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1.
《Journal of Structural Geology》2001,23(6-7):1167-1178
S–C fabrics similar to those found in mylonites are observed in foliated cataclastic granitic rocks from the Nojima fault zone, southwest Japan. The foliated cataclastic rocks comprise cataclasite, fault breccia, gouge, and crushing-originated pseudotachylyte. The S–C fabrics observed in these cataclastic rocks involve S-surfaces defined by shape preferred orientation of biotite fragments or aggregates of quartz and feldspar fragments, and C-and C′-surfaces defined by microshears and shear bands, respectively, where fine-grained material is concentrated. Striations on the main fault plane are oriented parallel to the cataclasite lineations. A significant microstructural difference between the foliated cataclastic rocks and S–C mylonites is the absence of dynamically recrystallized grains in the foliated cataclasites. The striations, cataclastic lineations, and the S–C fabrics in the cataclastic rocks formed from the late Tertiary to the late Holocene indicate that the Nojima fault zone has moved as a dextral strike-slip fault, with a minor reverse component since it formed. S–C fabrics in cataclastic rocks provide important information on the tectonic history and are reliable kinematic indicators of the shear sense in brittle shear zones or faults. 相似文献
2.
Christian Tueckmantel Silke Schmidt Markus Neisen Neven Georgiev Thorsten J. Nagel Nikolaus Froitzheim 《Swiss Journal of Geoscience》2008,101(1):295-310
The Rhodope Metamorphic Province represents the core of an Alpine orogen affected by strong syn- and postorogenic extension. We report evidence for multiple phases of extensional unroofing from the western border of the Rila Mountains in the lower Rila valley, SW Bulgaria. The most prominent structure is the Rila-Pastra Normal Fault (RPNF), a major extensional fault and shear zone of Eocene to Early Oligocene age. The fault zone includes, from base to top, mylonites, ultramylonites and cataclasites, indicating deformation under progressively decreasing temperature, from amphibolite-facies to low-temperature brittle deformation. It strikes E–W with a top-to-the-N-to NW-directed sense of shear. Basement rocks in the hanging wall and footwall both display amphibolite-facies conditions. The foliation of the hanging-wall gneisses, however, is discordantly cut by the fault, while the foliation of the footwall gneisses is seen to curve into parallelism with the fault when approaching it. Two ductile splays of the RPNF occur in the footwall, which are subparallel to the foliation of the surrounding gneisses and merge laterally into the mylonites of the main fault zone. The concordance between the foliation in the footwall and the RPNF suggests that deformation and cooling in the footwall occurred simultaneously with extensional shearing, while the hanging-wall gneisses had already been exhumed previously. The RPNF is associated with thick deposits of an Early Oligocene, syntectonic breccia on top of its hanging wall. Integrating our results with previous studies, we distinguish the following stages of extensional faulting: (1) Late Cretaceous NW–SE extension (Gabrov Dol Detachment), exhumation of the present day hanging wall of the RPNF; (2) Eocene to Early Oligocene NW–SE to N–S extension (RPNF); (3) Miocene to Pliocene E–W extension (Western Border Fault), formation of the Djerman Graben; (4) Holocene to recent N–S to NW–SE extension (Stob Fault), reactivating the SW part of the Western Border Fault. 相似文献
3.
S. White 《International Journal of Earth Sciences》2001,90(1):14-27
Fault rocks from the Siberia Fault Zone (SFZ) in southern New Zealand are derived from schists with varied mica contents. Regional evidence indicates that the rocks are exhumed from depths of 8-10 km and temperatures of 200-250 °C. Foliated cataclasites in a zone 5-40 m thick are accompanied by interlaced pseudotachylyte, and are cut through by a late-stage master fault and zones of random fabric cataclasite. Textures and microstructures in the foliated cataclasites reflect contemporaneous or cyclic operation of cataclastic, crystal-plastic and solution transfer deformation mechanisms, partitioned differently between different phases. The deformation regime is interpreted as a form of semi-brittle flow, facilitated by crystal-plastic deformation of phyllosilicate phases in a relatively weak interconnected matrix. Quartz and feldspar are deformed mainly by cataclasis. The presence of pseudotachylyte indicates the fault was seismically active, and non-localised semi-brittle flow was episodically punctuated by high strain-rate earthquake events. Late-stage formation of a discrete master fault probably reflects a change from semi-brittle flow to brittle faulting. The presently exposed level of the fault is thought to represent a section of the mid-crustal brittle-ductile transition in the seismogenic zone. Thus, this study provides a tangible natural example of theoretically and experimentally predicted fault rocks. 相似文献
4.
