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1.
Surface textures of quartz grains from fault gouges are examined by means of the scanning electron microscope. It is disclosed that the surface morphology of the grains is variable, but quartz grains extracted from one fault gouge sample commonly show a type of texture different from those observed on the grains from the other samples. The surface textures observed under the microscope are tentatively classified into eight types; subconchoidal, orange peel-like, fish scale-like, moss-like, moth-eaten, stalactitic, pot-hole, and coral-like textures. These textures can be classified into four groups. Arranged in the order of their apparent features, it is interpreted that the progressive corrosion of quartz grains by ground water has taken place after faulting. The change of this surface feature can assist in estimating the time elapsed since the last fault activity. 相似文献
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SHEN Junfeng YANG Weimin LIU Ting HUANG Xiao ZHENG Weijie YU Lei WANG Guoqiang 《《地质学报》英文版》2014,88(4):1131-1144
Much important information referring to fault motion （e.g., fault activities period, intensity, frequency, and even dynamic background） can be revealed by resolving fault gouge, which is the result of fault motion while extruding or grinding. The field investigation encompassed sample collecting from the Bailong River fault system of the western segment of the Qinling Orogenic Belt （QOB）; 44 samples of fault gouges were collected for quartz micro-morphology analysis. These samples were analyzed using field emission scanning electron microscopy. In addition, 14 samples were tested for thermo-luminescence dating. The results showed that most of the surface textures of quartz grains are characterized by fish scale, moss-like texture, and stalactite. However, a small amount of orange peel-like fractures and worm-hole-like shaped surface texture were observed. Moreover, a few typical conchoids or subconchoidal fractures in quartz grains can be seen. This implies that the Bailong River Fault was active repeatedly during the Quaternary period, but the main motion period is the Pleistocene. The 14 thermo-luminescence dating values showed two age groups： 343.29-184.06 ka and 92.18-13.87 ka. These study data reveal that fault movement started during the Pliocene, occurred frequently in the early-middle period of the Pleistocene, and the peak frequency of the motion was reached in the early Pleistocene. The fault motions were stopped terminated in the early Holocene. The results are significant for the natural disaster risk evaluation in the western segment of the QOB. 相似文献
3.
在分析研究前人资料的基础上,结合野外实际工作和室内研究,从三峡九湾溪断裂带内各段断层泥的特征研究分析出发,探讨了九湾溪断裂带的分段性,结果发现:九湾溪断裂带存在明显的分段性,中段和南段地震活动频度和强度大,应变强度高,断层活动以粘滑为主,其分维值在2.2～2.6之间,石英碎砾表面发育各种撞击揳入现象、线状擦痕等显微构造;北段地震活动频度和强度较小,应变强度弱,断层活动以稳滑为主,兼具粘滑,其分维值在2.4～2.8之间,石英颗粒多为磨圆球砾,其刻蚀形貌以裂而不破现象为代表;中段是九湾溪断裂带最有可能发生诱发地震的地段和我们的重点监测地段。 相似文献
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黄河公伯峡古风化花岗岩石英表面结构的工程地质研究 总被引：1，自引：0，他引：1
本文对黄河公伯峡电站古风化花岗岩中的石英表面结构进行了扫描电镜观察。其特征表明是在典型的高能化学环境下形成的,这与现代风化花岗岩石英表表面结构特征明显不同,为鉴定古风化花岗岩提供了依据。 相似文献
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准噶尔盆地南缘霍尔果斯和吐谷鲁断裂带断层泥分形特征与断裂活动关系 总被引：5，自引：1，他引：4
根据采集的天然断层泥样品 ,对准噶尔盆地南缘霍尔果斯和吐谷鲁逆断裂带中断层泥进行了显微构造、显微形貌和分形研究。研究结果表明 ,断层泥至少存在三期变形 ;同时断层泥和石英碎粒中既发育有线状擦痕、阶步等典型的粘滑活动显微构造 ,也发育有剪切滑动、定向排列等典型的蠕滑活动变形现象 ,说明了断裂活动的长期性和复杂性。断层泥的分形研究表明 ,霍尔果斯和吐谷鲁断裂带断层泥分维值分别在 2 .17～ 2 .6 3和 2 .76～ 2 .89变化 ,分维值与断层运动方式粘滑或蠕滑不存在因果关系。因此 ,断层泥分维值能否作为判别断裂活动方式值得进一步研究。 相似文献
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准噶尔盆地南缘断裂带显微构造特征与活动时代 总被引：1，自引：0，他引：1
对准噶尔盆地南缘霍尔果斯-玛纳斯-吐谷鲁逆断裂带中的断层泥和构造岩显微构造进行了研究,并对断裂带中的石膏、石英脉和断层泥进行了ESR测年。显微构造研究表明,断裂带至少经历了3期构造变形,断层泥和石英碎粒中既发育有线状擦痕、阶步等粘滑活动显微构造,也发育有剪切滑动、定向排列等蠕滑活动变形现象。ESR测年结果显示,霍尔果斯-玛纳斯-吐谷鲁逆断裂带形成于1.5Ma前,在0.4~1.0 Ma和0.08~0.12 Ma期间进行了二次再调整。断裂活动时间与青藏高原阶段性隆升的时间一致,说明准噶尔盆地南缘霍尔果斯-玛纳斯-吐谷鲁逆断裂带的形成与青藏高原的隆升过程密切相关。 相似文献
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四川汶川5.12大地震同震滑动断层泥的发现及意义 总被引：4，自引：0，他引：4
2008年汶川8.0级地震沿龙门山断裂带内的映秀—北川断裂和灌县—安县断裂产生了近300 km的同震地表破裂带。震后地质科学考察发现地表变形以逆冲为主,并伴有右旋走滑。地震地表破裂带大多沿古生代碳质泥岩、页岩和三叠系煤系地层内的滑动面出露地表,这些软弱地层为地震破裂带冲到地表提供了超低摩擦滑动带。我们发现在同震垂直和水平位错达6m左右的地表破裂带,地震的同震滑动发生在厚度约0.5~2cm 的狭窄滑动带内,以发育新鲜的灰色断层泥为特征,这些断层泥是地震断层快速滑动过程中岩石—流体相互作用的结果。 相似文献
