高温高压菱镁矿电导率实验研究

在俯冲带中,菱镁矿相比于其他碳酸盐矿物会在更高的温度压力环境下稳定存在,常被认为是地球深部碳循环的主要载体,其电学性质的研究对俯冲带及地球深部的电性结构具有重要的意义。本文在YJ-3000t高温高压设备上利用Solartron-1260阻抗/增益-相位分析仪,在1～3 GPa和773～1173 K条件下,对天然菱镁矿的电导率进行了原位测量。实验结果表明,在实验条件下,天然菱镁矿的电导率在10^-2～10^-7 S/m范围内,菱镁矿的电导率对温度有很强的依赖性,随着温度的升高,电导率增大,电导率与压力的关系呈正相关,随着压力的升高而增强。结合前人的研究成果及样品电导率随温度、压力的效应和活化能,可推断天然菱镁矿导电机制为大极化子导电。     

High pressure and high temperature fluid fugacities

High-temperature and high-pressure shock-wave data on fluids (pure species) have been combined with low-temperature and low-pressure data to generate a “corresponding state” equation in the virial format in reduced pressure and temperature for many species. The equation is then modified to obtain a similar equation of state for H₂O. The fugacities of the pure species in the CHO system can be calculated to a temperature of 3000 K and to a pressure of 1 megabar. However, dissociation of the pure species may invalidate the data over certain pressure-temperature ranges.     

Quartz-bearing C-O-H fluid inclusions diamond: Retracing the pressure-temperature path in the mantle using calibrated high temperature IR spectroscopy

Infrared spectra of C-O-H micro-inclusions were collected from a micro-inclusion bearing diamond during step-heating and freezing experiments to examine fluid speciation as a function of pressure and temperature. The inclusions contain H₂O, CO₂, carbonate, apatite, quartz and mica, which together represent the oxidising remnant mantle fluid composition after diamond crystallisation. The internal pressure of the inclusions, measured from calibrated shifts of the quartz peaks, increases from 1.3 GPa at ambient temperature, to approximately 4-5 GPa at 737 °C, close to the conditions of crystallisation of the host diamond in the mantle.     

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.     

高温高压下石英砂岩的电导率实验研究

利用交流阻抗谱实验技术,在0.5~2.0 GPa、573~873 K和10-1~106 Hz条件下,借助YJ-3000t紧装式六面顶高压设备和Solartron-1260阻抗/增益-相位分析仪测定了石英砂岩的电导率。实验结果表明:在测定的频率范围,样品的复阻抗的实部、虚部、模和相角对频率有很强的依赖性。随着温度升高,电导率增大,lgσT与1/T之间符合Arrhenius线性关系。通过拟合计算,获得了表征样品电学性质的指前因子、活化焓、活化能、活化体积等物性参数。杂质离子导电机制对高温高压下石英砂岩的导电行为提供了合理的解释。     

玄武岩的高温高压实验研究

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。     

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。     

Effect of saturating fluid composition on the rock microstructure,porosity, permeability and Vp under high pressure and temperature

The experiments on amphibolite and sandstone samples pressurized by gas (‘dry conditions’), pure water and water solutions of different composition under temperatures up to 850 °C at equal confining and pore pressure of 300 MPa revealed the different Vp behavior. On heating under gas pressure Vp decreases within all the temperature range, on heating under pressure of water and water solutions Vp at first decreases, but reaching a minimum value at temperature of about 650 °C increases. In order to interpret these data Vp, porosity, permeability and pore size distributions were measured on quenched samples. Microstructure and microprobe investigations also were carried out. The results obtained revealed porosity and permeability changes due to the rock microstructure changes with Vp trends synchronously. These microstructure changes initiating Vp changes were associated with rock thermal decompaction and geochemical transformation caused by the effects of water fluids of different composition, metasomatic and hydration-dehydration reactions, silicification and phase transitions (α-β quartz transition and partial melting).The experimental data demonstrated that the presence of fluids with different composition might lead to occurrence of different Vp values in the rock of the same type. Hence, seismic boundaries may occur in the rocks of the same chemical composition.     

铁橄榄石高温高压流变性的实验研究

通过高温高压实验研究了铁橄榄石集合体的流变性.首先,利用高精度的Paterson气体介质变形装置对铁橄榄石集合体Fe2SiO4进行了高温三轴压缩蠕变试验.变形试验条件为温度1273～1423K,围压300MPa,差应力10～250MPa,应变率10-7～10-4s-1,试件的最大变形量不超过20%.利用三维非线性拟合方法对蠕变试验数据进行分析,得到铁橄榄石集合体的微观变形机制为扩散域和位错域,扩散域的应力指数为1左右.位错蠕变域中,干燥铁橄榄石集合体的应力指数为5.4.活化能为781kJ/mol;含水铁橄榄石集合体的应力指数为3.4,活化能为516kJ/mol.实验结果表明,含水时铁橄榄石的流变强度比干燥时小一个数量级.将实验结果与铁橄榄石单晶的强度进行对比,发现铁橄榄石集合体的流变强度比铁橄榄石单晶的强度高.从而得到了铁橄榄石集合体高温高压流变性(强度)的初步试验结果.     

