Carbonate Fault Research Articles

Pore space properties in carbonate fault rocks of peninsular Italy

The fault cores of extensional faults in Mesozoic limestones and dolostones are examined by mean of combined microstructural, ultrasonic and petrophysical analyses. Grain-supported fault rocks commonly localize in the outer fault cores, whereas matrix-supported fault rocks in their inner portions. Cemented fault rocks, if present, surround the main slip surfaces. All dolomite-rich fault rocks, include elongated pores that show a preferential orientation only in the inner fault core. On the contrary, the pore network of calcite-rich fault rocks is made up of elongated pores in the outer fault core, and of sub-spherical pores in the inner fault core. Despite their different pore network characteristics, the petrophysical values of both grain-supported and matrix-supported fault rocks are quite similar one another, with effective porosity up to 10–12%, and permeability up to 2–5 mD. Differently, these values drop down to host rock values, porosity ~5% and permeability ~10−3 mD, in the cemented fault rocks. Experimental data are discussed to establish, for the first time, the relative control exerted by individual cataclastic and diagenetic processes on the present day pore characteristics, and to decipher the fault core permeability structure at depth.

Permeability of carbonate fault rocks: a case study from Malta

The inherent heterogeneity of carbonate rocks suggests that carbonate-hosted fault zones are also likely to be heterogeneous. Coupled with a lack of host–fault petrophysical relationships, this makes the hydraulic behaviour of carbonate-hosted fault zones difficult to predict. Here we investigate the link between host rock and fault rock porosity, permeability and texture, by presenting data from series of host rock, damage zone and fault rock samples from normally faulted, shallowly buried limestones from Malta. Core plug X-ray tomography indicates that texturally heterogeneous host rocks lead to greater variability in the porosity and permeability of fault rocks. Fault rocks derived from moderate- to high-porosity (>20%) formations experience permeability reductions of up to six orders of magnitude relative to the host; >30% of these fault rocks could act as baffles or barriers to fluid flow over production timescales. Fault rocks derived from lower-porosity (<20%) algal packstones have permeabilities that are lower than their hosts by up to three orders of magnitude, which is unlikely to impact fluid flow on production timescales. The variability of fault rock permeability is controlled by a number of factors, including the initial host rock texture and porosity, the magnitude of strain localization, and the extent of post-deformation diagenetic alteration. Fault displacement has no obvious control over fault rock permeability. The results enable better predictions of fault rock permeability in similar lithotypes and tectonic regimes. This may enable predictions of across-fault fluid flow potential when combined with data on fault zone architecture.

Fracture stratigraphy and DFN modelling of tight carbonates, the case study of the Lower Cretaceous carbonates exposed at the Monte Alpi (Basilicata, Italy)

Abstract This work focuses on the role played by depositional/diagenetic heterogeneities on the vertical growth of sub-seismic, high-angle structural elements such as joints, sheared joints, small faults, and well-developed faults in Lower Cretaceous tight carbonates exposed along the 100's m-high, km-long, western cliff of the Monte Alpi massif. The study carbonates pertain to the Inner Apulian Platform, and form a surface structural analogue of the fractured carbonate reservoirs currently exploited for hydrocarbon production in nearby areas of southern Italy. By combining traditional field stratigraphic and structural methods with photogrammetric analysis of a large portion of the aforementioned cliff, we assess the abutting and crosscutting relationships among the sub-seismic structural elements and different types of flooding surfaces. At smaller scale, bed interfaces extend laterally for a few tens-of-metres, bound tens-of-centimetres-thick beds characterized by amalgamation and bifurcation geometries, and form sequence boundaries of the 4th-5th order. At larger scale, transgressive surfaces extend laterally for hundreds-of-metres, include mm-thick terrigenous material, bound multiple metre-thick bed packages made up of multiple beds, and form sequence boundaries of the 3rd order. Field evidences are consistent with joints and sheared joints often forming stratabound and non-stratabound elements, respectively. At a reservoir scale, prominent transgressive surfaces are laterally continuous for kilometres, include up to a few centimetres-thick, clay-rich levels and collapsed breccia, bound tens-of-metres-thick bed package associations, and form sequence boundaries of the 2nd order. There, small faults with up to 10's of cm-offset mainly localize within individual bed package associations, whereas well-developed faults with up to a few m-offset crosscut multiple prominent transgressive surfaces. Results after DFN modelling of representative geo-cellular models highlight the control exerted by the study structural elements on the fluid accumulation and flow properties of the fractured carbonates. These data are useful to fill the gap between core and seismic data, as they provide information on the sub-seismic domain (i.e. below seismic resolution).

