Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review

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Marco E. Ciriotti
Messaggi: 23479
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
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Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review

Messaggio da Marco E. Ciriotti » mar 23 ago, 2016 18:43

Prossima pubblicazione.

Referenza:
▪ Charykova, M.V. & Krivovichev V.G. (2017): Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review. Mineralogy and Petrology, 111, (in press).

Abstract:
Contemporary mineralogy and geochemistry are concerned with understanding and deciphering processes that occur near the surface of the Earth. These processes are especially important for resolving ecological challenges and developing principles of good environmental management. Selenium oxysalts, selenites and selenates, are relatively rare as minerals; there are presently only 34 known mineral species. Thirty-one “pure” selenites, which contain only selenite anionic groups, are known to occur naturally. The other three minerals each contain two anionic groups: selenate and selenite (schmiederite), selenate and sulphate (olsacherite), and selenate and iodate (carlosruizite).
This work is intended to provide a classification of natural selenium oxysalts based on their chemical composition. Selenites belong to a particular mineral system, whose components are chemical elements required to construct the crystal structure of a mineral (species-defining constituents). The number of components represents the minimum number of independent elements necessary to define the composition of the system. All selenites and selenates are divided into two groups: anhydrous selenites (I) and hydrous selenites and selenates (II).
The paper also presents systematized data published on the thermodynamics of selenites, which are formed in the weathering zone of sulfide and selenide ores, and determines approaches to the quantitative physicochemical modeling of formation conditions. The Eh–pH diagrams of the Me–Se–H2O systems (Me = Cu, Co, Ni, Fe, Zn, Ca, Al) were calculated and plotted for the average contents of these elements in aqueous weathering solutions in sulfide deposit oxidation zones.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

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Marco E. Ciriotti
Messaggi: 23479
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review

Messaggio da Marco E. Ciriotti » mer 24 ago, 2016 11:51

Selenites: 24
Ahlfeldite
Alfredopetrovite
Allochalcoselite
Burnsite
Chalcomenite
Chloromenite
Cobaltomenite
Downeyite
Favreauite
Francisite
Georgbokiite
Ilinskite
Mandarinoite
Molybdomenite
Munakataite (selenite-sulfates)
Nestolaite
Nicksobolevite
Orlandiite
Parageorgbokiite
Pauladamsite
Prewittite
Sarrabusite
Sofiite
Zincomenite

Uranyl selenites: 7
Demesmaekerite
Derriksite
Guilleminite
Haynesite
Larisaite
Marthozite
Piretite

Selenates: 3
Carlosruizite (selenate-iodates)
Olsacherite (selenate-sulfates)
Schmiederite (selenite-selenates)
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Avatar utente
Marco E. Ciriotti
Messaggi: 23479
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review

Messaggio da Marco E. Ciriotti » dom 29 gen, 2017 11:38

Pubblicazione effettuata.

Referenza:
▪ Charykova, M.V. & Krivovichev V.G. (2017): Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review. Mineralogy and Petrology, 111, 121–134.
Marco E. Ciriotti

«Things are interesting only in so far as they relate themselves to other things»

Avatar utente
Marco E. Ciriotti
Messaggi: 23479
Iscritto il: ven 25 giu, 2004 11:31
Località: via San Pietro, 55 I-10073 Devesi/Cirié TO - Italy
Contatta:

Re: Mineral systems and the thermodynamics of selenites and selenates in the oxidation zone of sulfide ores – a review

Messaggio da Marco E. Ciriotti » gio 26 ott, 2017 14:33

Referenza:
▪ Krivovichev, V., Charykova, M., Vishnevsky, A. (2017): The Thermodynamics of Selenium Minerals in Near-Surface Environments. Minerals, 7, 188; doi:10.3390/min7100188.

Abstract:
Selenium compounds are relatively rare as minerals; there are presently only 118 known mineral species. This work is intended to codify and systematize the data of mineral systems and the thermodynamics of selenium minerals, which are unstable (selenides) or formed in near-surface environments (selenites), where the behavior of selenium is controlled by variations of the redox potential and the acidity of solutions at low temperatures and pressures. These parameters determine the migration of selenium and its precipitation as various solid phases. All selenium minerals are divided into four groups—native selenium, oxide, selenides, and oxysalts—anhydrous selenites (I) and hydrous selenites and selenates (II). Within each of the groups, minerals are codified according to the minimum number of independent elements necessary to define the composition of the mineral system. Eh–pH diagrams were calculated and plotted using the Geochemist’s Workbench (GMB 9.0) software package. The Eh–pH diagrams of the Me–Se–H2O systems (where Me = Co, Ni, Fe, Cu, Pb, Zn, Cd, Hg, Ag, Bi, As, Sb, Al and Ca) were plotted for the average contents of these elements in acidic waters in the oxidation zones of sulfide deposits. The possibility of the formation of Zn, Cd, Ag and Hg selenites under natural oxidation conditions in near surface environments is discussed.
Marco E. Ciriotti

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