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Transformation of pentlandite to violarite under mild hydrothermal conditions

Christophe Tenailleau, Allan Pring, Barbara Etschmann, Joel Brugger, Ben Grguric and Andrew Putnis
Transformation of pentlandite to violarite under mild hydrothermal conditions
American Mineralogist (April 2006) 91 (4): 706-709


The transformation of pentlandite, (Ni,Fe) (sub 9) S (sub 8) , to violarite, (Ni,Fe) (sub 3) S (sub 4) , has been investigated under mild hydrothermal conditions, at constant values of pH (range 3 to 5) controlled by the acetic acid/sodium acetate buffer. At 80 degrees C, 20(4) wt% of the pentlandite transforms to violarite in 33 days; with the addition of small amounts of Fe (super 3+) (CH (sub 3) COO) (sub 2) (OH) and H (sub 2) S the reaction reaches 40(4) wt% completion in this time. At 120 degrees C and a pressure of 3.5 bars the reaction is complete in 3 days at pH 3.9. Electron backscatter diffraction and backscattered electron imaging reveal that the reaction textures are typical of a coupled dissolution-reprecipitation reaction, rather than a solid state electrolytic process as has been previously reported. The gap between the dissolution front and the precipitation front of violarite is less than 400 nm. The violarite produced by these hydrothermal transformations is texturally similar to supergene violarite, being fine grained, porous and finely cracked.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 91
Serial Issue: 4
Title: Transformation of pentlandite to violarite under mild hydrothermal conditions
Affiliation: South Australian Museum, Department of Mineralogy, Adelaide, South Aust., Australia
Pages: 706-709
Published: 200604
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 17
Accession Number: 2006-041379
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus.
Secondary Affiliation: University of Adelaide, AUS, AustraliaUniversity of South Australia, AUS, AustraliaBHP Billiton, AUS, AustraliaUniversitaet Muenster, DEU, Federal Republic of Germany
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200623
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