流体包裹体压力计研究之二:高温高压下碳氢化合物的拉曼光谱

在温度23～315℃、压力高达近2000MPa下用金刚石压腔下研究了正庚烷、环己烷及其混合物的拉曼光谱特征。结果表明：环己烷和正庚烷混合,只是改变了环己烷及正庚烷的平均C-H伸缩振动的拉曼位移,但是并不影响其P-△^-vp关系式。另外,经过数据拟合,得到了平均C-H伸缩振动的拉曼位移与压力的关系为：P=78．21（△^-vp）＋71．56。该公式可以用来作为流体包裹体尤其是油气包裹体的压力计。     

高温高压下黄铁矿热力学性质的第一性原理研究

黄铁矿是自然界中分布最为广泛的硫化物矿物,同时也是重要的造矿矿物,在金属矿床、沉积岩、变质岩、花岗岩、基性-超基性岩浆岩、以及地幔岩中都有大量出现。因此,研究黄铁矿在不同温度压力下的热力学性质可以为深入探讨与黄铁矿有关的成岩、成矿、成藏问题提供有用的矿物学依据。本文利用基于密度泛函微扰理论的第一性原理方法,采用准谐近似计算了黄铁矿在高温高压下的热力学性质。我们计算的黄铁矿的晶格常数、零压下的体积模量及其对压力的导数与前人的实验及理论计算结果吻合得很好,零压下等压热容和熵随温度的变化与实验结果有很好的一致性。尤其是,本文计算了直至2500K、100GPa的高温高压下黄铁矿的等温体积模量、热膨胀系数、热容和熵等热力学性质。这为在有硫参与的情况下,人们开展下地壳-岩石圈地幔深度的地球动力学模拟和建立地球物理模型提供了有用的信息。     

高温高压下石膏脱水相变的原位拉曼光谱研究

本文运用激光拉曼光谱仪,利用水热金刚石压腔装置对高温高压条件下石膏-水体系中的石膏脱水相变进行拉曼光谱研究.在压力0.1 MPa～837.9 MPa和温度16～200 ℃条件下通过系列实验对相变的过程进行了原位光谱分析.与人们已知的无水条件下石膏分两步脱水的过程不同,高压下石膏在饱和水环境下倾向于一次性的脱去所有结晶水而形成无水石膏,实验中没有观察到半水石膏的出现.通过实验数据得到石膏和无水石膏的转折温度和平衡压力间的关系式为P(MPa)=19.56·T(℃)-2926.5.     

Raman Spectroscopy of Garnet—group Minerals

The Raman spectra of the natural end members of the garnet-group minerals,which include pyrope, almandine and spessarite of Fe-Al garnet series and grossularite ,andradite and uvarovite of Ca-Fe garnet series, have been strdied.Measured Raman spectra of these minerals are reasonably and qualitatively assigned to the internal modes, translational and rotatory modes of SiO4 tetrahedra, as well as the translational motion of bivalent cations in the X site.The stretch and rotatory A1g modes for the Fe-Al garnet series show obvious Raman shifts as compared with those for the Ca-Fe garnet series ,owing to the cations residing in the Xsite connected with SiO4 tetrahedra by sharing the two edges.The Raman shifts of all members within either of the series are attributed mainly to the properties of cations in the X site for the Fe-Al garnet series andin the Y site for the Ca-Fe garnet series.     

Thermodynamic properties of San Carlos olivine at high temperature and high pressure

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.     

流体包裹体压力计研究之二:高温高压下碳氢化合物的拉曼光诸

在温度23～315℃、压力高达近2000MPa下用金刚石压腔下研究了正庚烷、环己烷及其混合物的拉曼光谱特征.结果表明:环已烷和正庚烷混合,只是改变了环已烷及正庚烷的平均C-H伸缩振动的拉曼位移,但是并不影响其P-△vp关系式.另外,经过数据拟合,得到了平均C-H伸缩振动的拉曼位移与压力的关系为:P=78.21(△vp)+71.56.该公式可以用来作为流体包裹体尤其是油气包裹体的压力计.     

