• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Structure and elasticity of a lower mantle oxide (magnesium,iron)oxygen and a new method of generating shear waves for gigahertz ultrasonic interferometry.
【24h】

Structure and elasticity of a lower mantle oxide (magnesium,iron)oxygen and a new method of generating shear waves for gigahertz ultrasonic interferometry.

机译：下地幔氧化物（镁，铁）氧的结构和弹性，以及用于千兆赫超声干涉测量的产生剪切波的新方法。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Knowledge of the elastic properties and crystal chemistry of dense oxide structures plays an important role in interpreting the composition and mineralogy of Earth and planetary interiors from seismological observation. Magnesiowüstite-(Mg x,Fe1−x)O, with the rocksalt structure is expected to coexist with silicate perovskite-(Mg y,Fe1−y)SiO 3 in Earth's lower mantle (660–2900 km depth) and is thus potentially the most abundant non-silicate oxide in Earth, although the exact composition (x and y) of the lower mantle is yet unknown. The effects of (Mg,Fe)2+ substitution and non-stoichiometry due to Fe3+ on the crystal structure, elastic constants ( cij), and adiabatic moduli (K0S , G0) of synthetic single-crystal (Mg,Fe)O are reported for the first time. In addition to periclase-MgO and wüstite-Fe 0.95O, nine different intermediate compositions were studied with varying ΣFe/(ΣFe+Mg) and ferric-iron contents (Fe3+/ΣFe) ranging from 1 to 12%. Compressional (P) and shear (S) elastic-wave velocities were measured at ambient pressure using GHz-ultrasonic interferometry with a new method of generating high-frequency shear waves. The new acoustic technique features a P-to-S conversion inside a single-crystal buffer rod, and produces the highest frequency shear waves (up to 2 GHz) ever made in the laboratory. Single-crystal structure refinements confirm that ferric iron (Fe3+) is partially accommodated into the rocksalt structure by occupancy of the normally vacant tetrahedral interstitial site. The c11 and c44 elastic constants soften from periclase to wüstite whereas the c12 elastic constant increases. The rate of change in the elastic constants with composition is greatest between MgO and (Mg,Fe)O with ∼25 mol% FeO, such that adding Fe into periclase has a greater effect on the elastic properties than adding Mg to wüstite. The elastic anisotropy of (Mg,Fe)O has rather unusual behavior, being essentially constant for the range 0–25 mol% FeO, but then decreases linearly with Fe-content such that wUstite is elastically isotropic. The elastic properties of (Mg,Fe)O having similar total-Fe, but varying Fe3+ contents are identical within uncertainty. The isothermal compressibility of samples with 27, 56, and 75 mol% FeO was determined by X-ray diffraction in a diamond anvil cell at pressures up to ∼9 GPa resulting in determination of the bulk modulus: K0T = 158.4(4), 155.8(9), and 151.3(6) GPa with ∂KT/∂P = 5.5(1), 5.5(1), and 5.6(2), respectively. The [100] P-wave velocity was measured in the sample with ∼50 mol% FeO up to 3.6 GPa resulting in ∂ c11/∂P = 7.6(4), being about 20% lower than that for MgO. Therefore, Fe has an overall softening effect on the elasticity of (Mg,Fe)O, at least up to 4 GPa. Finally, the first single-crystal ultrasonic measurements have been made at simultaneous high temperature and hydrostatic pressure in a diamond anvil cell. The [001] P-wave travel time was measured in San Carlos olivine (Mg0.9Fe0.1) 2SiO4 to temperatures of 250°C from a starting pressure of 2.5 GPa. Although the pressure could not be measured at temperature, this experiment illustrates that acoustic coupling between the diamond anvil and the sample can be maintained at high temperature in a liquid pressure medium, potentially motivating future ultrasonic measurem
机译：对致密氧化物结构的弹性和晶体化学的了解在从地震学观察解释地球和行星内部的组成和矿物学方面起着重要作用。 Magnesiowüstite-（Mg x ，Fe 1 − x ）O，带有岩石盐结构有望与钙钛矿硅酸盐共存-（Mg y ，Fe 1- y < / italic>）SiO 3 在地球下地幔（深度660-2900 km）中，因此可能是地球上最丰富的非硅酸盐氧化物，尽管其确切组成（ x 和 y ）还未知。 Fe 3 + 引起的（Mg，Fe） 2 + 取代和非化学计量对晶体结构，弹性常数（ c 合成的 ij 和绝热模量（ K 0S ， G 0 ）首次报道了单晶（Mg，Fe）O。除了周长石MgO和wstite-Fe 0.95 O外，还研究了9种不同的中间组成，这些中间组成具有不同的ΣFe/（ΣFe+ Mg）和三价铁含量（Fe 3 + /ΣFe），范围为1至12％。使用GHz超声干涉仪和产生高频剪切波的新方法，在环境压力下测量压缩（P）和剪切（S）弹性波速度。这项新的声学技术在单晶缓冲棒内部进行了P到S转换，并产生了实验室中有史以来最高频率的剪切波（高达2 GHz）。单晶结构的细化证实，通过占据正常空缺的四面体间隙位，三价铁（Fe 3 + ）被部分容纳在岩盐结构中。 c 11 和 c 44 弹性常数从周长变为软质，而 c 12 弹性常数增加。弹性常数随组成的变化率在MgO和含约25 mol％FeO的（Mg，Fe）O之间最大，因此，向钙镁石中添加Fe比向镁橄榄石中添加Mg对弹性性能的影响更大。 （Mg，Fe）O的弹性各向异性具有非常不寻常的行为，在0-25 mol％FeO范围内基本上是恒定的，但随Fe含量线性降低，从而使钨铁矿具有弹性各向同性。具有相同的总Fe，但变化的Fe 3 + 含量的（Mg，Fe）O的弹性性质在不确定性内是相同的。用X射线衍射在高达约9 GPa的压力下在金刚石砧室中通过X射线衍射测定具有27、56和75 mol％FeO的样品的等温压缩率，从而确定了体积模量： K 0T = 158.4（4），155.8（9）和151.3（6）GPa，且∂ K T /∂ P < / italic>分别为5.5（1），5.5（1）和5.6（2）。用〜50 mol％FeO高达3.6 GPa测量样品中的[100] P波速度，结果产生resulting c 11 /∂ P = 7.6（4），比MgO低约20％。因此，Fe对（Mg，Fe）O的弹性具有整体软化作用，至少达到4 GPa。最后，在金刚石砧座中同时在高温和静水压力下进行了首次单晶超声测量。 [001] P波传播时间是在San Carlos橄榄石（Mg 0.9 Fe 0.1 0.1） 2 SiO 4

著录项

  • 作者

    Jacobsen, Steven Dollard.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Geophysics.; Geology.; Mineralogy.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 119 p.
  • 总页数 119
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;地质学;矿物学;
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号