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《吉林大学学报(地球科学版)》2015,(Z1)
<正>下地壳的力学性质一直以来都没研究清楚。近年来圣安德烈斯断层在下地壳深度上发现的震颤,使下地壳的力学性质引起了更多的关注,也已开展了相关的实验研究。以往的实验表明,从辉长岩中分离出来的辉石和斜长石以及二者的混合物在有效正应力为200 MPa的实验条件下,均在下地壳温度范围表现为速度弱化,即可以产生不稳定滑动。为了探究上述斜长石、辉石及其混合物的速度弱化是否具有代表性,考察其在更低压力下是否表现出相同的性质,本研究对斜长石断层泥在低正应力条件下的摩擦滑动性质进行 相似文献
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为了探讨含白云石断层的摩擦滑动稳定性,我们使用白云石断层泥开展了水热条件下的摩擦滑动实验研究。实验的有效正应力为60MPa,孔隙流体压力为20MPa,温度范围为25～150℃。实验过程中为了得到白云石摩擦强度系数的速度依赖性,我们将轴向加载速率在5μm/s、1μm/s、0.2μm/s和0.04μm/s之间进行切换。在本研究的温度和压力条件下,我们发现白云石断层泥表现出低温的稳定的速度强化的摩擦滑动行为向高温不稳定黏滑的转变。白云石摩擦强度系数为0.65～0.7,没有表现出显著的温度依赖性。在25～50℃的温度范围,白云石表现出稳定的速度强化的摩擦滑动行为。当温度升高到100℃时,在0.2～0.04μm/s加载速率范围内表现出速度弱化并伴随着黏滑现象,而在1～5μm/s的加载速率下表现出显著的速度强化的摩擦滑动行为。白云石的速率依赖性参数（a-b）值随温度和有效正压力的升高和加载速率的降低表现出有稳定的滑动向不稳定地震成核的转变趋势。因此,对油气储层而言,当其上覆的白云岩岩层被断层穿过时,其在较低的温度范围内（<100℃）也具备了发生不稳定地震成核的条件,需要防范其发生诱发地震的风... 相似文献
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东天山黄山岩带因发育众多镁铁质-超镁铁质岩体和岩浆铜镍硫化物矿床而备受地质学者关注。四顶黑山岩体位于该岩带最东端,具有层状岩体特征;岩石类型有单辉橄榄岩、橄榄辉石岩、橄榄苏长辉长岩、橄榄辉长岩、辉石角闪岩、辉长岩、角闪辉长岩、闪长岩,主要造岩矿物为贵橄榄石、古铜辉石、透辉石、普通角闪石和斜长石,岩体分异较好,蚀变较发育。通过矿物显微结构特征观察以及计算得出:四顶黑山岩体中橄榄石最先结晶,其开始结晶温度大约在1419℃左右;古铜辉石和透辉石在橄榄石之后开始结晶,结晶温度分别在1100℃左右和900～1100℃之间,两矿物相在岩石中可以共存。岩体中橄榄岩相、苏长岩相发育,以及贵橄榄石+古铜辉石的矿物组合特征,表明岩体具有形成铜镍(铂)矿床的有利条件。 相似文献
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在采用天然基性岩样品进行的流变实验中,存在因实验温度低而样品处于半脆性变形域与因实验温度高而样品颗粒边界出现熔体的矛盾。文献中给出的流变参数中,应力指数n的可靠性高,具有良好的重复性,激活能Q在一定范围内具有重复性,而系数A重复性差。采用6种样品进行流变实验。结果表明,矿物成分对岩石流变的影响比根据端员组分确定的双组分和多组分岩石流变物理模型要复杂得多。由斜长石、单斜辉石和角闪石组成的样品中,当斜长石和单斜辉石含量接近,而角闪石含量低于10%,斜长石和单斜辉石控制了岩石的流变;如果样品中有超过10%的角闪石参与流变,角闪石在变形中所起作用非常显著。由斜长石、石英和角闪石组成的样品,当石英含量小于10%而斜长石和角闪石含量接近时,斜长石和角闪石控制了岩石的流变;当斜长石含量达到70%时,样品变形更接近长石特性;如果石英含量超过20%时,石英在变形中起到主要作用。选择与基性麻粒岩中主要矿物成分接近的天然辉长岩(辉绿岩),或者从天然基性麻粒岩中挑选出主要矿物,通过热压合成人工样品,进行高温流变实验是研究基性麻粒岩流变的最有效途径。 相似文献
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本文在高温高压条件下,开展了辉长岩矿物反应与部分熔融实验,利用偏光显微镜与扫描电镜对实验样品微观结构观察,研究实验中的新生矿物与熔体的分布;通过电子探针分析熔体成分特征。实验结果表明,在低压(300MPa)条件下,静压和塑性变形实验样品中,单斜辉石以固体反应方式生成橄榄石,在高压(1300MPa)塑性实验中所有实验样品都没有发现新生矿物颗粒,这与相图中低压条件下斜长石与橄榄石稳定共存,而高压下斜长石-辉石稳定共存相吻合。高压塑性变形条件下,单斜辉石和黑云母首先发生部分熔融,随着温度增高,斜长石逐渐参与熔融,熔体呈薄膜状分布在矿物颗粒边界,熔体成分依赖于参与熔融的矿物成分,表明出现的熔体为非平衡熔融结果。 相似文献
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桂北龙胜地区位于江南造山带西段,本文利用电子探针对桂北龙胜地区金车辉长岩单斜辉石和斜长石进行了详细的矿物学和矿物化学研究,研究表明单斜辉石的成分为Wo27~28En47~57Fs15~22,属于普通辉石,斜长石的成分为An1.35~9.05Ab90.34~97.45Or0.36~1.05,为钠长石。单斜辉石温压估算结果显示,其形成温度为1 250~1 350℃,该温度基本与软流圈地幔温度(1 280~1 350℃)相当,其形成压力为1.31~2.25 GPa,对应深度为43.2~74.3 km。单斜辉石成分特征指示金车辉长岩为板内拉斑玄武岩,结合区域地质特征,推测金车辉长岩是裂谷构造背景下软流圈地幔物质上涌并发生减压熔融的产物。 相似文献
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对桂东北鹰扬关地区新发现的罗家山辉长岩开展年代学、矿物学和矿物化学研究,可进一步约束区域构造背景.罗家山辉长岩的主要矿物为单斜辉石(Cpx)和斜长石(Pl).单斜辉石具有高铁铝、低钙钠钛的特征,其成分为Wo27～31En36～47Fs21～32,属于普通辉石;斜长石具有高硅铝钠、低钙钾的特点,其成分为An0～3Ab96～100Or0～2,属于钠长石.根据单斜辉石的化学成分判定罗家山辉长岩的母岩浆属于Si不饱和的亚碱性拉斑玄武岩系列.单斜辉石温压估算结果表明,罗家山辉长岩的形成温度介于1 282～1 292℃,平均值1 287℃;形成压力介于1.53～2.37 GPa,平均值2.02 GPa;对应深度介于50.49～78.21 km,平均值66.80 km.LA-ICP-MS锆石U-Pb年龄表明罗家山辉长岩形成于(768.9±6.8) Ma.单斜辉石的化学成分特征表明罗家山辉长岩属于典型的板内拉斑玄武岩.结合区域构造演化特征,推断罗家山辉长岩起源于地幔物质上... 相似文献
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出露于西南天山特克斯县东南的小哈拉军山辉长岩体主要由角闪辉长岩和含磁铁矿辉长岩组成。角闪辉长岩主要由单斜辉石、角闪石和斜长石组成;含磁铁矿辉长岩主要由斜长石和磁铁矿组成。这两类岩石都含少量方解石。这些方解石均呈独立矿物出现,且与长石、单斜辉石或黑云母平衡共生。这些方解石是原生碳酸盐矿物（不是后期热液蚀变的产物）。两类岩石属于钙碱性系列,富集轻稀土元素,亏损重稀土元素,轻重稀土之间的分异比较明显,但不显示Eu异常。辉长岩相对富集大离子亲石元素而亏损高场强元素。岩石学和地球化学研究表明,小哈拉军山辉长岩是碳酸盐化地幔极低程度部分熔融的产物,斜长石堆晶过程对岩浆演化起重要作用。 相似文献