The >200 km long Moonlight Fault Zone (MFZ) in southern New Zealand was an Oligocene basin-bounding normal fault zone that reactivated in the Miocene as a high-angle reverse fault (present dip angle 65°–75°). Regional exhumation in the last c. 5 Ma has resulted in deep exposures of the MFZ that present an opportunity to study the structure and deformation processes that were active in a basin-scale reverse fault at basement depths. Syn-rift sediments are preserved only as thin fault-bound slivers. The hanging wall and footwall of the MFZ are mainly greenschist facies quartzofeldspathic schists that have a steeply-dipping (55°–75°) foliation subparallel to the main fault trace. In more fissile lithologies (e.g. greyschists), hanging-wall deformation occurred by the development of foliation-parallel breccia layers up to a few centimetres thick. Greyschists in the footwall deformed mainly by folding and formation of tabular, foliation-parallel breccias up to 1 m wide. Where the hanging-wall contains more competent lithologies (e.g. greenschist facies metabasite) it is laced with networks of pseudotachylyte that formed parallel to the host rock foliation in a damage zone extending up to 500 m from the main fault trace. The fault core contains an up to 20 m thick sequence of breccias, cataclasites and foliated cataclasites preserving evidence for the progressive development of interconnected networks of (partly authigenic) chlorite and muscovite. Deformation in the fault core occurred by cataclasis of quartz and albite, frictional sliding of chlorite and muscovite grains, and dissolution-precipitation. Combined with published friction and permeability data, our observations suggest that: 1) host rock lithology and anisotropy were the primary controls on the structure of the MFZ at basement depths and 2) high-angle reverse slip was facilitated by the low frictional strength of fault core materials. Restriction of pseudotachylyte networks to the hanging-wall of the MFZ further suggests that the wide, phyllosilicate-rich fault core acted as an efficient hydrological barrier, resulting in a relatively hydrous footwall and fault core but a relatively dry hanging-wall. 相似文献
5.
The Simav metamorphic core complex of the northern Menderes massif, western Turkey, consists of a plutonic (Tertiary) and metamorphic (Precambrian) core (footwall) separated from an allochthonous cover sequence (hanging wall) by a low-angle, ductile-to-brittle, extensional fault zone (i.e. detachment fault). The core rocks below the detachment fault are converted into mylonites with a thickness of a few hundred metres. Two main deformation events have affected the core rocks. The first deformational event (D1) was developed within the Precambrian metamorphic rocks. The second event (D2), associated with the Tertiary crustal extension, includes two distinct stages. Stage one is the formation of a variably developed ductile (mylonitic) deformation (D2d) in metamorphic and granitic core rocks under greenschist facies conditions. The majority of the mylonites in the study area have foliations that strike NNW to NNE and dip SW to SE. Stretched quartz and feldspar grains define the mineral lineation trending SW-NE direction and plunging gently to SW. The kinematic indicators indicate a top-to-NE sense of shear. Stage two formation of brittle deformation (D2b) that affected all core and cover rocks. D2b involves the development of cataclasites and high-angle normal faults. An overall top towards the north sense of shear for the ductile (mylonitic) fabrics in the core rocks is consistent with the N-S regional extension in western Turkey. 相似文献
6.
