Growth Of Siderite Research Articles

(Digital Presentation) The Role of Steel Microstructures on Sweet Corrosion Scaling By in Situ Confocal Raman

Confocal Raman imaging and spectroscopy has been used in a custom-made flow-cell to map in-situ spatial and temporal growth of siderite and chukanovite on pipeline steel in a hot brine environment, under conditions typical of commercial interest (pH 6.8, temp 80oC, oxygen conc < 10 ppb, 0.5 M NaCl, open circuit potential (OCP)). Ferrite and pearlite domains are found to exhibit an interesting contrast (colour) inversion under sweet environmental conditions compared to their Nital etched contrast – confirmed by identifying the shapes and surrounding of the domains before and after exposure to two different conditions. Ferrite and pearlite phases are found to exhibit differing evolution of the corrosion scale mineralogy, and phase transformation. The process starts by revealing the microstructural phase constituents, significantly the interphase boundaries are identified as the primary sites for scale formation. The ferritic phase forms pure siderite scale while the pearlitic phase shows both siderite and chukanovite scales, with chukanovite transforming into siderite over time. LPR profiles reveal that for carbon steel with a higher pearlite fraction the initial corrosion rate is higher, followed by a faster drop when compared to steel with lower pearlite fraction! Figure 1

Kinetic isotope effect in siderite growth: Implications for the origin of banded iron formation siderite

The widespread occurrence of siderite (FeCO3) at Earth's modern surface and in sedimentary rocks has led to its frequent use as a tool for palaeoenvironmental reconstruction. Isotopic studies of siderite associated with Archaean-Palaeoproterozoic banded iron formations show negative δ13C values, which coupled with δ56Fe values, have been considered to support an important role of dissimilatory iron reduction (DIR) in the genesis of iron formations.Facies-specific analyses show that texturally and petrographically syndepositional and/or early diagenetic, finely laminated microsparitic (≤10 µm in diameter) siderite exhibits δ13C between −3 and −7‰. This siderite δ13C range can be interpreted in three ways: (1) precipitation of siderite from dissolved inorganic carbon (DIC) produced by DIR coupled to partial oxidation of organic carbon with δ13C < −25‰, (2) precipitation from a mixed hydrothermal-seawater fluid bearing mantle-derived DIC with δ13C ≅ −6.5‰, and (3) precipitation from seawater-derived DIC and expression of a kinetic isotope effect (KIE) associated with siderite growth.We present the carbon isotopic composition of siderite formed in abiotic seeded growth experiments over a wide range of solution siderite saturation at 25 °C and 1 bar. With a complete set of chemical kinetic data, we develop and apply a model of disequilibrium siderite precipitation to constrain the carbon KIE as a function of growth rate. Sampling of model parameters from distributions that represent uncertainty in the parameter values, we find best-fit values of equilibrium and kinetic fractionation factors: 103lnαeq = −0.2 and 103lnαf = −14.9.These constraints allow us to assess the origins of δ13C values in microsparitic siderite in iron formations. For example, a moderate level of siderite supersaturation (e.g., Ωsid = 100) in the hydrothermal-seawater mixing fluids (source of dissolved iron) would have induced a carbon KIE of ∼−8‰ in fluid-buffered early diagenetic siderite growth; a range that encompasses essentially all negative δ13C values reported from microsparitic siderite in Campbellrand-Kuruman iron formations, Transvaal Supergroup, South Africa. We suggest that a straightforward, abiotic explanation for the range of δ13C values in microsparitic siderite in Archaean-Palaeoproterozoic banded iron formations is pulsed deposition of iron-rich sediments associated with intense hydrothermal activity. Specifically, the siderite-δ13C range is well explained by a partial expression of carbon KIE associated with siderite growth from supersaturated solutions, and from a bottom-water DIC reservoir with near-zero δ13C values (seawater with a possible contribution of mantle carbon).

