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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >High-temperature creep of synthetic calcite aggregates: influence of Mn-content
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High-temperature creep of synthetic calcite aggregates: influence of Mn-content

机译：合成方解石骨料的高温蠕变：锰含量的影响

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To investigate the role of impurities on the deformation of calcite rocks, we performed creep experiments on fine-grained synthetic calcite aggregates with varying Mn-content. The tests were performed in a uniaxial creep apparatus at temperatures of 700-830 degreesC and stresses between 15 and 65 MPa, resulting in strain rates of 10(-7) to 10(-4) s(-1). Varying the oxygen fugacity, f(O2), between 10(-18) and 10(-4) MPa did not affect the creep strength. Applying a power law constitutive relationship on the creep data, two distinct creep regimes were observed, a low stress regime (<15 MPa) and a high stress regime (>20-25 MPa). In the low stress regime, a stress exponent n of 1.7+/-0.3 and an activation energy of Q=300+/-45 kJ/mol were found. The mechanical data and microstructural observations suggest that grain-boundary sliding accommodated by grain-boundary diffusion is the dominant creep mechanism. At high stresses, we obtained a stress exponent of n=3.1+/-0.6 and an activation energy of Q=490+/-50 kJ/mol, indicating dislocation creep. Transmission-electron microscopy (TEM) observations show a dominance of recovery-related dislocation structures suggesting that dislocation climb is important. Increasing Mn-concentration from 10 to 670 ppm leads to an enhancement in creep rate in both creep regimes, but the effect is more substantial in the diffusion creep regime (one order of magnitude). In the diffusion creep regime, the enhancement of creep rate by Mn is attributed to the substitution of Ca by Mn, which may increase grain-boundary diffusivity of calcite. In the dislocation regime, it is interpreted as a combination of dislocation climb and glide with the exchange of Ca by aliovalent Mn, which may affect the point defect concentration. (C) 2004 Elsevier B.V. All rights reserved.
机译：为了研究杂质在方解石岩石变形中的作用，我们对锰含量不同的细粒方解石骨料进行了蠕变实验。测试是在700-830℃的温度和15至65 MPa的应力下的单轴蠕变设备中进行的，应变率为10（-7）到10（-4）s（-1）。氧逸度f（O2）在10（-18）和10（-4）MPa之间变化不会影响蠕变强度。在蠕变数据上应用幂律本构关系，观察到两种不同的蠕变状态，即低应力状态（<15 MPa）和高应力状态（> 20-25 MPa）。在低应力状态下，应力指数n为1.7 +/- 0.3，活化能为Q = 300 +/- 45 kJ / mol。力学数据和微观结构观察表明，晶界扩散所适应的晶界滑动是主要的蠕变机制。在高应力下，我们获得的应力指数为n = 3.1 +/- 0.6，活化能为Q = 490 +/- 50 kJ / mol，表明位错蠕变。透射电子显微镜（TEM）观察表明，与恢复相关的位错结构占主导地位，表明位错爬升很重要。 Mn浓度从10 ppm增加到670 ppm会导致两种蠕变状态下蠕变速率的提高，但是在扩散蠕变状态下（一个数量级），其影响更为明显。在扩散蠕变状态下，Mn引起的蠕变速率提高归因于Ca被Mn取代，这可能会增加方解石的晶界扩散率。在位错状态下，它被解释为位错爬升和滑移与钙离子被异价锰交换所导致的，这可能会影响点缺陷浓度。 （C）2004 Elsevier B.V.保留所有权利。

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