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ESR定年：一种确定脆性断层活动年龄的方法原理与应用 总被引：16，自引：0，他引：16
在浅层低温环境中，脆性断层活动难以生成新的变质矿物，断层的准确活动年龄就难以确定。但在浅层断层活动中，往往伴生有同期生成的石英脉，对石英脉采用热活化电子自旋共振(ESR)测年，能够确定石英脉的生成年龄，从而能提供断层活动的年龄。如果断层带中发育有多期石英脉，通过测定还能提供断层多次活动的年龄。以雪峰山2条断裂带为例，使用ESR定年方法获得了202.3~60.6 Ma的地质年龄，并探讨了2条断裂带的演化与区域构造活动的关系，最后对ESR测年的可信性与使用条件进行了讨论。 相似文献
11.
Supergene nickel deposits of New Caledonia that have been formed in the Neogene by weathering of obducted ultramafic rocks are controlled by fracture development. The relationship of tropical weathering and tectonic structures, faults and tension gashes, have been investigated in order to determine whether fractures play a passive role only, as previously thought; or alternatively, if brittle tectonics was acting together with alteration. Observation of time‐relationship, textures, and mineralogy of various fracture fills and fault gouges shows that active faulting has played a prominent role not only in facilitating drainage and providing room for synkinematic crystallization of supergene nickel silicate, but also in mobilizing already formed sparse nickel ore, producing the very high grade ore nicknamed “green gold”. 相似文献
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Secondary/minor structures occurring along the main fault surfaces are important indicators for judging the kinematic characteristics of faults. However, many factors can lead to the formation of these structures, which results in the difficulty for rapid judgment and application in the fields. A series of secondary faults/fractures developed due to the movement of main faults are the most important and widespread phenomena in the scope of brittle deformation. The morphology of the main fault surfaces is various, and former researchers mainly discussed the structures on the main even fault surfaces. However, the fluctuation of fault surfaces is the intrinsic character of the faults, and the intersection between the main fault and secondary faults/fractures can produce a series of kinematic indicators on the main fault surfaces. Based on previous studies and our observations, i.e. the structural traces of the P, R, R’, T and X shears/faults along the main faults, some indicators which are rarely reported previously, are described in the paper. Furthermore, their reliabilities are also discussed, and more practical and reliable criteria are brought forward. We suggest that the simple application of congruous and incongruous steps without knowing their exact origins should be abandoned in the fields, and several types of indicators along one fault surface should be checked with each other as much as possible. Meanwhile, the origins of some other arcuate indicators on the fault surfaces are also discussed, and new models are brought forward. 相似文献
14.
T. K. Gundu Rao C. P. Rajendran George Mathew Biju John 《Journal of Earth System Science》2002,111(2):103-113
The field investigations in the epicentral area of the 1994 Wadakkancheri (Desamangalam), Kerala, earthquake (M 4.3) indicate
subtle, but clearly recognizable expressions of geologically recent fault zone, consisting of fracture sets showing brittle
displacement and a gouge zone. The fracture zone confines to the crystalline basement, and is spatially coincident with the
elongation of the isoseismals of the 1994 mainshock and a 10-km-long WNW-ESE trending topographic lineament. The preliminary
results from the electron spin resonance (ESR) dating on the quartz grains from the fault gouge indicate that the last major
faulting in this site occurred 430 ± 43 ka ago. The experiments on different grain sizes of quartz from the gouge showed consistent
decrease in age to a plateau of low values, indicating that ESR signals in finer grains were completely zeroed at the time
of faulting due to frictional heat. The results show a relatively young age for displacement on the fault that occurs within
a Precambrian shear zone. Discrete reactivated faults in such areas may be characterized by low degree of activity, but considering
the ESR age of the last significant faulting event, the structure at Desamangalam may be categorized as a potentially active
fault capable of generating moderate earthquakes, separated by very long periods of quiescence. 相似文献
15.