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This paper experimentally explores the frictional sliding behavior of two simulated gouges:one,a series of quartz–smectite mixtures,and the other,powdered natural rocks,aiming to evaluate and codify the effect of mineralogy on gouge dilation and frictional strength,stability,and healing.Specifically,velocity-stepping and slide-hold-slide experiments were performed in a double direct shear configuration to analyze frictional constitutive parameters at room temperature,under normal stresses of 10,20,and 40 MPa.Gouge dilation was measured based on the applied step-wise changes in shear velocity.The frictional response of the quartz–smectite mixtures and powdered natural rocks are affected by their phyllosilicate content.Frictional strength and healing rates decrease with increasing phyllosilicate content,and at 20 wt.%a transition from velocity-weakening to velocity-strengthening behavior was noted.For both suites of gouges,dilation is positively correlated with frictional strength and healing rates,and negatively correlated with frictional stability.Changes in the permeability of gouge-filled faults were estimated from changes in mean porosity,indexed through measured magnitudes of gouge dilation.This combined analysis implies that the reactivation of caprock faults filled with phyllosilicaterich gouges may have a strong influence on permeability evolution in caprock faults. 相似文献
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Frictional sliding of gabbro gouge under hydrothermal conditions 总被引：12，自引：0，他引：12
We investigated the frictional sliding behaviour of gabbro gouge under hydrothermal conditions. Experiments were performed on 1-mm-thick gabbro gouge sandwiched between country rock pieces (with gouge inclined 35° to the sample axis) in a triaxial testing system with argon gas as the confining medium. In the first series, experiments were conducted under effective normal stresses of 200 MPa and 300 MPa respectively, with pore pressure of 10 MPa. For temperature over 400 °C, pore pressure of 30 MPa was also applied to implement supercritical water conditions. At temperatures up to 615 °C, slip rate steps ranging from 0.0488 μm/s to 1.22 μm/s were applied to obtain the rate dependence of friction.At 200 MPa effective normal stress and a pore pressure of 10 MPa, the steady state rate dependence a–b shows velocity-weakening behaviour for temperatures between 200 and 310 °C. The higher temperature limit for velocity-weakening behaviour to occur extends up to 510 °C under supercritical water conditions with a pore pressure of 30 MPa. For the limited sliding distance in our experiments, only velocity-strengthening behaviour occurred at 300 MPa effective normal stress. Considering the limited displacement (< 3.5 mm), velocity-weakening behaviour may not be excluded in the high effective normal stress case for temperature below 510 °C.The coefficient of friction shows an increasing trend with increasing temperature in the low temperature range. The cut-off temperatures for the increasing trend are 250 °C and 440 °C, respectively for the 200 