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A cataclastic rock mass is a poor type of engineering geological rock mass. The determination of the shear failure characteristics and shear strengths of cataclastic rock masses can provide key basis for the design and construction of infrastructure. Physical model samples of a sandstone cataclastic rock mass were first produced by a combination of three-dimensional (3D) printing technology and manual pouring. Shear tests were conducted with respect to the shear stresses parallel to the trace line plane and perpendicular to the trace line plane of the cataclastic rock mass model. Based on an extensive analysis of the shear failure characteristic, shear stress evolution characteristic curve and shear strength. When the shear stress was parallel to the trace line plane, and when the rock block that was cut and confined by the trace line exhibited a significant tip, the end stress concentration effect of the cataclastic rock mass was more significant during the shear process with the anisotropy of the rock block increased. In addition, the shapes of the rock blocks that were confined and cut by the joints were the main influencing factors of the strength of the cataclastic rock mass. When the shear stress was perpendicular to the trace line plane, the structure of the rock wall was the main influencing factor of the deformation and failure process of the shear failure plane and the shear strength. The physical and mechanical properties of the shear failure plane of the cataclastic rock mass were found to be closely related to the joint–rock wall system characteristics of the cataclastic rock mass. Therefore, when determining the shear strength of cataclastic rock mass, the shape and combination form of the rock block, shear direction, and structural failure characteristics of the rock wall should be comprehensively considered during the shear process. [ABSTRACT FROM AUTHOR]

Arranged from oldest to youngest, the main granitic rock units exposed in Khour Abalea are metagabbros, cataclastic rocks, ophiolitic melange, granitic rocks, pegmatite and lamprophyre dykes. The presence of radioactivity associated with the heavy bearing minerals in construction materials—like granite—increased interest in the extraction process. As it turns out, granitic rocks play an important economic part in the examination of an area's surroundings. The radionuclide content is measured by using an NaI (Tl)-detector. In the mineralized pegmatites, U (326 to 2667 ppm), Th (562 to 4010 ppm), RaeU (495 to 1544 ppm) and K (1.38 to 9.12%) ranged considerably with an average of 1700 ppm, 2881.86 ppm, 1171.82 ppm and 5.04%, respectively. Relationships among radioelements clarify that radioactive mineralization in the studied pegmatites is magmatic and hydrothermal. A positive equilibrium condition confirms uranium addition to the studied rocks. This study determined 226Ra, 232Th and 40K activity concentrations in pegmatites samples and assessed the radiological risks associated with these rocks. The activity concentrations of 226Ra (13,176 ± 4394 Bq kg−1), 232Th (11,883 ± 5644 Bq kg−1) and 40K (1573 ± 607 Bq kg−1) in pegmatites samples (P) are greater than the global average. The high activity of the mineralized pegmatite is mainly attributed to the presence of uranium mineral (autunite), uranophane, kasolite and carnotite, thorium minerals (thorite, thorianite and uranothorite) as well as accessories minerals—such as zircon and monazite. To assess the dangerous effects of pegmatites in the studied area, various radiological hazard factors (external, internal hazard indices, radium equivalent activity and annual effective dose) are estimated. The investigated samples almost surpassed the recommended allowable thresholds for all of the environmental factors. [ABSTRACT FROM AUTHOR]

In hard cataclastic surrounding rock with high geostress, the rock monomer strength is high and the rock is broken, and tunnel excavation in it is apt to cause large deformation, collapsing, and breaking, causing initial support crack and even intruding of the initial support deformation. The characteristics of the support system under different support parameters and shapes are analyzed, and the reasonable support section shape and support parameters are determined. The results showed that (1) under the condition of high geostress and hard cataclastic surrounding rock, the initial support deformation is large, the horizontal convergence is much larger than the settlement of arch, and the deformation duration is relatively short; (2) the distribution of pressure and stress in initial support are very uneven on the cross-section and greatly affected by the construction process; (3) in the case of large horizontal tectonic stress, the use of large curvature side wall support is beneficial to improve the quality of support and control the deformation of the structure, especially to improve the stress of concrete; (4) the closure time of the supporting system greatly influences the stress state and deformation, so it is necessary to shorten the length of the lower bench and the distance of the invert as possible so as to close the support as early as possible; (5) different location of the tunnel surrounding rock stress distribution is very uneven, the measured value is much larger than calculated value in level III based on the specification of surrounding rock; (6) under high strength and ground stress, the initial supporting stress of steel frame increases rapidly, and the measured stress is larger. This indicates that the steel frame structure bears heavy early load. Therefore, the stiffness of the steel frame should be as large as possible to meet the loading requirements. [ABSTRACT FROM AUTHOR]