雪峰山安化--溆浦断裂带变形特征及ESR定年 总被引：13，自引：3，他引：10
安化—溆浦断裂是雪峰山西部一条重要的区域性断裂带。宏观上呈向NW突出的弧形 ,由数条从溆浦向南撒开的主断裂及其次级分支断层组成。显微构造、断层岩与石英脉流体包裹体均一温度 (集中在 16 0℃附近 )均显示 ,断裂带以浅层脆性变形为主 ,最深动力变质岩仅为糜棱岩化绢云母千枚岩。断层岩中石英脉ESR(电子自旋共振 )定年显示 ,断裂在燕山期 (15 6 .9～ 136 .2Ma ,119.8～ 90 .6Ma)热流体活动强烈 ;而发育在上述两个时间段内的石英脉 ,不论在野外产状、显微构造及流体包裹体均一温度上都存在明显的差异 ,由此初步推断 ,这两个时间段之间应是雪峰山中生代挤压与伸展运动的反转时期。 相似文献
16.
新疆特克斯河下游河段断层活动性研究 总被引：2，自引：0，他引：2
新疆特克斯河上拟修建的恰普其海电站和山口电站位于断裂构造发育、新活动强烈的天山地区。野外地质研究表明，工程区的5条主要断层在第四纪均有活动。对采自工程区的特克斯河断层和F_1断层上的各种断层岩样品，应用变形岩石显微构造分析法、石英颗粒表面形貌法和热释光测年法进行了综合分析测试，结果表明，早期沿断层部位发生过慢速率的韧性变形作用，后沿韧性变形带发生脆性破裂。断层主活动期在上新世末期到早更新世，断层活动时的差异应力为130MPa,以挤压为主。更新世以后，断层活动强度大大减弱，但仍有明显活动，断层最后一次较强烈活动的下限时代为晚更新世末或全新世初。为确保工程安全，在最后确定场址时应尽可能避开活断层，在工程设计上也应增加一定的安全措施。 相似文献
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拟建的新疆喀拉喀什河乌鲁瓦提水电站位于现代地壳运动十分活跃的区域。野外证据显示出，坝区的Ｆ＿（１２）断层新活动延续到晚更新世，电站附近的石门北断层在第四纪有活动。对采自坝区及附近几条断层的断层物质样品进行了变形显微构造、石英颗粒表面形貌和微结构类型、ＴＬ年龄的分析测定，结果表明，Ｆ＿（１２）最新活动的上限时间不晚于３万年，Ｆ＿（３０）和石门断层的活动持续到晚更新世，石门北断层最新的活动的上限时间约２万年。根据区域断裂的分布和应力场的情况，进行了构造模拟实验，预测出工程区在区域应力场的继续作用下，应力集中在远离坝址的部位，坝址附近不会出现新的应力集中点。总体看，所选坝址是地壳活动区中相对较稳定的地段。 相似文献
18.
石英颗粒表面结构类型以及它们和形成环境间的对应关系,国外已有初步总结[1,2,3]。对石英颗粒表面结构应用于历史环境分析,有着不同的意见[4-6]。多数研究者认为,对于松散的或未固结的沉积物(主要为第四纪的)中的石英颗粒表面结构,具有显著的环境分析意义,而对于地质年代久远、早已半固结或固结成岩的则看法不一,有的则予以否定。因为,地质年代愈老,成岩作用(包括浅变质作用)影响也就愈大。但也有些情况表明[7,8],虽已固结成岩,其物源区的搬运、沉积过程中产生的机械结构,仍然部分或大部分被保存下来,仍可以指示其环境。 相似文献
19.
Tectonic pseudotachylytes, i.e. quenched friction-induced silicate melts, record coseismic slip along faults and are mainly reported from the brittle crust in association with cataclasites. In this study, we document the occurrence of recrystallization of quartz to ultrafine-grained (grain size 1–2 μm) aggregates along microshear zones (50–150 μm thick) in the host rock adjacent to pseudotachylytes from two different faults within quartzite (Schneeberg Normal Fault Zone, Eastern Alps), and tonalite (Adamello fault, Southern Alps) in the brittle crust. The transition from the host quartz to microshear zone interior includes: (i) formation of high dislocation densities; (ii) fine (0.3–0.5 μm) polygonization to subgrains defined by disordered to well-ordered dislocation walls; (iii) development of a mosaic aggregate of dislocation-free new grains. The crystallographic preferred orientation (CPO) of quartz towards the microshear zone shows a progressive misorientation from the host grain, by subgrain rotation recrystallization, to a nearly random CPO possibly related to grain boundary sliding. These ultrafine aggregates appear to be typically associated with pseudotachylytes in nature. We refer the crystal plastic deformation of quartz accompanied by dramatic grain size refinement to the coseismic stages of fault slip due to high differential stress and temperature transients induced by frictional heating. Microshear zones localized on precursory fractures developed during the stages of earthquake rupture propagation and the very initial stages of fault slip. Thermal models indicate that the process of recrystallization, including recovery processes, occurred in a time lapse of a few tens of seconds. 相似文献
20.
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