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| Titel |
Evidence for interfacial dissolution-precipitation during low-temperature mineral weathering |
| VerfasserIn |
Encarnacion Ruiz-Agudo, Christine V. Putnis, Carlos Rodriguez-Navarro, Andrew Putnis |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250079181
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| Zusammenfassung |
| The dissolution of most common multicomponent minerals and glasses is typically
“incongruent” as shown by the nonstoichiometric release of the solid phase components. This
frequently results in the formation of so-called surface leached layers. The mechanism of this
process has been a recurrent subject of research and debate over the past two decades, due to
its relevance to a wide range of natural and technological processes, as well as being crucial
in defining rate laws for mineral reactions. Here we report experimental, in situ nanoscale
observations that confirm the formation of a cation depleted layer at the mineral-solution
interface during dissolution of multicomponent minerals at acidic pH. Our in situ Atomic
Force Microscopy studies of the dissolution of wollastonite, CaSiO3, and dolomite,
Ca0.5Mg0.5CO3, combined with compositional analysis of reaction products, provide, for
the first time, clear direct experimental evidence that cation-depleted (i.e. leached) layers are
formed in a tight interface-coupled two step process: stoichiometric dissolution of the
pristine mineral surfaces and subsequent precipitation of a secondary phase from a
supersaturated boundary layer of fluid in contact with the mineral surface. Such a
mechanism presents a new paradigm that differs from the concept of preferential
leaching of cations, as postulated by most currently accepted incongruent dissolution
models.
References
Ruiz Agudo, E; Putnis, CV; Rodríguez Navarro, C and Putnis, A. (2012) Mechanism of
leached layer formation during chemical weathering of silicate minerals. Geology, 40,
947-950 Urosevic, M; Rodríguez Navarro,C; Putnis, CV; Cardell, C; Putnis, A and Ruiz
Agudo, E (2012) In situ nanoscale observations of the dissolution of [10-14] dolomite
cleavage surfaces. Geochimica et Cosmochimica Acta, 80, 1-13 |
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