Hydrosphere interactions and alteration of the terrestrial crust likely played a critical role in shaping Earth's surface, and in promoting prebiotic reactions leading to life, before 4.03 Ga (the Hadean Eon). The identity of aqueously altered material strongly depends on lithospheric cycling of abundant and water-soluble elements such as Si and O. However, direct constraints that define the character of Hadean sedimentary material are absent because samples from this earliest eon are limited to detrital zircons (ZrSiO4). Here we show that concurrent measurements of Si and O isotope ratios in Phanerozoic and detrital pre-3.0 Ga zircon constrain the composition of aqueously altered precursors incorporated into their source melts. Phanerozoic zircon from (S)edimentary-type rocks contain heterogeneous δ18O and δ30Si values consistent with assimilation of metapelitic material, distinct from the isotopic character of zircon from (I)gneous- and (A)norogenic-type rocks. The δ18O values of detrital Archean zircons are heterogeneous, although yield Si isotope compositions like mantle-derived zircon. Hadean crystals yield elevated δ18O values (vs. mantle zircon) and δ30Si values span almost the entire range observed for Phanerozoic samples. Coupled Si and O isotope data represent a constraint on Hadean weathering and sedimentary input into felsic melts including remelting of amphibolites possibly of basaltic origin, and fractional addition of chemical sediments, such as cherts and/or banded iron formations (BIFs) into source melts. That such sedimentary deposits were extensive enough to change the chemical signature of intracrustal melts suggests they may have been a suitable niche for (pre)biotic chemistry as early as 4.1 Ga. [ABSTRACT FROM AUTHOR]

The expansion of engineering and development of porous materials for the bio-adsorbents synthesis from agro-waste-derived as superior efficient extractors is a significant economic and environmental breakthrough. Here, a novel spongy mesoporous hybrid silica (SMS-L) was successfully prepared from wheat straw by developed dissolution/precipitation methodology. This manuscript aims to extract/preconcentrate 232Th isotope from Egyptian cataclastic rock (ECR) using SMS and SMS-L bio-adsorbents. The proposed bio-adsorbents/extractors provide high adsorption capacity toward the 232Th isotope ions depending on the pH value of the extraction process. The optimum conditions of leaching (batch procedure), adsorption and elution (batch and permanent-bed columnar procedures) were investigated through a series of practical experiments. The physical parameters like isotherm, kinetic, and thermodynamics were studied. The SMS and SMS-L are considered promising bio-adsorbents for the adsorption/trapping of 232Th isotope from real leach solutions of ECR. These characteristic features may attribute to (i) the recycling and management of sustainable wheat straw wastes, (ii) the low-cost and eco-friendly, (iii) superior adsorption capacity of 232Th isotope, (iv) selective-trapping of 232Th isotope ions among other competitive ions such as Cr3+, Pb2+, Sr2+, Zn2+, Zr4+, Ba2+, Cu2+, Ni2+, V3+ and REEs, and (v) the structural stability of SMS and SMS-L bio-adsorbents even after 10 adsorption-desorption recycles without marked reduction in the Th(IV)-extraction efficacy. This report offers a foundation for additional advancement in clean energy applications. [Display omitted] • Agricultural wheat straw was used to fabricate spongy mesoporous hybrid silica (SMS-L). • SMS-L offered selective thorium (Th) ions recovery adsorbent. • SMS-L bio-adsorbent extract 232Th isotope from Egyptian cataclastic rock (ECR). • The multiple reuse/cycles of SMS-L confirmed its stability and successful design. • ∼87% of Th isotope can be extracted selectively at pH 4 using SMS-L bio-adsorbents. [ABSTRACT FROM AUTHOR]

