SIMS depth profiles of weathered plagioclase and processes affecting dissolved Al and Si in some acidic soil solutions

Nesbitt, H.W.; Muir, I.J.

doi:10.1038/334336a0

Cited by 70 publications

(39 citation statements)

References 19 publications

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“…This is an obvious advantage for improved modeling of laboratory and natural 641 chemical weathering reactions. Moreover, this mechanism is also compatible with published 642 measurements that show an abrupt change in the composition of surface layers on altered 643 feldspars from Si to Al-rich at circum-neutral to moderately basic pH conditions (Chou and 644 Wollast, 1985;Nesbitt and Muir, 1988), a phenomenon difficult to explain with the leached 645 layer theory. Related to this is the observation that significant (apparent) non-stoichiometric 646 dissolution can even occur at basic pH (Hellmann, 1995), conditions not relevant for cation-647 proton exchange.…”

Section: Interfacial Dissolution-reprecipitaton Mechanism 606supporting

confidence: 77%

Unifying natural and laboratory chemical weathering with interfacial dissolution–reprecipitation: A study based on the nanometer-scale chemistry of fluid–silicate interfaces

et al. 2012

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in particular the leached layer theory. Most importantly, our data provide critical evidence for 51 a single mechanism based on interfacial dissolution-reprecipitation. This concept not only 52 unifies weathering processes for the first time, but we also suggest that nanoscale-surface 53 processes can have a potentially negative impact on CO 2 uptake associated with chemical 54 weathering. The results in this study, when combined with recently published research on 55 fluid-assisted mineral replacement reactions, supports the idea that dissolution-reprecipitation 56 is a universal mechanism controlling fluid-mineral interactions . 57Based on this we propose the existence of a chemical weathering continuum based solely on 58 the interfacial dissolution-reprecipitation mechanism. 59 3

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Section: Interfacial Dissolution-reprecipitaton Mechanism 606supporting

confidence: 77%

Unifying natural and laboratory chemical weathering with interfacial dissolution–reprecipitation: A study based on the nanometer-scale chemistry of fluid–silicate interfaces

et al. 2012

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“…The surface compositions of the feldspars that reacted experimentally with acid solutions tend to show a decrease in alkali cations and AI, and an increase in Si (Casey et al 1988(Casey et al , 1989Hochella et al 1988;Muir et al 1989Muir et al , 1990Petit et al 1989;Nesbitt et al 1991). On the contrary, Al-enriched layers at the surface of naturally weathered feldspars have been confirmed by EDX (Nixon 1979) and secondary ion mass spectroscopy (Nesbitt and Muir 1988). Similar leaching behaviors of hornblende in natural environments were also recognized by Auger electron spectroscopy (Mogk and Locke 1988).…”

Section: Resultsmentioning

confidence: 65%

Amorphous Aluminum Hydroxide Formed at the Earliest Weathering Stages of K-Feldspar

Kawano

Tomita

1996

Clays and clay miner.

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Abstract--Weathering products formed on the surface of K-feldspar in Yakushima Island, Japan were investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). XRD confirmed that the weathering products were composed mainly of gibbsite and halloysite. SEM, TEM and EDX clearly showed formation of amorphous aluminum hydroxide exhibiting 2 distinct habits: 1) curled fibrous or circular forms less than 0.02 p,m in diameter; and 2) a spherical habit less than 1.0 p~m in diameter. The fibrous aluminum hydroxide exhibited curled fibrous forms or circular forms less than 0.02 p.m in diameter and gave a diffuse electron diffraction halo. EDX indicated that the material consisted mainly of A1 and very small amounts of Si and Fe. The spherical aluminum hydroxide also gave similar EDX and electron diffraction characteristics to the fibrous material. These fibrous and spherical aluminum hydroxides must be formed as a metastable phase in the earliest weathering stages, and transformed into a stable phase of gibbsite and halloysite as the reaction proceeded.

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“…This is most often caused by precipitation of secondary minerals or by preferential leaching of more reactive species in the primary mineral. The composition of the fluid coexisting with minerals undergoing dissolution will also affect the nonstoichiometric release of components (Amrhein and Suarez, 1988;Casey et al, 1988;Nesbitt and Muir, 1988;Hellmann et al, 1989Hellmann et al, , 1990Inskeep et al, 1991;Nesbitt et al, 1991;Amrhein and Suarez, 1992;Alekseyev et al, 1993;Casey et al, 1993;Oxburgh et al, 1994;Stillings and Brantley, 1995;Gout et al, 1997;. The relatively acidic conditions (low aNa + /aH + ) that characterized the starting fluid for the experiments, for example, initiated albite dissolution in the boehmite field of stability.…”

Section: Article In Pressmentioning

confidence: 99%

A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

Chen¹

2008

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Currently, DOE is conducting pilot CO 2 injection tests to evaluate the concept of geological sequestration. The injected CO 2 is expected to react with the host rocks and these reactions can potentially alter the porosity, permeability, and mechanical properties of the host or cap rocks. Reactions can also result in precipitation of carbonate-containing minerals that favorably and permanently trap CO 2 underground. Many numerical models have been used to predict these reactions for the carbon sequestration program. However, a firm experimental basis for predicting silicate reaction kinetics in CO 2 injected geological formations is urgently needed to assure the reliability of the geochemical models used for the assessments of carbon sequestration strategies. The funded experimental and theoretical study attempts to resolve this outstanding scientific issue by novel experimental design and theoretical interpretation of silicate dissolution rates at conditions pertinent to geological carbon sequestration.In this four year research grant (three years plus a one year no cost extension), seven (7) laboratory experiments of CO 2 -rock-water interactions were carried out. An experimental design allowed the collection of water samples during experiments in situ and thus prevented back reactions. Analysis of the in situ samples delineated the temporal evolution of aqueous chemistry because of CO 2 -rock-water interactions. The solid products of the experiments were retrieved at the end of the experimental run, and analyzed with a suite of advanced analytical and electron microscopic techniques (i.e., atomic resolution transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron microprobe, X-ray diffraction, X-ray photoelectron spectroscopy (XPS)). As a result, the research project probably has produced one of the best data sets for CO 2 -rock-water interactions in terms of both aqueous solution chemistry and solid characterization. Three experiments were performed using the Navajo sandstone. Navajo sandstone is geologically equivalent to the Nugget sandstone, which is a target formation for a regional partnership injection project. Our experiments provided the experimental data on the potential CO 2 -rock-water interactions that are likely to occur in the aquifer. Geochemical modeling was performed to interpret the experimental results.Our single mineral (feldspar) experiments addressed a basic research need. i.e., the coupled nature of dissolution and precipitation reactions, which has universal implication to the reaction kinetics as it applied to CO 2 sequestration. Our whole rock experiments (Navajo sandstone) addressed the applied research component, e.g., reacting Navajo sandstone with brine and CO 2 has direct relevance on the activities of a number of regional partnerships.The following are the major findings from this project:1. The project generated a large amount of experimental data that is central to evaluating CO 2 -water-rcok interactions and providing ground truth to pred...

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SIMS depth profiles of weathered plagioclase and processes affecting dissolved Al and Si in some acidic soil solutions

Cited by 70 publications

References 19 publications

Unifying natural and laboratory chemical weathering with interfacial dissolution–reprecipitation: A study based on the nanometer-scale chemistry of fluid–silicate interfaces

Unifying natural and laboratory chemical weathering with interfacial dissolution–reprecipitation: A study based on the nanometer-scale chemistry of fluid–silicate interfaces

Amorphous Aluminum Hydroxide Formed at the Earliest Weathering Stages of K-Feldspar

A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

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