Mineralium Deposita

, Volume 46, Issue 7, pp 671–676 | Cite as

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 

Notes

Acknowledgements

We thank Dr. Khan T., University of Bahria, Islamabad, Pakistan, Dr. Uher P., Comenius University, Bratislava, Slovakia, Dr. Themelis T., gemologist in Thailand, and Prof. Shiraishi K., National Institute of Polar Research, Tokyo, Japan for providing samples from respectively Jambil, Pezinok, Mogok and Sør Rondane Mountains. The authors thank very much Prof. Dr. Chris Harris, University of Cape Town, Rondebosch, RSA, for reviewing, Dr. Hartwig Frimmel for handling the manuscript, and Dr. Bernd Lehmann, Editor-in-Chief of Mineralium Deposita.

Supplementary material

126_2011_355_MOESM1_ESM.pdf (50 kb)
ESM Table 1 The 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 2 The 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)

References

  1. Bridges CR (1974) Green grossularite garnets (tsavorites) in East Africa. Gems Gemology 14:290–295Google Scholar
  2. Feneyrol J, Giuliani G, Ohnenstetter D, Le Goff E, Malisa E, Saul M, Saul E, Saul J, Pardieu V (2010) Lithostratigraphic and structural controls of tsavorite deposits at Lemshuku, Merelani area, Tanzania. C R Geosci 342:778–785CrossRefGoogle Scholar
  3. Garnier V, Giuliani G, Ohnenstetter D, Fallick AE, Dubessy J, Banks D, Hoàng Quang V, Lhomme Th, Maluski H, Pêcher A, Bakhsh KA, Van Pham L, Phan Trong T, Schwarz D (2008) Marble-hosted ruby deposits from central and southeast Asia: towards a new genetic model. Ore Geol Rev 34:169–191CrossRefGoogle Scholar
  4. Giuliani G, Fallick AE, Garnier V, France-Lanord Ch, Ohnenstetter D, Schwarz D (2005) Oxygen isotope composition as a tracer for the origins of rubies and sapphires. Geology 33:249–252CrossRefGoogle Scholar
  5. Giuliani G, Ohnenstetter D, Palhol F, Feneyrol J, Boutroy E, De Boissezon H, Lhomme Th (2008) Karelianite and vanadian phlogopite from the Merelani Hills, gem zoisite deposits, Tanzania. Can Min 46:1183–1194CrossRefGoogle Scholar
  6. Hussain S (2005) Geology of the indus suture zone and high himalayan crystalline block west of Besham syntaxis and study of some associated minerals. Unpublished Ph.D. thesis, The University of Lahore, Pakistan. p 510Google Scholar
  7. Key RM, Hill PG (1989) Further evidence for the controls on the growth of vanadium grossular garnets in Kenya. J Gemmol 21:412–422Google Scholar
  8. Le Goff E, Deschamps Y, Guerrot C (2010) Tectonic implications of new single zircon Pb-Pb evaporation data in the Lossogonoi and Longido ruby-districts. Mozambican metamorphic Belt of north-eastern Tanzania. CR Geosci 342:36–45CrossRefGoogle Scholar
  9. Lichtenstein U, Hoernes S (1992) Oxygen isotope fractionation between grossular-spessartine garnet and water: an experimental investigation. Eur J Miner 4:239–249Google Scholar
  10. Malisa E (1987) Geology of the tanzanite gemstone deposits in the Lelatema area, NE Tanzania. Ph.D. thesis, University of Helsinski, Finland, Annale-Academiae Scientiarum Fennicae, Series A III: Geologica-Geographica. p 146Google Scholar
  11. Malisa E (1998) Application of graphite as a geothermometer in hydrothermally altered metamorphic rocks of the Merelani-Lelatema area, Mozambique belt, northeastern Tanzania. J Afr Earth Sci 26:313–316CrossRefGoogle Scholar
  12. Malisa E, Muhongo S (1990) Tectonic setting of gemstone mineralization in the Proterozoic metamorphic terrane of the Mozambique Belt in Tanzania. Precambrian Res 46:167–176CrossRefGoogle Scholar
  13. Meert JG (2003) A synopsis of events related to the assembly of eastern Gondwana. Tectonophysics 362:1–40CrossRefGoogle Scholar
  14. Mercier A, Moine B, Delorme J, Rakotondrazafy MAF (1997) A note on a new occurrence of vanadian grossular garnet from Madagascar. J Gemmol 25:391–393Google Scholar
  15. Muhongo S, Tuisku P, Mtoni Y (1999) Pan-African pressure-temperature evolution of the Merelani area in the Mozambique belt in northeast Tanzania. J Afr Earth Sci 29:353–365CrossRefGoogle Scholar
  16. Olivier B (2006) The geology and petrology of the Merelani tanzanite deposit, NE Tanzania. Ph.D. thesis, Stellenbosch University, South Africa. p 434Google Scholar
  17. Osanai Y, Ueno T, Tsuchiya N, Takahashi Y, Tainosho Y, Shiraishi K (1990) Finding of vanadium-bearing garnet from the Sør Rondane Mountains, East Antarctica. Antarct Rec 34:279–291Google Scholar
  18. Pardieu V, Hughes RW (2008) Tsavorite-the untamed beauty. Incolor 9:12–20Google Scholar
  19. Pohl W, Niedermayr G (1978) Geology of the Mwatate Quadrangle and the vanadium grossularite deposits of the area. Geol Surv Kenya Rep 101:55Google Scholar
  20. Suwa K, Suzuki K, Agata T (1996) Vanadium grossular from the Mozambique metamorphic rocks, south Kenya. J S Asian Earth Sci 14:299–308CrossRefGoogle Scholar
  21. Themelis T (2008) Gems and mines of Mogok, Themelis edition. Ted Themelis, Thailand, p 352Google Scholar
  22. Uher P, Kovacik M, Kubis M, Shtukenberg A, Ozdin D (2008) Metamorphic vanadian-chromian silicate mineralization in carbon-rich amphibole schists from the Malé Karpaty Mountains, Western Carpathians, Slovakia. Am Miner 93:63–73CrossRefGoogle Scholar
  23. Walton L, Marshall D (2007) Tanzanite and tsavorite. Miner Assoc Can Short Course 37:153–160Google Scholar
  24. Wight W, Grice JD (1982) Grossular garnet from the Jeffrey mine, Asbestos, Quebec, Canada. J Gemmol 18:126–130Google Scholar

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

Personalised recommendations