Kinematic compatibility of the western and eastern limbs of the Makarwal Anticline has been studied in the Shinawah and its adjoining area of Takhti-e-Nasrati, District Karak, KPK to understand the propagated structures and general structural model of the area. The study area is tectonically active and observed the deposition of post Pleistocene gravel deposits. In the Shinawah Nala, even younger gravel deposits are present indicating recent to sub-recent tectonic activity. Moreover, the channel avulsion of different nalas in Kurram River also reveals the existence of younger active deformations. Standard procedure has been adopted for the calculation of joint density and their other attitude data. For this purpose, the circle inventory and rectangular method has been espoused. The circle inventory method is valuable where highest numbers of fracture sets are exposed. The obtained data through this could be used for the establishment of their frequency diagrams and statistical density calculations. The shear zones that generally cut across the strata are typical cataclastic strike slip in character showing distinct asymmetric kinematic indicators of redial assemblages (Marwar, 1989). It is observed regionally, where the shear zones cut across each other; evolve a composite geometry of the conjugate joint patterns viewing mesoscopic displacements. Tensional joint sets of orthogonal symmetry are well developed. The pattern of these joint sets is observed systematic in nature and may have evolved in response to the forced folding deformational and uplifting phase of the Makarwal Anticline. This fusion of joints and conjugate fractures is properly penetrated on the strata of Dhok Pathan Formation. The general structural trend of the area is north-south. The younger joints are dipping toward east and crosscutting the older joint sets developed on the eastern limb of Makarwal Anticline. This frontal faulted limb of the Makarwal Anticline i s highly de formdand eroded w h i l e exposing t h e older formations and splays of Surghar Thrust dipping towards west. Thus, we interpret that the origin of the shear zones in the studied area is dynamically related with the neo tectonic of the Makarwal Anticline, while tensional joints are episodically related with the formation and uplifting of the Makarwal Anticline. The synchronous relationship of tensional joints and shear zones further suggests that Makarwal Anticline could be developed as a result of inversion tectonic as positive flower structure under transtensional regime. [ABSTRACT FROM AUTHOR]

The Alpine nappe stack in the Penninic-Austroalpine boundary zone in the Rätikon (Austria) contains a 4×1 km tectonic sliver of meta-diorite, known as the Schwarzhorn Amphibolite. It was deformed and metamorphosed in the amphibolite facies and is unconformably overlain by unmetamorphic Lower Triassic sandstone, indicating pre-Triassic metamorphism. Cataclastic deformation and brecciation of the amphibolite is related to normal faulting and block tilting during Jurassic rifting. Zircon dating of the Schwarzhorn Amphibolite using LA-ICP-MS gave a U-Pb age of 529+9/--8 Ma, interpreted as the crystallization age of the protolith. Geochemical characteristics indicate formation of the magmatic protolith in a supra-subduction zone setting. The Cambrian protolith age identifies the Schwarzhorn Amphibolite as a pre-Variscan element within the Austroalpine basement. Similar calc-alkaline igneous rocks of Late Neoproterozoic to Early Cambrian age are found in the Upper Austroalpine Silvretta Nappe nearby and in several other Variscan basement units of the Alps, interpreted to have formed in a peri-Gondwanan active-margin or island-arc setting. [ABSTRACT FROM AUTHOR]

Shatter cones are one of the most widely recognized pieces of evidence for meteorite impact events on Earth, but the process responsible for their formation is still debated. Evidence of melting on shatter cone surfaces has been rarely reported in the literature from terrestrial impact craters but has been recently observed in impact experiments. Although several models for shatter cones formation have been proposed, so far, no one can explain all the observed features. Shatter cones' from the Vista Alegre impact structure, Brazil, formed in fine-grained basalt of the Jurassic-Cretaceous Serra Geral Formation (Paraná large igneous province). A continuous quenched melt film, consisting of a crystalline phase, mica, and amorphous material, decorates the striated surface. Ultracataclasites, containing subrounded pyroxene clasts in an ultrafine-grained matrix, occur subparallel to the striated surface. Several techniques were applied to characterize the crystalline phase in the melt, including Raman spectroscopy and transmission electron microscopy. Results are not consistent with any known mineral, but they do suggest a possible rare or new type of clinopyroxene. This peculiar evidence of melting and cataclasis in relation with shatter cone surfaces is interpreted as the result of tensile fracturing at the tip of a fast propagating shock-induced rupture, which led to the formation of shatter cones at the tail of the shock front, likely during the early stage of the impact events. [ABSTRACT FROM AUTHOR]

