Mineralium Deposita

, Volume 46, Issue 7, pp 671–676

18O/16O and V/Cr ratios in gem tsavorites from the Neoproterozoic Mozambique metamorphic belt: a clue towards their origins?

  • Gaston Giuliani
  • Anthony E. Fallick
  • Julien Feneyrol
  • Daniel Ohnenstetter
  • Vincent Pardieu
  • Mark Saul
Letter

Abstract

The combination of oxygen isotope composition with V–Cr–Mn trace element concentrations of V-bearing garnets (tsavorites) originating from the main deposits of the Neoproterozoic Mozambique Metamorphic Belt is reported for the first time. The database enables the identification of the geological and geographical sources of the main productive areas from northern and southern Tanzania, Kenya, and Madagascar. Three consistent sets of δ18O values between 9.5‰ and 11.0‰, 11.6‰ and 14.5‰, and 15.5‰ and 21.1‰ have been recognized for primary deposits hosted in graphitic gneisses related to the Neoproterozic metasedimentary series. The δ18O value of tsavorite is a good tracer of the environment of its formation; the δ18O of the fluid in equilibrium with tsavorite was buffered by the host rock during metamorphism and fluid-rock interaction. This study is a first step in characterizing the geochemistry of gem tsavorite from most of the deposits and occurrences worldwide.

Keywords

Mozambique Metamorphic Belt Tsavorite Oxygen isotopes V/Cr ratio Mn Geographic and geologic origins 

Supplementary material

126_2011_355_MOESM1_ESM.pdf (50 kb)
ESM Table 1The oxygen isotopic composition (‰, V-SMOW) of tsavorites and other associated minerals from the tsavorite deposits of the Neoproterozoic Mozambique Metamorphic Belt (available on-line ESM) (PDF 49.8 kb)
126_2011_355_MOESM2_ESM.pdf (47 kb)
ESM Table 2The average chemical composition with the chemical formulae calculated on the basis of eight cations of tsavorite from the Neoproterozoic Metamorphic Mozambique Belt (available on-line ESM) (PDF 46.8 kb)
126_2011_355_MOESM3_ESM.pdf (14 kb)
ESM 1(PDF 13.9 kb)

Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Gaston Giuliani
    • 1
  • Anthony E. Fallick
    • 2
  • Julien Feneyrol
    • 3
  • Daniel Ohnenstetter
    • 3
  • Vincent Pardieu
    • 4
  • Mark Saul
    • 5
  1. 1.GET/IRD and C.R.P.G./C.N.R.SVandœuvre-lès-NancyFrance
  2. 2.Isotope Geosciences Unit, S.U.E.R.CGlasgowUK
  3. 3.C.R.P.G./C.N.R.SVandœuvre-lès-NancyFrance
  4. 4.GIABangkokThailand
  5. 5.Swala Gem TradersArushaTanzania

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