断裂带是一个宽度、长度和高度均与断距呈正比关系的三维地质体,具有典型的二分结构：即断层核和破碎带。断层核由多种类型的断层岩和后期胶结物组成,具有分选差,粘土含量高,颗粒粒径小等特征,表现为具有比围岩更低的孔渗性。破碎带同围岩相比发育大量的裂缝,裂缝的密度随着离断层核距离的增大而逐渐减小,孔渗性较高。断层岩类型取决于断移地层的岩性、成岩程度和断裂变形时期。对于同生断层而言,泥岩和不纯净的砂岩主要发生泥岩涂抹作用;纯净砂岩发生解聚作用,形成颗粒重排的变形带。中成岩阶段发生断裂变形,泥岩发生泥岩涂抹作用,不纯净的砂岩发生碎裂作用和层状硅酸盐涂抹作用,形成碎裂岩和层状硅酸盐 框架断层岩;纯净砂岩主要发生碎裂作用,形成碎裂岩。晚成岩阶段发生断裂变形,碎裂作用成为主要的变形机制,泥岩破碎形成大量断层泥,不纯净的砂岩和纯净的砂岩均形成碎裂岩,其中纯净砂岩形成的碎裂岩由于石英的压溶胶结变得更致密。因此不同成岩阶段、不同岩性形成的断层岩类型不同,泥岩涂抹的排替压力高于层状硅酸盐 框架断层岩和碎裂岩,即使都是碎裂岩,其渗透率相差7个数量级。从断裂带结构看油气运移和保存,断层垂向封闭主要靠剪切型泥岩涂抹的连续性,侧向封闭能力取决于断层岩物性,物性很高的碎裂岩自身封闭能力很差,依靠两盘岩性对接封闭油气,最小断距决定油水界面位置。物性很低的断层岩一般能封住一定高度的油气柱,其是断裂带中泥质含量的函数。断层在储盖层段变形机制差异,决定了断裂输导与封闭油气的耦合,即破碎带双向输导充注,盖层段剪切型泥岩涂抹顶部封闭,断层核遮挡成藏。 相似文献
7.
8.
Cataclasis and frictional wear are the primary bulk deformation mechanisms along steeply dipping portions of the Saltville thrust in the southern Appalachian foreland zone, U.S.A. Fault character ranges from a single discrete sliding surface with negligible gouge, to a zone of several discrete sliding surfaces or a zone (up to 0.3 m thick) of pervasive cataclasite. Marked fracturing occurs up to 20 m above the fault, whereas minimal deformation is found in the footwall rocks. Hanging wall dolomites range from crush breccias (less than 5% matrix) to ultracataclasites (with 90% matrix), although cataclasites (50–70% matrix) are predominant. Foliated cataclasites occur where dolomite is thrust over shale. Progressive development of cataclastic fabrics is due to comminution by fracturing and grinding along intersecting fractures. Continued frictional grinding results in complete disruption of the original fabric to produce cataclasite and minor ultracataclasite. Grain alignment occurs by rigid body rotation with subsequent local enhancement by pressure-solution. Microstructural relations of the fault gouge suggest periodic fluctuations in fluid pressure, where λv (ratio of fluid to overburden pressure) probably ranged between 0.45 and 1. The Saltville thrust-sheet emplacement must have occurred in a caterpillar-like fashion involving aseismic and seismic shear. Shear stresses accompanying fault motion as determined from dolomite twin lamellae are in the order of 65 mPa. 相似文献
9.
The structural location of an approximately 3-km stretch of the Catalina detachment fault zone appears to have been controlled by an ultramylonite shear zone within mylonites of the Catalina–Rincon metamorphic core complex. The Catalina detachment fault zone consists of the detachment fault surface, a 3–5 m interval of cataclasite and ultracataclasite, up to ∼50 m of chlorite breccia, and a discrete subdetachment fault. Beneath the subdetachment fault is a km-scale thickness of mylonites. Progressive ductile-to-brittle shear-zone evolution of the fault-rock stratigraphy started with mylonitization, was followed by overprinting of mylonites by chlorite brecciation, and culminated in the formation of the Catalina detachment fault and associated ultracataclasites. The detachment fault is cospatial with and subparallel to the zone of chlorite breccia. The subdetachment fault is subparallel to the interval of chlorite brecciation and to the detachment fault. The ‘plane’ of projection of the approximately 30-m thick ultramylonite shear zone within the mountain of mylonite, when followed downdip, coincides with the base of the ‘chlorite breccia’ brittle shear zone. Ultramylonite is preserved in places in the immediate lower plate of the subdetachment fault. The position and orientation of the subdetachment fault appears to have been controlled by an ultramylonite shear zone within the lower-plate mylonites. The rheological properties and orientation of this ultramylonite shear zone favored its reactivation as the brittle sole fault of the zone of chloritic brecciation. 相似文献
10.