The structural planes play an important role in rock mass slope stability. In this paper, a series of triaxial tests on the rock mass samples with different dip angles, plane numbers and plane spacing of structural surfaces were carried out to study the effect of the combination characteristics of the rock structural plane on rock mass mechanic parameters. Based on the test results and the combination characteristics of the field structural plane, the rock mechanics parameters for the spillway lock chamber slope of the Liyuan hydroelectric station were forecast. The stability of the slope was rationally evaluated based on the forecasted rock mass mechanical parameters. Finally, the safety factor was obtained based on the shear strength reduction method. [ABSTRACT FROM AUTHOR]

Mg-Al spinel is rare in lunar rocks (Apollo and meteorite collections), and occurs mostly in troctolites and troctolitic cataclastites. Recently, a new lunar lithology, rich in spinel and plagioclase, and lacking abundant olivine and pyroxene, was recognized in visible to near-infrared (VNIR) reflectance spectra by the Moon Mineralogy Mapper (M3) instrument on the Chandrayaan-1 spacecraft at the Moscoviense basin. These outcrop-scale areas are inferred to contain 20-30%Mg-Al spinel. Possible explanations for the petrogenesis of spinel-bearing and spinel-rich lithology(s) range from low-pressure near-surface crystallization to a deep-seated origin in the lower lunar crust or upper mantle. Here, we describe 1-bar crystallization experiments conducted on rock compositions rich in olivine and plagioclase that crystallize spinel. This would be equivalent to impact-melting, which is moderately common among lunar plutonic rocks and granulites. To explore possible precursor materials and the maximum amount of spinel that could be crystallized, a lunar troctolitic composition similar to Apollo pink spinel troctolite 65785, and a composition similar to ALHA81005 as analog to the source region of this meteorite have been chosen. The crystallization experiments on the composition of AHLA 81005 did not yield any spinel; experiments on the composition similar to Apollo 65785 crystallized a maximum of ∼8 wt%spinel, much less than the suggested 20-30%spinel of the new lithology detected by M3. However, our VNIR spectral reflectance analyses of the experimental run products indicate that the spinel composition of the experimental run products not only appears to be similar to the composition of the spinel lithology detected by M3 (characteristics of the spinel absorption), but also that the modal abundances of coexisting phases (e.g., mafic glass) influence the spectral reflectance properties. Thus, the spinel-rich deposits detected by M3 might not be as spinel-rich as previously thought and could contain as little as 4-5 wt%spinel. However, the effect of space weathering on spinel is unknown and could significantly weaken its 2 μm absorptions. If this occurs, weathered lunar rocks could contain more spinel than a comparison with our unweathered experimental charges would suggest. [ABSTRACT FROM AUTHOR]

Abstract: In most rock mechanical testing devices, the texture developed during deformation is only observed after the failure, and the detailed mapping of cracks and pore structure evolution, just before or after rupture, remains speculative. Computerized X-ray tomography (CT X-ray) offers a way to observe ‘in vivo’ some characteristics of a tested sample in the course of its deformation. Therefore we developed an X-ray transparent tri-axial cell that was included in a medical purpose X-ray scanner with a volumetric resolution of the order of 1mm3. This technique is described and applied to a porous calcarenite, which is regularly scanned for porosity evolution during mechanical testing. The experiment is performed at low confining pressure (2–10MPa). During testing, an axial load is applied until failure and is then progressively decreased. In these experiments, the peak stress is preceded by phase of diffuse dilatancy. After failure localization, the axial stress is unloaded until the stress reaches isotropy. During this unloading phase, the previous diffuse dilatancy is lost due to an elastic relaxation. Then, the stress is completely relaxed. At this moment the dilatancy increases again and the residual dilatancy is larger than that reached at the peak stress. When observed “post mortem” at microscopic scale, the dilatant structures are comprised of cataclastic deformation bands and cracks in some larger crystals. [Copyright &y& Elsevier]

