Complexities of rock fracture and rock friction from deformation of Westerly granite

A series of rock friction experiments has been carried out to study the complexities in rock fracture and rock friction. Intact Westerly granite samples were loaded to shear failure in a laboratory polyaxial loading apparatus. The resultant fractured samples were reloaded to cause frictional sliding. Both polyaxial loading (₁ > ₂ > ₃ > 0) and equal confining condition (₁ > ₂ = ₃ > 0) were used. The deformation processes were monitored by macroscopic axial stress-strain, optical holography, and ultrasonic velocity measurements.Intense localized deformation along the fracture occurred very early in the loading of fractured samples. Contacts on the fracture surfaces continuously broke during loading. No acoustic velocity anomaly was observed for the fractured sample, in contrast to a 25% drop in the velocity before the failure of the corresponding intact sample. The current study and previous research suggest that the deformation localization is an important process in governing the instability of rock friction. Instability analysis of rock friction needs to include not only the deformation processes along the sliding surfaces, but also those adjacent to the fractures such as the localized deformation along the fractures observed in the current study. The instability analysis of rock friction with rate- and state-dependent friction laws does not specifically include the deformation localization adjacent to the faults and thus ignores an important class of instability as described byRudnicki (1977).A dependence of frictional strengths on the stress components normal to the sliding and in the plane of the fracture surface was observed. This dependence can be understood by considering the loading of the irregular fracture surface under polyaxial loading conditions. This observation requires the friction laws in the macroscopic scale to be modified for those cases where the three principal stresses (₁, ₂, and ₃) are significantly different.     

Microstructures and deformation mechanisms of experimentally deformed gabbro

The natural gabbro samples were deformed at temperature ranging from 700 to 1150 °C with strain rate steps of 1 9 10-4, 2.5 9 10-5, 6.3 9 10-6s-1. The mechanical data show that sample experiences gradual transition from semi-brittle flow to plastic flow, corresponding to a systematically decreasing stress exponent n with the increasing temperature ranging from 16.5 to 4.1(He et al.Sci China(D) 46(7):730–742, 2003). We investigate microstructures and deformation mechanisms of experimentally deformed gabbro under transmission electron microscope in this study. For low temperature of 700 °C to950 °C, the deformation is mainly accommodated with dislocation glide and mechanical twinning, corresponding to stress exponent lager than 5, which means semi-brittle deformation. Whereas with higher temperature up to 1000°C–1150 °C, the deformation is accommodated mainly with dislocation glide and climb corresponding to stress exponent of 4.1, which means plastic deformation. Evidence of dislocation climb has been found as dislocation walls in plagioclase. The observed slip system in plagioclase is(001)1/2[110] and that in clinopyroxene are(100)[001] and(010)[001]. The(010)[001] slip system in clinopyroxene is newly found in this work. Melt was found at temperature of 950 °C–1050 °C. The melt glass distributed both in melt thin film between two grain boundaries and melt tubules of triangular along three grain boundaries at temperature of 950 °C–1000 °C. The melt triangular interconnected to the melt film at temperature of1050 °C–1150 °C, where the melt chemical composition differentiated into iron-rich dark dots and silicate-rich matrix.     

Age and generation of Fogang granite batholith and Wushi diorite-hornblende gabbro body

Fogang granitic batholith, the largest Late Mesozoic batholith in the Nanling region, has an exposure area of ca. 6000 km2. Wushi diorite-hornblende gabbro body is situated at the northeast part of the ba- tholith. Both the granitic batholith main body and the diorite-hornblende gabbro body belong to high-K calc alkaline series. Compared with the granitic main body, the Wushi body has lower Si (49%―55%), higher Fe, Mg, Ca, lower REE, less depletion of Eu, Ba, P, Ti, and obvious depletion of Zr, Hf. Zircon LA-ICP-MS dating and the mineral-whole rock isochron dating reveal that Fogang granitic main body and Wushi body were generated simultaneously at ca. 160 Ma. The Fogang granitic main body has high (87Sr/86Sr)i ratios (0.70871―0.71570) and low εNd(t) values (?5.11―?8.93), suggesting the origins of the granitic rocks from crustal materials. Their Nd two-stage model ages range from 1.37―1.68 Ga. The Sr and Nd isotopic compositions and the Nd model ages of the granitic rocks may suggest that the giant Fogang granitic main body was generated from a heterogeneous source, with participation of mantle component. Wushi diorite-hornblende gabbro is an unusual intermediate-basic magmatic rock series, with high (87Sr/86Sr)i ratios (0.71256―0.71318) and low εNd(t) values (?7.32―?7.92), which was possibly formed through mixing between the mantle-derived juvenile basaltic magma and the magma produced by the dehydration melting of lower crustal basaltic rocks.     