A model for C-O-H fluid in the Earth’s mantle

A model is presented for predicting the composition (H₂O, CO₂, CH₄, H₂, CO, O₂ and C₂H₆) in the C-O-H fluid system under high temperatures and pressures found in the Earth’s mantle. The model is based on a molecular dynamic equation of state, statistical mechanics calculations and non-stoichiometric global free-energy minimization. Although the model is not fitted to experimental data on C-O-H speciation, it does accurately reproduce these datasets and should extrapolate at least to the depths of ∼80-220 km. The model results suggest that (1) in the upper cratonic mantle, H₂O is the dominant fluid species in the C-O-H fluid system; (2) the abundance of CO₂ increases with decreasing depth, the trend of CH₄ is just the opposite; (3) the boundary between lithosphere and asthenosphere generally divides fluid systems into H₂O-CH₄+ minor species and H₂O-CO₂+ minor species, respectively; (4) it is entirely possible to generate methane and ethane and possibly other hydrocarbons under mantle conditions, confirming previously experimental results.     

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     

Study of intergranular films and interstitial phases in geomaterials using high temperature centrifuge and ultrasonic method at high pressure

Water fluids in the Earth's crust may initiate a number of mineral reactions resulting in different microstructure changes, which may appear in the form of intergranular melt films and interstitial phases. Therefore, they have an essential influence on elastic wave velocities of rocks (for example, sandstone, amphibolite, basalt). The aim of the experiment was to determine the conditions of the silicate liquid and others interstitial phases distribution in the rock intergranular space.The results obtained using the ultrasonic method at temperature up to 950 °C and under fluid pressure of 300 MPa revealed that the formation of intergranular melt films and interstitial phases network depend on chemical composition of fluids. The experiments with use of a high-temperature centrifuge at temperature 1400 °C showed that the amount of melt films, higher than 6 %, is sufficient to form a system of interconnected intergranular channels. These studies can be contributed to the petrophysical and geochemical interpretation of geophysical measurements.     

高温高压岩石流变仪的围压标定方法

高温高压岩石流变仪围压标定的主要方法为氯化盐类的部分熔融法和矿物相变法。利用氯化盐类进行压力标定时,不仅可以利用单一盐类,也可以使用多种盐类的混合物;常用的压力标定矿物相变及其适用温压范围如下:石英-柯石英,500~1200℃、2.5~3.2GPa;钠长石-硬玉+石英,600~1200℃、1.6~3.2GPa;铁橄榄石+石英-铁辉石,600~1200℃、1~1.7GPa;磷镁石-Mg3(PO4)2-Ⅱ,565~825℃、0.6~0.9GPa;方解石-文石,600~1200℃、0.5~2.5GPa。不同的标定方法具有不同的特征,文中将进行详细介绍。     

花岗岩剪切变形与矿物成分变化的高温高压实验

在构造变形过程中,流体控制成矿作用的机制是目前世界矿床界共同面临的问题之一。通过研究剪切变形过程中的力学-化学作用,理解剪切构造应力和流体在构造成岩成矿过程中的行为与作用是解决这一科学问题的关键环节。在花岗岩高温高压剪切变形实验的基础上,分析了实验变形的矿物反应特征及矿物反应引起的化学成分变化,讨论了矿物反应与变形的相互影响。实验结果表明,变形样品中斜长石、钾长石和辉石以脆性-塑性变形为主,石英和云母以塑性变形为主。同时流体与岩石的相互作用引起了矿物间的反应,其中钾长石、辉石发生水解作用最典型。实验变形整体受应变局部化控制,随着剪切变形加强,脆性破裂逐渐形成和发展为裂隙,应力不断释放,有金属元素沿裂隙充填,这些微观特征在实验样品中普遍存在,类似野外中的矿脉。本次实验为韧性剪切带的流变行为、化学行为和剪切作用过程提供了实验数据。     

松科二井高温高压随钻测温技术的应用研究

松科二井是亚洲国家组织实施的最深大陆科学钻井。松科二井完钻后38 h测井温度为241℃,创造了我国钻井工程最高井温应用记录。松科二井井内参数测试主要采用两种方法,一是综合物探测井,在下套管前进行综合测井;另一种是不影响正常钻进工作,随钻进行井下参数测试。及时掌握井下随钻温度等信息,对高温泥浆性能的调整和动力机具应用起着关键性的支撑作用。本文针对松科二井科学钻探高温难点问题展开系列研究,研制了一种存储式井下高温测试仪器。该仪器经过多轮攻关改进设计,成功应用于松科二井现场,在现场应用的最高随钻测试温度为222℃。     