Multistage veinlet cataclastic rocks, composed of aphanitic veins typical of pseudotachylyte and unconsolidated fault gouge, and sediment veins composed of alluvial deposits are widely developed within a fault shear zone (<5 m wide) as simple veins, breccias, and complex networks along the active Shimotsuburai fault, central-southern segment of the Itoigawa-Shizuoka Tectonic Line active fault system (ISTL-AFS), central Japan. Early veins are generally fractured and overprinted by younger veins, indicating that vein-forming events occurred repeatedly within the same fault shear zone. Microstructurally, both the pseudotachylyte and fault gouge veins are characterized by a superfine- to fine-grained matrix and angular-subangular fragments ranging in size from submicron scale to several centimeters. Powder X-ray diffraction patterns show that the fault veins and injection veins of fault gouge and pseudotachylyte are characterized by crystalline materials composed mainly of quartz and feldspar, similar to the granitic cataclasite host. Based on the meso- and microstructural features of veinlet cataclastic rocks and the results of powder X-ray diffraction analyses, we conclude that (i) the pseudotachylyte veins were generated mainly by crushing rather than melting, (ii) multistage veinlet fault gouge and pseudotachylyte formed repeatedly within the fault-fracture zone via the rapid fluidization and injection of superfine- to fine-grained materials derived from the host granitic rocks during seismic faulting events, and (iii) veins of alluvial deposit formed by liquefaction associated with strong groundmotion during large-magnitude earthquakes that occurred along the active Shimotsuburai fault of the ISTL-AFS. Our results show that the fluidized cataclastic veins and alluvial deposit veins record paleoseismic faulting events that occurred within a seismogenic fault zone; consequently, these features are a type of earthquake fossil, as is melt-origin pseudotachylyte. [ABSTRACT FROM AUTHOR]

The article presents information on a study related to the increase in the seismic activity at the Kuril Islands, Russia which is the place hit by two of the strongest catastrophic earthquakes. It informs that the study focused on the peculiarities of the tectonic stress field in the region of the Middle Kuril Islands by utilizing a method of method of cataclastic analysis (MCA). It further informs that reconstruction of the stress tensor components, increments of quasiplastic deformations, and estimation of the mechanical properties were performed using this method which is based on Centroid Momentum Tensor (CMT) data.

Fault rocks can function as barriers to subsurface fluid flow and affect the storage of CO2 in geological structures. Even though flow across faults often involves more than one fluid phase, it is typically modeled using only single-phase functions due to a lack of fault rock relative permeability data and complexities in incorporating two-phase flow properties into flow simulations. Here we present two-phase fluid flow data for cataclastic fault rocks in porous sandstone from the 90-Fathom fault (northeast England). The study area represents a field analogue for North Sea saline aquifers of Permian-Triassic age that are currently being considered for CO2 storage. We use the experimental data to populate a synthetic model of a faulted saline aquifer to assess the impact of these fault rocks on CO2 injection. We show that even fault rocks with low clay contents and very limited quartz cementation can act as major baffles to the flow of a non-wetting phase if realistic two-phase properties are taken into account. Consequently, pressure may increase far more rapidly in the storage compartment during CO2 injection than anticipated based on models that only incorporate absolute fault rock permeabilities. To avoid high pressures, which may lead to hydrofracturing and CO2 leakage, either more complex injection strategies need to be adopted or seismic data acquired to ensure the absence of faults in aquifers selected for CO2 storage. [ABSTRACT FROM AUTHOR]

Abstract: X-ray computed tomography (XRCT) can reconstruct, in a nondestructive way and in three-dimension, the distribution of densities within opaque materials. Consequently, it provides an effective possibility to characterize the inner content of rock core samples and, in particular their alteration products sensu lato which generally appear less dense than the intact rock matrix. In this paper, a new index, based on XRCT data, is tested for evaluating the degree of alteration of highly tectonized carbonate rock samples and is compared with visual-based classification systems. This XRCT-based analysis leads to a diagnosis of alteration which appears objective, precise and in agreement with the visual observations. Besides, this method takes into account the entire volume of the sample, is rapid to carry out and allows an intact rock core to be used for further laboratory testing. [ABSTRACT FROM AUTHOR]

The article discusses the role of fractures in gabbroids formation in a Sierra Leone test area. It says that gabbroids are developed in zones of the Sierra Leone nontransform displacement and the Bogdanov transform fault. It mentions the seven recognizable metamorphic lithotectonic parageneses in Sierra Leone gabbroids, including textures of brittle-plastic deformations, textures of brittle deformations and cataclasites, and metasomatically replaced rock-forming minerals without deformation features. It states that each lithotectonic parageneses characterizes certain temperature, deformation rates, and relative stress load. It concludes that in mid-oceanic ridges (MOR), cataclastic and plastic flows and tectonic fractures were responsible for exhumation of deep rocks to the surface.