不同温度条件下花岗岩变形破坏及声发射时序特征

在４００ＭＰａ范围及２０～８５０℃的温度范围内,研究了花岗岩的变形破坏及声发射时序特征。结果表明,随环境温度的升高,岩石强度降低,破坏方式从突发式失稳逐渐转变为渐进式,破坏类型亦从生剪切破裂逐渐转变为半脆性、半延性和延性破坏。声发射数量随温度升高迅速减少,出现ＡＥ活动及ＡＥ活动显增强的差应力水平亦有所提高。温度不太高时（２５０℃以下）,随破坏强度的临近,破前ＡＥ紧计频度指数增长,其指数增长速率随温     

大陆碰撞过程中的多地体变形模式

几乎所有的大陆碰撞造山带都含有多个增生地体,它们是大陆造山带的重要组成部分.前人对地体拼贴过程及其相应地质记录都做过详细探讨,但对后期大陆持续汇聚过程中的多地体之间的变形行为及拆离模式目前研究得仍较为薄弱.为此,我们以"两地体"结构为代表,通过系统的动力学模型试验,来探讨多地体流变结构及其几何参数对大陆碰撞动力学过程的影响.模型结果显示,大陆碰撞过程中的地体变形行为主要受控于靠近主碰撞带的地体流变强度(确切来说是地壳流变强度,下同)及其几何宽度,而与远离主碰撞带的地体流变和几何属性关系较弱.同时,模型结果也揭示出大陆碰撞造山带中地体之间的相互俯冲仅发生在靠近主碰撞带一侧地体较宽的情况下,且总是弱地体向相对强的地体之下俯冲.该研究成果不仅对喜马拉雅—青藏高原造山带中地体变形演化给予重要的动力学启示,也对含有多地体结构的碰撞造山带的动力学演化研究提供一定的理论支撑.     

Miocene emplacement and deformation of the Konga Shan granite (Xianshui He fault zone, west Sichuan, China): Geodynamic implications

The presently active sinistral Xianshui He strike-slip fault (XSH) is a lithospheric scale strike-slip fault in the eastern Himalaya. In the study area this fault affects the eastern edge of the Konga Shan granitic massif, where it has caused both brittle and ductile deformation. A RbSr isochron and Nd and Pb isotope study of three samples, and a UPb zircon study of a single sample, were completed on the granite.

UPb data indicate a granite emplacement age of 12.8 ± 1.4 Ma. The RbSr isochrons show that the granite emplacement and the deformational event were synchronous, at around 12-10 Ma (minimum age for deformation). The Nd and Pb isotope compositions of whole rocks and K-feldspars indicate the involvement of Proterozoic continental crust, which is confirmed by UPb systematics indicating inherited zircons.

Sinistral faulting along the XSH began at the latest at 12 Ma and marks the extrusion toward the east of the West Sichuan and South China blocks, following their extrusion along the Red River fault zone between 50 and 21 Ma.     

岩石变形破裂过程中电荷感应信号的检测

设计了采用非接触方式、高放大倍数、高效率的电荷传感器,并给出了电荷传感器的设计原理和技术指标。利用研制的电荷传感器对岩石变形破裂过程中产生的电荷感应信号进行了检测试验。结果表明,岩石在变形破裂过程中会产生电荷感应信号,并能够被研制的电荷传感器检测到;电荷感应信号是瞬时脉冲的;随着加载应力水平的增加,电荷感应信号强度增强,在峰值应力前,电荷感应信号强度达到最大值;在破裂面接收到的电荷感应信号较强,主破裂面接收到的信号最强,因而电荷的产生和岩石的破裂有很大的关系。作为正在探索的检测岩石破坏过程的手段之一,电荷感应方法应是一种很具潜力的方法,值得深入研究。     

Palaeomagnetic determination of transgressive and regressive movements during the quaternary in the Black Sea

Summary The piston core with a length of 60·8 m from the Samotino-east structure of the Bulgarian Black Sea shelf (about 28·2 E, 42·8 N) is studied palaeomagnetically. 129 levels from the interval 2·5–60·2 m, generally represented by clays and aleurolitic muds, were sampled. The age of the sediments of this core was determined by correlation with another core, situated very close to the one concerned (3 km), whose fauna is known very well. Its age is Eopleistocene (Gurinian deposits), Upper Pleistocene (Neweuxinian deposits) and Holocene.Standard palaeomagnetic methods are used to determine the components of NRM and the main carriers of primary magnetization (AF and thermal demagnetization of NRM, thermodemagnetization of J_rs and J_s).It is assumed that the basic carrier of NRM is coarse-grained ferrimagnetic monoclinic pyrrhotite (T_B of 300 °C) or partly oxidized pyrite (T_B of 400 °C).It is shown that the pyrite concentration varies along the depth of the section. This palaeomagnetically established variation corresponds very well to the data on the transgressive and regressive phases in the Black Sea basin. For the Gurinian deposits these phases are connected with the Danube and Güns glacials, the D-G interglacial and G1-G2 interstadial. No such correlation has so far been mentioned in the literature to our knowledge.Presented at 2nd conference on New Trends in Geomagnetism, Castle of Bechyn, Czechoslovakia, September 24–29, 1990.     

