橄榄石-尖晶石相转变流变学的实验研究

对(Mgx,Ni1-x)2GeO4系统中橄榄石-尖晶石两相混合物的流变性进行了实验研究.利用不同温压条件对混合物进行热压,得到的橄榄石和尖晶石的比例不同.温度为1 573K,试件的化学组成从x=0.95-0.70时,得到的两相材料从100%橄榄石到100%尖晶石.三轴压缩试件为圆柱状,直径8mm,两相混合物的平均颗粒尺寸为2.21-9.43μm.流变学试验在气体介质试验机中进行,围压为300MPa,温度为1 073-1 573K.试验分为常应力和常位移率两种,差应力σ1-σ3为45-320MPa,应变率在2.8×10-6-2.8×10-5s-1之间,将实验测得的混合物力学性质与两端材料的强度进行对比,发现两相多晶介质的强度介于两端材料的强度之间.当橄榄石到尖晶石的相变发生在变形过程中时,尖晶石比率的增加使得多晶材料的总体强度上升.     

若干固体材料脆-延性转变及宏观结构的实验研究

石灰岩、石蜡-松香-水泥粉混合物和环氧树脂等固体材料室温下的压缩变形实验表明,随着围压的加大和材料可塑性的增强,试件破坏形式由脆性转变为延性,在宏观结构上表现为从脆性单斜破裂、半脆性共轭破裂,到半延性和延性网状流动,以及延性均匀流动的转变.材料屈服后在应力-应变曲线上所出现的平缓段或应变硬化段对应着试件中的网络状或均匀塑性流动;随着应变的增大,当出现负坡或坡度减小现象时,则标志着试件内宏观破裂的贯通,在宏观破坏结构上往往表现为共轭流动网络与共轭破裂网络的重叠,前者网带近似正交,后者斜交.蠕变实验进一步表明,稳态蠕变幂次流动律的应力指数n 值的大小反映了试件不同的宏观流动结构:网络状流动,n 显著大于1,为非牛顿流;均匀流动,n 等于或近似于1,为牛顿流或近似牛顿流.     

中下地壳温度压力条件下岩石半脆性蠕变的实验研究

本文着重介绍了在中下地壳温度、压力条件下进行的几种岩石半脆性蠕变的实验研究结果。通过对这些岩石的蠕变曲线、蠕变类型、蠕变速度和时间、蠕变应变的关系、稳态蠕变速度-流动应力和蠕变破坏特征的观测、分析,阐述了地壳岩石半脆性蠕变的基本规律,并在温度、围压-流动应力座标系中给出了岩石半脆性蠕变的分区     

天然麻粒岩高温流变实验研究

本实验在气体介质三轴高温流变仪上,采用怀安瓦窑口麻粒岩,在温度900～1200℃、围压300 MPa、应变速率10~(-4)～10~(-6)/s条件下,开展高温流变实验.实验样品麻粒岩由斜长石(52%)、单斜辉石和斜方辉石(40%)、石英(3%)、磁铁矿和钛铁矿(5%)组成,矿物平均粒度为:斜长石294μm、单斜辉石和斜方辉石282μm、石英97μm、磁铁矿和钛铁矿109μm.利用傅里叶变换红外光谱仪分析获得变形后样品的水含量约为0.17±0.05wt%.实验样品的强度随温度升高而降低,随应变速率降低而降低.基于力学数据,采用稳态流变方程,获得实验样品在900～1000℃时的应力指数为8.1～12.9,在1050～1150℃时的应力指数为4.8～5.8,平均值5.2.应力指数随着温度升高而降低.显微结构和成分分析表明,在900℃时麻粒岩出现矿物压扁与定向拉长特征,样品以位错滑移和微破裂变形为主;在950～1000℃时,麻粒岩样品中颗粒边界变得圆滑,表现出位错攀移特征,辉石和磁铁矿边缘出现微量熔体;在1050～1200℃时麻粒岩出现部分熔融,而且随着温度和实验时间(应变)增加,熔体含量增加,熔体结晶出微粒斜长石、辉石和橄榄石,部分辉石通过固体反应生成橄榄石.颗粒边界熔体和矿物反应促进了扩散作用,导致位错攀移和熔体引起的扩散蠕变共同控制了麻粒岩的高温流变.     

橄榄石单晶体高温蠕变

作者首次采用中国河北大麻坪橄榄石单晶体做原始变形材料,在温度1200—1500℃,应力16—175 MPa,氧分压10~(-4)—10~(-10)atm 条件下,对上地幔流变学的有关三个问题进行了详细研究:(1)化学环境(氧分压和斜方辉石缓冲剂)对橄榄石流变性质的制约作用;(2)详细测定橄榄石单晶体流变参数和建立流变本构方程;(3)对橄榄石单晶体[110]c 方向的三个蠕变机制进行研究,这些新的高温实验成果第一次为研究中国东部岩石圈动力学提供了有意义的定量资料.     