Abstract: Borehole studies of the Soultz-sous-Forêts granite are dedicated to deep geothermics. The hydraulic properties of the reservoir are mainly controlled by the occurrence of some altered cataclastic shear zones showing a low natural permeability characterized by the occurrence of brines. Those zones show a fracture cluster organisation with sealed fractures of various types (post-filled joints, sheared fractures, veins). The main hydrothermal deposits observed within the permeable zones are geodic quartz, carbonates, illite and more locally sulphides. The fracture wall–rocks are intensely transformed: dissolution of igneous minerals, crystallization of new minerals, porosity and permeability increase. It is important to characterize the newly-formed minerals in order to choose the reagents used to improve the permeability of the exchanger by chemical stimulations. This article represents a synthesis of the studies completed by the authors between 1990 and 2008 on the fracture networks, hydrothermal alterations and mineral crystallizations they induced and data about the flow pathways in the exchanger. [Copyright &y& Elsevier]

Abstract: Monitoring of chemical and physical groundwater parameters has been carried out worldwide in seismogenic areas with the aim to test possible correlations between their spatial and temporal variations and strain processes. Uranium (U) groundwater anomalies were observed during the preparation phases of the recent L''Aquila earthquake of 6th April 2009 in the cataclastic rocks near the overthrust fault crossing the deep underground Gran Sasso National Laboratory. The results suggest that U may be used as a potential strain indicator of geodynamic processes occurring before the seismic swarm and the main earthquake shock. Moreover, this justifies the different radon patterns before and after the main shock: the radon releases during and after the earthquake are much than more during the preparatory period because the process does not include only the microfracturing induced by stress–strain activation, but also radon increases accompanying groundwater U anomalies. [Copyright &y& Elsevier]

Geological and geophysical evidence suggests that some crustal faults are weak compared to laboratory measurements of frictional strength. Explanations for fault weakness include the presence of weak minerals, high fluid pressures within the fault core and dynamic processes such as normal stress reduction, acoustic fluidization or extreme weakening at high slip velocity. Dynamic weakening mechanisms can explain some observations; however, creep and aseismic slip are thought to occur on weak faults, and quasi-static weakening mechanisms are required to initiate frictional slip on mis-oriented faults, at high angles to the tectonic stress field. Moreover, the maintenance of high fluid pressures requires specialized conditions and weak mineral phases are not present in sufficient abundance to satisfy weak fault models, so weak faults remain largely unexplained. Here we provide laboratory evidence for a brittle, frictional weakening mechanism based on common fault zone fabrics. We report on the frictional strength of intact fault rocks sheared in their in situ geometry. Samples with well-developed foliation are extremely weak compared to their powdered equivalents. Micro- and nano-structural studies show that frictional sliding occurs along very fine-grained foliations composed of phyllosilicates (talc and smectite). When the same rocks are powdered, frictional strength is high, consistent with cataclastic processes. Our data show that fault weakness can occur in cases where weak mineral phases constitute only a small percentage of the total fault rock and that low friction results from slip on a network of weak phyllosilicate-rich surfaces that define the rock fabric. The widespread documentation of foliated fault rocks along mature faults in different tectonic settings and from many different protoliths suggests that this mechanism could be a viable explanation for fault weakening in the brittle crust. [ABSTRACT FROM AUTHOR]

Abstract: The term cataclastic diapirism is proposed for the low-temperature extrusion of highly fractured rocks through more competent strata to produce domed topographies at the surface. The process is illustrated by reference to the geomorphology, neotectonics and microseismicity of the Pie de Palo, an elongated ridge in the western Sierras Pampeanas of Argentina composed of shattered and sheared Lower Palaeozoic rocks and subject to coseismic uplift. The Pie de Palo is conventionally interpreted as a fault-driven basement fold linked to low-angle eastward subduction of the Nazca plate beneath South America; the diapiric model implies instead that deformation is powered by regional compression from west-verging, near-surface, crustal shortening which results ultimately from Atlantic spreading. [Copyright &y& Elsevier]

