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橄榄石是下地壳上地幔最丰富的造岩矿物,橄榄石集合体的高温高压流变性对地幔动力学过程有着很大的影响。以往对橄榄石单晶和集合体进行过的流变性实验研究,涉及了温度、压力、氧逸度、含铁量以及含水等因素的影响,本文研究了含水对富铁橄榄石集合体流变性能的影响,首先,利用高精度 Paterson 气体介质变形装置对含水富铁橄榄石集合体(Mg_(0.9),Fe_(0.1))_2SiO_4、(Mg_(0.7),Fe_(0.3))_2SiO_4和(Mg_(0.5),Fe_(0.5))_2SiO_4进行了高温三轴压缩蠕变试验,变形试验条件为:温度1323～1473K,围压300MPa,差应力10～300MPa,应变率10~(-7)～10~(-4)s~(-1),每个试件的最大变形量为20%。利用三维非线性拟合方法对蠕变试验数据进行分析,结果表明,含水富铁橄榄石集合体的微观变形机制为扩散域和位错域,对三种铁含量,扩散域的应力指数为1。位错蠕变域中,Fo_(50)应力指教为3.8,活化能为444kJ/mol;Fo_(70)应力指数为3.7,活化能为479kJ/mol,Fo_(90)应力指数为3.6,活化能为514kJ/mol。将实验结果与不含水富铁橄榄石集合体的强度进行对比,发现含水使富铁橄榄石的强度明显下降,舍铁量相同时,含水橄榄石集合体的流变强度比干燥时小至少一个数量级。从而得到了含水对含铁量不同的橄榄石集合体粘性(强度)影响的初步试验结果。
Olivine is the most abundant rock-forming mineral in the lower crust and upper mantle. The high temperature and high pressure rheological properties of the olivine aggregate have a great influence on the mantle kinetics. In the past, the rheological properties of olivine single crystals and aggregates were studied. The influences of temperature, pressure, oxygen fugacity, iron content and water content on the rheological properties of olivine single crystals and aggregates were studied. (Mg_ (0.9), Fe_ (0.1)) _2SiO_4, (Mg_ (0.7), Fe_ (0.3)) _2SiO_4 and (Mg_ (0.5), Fe_ (0.5)) _2SiO_4 under high temperature. The deformation test conditions are: temperature 1323 ~ 1473K, confining pressure 300MPa, differential stress 10 ~ 300MPa and strain rate 10 ~ (-7) ~ 10 ~ (-4) s ~ (-1), the maximum deformation of each specimen is 20%. The three-dimensional non-linear fitting method was used to analyze the creep test data. The results show that the micro-deformation mechanism of water-rich iron-rich olivine aggregates is diffusion domain and dislocation domain. The stress exponents of three kinds of iron content and diffusion domain are 1 . In the dislocation creep domain, the stress of Fo 50 stress is 3.8, the activation energy is 444 kJ / mol, the stress index of Fo 70 is 3.7, the activation energy is 479 kJ / mol, the stress index of Fo 90 is 3.6 and the activation energy Is 514 kJ / mol. Comparing the experimental results with those of non-water-rich iron-olivine aggregates, it is found that the strength of the iron-rich olivine decreases with water content. When the amount of iron is the same, the rheological strength of the water-containing olivine aggregate is at least one less than that of the dry Magnitude. The preliminary test results of the influence of water content on the viscosity (strength) of olivine aggregates with different iron contents were obtained.