This book is a systematic guide to the recognition and. Here, sibson 1977 uses rock cohesion at the time of faulting and the presenceabsence of foliation as the defining factors for classification with fault gouge defined as an incohesive rock composed of. It is believed that the difference in the amount of heavy metals between the bed rock and the fault gouge is mainly due to the existence of goethite which is the main mineral composition in the. Several other algorithms for estimating gouge composition exist. Enlargement of the intersection in figure 2b between well px2 and the namsong fault, showing a reports of fault gouge, cataclasite, and loss of drilling mud, from drilling logs, and b proportions of fault gouge from subsequent laboratory analysis of cuttings. Determining the relative age of fault activity through. Gouge is usually classified by to characteristics, it may be classified based upon its chemical or mineralogical composition and by its particle size type. Fault gouge has no cohesion and it is normally an unconsolidated rock type, unless cementation took place at a later stage. The black gouge samples, compared to the fault breccia, have a lower d1g peak intensity ratio and higher d1g peak width ratio.
These data are important in traps where faults play an important role in the critical seal. A microphysical model for fault gouge friction applied to. Shear resistance reduction due to vibration in simulated. This page deals specifically with the deformation of polyphase fault gouges. Exxonmobil exploration company abstract we investigate the relationship between frictional strength and clay mineralogy of natural. From our result, it is clear that these two approaches yielded consistent results with regard to the relative age of the faults. Fault gouge is a tectonite a rock formed by tectonic forces with a very small grain size. As the fractal dimension dvalue of grains gradually increases. To be able to do this, a basic understanding of the mineralogy needs to be gathered from the sample e. The mineral composition of bed rock suggests that it is heavily altered by hydrothermal activity. Earthquakes are some of the most dynamic features of the earth. Its roughness is made of triangular grooves perpendicular to the. Darley hch, george rg 1988 composition and properties of drilling and completion fluids. A cataclastic rock is a type of fault rock that has been wholly or partly formed by the progressive fracturing and comminution of existing rocks, a process known as cataclasis.
If the gouge is composed of minerals such as illite, kaolinite, chlorite, or antigorite, which have. Cataclasis involves the granulation, crushing, or milling of the original rock, then rigidbody rotation and translation of mineral grains or aggregates before. We examine the finescale variations in mineralogical composition, geochemical alteration, and texture of the faultrelated rocks from the phase 3 wholerock core sampled between 3,187. Protoliths of the granitic composition are from the ryoke metamorphic belt and those of the basic schist from the sambagawa metamorphic belt. We examine the finescale variations in mineralogical composition, geochemical alteration, and texture of the fault related rocks from the phase 3 wholerock core sampled between 3,187.
We collected a clayrich fault gouge sample al211, table 1, fig. Frictional strengths of fault gouge from a creeping segment. Fault gouge from the valle mastallone, west of valle strona, yielded a kar age of 22. Fault zone dynamic processes geophysical monograph series. Chemical composition of pseudotachylyte and melting process.
Ichi uehara, kazuo mizoguchi, ichiko shimizu, keishi okazaki and koji masuda, on the transient response of serpentine antigorite gouge to stepwise changes in slip velocity under high. The fracture zone c has a 3m 10ftthick bluish gray fault gouge. A microstructural study of the fault gouge in the granite, yangbuk. Information and translations of fault gouge in the most comprehensive dictionary definitions resource on the web. As fault gouge is formed by break down of the surrounding fault blocks, the mineralogical composition of the gouge is expected to be that of the bulk rock. A note on the stressdilatancy relation for simulated fault gouge chris marone l abstracttheoretical constraints on the stressdilation relation for a deforming coulomb material require v fault gouge is a tectonite a rock formed by tectonic forces with a very small grain size.
Areas of deep sedimentary rock cover often show no surface indications of the faulting below. Geochemical and mineralogical characteristics of fault. Frictional strengths of fault gouge from a creeping. Fault gouge in siliciclastic sequences ranges from sandrich to shalerich. The results of active fault effect are on the one hand the forming of fault gouge along the. A microphysical model is developed for the steady state frictional behavior of illite. Pdf cataclasis and the generation of fault gouge researchgate. The following list outlines the procedure for quantitative fault seal analysis. It was hypothesised that the two methods would yield consistent results. Frictional properties of natural fault gouge from a low. The role of fault gouge properties on fault reactivation.