Cataclastic rocks, as clay-rich fault gouges, are commonly present in brittle rock masses when fault zones appear during geological engineering projects. Highly deformed rocks that are of poor mechanical quality can lead to technical, safety, and economic problems in rock engineering. The aim of this study is to characterise the resistant behaviour of a highly deformed clay-rich gouge >40 m wide with a marked tectonic fabric that indicates strength anisotropy. We present the results of consolidated-undrained (CU) triaxial tests that were performed at low confining pressures (50, 150, and 300 kPa) on several sets of foliated gouge specimens with four different orientations in the tectonic fabric. Specimens were collected from the encapsulated rock cores of two research boreholes drilled through the Alhama de Murcia Fault (AMF), a main regional fault located in SE Spain. The strain–stress relationships and failure modes were established, indicating that the gouge behaves as hard soil or very soft rock. The test results were adjusted at each orientation using the non-linear Hoek and Brown criteria by considering the fault gouge as an intact material or as a tectonised rockmass. Here, we use the Geological Strength Index (GSI) as an indicator of the rockmass strength that depends on the direction of the tectonic fabric. However, the results from specimens with tectonic fabric that is oriented most favourably for failure were not the weakest in terms of rock strength. Such an anomalous result could be the result of asymmetry in the roughness of the weakness planes that is related to the original gouge microstructure characterised by the strong reorientation of clays in an S-C′ like tectonic fabric. Our results will be useful for practical applications that are related to the stability of slopes and/or shallow underground excavations in brittle fault zones, and provide an inexpensive and easy way to preliminarily evaluate the anisotropic behaviour of this type of brittle fault zones for future engineering projects. • Strength of a foliated clay-rich fault gouge is controlled by roughness within the weak planes. • Gouge microstructure defined by strong reorientation of clays in a S-C' fabric controls the roughness of the weakness planes • Strength of clay gouges shows a medium to low anisotropy. • GSI is a sensitive index with which the strength anisotropy of tectonised rocks can be investigated. [ABSTRACT FROM AUTHOR]

The mechanical behaviour of cataclastic rocks is hard to characterise because of many difficulties arising in getting undisturbed samples during field investigations, in specimen preparation, and in performing appropriate laboratory testing. To acquire a better understanding of such kind of very poor rocks, the EPFL''s Rock Mechanics Laboratory has carried out an extensive laboratory testing programme on cataclastic rocks from the Cleuson–Dixence project (Switzerland). After some reflections on the quantification of the intensity of tectonic degradation process by means of the Geological Strength Index, the paper describes briefly the sampling and testing techniques. Then it focuses on the failure criterion and the stress–strain relationship of two types of cataclastic rocks: quartzitic sandstones and phyllitic schists. A new failure criterion is suggested: it consists in an extension of the Hoek and Brown failure criterion that takes into account the progressive damage undergone by cataclastic rocks during the tectonic degradation process. Its parameters are bounded by an upper limit corresponding to the original rock and a lower limit corresponding to a soil-like extremely tectonised material. Finally, the stress–strain behaviour of the tested cataclastic rocks is found to depend on the confining stress and the tectonisation degree and is adequately approached by the hyperbolic law of Duncan and Chang. [Copyright &y& Elsevier]

Describes the statistical analysis and origin of the magnetic susceptibility of drill cuttings from KTB drip hole. Determination of ferrimagnetic susceptibility; Measurement of the amount of cataclastic rocks; Susceptibility distribution of metabasites.

