Chromite-Rich and Chromite-Poor Ophiolites: The Oman Case

  • A. Nicolas
  • H. Al Azri
Part of the Petrology and Structural Geology book series (PESG, volume 5)


Chroinite deposits in Oman belong dominantly to the concordant structural type, meaning that these have been intensely deformed by plastic flow and tectonically rotated to become parallel to the peridotite foliation. This occurred soon after their formation within the transition zone below the ridge of origin. Subconcordant and discordant pods are also present. The latter have preserved delicate magmatic structures showing that they have only been little deformed after their formation in melt-carrying conduits. Regionally, the chromite deposits have been dominantly found, so far, in restricted areas whereas large areas of Oman seem to be devoid of deposits. Maqsad, one of the largest chromite districts, was also an area of mantle diapirism below the ridge of origin. This association is well explained if it is considered that most of mantle melt feeding the crust at ridges is expected to be delivered through such diapirs. Although Oman is the largest and best exposed ophiolite in the world, it seems to be comparatively poor in chromite due to the spreading situation. In the Lherzolite Ophiolite Type (LOT), thought to be derived from slow spreading ridges, the chromite deposits are absent as a result of chromium being retained in mantle diopside during partial melting. The chromite deposits are restricted to the Harzburgite Ophiolite Type (HOT) in which chromium has passed into the melt. Although Oman belongs to the HOT group, it seems to have been a particularly fast spreading HOT. It is suggested that in such a situation the transition zone, which is the level where the chromite normally precipitates from the melt, due to temperature drop, could have remained too hot to allow for abundant chromite formation.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Ahmad, Z. and Bilgrami, S.A., 1987. Chromite deposits and ophiolites of Pakistan, In: Evolution of chromium fields, C.S. Stowe (ed), Van Nostrand Reinhold Co., New-York, pp. 239–264.Google Scholar
  2. Augé, T., 1982. Etude minéralogique et pétrographique de roches basiques et ultrabasiques du complexe ophiolitique du Nord Oman, Relations avec les chromitites comparaison avec deux complexes dArabie Saoudite, Thèse 3ème cycle, Univ. Orléans, Fr., 263 p.Google Scholar
  3. Augé, T. and Roberts, S., 1982. Petrology and geochemistry of some chromitiferous bodies within the Oman ophiolite.; Ofioliti, 7: 133–154.Google Scholar
  4. Bacuta, G.C., 1978. Geology of some Alpine-type chromite deposits in the Philippines: Manila, Philippines., Bur. Mines, unpub. Rep., 22 p.Google Scholar
  5. Boudier, F. and Nicolas, A., 1985. Harzburgites and lherzolites subtypes in ophiolitic and oceanic environments., Earth Planet. Sci. Lett., 76: 84–92.CrossRefGoogle Scholar
  6. B.R.G.M./Oman, 1985. Mineral deposits of the mountains of Northern Oman, Map 1/1,000,000, Sultanate of Oman, (Ed.)Google Scholar
  7. Brown, M.A., 1982. Chromite deposits and their ultramafic host rocks in the Oman ophiolite., Dep. Earth Sci. Open Univ., Ph. D. Thesis, 263 p.Google Scholar
  8. Burgath, K.P., Mohr, M., Ramunlmair D. and Steiner, L., 1982. The chromite potential in North Central Oman (new discoveries). Federal Inst. Geosc. Nat. Res., Hannover, unpublished Rep., 89 p.Google Scholar
  9. Cassard, D., Nicolas, A., Rabinowicz, M., Moutte, M., Leblanc, M. and Prinzhofer, A., 1981. Structural classification of chromite pods in southern New Caledonia., Econ. Geol., 76: 805–831.CrossRefGoogle Scholar
  10. Ceuleneer, G. and Nicolas, A., 1985, Structures in podiform chromite from the Maqsad district (Sumail ophiolite, Oman)., Mineral. Deposita, 20: 177–185.CrossRefGoogle Scholar
  11. Ceuleneer, G., Nicolas, A. and Boudier, F., 1988. Mantle flow patterns at an oceanic spreading centre: the Oman peridotites record., Tectonophysics, 151: 1–26.CrossRefGoogle Scholar
  12. Christiansen, F.G., 1985. Deformation fabric and microstructures in ophiolitic chromitites and host ultramafics., Sultanate of Oman, Geologische Rundschau, 74: 61–76.CrossRefGoogle Scholar
