The Fingerprint of Water in Mantle Melting

智力优势。该项目旨在研究水和含水熔体在约瑟芬橄榄岩（西南俄勒冈州）熔融中的作用。 该机构包括二辉橄榄岩（5%的单斜辉石）和harzburstenite（5%的单斜辉石）岩石解释地幔熔融的残留物：首先在洋脊干燥条件下，产生当地的镁橄榄石分层，然后在潮湿的含水熔融环境中，驾驶残留物的极端枯竭没有看到在深海橄榄岩套房。这表现在矿物成分范围很广，既包括大洋中脊的深海橄榄岩，也包括据信形成于俯冲带环境的蛇绿岩橄榄岩。熔融的第二阶段是由于引入水和/或含水熔体从下行的海洋岩石圈板进入地幔楔-降低地幔熔点，并允许它继续远远超出Cpx出相边界，限制熔融洋脊下。而脊岩浆活动可以归因于绝热上涌和熔融的近干燥的地幔，弧相关的火山活动涉及到引入挥发分和含水熔融到地幔，诱导含水（或“通量”）重熔。板片和地幔楔成分在弧相关岩浆产生中的相对贡献一直存在争议。大多数研究通过反演与弧有关的熔岩的同位素和微量元素组成来限制岩浆过程。这种方法受到熔体生成过程的复杂性的阻碍，这可能涉及到迁移熔体和上覆地幔之间的相互作用，以及通过弧壳的运输和相互作用。约瑟芬橄榄岩提供了直接研究和限制水和含水熔体如何被引入，相互作用和通过亚弧地幔运输的机会-以及这如何影响熔体化学。 建议进行主量元素和微量元素全岩和矿物研究，以记录挥发物和含水熔体的引入如何影响约瑟芬橄榄岩的成分，以及这是局部影响还是普遍影响。这个项目直接关系到了解挥发分在与弧有关的岩浆作用中的作用的目标-由于弧火山作用的爆炸性质，这是一个具有广泛兴趣和重大社会影响的主题。此外，该项目还将资助一名博士。学生.

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.