HIGH-TEMPERATURE CREEP OF OLIVINE SINGLE-CRYSTALS .1. MECHANICAL RESULTS FOR BUFFERED SAMPLES
HIGH-TEMPERATURE CREEP OF OLIVINE SINGLE-CRYSTALS .1. MECHANICAL RESULTS FOR BUFFERED SAMPLES
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DOI：
10.1029/90jb01723
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发表时间：
1991-02-10
期刊：
影响因子：
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通讯作者：
KOHLSTEDT, DL
中科院分区：
文献类型：
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作者：
BAI, Q;MACKWELL, SJ;KOHLSTEDT, DL
为了研究地球上地幔的流变行为，对圣卡洛斯橄榄石单晶进行了100多次高温变形实验，在总压为0.1 MPa的受控化学环境中进行了变形实验。建立了蠕变速率与外加应力、温度和氧逸度之间的幂函数关系本构方程。此外，还研究了斜方辉石活性和加载方向对蠕变行为的影响。对于[101]c，[011]c和[110]c三个压缩方向的样品，在斜方辉石或镁闪石缓冲下，需要两个或三个幂定律方程来描述在整个实验条件下在固定应力下的应变速率对温度和氧逸度的依赖关系。提出了不同的蠕变机制控制蠕变速率的结论。在所有实验条件下，蠕变激活能与应力水平无关，应力指数在3.5+/-0.1范围内为常数。各种蠕变机制的活化能在230~1000kJ/mol之间变化，氧逸度指数在-0.03~0.4之间。从基于所有蠕变机制的幂定律方程确定的本构方程出发，建立了橄榄石在1 Mpa应力下的epsilon-T-f(O)(2)形变图。
To investigate the rheological behavior of the Earth's upper mantle, over 100 high-temperature deformation experiments have been performed on single crystals of San Carlos olivine in controlled chemical environments at a total pressure of 0.1 MPa. Constitutive equations have been determined which describe the dependence of creep rate on applied stress, temperature and oxygen fugacity in terms of power law relations. In addition, the effects of orthopyroxene activity and loading orientation on the creep behavior have been investigated. For samples of each of three compression directions, [101]c, [011]c and [110]c, buffered by orthopyroxene or magnesiowustite, either two or three power law equations are required to describe the dependence of strain rate at fixed stress on temperature and oxygen fugacity over the full range of experimental conditions. It is proposed that in each power law regime a different creep mechanism controls the creep rate. For all of the experimental conditions, the activation energy for creep is independent of the stress level and the stress exponent is constant at 3.5 +/- 0.1. Activation energies for the various creep mechanisms varied from 230 to 1000 kJ/mol; and oxygen fugacity exponents lie in the range -0.03 to 0.4. From the constitutive equations determined based on the power law equations for all of the creep mechanisms, epsilon-T-f(o)(2) deformation maps were constructed at a stress of 1 MPa for olivine.