Sphaerosiderites as sensitive recorders of non‐marine depositional and diagenetic history: Insights from the Lower Cretaceous Wealden Supergroup

AbstractWaterlogged, reducing soils in modern and ancient wetlands feature distinctive syndepositional to early diagenetic spherical iron carbonate concretions, known as sphaerosiderites. Sphaerosiderites are thought to record pore water elemental chemistry and local palaeoenvironmental conditions, and are widely used in palaeohydrological reconstructions throughout the Phanerozoic. The Lower Cretaceous non‐marine Wealden Supergroup of Southern England, deposited in fluvio‐lacustrine settings, contains abundant well‐preserved sphaerosiderites offering an ideal archive for unravelling the geochemistry of ancient non‐marine environments. Sphaerosiderites were characterised via multiple microanalytical techniques (SEM‐EDS, EPMA, XRD, SIMS), and show morphological and compositional heterogeneity (e.g. concentric zones of variably enriched Mn, Ca or Mg, elemental differences between cores and rims) in well‐preserved sphaerosiderites from the Ashdown and Tunbridge Wells Sand formations. The preservation of primary fabrics, lack of post‐burial cements or extensive alteration suggests these sphaerosiderites record primary palaeoenvironmental conditions. By contrast, in the Wadhurst Clay Formation, sphaerosiderites are recrystallised, potentially reflecting wide scale palaeoenvironmental changes (e.g. marine incursions). New experimental constraints on elemental uptake during siderite growth suggests that rather than reflecting pore water elemental chemistry, the elemental heterogeneity in the Wealden sphaerosiderites reflects complex parameters; variations in pH, cation concentrations, DIC, growth rate and siderite saturation state in groundwaters. At a larger scale, morphological and compositional differences between sphaerosiderites from distinct palaeosol horizons record spatial and temporal variability in local hydrogeochemistry. This suggests that the Weald Basin wetlands of the Lower Cretaceous featured a dynamic and periodically fluctuating groundwater table, where sphaerosiderites growing close to the soil surface responded rapidly to variability in physiochemical conditions, consistent with wet and warm conditions suggested by sedimentological evidence and climate model simulations. Similar morphological and compositional variability noted in other Phanerozoic sphaerosiderites suggests analogous processes operated in ancient wetlands, and that sphaerosiderites could provide a crucial tool to understand wetland dynamics in deep time.

Corrosion of High-Strength Carbon Steels in Siderite Supersaturated Water at Near Neutral pH

When carbon steel corrodes in anaerobic carbonated water, and the steel surface area to liquid volume is high, the concentration of ferrous and bicarbonate ions increases rapidly even though the corrosion rate is low. Such solutions with high bicarbonate concentration and a near neutral pH are believed to induce stress corrosion cracking of high-strength carbon steels. This work was conducted to investigate the solid precipitation in siderite supersaturated solutions. It was also an objective to measure the corrosion rate of high-strength carbon steel in solutions with high bicarbonate concentration at pH close to neutral. Preloading the solutions with ferrous ions and bicarbonate made it possible to measure desupersaturation and corrosion rate as function of time. The initial siderite supersaturation was more than 1,000 in the desupersaturation experiments. Despite this, the nucleation and growth of siderite was so slow that the solutions remained supersaturated for 100 h to 500 h at 10°C to 25°C. The ferrous ion concentration decreased from 1,200 mg/kg to 100 mg/kg in less than 24 h at 40°C, but did not reach equilibrium within 250 h. The precipitate was siderite at 5°C to 25°C. At 40°C, the solid was a mixture of siderite and chuckanovite in low salinity water and siderite with dissolved Ca2+ in artificial seawater. The corrosion rate of carbon steel at pH 6.7 to 7.2 at 25°C decreased to less than 0.01 mm/y in 5 h. Siderite precipitated and grew to a thin protective layer at the steel surface. Even though the solutions were highly supersaturated with respect to siderite throughout the experiments, the carbonate layer at the steel surface did not grow to more 5 μm thickness during 250 h to 400 h. The investigated steels were armor wires for flexible pipes. They have an oxide layer at the surface which is an inherent result of the manufacturing process. The presence of these oxides did not impede the formation of protective siderite layer.