Influence of analytical operating procedures on particle size distributions in carbonate cataclastic rocks

Fractal dimensions of fault core rocks provide a suitable tool to estimate amounts of comminution and describe processes associated with faulting, such as hydraulic sealing, and nucleation and propagation of coseismic ruptures. It is thus important to be aware of possible biases produced by different analytical procedures on given materials, to prevent unsupported interpretations of granulometric data. The aim of this paper is to minimize the method-induced variability in the calculation of fractal dimensions. We present a comparison among different 2D and 3D analytical techniques that are commonly used to calculate grain size distributions, even introducing and discussing new analytical techniques never used before in the study of fault core rocks. The studied samples are loose and coherent carbonate cataclastic rocks collected at the same field site along the Fiamignano Fault in the Central Apennines (Italy). Our results provide further support to the evidence that analytical procedures can significantly influence particle size distributions and related D-values. It follows that direct comparison between different datasets is not straightforward if rigorous analytical protocols are not systematically used and described. Guidelines for fractal analysis of carbonate fault rocks are provided.

Seismic damage zone and width\u2013throw scaling along the strike-slip faults in the Ordovician carbonates in the Tarim Basin

Understanding the scaling relation of damage zone width with displacement of faults is important for predicting subsurface faulting mechanisms and fluid flow processes. The understanding of this scaling relationship is influenced by the accuracy of the methods and types of data utilized to investigate faults. In this study, seismic reflection data are used to investigate the throw and damage zone width of five strike-slip faults affecting Ordovician carbonates of the Tarim intracraton basin, NW China. The results indicate that fault slips with a throw less than 200 m had formed wide damage zones up to 3000 m in width. Also, damage zone width is found to have both a positive correlation and a power-law relation with throw of two orders of magnitude, with a ratio of these values varying in a range of 2–15. The relationship between throw and damage zone width is not a simple power-law and changes its slope from small to larger size faults. The results indicate that throw scales well with damage zone width for the studied faults, and hence these can be used to predict fault geometries in the Tarim Basin. The study of the wide carbonate damage zones presented here provides new insights into scaling of large-size faults, which involve multiple faulting stages.

Structural Diagenesis in Carbonate Rocks as Identified in Fault Damage Zones in the Northern Tarim Basin, NW China

The identification of structural diagenesis and the reconstruction of diagenetic paragenesis in fault damage zones is important for understanding fault mechanisms and fluid flow in the subsurface. Based on the examination of core and sample thin section data, we deciphered the diagenetic parasequence and their fault controls for Ordovician carbonates in the northern Tarim intracratonic basin in NW China (Halahatang area). In contrast to the uniform nature of diagenesis observed in country rocks, there is a relatively complicated style of compaction and pressure solution, multiple fracturing, and cementation and dissolution history along the carbonate fault damage zones. The relative paragenetic sequence of the structure related diagenesis suggests three cycles of fracture activities, following varied fracture enlargement and dissolution, and progressively weaker calcite cementation. These processes of structure related diagenesis are constrained to the fault damage zones, and their variation is affected by the fault activities. The results of this study suggest that the carbonate reservoir and productivity could be impacted by the structure related diagenesis locally along the fault damage zones.

