Water in mantle eclogite: Origin, distribution and physical consequences

地幔榴辉岩中的水：起源、分布和物理后果

• 批准号: 432249855
• 负责人: Dr. Sonja Aulbach
• 金额: --
• 依托单位: Abteilung Petrologie und Geochemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/432249855?language=en
• 关键词: Water; mantle; eclogite; Origin; distribution

The composition, structure and thermal state of the largely inaccessible deep lithosphere are inter-rogated by geophysical means with increasing detail, and its dynamics revealed by increasingly sophisticated numerical modelling. The accuracy of both approaches is enhanced by input from xenoliths entrained in deep-seated magmas. However, the physical properties of eclogites, as a subordinate but non-negligible part of dominantly peridotitic cratonic lithosphere, have not been systematically investigated. Like their peridotitic counterparts, some of these rocks have been metasomatised and possibly cryptically hydrated. As rocks consisting of ~50% clinopyroxene, mantle eclogites are expected to significantly contribute to the lithospheric water budget, but there are few studies on their H2O contents, and the nature and timing of their enrichment, and effects on geophysical observables are virtually unknown. The main aims of this study are thus: (1) To determine the H2O content in - and distribution between - clinopyroxene, garnet ± rutile in eight exceptionally well-characterised mantle eclogite suites from various cratons and tectonic settings by Fourier-Transformed Infrared Spectroscopy. Combined with published com¬po¬sitions for peridotite, this will allow the bulk densities, seismic velocities and electrical conductivities of regional eclogite-bearing continental lithospheres to be constrained with unprecedented detail and accuracy; (2) To determine the timing of the major hydration event represented by phlogopite-bearing eclogite, possibly linked to H2O introduction into nominally anhydrous minerals, by Ar-Ar dating of phlogopite; (3) evaluate implications for the rheology and stability of cratonic lithosphere.

在很大程度上无法访问的深层岩石圈的组成，结构和热状态通过地球物理手段与越来越多的细节相互融合，并且其动力学通过日益复杂的数值建模所揭示。通过包裹在深座岩浆中的异种石的输入，两种方法的准确性都提高了。然而，尚未系统地研究Elogites的物理特性，是主要研究的植物性cratonic Cratonic岩石圈的下属但不可忽略的部分。像橄榄岩的对应物一样，其中一些岩石已被化合作，并且可能在密码量中进行了密码。由于岩石由约50％的斜二烯组成，预计地幔elog岩将显着有助于岩石圈水预算，但对其H2O含量的研究很少，其富集的性质和时机以及对地球物理观察者的影响实际上是未知的。因此，这项研究的主要目的是：（1）确定 - 在八个特征良好的特征良好的地幔eclogite套件中，在 - 斜氧烯，石榴石±金红石之间的H2O含量和分布之间，并通过傅立叶转换红外光谱光谱概况。结合出版的橄榄岩的综合性，这将允许区域含有依云母的连续岩石圈的大量密度，地震速度和电导率受到前所未有的细节和准确性的限制； （2）确定由含有磷酸磷酸石的叶绿树代表的主要水合事件的时机，可能与富洛格属的Ar-ar ar-ar ar-ar ar-ar tate可能与H2O引入了名义上无水矿物的介绍； （3）评估对板岩岩石圈流变学和稳定性的影响。