Growth kinetics of siderite at 298.15 K and 1 bar

The widespread occurrence of siderite at the Earth’s surface has motivated investigations into the thermodynamic factors controlling its stability for most of the last century. However, despite a new appreciation for multiple Fe(II)-carbonate mineralisation pathways, the rates of siderite growth have not been accurately predicted as a function of solution chemistry. This has impeded a quantitative understanding of myriad geochemical systems, both modern and ancient. To address this issue, we investigated the growth kinetics of synthetic siderite seeds in anoxic closed-system conditions at 298.15 K and 1 bar. On the basis of monitoring the chemical evolution of the bulk solutions over the course of 46 days, our results demonstrate two distinct relationships between kinetic behaviour and solution saturation (Ω) with respect to siderite. These relationships are best explained by chemical affinity-based rate laws that have been extensively applied to the growth kinetics of calcite (a mineral isostructural with siderite). More specifically, the surface area-normalised siderite growth rates (mol·m−2·s−1) display a linear correlation with supersaturation (Ω-1) when Ω≳5, suggesting a growth rate controlled by the transport of ions to the mineral surface (rtr):rtr=10-12.60±0.16(Ω-1)1.057±0.112.At low solution saturation, growth rates are consistent with spiral mechanism-dominated surface reactions (rsr), exhibiting a parabolic correlation with (Ω-1):rsr=10-13.42±0.14(Ω-1)1.868±0.307.These data show that at comparable solution saturation at 25 °C, siderite growth is nearly 7-orders of magnitude slower than that of calcite. These kinetic behaviours imply that most examples of natural Fe(II) supply fluxes (e.g., dissimilatory iron reduction, hydrothermal activity, or dissolution of other Fe(II)-minerals) would only be balanced by siderite precipitation rates at very high supersaturation, or, if the barrier to Fe(II)-carbonate nucleation is surpassed, balanced by episodic fluctuations in precipitation rate in response to Fe(II) accumulation. In combination with kinetic barriers influencing nucleation, this slow growth rate provides a straightforward explanation for the common observation that many anoxic water bodies are persistently supersaturated with respect to siderite, and implies that the precipitation of siderite may be more dynamic than previously appreciated.

Formation of diagenetic siderite in modern ferruginous sediments

Ferruginous conditions prevailed in the world’s deep oceans during the Archean and Proterozoic Eons. Sedimentary iron formations deposited at that time may provide an important record of environmental conditions, yet linking the chemistry and mineralogy of these sedimentary rocks to depositional conditions remains a challenge due to a dearth of information about the processes by which minerals form in analogous modern environments. We identified siderites in ferruginous Lake Towuti, Indonesia, which we characterized using high-resolution microscopic and spectroscopic imaging combined with microchemical and geochemical analyses. We infer early diagenetic growth of siderite crystals as a response to sedimentary organic carbon degradation and the accumulation of dissolved inorganic carbon in pore waters. We suggest that siderite formation proceeds through syntaxial growth on preexisting siderite crystals, or possibly through aging of precursor carbonate green rust. Crystal growth ultimately leads to spar-sized (>50 μm) mosaic single siderite crystals that form twins, bundles, and spheroidal aggregates during burial. Early-formed carbonate was detectable through microchemical zonation and the possible presence of residual phases trapped in siderite interstices. This suggests that such microchemical zonation and mineral inclusions may be used to infer siderite growth histories in ancient sedimentary rocks including sedimentary iron formations.

Anomalously low δ18O values of high-latitude Permo-Triassic paleosol siderite

The most severe extinction in Earth history occurred during a time of extreme climate change, caused in part by a massive release of carbon into the atmosphere. Isotopic measurements of siderite occurring in paleosols during intervals of global warming suggest high-latitude depletions in δ18O of precipitation, often attributed to an amplified hydrologic cycle. Here, Late Permian and Early Triassic paleosol siderite from Alaska, Antarctica, eastern Australia, Siberia, and South Africa indicate similar or greater meridional gradients in siderite δ18O compared to other past warm intervals.An isotope-tracer-enabled version of the Global Environmental and Ecological Simulation of Interactive Systems (GENESIS) general circulation model (GCM) was used to compare to siderite δ18O data. The model, when deriving siderite δ18O at a specified paleoatmospheric CO2 concentration of 12.7× the preindustrial atmospheric level (PAL), matches a small subset of relatively less depleted high-latitude siderites but does not produce the conditions necessary to explain the most depleted siderite δ18O values. Siderite has been thought to record mean annual precipitation δ18O, though this study suggests that many may not. A seasonal bias, where siderite growth occurs in the summertime in wetlands that receive most of their recharge from melting winter precipitation, may be responsible. GENESIS indicates soil moisture recharge during the spring ahead of the rainy season for high-latitude Permo-Triassic (PT) siderite localities that reach below freezing winter temperatures. Drainage from high altitude regions throughout the growing season may also be responsible. Biological cloud feedbacks and monsoon-related amount effects are not likely the cause for low siderite δ18O because the enrichment of water vapor δ18O associated with warming is too significant.

