Zirconium-bearing accessory minerals in UK Paleogene granites: textural, compositional, and paragenetic relationships

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Marco E. Ciriotti
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Zirconium-bearing accessory minerals in UK Paleogene granites: textural, compositional, and paragenetic relationships

Messaggio da Marco E. Ciriotti » ven 24 set, 2021 9:14

Referenza:
▪ Belkin, H.E. & Macdonald, R. (2021): Zirconium-bearing accessory minerals in UK Paleogene granites: textural, compositional, and paragenetic relationships. European Journal of Mineralogy, 33, 537–570.

Abstract:
The mineral occurrences, parageneses, textures, and compositions of Zr-bearing accessory minerals in a suite of UK Paleogene granites from Scotland and Northern Ireland are described. Baddeleyite, zirconolite, and zircon, in that sequence, formed in hornblende + biotite granites (type 1) and hedenbergite–fayalite granites (type 2). The peralkaline microgranite (type 3) of Ailsa Craig contains zircon, dalyite, a eudialyte-group mineral, a fibrous phase which is possibly lemoynite, and Zr-bearing aegirine. Hydrothermal zircon is also present in all three granite types and documents the transition from a silicate-melt environment to an incompatible element-rich aqueous-dominated fluid. No textures indicative of inherited zircon were observed. The minerals crystallized in stages from magmatic through late-magmatic to hydrothermal. The zirconolite and eudialyte-group mineral are notably Y+REE-rich (REE signifies rare earth element). The crystallization sequence of the minerals may have been related to the activities of Si and Ca, to melt peralkalinity, and to local disequilibrium.
Marco E. Ciriotti

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