MPa and 300 MPa effective normal stress cases. Above the cut-off temperatures, the coefficient of friction at 1.83 mm permanent displacement varies around an average of 0.73, which is identical to the average for the oven-dried case [He, C., Yao, W., Wang, Z., Zhou, Y., 2006. Strength and stability of frictional sliding of gabbro gouge at elevated temperatures. Tectonophysics 427, 217–229, doi:10.1016/j.tecto.2006.05.023]. Together with the small value of rate dependence (a–b < 0.0073) for the whole temperature range, these results indicate the absence of fluid-assisted creep.With the result of our experiments as a constraint on strength of frictional sliding, comparison between converted strength for strike–slip faults and creep strength of gabbro-like rocks implies fracturing and faulting behaviours in the lower crust of a cool area (Zhangbei) in North China. 相似文献
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断裂岩的岩石磁学研究可以揭示地震断裂作用的物理和化学环境,对于探讨地震断裂作用机制具有重要作用。本文在断裂岩岩石磁学最新文献的基础上,结合笔者及所在研究团队在龙门山断裂带获得的研究成果,综述了断裂岩的岩石磁学研究进展。大量研究发现断层泥和假玄武玻璃通常具有磁化率值或剩磁强度异常特征。顺磁性矿物在摩擦热或流体作用下形成新的铁磁性矿物是断层泥和假玄武玻璃高磁化率值或高剩磁强度的主要原因;地震断裂摩擦熔融作用中形成的单质铁是假玄武玻璃中高磁化率值或高剩磁强度异常的另一个重要原因。蠕滑断裂和出露于浅地表的断裂带中可见一些具有低磁化率值异常的断层泥,原因可能是流体作用或断裂带未经历高温摩擦热。断裂岩的岩石磁学研究为地震断裂带的应力应变、形成温度、摩擦热效应、流体作用、形成深度和氧化还原特征等提供了重要信息,可用于分析地震断裂的孕震和发震环境。综合岩石磁学测试和微米至纳米尺度的超显微学研究,并辅助地震断裂岩的摩擦实验、高温热模拟实验等研究可以更好地获得断裂岩的岩石磁学信息。 相似文献
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探究断层泥力学行为是研究断裂带工程地质效应的基础,以延安神道沟断裂带断层泥为对象,借助颗粒分析、X射线衍射等微观测试手段研究了3种颜色断层泥的组构特征,并通过环剪试验分析了不同含水率条件下重塑断层泥的力学行为。研究结果表明:单峰型粒径曲线的断层泥级配明显优于双峰型,石英、云母和长石为主要的非黏土矿物,黏土矿物则以伊利石和高岭石为主,赤铁矿与绿泥石的相对含量是造成断层泥颜色差异的主要原因;受含水率和粗颗粒含量的影响,断层泥应变软化特征显著,应变软化随着含水率增大呈现先增强后减弱的变化规律,当含水率小于塑限含水率时,应变软化特征则随着粗颗粒含量升高而趋弱;内摩擦角是影响应变软化特征的主要力学指标,峰值内摩擦角和残余内摩擦角均与含水率呈负相关;矿物含量影响内摩擦角的变化,在5%和10%含水率条件下,内摩擦角随非黏土矿物含量的升高而增大。 相似文献
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Neoformed minerals in shallow fault rocks are increasingly recognized as key to the behavior of faults in the elasto-frictional regime, but neither the conditions nor the processes which wall-rock is transformed into clay minerals are well understood. Yet, understanding of these mineral transformations is required to predict the mechanical and seismogenic behavior of faults. We therefore present a systematic study of clay gouge mineralogy from 30 outcrops of 17 low-angle normal faults (LANF's) in the American Cordillera to demonstrate the range and type of clay transformations in natural fault gouges. The sampled faults juxtapose a wide and representative range of wall rock types, including sedimentary, metamorphic and igneous rocks under shallow-crustal conditions. Clay mineral transformations were observed in all but one of 28 faults; one fault contains only mechanically derived clay-rich gouge, which formed entirely by cataclasis.Clay mineral transformations observed in gouges show four general patterns: 1) growth of authigenic 1Md illite, either by transformation of fragmental 2M1 illite or muscovite, or growth after the dissolution of K-feldspar. Illitization of fragmental illite–smectite is observed in LANF gouges, but is less common than reported from faults with sedimentary wall rocks; 2) ‘retrograde diagenesis’ of an early mechanically derived chlorite-rich gouge to authigenic