Experimental studies on rheological properties of transition zone minerals

过渡带矿物流变特性的实验研究

• 批准号: 1015336
• 负责人: Shun-ichiro Karato
• 金额: $ 34.94万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1015336&HistoricalAwards=false
• 关键词: Experimental; studies; rheological; properties; transition

The rheological properties of transition zone minerals have a strong influence on how mantle convection works. There is clear evidence, from seismic tomography, for intense deformation of deep sinking cold materials in the mantle transition zone. However, intense deformation of cold materials is at odds with the conventional view of temperature sensitivity of rheological properties. The main purpose of this project is to provide a new data set, based on newly developed high-pressure deformation techniques, by which we can solve this paradox. One hypothesis to resolve this paradox is that the phase transformations that occur in the transition zone will make materials weak by grain-size reduction. However, so far there is no quantitative data on the sensitivity of rheological properties of transition zone minerals on grain-size. In this project, the investigator will perform a series of laboratory experiments on wadsleyite (one of the transition zone minerals), using RDA (rotational Drickamer apparatus), to determine the flow laws for grain-size sensitive deformation mechanisms. Samples to be used are synthetic polycrystalline aggregates with controlled grain-size and water content. Specimens will be deformed at constant strain-rates using RDA, and the mechanical data (stress-strain curves) will be obtained in-situ at a synchrotron facility (NSLS at Brookhaven). Deformed samples will be examined ex-situ after the recovery to study the microstructures using a range of techniques including optical microscope, EPMA, SEM (EBSD), FTIR, Raman and TEM. The results will shed light on how mantle convection occurs in Earth and how Earth evolves thermally.

过渡区矿物质的流变特性对地幔对流的工作原理有很大影响。从地震层析成像中有明确的证据表明，地幔过渡区中深沉的冷材料的严重变形。然而，冷材料的严重变形与流变特性的温度灵敏度的常规视图不一致。该项目的主要目的是基于新开发的高压变形技术提供新的数据集，我们可以通过该技术解决此悖论。解决这一悖论的一种假设是，过渡区域中发生的相变会使材料通过晶粒大小的减少而弱。但是，到目前为止，尚无关于过渡区矿物在晶粒大小的流变特性敏感性的定量数据。在该项目中，研究人员将使用RDA（旋转式drickamer设备）对Wadsleyite（过渡区矿物之一）进行一系列实验室实验，以确定用于晶粒大小敏感变形机制的流量法。要使用的样品是具有控制晶粒和水含量的合成多晶骨料。样品将使用RDA在恒定应变率上变形，并将在同步器设备（Brookhaven的NSLS）处获得机械数据（应力 - 应变曲线）。恢复后将检查变形的样品，以使用一系列技术研究微观结构，包括光学显微镜，EPMA，SEM（EBSD），FTIR，RAMAN和TEM。结果将阐明地幔对流在地球中的发生以及地球如何热发展。