This book is essential to all practising structural and. The effect of mineral bond strength and adsorbed water on. Jan 17, 2017 microstructures developed in the fault gouge zone, yangbuk, gyeongju city, korea, were characterized with emphasis on distribution of remaining grains. A microstructural study of the fault gouge in the granite. Fault gouge is generated by both seismic and aseismic fault slip events. The lower fractal limit occurs at a dimension of about 110. Powder xrd polytype analysis shows that the clay fraction contains the predominance of 1md illite polytype over 2m1 illite polytype.
The following list outlines the procedure for quantitative fault seal analysis. The fully saturated fault gouges consisted of 35 g of bowland shale powder and 15 g of deionised water. The aim of this work was to compare these approaches. These zones are fundamental geologic structures in the earths crust. It was hypothesised that the two methods would yield consistent results. Protoliths of the granitic composition are from the ryoke metamorphic belt and those of the basic schist from the sambagawa metamorphic belt. 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. Microstructures developed in the fault gouge zone, yangbuk, gyeongju city, korea, were characterized with emphasis on distribution of remaining grains. Geochemical and mineralogical characteristics of fault. Fault zone dynamic processes geophysical monograph series. These data are important in traps where faults play an important role in the critical seal. Implications of clay mineral composition in fault gouge. Qualitative examinations of the fault zone at each sampling site revealed that more than one distinct gouge composition was present. 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.
Its roughness is made of triangular grooves perpendicular to the. 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. Minerals free fulltext nanoscale automated quantitative. The role of fault gouge properties on fault reactivation. Accurate estimation of the frictional strength of the fault gouge. Information and translations of fault gouge in the most comprehensive dictionary definitions resource on the web. Fault gouge graphitization as evidence of past seismic slip. The spaces between the large angular fragments are filled with a matrix of smaller particles and a mineral cement that binds the rock together. 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. The major and minorelement composition of the gouge samples is in between that of the granodiorite and the diorite compositions. We collected a clayrich fault gouge sample al211, table 1, fig. These tools augmented interpretation of sealnonseal character in proved reservoirs and were used to quantify fault seal risk of untested, faultdependent closures.
Composition, alteration, and texture of faultrelated. Near lake pillsbury, the bsf slip rate is expressed as fault creep at a rate of 3. Pdf fault gouge evolution in highly overconsolidated claystones. Fault gouge has no cohesion and it is normally an unconsolidated rock type, unless cementation took place at a later stage. Particle size and energetics of gouge from earthquake. This ratio of sandshale is the sgr or smear gouge ratio. Smear gouge ratios calculated from elogs were used to estimate the composition of fault gouge materials between the juxtaposed reservoirs. The oriented sample of fault gouge from zone a has the foliation of n59e75s, with a stretching lineation of n65e12. Fault gouge in siliciclastic sequences ranges from sandrich to shalerich. Influence of the characteristics of fault gouge on the stability of a. 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 mineral composition of bed rock suggests that it is heavily altered by hydrothermal activity. Fault gouge from the valle mastallone, west of valle strona, yielded a kar age of 22.
When fault gouge is melted, frictional resistance is governed by the viscosity of melt which depends mainly on temperature. 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. Microstructural and mineral analysis on the fault gouge in the. As the fractal dimension dvalue of grains gradually increases.
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. Areas of deep sedimentary rock cover often show no surface indications. 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. 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.
Fault plane sections defined reservoir juxtapositions and aided visualization of potential cross fault spill points. Recent studies suggest that the tendency of many fault gouge minerals to take on adsorbed or interlayer water may strongly influence their frictional strength. The lower and upper fractal limits were also determined. The results of active fault effect are on the one hand the forming of fault gouge along the. Byerlee the frictional properties of fault gouge have been studied at confining pres sures to 6 kbars. Shear resistance reduction due to vibration in simulated fault gouge takane hori institute for research on earth evolution, japan agency for marine. 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. Geochemical and mineralogical characteristics of fault gouge in the. This page deals specifically with the deformation of polyphase fault gouges. This work provides insight into the physical and chemical properties, structural. Exxonmobil exploration company abstract we investigate the relationship between frictional strength and clay mineralogy of natural. Frictional properties of natural fault gouge from a low. 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 is a tectonite a rock formed by tectonic forces with a very small grain size. 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 effect of fault gouge composition on the. Shear resistance reduction due to vibration in simulated. Seal behavior is dependent upon the ratio of sandshale at that point along the fault. The finegrained output of faulting near the surface is the gouge, which is essentially the rock powder formed during faulting. Dating of fault gouges from the major active faults in. A microstructural study of the fault gouge in the granite, yangbuk.
Frictional strengths of fault gouge from a creeping. A fault crossseals or dipseals if the sandshale ratio is low in the zone low sgr. Kirby department of geosciences, the pennsylvania state university now at. 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. The fracture zone b is partly composed of soft gouge, yellowish white in color. Kar dating of synkinematic clay gouges from neoalpine.
