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首页> 外文学位 >A determination of the viscosity of partially molten peridotite at melt fractions up to the RCMF and the effect of incompatible elements in olivines on the rates of cation diffusion.
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A determination of the viscosity of partially molten peridotite at melt fractions up to the RCMF and the effect of incompatible elements in olivines on the rates of cation diffusion.

机译：确定部分熔融橄榄石的熔融分数（直至RCMF）的粘度，以及橄榄石中不相容元素对阳离子扩散速率的影响。

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摘要

In this dissertation, I report on experiments to measure the viscosity of partially molten mantle rocks and experiments to measure the effect of mantle rock grain boundary chemistry on the diffusional transport of cations.; In chapter 2, I determine the influence of a large melt fraction, 0.15 ≤ &phis; ≤ 0.30, on the rheological behavior of partially molten rocks, after performing a series of creep experiments on synthetic peridotites in the diffusion and dislocation creep regimes. The creep data reveal a sharp drop in rock viscosity as &phis; is increased from &phis; = 0.25 to 0.30, indicative of a rheologically critical melt fraction (RCMF). Over the range 0 ≤ &phis; ≤ 0.25, the flow behavior of peridotite is well described by 3&d2; ∝ exp(alpha&phis;) with alpha = 21 for diffusion creep and alpha = 32 for dislocation-accommodated GBS creep.; In chapter 3, I extend the work in Chapter 2 to determine the relationship between alpha and melt composition. I (with Justin Hustoft) performed a series of creep experiments on samples of olivine + Fe-S and olivine + Au and combine the results with previously published measurements for olivine + MORB. Our results reveal an abrupt change in the value of alpha, from alpha = 21 for silicate melts to alpha = 6 for metallic melts. The low solubility of olivine in the metallic melts combined with stress enhancement at grain contacts may be responsible for change in alpha.; In chapter 4, I performed a series of interdiffusion experiments between pure and Ca or Sc-doped polycrystalline Mg2SiO4 and Co2SiO4. Doping the olivines with Ca, retards grain boundary diffusion, resulting in a lower value of D eff that is still enhanced a factor of ∼10 relative to lattice diffusion. Doping the olivines with Sc, has the effect of increasing both the lattice and grain boundary diffusivity, such that Deff is a factor of ∼3 greater than undoped samples. Therefore, relative to the host cation, a segregant with either higher valence state or larger ionic radius can significantly affect the mobility of the divalent cations, which will effect the mechanical and electrical properties of olivine in the earth.
机译：在本文中，我报告了测量部分熔融地幔岩石粘度的实验，以及测量地幔岩石晶界化学对阳离子扩散迁移的影响的实验。在第二章中，我确定了大熔体分数0.15≤＆phis;的影响。 ≤0.30，关于部分熔融岩石的流变行为，是在扩散和位错蠕变状态下对合成橄榄岩进行一系列蠕变实验后得出的。蠕变数据表明，岩石粘度急剧下降，为；从＆phis;增加= 0.25至0.30，表示流变学上关键的熔体分数（RCMF）。在0≤＆phis;的范围内≤0.25，橄榄石的流动行为由3＆d2很好地描述； ∝ exp（alphaφ），对于扩散蠕变，alpha = 21，对于位错适应的GBS蠕变，alpha = 32。在第3章中，我扩展了第2章中的工作，以确定Alpha和熔体成分之间的关​​系。我（与Justin Hustoft一起）对橄榄石+ Fe-S和橄榄石+ Au样品进行了一系列蠕变实验，并将结果与​​先前发布的橄榄石+ MORB的测量结果相结合。我们的结果揭示了α值的突然变化，从硅酸盐熔体的alpha = 21到金属熔体的alpha = 6。橄榄石在金属熔体中的低溶解度以及晶粒接触时的应力增强可能是造成α变化的原因。在第四章中，我进行了一系列纯和Ca或Sc掺杂的多晶Mg2SiO4和Co2SiO4之间的相互扩散实验。用Ca掺杂橄榄石可延缓晶界扩散，导致较低的D eff值，相对于晶格扩散，D eff仍提高了约10倍。用Sc掺杂橄榄石具有增加晶格和晶界扩散率的作用，因此Deff比未掺杂样品大约3倍。因此，相对于主体阳离子，具有较高价态或较大离子半径的分离剂会显着影响二价阳离子的迁移率，这将影响地球上橄榄石的机械和电气性能。

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  • 作者

    Scott, Theodor Joseph.;

  • 作者单位

    University of Minnesota.;

  • 授予单位 University of Minnesota.;
  • 学科 Geophysics.; Engineering Materials Science.; Geochemistry.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 96 p.
  • 总页数 96
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地球物理学;工程材料学;地质学;
  • 关键词

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