  13. Christiansen, F.G., 1986. Structures of ophiolitic chromite deposits, Thesis Lic. Scient. degree, Univ. Aarhus, Denmark.Google Scholar
  14. Detrick, R.S., Bulh, P., Vera, E., Mutter, J., Orcutt, J., Madsen, J. and Brocher, T., 1987: Multi-channel seismic imaging of a crustal magma chamber along the East Pacific Rise., Nature, 326: 35–41.CrossRefGoogle Scholar
  15. Dogan Paktunc, A., 1990. Origin of podiform chromite deposits by multistage melting, melt segregation and magma mixing in the upper mante., Ore Geol. Rev., 5: 211–222.CrossRefGoogle Scholar
  16. Engin, T, Ozkoçak, O. and Artan, U., 1987. General geological setting and character of chromite deposits in Turkey. In: Evolution of chromium fields, Stowe CX.W. (ed.), New-York, Van Nostrand Reinhold Co. pp. 195–219.Google Scholar
  17. Hock, M. and Friedrich, G., 1985. Structural features of ophiolitic chromitites in the Zambales Range, Luzon, Philippines., Mineral. Deposita, 20: 290–301.CrossRefGoogle Scholar
  18. Lago, B.L., Rabinowicz, M. and Nicolas, A., 1982. Podiform chromite ore bodies: a genetic model., J. Petrol., 23: 103–125.CrossRefGoogle Scholar
  19. Leblanc, M., 1987, Chromite in oceanic arc environments: New-Caledonia, In: Evolution of chromium ore fields, C.W. Stowe (ed.), Van Nostrand Reinhold Co, pp. 265–295.Google Scholar
  20. Leblanc, M. and Violette, J.F., 1983. Distribution of aluminium-rich and chromium-rich chro-mite pods in ophiolite peridotites., Economic Geology, 78: 293–301.CrossRefGoogle Scholar
  21. Malpas, J. and Strong D.F., 1975. A comparison of chromite-spinels in ophiolites and mantle diapirs of Newfoundland., Geochim. Cosmochim Acta, 39: 1045–1060.CrossRefGoogle Scholar
  22. Nicolas, A., 1986. Structure and petrology of peridotites., Rev. Geophys., 24: 875–895.CrossRefGoogle Scholar
  23. Nicolas, A., 1989. Structures of Ophiolites and dynamics of oceanic lithosphere, Kluwer Ed., 367 p.Google Scholar
  24. Nicolas, A. and Violette, J.F., 1982. Mantle flow at oceanic spreading centers: models derived from ophiolites., Tectonophysics, 81: 319–339.CrossRefGoogle Scholar
  25. Nicolas, A., Reuber, I. and Benn, K., 1988. A new magma chamber model based on structural studies in the Oman ophiolite., Tectonophysics, 151: 87–105.CrossRefGoogle Scholar
  26. Pantakis, M.T., 1980. Chromite mineralization associated with the Troodos ophiolite, Cyprus, International Symposium on Metallogeny of mafic and ultramafic complexes of the eastern Mediterranean and western Asian area and its comparison with similar metallogenic environments of the word, pp. 91–97. Athens: UNESCO IGCP Publication, 1, National Technical Univ., Athens.Google Scholar
  27. Rabinowicz, M., Nicolas, A. and Vigneresse, J.L., 1984. A rolling mill effect in asthenospheric beneath oceanic spreading centers., Earth Planet. Sci. Lett., 67: 97–108.CrossRefGoogle Scholar
  28. Rabinowicz, M., Ceuleneer, G. and Nicolas, A., 1987. Melt segregation and flow in mantle diapirs below spreading centers: evidence from the Oman ophiolites., J. Geophys. Res., 92: 3475–3486.CrossRefGoogle Scholar
  29. Rassios, A. and Vacondios, I., 1986. Chromite mineralization and Mining at Vourinos., EEC Internal Rep., Athens, pp. 128–142.Google Scholar
  30. Roberts S., 1988. Ophiolitic chromitite formation: a marginal basin phenomenon?, Econ. Geology, 83: 1034–1036.CrossRefGoogle Scholar
  31. Thayer, T.P., 1969. Gravity differenciation and magmatic re-emplacement of podiform chromite deposits., Econ. Geol. Monogr., 4: 132–146.Google Scholar
  32. Thayer, T.P. and Lipin B.R., 1978. A geological analysis of world chromite production to the year 2000 A.D., Proceedings 107th Annual Meeting Council of Economics of AIME, pp. 143–146.Google Scholar
  33. Vacondios, I., 1986. Chromite mine in Tsangli, Workshop on Greek ophiolites., Inst. Geol. Min. Expl., Athens, pp. 55–57.Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1991

Authors and Affiliations

  • A. Nicolas
    • 1
  • H. Al Azri
    • 2
  1. 1.Laboratoire de Tectonophysique, URA 1370 CNRSUniversité Montpellier IIMontpellierFrance
  2. 2.Ministry of Petroleum and MineralsMuscatOman

Personalised recommendations