that flux H2O through the mantle and crust in subduction zones are of fundamental importance for understanding the chemical evolution of the Earth over the last 4.5 billion years. The proposed work will provide a quantitative basis for understanding how H2O has influenced the chemical composition of the Earth?s mantle and crust. The experimental data will be used to develop models for predicting temperature, H2O content and pressure of melting for natural primitive lavas, which will be shared with the geosciences community. The results of the experimental study will also allow development of better geodynamic models of flow coupling between the asthenospheric mantle and the subducting slab, as well as providing constraints on the physical process of melt transport through the mantle wedge.

这个项目的重点是了解地球是如何？俯冲带地幔熔融。H2O是形成俯冲带岩浆的关键成分，这些岩浆在弧火山喷发，弧火山形成于俯冲的海洋板块之上。这项研究将使用实验岩石学来了解当H2O参与熔融过程时岩浆是如何形成的。实验将包括融化的岩石（地球？的地幔）在H2O的存在下的温度和压力相当于那些经历了在火山链以下的深度。关于H2O如何影响地幔熔融产生的温度和化学成分知之甚少。了解水？的温度，熔体成分和化学反应的影响，这岩浆生成过程中，我们将获得新的基本知识，在哪里和如何地球？中国大陆地壳是在地质时代形成的。这些新知识将通过提供一个定量框架来理解地球45亿年来水在地球上的循环，从而推动基础科学的发展。这一基于成就的更新请求支持一项实验岩石学研究计划，该计划将量化水对俯冲带熔融过程的影响。实验将系统地研究（1）1.6 ~ 2.8GPa的H_2O欠饱和地幔熔融和（2）1.2GPa下深部地幔熔体与浅部地幔围岩的H_2O欠饱和反应。在1.6- 2.8GPa压力范围内，人们对水合熔融过程知之甚少，因此实验将为这一压力范围内的水合熔融过程提供新的信息。深部地幔熔体和浅部地幔围岩之间的反应实验将是首次在0.5 - 2GPa压力下进行的水合反应实验。这些实验将允许定量了解地幔楔内反应的影响，这是一个被广泛承认的过程，但目前缺乏实验探索。对于这两组实验，目标是评估H2O对熔体成分的影响，并使用新的数据来开发定量模型地幔熔融以及在亚弧地幔的熔体-岩石反应模型。在俯冲带中，H2O通过地幔和地壳的岩浆过程对于理解过去45亿年来地球的化学演化具有根本的重要性。拟议的工作将提供一个定量的基础，了解如何H2O影响了地球的化学组成？的地幔和地壳。实验数据将用于开发预测天然原始熔岩的温度、H2O含量和熔化压力的模型，并将与地球科学界分享。实验研究的结果还将有助于开发更好的软流圈地幔和俯冲板块之间流动耦合的地球动力学模型，并对熔体通过地幔楔的物理过程提供限制。