Time-Resolved in Situ Raman Spectroscopy of the Nucleation and Growth of Siderite, Magnesite, and Calcite and Their Precursors

The nucleation and growth processes of particles and crystals from aqueous systems are actively investigated and occasionally open to debate because multistep nucleation and prenucleation events often exist. This study demonstrates that time-resolved Raman spectroscopic measurements can provide complementary and useful information on the nucleation and growth of particles and crystals from homogeneous and heterogeneous systems at different pressure–temperature conditions. Three minerals were chosen for this study: siderite, magnesite, and calcite, three carbonate minerals that are widespread in geological environments and have numerous industrial and medical applications. As expected, siderite and calcite can rapidly form via an amorphous precursor when using concentrated solutions of reactants directly mixed at ambient temperature (∼25 °C) and pressure (∼1 bar) (i.e., via spinodal decomposition or when energetic barrier is close to zero). In addition, calcium carbonate clusters and/or probably also amorp...

What effect does siderite crystal growth have on chlorides and potential information within the corrosion products of archaeological iron artefacts?

In anoxic, carbonated and slightly acidic burial environments, the growth of siderite crystals on archaeological iron has been attributed a passivating effect on the corrosion process. By creating a simplified, though similar environment (optimized for siderite growth), the aim of this project was to observe how the growth of siderite crystals within the corrosion crust of archaeological iron objects would affect both the corrosion crust and its chloride content.

In Situ Synchrotron X-Ray Diffraction Studies of CO2Corrosion of Carbon Steel with Scale Inhibitors ATMPA and PEI at 80°C

In situ synchrotron x-ray diffraction was used to investigate experimentally the effect of two common scale inhibitors, amino trimethylene phosphonic acid (ATMPA) and polyethyle-neimine (PEI), on the corrosion rate and protective scale formation process during carbon dioxide (CO2) corrosion of carbon steel. These experiments were performed under mild anodic polarization in sodium chloride (NaCl) solutions at ~1 bar CO2, 80°C, and pH 6.5, such that a protective scale would form readily in the absence of any organic scale inhibitors. These results were compared with longer-term open-circuit weight-loss corrosion tests in similar conditions but at up to 30 bar CO2. The scale inhibitors had complex, concentration-dependent effects but in general had a very significant inhibitory effect on the nucleation and growth of siderite (FeCO3), and as a consequence resulted in an increased corrosion rate. The results of pulsed galvanostatic experiments were consistent with the scale inhibitors acting by adsorption onto...

Synthesis of siderite microspheres and their transformation to magnetite microspheres

Carbonates are among the most ubiquitous minerals in nature and are of significant interest in the geology and materials sciences communities, but studies concerning iron carbonate (i.e., siderite) mineralization processes and morphogenesis are less well developed. In this paper, we describe an environmentally benign biomolecule-assisted hydrothermal synthesis strategy to obtain siderite spherulites. Our results show that the formation of siderite microspheres is a successive multistep growth process involving a rod!peanut!dumbbell!sphere transition, which is driven by the intrinsic electric forces of siderite crystallites. Addition of the biomolecule ascorbic acid not only prevents Fe 2þ oxidation in the alkaline solution environment but also modifies the growth of siderite. Moreover, with increasing Fe 2þ concentrations, siderite nanoparticles or nano-sized triangular pyramids appear one after the other on the preformed spherical surfaces, resulting in different surface textures of the siderite microspheres. The surface morpho- logical modifications of the siderite microspheres can be attributed to the secondary nucleation and overgrowth of siderite nanocrystals. The siderite microspheres so obtained were then used as solid precursor minerals to form secondary magnetite through oxygen-limited thermolysis at 300 � C. The thermolysis experiments demonstrate the possibility that the size and morphology of secondary magnetite particles are influenced by the precursor siderite, suggesting that magnetite microcrystals with elongated or other uncommon morphologies in nature may potentially inherit the antecedent morphologies of Fe-carbonate-bearing minerals. Moreover, measurements of the magnetic properties of magnetite products after thermolysis show that the saturation magnetizations (Ms) of three kinds of magnetite microspheres are 52.5, 62.8 and 78.6 emu/g, which vary according to increasing Fe 2þ concentrations used in the synthesis of the precursor siderite.

