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1.
含水对富铁橄榄石流变性的影响 总被引：3，自引：2，他引：3
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。 相似文献
2.
富铁橄榄石的高温变形实验研究 总被引：1，自引：3，他引：1
利用高精度Paterson气体介质变形装置对(Mg0.5,Fe0.5)2SiO4和(Mg0.7,Fe0.3)2SiO4橄榄石集合体进行了高温三轴压缩变形试验。首先用人工合成了纯铁橄榄石Fe2SiO4,然后用合成的纯铁橄榄石与天然圣卡罗橄榄石按一定比例混合烧结合成了含铁量分别为50％和30％的富铁橄榄石集合体Fo50和Fo70。三轴压缩蠕变变形试验在温度1223-1473 K和围压 300 MPa的条件下进行,差应力为10-300 MPa,应变率为10-7-10-4s-1,每个试件的最大变形量为20％．利用三维非线性方法对蠕变数据进行拟合,得出的流动律中,Fo50应力指数为4．1,活化能为499kJ／mol;Fo70应力指数为4．3,活化能为510kJ／ mol。将实验结果与Fo90圣卡罗橄榄石集合体的强度进行对比,发现含铁量的增加使橄榄石的强度明显下降,Fo50橄榄石集合体比Fo70的粘性低一个量级,Fo70比Fo90的粘性低一个量级。从而得到了含铁量对橄榄石的粘性(强度)影响的初步试验结果。 相似文献
3.
单斜辉石作为大陆下地壳以及上地幔岩石的重要组成矿物,其在高温高压条件下的流变行为已有大量的实验研究。本文在综述以往对单斜辉石流变实验研究的基础上,讨论了影响其流变行为的各种因素及其地质意义,并指出了现存的问题及今后的研究趋势。影响单斜辉石流变性质的因素主要有流体（包括水和熔体）、粒度、化学成分、氧逸度以及温度与压力条件等。微量结构水可以显著增大单斜辉石单晶和多晶集合体的蠕变速率,降低其流变强度。熔体对单斜辉石强度的影响与熔体的含量和分布状态有关,呈三联点分布于矿物颗粒间的熔体对样品强度影响较小,只有当熔体呈薄膜状湿润颗粒边界时,熔体的弱化作用才显著。粒度主要影响单斜辉石的变形机制,单斜辉石集合体晶粒粒度的减小会促使变形机制由位错蠕变转变为扩散蠕变,较细粒的单斜辉石在扩散蠕变域内的应力与粒度呈线性负相关,而在位错蠕变域,应力与粒度无明显相关性。关于铁含量对单斜辉石的影响尚未有直接的实验研究,而对比前人在相同实验条件下采用不同铁含量的单斜辉石的扩散蠕变实验研究显示,单斜辉石中铁含量与蠕变速率可能呈正相关。氧逸度的升高对单斜辉石单晶的蠕变强度有轻微的弱化作用,而关于氧逸度对单斜辉石集合体流变... 相似文献
4.
橄榄石集合体中与位错蠕变相伴随的粒间滑动 总被引：2，自引：0，他引：2
为了研究橄榄岩位错蠕变过程中粒间滑动所起的作用,对经脱水干燥的橄榄石集合体试件进行了一系列的变形试验。三轴压缩蠕变试验在T=1473K、P=200和400MPa条件下使用一台高分辨率气体介质变形装置进行,每个试件在介于100~250MPa之间的不同应力水平下变形,得到的应变率介于10-4 ~10-6S-1之间。随着差应力的增加,得到扩散蠕变到位错蠕变的过渡,在位错蠕变域,易滑动体系在~50MPa和颗粒尺寸为15μm时伴随粒间滑动。这一粒径敏感蠕变域由应力指数3.2±0.1和粒径指数1.8±0.2来刻划。将这一流动律与其他扩散和位错蠕变结果进行对比,表明本文得出的流动律可应用于粒度小于100μm和差应力大于20MPa时的岩石流动。因此,与粒间滑动相伴的位错蠕变可能是上地幔岩石圈剪切带变形局部化的主要变形机制。 相似文献
5.