不同围压条件下花岗岩变形破坏过程中的声发射时序特征

在室温、围压 50— 60 0MPa范围内 ,采用以Pb为围压介质的三轴实验装置 ,对花岗岩变形破坏过程中的声发射序列特征进行的研究表明 ,花岗岩强度随围压增加而增大 .低围压下 ,样品破坏时系统不失稳 ,破裂前后声发射稀少且时间分布较为随机 .随围压的增高 ,样品破坏时系统失稳 ,随后出现粘滑 ;声发射出现时间随围压增加而提前 .以破坏时应力降发生时间为界 ,一个显著的特征是破前声发射累积数随时间指数增长 ,增长速率随围压增加而加快 ;而破后各粘滑段的声发射累积数随时间却呈线性增长 .声发射b值随围压增加有减小的趋势 .声发射序列时间结构的 f(α) α谱研究表明 ,其多分形性质主要决定于时间密集特征 ,标度指数α的分布范围随围压增加有减小的趋势 .粘滑过程中 ,应力降幅度、应力降释放率及粘滑事件时间间隔均随围压增加而增大。     

橄榄石的同系温度T/T_m:对上地幔蠕变与橄榄石组构转变的启示

同系温度为晶体材料的绝对温度(T)与其熔点(T_m)的比值,是对比晶体流变强度的重要参数之一.橄榄石(Mg,Fe)_2Si O_4的熔点随含铁量和含水量的增加而降低,随压力增加而升高,高压下橄榄石的相变可导致熔点随压力发生不连续变化.本文对前人的铁橄榄石(Fe2Si O_4)熔融实验结果进行校正,确定铁橄榄石-γ相Fe2Si O_4-熔体的三联点位于6.4GPa和1793K.然后使用广义混合律建立了常压至6.4GPa,无水橄榄石的固相线和液相线与含铁量和压力的关系.橄榄石T/T_m随深度的变化可用于定性对比具有不同热状态和橄榄石成分的上地幔流变强度,T/T_m=0.5的深度界定了上地幔从半脆性变形到完全塑性变形的转换深度.克拉通岩石圈地幔的橄榄石T/T_m显著低于造山带和伸展盆地,一直到岩石圈-软流圈边界才与周围地幔趋于一致(T/T_m0.66),表明克拉通的岩石圈强度较高.此外,使用T/T_m分析橄榄石的变形实验结果,发现含水量对橄榄石组构的影响与压力密切相关,但是水对橄榄石流变强度的弱化作用及其与橄榄石同系温度的关系尚需进一步研究.低于6.4GPa(200km),T/T_m控制了橄榄石[100]和[001]位错滑移的转变.在上地幔10~-(12)~10~-(15)s~(-1)的应变速率和低应力条件下,橄榄石[100](010)位错滑移系(A型组构)的稳定域为T/T_m0.55~0.60.T/T_m0.55~0.60时,[001]位错滑移更易于发生,低T/T_m使橄榄石的主控位错滑移系转变为[001](100),形成C型组构.这与天然变形的橄榄岩普遍发育橄榄石A型组构,而超高压变质带中经历了深俯冲的橄榄岩发育橄榄石C型组构一致.而[001](010)位错滑移系(B型组构)受T/T_m和应力的共同影响.因此,橄榄石的同系温度建立了将变形实验结果外延到上地幔流变的桥梁.克拉通地区的上地幔地震波各向异性需要一个四层模型来拟合:上层为残留的A型组构,中间为B型组构,岩石圈-软流圈边界为新生的A型或B型组构,以及Lehmann不连续面之下以扩散蠕变为主的软流圈地幔.对橄榄石组构转变机制的认识是通过地震波各向异性追踪上地幔含水量的分布和地幔流动的关键.     

围压对低渗砂岩渗透率有效应力系数的影响

多孔岩石渗透率有效应力系数的取值至今仍没有一致的认识,影响取值的因素较为复杂.为了探索围压对低渗砂岩渗透率有效应力系数的影响,实验上采用较大的围压范围(10MPa～50MPa),选取两块低渗致密砂岩岩样,进行渗透率测试,并利用二元线性回归方法,计算了不同围压组合下的渗透率有效应力系数值,获取了该系数随围压的变化趋势.实验中,两块岩样的渗透率有效应力系数随围压的增加而减小,但各自的减小趋势略有不同.利用Bernabé和Berryman提出的模型,理论上解释了围压对渗透率有效应力系数的影响,并得到渗透率有效应力系数的下限值为岩样孔隙度.尽管渗透率有效应力系数不是一个常数,但可以表示为压差的函数,进而起到简化分析的作用.     