Effect of Fluid Chemistry on the Interfacial Composition, Adhesion, and Frictional Response of Calcite Single Crystals—Implications for Injection‐Induced Seismicity

AbstractWhile it has been shown that the mechanical properties and the reactivity of carbonate‐bearing rocks may be influenced by the chemical composition of the fluids, little is known about how the fluid composition affects their frictional response. Here, we have used atomic force microscopy to investigate the frictional characteristics of single calcite crystals in calcium carbonate saturated solutions and in two brines, NaCl and CaCl2, at a wide range of geologically relevant concentrations. Surface forces were measured to determine the ion‐specific composition of the confined fluid films and the adhesion between the confining surfaces. The effect of fluid chemistry on calcite's (dynamic) frictional response significantly depends on the normal stress. At low stresses, the confined fluid film lubricates the single‐asperity contact efficiently, resulting in low friction coefficients, especially in the case of NaCl solutions. When the pressure solution of calcite is triggered at sufficiently high stress, a significant reduction of the friction coefficient was observed, and in this case, CaCl2 solutions were shown to promote this frictional weakening more significantly than NaCl. This is the first experimental investigation of the ion‐specific frictional characteristics of calcite at the level of a single‐asperity contact. The presence of infiltrated fluids in carbonate faults may also play a critical role in fault dynamics. Hence, the results of this nanoscale study are extrapolated to carbonate fault friction in the presence of infiltrated fluids, and they contribute to advance our understanding of induced seismicity at geological scale.

Development of crystallographic preferred orientation during cataclasis in low-temperature carbonate fault gouge

Grain size reduction due to cataclasis is a key process controlling fault frictional properties during the seismic cycle. We investigated the role of cleavage planes on fracturing and microstructural evolution during cataclasis in wet and dry carbonate fault gouges (50 wt% calcite, 50 wt% dolomite) deformed in a rotary-shear apparatus over a wide range of slip rates (30 μms−1 to 1 ms−1) and displacements (0.05–0.4 m). During shearing, progressive strain localization forms a narrow slip zone that undergoes significant frictional heating (at high slip rates), but the bulk gouge always accommodates low finite shear strains and deforms at low temperatures. Microstructural analysis of the bulk gouges indicates that deformation occurred by brittle fracturing and twinning. Microfractures in calcite are closely spaced, often exploit {101¯4} cleavage r-rhomb planes, and occur mainly subparallel to the expected principal stress orientation (σ1). Instead, twin planes typically occur sub-perpendicular to σ1. Electron backscatter diffraction analysis of the bulk gouges shows that calcite develops a well-defined crystallographic preferred orientation (CPO) at all investigated deformation conditions. The CPO is defined by a clustering of the calcite c-axes around an orientation sub-parallel to σ1. The calcite CPO is interpreted to result from grain rotation during granular flow, followed by brittle fracturing that occurred preferentially along calcite cleavage planes. This interpretation is supported by measurements of calcite grain shape-preferred orientations that show a population of elongate calcite grains oriented with their long axes sub-parallel to σ1. Our experimental results indicate that well-defined CPOs can form at low temperature in cataclastic fault rocks, and that mineral cleavage can strongly influence the evolution of grain sizes and shapes during comminution.

The relationship between fault zone structure and frictional heterogeneity, insight from faults in the High Zagros