Diagenesis of fossil ostracods: Implications for stable isotope based palaeoenvironmental reconstruction

A protocol for assessing the diagenetic alteration of ostracod carapaces for use in palaeoenvironmental reconstruction is proposed, based on comparison between fossil (Carboniferous) and recent specimens. Recent ostracods have a carapace ultrastructure of fine (< 0.5 μm diameter) crystals of primary low-magnesium calcite. The degree of recrystallisation in fossil ostracods is assessed based on the carapace ultrastructure and geochemistry. Six diagenetic stages are identified: 1, replacement of the original finely crystalline calcite carapace with neomorphic calcite; 2, framboidal and euhedral pyrite growth; 3, ferroan calcite carapace replacement and cavity (void) filling cement; 4, ferroan dolomite carapace replacement and void fills; 5, siderite growth; and 6, sphalerite and barite mineralisation. Stage 1 occurs during early shallow burial, stages 2–3 soon after, and stages 4–6 during much later burial (possibly hydrothermal) alteration. Ostracods and macrofossils exhibiting diagenetic stages 1–5 were analysed for oxygen and carbon isotope ratios. The oxygen isotope compositions clearly reflect the diagenetic stages. The most negative oxygen isotopes (δ 18O − 12.9‰) represent the precipitation of ferroan dolomite (Stage 4), and the most positive values of the neomorphic calcite (δ 18O − 0.9‰) represent Stage 1, and are within the predicted range of Carboniferous seawater (δ 18O − 4‰ to 0‰). The diagenetic protocol established here is specific to Palaeozoic fossil ostracods from carbonate and clastic sediments that were subject to shallow burial diagenesis and later hydrothermal alteration. Nevertheless, the approach could be used to assess the utility of fossil ostracods for palaeoenvironmental interpretation from a wide range of geological settings.

Experimental evaluation of mixed fluid reactions between supercritical carbon dioxide and NaCl brine: Relevance to the integrity of a geologic carbon repository

The reactive behavior of a mixed fluid (supercritical CO 2 and brine) under physical–chemical conditions relevant to geologic storage and sequestration in a carbon repository is largely unknown. Experiments were conducted in a flexible cell hydrothermal apparatus to evaluate fluid–rock (aquifer plus aquitard) reactions that may adversely impact the integrity of the repository. A 5.5 molal NaCl brine–rock system was held at 200 °C and 200 bars (20 MPa) for 32 days (772 h) to approach steady state, then injected with CO 2 and allowed to react for an additional 45 days (1079 h). In a separate experiment at 200 °C and 200 bars, the system was allowed to react for 77 days (1845 h) without injection of CO 2. Corroded magnesite and euhedral siderite crystallized in a paragenetic sequence after CO 2 injection. Nucleation and growth of siderite on shale suggests the aquitard is a reactive component in the system. Changes in elemental abundances in the brine following addition of CO 2 include pH decrease and depletion of sodium due to accelerated growth of analcime. A pH increase follows pressure and temperature decrease and loss of saturated CO 2 from acidic brine. Silica concentrations and dissolution rates are enhanced and silica precipitation inhibited in the acidic brine. Geochemical reactions in a carbon repository extend beyond pH decrease and carbonate mineral precipitation. Rock-dominated reaction systems yield to acid-dominated and related reactions controlled by mixed fluid equilibria (i.e., a fluid-dominated system). Escape of CO 2 or migration of brine from the repository into overlying aquifers may cause silica super-saturation and increased alkalinity due to mixed fluid phase equilibria. These geochemical changes could be monitored in aquifers as indicators of repository integrity. Return of silica super-saturated brine to a rock-dominated reaction system buffered to neutral pH conditions may enhance precipitation of quartz, chalcedony, or amorphous silica. In addition to the potential effects (beneficial or deleterious) that silica super-saturation and precipitation may hold for repository performance, an understanding of the effects of multi-phase equilibrium relationships between supercritical CO 2 and dissolved silica in aquifer–brine systems also raises new questions for a variety of geologic systems. Multi-phase fluid equilibria may, for example, account for quartz cements in some sedimentary basin sandstones and quartz vein mineralization in some ore districts.

Oblique magnetic fabric in siderite-bearing pelitic rocks of the Upper Carboniferous Culm Basin, SW England: an indicator for palaeo-fluid migration?

