Intergranular Pressure Solution Research Articles

Frictional behaviour of simulated quartz fault gouges under hydrothermal conditions: Results from ultra-high strain rotary shear experiments

Numerous experimental studies have been conducted to explore the mechanical behaviour and strength properties of rock materials. Most of these studies, however, do not take the effects of fluids into account, though it has long been recognized that fluids might play an important role in the deformation of crustal rocks under brittle–ductile conditions. Moreover, all these studies are limited in the total shear strain that could be reached. In this study we report on ultra-high strain experiments performed on simulated quartz fault gouges in a rotary shear apparatus under hydrothermal conditions (effective normal stresses of 20–100 MPa, a fluid pressure of 200 MPa, temperatures of 400–600 °C, sliding velocities of 0.01–1 μm/s and total shear strains up to 50). The experiments show strain hardening up to a shear strain γ of 0.6–1.8, followed by strain weakening of up to 30% towards a steady state value at a strain γ of ∼ 8–12. This strain weakening effect is much higher than previously reported for quartz gouge. The steady state shear strength increases with decreasing grain size, increasing sliding velocity, and decreasing temperature. The microstructure of the deformed quartz gouge is characterized by the presence of a through-going boundary-parallel Y-shear. Some samples also show Riedel shears oriented oblique to the shear zone boundary. Deformation in these tests was largely by cataclastic processes, with most displacement being accommodated along the boundary-parallel Y-shear, causing the marked weakening observed. Intergranular pressure solution did not accommodate significant shear strain but appears to play a role in smoothing and weakening the localized slip surface and in controlling gouge compaction.

Intergranular pressure solution in internally wetted polycrystals: Effect of additives

Wetting of grain boundaries in polycrystalline materials leads to considerable changes in their physicochemical and mechanical properties. Under a constant compressive load, internally wetted materials display an enhanced deformability; creep rate increases sometimes by several orders of magnitude. The dominant creep mechanism is known as dissolution–precipitation or pressure solution; a stress-induced excessive chemical potential provides a driving force for dissolution of material within grain contacts, diffusion through the grain boundary solution film and re-precipitation elsewhere. Sensitivity of pressure solution rate to the chemical composition of the intergranular liquid was reported earlier, but the underlying mechanisms were poorly understood. In the present work, the creep experiments were carried out on poly- or monocrystalline sodium chloride in the presence of NaCl aqueous solution (pure or containing additives such as copper, magnesium and lead chlorides, K 4Fe(CN) 6 and urea). In all cases, pressure solution has been shown to be the main deformation mechanism. Creep rate decreases in the presence of additives which are known to affect the dissolution and growth processes of sodium chloride or its concentration in the brine. Rate-limiting stage (dissolution or diffusion) in various environments has been identified.

Influence of time, temperature, confining pressure and fluid content on the experimental compaction of spherical grains

Theoretical models of compaction processes, such as for example intergranular pressure-solution (IPS), focus on deformation occurring at the contacts between spherical grains that constitute an aggregate. In order to investigate the applicability of such models, and to quantify the deformation of particles within an aggregate, isostatic experiments were performed in cold-sealed vessels on glass sphere aggregates at 200 MPa confining pressure and 350 °C with varying amounts of fluid. Several runs were performed in order to investigate the effects of time, fluid content, pressure and temperature, by varying one of these parameters and holding the others fixed. In order to compare the aggregates with natural materials, similar experiments were also performed using quartz sand instead of glass spheres. Experiments with quartz show evidence of IPS, but the strain could not be quantified. Experiments with glass spheres show evidence of several types of deformation processes: both brittle (fracturing) and ductile (plastic flow and fluid-enhanced deformation, such as IPS). In experiments with a large amount of water (≥ 5 vol.%), dissolution and recrystallization of the glass spheres also occurred, coupled with crystallization of new material filling the initial porosity. Experiments performed with a fluid content of less than 1 vol.% indicate creep behavior that is typical of glass deformation, following an exponential law. These experiments can also be made to fit a power law for creep, with a stress exponent of n = 10.5 ± 2.2 in both dry and wet experiments. However, the pre-factor of the power law creep increases 5 times with the addition of water, showing the strong effect of water on the deformation rate. These simple and low-cost experiments provide new insights on the rheology of soda-lime glass, which is used in analogue experiments, and of glass-bearing rocks under mid-crustal P– T conditions. They also highlight the strong enhancement of plasticity of natural rocks in presence of fluid or of a glassy phase.

