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Water contents in nominally anhydrous minerals in oceanic peridotite

大洋橄榄岩中名义无水矿物的含水量

基本信息

批准号：
5442230
负责人：
Professorin Dr. Esther Schmädicke
金额：
--
依托单位：
Lehrstuhl für Mineralogie
依托单位国家：
德国
项目类别：
Infrastructure Priority Programmes
财政年份：
2004
资助国家：
德国
起止时间：
2003-12-31 至 2011-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/5442230?language=en
关键词：
Water contents nominally anhydrous minerals

项目摘要

Olivine, ortho- and clinopyroxene are the main constituents of the Earth`s upper mantle. Although these minerals are nominally anhydrous, they can host traces of water, predominantly as OH defects, with concentrations of hundreds to thousands ppm H2O. These amounts of hydrous components have a disproportionately large effect on the physical and chemical properties of minerals and rocks. They enhance deformation, increase ionic diffusion and electrical conductivity in the asthenosphere and also may influence the melting behaviour. So far, predominantly xenoliths were used in order to measure the water contents in mantle minerals. No data are available für the suboceanic mantle. However, the knowledge of water contents is very important für implications on mantle rheology, convection and plate tectonics. The focus of this project, therefore, is to determine the water concentrations in oceanic peridotite. The unique samples taken at the Mid-Atlantik ridge (ODP legs 153 and 209) shall be investigated in this context. These peridotites are well suited for this purpose: (¡) They preserve relics of olivine and pyroxenes of sufficient size for measurements. (¡¡) They reveal different fabrics, from undeformed to strongly sheared, which is very fortunate in order to assess to weakening effect of water on mineral deformation.

橄榄石、正辉石和斜辉石是地球上地幔的主要成分。虽然这些矿物质名义上是无水的，但它们可以承载微量的水，主要是OH缺陷，浓度为数百到数千ppm的H2O。这些含水成分对矿物和岩石的物理和化学性质有着不成比例的巨大影响。它们增强了软流层的变形，增加了离子扩散和电导率，也可能影响融化行为。到目前为止，主要是用捕虏体来测量地幔矿物中的水分含量。没有关于海底地幔的资料。然而，对含水量的认识对于地幔流变学、对流和板块构造学具有重要意义。因此，这个项目的重点是确定海洋橄榄岩中的水浓度。在大西洋中脊（ODP腿153和209）采集的独特样本应在此背景下进行调查。这些橄榄岩非常适合这一目的：它们保存了足够大小的橄榄石和辉石遗迹，可供测量。（）它们揭示了不同的织物，从未变形到强烈剪切，这是非常幸运的，以评估水对矿物变形的减弱作用。