压力对橄榄石流变性的影响 总被引：2，自引：4，他引：2
本文给出细粒橄榄石集合体在位错蠕变域中压力效应的实验结果。对干燥、人工合成的橄榄石集合体进行了三轴压缩实验,试验在一台高分辨率的气体介质试验机上进行。典型的常载荷蠕变试验温度为1473K或1523K,围压为400MPa、200MPa、400MPa、200MPa。当差压力和温度给定时,试件在400MPa围压下,变形速度较200MPa围压下要慢。实验得出的细粒橄榄石集合体在位错蠕变域中的活化体积值为(23±3)×10~(-6)m~3/mol。最后,对实验结果在地幔动力学中的应用进行了讨论。 相似文献
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西藏罗布莎地幔橄榄岩变形显微构造特征及其地质意义 总被引：1，自引：0，他引：1
地幔橄榄岩是罗布莎蛇绿岩的主要组成成分之一,通过显微构造特征可对其变形特征进行分析,确定流变学参数,探讨地幔橄榄岩的变形历史。以蛇纹石化程度较低的二辉橄榄岩和方辉橄榄岩为研究对象,橄榄石位错特征研究显示,本区橄榄石主要发育了低温常见的直线型自由位错,局部可见位错弓弯、位错环、位错壁等高温位错,反映罗布莎地幔橄榄岩变形以低温塑性流变为主,局部经历了高温塑性流变,主导变形机制为位错蠕变。橄榄石自由位错统计结果表明,二辉橄榄岩中的橄榄石自由位错密度为4.422×107/cm2,方辉橄榄岩中的橄榄石为9.137×107/cm2,变形过程中所受差异应力分别为65MPa和93MPa。橄榄石和斜方辉石显微组构测量采用了电子背散射衍射技术(EBSD),分析结果表明,橄榄石均发育A型组构,为浅部地幔常见的组构类型,该结果与金刚石、柯石英等超高压矿物所指示的形成深度不一致。 相似文献
8.
橄榄石集合体扭转大变形实验研究 总被引：5，自引：4，他引：1
对(Mg0.5,Fe0.5)2SiO4和(Mg0.7、Fe0.3)2SiO4橄榄石集合体进行了高温高压扭转大变形实验研究.试验在高精度和高分辨率Paterson气体介质变形试验机上进行,试验温度为1473K,围压为300MPa,应变率为10-4～10-5S-1,剪切应力为82～124MPa,剪切应变为～400%,将变形后试件沿轴向切开进行了显微结构分析,确定了不同纵截面上橄榄石的颗粒尺寸.由蠕变数据拟合出的流动律中,应力指数为与三轴压缩实验给出的应力指数吻合.利用EBSD方法分别对变形前后试件中橄榄石的晶格最优取向(LPO)进行了测定.在富铁橄榄石样品中观测到的最优晶格取向表明滑动属于(okl)[100]滑动系统.这个结果与Bystficky等人在Fo90种观测到的最优晶格取向特征是一致的. 相似文献
9.
本文介绍了采用透射电子显微镜观察研究福建明溪大洋窠上第三系玻基玄武岩中的包体橄榄石的位错结构。研究表明,该地幔源包体橄榄石中存在位错壁、自由位错、位错弓弯和位错环等,它们是该橄榄石在上地幔的高温低应力条件下发生复杂蠕变的产物。根据该地包体橄榄石中自由位错密度(统计值为2.0×10~8cm~(-2)和共生辉石的化学成分,估算出福建明溪大洋窠玻基玄武岩中幔源包体的变形条件为:温度(T)为1070℃;压力(P)为2480MPa;深度(Z)为79.3km;流变应力(σ_1-σ_3)为136MPa;流变速率(ε)为7.6×10~(-13)s~(-1);粘稠度(η)为0.8×10~(20)poise。 相似文献
10.
嵇少丞 《大地构造与成矿学》2013,37(2)
迄今为止,上地幔流变学的研究主要集中于橄榄石单晶与多晶集合体的实验和野外观察,但对辉石的流变学特征知之甚少,虽然辉石亦是上地幔岩石的主要组成矿物.因此,查清斜方辉石的流变学行为、塑性变形机制、重结晶作用以及与其共生的橄榄石之间的流变强度差等,现已成为国际地学界研究的新的热点课题.新疆中天山南缘库米什地区的榆树沟高压变质地体中出现地幔超糜棱岩,其中带状拉伸的斜方辉石(En90)碎斑晶发生了强烈地弯滑褶皱,周围橄榄石(Fo90)重结晶成细粒(～10 μm)多晶基质.显微构造研究表明,单晶斜方辉石的褶皱主要通过单一的(100)[001]滑移进行的,而细粒重结晶橄榄石基质的变形机制则最可能以超塑性(颗粒边界滑移与扩散)为主.单晶斜方辉石发生弯滑褶皱,而不形成常见的膝折(Kinks),说明所处物理化学条件下斜方辉石晶体位错攀移与原子扩散并不足够活跃.此外,即使其晶格发生高达140.的旋转,斜方辉石依然没有发生光学显微镜下足以识别的重结晶结构,说明启动重结晶作用的临界剪切应变应不少于5.5.根据现有的层状材料的褶皱理论,推测榆树沟高压变质地体中地幔岩发生塑性变形时位错蠕变的斜方辉石的流动强度至少比相同条件下超塑性变形的细粒橄榄石多晶基质高近2个数量级. 相似文献
11.
