The Fingerprint of Water in Mantle Melting

地幔融化过程中水的指纹

• 批准号: 0635805
• 负责人: Henry Dick
• 金额: $ 19.97万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0635805&HistoricalAwards=false
• 关键词: Fingerprint; Water; Mantle; Melting

Intellectual Merits. This project seeks to study the role of water and hydrous melt in melting of the Josephine Peridotite (SW Oregon). This body comprises lherzolite (5% clinopyroxene) and harzburgite (5% clinopyroxene) rocks interpreted to the residue of mantle melting: first at an ocean ridge under dry conditions that produced local websterite layering, and then in a wet hydrous melting environment that drove the residue to extreme depletions not seen in abyssal peridotite suites. This is expressed by a wide range in mineral composition spanning that for both abyssal peridotites from mid-ocean ridges, and for ophiolite peridotites believed formed in supra-subduction zone environments. A second stage of melting is attributed to introduction of water and/or hydrous melt from a down-going ocean lithosphere slab into the mantle wedge - lowering the mantle melting point and allowing it to proceed well beyond the Cpx-out phase boundary that limits melting beneath ocean ridges. Whereas ridge magmatism can be attributed to adiabatic upwelling and melting of nearly dry mantle, arc-related volcanism involves introduction of volatiles and hydrous melts into the mantle that induce hydrous (or 'flux') remelting. The relative contribution of the slab-derived and mantle wedge components in the production of arc-related magmas has been long debated. Most studies constrain magmatic processes by inverting isotopic and trace element compositions of arc-related lavas. This approach is hindered by the complexity of the melt generation process, that may involve as yet poorly understood interactions between migrating melts and the overlying mantle, as well as transport through and interaction with arc crust. The Josephine Peridotite offers the opportunity to directly study and constrain how water and hydrous melts are introduced into, interact with and are transported through the subarc mantle - and how this effects melt chemistry. A combined major and trace element whole rock and mineral study is proposed to document how the composition of the Josephine Peridotite massif was influenced by the introduction of volatiles and hydrous melt, and whether this is a local or pervasive influence.Broader Impacts: This project relates directly to the goal of understanding the role of volatiles in arc-related magmatism - a subject of broad interest and significant societal impact due to the explosive nature of arc volcanism. In addition, the project will support a Ph.D. student.

智力优点。该项目旨在研究水和含水熔体在约瑟芬橄榄岩融化（SW Oregon）中的作用。 该物体包括lherzolite（5％斜氧烯）和Harzburgite（5％Clinopyroxene）岩石解释为地幔融化的残留物：在干燥的条件下在海脊中产生当地的韦伯特矿石分层，然后在潮湿的水熔融化环境中，使残留物造成了极端消耗的残留物，无法看到Abyssal perysal perictiite pericite perictiite。这是由跨矿物组成的广泛范围表达的，这些矿物质跨越了近代山脊的两种深渊橄榄岩，以及在上象形区环境中形成的蛇绿岩橄榄石橄榄石。第二阶段的融化归因于从向下的海洋岩石圈板中引入水和/或液压熔体到地幔楔中 - 降低了地幔熔点，并允许其远远超出CPX外的相边界，从而限制了融化在海洋山脊下的融化。山脊岩浆可归因于绝热的上升流和近乎干燥的地幔的融化，而与弧相关的火山作用涉及将挥发性和含水融化到地幔中，从而诱导含水（或“玻璃”）。长期以来，人们一直在争论板衍生和地幔楔组件在与弧相关的岩浆生产中的相对贡献。大多数研究通过与弧相关熔岩的同位素和痕量元素组成来限制岩浆过程。这种方法受到熔融生成过程的复杂性的阻碍，这种过程可能涉及到迁移熔体与上覆的地幔之间以及通过弧形外壳的运输和相互作用之间的相互作用较低。约瑟芬橄榄岩提供了直接研究和限制如何将水和含水融化引入，与suberc suberc santle一起运输的机会，以及这如何影响化学融化。 提出了一项重大和微量元素的整体岩石和矿物研究，以记录约瑟芬橄榄岩块的组成如何受到挥发物和含水融化的引入以及这是当地的影响还是普遍影响的影响：该项目直接与理解挥发性杂志的作用有关，这是一种直接与Arc explative Insporive anc extive Insicive and Assive and Asciel and aborcielive and socie and siciet的影响：火山主义。此外，该项目将支持博士学位。学生。