Fluidization and melting of fault gouge during seismic slip. This ratio of sandshale is the sgr or smear gouge ratio. Kar dating of synkinematic clay gouges from neoalpine faults. This work provides insight into the physical and chemical properties, structural. The bartlett springs fault bsf is a rightlateral strikeslip fault that is part of the san andreas fault system in northern california with an estimated slip rate of 7 mmyr. A fault rock without primary cohesion where less than 30% of the fragments are visible to the naked eye and the rest is finegrained and clayey. Fault sealconduit studies predict fault sealconduit behavior and potential hydrocarbon column height, based on fault morphology and gouge composition, lithology juxtapositions along faults, hydrocarbon type, and reservoir pressure how to use them. Composition, alteration, and texture of faultrelated.
These zones are fundamental geologic structures in the earths crust. The major and minorelement composition of the gouge samples is in between that of the granodiorite and the diorite compositions. Changes in texture and mineral compositions will cause differences among. A fault gouge forms in the same way as fault breccia, the latter also having larger clasts. A fault crossseals or dipseals if the sandshale ratio is low in the zone low sgr. In both cases the powder and water were mixed together for 5 min by a combination of hand and blender to form a homogeneous fault gouge material. Dating of fault gouges from the major active faults in. When fault gouge is melted, frictional resistance is governed by the viscosity of melt which depends mainly on temperature. This is a richly illustrated reference book that provides a unique, comprehensive, and uptodate survey of the rocks and structures of fault and shear zones. The particlesize distribution of a natural faultgouge has been determined over the range from 5. Many of the larger centimetresized cuttings from this depth range were mud balls.
Microstructures developed in the fault gouge zone, yangbuk. The finegrained output of faulting near the surface is the gouge, which is essentially the rock powder formed during faulting. Qualitative examinations of the fault zone at each sampling site revealed that more than one distinct gouge composition was present. The aim of this work was to compare these approaches. Here we show that gouge from the san andreas fault, california, with. Near lake pillsbury, the bsf slip rate is expressed as fault creep at a rate of 3. Shear resistance reduction due to vibration in simulated fault gouge takane hori institute for research on earth evolution, japan agency for marine. Seal behavior is dependent upon the ratio of sandshale at that point along the fault. Accurate estimation of the frictional strength of the fault gouge. Occasionally, the beds adjacent to the fault plane fold or bend as they resist slippage because of friction. Therefore, mineral mapping at a very high resolution is necessary to obtain most of the information on the composition of the fault gouge sample. Fault gouge is crushed and groundup rock produced by friction between the two sides when a fault moves. Areas of deep sedimentary rock cover often show no surface indications.
A microstructural study of the fault gouge in the granite. To test this hypothesis, triaxial sliding experiments were conducted on 15 different single. Geochemical and mineralogical characteristics of fault gouge in the. Fault sealconduit studies predict fault sealconduit behavior and potential hydrocarbon column height, based on fault morphology and gouge composition, lithology juxtapositions along faults, hydrocarbon type, and reservoir pressure. This book is essential to all practising structural and. Mechanical healing of simulated fault gouge 3 we used in our experiments a rough inner cylinder made in dural density of 2. Many of these contributions illustrate riedel shears, which develop in both experimental and natural fault gouge, in orientations similar to s, c, or c planes of higher temperature mylonites. Cataclasis involves the granulation, crushing, or milling of the original rock, then rigidbody rotation and translation of mineral grains or aggregates before lithification. Pdf processes of fault gouge evolution in hard claystones start with cataclasis that produces a. Particle size and energetics of gouge from earthquake rupture. Fault plane sections defined reservoir juxtapositions and aided visualization of potential cross fault spill points.
Printed in great britain a note on the effect of fault gouge composition on the stability of frictional sliding r. Kar dating of synkinematic clay gouges from neoalpine. The lower fractal limit occurs at a dimension of about 110. Minerals free fulltext nanoscale automated quantitative. Fault gouge graphitization as evidence of past seismic.
A note on the stressdilatancy relation for simulated. Pdf microstructural and mineral analysis on the fault. Influence of the characteristics of fault gouge on the stability of a. Pdf fault gouge evolution in highly overconsolidated claystones.
Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments over two millimeters in diameter. Implications of clay mineral composition in fault gouge. The oriented sample of fault gouge from zone a has the foliation of n59e75s, with a stretching lineation of n65e12. Microstructural and mineral analysis on the fault gouge in the. Parent material and clay gouge the composition of the fault filling is determined. Composition, alteration, and texture of faultrelated rocks. Although fault breccia and black gouge have similar d1 band position, the g band position of the black gouge has higher frequency. Bed rock consists of quartz, pyrophyllite, pyrite, illite, and topaz, but the browncolored fault gouge is composed of quartz, illite, chlorite, smectite, goethite, and cacoxenite. In addition, the g peak width ratio of the black gouge was smaller than that of the. Grain size reduction and gouge formation are found to be ubiquitous in brittle faults at all scales 1,2,3,4, and most slip along mature faults is observed to have been localized within gouge zones. Pdf microstructural and mineral analysis on the fault gouge.