A. Suzuki E. Ohtani K. Funakoshi H. Terasaki T. Kubo 《Physics and Chemistry of Minerals》2002,29(3):159-165
The viscosity of albite (NaAlSi3O8) melt was measured at high pressure by the in situ falling-sphere method using a high-resolution X-ray CCD camera and a large-volume
multianvil apparatus installed at SPring-8. This system enabled us to conduct in situ viscosity measurements more accurately
than that using the conventional technique at pressures of up to several gigapascals and viscosity in the order of 100 Pa s. The viscosity of albite melt is 5.8 Pa s at 2.6 GPa and 2.2 Pa s at 5.3 GPa and 1973 K. Experiments at 1873 and 1973
K show that the decrease in viscosity continues to 5.3 GPa. The activation energy for viscosity is estimated to be 316(8)
kJ mol−1 at 3.3 GPa. Molecular dynamics simulations suggest that a gradual decrease in viscosity of albite melt at high pressure may
be explained by structural changes such as an increase in the coordination number of aluminum in the melt.
Received: 6 January 2001 / Accepted: 27 August 2001 相似文献
12.
Haiying Hu Lidong Dai Heping Li Jianjun Jiang Keshi Hui 《Mineralogy and Petrology》2014,108(5):609-618
Electrical conductivity measurements on dry polycrystalline K-feldspar were performed at 1.0 to 3.0 GPa and 873 to 1,173 K with a multi-anvil high-pressure apparatus and the Solartron-1260 Impedance/Gain Phase Analyzer in the frequency range of 10?1 to 106 Hz. At each temperature the complex impedance displays a perfect semi-circular arc that represents the grain-interior conduction. Under the experimental conditions, electrical conductivity exponentially increases with increasing temperature and slightly decreases with increasing pressure; however, the effect of pressure on the conductivity is less pronounced than that of temperature. The activation enthalpy decreases slightly from 0.99 to 1.02 eV with increasing pressure, and the activation energy and activation volume for K-feldspar are 0.98 eV and 1.46?±?0.17 cm3/mol, respectively. According to these Arrhenius parameters, ionic conduction is proposed to be the dominant conduction mechanism in K-feldspar at high temperatures and pressures, and potassium ions are the charge carriers transporting by an interstitial mechanism. The diffusion coefficient of potassium at high temperatures was calculated from our conductivity data on K-feldspar using Nernst–Einstein equation, and the results were compared with the previous experimental results. 相似文献
13.
The electric conductivity of gabbro has been measured at 1.0 - 2.0 GPa and 320-700℃, and the conduction mechanism has been analyzed in terms of the impedance spectra.Experimental results indicated that the electric conductivity depends on the frequency of alternative current. Impedance arcs representing the conduction mechanism of grain interiors are displayed in the complex impedance plane, and the mechanism is dominated at high pressure.These arcs occur over the range of 102 - k× 105 Hz (k is the positive integer from 1 to 9). On the basis of our results and previous work, it is concluded that gabbro cannot form any high conductivity layer (HCL) in the middle-lower crust. 相似文献
14.
