Cuspidine-niocalite-baghdadite solid solutions in the metacarbonatites of the Basal Complex of Fuerteventura (Canary Islands)

Ramón Casillas, G. Nagy, A. Demény, Agustina Ahijado, Carlos Fernández

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Metamorphosed carbonatites, located in the Basal Complex of Fuerteventura, Canary Islands (Spain), contain unusual Ca-Nb-Zr disilicates. These mineral phases appear in different textural situations that have very different chemical compositions. More widespread Ca-Nb disilicates with minor Zr contents cover the whole range of cuspidine-niocalite solid solution. Disilicate crystals containing more Zr always have Nb, too, and can be described as members of the cuspidine-niocalite-baghdadite ternary solid solution. The crystals richest in Zr have intermediate compositions between niocalite and baghdadite. All of the analyzed crystals have very high Sr contents (between 0.05 and 0.30 a.p.f.u.) and very low Na contents in substitution of Ca compared to the composition of the cuspidine group minerals from diverse paragenesis. The Ca-Nb-Zr disilicate crystals were formed by metamorphic and metasomatic recrystallization of zircon and pyrochlore crystals, which are very frequent in the igneous carbonatites of Fuerteventura, due to the increase in temperature around the ultramafic intrusion of the Pajara pluton and the circulation of F, S and H2O-rich high temperature fluids. Zr-rich minerals of the cuspidine-niocalite solid solution and crystals belonging to the baghdadite-niocalite solid solution as described in the Fuerteventura metacarbonatites have not been reported previously from any other paragenesis and are considered to represent new members of the cuspidine-lavenite group.

Original languageEnglish
Pages (from-to)25-41
Number of pages17
JournalLithos
Volume105
Issue number1-2
DOIs
Publication statusPublished - Sep 2008

Fingerprint

solid solution
Solid solutions
crystal
Crystals
Minerals
paragenesis
mineral
Chemical analysis
pyrochlore
pluton
Ca(3)ZrSi(2)O(9)
zircon
substitution
Substitution reactions
chemical composition
Temperature
Fluids
fluid
temperature

Keywords

  • Baghdadite
  • Canaries
  • Cuspidine
  • Fuerteventura
  • Metacarbonatite
  • Niocalite

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Cuspidine-niocalite-baghdadite solid solutions in the metacarbonatites of the Basal Complex of Fuerteventura (Canary Islands). / Casillas, Ramón; Nagy, G.; Demény, A.; Ahijado, Agustina; Fernández, Carlos.

In: Lithos, Vol. 105, No. 1-2, 09.2008, p. 25-41.

Research output: Contribution to journalArticle

Casillas, Ramón ; Nagy, G. ; Demény, A. ; Ahijado, Agustina ; Fernández, Carlos. / Cuspidine-niocalite-baghdadite solid solutions in the metacarbonatites of the Basal Complex of Fuerteventura (Canary Islands). In: Lithos. 2008 ; Vol. 105, No. 1-2. pp. 25-41.
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abstract = "Metamorphosed carbonatites, located in the Basal Complex of Fuerteventura, Canary Islands (Spain), contain unusual Ca-Nb-Zr disilicates. These mineral phases appear in different textural situations that have very different chemical compositions. More widespread Ca-Nb disilicates with minor Zr contents cover the whole range of cuspidine-niocalite solid solution. Disilicate crystals containing more Zr always have Nb, too, and can be described as members of the cuspidine-niocalite-baghdadite ternary solid solution. The crystals richest in Zr have intermediate compositions between niocalite and baghdadite. All of the analyzed crystals have very high Sr contents (between 0.05 and 0.30 a.p.f.u.) and very low Na contents in substitution of Ca compared to the composition of the cuspidine group minerals from diverse paragenesis. The Ca-Nb-Zr disilicate crystals were formed by metamorphic and metasomatic recrystallization of zircon and pyrochlore crystals, which are very frequent in the igneous carbonatites of Fuerteventura, due to the increase in temperature around the ultramafic intrusion of the Pajara pluton and the circulation of F, S and H2O-rich high temperature fluids. Zr-rich minerals of the cuspidine-niocalite solid solution and crystals belonging to the baghdadite-niocalite solid solution as described in the Fuerteventura metacarbonatites have not been reported previously from any other paragenesis and are considered to represent new members of the cuspidine-lavenite group.",
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N2 - Metamorphosed carbonatites, located in the Basal Complex of Fuerteventura, Canary Islands (Spain), contain unusual Ca-Nb-Zr disilicates. These mineral phases appear in different textural situations that have very different chemical compositions. More widespread Ca-Nb disilicates with minor Zr contents cover the whole range of cuspidine-niocalite solid solution. Disilicate crystals containing more Zr always have Nb, too, and can be described as members of the cuspidine-niocalite-baghdadite ternary solid solution. The crystals richest in Zr have intermediate compositions between niocalite and baghdadite. All of the analyzed crystals have very high Sr contents (between 0.05 and 0.30 a.p.f.u.) and very low Na contents in substitution of Ca compared to the composition of the cuspidine group minerals from diverse paragenesis. The Ca-Nb-Zr disilicate crystals were formed by metamorphic and metasomatic recrystallization of zircon and pyrochlore crystals, which are very frequent in the igneous carbonatites of Fuerteventura, due to the increase in temperature around the ultramafic intrusion of the Pajara pluton and the circulation of F, S and H2O-rich high temperature fluids. Zr-rich minerals of the cuspidine-niocalite solid solution and crystals belonging to the baghdadite-niocalite solid solution as described in the Fuerteventura metacarbonatites have not been reported previously from any other paragenesis and are considered to represent new members of the cuspidine-lavenite group.

AB - Metamorphosed carbonatites, located in the Basal Complex of Fuerteventura, Canary Islands (Spain), contain unusual Ca-Nb-Zr disilicates. These mineral phases appear in different textural situations that have very different chemical compositions. More widespread Ca-Nb disilicates with minor Zr contents cover the whole range of cuspidine-niocalite solid solution. Disilicate crystals containing more Zr always have Nb, too, and can be described as members of the cuspidine-niocalite-baghdadite ternary solid solution. The crystals richest in Zr have intermediate compositions between niocalite and baghdadite. All of the analyzed crystals have very high Sr contents (between 0.05 and 0.30 a.p.f.u.) and very low Na contents in substitution of Ca compared to the composition of the cuspidine group minerals from diverse paragenesis. The Ca-Nb-Zr disilicate crystals were formed by metamorphic and metasomatic recrystallization of zircon and pyrochlore crystals, which are very frequent in the igneous carbonatites of Fuerteventura, due to the increase in temperature around the ultramafic intrusion of the Pajara pluton and the circulation of F, S and H2O-rich high temperature fluids. Zr-rich minerals of the cuspidine-niocalite solid solution and crystals belonging to the baghdadite-niocalite solid solution as described in the Fuerteventura metacarbonatites have not been reported previously from any other paragenesis and are considered to represent new members of the cuspidine-lavenite group.

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