The tectonic units of Crete are divided in a Lower- and an Upper Nappe system that are separated by the so called Cretan Detachment. The Upper Nappe System was almost not affected by Alpine metamorphism but the Lower Nappe System experienced high-pressure/low-temperature metamorphism. Therefore, it has been suggested that the tectonic contact represents a low-angle top-to-the N extensional shear zone. However, a number of studies present conflicting and/or not very convincing kinematic indicators and came to the conclusion that the Cretan Detachment reflects bivergent extension with a strong component of coaxial deformation or a top-to-the S thrust. Recent data on calcite twinning, Raman spectroscopy of carbonaceous material and illite crystallinity from the Upper and Lower Nappe System also suggest that the Cretan Detachment might be a Miocene thrust, which was active at mid to upper crustal conditions..In this work, we investigate fault rocks from several locations in in Eastern Crete, where the Tripolitza Unit (Upper Nappe System) is juxtaposed against the Phyllite-Quartzite Unit s.l. (Lower Nappe System). The Tripolitza Unit in the hanging wall consists of Upper Triassic platform carbonates and the Phyllite-Quartzite Unit s.l. in the footwall is composed of violet-greenish slates and quartz-rich phyllites. Major displacement is localized in an almost horizontal detachment with up to several meter thick foliated ultracataclasites and fault gouges, which record numerous kinematic indicators like duplex structures, scaly fabrics, Riedel fractures, which consistently confirm top-to-N displacement. The cataclastic material is mainly derived from the violet and greenish slates in the footwall that are below the detachment zone strongly folded with subvertical limbs overprinted by a subhorizontal axial plane slaty cleavage. Asymmetric crenulation cleavage can be (and has been!) easily confused with SSC' fabrics, obscuring the clear picture of a top-to-the N sense of shear. The only slightly recrystallized carbonates of the overlying Tripolitza Unit are cut by parallel steeply S-dipping antithetic normal faults forming bookshelves, which are tilted towards the north. Numerous injection dykes, polished slicken sides and truncated grains at principal slip surfaces probably suggest seismic movement along the Cretan Detachment. New (U-Th)/He zircon ages are dispersed and as old as 130 Ma, but a significant population of the dates are ca. 14.5 Ma. These dates are much younger than the published zircon fission track dates for eastern Crete, and help constrain the temperature of deformation to 200 ± 20°C. Although we do not question the occurrence of an earlier thrusting component along this tectonic contact, our data from mainly cataclastic rocks clearly indicate Miocene top-to-N normal slip along the eastern part of the 'Cretan Detachment.' [ABSTRACT FROM AUTHOR]

We present the preliminary results of a multiscalar structural study of an outstanding exposure of the Belluno Thrust of the Italian Southern Alps (Monte Coppolo area, Feltre region). The Belluno Thrust is one of the main structures forming the orogen-scale WSW-ENE-trending thrust system that contributed to the building of the Southern Alps in the context of the Neogene Alpine evolution. Thrust tectonics, expressed by generally SSE-verging low-angle thrusts, started in the upper Oligocene and continues to present times, as documented by active faults considered to be the seismogenic sources affecting the eastern Southern Alps. In the Monte Coppolo area, the Belluno Thrust marks the tectonic juxtaposition of Early Jurassic oolitic and micritic limestones (the Calcari Grigi Group) on top of Late Jurassic-Early Cretaceous pelagic limestones (the Maiolica Fm). At the outcrop-scale, the thrust corresponds to an up to 2 m-thick complex deformation zone striking WSW-ENE and dipping NNW at less than 40°. Kinematic indicators confirm top-to-the-SSE tectonic transport. The fault consists of blandly anastomosed slip surfaces wrapping around lenses of massive cataclasites and less deformed, dm-to-half metre-thick strained lithons that sample both the hanging wall and the footwall blocks. At the top, the deformation zone is bounded by a sharp principal slip surface over which the Calcari Grigi Group is stacked. Microstructural investigations on samples that are representative of the identified fault facies denote that: (i) cataclasites consist of a fine-to-very fine- grained matrix (in the order of the clay-size fraction) hosting poorly-sorted and variably rounded fragments of limestone derived from both the hanging wall and footwall limestones as well as early cataclased fragments; (ii) the strained lithons display evidence of a long and complex deformation history documented by multiple arrays of shear and dilatant fractures filled by calcite, SC-like structures within foliated microdomains, and pervasive pressure-solution; (iii) the principal slip surface is a mm-thick surface that abruptly cuts at an angle < 10° an underlying foliated cataclasite; and (iv) the hanging wall Calcari Grigi Group limestone is deformed by a complex system of cross-cutting shear veins and diffuse evidence of pressure-solution. These preliminary observations constrain a thrusting faulting mechanism aided by major cataclastic flow and localised sliding within a seismic scenario, wherein strain localised into a progressively narrower fault core, likely assisted by fluid circulation and synkinematic clay authigenesis along individual slip surfaces. The principal slip surface likely represents the last increment of strain at the outcrop. These deformation processes are considered to be representative of the mechanical behaviour of the Belluno Thrust in response to the stress accumulation during its seismic cycle and provide further insights on strain localisation in carbonatic rocks. [ABSTRACT FROM AUTHOR]

Comments on the issue about the study of pseudotachylite-bearing friction marks on andesitic blocks. Types of structures on block surfaces; Formation of pseudotachylites; Decrease of grain size on cataclastic layers.