Apatite-group minerals from nepheline syenite, Pilansberg alkaline complex, South Africa (original) (raw)

none 10.1180/0026461067050346 Mineralogical Society The Mineralogical Society 7149 25377197 5840 2021020407285211229 10.1180 2021-02-04T07:40:47Z 2007-01-16T15:29:37Z 24 Mineralogical Magazine Mineral. mag. 0026-461X 1471-8022 10 2006 70 5 Apatite-group minerals from nepheline syenite, Pilansberg alkaline complex, South Africa R. P. Liferovich R. H. Mitchell Abstract The nepheline syenites of the Pilansberg alkaline complex (South Africa) have undergone extensive subsolidus equilibration and alteration with a deuteric Cl- and Na-rich fluid phase. Complex assemblages of secondary minerals result from the replacement of primary alummosilicates, rinkite, eudialyte and fluorapatite. The composition of apatite group minerals formed during these alteration processes reflects the Sr- and rare earth element (REE ) content, Na/Cl ratio and pH of the deuteric fluids. Apatite-group minerals are observed to have formed in the following sequence: orthomagmatic fluorapatite; strontian britholite-(Ce); strontian fluorapatite; Sr-apatite;REE -rich Sr-apatite; Sr-Na-REE - rich minerals approaching the stoichiometry of belovite-(Ce) and deloneite-(Ce); britholite-(Ce). Increasing alkalinity of the deuteric fluids is reflected by increasing amounts of Sr replacing Ca in apatite and culminates in the formation of Sr apatite containing 62.1 wt.% SrO (∼4.17 a.p.f.u. Sr). Pilansberg apatite-group minerals form a near-complete solid solution between fluorapatite and a fluorine analogue of Sr apatite with limited solution towards belovite-(Ce), Si-rich belovite-(Ce) and strontian britholite-(Ce). 07 05 2018 10 2006 463 484 S0026461X0005605X https://www.cambridge.org/core/terms 10.1180/0026461067050346 https://www.cambridge.org/core/product/identifier/S0026461X0005605X/type/journal\_article https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0026461X0005605X http://www.ingentaconnect.com/content/minsoc/mag/2006/00000070/00000005/art00001 http://minmag.geoscienceworld.org/cgi/doi/10.1180/0026461067050346 Mineralogy of Khibina Complex, part II 585 1978 Kostyleva-Labuntsova Alkaline Magmatism in the NE part of the Baltic Shield 106 1990 Khomyakov Lovozero Massif: History of Investigations, Pegmatites, Minerals 432 2001 Pekov Retief, E. A. 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