华北地区新生代碱性玄武岩中超镁铁质捕掳体的初步研究(续)

(二)由新变晶大小估计地幔应力近些年来,据天然橄榄石的变形结构、显微亚构造及实验研究的结果,提出了多种估计上地幔应力的方法。Nicolas(1978)曾对此进行过综合评述。归纳起来有两类方法,一类是建立在位错显微构造基础上的方法,如根据橄榄石的位错密度和位错曲率与应力之间的经验关系或亚颗粒大小与应力之间的关系来估算应力值;另一类方法是由动力重结晶的橄榄石晶粒(新变晶)的大小来估计上地幔应力的方法。对同一样品采用上述诸方法常不能得到相     

高温高压下石灰岩剪切网络的实验研究

主要介绍在不同温度(300—1000℃)、围压(300—600 MPa)条件下灰岩的等应变率压缩实验和蠕变实验以及变形样品的显微观测、分析结果.通过研究岩石的流变特性、变形形迹和变形机制及其受温度,压力、应变率等因素的影响,确定由共轭网络状塑性流动向均匀塑性流动过渡的温、压界限,并讨论了相应的流变学标志和微观构造标志.上述结果为大陆岩石层多层构造网络的研究提供了实验依据.     

Olivine flow mechanisms at 8 GPa

The mechanisms responsible for high-temperature olivine deformation are investigated at a pressure of 8 GPa and temperatures up to 1780 K. San Carlos olivine specimens of different average grain sizes (0.5 and 5 μm) were deformed simultaneously between hard-alumina pistons during relaxation experiments. These experiments are carried out in a multi-anvil high-pressure apparatus coupled with synchrotron X-ray radiation. The different grain-size specimens experienced identical P-T-stress condition at any given time. A new method for measuring strains and strain rates (≥10⁻⁶ s⁻¹) of specimens at high pressure is documented. This method uses time-resolved in situ X-ray imaging and an image-analysis computation. The microstructures of run products, recovered after being quenched at different temperatures were characterized by transmission electron microscopy (TEM). We find that high-temperature olivine flow is grain-size insensitive at 8 GPa, which suggests that dislocation creep dominates olivine deformation at high pressure. This result is confirmed by the TEM investigation of our deformed specimens in which we find evidences of the activation of olivine dislocation slip systems. Specimen microstructures are consistent with dynamic recrystallization as an assisting process in olivine deformation during the high-pressure experiments. Extrapolation of our results to the low stress level and large grain size expected in the mantle suggests that dislocation creep assisted by dynamic recrystallization may also dominate natural olivine deformation in the upper mantle.     

山西大同第四纪火山岩中幔源包体的变形特征及其上地幔流变学意义

山西大同第四纪玄武岩中含有少量小型的幔源包体，主要为尖晶石二辉橄榄岩。包体的变形显微构造反映了上地幔条件下至少有两次变形事件；包体的平衡温度为９００～１０５０℃，平衡压力为１．１～１．７ＧＰａ，对应的来源深度为４０～６０ｋｍ。由包体的变形显微构造推导的上地幔流变学参数表明，该地区上地幔符合大陆拉张带上地幔的特征。在第四纪时期，该地区上地幔仍然继续其底辟上涌过程     

Numerical studies of non-Newtonian mantle convection

Numerical model computations have been carried out to determine how the stress-dependence of non-Newtonian viscosity affects the flow structure of thermal convection. The viscosity laws have been chosen in accordance with present knowledge of upper mantle rheology, based on the diffusion and dislocation creep laws of olivine. The results show that there are important differences between the structures of Newtonian and non-Newtonian convection. While the Newtonian models are insufficient in some respects, the non-Newtonian solutions can explain the characteristics of the real mantle flow. However, this may require a faster plastic deformation than power law dislocation creep, at least in the high-stress regions of the mantle, e.g. at the active plate margins.     

Deformation mechanism maps for polycrystalline galena

A deformation mechanism map, depicting the fields of stress and temperature in which modes of plastic flow are dominant (i.e. provide the fastest strain rate) has been calculated for polycrystalline, stoichiometric galena for each of two grain sizes; namely, 10 and 10³ μm. The deformation mechanisms considered were dislocation glide, dislocation creep (i.e. creep involving dislocation climb), Nabarro-Herring creep and Coble creep.During folding and related tectonic deformation in the earth's crust steady-state flow of galena may occur by either dislocation or diffusion creep at very low differential stresses (typically ranging from 100 bars down to 10^?2 bar, or less). The dislocation creep field will be enlarged at the expense of that for diffusion creep, however, if (a) the stress dependence of strain rate for dislocation creep decreases at low stresses and if the grain size is greater than 10 μm, or (b) diffusion creep rates decline at high strains due to the presence of second-phase particles in the grain boundaries. It is probable that dislocation glide will be the dominant deformation mechanism in galena only at low temperatures and fast strain rates and it is unlikely to be the dominant mechanism during folding. Kinking may have some potential as an indicator of these temperatures and strain rates.     

