EFFECT OF DECOMPOSITION OF HYDROUS MINERALS ON MECHANICAL-PROPERTIES OF ROCKS AT HIGH-PRESSURES AND TEMPERATURES
EFFECT OF DECOMPOSITION OF HYDROUS MINERALS ON MECHANICAL-PROPERTIES OF ROCKS AT HIGH-PRESSURES AND TEMPERATURES
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DOI：
10.1016/0040-1951(76)90120-7
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发表时间：
1976-01-01
期刊：
影响因子：
2.9
通讯作者：
ISMAIL, IAH
中科院分区：
文献类型：
--
作者：
MURRELL, SAF;ISMAIL, IAH
石膏、部分蛇纹石化橄榄岩、蛇纹岩和绿泥石的样品在高达0.662 Gpa的压力和高达780℃的温度下，以∼10−5/S的固定应变速率变形。在密封样品中，含水矿物的开始分解伴随着强度的丧失、滑动摩擦的减少和岩石的脆化。观察到了膨胀硬化效应。被排放到大气中的标本仍然很坚固。在石膏中，在∼50℃和∼150℃之间，强度下降了10倍。部分蛇纹岩(∼40%镁橄榄岩，∼60%闪长岩)含有∼1%的水镁石，在∼300℃时，强度下降了50%，然后在∼300℃和∼700℃之间，强度又下降了10倍。蛇纹岩(∼90%利蛇纹石和温石棉)在∼400℃和600℃之间，强度下降了10倍。绿云母(∼85%波纹橄榄岩)在300℃时强度下降了约一半；在300°C到600°C之间，强度基本保持不变，在600°C到700°C之间，强度又下降了五倍。已通过差热分析、X射线衍射和光学显微镜研究了含水矿物中的相变，并将在其他地方进行更全面的描述。文中详细讨论了变形特征和变形机理，重点讨论了孔压和剪胀的作用。每种岩石都有一个温度范围，在这个温度范围内，密封样品的变形最稳定，因为不会发生伴随应力下降的脆性断层作用。在较高的温度下，岩石变得不稳定，非常脆弱。在与5K Km−1和100K Km−1之间的地温梯度相对应的条件下，这些岩石在浅层将变得脆而弱，在低于一定深度时将再次变脆和弱，这取决于岩石。讨论了与断裂和地震、同构造变质作用和阿尔卑斯型橄榄岩侵位有关的可能意义。
Extensive experiments have been carried out in which specimens of gypsum, a partially serpentinized peridotite, a serpentinite and a chloritite have been subjected to pressures up to 0.662 GPa together with temperatures up to 780°C and have been deformed at a fixed strain rate of ∼10−5/s. The commencement of decomposition of the hydrous minerals is accompanied in sealed specimens by loss of strength, a reduction in sliding friction, and embrittlement of the rocks. Dilatancy-hardening effects are observed. Specimens which are drained to the atmosphere remain strong. In gypsum there is a ten-fold reduction in strength between temperatures of ∼50°C and ∼150°C. The partially serpentinized peridotite (∼40% forsterite, ∼60% antigorite) which contains ∼1% of brucite shows a reduction in strength ∼50% at ∼300°C, followed by a further ten-fold reduction between ∼300°C and ∼700°C. The serpentinite (∼90% lizardite and chrysotile) shows a ten-fold reduction in strength between ∼400°C and 600°C. The chloritite (∼85% ripidolite) shows a reduction of strength by about a half at 300°C; the strength remains approximately constant between 300°C and 600°C, and there is a further five-fold reduction in strength between 600°C and 700°C. The phase changes in the hydrous minerals have been studied by means of differential thermal analysis, X-ray diffraction and optical microscopy, and will be more fully described elsewhere. A detailed discussion is given of the deformation characteristics and mechanisms, with particular emphasis on the role of pore pressure and dilatancy. There is a range of temperature for each of these rocks in which the deformation of sealed samples is most stable, in the sense that brittle faulting accompanied by a stress-drop does not occur. At higher temperatures the rocks become unstable and very weak. Under conditions corresponding to geothermal gradients between 5 K km−1and 100 K km−1these rocks would be brittle and weak at shallow depths, and would again become brittle and weak at depths below some level which depends on the rock. Possible implications are discussed in connection with faulting and earthquakes, with syntectonic metamorphism, and with the emplacement of Alpine-type peridotites.