Ilmenite generations in kimberlite from Banankoro, Guinea Conakry

Jingyao Xu*, Joan Carles Melgarejo, Montgarri Castillo-Oliver, Laia Arqués, Joan Santamaria

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

A complex mineral sequence in a kimberlite from the Banankoro Cluster (Guinea Conakry) has been interpreted as the result of magma mixing processes. The composition of the early generations of phlogopite and spinel suggest direct crystallisation of a kimberlitic magma. However, the compositional trends found in the late generations of phlogopite and spinels could suggest magma mixing. In this context, four ilmenite generations formed. The first generations (types 1 and 2) are geikielitic and are associated with spinel and phlogopite which follow the kimberlitic compositional trends. They are interpreted as produced by crystallization from the kimberlite magma. A third generation of euhedral tabular Mg-rich ilmenite (type 3) formed during the interval between two generations of serpentine. Finally, a late generation of Mn-rich ilmenite (type 4) replaces all the Ti-rich minerals and is contemporaneous with the last generation of serpophitic non-replacing serpentine. Therefore, the formation of type 3 and type 4 ilmenite took place after the crystallization of the groundmass, during late hydrothermal process. Our results suggest a detailed textural study is necessary when use Mg-rich and Mn-rich ilmenites as KIMs.

Original languageEnglish
Pages (from-to)191-204
Number of pages14
JournalNeues Jahrbuch fur Mineralogie, Abhandlungen
Volume195
Issue number3
Early online dateOct 2018
DOIs
Publication statusPublished - Dec 2018

Keywords

  • Kimberlite
  • Tetraferriphlogopite
  • Spinels
  • Magnesian ilmenite
  • Manganoan ilmenite
  • Geikielite

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