煤岩变形破坏电磁辐射记忆效应的力电耦合规律

理论分析了煤岩变形破坏过程中电磁辐射脉冲数与损伤之间的关系,探讨了煤岩变形破坏电磁辐射产生机制及电磁辐射记忆效应的力电耦合规律,建立了等围压三轴应力状态下含瓦斯煤岩变形破坏电磁辐射记忆效应的力电耦合模型,实验测定并分析了单轴压缩状况下含瓦斯煤岩变形破坏电磁辐射记忆效应的力电耦合规律.结果表明,含瓦斯煤岩变形破坏电磁辐射记忆效应力电耦合模型很好地反映了煤岩变形破坏电磁辐射记忆效应特征规律和微观损伤机理.     

Estimating the influence of filtering during the operation of the Pauzhetka and Mutnovskii high-temperature geothermal fields,Kamchatka, Russia

It is shown that the productive reservoir received considerable quantities of meteoric water during the operation of the Pauzhetka geothermal field (1960–2007), which amounted to 30% of the total with-drawal of heat carrier. This led to cooling of the productive reservoir and reduced steam extraction. Modeling the operation process with the infiltration zones sealed shows that steam extraction can be enhanced by 23.2%. Multi-option modeling for the operation of the Dachnyi site of the Mutnovskii geothermal field shows that the most-likely scenario is infiltration of meteoric water with a discharge of about 60 kg/s into the productive reservoir from above. These results are consistent with the decrease in the steam concentration during the first 4 years of operation.     

岩石受压破裂的ULF和LF电磁前兆信号

实验观测到了4类岩性、18块样品在单轴压力下直至破裂发生全过程中的ULF和LF电磁前兆信号。这些不同频率的信号是零散出现的，其形态为一组组脉冲，宽度为4ms～16ms，幅度为0．1mV～1．4mV。实验发现具同一谐振频率的天线收到的信号频次与其相对于裂缝的位置和方位有关。结果还表明，电磁前兆信号的频度与岩样强度有关，抗压强度高的岩样电磁前兆信号多。微破裂可能产生了偶电层，在破裂过程中向外辐射，产生了LF频段的磁信号，ULF磁信号则主要由压磁效应产生。     

Spatio-temporal characteristics of acoustic emission during the deformation of rock samples with compressional and extensional en-echelon faults

Introduction By the experimental techniques of acoustic emission (AE) and surface strain observation, a lot of achievements on the study of deformation and fracture process of samples with en-echelon faults has been obtained (Bomblakis, 1973; LIU, et al, 1986; DU, et al, 1989; LI, et al, 1989; ZHANG, FANG, 1989; ZHANG, LI, 1989; MA, et al, 1995a, b; LI, et al, 2000). However, there still exist many problems. For example, most of discussion on the spatio-temporal evolution of microf…     

Study on the pattern and mode of vertical crustal deformation during the seismogenic process of intraplate strong earthquakes

Ｓｔｕｄｙｏｎｔｈｅｐａｔｔｅｒｎａｎｄｍｏｄｅｏｆｖｅｒｔｉｃａｌｃｒｕｓｔａｌｄｅｆｏｒｍａｔｉｏｎｄｕｒｉｎｇｔｈｅｓｅｉｓｍｏｇｅｎｉｃｐｒｏｃｅｓｓｏｆｉｎｔｒａｐｌａｔｅｓｔｒｏｎｇｅａｒｔｈｑｕａｋｅｓ杨国华，桂昆长，巩曰沐，杨春花，韩...     

煤岩变形破坏电磁辐射记忆效应实验研究

实验研究了原煤、型煤单轴压缩电磁辐射记忆效应特征、记忆内容及变化规律,探讨并分析了煤岩电磁辐射记忆效应机理.结果表明,煤岩变形破坏电磁辐射具有记忆先期最大应力、纵向应变、横向应变和体应变的能力,最直接的记忆内容是先期受到的应力、纵向应变和横向应变;当先期施加的应力水平大于70%～80%时,电磁辐射记忆能力迅速减弱,甚至根本失去记忆能力;煤岩损伤破坏过程的不可逆决定了电磁辐射过程的不可逆,电磁辐射过程的不可逆是煤岩变形破坏电磁辐射记忆效应的直接原因.煤岩电磁辐射记忆效应理论在地应力测试、巷道围岩不同应力区范围的确定及煤岩动力灾害预测等方面具有广阔的应用前景.     