Abstract A zone of siderite dominated magnetic fabrics is recognized within clastic argillaceous rocks of the southern part of the Upper Carboniferous Culm foreland basin of SW England. This zone was identified by measuring the anisotropy of magnetic susceptibility (AMS) before and after heat treatment of samples. A detailed investigation of a recumbent fold structure within this zone (at the well-known Crackington Haven locality) reveals the pre-folding nature of siderite formation. The restored κ max axes of AMS-ellipsoids plot on a segment of a small circle, with a mean inclination of c. 45° to the pole of the sedimentary bedding planes. This oblique magnetic fabric geometry is considered to reflect substrate-controlled siderite growth within a migrating fluid medium, which crystallized during diagenesis and the early stages of Variscan compression. The regional distribution of siderite growth, in combination with the directional information from the AMS, is discussed as an indicator for the palaeo-flow direction of diagenetic fluids within a foreland basin setting.

Green opals in hydrothermalized basalts (Tenerife Island, Spain): alteration and aging of silica pseudoglass

Green opals have been identified in veins and vugs in hydrothermalized basalts from the area of Taganana (Tenerife). The aim of this paper is to document the petrology and geochemistry of these opals and to describe the formation process from amorphous components. Green opals were studied using optical microscopy, powder X-ray diffraction, electron microprobe, atomic absorption spectroscopy and induced coupled plasma mass spectrometer. Our textural and X-ray powder diffraction analyses indicate that green opals are composed of a major groundmass fraction of crystalline (opal CT and celadonite) and amorphous components (opal A and Fe-(hydro)oxides), which host minor siderite and dolomite crystals. The results indicate green opals were formed during the hydrothermal process from a Fe-rich silica amorphous phase (pseudoglass) which aging and alteration transformed into a groundmass of celadonite and opaline mixture rich in Fe-(hydro)oxides. The opaline–celadonite groundmass, or its amorphous precursor, served as a substrate for the growth of siderite and dolomite crystals.

Early discordant diagenesis in the Brent Group, Murchison Field, UK North Sea, detected in high values of seismic-derived acoustic impedance

Acoustic impedance inversion of seismic data in the Murchison Field, UK North Sea has revealed a zone of high acoustic impedance within the Rannoch Formation of the Brent Group which is discordant to stratigraphy. The high values of acoustic impedance are caused by the diagenetic growth of siderite and pyrite early in the burial history of the rocks, probably while semi-consolidated at a depth of less than 1000 ft. The zone is approximately parallel to the overlying Base Cretaceous unconformity and its formation may have been controlled by a temperature gradient and/or groundwater chemical boundary that was parallel to ground surface at that time.

Orientation history and rheology in slates, Kodiak and Afognak Islands, Alaska

Theoretical and experimental studies have shown that slates have a roughly parabolic yield curve in φ - σ and Φ - σ space, where φ is the orientation of cleavage relative to the maximum compressive stress, Φ is the orientation of cleavage relative to the incremental shortening direction and σ is the deviatoric stress. Deformation mechanisms that operate in low-grade rocks such as diffusive mass transfer in a grain boundary fluid, dislocation creep and frictional grain boundary sliding may have stress-strain rate relationships that depend on φ. During a progressive strain history, φ and Φ may vary as a function of the strain path. Thus, the sequence of dominant deformation mechanisms as well as the stress-strain history may depend on the orientation history or variations in Φ as strain accumulates. In the Kodiak Formation, a slate belt in southwest Alaska, the orientation history and deformation mechanisms were evaluated using incremental strain indicators and microstructures. There are four successive textural events: (1) development of a slaty cleavage ( S 2) with antitaxial growth of fibrous quartz and mica in pressure shadows ( Fi 2); (2) static growth of siderite and chlorite porphyroblasts; (3) 10–70° rotation of porphyroblasts relative to S 2 with growth of curved syntaxial siderite fibers; and (4) antitaxial growth of fibrous quartz and micas with local development of a crenulation cleavage ( S 3). Cumulative incremental strain and progressive finite strain histories were determined in 23 samples from syntectonic fibers, and orientation histories were reconstructed from information provided by cumulative incremental strain histories. Textural and strain analyses indicate that: (1) the strain history of nearly all samples can be approximated by two coaxial strain accumulations separated by a rigid rotation; (2) development of crenulation cleavages was dependent on the orientation history and the magnitude of the early strain accumulation (i.e. the degree of mica alignment at the completion of D 2); (3) unstable behavior, or buckling, occurred when suggesting that the angle of internal friction (Ψ) was close to 0° (i.e. basal slip in micas may have been more important than frictional grain boundary sliding); and (4) diffusive mass transfer was accompanied by anisotropic plastic deformation, so the orientation history could be used to reconstruct the σ - ϵ history.