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Compositional variation in minerals of the chevkinite group

Mineralogical Magazine

By:
and
DOI: 10.1180/0026461026660078

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Abstract

The composition of chevkinite and perrierite, the most common members of the chevkinite group, is closely expressed by the formula A4BC2D2Si4O22, where A = (La,Ce,Ca,Sr,Th), B = Fe2+, C = (Fe2+,Fe3+,Ti,Al,Zr,Nb) and D = Ti. The A site is dominated by a strong negative correlation between (Ca+Sr) and the REE. Chondrite-normalized REE patterns are very variable, e.g. in LREE/HREE and Eu/Eu*. The C site is dominated by Ti, Al and Fe2+, in very variable proportions. Most chevkinites and perrierites are close to stoichiometric, with cation sums between 12.9 and 13.5, compared to the theoretical 13. There is no single, generally applicable charge balancing substitution scheme in the group; however, the general relationship (Ca+Sr)A + TiC + REEA + M3C+2+ defines a linear array with r2 = 0.91. Chevkinite and perrierite are shown to be compositionally distinct on the basis of CaO, FeO* Al2O3 and Ce2O3 abundances. Chevkinite forms mainly in chemically evolved parageneses, such as syenites, rhyolites and fenites associated with carbonatite complexes. Perrierite is more commonly recorded from igneous rocks of mafic to intermediate composition. The compositional characteristics and possible structural formulae of other members of the chevkinite group are reviewed briefly.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Compositional variation in minerals of the chevkinite group
Series title:
Mineralogical Magazine
DOI:
10.1180/0026461026660078
Volume
66
Issue:
6
Year Published:
2002
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Mineralogical Magazine
First page:
1075
Last page:
1098