Frictional heterogeneities within fault zones depend strongly on lithology as well as shear fabric and strain localization structures. Here we investigate the impact of fault rock composition and shear fabric on friction constitutive properties for mature High Zagros (Iran) fault rocks. We present field observations along with results from friction experiments on intact and powdered fault rock from carbonate, quartzofeldspathic and schist. We measured frictional strength and rate/state dependence over normal stresses from 25 to 100 MPa and shear slip velocities from 3 to 300 μm/s. The sliding friction coefficients of intact fault rocks are lower than their powdered equivalents. The foliated quartzofeldspathic and lensoidal carbonate rocks from the Main Zagros Reverse Fault (MZRF) exhibit velocity strengthening friction and stable sliding. In contrast, the cataclasite carbonate rocks from the younger, Main Recent Fault (MRF) exhibit potentially unstable, velocity-weakening frictional behavior, consistent with regional seismicity. Our results suggest that solution seams, cleavage processes, and development of stylolite and calcite veins in the carbonate fault rocks of the MZRF continually rejuvenate and rework shear structures, which leads to dominantly aseismic shear. In contrast, younger fault rocks of the MRF form highly localized shear zones and shear fabric that result in velocity-weakening frictional behavior and seismic slip. Our field observations and laboratory data provide insights for using friction data and fault zone structure to build predictive models of the mode of fault slip in zones of tectonic collision.

Structural diagenesis of carbonate fault rocks exhumed from shallow crustal depths: An example from the central-southern Apennines, Italy

This contribution focuses on field and laboratory analyses of carbonate fault cores pertaining to high-angle extensional fault zones currently exposed in the central and southern Apennines, Italy. The fault zones studied crosscut Mesozoic platform-related carbonate rocks, strike ca. NW-SE, and dip steeply SW. They formed during the Plio-Quaternary downfaulting of the Apennine fold-and-thrust belt and were exhumed from shallow crustal levels (<1.5 km). The carbonate fault cores include grain-supported, matrix-supported, and cement-supported fault rocks, fluidized layers of ultracataclasites with injection veins, and main slip surfaces. Our results of microstructural, petrographic, and cathodoluminescence analyses highlight the contrasting diagenetic evolution of calcite- and dolomite-rich fault rocks. Physical compaction was common within the dolomite-rich fault rocks, whereas chemical compaction coupled with dissolution characterized the calcite-rich fault rocks. Furthermore, multiple generations of calcite cements are documented in the fault zones. The first generation consists of a microcrystalline calcite cement, which developed around survivor grains and lined intergranular pores. The second generation is made up of light-luminescent, fibrous calcite crystals, which precipitated within open fractures and around survivor grains. The third generation consists of an euhedral calcite cement that surrounded survivor grains and infilled both open fractures and intergranular pores.

Fracture attributes in reservoir-scale carbonate fault damage zones and implications for damage zone width and growth in the deep subsurface

The width of reservoir-scale fault damage zone governs fluid flow of the tight reservoirs in subsurface petroliferous basins. Together with cores, thin sections, geophysical well logs, and production data from more than 60 wells, we describe fracture attributes and fault damage zones associated with a conjugate strike-slip fault system in tight Ordovician carbonate rock at depths of between 6500 m and 7500 m in the Tarim intracratonic basin in NW China. Fracture frequency, aperture, and oil production in wells reveals a power-law relationship with the distance from fault cores, with a variation in two orders of magnitude. The cumulative data of fracture frequency, aperture and oil production show multiple gradients in slope with the distance. Except for sampling bias, the varied gradients are possibly related to the overlaying multiple fault zones or multiple sections along a large fault zone, which are useful to constrain damage zone width. Together with fracture frequency, cumulative fracture frequency, aperture and oil production, four major damage zone boundaries are identified at ∼200, ∼420 m, ∼780 m and ∼1100 m. Therefore, a wide fault damage zone with a width of more than 2 km in the carbonate rocks could be inferred, which mostly depends on the interaction and superposition of secondary faults. In addition, there is a relatively high fracture frequency decay exponent (>1) with distance, which is possibly related to fault size, fault splays, background fracture frequency and the lithology. In turn, the growth of wide damage zone also resulted in a large scattered distribution of the fracture attributes with the distance from fault cores. Attributes of fractures of various scales from the deep subsurface provide powerful tools for assessing damage zone width and growth.