chlorite–smectite and saponite (Mg-rich tri-octahedral smectite); 3) reaction of mechanically derived chlorite-rich gouges with Mg-rich fluids at low temperatures (50–150 °C) to produce localized lenses of one of two assemblages: sepiolite + saponite + talc + lizardite or palygorskite +/− chlorite +/− quartz; and 4) growth of authigenic di-octahedral smectite from alteration of acidic volcanic wall rocks. These transformation groups are consistent with patterns observed in fault rocks elsewhere. The main controls for the type of neoformed clay in gouge appear to be wall-rock chemistry and fluid chemistry, and temperatures in the range of 60–180 °C. 相似文献
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We compare frictional strengths in the temperature range 25–250 °C of fault gouge from SAFOD (CDZ and SDZ) with quartzofeldspathic wall rocks typical of the central creeping section of the San Andreas Fault (Great Valley sequence and Franciscan Complex). The Great Valley and Franciscan samples have coefficients of friction, μ > 0.35 at all experimental conditions. Strength is unchanged between 25° and 150 °C, but μ increases at higher temperatures, exceeding 0.50 at 250 °C. Both samples are velocity strengthening at room temperature but show velocity-weakening behavior beginning at 150 °C and stick-slip motion at 250 °C. These rocks, therefore, have the potential for unstable seismic slip at depth. The CDZ gouge, with a high saponite content, is weak (μ = 0.09–0.17) and velocity strengthening in all experiments, and μ decreases at temperatures above 150 °C. Behavior of the SDZ is intermediate between the CDZ and wall rocks: μ < 0.2 and does not vary with temperature. Although saponite is probably not stable at depths greater than ∼3 km, substitution of the frictionally similar minerals talc and Mg-rich chlorite for saponite at higher temperatures could potentially extend the range of low strength and stable slip down to the base of the seismogenic zone. 相似文献
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The mechanical properties and microstructures of mixed kaolinite/ quartz fault gouge have been studied by means of triaxial tests, wherein a 1 mm thickness of fault gouge was sheared between rigid, sintered alumina sliders. Test conditions ranged up to 200 MPa confining pressure, 175 MPa pore water pressure and temperatures to 600°C. Constant displacement rate tests were carried out at 5×10-4 mm s-1, and the stress relaxation technique was used to access a wide range of lower displacement rates down to 10-10 mm s-1. The effects of different ratios of clay: quartz were studied, and some experiments were cafried out using crushed Tennessee sandstone gouge and pre-faulted cylinders of Tennessee sandstone. Deformation-induced microstructures were studied by optical, scanning and transmission electron microscopy, and mineral chemistry changes were identified using EDS analysis in the STEM. The most important factor determining the strength of these gouges is effective confining pressure, and the effective stress law was obeyed at all test conditions. Increasing the proportion of quartz in the gouge slightly increases the strength, as does increase of temperature. Under all test conditions the