Formation of emeralds at pegmatite-ultramafic contacts based on fluid inclusions in Kianjavato emerald, Mananjary deposits, Madagascar

Ye Vapnik, I. Moroz, M. Roth, I. Eliezri

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Kianjavato emerald (Mananjary deposits, East coast of Madagascar) was formed during metasomatic processes at the contact between pegmatites and hornblendites. The metasomatic exchange was related to a Pan-African tectonometamorphic event. Fluid inclusions in the Kianjavato emerald and quartz were studied by means of microthermometry and Raman probe analysis. Three main types of inclusions were revealed: CO2-rich, CH4-rich and aqueous-rich, with a salinity of ∼2 wt.% NaCl equiv. The inclusions occurred along the same primary and pseudosecondary trails and were considered to be formed simultaneously. Based on fluid-inclusion data, the conditions of emerald growth were 250°C < T < 450°C and P = 1.5 kbar. The fluid inclusion d ata for Kianjavato emerald were compared to the data for another Madagascar emerald, Ianapera. The latter is of similar age, but its genesis was determined by a shearing event. Our fluid inclusion data suggested that shearing was also important as a mechanism of introducing CO2-rich fluid for the genesis of the Kianjavato emerald.

Original languageEnglish
Pages (from-to)141-158
Number of pages18
JournalMineralogical Magazine
Volume70
Issue number2
DOIs
StatePublished - 1 Apr 2006

Keywords

  • Fluid inclusions
  • Kianjavato and Ianapera emeralds
  • Madagascar

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