Seismic moment and recurrence: Microstructural and mineralogical characterization of rocks in carbonate fault zones and their potential for luminescence and ESR dating

The important question of absolute dating of seismic phenomena has been the study of several researchers over the past few decades. The relevant research has concentrated on “energy traps” of minerals, such as quartz or feldspar, which may accumulate chronological information associated with tectonic deformations. However, the produced knowledge so far, is not sufficient to allow the absolute dating of faults. Today, Luminescence and Electron Spin Resonance (ESR) dating methods could be seen as offering high potential for dating past seismic deformed features on timescales ranging from some years to even several million years.This preliminary study attempts to establish the potential of three different carbonate fault zones hosting fault mirror-like structures, to be used in luminescence and ESR dating, based on their microstructural, mineralogical and palaeo-maximum temperatures analysis. The results indicated that the collected samples can be considered datable fault-rock materials, since they contain suitable minerals (quartz) for luminescence and ESR dating, have experienced repeated cataclastic deformation and have been subject to various physical and chemical processes as well as pressure and temperature conditions.

Investigating the controls on fault rock distribution in normal faulted shallow burial limestones, Malta, and the implications for fluid flow

The spatial distribution and fabric of carbonate fault rocks observed at outcrop are often highly heterogeneous. Therefore, petrophysical properties of fault rock samples may not be representative of the overall sealing capacity of the fault zone. By quantifying the fault rock distributions (i.e. fault rock thickness and fault rock continuity) of several fault zones in Malta, juxtaposing shallow burial limestones, this work investigates the relationship between fault zone architecture, deformation mechanisms, and fault rock distribution. Results from microstructural analyses indicate that high porosity (>15%) grain-dominated limestones deform via grain scale deformation, as opposed to fracture-derived cataclasites often observed in tight carbonates. Low porosity (<15%) grain-dominated limestones and high porosity micrite-dominated limestones deform in a more distributed manner, through extensional fracturing and brecciation. Fault rock continuity estimates suggest displacements of 50–200 m are required to form a continuous low-permeability cataclasite veneer in the studied sequence. However, greater displacements may be required when a distributed damage zone is present, in which strain is accommodated over multiple slip surfaces. This work highlights the heterogeneity in the distribution and fabric of carbonate fault rocks within fault zones hosting tens of meters displacement, and the importance of considering fault rock thickness and continuity when estimating the sealing capacity of a carbonate-hosted fault zone.

Space-time evolution of cataclasis in carbonate fault zones

The present contribution focuses on the micro-mechanisms associated to cataclasis of both calcite- and dolomite-rich fault rocks. This work combines field and laboratory data of carbonate fault cores currently exposed in central and southern Italy. By first deciphering the main fault rock textures, their spatial distribution, crosscutting relationships and multi-scale dimensional properties, the relative timing of Intragranular Extensional Fracturing (IEF), chipping, and localized shear is inferred. IEF was predominant within already fractured carbonates, forming coarse and angular rock fragments, and likely lasted for a longer period within the dolomitic fault rocks. Chipping occurred in both lithologies, and was activated by grain rolling forming minute, sub-rounded survivor grains embedded in a powder-like carbonate matrix. The largest fault zones, which crosscut either limestones or dolostones, were subjected to localized shear and, eventually, to flash temperature increase which caused thermal decomposition of calcite within narrow (cm-thick) slip zones. Results are organized in a synoptic panel including the main dimensional properties of survivor grains. Finally, a conceptual model of the time-dependent evolution of cataclastic deformation in carbonate rocks is proposed.