桐柏-大别造山带剪切带阵列的构造岩研究 总被引：5，自引：0，他引：5
桐柏—大别造山带剪切带阵列经受长期的应变软化、应变局部化和变形分解作用,形成了一系列构造岩,包括糜棱岩、变晶糜棱岩、半塑性糜棱岩和面理化碎裂岩等。糜棱岩普遍具二相糜棱结构或由相连的弱相基质或层分离强相残斑或布丁所形成的IWL(Interconnected weak matrix or layers)结构。构造岩中显微构造各式各样,并具一定的组合形式和演化规律,反映了不同环境下主导变形机制的多样性及变形机制间转换的规律性。代表性剪切带岩石化学成分变异的研究表明,除流体流动外,体积亏损是造成某些组分,尤其是一些不活动组分,如钛、磷、锆、钒、钇等相对富集的主导因素,并由化学成分的变异和质量平衡计算,求出了该剪切带的体积亏损率以及流体/岩石值。较大的体积亏损和大量渗透体的存在,对剪切带的化学行为和流变行为都有着重要的影响作用。 相似文献
11.
Field investigations reveal spatial variations in fault zone width along strike-slip active faults of the Arima–Takatsuki Tectonic Line (ATTL) and the Rokko–Awaji Fault Zone (RAFZ) of southwest Japan, which together form a left-stepping geometric pattern. The fault zones are composed of damage zones dominated by fractured host rocks, non-foliated and foliated cataclasites, and a fault core zone that consists of cataclastic rocks including fault gouge and fault breccia. The fault damage zones of the ATTL are characterized by subsidiary faults and fractures that are asymmetrically developed on each side of the main fault. The width of the damage zone varies along faults developed within granitic rocks of the ATTL and RAFZ, from ∼50 to ∼1000 m. In contrast, the width of the damage zone within rhyolitic tuff on the northwestern side of the ATTL varies from ∼30 to ∼100 m. The fault core zone is generally concentrated in a narrow zone of ∼0.5–∼5 m in width, consisting mainly of pulverized cataclastic rocks that lack the primary cohesion of the host rocks, including a narrow zone of fault gouge (<0.5 m) and fault-breccia zones either side of the fault. The present results indicate that spatial variations in the width of damage zone and the asymmetric distribution of damage zones across the studied strike-slip faults are mainly caused by local concentrations in compressive stress within an overstep area between left-stepping strike-slip faults of the ATTL and RAFZ. The findings demonstrate that fault zone structures and the spatial distribution in the width of damage zone are strongly affected by the geometric patterns of strike-slip faults. 相似文献
12.
Very high strains recorded in mylonites along the Alpine Fault, New Zealand: implications for the deep structure of plate boundary faults 总被引：1，自引：0，他引：1
Oblique displacement on the Alpine Fault, which forms the principal structure along the Australian–Pacific plate boundary in South Island, New Zealand, has resulted in exhumation of a kilometre-wide mylonite zone in the hanging wall adjacent to the current brittle fault trace. The mylonites formed under amphibolite facies conditions at depths of ca. 25 km and have been uplifted during the past 5 Ma. A suite of 65–70 Ma pegmatite veins in the hanging wall Alpine schists has been progressively deformed within the mylonite zone and sheared out over a strike length of ca. 100 km. Measurements of the thickness distribution of the pegmatite veins within the non-mylonitised schists and at three localities within the progressively strained mylonites have been used to estimate strain values within the mylonites. The thicknesses approximate a log-normal distribution, with a mean value that is progressively reduced through the protomylonites, mylonites and ultramylonites. By assuming that the thickness distribution currently observed in the schists was the same for the pegmatites within the mylonites before strain, a model of deformation incorporating simple shear and simultaneous pure shear is used to strain the undeformed veins until a fit is obtained with the strained distributions. Shear strains calculated range from 12 to 22 for the protomylonites, 120 to 200 for the mylonites and 180 to 300 for the ultramylonites, corresponding to pure shear values of 1–3 in each case. These values are compatible with the strains predicted if most of the surface displacement on the fault over the past 5 Ma were accommodated within a 1–2-km-wide mylonite zone through the middle and lower crusts. The results suggest that processes such as erosional focussing of deformation and thermal weakening may cause intense strain localisation within the lower crust, with plate boundary deformation restricted to narrow zones rather than becoming increasingly distributed over a widening shear zone with depth. 相似文献
13.
