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Crystal chemistry of Cr-spinels from a suite of spinel peridotite mantle xenoliths from the Predazzo area (Dolomites, northern Italy)

Anna Carraro
Crystal chemistry of Cr-spinels from a suite of spinel peridotite mantle xenoliths from the Predazzo area (Dolomites, northern Italy)
European Journal of Mineralogy (August 2003) 15 (4): 681-688

Abstract

The crystal chemistry of ten Cr-spinels enclosed in protogranular to weakly porphyroclastic spinel peridotite mantle xenoliths from the Predazzo Area (Dolomites, Northern Italy) was studied by single-crystal X-ray diffraction and electron microprobe. Within the suite, unit cell parameter a (sub 0) increases from 8.1358 to 8.2201 Aa, with increasing Cr content, from 0.205 to 0.812 a.f.u., whereas the oxygen coordinate u remains virtually constant (u = 0.2627-0.2630), therefore giving a quite constant ratio of octahedral (M-O) and tetrahedral (T-O) bond distances. The cation distribution, obtained from structural and chemical data, shows that, with increasing Cr (super 3+) within the suite, the Al (T) content decreases from 0.144 to 0.056 a.f.u. Data from the Predazzo spinels were compared with those of spinel suites from well-defined mantle rocks (Newer Victoria, Australia; NE Brazil; Assab, Ethiopia; Balmuccia, Italy) from different petrological environments. Estimation of the intracrystalline closure temperature for the investigated spinels gives a mean value of 769 degrees C. This indicates a cooling rate intermediate between that of a slowly cooled peridotitic massif and that of very fast cooled mantle xenoliths hosted by volcanics, which is consistent with the origin of the Predazzo spinels from mantle xenoliths hosted in subvolcanic dykes.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 15
Serial Issue: 4
Title: Crystal chemistry of Cr-spinels from a suite of spinel peridotite mantle xenoliths from the Predazzo area (Dolomites, northern Italy)
Author(s): Carraro, Anna
Affiliation: Universita di Padova, Dipartimento di Mineralogia e Petrologia, Padua, Italy
Pages: 681-688
Published: 200308
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 19
Accession Number: 2003-070558
Categories: Mineralogy of non-silicatesIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
N46°00'00" - N46°45'00", E11°30'00" - E12°15'00"
N46°19'00" - N46°19'00", E11°37'00" - E11°37'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200321
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