Strength evolution of simulated carbonate-bearing faults: The role of normal stress and slip velocity

A great number of earthquakes occur within thick carbonate sequences in the shallow crust. At the same time, carbonate fault rocks exhumed from a depth < 6 km (i.e., from seismogenic depths) exhibit the coexistence of structures related to brittle (i.e., cataclasis) and ductile deformation processes (i.e., pressure-solution and granular plasticity). We performed friction experiments on water-saturated simulated carbonate-bearing faults for a wide range of normal stresses (from 5 to 120 MPa) and slip velocities (from 0.3 to 100 μm/s). At high normal stresses (σn > 20 MPa) fault gouges undergo strain-weakening, that is more pronounced at slow slip velocities, and causes a significant reduction of frictional strength, from μ = 0.7 to μ = 0.47. Microstructural analysis show that fault gouge weakening is driven by deformation accommodated by cataclasis and pressure-insensitive deformation processes (pressure solution and granular plasticity) that become more efficient at slow slip velocity. The reduction in frictional strength caused by strain weakening behaviour promoted by the activation of pressure-insensitive deformation might play a significant role in carbonate-bearing faults mechanics.

Fabric transition with dislocation creep of a carbonate fault zone in the brittle regime

Fabric transition by a switch in the dominant slip system of minerals in the plastic regime can be induced by changes in temperature, strain rate, or water content. We propose here this fabric transition by frictional heating in seismogenic fault zones in the brittle regime. The Garam Thrust in the Taebaeksan Basin of South Korea has a hanging wall of Cambrian dolostone juxtaposed against a footwall of Ordovician limestone and records a minimum displacement of ~120m. In a 10cm thick plastically deformed layer adjacent to the principal slip layer of the fault zone, the lattice preferred orientation of calcite grains suggests that the dominant slip system changes, approaching the principal slip layer, from r 〈02–21〉 and e-twinning, through r 〈02–21〉 and basal 〈a〉, to basal 〈a〉. This fabric transition requires a high temperature-gradient of 40°C/cm, which we infer to result from frictional heating of the seismic fault zone. We suggest that fabric transition within a thin plastically deformed layer adjacent to the principal slip layer of a fault zone indicates an unusually steep temperature gradient and provides strong evidence of seismic slip.

Discrete Fracture Network modelling of a hydrocarbon-bearing, oblique-slip fault zone: Inferences on fault-controlled fluid storage and migration properties of carbonate fault damage zones

Discrete Fracture Network (DFN) modelling is a useful tool to assess both fluid storage and migration properties of naturally fractured carbonate rocks. This work presents the results of multiple DFN models, which represent the structural network associated with a ca. 100 m–offset, oblique-slip, normal fault zone crosscutting Miocene ramp carbonates of the Majella Mountain, Italy. Specifically, by taking advantage of a previously published conceptual model of fault nucleation and growth, the DFN models are aimed at computing the amount of fracture porosity and equivalent permeability of representative portions of the evolving fault damage zone. In fact, by first considering only background structural elements, those pre-dating the fault nucleation stage, all fault-related structural elements such as joints, small and medium faults are added, one by one, according to their relative time of formation. Small faults are characterized by several cm-offset, whereas the latter ones have several 10's of cm-offset. The following fracture parameters are inputted for each structural element: (i) length; (ii) aspect ratio; (iii) mechanical and hydraulic aperture; (iv) fracture intensity and (v) orientation. A sensitivity analysis is carried out in order to test the seeding procedure of the software, and the input fracture aperture values. Results of DFN modelling are consistent with the small faults forming the main repository for underground geofluids. Differently, the fluid migration paths through the fault damage zone are mainly controlled by opening-mode-related fractures, which mainly form clusters at the extensional quadrants of sheared structural elements. Due to their attitude and distribution, these features mainly enhance fault-parallel fluid migration paths. In fact, the computed values of horizontal equivalent permeability obtained along this direction are about one order of magnitude higher than those along the orthogonal direction. The approach and methodologies applied in this work, together with the results of the multiple DFN model configurations show the relative influence and role of the different structural elements on fluid storage and migration properties of limestone-hosted, fault damage zones.