In situ Raman spectroscopy on kerogen at high temperatures and high pressures

Kerogen samples were treated at temperatures and pressures up to 25–600°C and ~9 GPa, respectively. In situ micro-Raman spectroscopy was used to measure the systematic changes in the first-order Raman spectral features during the process of temperature or pressure increment. Three Raman bands, D1, D2, and G bands, were examined to characterize the structural and chemical changes of kerogen at high temperatures and pressures. We found that the wavenumbers of D1, D2 and G bands showed a linear variation with both temperature and pressure. Therefore, a correlation between R1 and R2 and the peak temperature in regionally metamorphosed rocks cannot be applied to this work. This result implies that the G band may serve as a temperature or pressure indicator during the promotion of maturation of kerogen. Kerogen possesses reversible properties in contrast with the natural samples recovered from the field suffered from prolonged thermal history during regional metamorphism.     

Viscosity of albite melt at high pressure and high temperature

 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     

Electrical conductivity of K-feldspar at high temperature and high pressure

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.     

Carrara大理岩高温高压变形实验研究

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。     

X-ray diffraction study of magnesite at high pressure and high temperature

 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, (∂K_T/∂T)_P=−0.021(2) GPaK⁻¹, (dα/∂P)_T=−1.81×10⁻⁶ GPa⁻¹K⁻¹ and (∂K_T/∂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, (∂K_T/∂T)_P=−0.017(1) GPaK⁻¹, (dα/∂P)_T= −1.41×10⁻⁶ GPa⁻¹K⁻¹ and (∂K_T/∂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 (∂K_T/∂T)_P, (∂α/∂P)_T and (∂K_T/∂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     

The Electrical Conductivity of Gabbro at High Temperature and High Pressure

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.     

高温高压下超临界二氧化碳作用对花岗岩力学性质影响的试验研究

为了研究二氧化碳基增强型地热系统核心及邻近区域中超临界二氧化碳(ScCO₂)作用对岩石力学性能的影响,设计了纯ScCO₂与干燥花岗岩作用,ScCO₂、水蒸气与干燥花岗岩作用,ScCO₂与在水中浸泡了24 h后的花岗岩作用3种试验条件,每种试验条件下均开展了210、240、270℃温度下的试验。对ScCO₂作用后的岩样以及一个未经处理的对比样先后开展纵波波速测试以及单轴压缩试验,获得了岩石的纵波波速、单轴抗压强度以及弹性模量。纵波波速试验结果表明,在上述3种试验条件下,花岗岩样的波速会都会发生一定程度的降低。单轴压缩试验结果表明,ScCO₂作用后的岩石单轴抗压强度及弹性模量都几乎没有受到影响,但是从破坏模式看,未经处理的岩石以张拉破坏为主,处理后的岩石以剪切破坏为主,并且随着温度的升高剪切破坏越明显。试验结果说明,在不存在水或者仅有微量水存在的情况下,ScCO₂的作用对岩石产生轻微损伤,岩样的刚性减弱、塑性增强,导致其纵波波速有少量的下...     

Friction in faulted rock at high temperature and pressure

Two hundred observations of frictional behavior of seven low-porosity silicate rocks were made at temperatures to 700°C and pressures from 2.5 to 6 kbar. For all rocks except one, peridotite, stick-slip occurred at low temperature and gave way to stable sliding at some high temperature, different for each rock. These differences could be related to the presence or absence of minerals such as amphibole, mica, or serpentine. Up to some temperature, depending on rock type, the friction stress was relatively unaffected by temperature. The shear stress decreased at higher temperature, and in some cases such decrease was related to the coincidence of fracture and friction strength. While somewhat dependent on rock type, the friction stress for the seven rocks studied was about the same, within 10–15%. Up to 265°C, water had little effect on the frictional behavior of faulted granite at 3 kbar effective pressure. The frictional stresses measured in the laboratory were significantly higher than estimated for natural faults. This difference could be accounted for by high pore pressure or weak alteration materials in the natural fault zone.     

