Lancaster EPrints

Compositional variation in minerals of the chevkinite group.

MacDonald, Raymond and Belkin, H. E. (2002) Compositional variation in minerals of the chevkinite group. Mineralogical Magazine, 66 (6). pp. 1075-1098. ISSN 0026-461X

Full text not available from this repository.

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 + MC3+,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.

Item Type: Article
Journal or Publication Title: Mineralogical Magazine
Uncontrolled Keywords: CHEVKINITE ; PERRIERITE ; COMPOSITIONAL VARIATION.
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
Departments: Faculty of Science and Technology > Lancaster Environment Centre
ID Code: 21479
Deposited By: ep_ss_importer
Deposited On: 15 Jan 2009 10:23
Refereed?: Yes
Published?: Published
Last Modified: 26 Jul 2012 15:47
Identification Number:
URI: http://eprints.lancs.ac.uk/id/eprint/21479

Actions (login required)

View Item