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.榴辉岩-0003631榴辉岩是暴露在地球表面的致密正常岩石，通常由大约等量的石榴石和绿辉石，+/-少量的石英，蓝晶石，绿辉石和/或角闪石组成。榴辉岩形成于玄武岩成分的岩石的高压高温变质作用。这种转变可能有助于洋壳向更深的地方俯冲，可能影响中源地震的分布，并被认为会产生一个强大的层，可能会从岩石圈的其余部分分层。研究人员提出了一个详细的实验研究的流变学榴辉岩及其组成矿物。他们介绍了用其独特的5 GPa变形装置获得的初步结果，表明现在在技术上可以在这种研究所需的压力（2-4 GPa）下获得高质量的数据。这些初步结果表明，榴辉岩的强度可与位于大洋地壳正下方的方辉橄榄岩相媲美;之所以能达到这种平衡，是因为多晶硅酸盐石榴石的强度很高，但绿辉石的强度较弱。多晶硅酸盐石榴石的非凡强度支持了先前的建议，即地幔过渡带的下部（约500-700 km）可能是一个粘度增强的层。 为了更好地了解深俯冲过程，研究人员计划在其初步结果的基础上，对榴辉岩及其组成矿物在2-4 GPa压力下的流变学进行为期三年的扩大研究，以详细绘制其流动规律，变形机制和显微结构特征。他们将：（a）在3 GPa的温度和应变率的较大范围内详细阐述50-50榴辉岩的流变性，并在P = 2.0-4.0 GPa进行选定的实验;（B）对单矿物绿辉石和石榴石端元进行类似实验，以确定它们的流动参数;（c）对加入H2O的样品进行可比实验和等效分析;（d）如果时间允许，他们将在我们的多砧装置中合成多晶石榴石，并使用多晶石榴石和火成石榴石的短圆柱形样品在多晶稳定性范围内进行定性变形实验，一个在另一个的顶部，这将确定这两相的相对强度。