Enhanced deformation of limestone and sandstone in the presence of high fluids

Geological repositories subject to the injection of large amounts of anthropogenic carbon dioxide will undergo chemical and mechanical instabilities for which there are currently little experimental data. This study reports on experiments where low and high (8 MPa) aqueous fluids were injected into natural rock samples. The experiments were performed in flow‐through triaxial cells, where the vertical and confining stresses, temperature, and pressure and composition of the fluid were separately controlled and monitored. The axial vertical strains of two limestones and one sandstone were continuously measured during separate experiments for several months, with a strain rate resolution of 10−11 s−1. Fluids exiting the triaxial cells were continuously collected and their compositions analyzed. The high fluids induced an increase in strain rates of the limestones by up to a factor of 5, compared to the low fluids. Injection of high fluids into the sandstone resulted in deformation rates one order of magnitude smaller than the limestones. The creep accelerating effect of high fluids with respect to the limestones was mainly due to the acidification of the injected fluids, resulting in a significant increase in solubility and reaction kinetics of calcite. Compared to the limestones, the much weaker response of the sandstone was due to the much lower solubility and reactivity of quartz in high fluids. In general, all samples showed a positive correlation between fluid flow rate and strain rate. X‐ray tomography results revealed significant increases in porosity at the inlet portion of each core; the porosity increases were dependent on the original lithological structure and composition. The overall deformation of the samples is interpreted in terms of simultaneous dissolution reactions in pore spaces and intergranular pressure solution creep.

Intergranular pressure solution in chalk: a multiscale approach

This paper outlines a multiscale approach for modelling of chemo-mechanical interaction in chalk. The primary focus is on quantitative micromechanical analysis of dissolution/diffusion phenomena that occur within the intergranular interface. First, the influence of the kinetics of the dissolution process on the underlying physical mechanisms is investigated. Subsequently, a macroscopic chemo-plasticity formulation is outlined. Extensive numerical studies are carried out. Those include the analysis at micro-level, simulation of macroscopic creep deformation characteristics as well as application in a boundary value problem that involves a water injection test.

Effects of phosphate ions on intergranular pressure solution in calcite: An experimental study

Intergranular pressure solution (IPS) is a coupled chemical-mechanical process of widespread importance that occurs during diagenesis and low-temperature deformation of sedimentary rocks. Laboratory experiments on IPS in halite, quartz, and calcite have largely concentrated on the mechanical aspects of the process. In this study, we report the effects of pore fluid chemistry, specifically varying phosphate ion concentration, on the mechanical compaction by IPS of fine-grained calcite powders at room temperature and 1 to 4 MPa applied effective stress. Phosphate was investigated because of its importance as a biogenic constituent of sea and pore waters. Increasing the pore fluid phosphate concentration from 0 to 10 −3 mol/L systematically reduced compaction strain rates by up to two orders of magnitude. The sensitivity of the compaction strain rate to phosphate concentration was the same as the sensitivity of calcite precipitation rates to the addition of phosphate ions reported in the literature, suggesting that the rate of IPS in phosphate-bearing samples was controlled by calcite precipitation on pore walls. The results imply that IPS and associated porosity/permeability reduction rates in calcite sediments may be strongly reduced when pore fluids are enriched in phosphates, for example, through high biologic productivity or a seawater origin. Future modeling of IPS-related processes in carbonates must therefore take into account the effects of pore fluid chemistry, specifically the inhibition of interfacial reactions.

Numerical Modeling of the Effect of Carbon Dioxide Sequestration on the Rate of Pressure Solution Creep in Limestone: Preliminary Results

When carbon dioxide (CO2 ) is injected into an aquifer or a depleted geological reservoir, its dissolution into solution results in acidification of the pore waters. As a consequence, the pore waters become more reactive, which leads to enhanced dissolution-precipitation processes and a modification of the mechanical and hydrological properties of the rock. This effect is especially important for limestones given that the solubility and reactivity of carbonates is strongly dependent on pH and the partial pressure of CO2 . The main mechanism that couples dissolution, precipitation and rock matrix deformation is commonly referred to as intergranular pressure solution creep (IPS) or pervasive pressure solution creep (PSC). This process involves dissolution at intergranular grain contacts subject to elevated stress, diffusion of dissolved material in an intergranular fluid, and precipitation in pore spaces subject to lower stress. This leads to an overall and pervasive reduction in porosity due to both grain indentation and precipitation in pore spaces. The percolation of CO2 -rich fluids may influence on-going compaction due to pressure solution and can therefore potentially affect the reservoir and its long-term CO2 storage capacity. We aim at quantifying this effect by using a 2D numerical model to study the coupling between dissolution-precipitation processes, local mass transfer, and deformation of the rock over long time scales. We show that high partial pressures of dissolved CO2 (up to 30 MPa) significantly increase the rates of compaction by a factor of ~50 to ~75, and also result in a concomitant decrease in the viscosity of the rock matrix.