Spatial and temporal characteristics of acoustic emission activity during deformation of rock samples with inhomogeneous fault under biaxial compression

The spatial and temporal distributions of acoustic emission （AE） during the deformation of samples containing an inhomogeneous fault have been studied under biaxial compression. The results show that the fault strength and the duration from loading to failure increase and the failure mode changes from abrupt instability to gradual failure with increase of lateral stress σ2. The pre-setting fault and its heterogeneity play an important role in controlling AE spatial distribution during the deformation. The basic pattern of AE spatial distribution is controlled by the pre-setting fault, especially the parts with inhomogeneous strength and the strong segment, and the localization of fracturing starts from the positions with inhomogeneous strength, With increase of σ5, the dense AE distribution area spreads from the positions with inhomogeneous strength to the whole strong segment gradually. AE temporal sequence is significantly affected by σ2. The fault shows abrupt instability in final failure, which occurs on a background of ＂enhancement-quiescence＂ in microfracturing activity at lower σ2. At higher σ5, the fault shows gradual failure, and AE occurrence rate increases continuously and AER increase exponentially before and after the failure, The effect of σ2 on b-value is also remarkable, b-value shows precursory decrease in the weakening stage when fault behavior is abrupt instability, but it shows balanced change when fault behavior is gradual failure,     

Aseismic negative dislocation model and deformation analysis of crustal horizontal movement during 1999~2001 in the northeast margin of Qinghai-Xizang block

Introduction So small is the hypocenter area of strong earthquake, but its formation is controlled by time-space evolution of present-day crustal movement in wider-range area, and related to motion and deformation of active blocks and their boundary faults. Aseismic negative dislocation model presented by Matsuura, et al (1986) is that, the relative motion between blocks driven by present-day crustal movement may be partly locked at the block …     

Aseismic negative dislocation model and deformation analysis of crustal horizontal movement during 1999——2001 in the northeast margin of Qinghai-Xizang block

Through numerical simulation for GPS data, aseism/c negative dislocation model for crustal horizontal movement during 1999-2001 in the northeast margin of Qinghai-Xizang block is presented, combined with the spatial distri-bution of apparent strain field in this area, the characteristics of motion and deformation of active blocks and their boundary faults, together with the place and intensity of strain accumulation are analyzed. It is shown that: a) 9 active blocks appeared totally clockwise motion from eastward by north to eastward by south. Obvious sinistral strike-slip and NE-NEE relative compressive motion between the blocks separated by Qilianshan-Haiyuan fault zone was discovered; b) 20 fault segments (most of them showed compression) locked the relative motion between blocks to varying degrees, among the total, the mid-east segment of Qilianshan fault (containing the place where it meets Riyueshan-Lajishan fault) and the place where it meets Haiyuan fault and Zhuanglanghe fault, more favored accumulation of strain. Moreover, the region where Riyueshan-Lajishan fault meets north boundary of Qaidam block may have strain accumulation to some degree, c) Obtained magnitude of block velocities and locking of their boundaries were less than relevant results for observation in the period of 1993-1999.     

人类活动影响下的云南阳宗海近百年有机碳与黑炭湖泊沉积记录

利用我国云南省昆明市阳宗海湖心40 cm沉积岩芯,分析总氮(TN)、有机碳(TOC)、黑炭(BC)含量和黑炭同位素(δ~(13)CBC)等多环境指标,采用~(137)Cs和~(210)Pb定年方法建立沉积岩芯年代序列,探讨阳宗海近百年来TOC以及BC沉积变化特征及其对区域人类活动的响应.结果表明:(1)阳宗海沉积岩芯中TN、TOC和BC含量分别为0.76~5.07、4.95~42.65和0.69~11.16 mg/g;δ~(13)CBC值为-31.03‰~-25.45‰,均值为-27.18‰;(2)TN、TOC含量自下而上同步增长,TOC/TN摩尔比值在1994年左右增长到最大值后逐渐减小,反映了流域内人为活动导致的外源性TOC增加,阳宗海水体逐渐富营养化;(3)阳宗海沉积岩芯中BC含量及其同位素的时间序列变化,反映了当地能源结构的变化,工业源和居民消费源成为阳宗海BC的主要来源,BC与人口数量和能耗间呈显著相关.