Mechanism of pyroxene and amphibole weathering—I. Experimental studies of iron-free minerals

Schott, Jacques; Berner, Robert A.; Sjöberg, Eric

doi:10.1016/0016-7037(81)90065-x

Cited by 335 publications

(148 citation statements)

References 14 publications

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“…The highest concentrations of total dissolved solids (measured by specific conductance) for all rock types occurred during the first weeks of the experiment because of very-fine particles (potential to pass through the cell filter media) and highly reactive fresh-mineral surfaces as a result of mining [39][40][41]. This effect was anticipated and an increased number of column floodings was implemented for weeks 0, 1, 2 and 3 according to Lapakko and White's [42] modification of the ASTM method [34].…”

Section: Leachate Characteristicsmentioning

confidence: 99%

Diavik Waste Rock Project: Evolution of Mineral Weathering, Element Release, and Acid Generation and Neutralization during a Five-Year Humidity Cell Experiment

et al. 2014

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Abstract:A five-year, humidity-cell experiment was used to study the weathering evolution of a low-sulfide, granitic waste rock at 5 and 22 °C. Only the rock with the highest sulfide content (0.16 wt %) released sufficient acid to overcome a limited carbonate acid-neutralization capacity and produce a substantial decline in pH. Leached SO 4 and Ca quickly increased then decreased during the first two years of weathering. Sulfide oxidation continued to release acid and SO 4 after carbonate depletion, resulting in an increase in acid-soluble elements, including Cu and Zn. With the dissolution of Al-bearing minerals, the pH stabilized above 4, and sulfide oxidation continued to decline until the end of the experiment. The variation in activation energy of sulfide oxidation correlates with changes in sulfide availability, where the lowest activation energies occurred during the largest releases of SO 4 . A decrease in sulfide availability was attributed to consumption of sulfide and weathered rims on sulfide grains that reduced the oxidation rate. Varying element release rates due to changing carbonate and sulfide availability provide identifiable OPEN ACCESSMinerals 2014, 4 258 geochemical conditions that can be viewed as neutralization sequences and may be extrapolated to the field site for examining the evolution of mineral weathering of the waste rock.

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Section: Leachate Characteristicsmentioning

confidence: 99%

Diavik Waste Rock Project: Evolution of Mineral Weathering, Element Release, and Acid Generation and Neutralization during a Five-Year Humidity Cell Experiment

et al. 2014

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“…Schott et al (1981), Berner andSchott(1982),andSchottandBerner(1983, 1985 studied experimentally and naturally weathered surfaces of iron-free Copyright 9 1989, The Clay Minerals Society and iron-bearing pyroxenes by X-ray photoelectron spectroscopy (XPS). They found that a thin layer (a few tens of,~mg-stroms thick) depleted in Ca and Mg relative to silica formed on iron-free pyriboles.…”

Section: Previous Workmentioning

confidence: 99%

Weathering of Hornblende to Ferruginous Products by a Dissolution-Reprecipitation Mechanism: Petrography and Stoichiometry

Velbel

1989

Clays and clay miner.

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Abstract--Hornblende of the Carrol Knob mafic complex (southern Blue Ridge Mountains, North Carolina) has weathered under humid, temperate conditions. Hornblende weathering appears to have been a dissolution-reprecipitation reaction, in which hornblende dissolved stoichiometrically, and the ferruginous and aluminous weathering products (goethite, gibbsite, and kaolinite) precipitated from solution (neoformation). During the earliest stage of alteration, ferruginous weathering products formed as linings of fractures within and around crystals and cleavage fragments of hornblende. Side-by-side coalescence of lenticular etch pits during more advanced weathering produced characteristic "denticulated" terminations on hornblende remnants in dissolution cavities bounded by ferruginous boxworks. Dissolution cavities are devoid of weathering products. Small "pendants" of ferruginous material project from the boxwork into void spaces. Because these products are separated from the hornblende remnants by void space, they must have been produced by dissolution-reprecipitation reactions. Complete removal of the parent hornblende left a ferruginous microboxwork or "negative pseudomorph." Only A1 and Fe were conserved over microscopic distances; alkali and alkaline-earth elements were stoichiometrically removed from the weathering microenvironment during the weathering process.

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“…67 Thus, with increasing temperature, the dissolution rate of the altered surface layer increases more rapidly than the rate of diffusion, resulting in a decrease in the thickness of the leached layer. 67 Similar Si-rich altered layers were also observed on the surfaces of acid-leached olivines, 48,[68][69][70] pyroxenes, 68,71,72 and amphibole [tremolite, Ca2(Mg,Fe)5Si8O22(OH)2 (Mg > Fe)], 72 because of preferential leaching of Mg, Fe, and Ca. The thickness of altered surface layers, deduced from XPS analyses, was 20 nm for olivine, 69 and less than a few nanometers for pyroxenes 68,72 and tremolite, 72 i.e.…”

Section: Mgmentioning

confidence: 87%

Surface-analytical Studies on Environmental and Geochemical Surface Processes

Seyama

Soma

2003

ANAL. SCI.

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Mechanism of pyroxene and amphibole weathering—I. Experimental studies of iron-free minerals

Cited by 335 publications

References 14 publications

Diavik Waste Rock Project: Evolution of Mineral Weathering, Element Release, and Acid Generation and Neutralization during a Five-Year Humidity Cell Experiment

Diavik Waste Rock Project: Evolution of Mineral Weathering, Element Release, and Acid Generation and Neutralization during a Five-Year Humidity Cell Experiment

Weathering of Hornblende to Ferruginous Products by a Dissolution-Reprecipitation Mechanism: Petrography and Stoichiometry

Surface-analytical Studies on Environmental and Geochemical Surface Processes

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