Experimental pressure solution compaction of synthetic halite/calcite aggregates

Experimental observations are reported of weakening of sediment-like aggregates by addition of hard particles. Sieved mixtures of calcite and halite grains are experimentally compacted in drained pressure cells in the presence of a saturated aqueous solution. The individual halite grains deform easily by pressure solution creep whereas calcite grains act as hard objects and resist compaction. The fastest rate of compaction of the mixed aggregate is not obtained for a 100% halite aggregate but for a content of halite grains between 45% and 75%. We propose that this unusual compaction behavior reflects the competition between two mechanisms at the grain scale: intergranular pressure solution at grain contacts and grain boundary healing between halite grains that prevent further compaction.

Diffusive properties of fluid-filled grain boundaries measured electrically during active pressure solution

Diffusion through ‘wetted’ grain boundaries is often the rate limiting process during rock deformation by intergranular pressure solution. However, the underlying processes operative within such boundaries are poorly understood. In this contribution we have studied the diffusive properties of wetted grain boundaries by measuring the electrical resistivity of single, annular halite–glass contacts undergoing active pressure solution. Optical observation shows continuous growth (i.e. widening) of the annular contacts by pressure solution. From the resistivity measurements and making use of the Nernst–Einstein equation, it was possible to calculate the apparent grain boundary diffusion coefficient Z= DδC (i.e. the product of grain boundary diffusion coefficient D, grain boundary film thickness δ and the solubility C of the diffusing species in the grain boundary fluid) during the pressure solution process. The Z-values obtained lie in the range 3×10 −20–2×10 −18 m 3/s, show an inverse dependence on normal stress ( σ n) and agree well with values inferred previously from single contact and polycrystalline compaction experiments.

Compaction creep of quartz sand at 400–600°C: experimental evidence for dissolution-controlled pressure solution

Intergranular pressure solution (IPS) is an important compaction and deformation mechanism in quartzose rocks, but the kinetics and rate-controlling process remain unclear. The aim of the present study is to test microphysical models for compaction creep by IPS against isostatic hot pressing experiments performed on quartz sand under conditions expected to favor pressure solution (confining pressure 300 MPa, pore water pressure 150–250 MPa, temperature 400–600°C). Microstructural observations revealed widespread intergranular indentation features and confirmed that intergranular pressure solution was indeed the dominant deformation mechanism under the chosen conditions. For porosities down to 15%, the mechanical data agree satisfactorily with a microphysical model incorporating a previously determined kinetic law for dissolution of loose granular quartz, suggesting that the rate-limiting mechanism of IPS was dissolution. The model also predicts IPS rates within one order of magnitude of those measured in previous experiments at 150–350°C, and thus seem robust enough to model sandstone compaction in nature. Such applications may not be straightforward, however, as the present evidence for dissolution control implies that the compositional variability of natural pore fluids may strongly influence IPS rates in sandstones.

Compaction experiments on wet calcite powder at room temperature: evidence for operation of intergranular pressure solution

Abstract Dead weight uniaxial compaction creep experiments were carried out on fine-grained, super-pure calcite (<74 μm) at room temperature and applied effective stresses of 1–4 MPa. All samples were pre-compacted dry at a stress of 8 MPa, for 30 minutes, to obtain a well-controlled initial porosity. The samples were then wet-compacted under ‘drained’ conditions with pre-saturated solution as pore fluid. Control experiments, which were done either dry or with chemically inert pore fluid, showed negligible compaction. However, samples tested with saturated solution as pore fluid showed easily measurable compaction creep. The compaction strain rate decreased with increasing strain and increasing grain size, and increased with increasing applied stress. Addition of Mg 2+ ions to the saturated solution dramatically inhibited compaction. From the literature, Mg 2+ ions are known to inhibit calcite precipitation. By comparison with a theoretical model for intergranular pressure solution in calcite, the observed mechanical behaviour and the way that compaction responded to the pore fluid chemistry suggest that, under our experimental condition, intergranular pressure solution is the mechanism of the deformation and that precipitation is likely to be the rate-limiting step.