矿物反应与变形关系研究——以糜棱岩高温高压实验为例

矿物反应和变形局部化在中下地壳普遍存在,两者相互影响和促进。实验研究表明,矿物反应与变形关系非常复杂。本文在糜棱岩高温高压流变实验的基础上,分析了实验变形样品中的矿物反应分布特征以及矿物反应引起的化学成分变化,讨论了矿物反应与变形的相互影响。微观结构分析表明,实验变形后的糜棱岩样品在温度800~890℃时,角闪石和黑云母出现脱水反应,生成微晶角闪石和黑云母,并伴有局部熔融。受应变局部化控制,脱水反应产物主要出现在黑云母、角闪石条带边缘。微晶和熔体的成分分析表明,不仅脱水反应形成的微晶与熔体的SiO 2含量非常低,而且黑云母周围的反应产物和熔体主要来自于黑云母的脱水,角闪石边缘的反应产物和熔体主要来自于角闪石脱水,石英、钾长石和斜长石没有参与反应与熔融。本研究中的脱水反应产物中,没有发现辉石和石榴石,这种脱水反应与文献中报道的无局部化的均匀样品在静高压和高熔融比例条件的脱水反应产物和熔体的成分有很大差别。黑云母和角闪石的局部化分布和脱水程度低,可能是造成脱水反应产物有差别的巨大原因。在本实验结果中,脱水反应对变形的影响主要体现为,脱水反应产生了细粒混合矿物相,使得在局部化的剪切带内变形机制从位错蠕变转变为扩散蠕变,导致样品出现应变弱化。另外脱水反应还引起了局部脆性破裂。变形引起晶体塑性变形,增加了位错密度和矿物细粒化,促进了晶体内部成核和黑云母与角闪石的脱水分解;差应力作用增加了局部的正应力和平均应力,增加了黑云母和角闪石能够稳定存在的压力范围,这可能是反应产物以微晶黑云母和角闪石为主,而没有转化为辉石的原因。     

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.     

高温高压条件下实验变形石英闪长岩微观结构与熔体特征研究

本文以高温高压条件下石英闪长岩流变实验样品为研究对象,利用偏光显微镜进行微观结构观察,研究了样品在实验温度压力条件下的变形机制与斜长石结构对流变强度的影响;通过透射电镜能谱与电子探针,分析了熔体分布和成分特征,讨论了角闪石脱水熔融的影响因素与脱水熔融对岩石流变的影响。结果表明,随着温度升高,岩石从脆塑性过渡域逐渐向高温位错攀移和动态重结晶为主的塑性域转化。在高温条件下,角闪石出现了脱水与部分熔融,脱水熔融的熔体分布和成分体现出非均匀与非平衡熔融的特点,空间分布上,熔体主要出现在角闪石和黑云母矿物颗粒的边缘以及角闪石和长石颗粒之间的区域内;成分分布上,熔体的成分与参与熔融的矿物成分密切相关。角闪石边缘的熔体和黑云母边缘的熔体具有低硅铝、高铁镁特征,斜长石边缘的熔体具有高硅铝、低铁镁的特征,处于角闪石和斜长石颗粒中间的熔体,其成分间于斜长石与角闪石成分之间。实验中出现的非平衡非均匀部分熔融可以解释混合岩中的浅色体与暗色体的成因,富硅熔体可以形成富硅铝的花岗质岩石,而贫硅富铁镁的熔体可以形成基性岩。角闪石的脱水熔融程度依赖于样品的封闭条件,处于封闭环境的样品,角闪石不易脱水熔融,而处于开放环境时,角闪石脱水熔融显著。拆离断层带及其附近具备这样的开放环境,有利于角闪石发生脱水熔融。实验力学数据和微观结构显示,随机分布的斜长石对岩石强度影响并不明显,但斜长石的长轴方向与最大主应力方向呈大角度相交(近90°)会显著强化岩石的强度,这意味着岩石组构与主应力方向大角度相交或呈垂直方向时,不利于岩石变形和拆离断层的形成,反之,均匀岩石或岩石组构与最大主应力方向小角度相交,有利于岩石的变形,容易发育拆离断层。     

高温周期变化与高围压作用下大理岩力学特性试验研究

为了探讨温度周期变化与高围压对大理岩变形、强度特性及破坏断裂损伤劣化的影响,采用MTS815.03电液伺服刚性岩石试验系统,选取四川凉山雅砻江大河湾锦屏二级水电站引水隧洞围岩大理岩试样分别进行不同温度变化（100～ 600 ℃）,周期次数为8次。进行高围压（60 MPa）作用下全应力应变过程三轴压缩与单轴压缩对比试验,系统分析比较了温度循环与高围压作用对大理岩应力-应变关系曲线、峰值应力、残余应力,峰值应变、残余应变以及弹性模量等的影响。试验结果表明,大理岩随着温度升高,峰值强度、残余强度、弹性模量下降,峰值应变和残余应变随之增大;在同一温度下,随着循环次数增加,其弹性模量、峰值强度、残余强度降低,温度越高,降低越明显;多次循环后,岩石的脆性变大,应力-应变曲线峰后段不再平滑,残余应变变小,其研究成果为锦屏二级水电站引水隧洞围岩稳定性分析提供理论依据。