J. Zhang I. Martinez F. Guyot P. Gillet S. K. Saxena 《Physics and Chemistry of Minerals》1997,24(2):122-130
P–V–T measurements on magnesite MgCO3 have been carried out at high pressure and high temperature up to 8.6 GPa and 1285 K, using a DIA-type, cubic-anvil apparatus
(SAM-85) in conjunction with in situ synchrotron X-ray powder diffraction. Precise volumes are obtained by the use of data collected above 873 K on heating and
in the entire cooling cycle to minimize non-hydrostatic stress. From these data, the equation-of-state parameters are derived
from various approaches based on the Birch-Murnaghan equation of state and on the relevant thermodynamic relations. With K′0 fixed at 4, we obtain K0=103(1) GPa, α(K−1)=3.15(17)×10−5 +2.32(28)×10−8 T, (∂KT/∂T)P=−0.021(2) GPaK−1, (dα/∂P)T=−1.81×10−6 GPa−1K−1 and (∂KT/∂T)V= −0.007(1) GPaK−1; whereas the third-order Birch-Murnaghan equation of state with K′0 as an adjustable parameter yields the following values: K0=108(3) GPa, K′0=2.33(94), α(K−1)=3.08(16)×10−5+2.05(27) ×10−8 T, (∂KT/∂T)P=−0.017(1) GPaK−1, (dα/∂P)T= −1.41×10−6 GPa−1K−1 and (∂KT/∂T)V=−0.008(1) GPaK−1. Within the investigated P–T range, thermal pressure for magnesite increases linearly with temperature and is pressure (or
volume) dependent. The present measurements of room-temperature bulk modulus, of its pressure derivative, and of the extrapolated
zero-pressure volumes at high temperatures, are in agreement with previous single-crystal study and ultrasonic measurements,
whereas (∂KT/∂T)P, (∂α/∂P)T and (∂KT/∂T)V are determined for the first time in this compound. Using this new equation of state, thermodynamic calculations for the
reactions (1) magnesite=periclase+CO2 and (2) magnesite+enstatite=forsterite+CO2 are consistent with existing experimental phase equilibrium data.
Received September 28, 1995/Revised, accepted May 22, 1996 相似文献
15.
玄武岩及其高温高压相—榴辉岩的相组合,经历了长期的地质作用,反映出一定的时空条件。从高温高压实验矿物学,实验岩石学入手,对于以相组合出现的某些化学体系进行平衡条件研究,可揭示此类岩石形成的物理化学环境,并有助于阐明地球内部的物理状态、组成成分以及活动过程。 相似文献
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The phonon density of states (DOS) in iron has been measured in situ by nuclear resonance inelastic X-ray scattering (NRIXS) at high pressures and high temperatures in a resistively heated diamond anvil cell. The DOS data provide a variety of thermodynamic and elastic parameters essential for characterizing iron at depth in the Earth interior, such as average sound velocity, Debye temperature, atomic mean square displacement, average kinetic energy, vibrational entropy and specific heat. The NRIXS data were collected at 6, 20, and 29 GPa and at temperatures up to 920 K. Temperatures were directly determined from the measured spectra by the ratio of intensities of the phonon creation/annihilation side bands that are determined only by the Boltzmann factor. The change of the DOS caused by the structural transition from -Fe to -Fe is small and not resolvable within the experimental precision. However, the phonon energies in -Fe are clearly shifted to lower values with respect to - and -Fe. The temperature dependence of derived thermodynamic parameters is presented and compared with those obtained by Debyes model. The Debye temperatures that best describe the data decrease slightly with increasing temperature. 相似文献
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In this study, the thermal expansion and heat capacity of San Carlos olivine under high temperature and high pressure are reported. Combining accurate sound velocity data under different P–T conditions with density and heat capacity data at ambient pressure, the density, adiabatic bulk modulus, shear modulus, and most importantly, thermal expansion and heat capacity, of San Carlos are extracted to 14 GPa by a numerical procedure using classic thermodynamic relationships. These data are in agreement with published findings. To estimate the temperature gradient in the upper mantle, we also report the fitting equations of thermal expansion and heat capacity of San Carlos olivine as a function of both temperature and pressure to the P–T condition of the 410 km discontinuity, which provide the thermodynamic properties with increasing depth in the Earth’s interior. 相似文献
20.
Carrara大理岩高温高压变形实验研究 总被引：1，自引：0，他引：1
利用高精度的Paterson高温高压流变仪对Carrara大理岩在高温(873~1173K)高压(~300MPa)以及约10-6~10-3s-1应变速率下进行了三轴压缩变形实验。结果表明,在等应变速率条件下,其强度随着温度的升高而降低;在等温和等压条件下,其强度随着应变速率的增加先快速增加而后缓慢增加。在应变速率对差应力的双对数投图中,我们发现随着温度的升高拟合直线的斜率减小,并且在873K和高应变速率时973K温度下Carrara大理岩的流变本构方程服从指数律变化关系;而在高温(1073K和1173K)和973K低应变速率条件下Carrara大理岩的应力指数n为5.3~7.7,且服从幂次律变化关系。因此,Carrara大理岩在本研究的实验条件下主要有两种变形机制,一种是用指数律表示的高应力变形机制;另一种是用幂次律表示的中等应力变形机制。 相似文献