Construction of an intergranular volume compaction curve for evaluating and predicting compaction and porosity loss in rigid-grain sandstone reservoirs

To evaluate compaction as a factor in porosity evolution, a plot of intergranular volume vs. depth was constructed using data from relatively uncemented reservoir sandstones from a variety of depths, ages, and geographic locations. The resulting intergranular-volume-decline curve reveals that sands compact mechanically and intergranular volume declines rapidly, from about 40 to 42% at the surface, to about 28% at 1500 m. Between about 1500 and 2500 m, intergranular volume continues to decline slowly, until the framework stabilizes at around 26% (maximum potential porosity in the absence of cement or matrix). No further significant decrease in intergranular volume is observed to the depth limits of the data set at 6700 m. Comparison of intergranular volume and volume of quartz cement for different formations reveals no obvious balance between intergranular pressure solution (as monitored by intergranular volume) and quartz cementation. This indicates that grain-to-grain pressure solution and quartz cement precipitation do not proceed concomitantly on the thin-section scale. Moreover, grain compaction is limited (to about 26% intergranular volume) in rigid-grain sandstones, which suggests that the occurrence and distribution of deep porosity is a function of the volume of cement available to fill the intergranular pores. Therefore, deep, porous sandstones are relatively uncemented rather than undercompacted.

Compaction creep of quartz-muscovite mixtures at 500°C: Preliminary results on the influence of muscovite on pressure solution

Abstract It is widely claimed that the presence of phyllosilicates in sandstones increases intergranular pressure solution (IPS) rates in these rocks. However, this has not been experimentally confirmed. This study reports the results of isostatic hot-pressing compaction experiments at a temperature of 500°C and an effective pressure of 100 MPa on mixtures of quartz and muscovite. Previous work has shown that under these conditions dissolution is rate controlling in pure quartz. No acceleration of compaction rates of quartz by the addition of muscovite was observed. Instead, a modest decrease in compaction rates was observed (factor 3–10), which we infer was due to a decrease in IPS rate. The effect of muscovite in slowing IPS may be due to the influence of dissolved aluminum (Al 3+ ) dominating over any accelerating effects of alkali-metal cations. From the geochemical literature, Al 3+ in solution is expected to decrease the solubility, dissolution rates and precipitation rates of quartz. However, the effect of the addition of muscovite on IPS rates in quartz when controlled by diffusion or precipitation may be different. Experiments should be conducted on quartz sand under conditions where diffusion or precipitation is rate controlling to investigate these possible effects.

Solid–fluid phase transformation within grain boundaries during compaction by pressure solution

The overall compaction of porous rocks due to intergranular pressure solution (IPS) results from the dissolution of minerals within contact regions and the diffusive transport through the grain boundary of the dissolved species towards the fluid-filled pore space. The grain boundary structure can be imagined to be composed of dry contact zones, thin fluid films and fluid-filled cavities. The connectiveness and tortuosity of this structure determine the effective diffusivity of grain contacts and thus the potential of porous rock to compact by the action of IPS. The evolution in time of the grain-boundary structure, and thus of the effective diffusivity, is discussed here with the help of two 2D initial- and boundary-value problems which are solved by analytical and numerical means. The evolution of the solid–fluid interfaces within the grain boundary is governed by a phase transformation between the non-hydrostatically stressed elastic solid and the trapped fluid assumed in mechanical equilibrium. The characteristic time is provided by a linear kinetic law. The evolution of the structure away from a state of thermodynamic equilibrium during a loading normal to the grain boundary is found to occur in two steps. The first one consists of a diffuse morphology evolution in time and results in an enhancement of any initial stress concentration. The second step is characterized by a rapid and localized dissolution in the region of stress concentration. The latency period prior to localization is governed by the magnitude of the non-hydrostatic remote stress as well as the microstructural geometric factor responsible for the initial stress concentration at the solid–fluid interface. The localized dissolution is shown to provide a mechanism for the fluid to penetrate a previously dry contact region by marginal dissolution and thus to create a fluid film. However, the newly formed thin fluid layer is found to be unstable pointing to a possible repeated reorganization or dynamic evolution of the grain boundary internal structure during the action of IPS.