gouges deformed by strain-hardening stable sliding. At 2 mm displacement the friction coefficient is similar to that for rock and rock sliding (μ= 0.85). Over wide ranges of strain-rate and temperature the strength of these gouges is little affected if the effective pressure is high, but strength drops rapidly with decreasing strain-rate if effective pressure is low (or if pore water pressure is high). Reloading of the gouge after stress relaxation at high temperatures demonstrated hardening arising from hydrothermal cementation during stress relaxation, which led to sudden rupture of the cemented gouge. This phenomenon may be responsible for cyclic rupture of natural faults. New mineral phases were produced in these experiments only at 600°C. At 400°C, anticipated production of pyrophyllite from kaolinite plus quartz was not found, but recrystallization of kaolinite is believed to have occurred and evidence of healing of cracks in quartz was seen. Microstructural studies revealed the ubiquitous development of P and R1 foliations and other features, which are identical to those found in natural clay-bearing fault zones. Microstructural evolution is associated with the strain-hardening, and apparent hardening is strongly associated with the stress path during loading. 相似文献
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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. 相似文献
19.
胶东海阳所堆积辉长岩的变质反应结构、石榴石形成及P—T演化 总被引：5，自引：0，他引：5
海阳所堆积辉长岩由橄长岩、橄榄辉长岩和辉长岩组成。在橄长岩和橄榄辉长岩中发育有典型的变质反应结构：主要为橄榄石与斜长石之间形成由斜方辉石、尖晶石、角闪石和石榴石等矿物组成的多期次次变边，并有三个不同世代变质矿物，早期Cpx＋Opx＋Spl，中期Amp，晚期Grt；期次是钛铁矿与斜长石之间形成石榴石次变边，相对比较简单，只有一个世代变质矿物，为Grt＋Amp＋Rut或Grt＋Rut岩中石榴石是通过斜长石与角闪石或斜长石与钛铁矿之间的变质反应形成的，虽为峰值变质作用的产物，但变质反应的期次及类型不同导致了所形成石榴石的温度和压力有所不同。堆积辉长岩形成演化的温压计算表明，堆积辉长岩在经过近等压降温的岩浆作用之后的变质作用早期，仍为近等压降温，而晚期则表现为近等温升压。这一特殊的P－T演化可能反映了堆积辉长冷侵位与深俯冲特征。 相似文献
20.
The frictional properties of anhydrite-dolomite fault gouges, and the effects of CO2 upon them, are of key importance in assessing the risks associated with CO2 storage in reservoir formations capped by anhydrite-dolomite sequences, and in understanding seismicity occurring in such formations (such as the Italian Apennines). Therefore, we performed velocity-stepping direct-shear experiments on simulated dolomite, anhydrite and 50:50 anhydrite/dolomite gouges, at representative in-situ conditions (120 °C and σne = 25 MPa). They were conducted under vacuum, or else using water or CO2-saturated water as pore fluid (Pf = 15 MPa). Friction coefficients varied between 0.55 and 0.7. All dry samples exhibited velocity-weakening behavior, whereas all wet samples exhibited velocity-strengthening behavior, without or with CO2. This is consistent with trends previously reported for such gouges. A compilation of literature data shows that the transition from velocity-strengthening to velocity-weakening occurs in these materials between 80 and 120 °C when dry, and between 100 and 150 °C when wet. This implies little seismogenic potential for wet dolomite, anhydrite and mixed gouges under CO2 storage conditions at 2–4 km depth. Seismic slip in the Italian Apennines at depths of ∼6 km and beyond may be explained by the velocity-weakening behavior expected in anhydrite and especially dolomite at temperatures above 150 °C. 相似文献