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. Many of the larger centimetresized cuttings from this depth range were mud balls. 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. Pdf cataclasis and the generation of fault gouge researchgate. 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. Pdf microstructural and mineral analysis on the fault. A fault gouge forms in the same way as fault breccia, the latter also having larger clasts. Changes in texture and mineral compositions will cause differences among. This classification, initially compiled by sibson 1977 using data from spry 1969 and higgins 1971, is shown in figure 1a.
A microphysical model for fault gouge friction applied to. Therefore, mineral mapping at a very high resolution is necessary to obtain most of the information on the composition of the fault gouge sample. Areas of deep sedimentary rock cover often show no surface indications of the faulting below. 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. From our result, it is clear that these two approaches yielded consistent results with regard to the relative age of the faults. This is further confirmed by the isotopic signature shown by concretions close to the master fault, which suggests cementation operated by fluids with composition. 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. Frictional strengths of fault gouge from a creeping segment. Sibson 1986 studied earthquake repeat times and locations in association with breccia characteristics to outline the process of brecciation into three groups. To test this hypothesis, triaxial sliding experiments were conducted on 15 different single. 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. 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.
Cataclasis involves the granulation, crushing, or milling of the original rock, then rigidbody rotation and translation of mineral grains or aggregates before. Breccia is a term most often used for clastic sedimentary rocks that are composed of large angular fragments over two millimeters in diameter. Microstructures developed in the fault gouge zone, yangbuk. Kar dating of synkinematic clay gouges from neoalpine faults. These observations indicate that a major fault was transected cf. 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. Occasionally, the beds adjacent to the fault plane fold or bend as they resist slippage because of friction. The fracture zone c has a 3m 10ftthick bluish gray fault gouge. Shear resistance reduction due to vibration in simulated fault gouge.
Although fault breccia and black gouge have similar d1 band position, the g band position of the black gouge has higher frequency. Determining the relative age of fault activity through. Here we show that gouge from the san andreas fault, california, with. Several other algorithms for estimating gouge composition exist. Smear gouge ratios calculated from elogs were used to estimate the composition of faultgouge materials between juxtaposed reservoirs. All have established a relationship between the actual seal behavior and inferred gouge composition. The black gouge samples, compared to the fault breccia, have a lower d1g peak intensity ratio and higher d1g peak width ratio. Niemeijer and chris marone, the role of fault zone fabric and. Pdf processes of fault gouge evolution in hard claystones start with cataclasis that produces a. 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 particlesize distribution of a natural faultgouge has been determined over the range from 5. Pdf microstructural and mineral analysis on the fault gouge. These tools augmented interpretation of sealnonseal character in proved reservoirs and were used more. Characterization of pulverized granitoids in a shallow. Mechanical healing of simulated fault gouge 3 we used in our experiments a rough inner cylinder made in dural density of 2. If the gouge is composed of minerals such as illite, kaolinite, chlorite, or antigorite, which have. In addition, the g peak width ratio of the black gouge was smaller than that of the. To be able to do this, a basic understanding of the mineralogy needs to be gathered from the sample e.
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. 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. Parent material and clay gouge the composition of the fault filling is determined. Particle size and energetics of gouge from earthquake rupture. The latest fault zone in the anko section contains cataclasite, fault breccia, and fault gouge of granitic composition, and brecciated basic schist. Chemical composition of pseudotachylyte and melting process. Earthquakes are some of the most dynamic features of the earth. The frictional properties of fault gouge have been studied at confining pressures to 6 kbars. The frictional strength of a rock in this case fault gouge is described by a coefficient of friction. 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. Cataclasis involves the granulation, crushing, or milling of the original rock, then rigidbody rotation and translation of mineral grains or aggregates before lithification. Mineralogy and geochemistry of fault gouge in pyriterich. This book is a systematic guide to the recognition and. This subscribes to the examination of ylagan et al.
Fluidization and melting of fault gouge during seismic slip. Composition, alteration, and texture of faultrelated rocks. 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. Printed in great britain a note on the effect of fault gouge composition on the stability of frictional sliding r. It is therefore impossible to make a reliable determination of the total movement along the fault. Darley hch, george rg 1988 composition and properties of drilling and completion fluids. Fault gouge graphitization as evidence of past seismic. A note on the stressdilatancy relation for simulated. A microphysical model is developed for the steady state frictional behavior of illite.
Fault gouge is crushed and groundup rock produced by friction between the two sides when a fault moves. This is governed by byerlees law in the following equation. 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. 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. Fault seal analysis of okan and meren fields, nigeria. The mineralogical composition of the fault gouges has been established by xrd analysis of powder samples and analysis of preferentially oriented clay minerals. The brittle fault zones in crystalline bedrocks are, in general, consists of a major slip planes fault core bounded by a zone of fractured rocks damage zone caine et al.
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