Analogue modeling of through-going process and development pattern of strike-slip fault zone

Nine sets of sand-box experiments were designed according to actual geologic data to investigate the evolution pattern and development mechanism of simple shear strike-slip fault zone using the fault CT scanning technique. The experimental results show that R (Riedel) shears were developed early and more in number, and one set of these faults intersected with the principal displacement zone (PDZ) at relatively lower angle; the P shears (being in symmetrical distribution with the R shears) and Y shears (subparallel to PDZ) were developed later than the R shears, and the fault zone was through-going only after the formation of Y shears. The through-going process of strike-slip fault zone can be divided into four stages: embryonic stage, R (Riedel) shears development stage, P shears and Y shears development stage, and through-going stage of fault zone. In the process, the faults developed progressively from the basement to the top cover, the faults spread upward in the profile at embryonic stage, and then converged toward the PDZ on the plane at R shears development stage. The modeling supports that the en echelon structure developed in “helicoidally drag” pattern, however, the length of the en echelon fault grew linearly doubling the growth rate of its depth, and the fault intersection angle with the PDZ decreased in quadratic function with the increase of its depth. The analysis reveals that cover thickness and the maximum principal stress direction are the main factors causing the difference in “helicoidally drag” structure. The modeling provides guidance for the strike-slip fault interpretation and evolution study, and layering and segmenting faults in the marine carbonates of the Tarim Basin.

Predicting transmissibilities of carbonate-hosted fault zones

Abstract It is common practice to incorporate deterministic transmissibility multipliers into simulation models of siliciclastic reservoirs to take into account the impact of faults on fluid flow, but this is not common practice in carbonate reservoirs due to the lack of data on fault permeability. Calculation of fault transmissibilities in carbonates is also complicated by the variety of mechanisms active during faulting, associated with their high heterogeneity and increased tendency to react with fluids. Analysis of the main controls on fault-rock formation and permeability from several carbonate-hosted fault zones is used to enhance our ability to predict fault transmissibility. Lithological heterogeneity in a faulted carbonate succession leads to a variety of deformation and/or diagenetic mechanisms, generating several fault-rock types. Although each fault-rock type has widely varying permeabilities, trends can be observed dependent on host lithofacies, juxtaposition and displacement. These trends can be used as preliminary predictive tools when considering fluid flow across carbonate fault zones. Fewer mechanisms occur at lower displacements (&lt;30 m), creating limited fault-rock types with a narrow range of low permeabilities regardless of lithofacies juxtaposition. At increased displacements, more fault-rock types are produced at juxtaposition of different lithofacies, with a wide range of permeabilities.

Friction and scale-dependent deformation processes of large experimental carbonate faults

We studied the frictional behaviour and deformation products of large (20 cm × 20 cm bare surfaces) experimental limestone faults. We sheared samples in a direct shear configuration, with an imposed normal force of 40–200 kN and shear velocity of 10 μm/s. The steady-state shearing of these surfaces yielded a coefficient of friction 0.7<μ<1 (average μ∼0.9), significantly higher than gouge friction of the same material, μ∼0.6. Frictional healing, studied via slide-hold-slide tests, is null (Δμ≤0 upon re-shear). Moreover, sliding of these surfaces is accompanied by dilatation and production of grooves, gouge striations and fault mirrors. These products are entirely analogous to slip surface phenomena found on natural limestone-bearing faults at both the macroscale and at the microscale. We infer that high friction, accompanied by dilatant deformation, and null frictional healing are the macroscopic effect of brittle damage on the sliding surface, constrained by the strength of the rock and by fast healing processes in the gouge. Simultaneously to brittle failure, plastic deformation occurs on the sliding surface and inside the intact rock via nanoparticle formation (mirrors) and twinning at the micron scale. Because of the similarity between experimental and natural structures, we suggest that sliding of carbonate-bearing faults in the uppermost crust could be characterized by high friction, fast healing and strongly dilatant deformation, which would help to explain shallow seismicity frequently documented in carbonatic terrains such as the Northern Apennines of Italy.