Kinetics of crack-sealing, intergranular pressure solution, and compaction around active faults

Geological evidence indicates that fluids play a key role during the seismic cycle. After an earthquake, fractures are open in the fault and in the surroundings rocks. With time, during the interseismic period, the permeability of the fault and the country rocks tends to decrease by gouge compaction and fracture healing and sealing. Dissolution along stylolite seams provides the matter that fills the fractures, whereas intergranular pressure solution is responsible for gouge compaction. If these processes are fast enough during the seismic cycle, they can modify the creep properties of the fault. Based on field observations and experimental data, we model the porosity decrease by pressure solution processes around an active fault after an earthquake. We arrive at plausible rates of fracture sealing that are comparable to the recurrence time for earthquakes. We also study the sensitivity of these rates to various parameters such as grain size, fracture spacing, and the coefficient of diffusion along grain boundaries and stylolites.

Kinetics of precipitation of gypsum and implications for pressure‐solution creep

In order to model the role of gypsum in crustal deformation and in trapping hydrocarbons, a quantitative, mechanism‐based understanding of the deformation and compaction behaviour of gypsum is needed. Previous laboratory experiments indicate that intergranular pressure solution is an important deformation mechanism in gypsum and may be controlled by the kinetics of gypsum precipitation. To examine this further, the growth kinetics of gypsum were investigated using seed crystals and super‐saturated aqueous solutions prepared from natural gypsum powders. The results showed both nucleation and growth dominated behaviour. Results relating purely to seed (over)growth showed that at low driving forces (<1 kJ/mole) precipitation follows a second order growth law, while at larger driving forces the order is 3–4. The growth rates are 1 to 2 orders of magnitude slower than those reported in studies on pure systems. However, pressure‐solution creep rates, predicted by coupling the present growth data with a microphysical model for pressure solution, are 1 to 2 orders of magnitude too fast to be consistent with experimentally obtained creep rates. On the other hand, the predicted and measured creep rates show an almost identical dependence on applied stress and grain size, supporting the hypothesis that pressure‐solution creep in gypsum is controlled by the kinetics of precipitation.

Porosity Loss, Fluid Flow, and Mass Transfer in Limestone Reservoirs: Application to the Upper Jurassic Smackover Formation, Mississippi1

Ooid grainstones of the Upper Jurassic Smack over Formation are buried to a depth of over 6 km and exposed to temperatures in excess of 200°C at Black Creek field, Mississippi. Combined effects of mechanical compaction, intergranular pressure solution, and cementation have reduced intergranular porosity of these ooid grainstones to 0%, indicating that porosity reduction has gone to completion. Modal analysis of 24 samples lacking preburial cements indicates that from the original 40% porosity, 13 porosity units (range: 4 to 21) were lost by mechanical compaction, 15 porosity units (range: 8 to 23) were reduced by intergranular pressure solution, and 12 porosity units (range: <1 to 26) were destroyed by cementation. Intergranular pressure solution caused an average of 28% (range: 15 to 51%) vertical shortening in Smackover ooid grainstones. Under ideal conditions, the 28% vertical shortening will generate enough calcium carbonate to precipitate 10% calcite cement. This is close to the measured volume of cements in Smackover grainstones (12%), suggesting that intergranular pressure solution provided most of the calcite cement present. No external sources of calcium carbonate are required. Fine-grained samples that experienced high degrees of intergranular pressure solution and contain only small amounts of cement occur at the top of the reservoir, whereas coarse-grained samples with abundant cement and low degrees of pressure solution occur in the middle and basal parts of the reservoir, suggesting that the fine-grained intervals acted as sources and the coarse-grained intervals as sinks for calcium carbonate. Mass transfer of pressure solution-generated calcium carbonate from the top of the unit to precipitation sites in the middle and basal parts of the reservoir could have occurred by a non-Rayleigh-type convection cell. Due to calcite's reverse solubility with respect to temperature, the cooling, upward-moving limb of the convection cell would become progressively more undersaturated, and hence able to transport more dissolved calcium carbonate released by intergranular pressure solution in the upper portion of the reservoir. Pore fluids descending in the downward-moving limb of the cell would become progressively more supersaturated, and calcium carbonate would tend to precipitate as cement in the middle and basal parts of the reservoir as fluids become progressively hotter.

