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Megacrystic clinopyroxenes from Victoria (Australia); crystal chemical comparisons of pyroxenes from high and low pressure regimes

A. Dal-Negro, S. Manoli, L. Secca and E. M. Piccirillo
Megacrystic clinopyroxenes from Victoria (Australia); crystal chemical comparisons of pyroxenes from high and low pressure regimes
European Journal of Mineralogy (February 1989) 1 (1): 105-121

Abstract

Analysis of a suite of Ca-rich clinopyroxene megacrysts from this area showed that their small cell volumes are similar to those of clinopyroxenes from spinel peridotite nodules, and are significantly lower than those of phenocryst clinopyroxenes crystallized at low P in alkaline to tholeiitic basalts. The small volumes are the result of a large reduction of M1 and M2 polyhedral volumes. By contrast the tetrahedral volume is larger and is comparable with that of clinopyroxenes of low P crystallized from alkaline magmas. Clinopyroxene megacrysts are characterized by Mg/(Mg + Fe (super 2+) ) ratios much lower than those of clinopyroxenes from spinel peridotite nodules, but similar to those of clinopyroxenes of low P. Low Mg/(Mg + Fe (super 2+) ) ratio values, large tetrahedral volumes and small cell volumes are consistent with the clinopyroxene megacrysts having crystallized (from alkaline magmas) at high P.


ISSN: 0935-1221
Serial Title: European Journal of Mineralogy
Serial Volume: 1
Serial Issue: 1
Title: Megacrystic clinopyroxenes from Victoria (Australia); crystal chemical comparisons of pyroxenes from high and low pressure regimes
Affiliation: Univ. Padova, Dip. Mineral. Petrol., I-35100 Padua, Italy
Pages: 105-121
Published: 198902
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 21
Accession Number: 1992-059277
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: 5 tables
S39°00'00" - S34°00'00", E140°00'00" - E150°00'00"
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 1992
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