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The (Mg,Fe (super 2+) ) substitution in ferri-clinoholmquistite, []Li (sub 2) (Mg,Fe (super 2+) ) (sub 3) Fe (super 3+) (sub 2) Si (sub 8) O (sub 22) (OH) (sub 2)

Gianluca Iezzi, Giancarlo Della Ventura, Frank C. Hawthorne, Giuseppe Pedrazzi, Jean-Louis Robert and Daniela Novembre
The (Mg,Fe (super 2+) ) substitution in ferri-clinoholmquistite, []Li (sub 2) (Mg,Fe (super 2+) ) (sub 3) Fe (super 3+) (sub 2) Si (sub 8) O (sub 22) (OH) (sub 2)
European Journal of Mineralogy (October 2005) 17 (5): 733-740


Amphiboles have been synthesized hydrothermally at 500-600 degrees C, 1 kbar P(H (sub 2) O) and low fO (sub 2) along the join ferri-holmquistite-ferri-clino-ferroholmquistite. At 500 degrees C, on the Fe-rich side of the join, up to approximately 50 mol.% ferri-holmquistite occurs. For higher Mg contents, an assemblage consisting predominantly of clinopyroxene + quartz is obtained, and amphibole is only a minor phase. At 600 degrees C, the situation is reversed, with amphibole the dominant phase in the Mg-rich side of the join( approximately 60-100 mol % ferrri-holmquistite); XRD patterns can be indexed in space group C2/m and cell parameters show well-defined linear trends. Moessbauer spectra show that Fe (super 3+ ) is ordered strongly at the M2 site, whereas Fe (super 2+) is disordered over the B and C sites. The IR spectra show fine structure caused by ordering of Mg and Fe (super 2+) over the M1 and M3 sites; this fine structure consists of four main bands assigned to the four local combinations of (Mg,Fe (super 2+) ) at M(1,3). There is almost complete Mg-Fe (super 2+) substitution at M(1,3) in ferri-clinoholmquistite. The IR spectra also show, in addition, four minor components that are assigned to (Fe (super 2+) ,Mg) at M4, indicating that the amphibole composition departs from the nominal one following the vector (super M) (super 4) Fe (super 2+) (super M) (super 2) Mg (super M) (super 2) Fe (super 3+) (sub -1) (super M) (super 4) Li (sub -1) .

ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 17
Serial Issue: 5
Title: The (Mg,Fe (super 2+) ) substitution in ferri-clinoholmquistite, []Li (sub 2) (Mg,Fe (super 2+) ) (sub 3) Fe (super 3+) (sub 2) Si (sub 8) O (sub 22) (OH) (sub 2)
Affiliation: Universita "G. D'Annunzio, Dipartimento di Scienze della Terra, Scalo, Italy
Pages: 733-740
Published: 200510
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 28
Accession Number: 2005-074505
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
Secondary Affiliation: Universita Roma Tre, ITA, ItalyUniversity of Manitoba, CAN, CanadaUniversita di Parma, ITA, ItalyISTO, FRA, France
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200544
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