Experimental Investigation of the Rheology of Eclogite and Its Constituent Minerals at High Pressure

榴辉岩及其成分矿物高压流变性的实验研究

• 批准号: 0003631
• 负责人: Harry Green
• 金额: $ 36万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-01-15 至 2004-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0003631&HistoricalAwards=false
• 关键词: Experimental; Investigation; Rheology; Eclogite; Its

Green, Harry W.EAR-0003631 Eclogite is the densest normal rock exposed at the surface of Earth, typically consisting of approximately equal amounts of garnet and omphacite, +/- small amounts of quartz, kyanite, zoisite, and/or amphibole. Eclogite forms from high-pressure, high-temperature metamorphism of rocks of basaltic composition. This transformation may contribute to the subduction of oceanic crust to great depth, may affect the distribution of intermediate-focus earthquakes, and has been suggested to produce a strong layer that may delaminate from the rest of the lithosphere. The investigators propose a detailed experimental study of the rheology of eclogite and its constituent minerals. They presented preliminary results acquired with their unique, 5 GPa, deformation apparatus showing that it is now technically possible to acquire high-quality data at the pressures required for such studies (2-4 GPa). These preliminary results show that eclogite has a strength comparable to harzburgite, the rock type located immediately below the oceanic crust; this equality is achieved because the great strength of polycrystalline silicate garnet is compensated by the weakness of omphacite. The extraordinary strength of polycrystalline silicate garnet supports previous suggestions that the lower portion of the mantle transition zone (~500-700 km) may be a layer of enhanced viscosity. Toward a better understanding of deep subduction processes, the investigators plan to build on their preliminary results with a three-year expanded study of the rheology of eclogite and its constituent minerals at pressures of 2-4 GPa to map out in detail their flow laws, deformation mechanisms and microstructural characteristics. They will: (a) Elaborate the rheology of 50-50 eclogite over a larger domain of temperature and strain rate at 3 GPa and selected experiments at P = 2.0-4.0 GPa; (b) perform analogous experiments on the monomineralic omphacite and garnet end members to determine their flow parameters;(c) conduct comparable experiments and equivalent analysis of specimens with H2O added; and (d) if time permits, they will synthesize majoritic garnet in our multianvil apparatus and conduct qualitative deformation experiments within the majorite stability field using short cylindrical specimens of majoritic and pyropic garnets, one on top of the other, which will determine the relative strengths of these two phases.

绿色，Harry W.EAR-0003631 ECLOGITE是暴露在地球表面的最密集的正常岩石，通常由大约相等量的石榴石和绿一石组成，+/- +/-少量石英，kyanite，kyanite，Zoisite，Zoisite和/或Amphibole。来自玄武岩组成岩石的高压，高温变质的叶绿石形成。这种转变可能有助于将海洋壳的俯冲俯冲到深度，可能会影响中间位地震的分布，并已建议产生一个强大的层，该层可能与岩石圈的其余部分分层。研究人员提出了一项详细的实验研究，对叶绿石及其组成矿物的流变学。他们提出了其独特的5 GPA变形设备获得的初步结果，这表明现在有可能在此类研究所需的压力下获得高质量的数据（2-4 GPA）。这些初步的结果表明，叶绿石具有与位于海洋外壳下方的岩石类型相当的强度。之所以达到这种平等，是因为多晶硅酸盐石榴石的巨大强度是由绿岩的弱点所补偿的。多晶硅酸盐石榴石的特殊强度支持先前的建议，即地幔过渡区的下部（〜500-700 km）可能是增强的粘度。 为了更好地了解深层俯冲过程，研究人员计划以2-4 GPA的压力进行了为期三年的叶绿树及其组成矿物的研究，以详细介绍其流动法，变形机制和微观结构特征，以详细介绍了对叶虫及其组成矿物的三年研究。他们将：（a）在3 GPA的较大温度和应变率的较大域中详细说明50-50 eclogite的流变学，并在p = 2.0-4.0 GPA时进行选定的实验； （b）对单矿物的半矿物和石榴石端构件进行类似的实验，以确定其流参数；（c）对添加的H2O进行可比较的实验和标本的同等分析； （d）如果时间允许，它们将在我们的多静脉设备中合成主要石榴石，并使用短圆柱标本在多数岩和热带石榴石的短圆柱标本中进行定性变形实验，其中一个在另一个阶段，这将确定这两个阶段的相对强度。