Intergranular Pressure Solution in Nacl: Grain-To-Grain Contact Experiments under the Optical Microscope

Intergranular Pressure Solution (IPS) is an important geologic lithification, compaction and deformation mechanism in a wide variety of crustal rocks. Experimental studies of IPS in quartz aggregates have not been very successful due to the low rate of IPS, and IPS experiments performed using wet halite as a rock analogue (Spiers and Schutjens, 1990; Hickman and Evans, 1991) have left uncertainty about the detailed IPS mechanism and grain contact structure/wetting in this material. The present study reports four contact dissolution experiments performed under the optical microscope to study the mechanism and kinetics of IPS at single halite/halite and halite/glass contacts loaded under brine (room temperature). Normal constant contact forces in the range 1. 0 to 2. 6 N were applied in the presence of NaCl-saturated brine, exerting stresses of 0. 8 to 7. 4 MPa. Time-dependent mass removal and convergence were observed at all contacts. In all cases, loading of the contact (or increasing the load on the contact) led to instantaneous formation of a rough contact morphology, composed of a crystallographically-controlled pattern of islands and channels with a length scale of several micrometers. This nonequilibrium microstructure evolved with time to an optically flat contact face while contact broadening and convergence continued. The smoothing/convergence process must therefore have involved diffusion of mass out of the contact, and expulsion of brine, through a connected brine phase within the contact. Whether a fine-scale rough structure persisted in contacts which evolved to optical flatness is not known, though post-test SEM (Scanning Electron Microscopy) observations suggest that it may have. If so, its amplitude was less than 500 nm. Measurements of dissolution rates enabled comparison with a model for IPS. The analysis suggests that solute diffusion through the contact boundary was probably rate-controlling, with the contact structure and effective diffusivity varying with contact force and on-going convergence. The results agree broadly with those of previous compaction creep experiments performed using wet halite powder. Discrepancies with other workers results for single-contact dissolution experiments can be explained in terms of differences in experimental configuration and competition between driving forces.

Timing of Compaction and Quartz Cementation from Integrated Petrographic and Burial-History Analyses, Lower Cretaceous Fall River Formation, Wyoming and South Dakota

ABSTRACT Integrated petrographic and burial-history studies of Fall River sandstones from outcrop and the subsurface provide insight into the timing of compaction and quartz cementation, the two main porosity-reducing processes in quartzose sandstones. Petrographic study of 95 thin sections of Fall River fluvial valley-fill sandstones from outcrop, Donkey Creek field at 2 km burial depth, and Buck Draw field at 3.8 km indicates that reservoir quality differs significantly in these three areas. Fall River sandstones at the surface contain an average of 31% intergranular volume (IGV) and 2% quartz cement. In both Donkey Creek and Buck Draw fields, the sandstones average 22% IGV, but quartz-cement volume averages 8% in the shallower field and 12% in the deeper. Geometric mean permeability at the urface is 4700 md, compared with 42 md at 2 km and 2 md at 3.8 km. Burial history of the Fall River sandstone differs greatly in the three areas. The outcropping sandstones were buried to 2 km and had reached 80°C by the end of the Cretaceous. They were then uplifted and have remained at near-surface temperatures since the Paleocene; the calculated time-temperature index (TTI) of these sandstones is 1. Fall River sandstones at Donkey Creek were also buried to 2 km and had reached 80°C by the end of the Cretaceous but remained at that depth during the Tertiary; TTI is 14. In Buck Draw field, Fall River sandstones were buried to 2.5 km during the Cretaceous and then continued to subside during the Tertiary, reaching depths of 4 km and temperatures of 140°C; TTI is 512. Much of the compaction of Fall River sandstones had occurred by burial depths of 2 km, but additional time at that depth was required for completion of mechanical compaction and for minor chemical compaction. Although greater depth and higher temperatures did not increase chemical compaction, increasing thermal maturity resulted in more quartz cementation. Internal sources of silica from stylolitization and intergranular pressure solution account for only 10-25% of the volume of quartz cement in Fall River sandstones. Imported silica may have come from clay-mineral transformations in Cretaceous shales. Loss of porosity and permeability was greatest between TTI of 1 and 14 but continued, at a reduced rate, as TTI increased.

A model for intergranular pressure solution in open systems : F. K. Lehner, Tectonophysics, 245(3–4), 1995, pp 153–170

A model for intergranular pressure solution in open systems : F. K. Lehner, Tectonophysics, 245(3–4), 1995, pp 153–170