Structural superplastic creep and linear viscosity in the earth's mantle

The rheology of dry polycrystalline olivine is examined by adopting a hyperbolic sine flow law (which reduces to a power law below 3 kbars) for high stress behavior, and a model for diffusion accommodated, coherent, grain boundary sliding (structural superplastic creep) for low stress behavior. The model for superplastic creep gives a linear relation between stress and strain rate and is consistent with the behavior of polycrystalline olivine during ductile faulting experiments (Post, 1973). For any given stable grain size, linear superplastic creep is promoted by relatively low stress and temperature. For a 1 -cm grain size and a homologous temperature between 0.6 and 0.8, superplastic creep dominates below transition stresses between 402 and 25 bars, respectively. Transition stresses are higher for smaller grain size and lower temperature. If grain size is stress dependent, superplastic creep is non-linear and dominates above a stress of 300 bars. Below that stress, relatively lower temperatures promote superplastic creep. Grain size may be stabilized by either physical or kinetic inhibition of grain growth, thereby allowing linear superplastic creep in the mantle. Results suggest that superplastic creep can dominate in most of the upper mantle except possibly for the asthenosphere where homologous temperatures are maximal and hyperbolic sine law creep can dominate. Mantle diapirism is at least in part accomplished by superplastic flow above and along the margins of the rising diapir.     

An experimental study on semi-brittle and plastic rheology of Panzhihua gabbro

Rheological properties of the crust and upper mantle are essential data that are needed in modelling the mechanical behaviour of the shallow part of the earth. The importance of such data has been seen in discussions about the strength profile of continen…     

构造地震的前兆理论——震源孕育的膨胀-蠕动模式

较详细地讨论了构造地震的震源孕育情况;在考虑了动摩擦效应后,进一步对震源孕育过程和各种物理量的变化规律进行了分析和计算,提出了震源孕育的膨张一蠕动模式.该模式将孕震过程划分为:弹性变形、非弹性变形（膨胀）、前兆蠕动（断层面局部破裂）、加速蠕动（短期和临震）、整体错动（断层面全部破裂）--发震、震后调整等六个阶段.最后讨论了两类不同前兆、蠕裂和崩裂、非弹性变形（膨胀）速度的变化、各种前兆异常的基本形态、短临前兆的物理基础等问题.研究结果表明,膨胀-蠕动模式可能是认识地震前兆现象本质和发展预报技术的一个物理和力学基础.     

Effects of cation disordering in a natural MgAl2O4 spinel observed by rectangular parallelepiped ultrasonic resonance and Raman measurements

At moderate temperatures, the elastic properties of natural MgAl₂O₄ spinel differ in several significant ways from properties of synthetic spinels. Below 1000 K, the ultrasonic resonant frequencies of an ordered natural spinel change significantly after heat treatment; at higher temperatures, both types of spinels have similar resonant responses. The temperature derivatives of the elastic constants of an ordered spinel also differ from those of disordered spinels at moderate temperatures; again, at higher temperatures, both types of spinels have similar behaviors. The Raman spectra also differ below 1000 K for ordered natural and disordered spinels and are similar at higher temperatures and after cooling to ambient temperature. We associate these changes in ultrasonic resonance and Raman spectra of spinel with cation disordering at high temperature which may be quenched by cooling. We deduce estimates of the inversion parameter from the relative intensities of the two A_1g Raman modes in very good agreement with estimates made from other measurements. We find thatC ₁₁ andC ₁₂ decrease by 4 and 8%, respectively, with 20% inversion in spinel;C ₄₄ is less sensitive to cation order. These results imply that previous measurements of the adiabatic elastic constants of spinels at ambient conditions have been affected by the state of cation disorder of the specimen.     

具有割缝的大理岩试件破坏过程的有限元模拟

本文使用应变软化的弹塑性本构模型,用有限元方法对具有中心斜割缝的岩石试件在轴压下的破坏过程进行了数值模拟。得到了与实验观察相当一致的结果:在割线端部附近,首先发生张破裂,裂纹的扩张是逐渐地弯向试件的轴线方向,并变为稳定的。随着轴向压力增加,在张裂纹的相反方向上出现共轭的剪破裂。这些现象与割缝顶端附近材料的应变软化性质有关。说明所采用的有限元方法是研究岩石材料破裂过程的一种可行的方法。