沿红河断裂带(RRFZ)分布的点苍山变质核杂岩是一个不完整的变质核杂岩,它由两个特征迥异的单元组成,包括被同构造二长花岗岩侵入角闪岩相构造岩组成的下盘和绿片岩相的拆离断层带。下盘岩石包括具有高温构造组合,具有指示左行走滑剪切运动方向的L型糜棱岩或LS型糜棱岩。拆离断层带是一个上盘向E到SE伸展剪切的低温剪切带,由具有剪应变和压应变的典型S-L糜棱岩构成。低温构造岩也包括发育于下盘的几个糜棱岩化似斑状二长花岗岩侵入体。变质核杂岩与西侧覆盖未变质的中生代沉积岩并置,东部受第四纪断层作用影响为沿洱海分布的更新世-全新世沉积盆地。通过对点苍山变质核杂岩的构造研究,结合邻区变质核杂岩的地质年代学及古地磁学分析,我们认为:位于东南亚红河断裂和实皆断裂带之间的扇形区域内出现的变质核杂岩与渐新世-中新世时期区域性伸展作用有关,而伸展作用是由印支地块的差异性旋转产生的,其原因是由于约33Ma开始斜向俯冲的印度板块的顺时针旋转和回退所致。 相似文献
14.
Late Quaternary activity and dextral strike-slip movement on the Karakax Fault Zone, northwest Tibet 总被引：1，自引：0，他引：1
Field observations and interpretations of satellite images reveal that the westernmost segment of the Altyn Tagh Fault (called Karakax Fault Zone) striking WNW located in the northwestern margin of the Tibetan Plateau has distinctive geomorphic and tectonic features indicative of right-lateral strike-slip fault in the Late Quaternary. South-flowing gullies and N–S-trending ridges are systematically deflected and offset by up to ~ 1250 m, and Late Pleistocene–Holocene alluvial fans and small gullies that incise south-sloping fans record dextral offset up to ~ 150 m along the fault zone. Fault scarps developed on alluvial fans vary in height from 1 to 24 m. Riedel composite fabrics of foliated cataclastic rocks including cataclasite and fault gouge developed in the shear zone indicate a principal right-lateral shear sense with a thrust component. Based on offset Late Quaternary alluvial fans, 14C ages and composite fabrics of cataclastic fault rocks, it is inferred that the average right-lateral strike-slip rate along the Karakax Fault Zone is ~ 9 mm/a in the Late Quaternary, with a vertical component of ~ 2 mm/a, and that a M 7.5 morphogenic earthquake occurred along this fault in 1902. We suggest that right-lateral slip in the Late Quaternary along the WNW-trending Karakax Fault Zone is caused by escape tectonics that accommodate north–south shortening of the western Tibetan Plateau due to ongoing northward penetration of the Indian plate into the Eurasian plate. 相似文献
15.
Abstract The article describes the characteristics of the Yagan metamorphic core complex, especially the associated detachment fault and various extensional structures in its footwall. The age of the complex is discussed in some detail as well. The basic features of the Yagan metamorphic complex (Jurassic in age) are similar to those of the metamorphic core complex (Tertiary in age) in the Cordilleran area; they are as follows: (a) mylonitic gneisses in the footwall, (b) chloritized sheared mylonitic rocks, (c) pseudotachylites and flinty cataclasites or microbreccias, (d) unmetamorphosed or epimetamorphic rocks in the hanging wall with a layer of fault gouges or incohesive fault breccia next to the detachment fault. In contrast to its Cordilleran counterpart, however, there are many extensional faults with different styles (from dactile low-angle normal faults through brittle — ductile to brittle high — angle normal faults) in the footwall. 相似文献
16.