The fracture zone b is partly composed of soft gouge, yellowish white in color. These tools augmented interpretation of sealnonseal character in proved reservoirs and were used to quantify fault seal risk of untested, faultdependent closures. Jan 17, 2017 microstructures developed in the fault gouge zone, yangbuk, gyeongju city, korea, were characterized with emphasis on distribution of remaining grains. This classification, initially compiled by sibson 1977 using data from spry 1969 and higgins 1971, is shown in figure 1a. This subscribes to the examination of ylagan et al. Mineralogy and geochemistry of fault gouge in pyriterich. The lower and upper fractal limits were also determined. Unfortunately, the intersection of the lamprophyre dikes with the fault surface is almost exactly parallel to the grooves and striae which presumably mark the movement direction in the veins and shear zones fig.
This multidisciplinary volume presents an overview of earthquake processes and properties including the physics of dynamic faulting, fault fabric and mechanics, physical and chemical properties of fault zones, dynamic rupture processes, and numerical modeling of fault zones during seismic rupture. Characterization of pulverized granitoids in a shallow. Microstructures developed in the fault gouge zone, yangbuk, gyeongju city, korea, were characterized with emphasis on distribution of remaining grains. Sibson 1986 studied earthquake repeat times and locations in association with breccia characteristics to outline the process of brecciation into three groups. The fully saturated fault gouges consisted of 35 g of bowland shale powder and 15 g of deionised water. We found that small variations of fault gouge composition, which insignificantly affect the ultimate fault strength, may result in significant variations of a fault slipweakening rate during sliding sufficient for significant variation of kinetic energy of the movable block and even for alteration of the slip mode from stickslip to steady. Based on xrd analysis, the fault gouges consist of quartz, feldspar and clay minerals composed of abundant illite and chlorite, with vein minerals including laumontite and pyrite. Smear gouge ratios calculated from elogs were used to estimate the composition of faultgouge materialsmore these tools augmented interpretation of sealnonseal character based on fluid contact relationships in proved reservoirs and, in addition, were used to quantify fault seal risk of untested faultdependent closures in okan. Kirby department of geosciences, the pennsylvania state university now at. Byerlee the frictional properties of fault gouge have been studied at confining pres sures to 6 kbars. The effect of mineral bond strength and adsorbed water on.
Smear gouge ratios calculated from elogs were used to estimate the composition of faultgouge materials between juxtaposed reservoirs. This is further confirmed by the isotopic signature shown by concretions close to the master fault, which suggests cementation operated by fluids with composition. Niemeijer and chris marone, the role of fault zone fabric and. Shear resistance reduction due to vibration in simulated fault gouge. The mineralogical composition of the fault gouges has been established by xrd analysis of powder samples and analysis of preferentially oriented clay minerals. Fault gouge graphitization as evidence of past seismic slip. The marked character of new gouge is abundant in clay minerals, and the content of clay minerals decreases in turn from coseismic gouge to old fault gouge, fault breccia and wall rock. The relative age of fractures can be determined through structural analyses in the field or through the detailed mineralogical xrd and chemical analyses aas method, volumetric, and gravimetric analysis of fault gouge in the laboratory. These tools augmented interpretation of sealnonseal character in proved reservoirs and were used more. The frictional properties of fault gouge have been studied at confining pressures to 6 kbars. The latest fault zone in the anko section contains cataclasite, fault breccia, and fault gouge of granitic composition, and brecciated basic schist. Powder xrd polytype analysis shows that the clay fraction contains the predominance of 1md illite polytype over 2m1 illite polytype. An even greater loss of circulation was reported, concentrated between depths of 3816 and 3840 m, during drilling of well px2, directly beneath a zone of fault gouge spanning 37903816 m figure 3.
These observations indicate that a major fault was transected cf. If the gouge is composed of strong materials such as crushed granite or quartz sand, the frictional strength is high, and violent stickslip occurs at confining pressures above approximately 1. The spaces between the large angular fragments are filled with a matrix of smaller particles and a mineral cement that binds the rock together. Fault gouge is generated by both seismic and aseismic fault slip events. It is therefore impossible to make a reliable determination of the total movement along the fault.
Smear gouge ratios calculated from elogs were used to estimate the composition of fault gouge materials between the juxtaposed reservoirs. All have established a relationship between the actual seal behavior and inferred gouge composition. Particle size and energetics of gouge from earthquake. A note on the effect of fault gouge composition on the.
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