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GEOREF RECORD

Crystal chemistry of apatites from the Tapira carbonatite complex, Brazil

Maria Franca Brigatti, Daniele Malferrari, Luca Medici, Luisa Ottolini and Luciano Poppi
Crystal chemistry of apatites from the Tapira carbonatite complex, Brazil
European Journal of Mineralogy (August 2004) 16 (4): 677-685

Abstract

The crystal chemistry of 10 hydroxylapatites from the Tapira alkaline carbonatite complex, SE Brazil, has been determined by EPMA, ion microprobe, IR spectroscopy and single-crystal XRD; their compositional range (atoms pfu) is 9.935 < or = Ca < or = 10.024, 5.926 < or = P < or = 6.006, 0.005 < or = REE < or = 0.046, 0.042 < or = F < or = 0.914, 0.003 < or = Cl < or = 0.008, 0.003 < or = Si < or = 0.038, with Na present only as a trace. Crystal structure refinements were carried out in space group P6 (sub 3) /m to R values of 0.016- 0.028. The REE for Ca substitution requires two different exchange mechanisms producing an increase in bond valence on the X site: the deprotonation of OH and/or the substitution of CO (sub 3) (super 2-) (sub ) for OH. The CO (sub 3) (super 2-) substitution in the anionic sites was found to be related to great CO (sub 2) activity of the melt whereas deprotonation of the apatite crystals could be related to the highly oxidizing nature of the Tapira carbonatitic magma. The very low Cl/F ratio suggests that the crystallization of the Tapira pluton was relatively shallow. The determination of REE partitioning between the Ca1 and Ca2 sites is difficult because of the low REE content; a proportional increase in the size of the Ca1 and Ca2 sites was noted with increasing REE content as well as an overall increase of the a cell parameter.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 16
Serial Issue: 4
Title: Crystal chemistry of apatites from the Tapira carbonatite complex, Brazil
Affiliation: Universita di Modena e Reggio Emilia, Dipartimento di Scienze della Terra, Modena, Italy
Pages: 677-685
Published: 200408
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 47
Accession Number: 2007-037371
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables
S34°00'00" - N05°15'00", W74°00'00" - W34°00'00"
Secondary Affiliation: CNR Istituto di Metodologie per l'Analisi Ambientale, ITA, ItalyCNR Istituto di Geoscienze e Georisorse, ITA, Italy
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200720

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