The article describes the characteristics of the Yagan metamorphic core complex, especially the associated detachment fault and various extensional structures in its footwall. The age of the complex is discussed in some detail as well. The basic features of the Yagan metamorphic complex (Jurassic in age) are similar to those of the metamorphic core complex (Tertiary in age) in the Cordilleran area; they are as follows: (a) mylonitic gneisses in the footwall, (b) chloritized sheared mylonitic rocks, (c) pseudotachylites and flinty cataclasites or microbreccias, (d) unmetamorphosed or epimetamorphic rocks in the hanging wall with a layer of fault gouges or incohesive fault breccia next to the detachment fault. In contrast to its Cordilleran counterpart, however, there are many extensional faults with different styles (from dactile low-angle normal faults through brittle-ductile to brittle high-angle normal faults)in the footwall. 相似文献
17.
We report the results of permeability measurements of fault gouge and tonalitic cataclasite from the fault zone of the Median Tectonic Line, Ohshika, central Japan, carried out during triaxial compression tests. The experiments revealed marked effects of deformation on the permeability of the specimens. Permeability of fault gouge decreases rapidly by about two orders of magnitude during initial loading and continues to decrease slowly during further inelastic deformation. The drop in permeability during initial loading is much smaller for cataclasite than for gouge, followed by abrupt increase upon failure, and the overall change in permeability correlates well with change in volumetric strain, i.e., initial, nearly elastic contraction followed by dilatancy upon the initiation of inelastic deformation towards specimen failure. If cemented cataclasite suffers deformation prior to or during an earthquake, a cataclasite zone may change into a conduit for fluid flow. Fault gouge zones, however, are unlikely to switch to very permeable zones upon the initiation of fault slip. Thus, overall permeability structure of a fault may change abruptly prior to or during earthquakes and during the interseismic period. Fault gouge and cataclasite have internal angles of friction of about 36° and 45°, respectively, as is typical for brittle rocks. 相似文献
18.
Microcracks in the Cretaceous Ryoke-type granite in Japan were investigated by using deep drilling core samples collected in the Mizunami Underground Research Project of the Japan Nuclear Cycle Development Institute (JNC). The granite body suffered brittle deformation associated with Tertiary thrust movement. Based on core-scale and microscopic deformation features, the drill core from a depth of 300 to 700 m is divided into four domains, i.e. (A) undeformed granite, (B) granite intruded by cataclastic seams, (C) fractured granite in the fault damage zone, and (D) foliated cataclasite at the fault center. To characterize microcrack geometries in each domain, we employed the impregnation method using a low-viscous acrylic resin doped with fluorescent agents and captured the microcrack images by confocal laser scanning microscopy (CLSM). The CLSM image in the fault damage zone revealed anisotropic development of microcrack networks related to the fault movement. Both CLSM observation and porosity measurements reveal a drastic increase of micro-pores in the foliated cataclasite, possibly caused by fragmentation, and granulation and crack sealing in the fault zone. 相似文献
19.
南雄断裂构造剥离作用及其与铀成矿的关系 总被引：4，自引：2，他引：4
南雄断裂带下盘发育规模较大，平行于断裂走向的糜棱岩带，上盘为一中新生代盆地，随着地层时代的变新，沉积中心向断层一侧迁移。本文通过对断裂下盘糜棱岩带的剖面测量，对糜校岩中Ｓ－Ｃ面理、旋转碎斑和拉伸线理等各种韧性变形组构的详细研究，根据变形组构的运动学指向，结合断裂带内脆性构造岩及盆地中正断层的发育状况和展布特征，确定南雄断裂为一规模巨大的剥离断层。对剥离断层与铀成矿的关系本文也进行了初步探讨。 相似文献