Petrology and mineral chemistry of shallow intrusive carbonatites : examples from the Kola Peninsula and Cape Verde ...

• Main Author: Smith, Barbara
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: Birkbeck, University of London 2022
• Subjects: kola peninsula
• Online Access: https://dx.doi.org/10.18743/pub.00049511; https://eprints.bbk.ac.uk/id/eprint/49511

Analysis of hypabyssal carbonatite and associated silicate rocks from three locations was undertaken to establish the processes leading to their textural and chemical diversity. Carbonatite dykes from Vuorijarvi (Kola Peninsula) show good evidence of magmatic processes and were least affected by fenitization. Globular calcite and apatite inclusions in silicate phases indicate precipitation from a silicate melt; subsolidus recrystallisation of olivine to monticellite implies an early stage of carbonatite formation; complex substitution in perovskite formed Zr-garnet. Occurrences of xenocrysts suggest extensive wall-rock interaction. Primary tabular calcite was replaced by secondary mosaic calcite, and amphibole was formed by early fenitisation. Calcite and apatite host LREE; Zr-garnet and perovskite show strong compatibility for Zr, Nb and all REE. Hypabyssal carbonatites of Fogo, Cape Verde, contain glimmerite sheets which formed hydrothermal pathways in which accessory minerals crystallised. Shearing also ...