Phase transitions in leucite: Order parameter behaviour and the Landau potential deduced from Raman spectroscopy and birefringence studies

Hard mode Raman Spectroscopy and optical birefringence studies have been used to evaluate the temperature behaviour of order parameters for the cubictetragonal phase transition in leucite. There is a strong temperature-dependence of Raman line frequencies near 498 cm^–1 and 529 cm^–1, and the optical birefringence decreases towards zero on heating. Above the transition temperature leucite still shows slight birefringence, which correlates with the persistence of the 200 X-ray reflexion at these temperatures, and is not compatible with the ideal cubic symmetry. Quantitative observations of the temperature evolution of Raman line-frequencies and the birefringence are consistent with an order parameter showing T _1g symmetry, and a nearly-tricritical phase transition behaviour. The results of earlier X-ray and DSC studies imply the operation of an additional order parameter, with E _g symmetry; this is observed, but its influence on the transition behaviour is significant only at temperatures close to T _c. The two order parameters are related via linear-quadratic or biquadratic coupling. We develop the form of the Landau Potential for leucite — including both order parameters and their couplings — to discuss the present observations and previous structural data.     

冲绳海槽浮岩的高温高压纵波速度

对采自冲绳海槽中部海底的浮岩样品和邻近陆地樱岛火山的安山岩样品进行了温度 (常温 - 15 0 0℃ )与压力 (常压 - 2 .4 GPa)实验 ,测得在较低温度 -压力条件下 (<1GPa,<80 0℃ )浮岩样品的纵波速度小于安山岩样品的纵波速度 ,在较高温度 -压力条件下 (>1GPa,>80 0℃ )二者的纵波速度接近一致 (5 .9km /s)。 1GPa/80 0℃是浮岩样品和安山岩样品的热动力相变点 ,推测该点的深度大于 18km。     

Reaction of forsterite with hydrogen molecules at high pressure and temperature

High pressure and temperature reactions of a mixture of forsterite and hydrogen molecules have been carried out using a laser heated diamond anvil cell at 9.8–13.2 GPa and ~1,000 K. In situ X-ray diffraction measurements showed no sign of decomposition or phase transitions of the forsterite under these experimental conditions, indicating that the olivine structure was maintained throughout all runs. However, a substantial expansion of the unit cell volume of the forsterite was observed for samples down to ~3 GPa upon quenching to ambient pressure at room temperature. The Raman spectroscopy measurements under pressure showed significant shifts of the Raman peaks of the Si–O vibration modes for forsterite and of the intramolecular vibration mode for H₂ molecules toward a lower frequency after heating. Additionally, no OH vibration modes were observed by Raman and FT-IR spectroscopic measurements. These lines of evidence show that the observed volume expansion in forsterite is not explained by the incorporation of hydrogen atoms as hydroxyl, but suggest the presence of hydrogen as molecules in the forsterite structure under these high pressure and temperature conditions.     

Simulation of thermodynamic mixing properties of garnet solid solutions at high temperatures and pressures

We present results of high temperature, high pressure atomistic simulations aimed at determining the thermodynamic mixing properties of key binary garnet solid solutions. Computations cover the pressure range 0–15 GPa and the temperature range 0–2000 K. Through a combination of Monte-Carlo and lattice-dynamics calculations, we derive thermodynamic mixing properties for garnets with compositions along the pyrope–almandine and pyrope–grossular joins, and compare these with existing experimental data. Across the pressure–temperature range considered, simulations show virtually ideal mixing behaviour in garnet on the pyrope–almandine join, while large excess volumes and enthalpies of mixing are predicted for garnet along the pyrope–grossular join. Excess heat capacities and entropies are also examined. These simulations shed additional light on the link between the behaviour at the atomic level and macroscopic thermodynamic properties: we illustrate the importance of certain atomistic Ca–Mg contacts in the pyrope–grossular solid solutions. For simulation techniques of this type to become sufficiently accurate for direct use in geological applications such as geothermobarometry, there is an urgent need for improved experimental determinations of several key quantities, such as the enthalpies of mixing along both joins.