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Diabase Dikes Emplacement in the Oman Ophiolite: A Magnetic Fabric Study with Reference to Geochemistry

  • P. Rochette
  • L. Jenatton
  • C. Dupuy
  • F. Boudier
  • I. Reuber
Part of the Petrology and Structural Geology book series (PESG, volume 5)

Abstract

The anisotropy of magnetic susceptibility, coupled with geochemical identification of magma sources, has been investigated in 360 samples from 67 basaltic dikes of the sheeted dike complex of the Oman ophiolite. Two thirds of the analysed dikes have MORB affinities, while the others, previously related to island arc setting, show REE patterns and trace elements evolution more in agreement with an off-axis ridge magmatism and an interaction between magma and ultramafic country rocks. Only half of the dikes yield primary flow fabrics with a minimum magnetic axis K3 close to dike pole and a maximum axis Kl parallel to flow line. Secondary fabrics, mainly with Kl parallel to dike pole, are more likely to occur in thick (≥1.5 m) dikes with high susceptibility and MORB composition. Flow lines appear quite dispersed with an overall tendency toward vertical flow. Dikes of the end of emplacement. This shear could be a signature of oblique spreading during the accretion of the Omani oceanic crust MORB type composition show a distinct obliquity of their flow plane relative to dike margins, suggesting that the dikes were horizontally sheared at the end of emplacement. This shear could be a signature of oblique spreading during the accretion of the Omani oceanic crust.

Keywords

Flow Line Secondary Fabric Magnetic Foliation Dextral Shear Oman Ophiolite 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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References

  1. Alabaster, T., Pearce, J.A. and Malpas, J., 1982. The volcanic stratigraphy and petrogenesis of the Oman ophiolite Complex. Contrib. Mineral. Petrol., 82: 168–183.CrossRefGoogle Scholar
  2. Beurrier, M., Ohnenstetter, M., Cabanis, B., Lescuyer, J.L., Tegyey, M. and Le Métour, J., 1989. Géochimie des filons doléritiques et des roches volcaniques ophiolitiques de la nappe de Semail: contraintes sur leur origine géotectonique au Crétacé Supérieur. Bull. Soc. Géol. Fr., 8: 205–219.Google Scholar
  3. Boudier, F., Bouchez, J.L., Nicolas, A., Cannat, M., Ceuleneer, G., Misseri M. and Montigny R., 1985. Kinematics of oceanic thrusting in the Oman ophiolite: model of plate convergence. Earth Planet. Sci. Lett., 75: 215–222.CrossRefGoogle Scholar
  4. Boudier, F., Ceuleneer, G. and Nicolas, A., 1988. Shear zones, thrusts and related magmatism in the Oman ophiolite: initiation of thrusting on an oceanic ridge. Tectonophysics, 151: 275–296.CrossRefGoogle Scholar
  5. Boudier, F., Nicolas, A. and Ceuleneer, G., 1989. De l’accretion océanique à la convergence. Le cas de l’ophiolite d’Oman. Bull. Soc. Géol. France, 8: 221–230.Google Scholar
  6. Coleman, R.G., 1981. Tectonic setting for ophiolite obduction in Oman. J. Geophys. Res., 86: 2497–2508.CrossRefGoogle Scholar
  7. Dauteuil, O., Brun, J.P., Avedik, F. and Geli, L., 1990. Structures of the oblique rifting in the Mohns ridge (Norwegian Sea), C.R. Acad. Sci. Paris, 311: 357–363.Google Scholar
  8. Dawson, E.M. and Hargraves, R.B., 1985. Anisotropy of magnetic susceptibility as an indicator of magma flow directions in diabase dikes. EOS Trans. AGU, 66: 251.Google Scholar
  9. Dosso, L., Bougault, H., Beuzart, P., Calvez, J.Y. and Joron, J.L., 1988. The geochemical structure of the South East Indian Ridge. Earth Planet. Sci. Lett., 88: 47–59.CrossRefGoogle Scholar
  10. Ellwood, B.B., 1978. Flow and emplacement directions determined for selected magmatic bodies using anisotropy of magnetic susceptibility measurements. Earth Planet. Sci. Lett., 41: 254–264.CrossRefGoogle Scholar
  11. Hrouda, F., 1982. Magnetic anisotropy of rocks and its application in geology and geophysics. Geophys. Surv., 5: 37–82.CrossRefGoogle Scholar
  12. Hrouda, F., 1985. The magnetic fabric of the Brno massif. Sbor. geol. ved, 19: 89–112.Google Scholar
  13. Jeffrey, G.H., 1922. The motion of ellipsoidal particles emersed in a viscous fluid. Proc. R. Soc. London ser. A, 102: 161–179.CrossRefGoogle Scholar
  14. Jelinek, V., 1978. Statistical processing of anisotropy of magnetic susceptibility measured on group of specimens. Studia Geophys. Geodet., 22: 50–62.CrossRefGoogle Scholar
  15. Kelemen, P.B., Joyce, D.B., Webster, J.D. and Holloway, J.R., 1990. Reaction between ultramafic rock and fractionating basaltic magma - II - Experimental investigation of reaction between olivine tholeiite and harzburgite at 1150°-1050°C and 5 kb. J. Petrol., 31: 99–134.CrossRefGoogle Scholar
  16. Khan, M.A., 1962. The anisotropy of magnetic susceptibility of some igneous and metamorphic rocks, J. Geophys. Res., 67: 2873–2885.CrossRefGoogle Scholar
  17. Kidd, R.G.W. and Cann, J.R., 1974. Chilling statistics indicate on ocean floor spreading origin for the Troodos complex, Cyprus. Earth Planet. Sci. Lett., 24: 151–155.CrossRefGoogle Scholar
  18. Knight, M.D. and Walker, G.P., 1988. Magma flow directions in dikes of the Koolau complex, Oahu, determined from magnetic fabric studies. J. Geophys. Res., 93: 4301–4319.CrossRefGoogle Scholar
  19. Luyendick, B.P., Laws, B.R., Day, R. and Collinson, T.B., 1982. Paleomagnetism of the Samail ophiolite, Oman 1. The sheeted dike complex at Ibra. J. Geophys. Res., 87: 10883–10902.CrossRefGoogle Scholar
  20. Mc Culloch, M.T., Gregory, R.T., Wasserburg, G.J. and Taylor, H.P., 1981. Sm-Nd, Rb-Sr and O18/O16 isotopic systematics in an oceanic crustal section: evidence from the Samail ophiolite. J. Geophys. Res., 86: 2721–2735.CrossRefGoogle Scholar
  21. Michard, A., Montigny, R. and Schlich, R.. 1986. Geochemistry of the mantle beneath the Rodriguez Triple junction and the South-East Indian Ridge. Earth Planet. Sci. Lett., 78: 104–114.CrossRefGoogle Scholar
  22. Montigny, R., Le Mer, O., Thuizat, R. and Withechurch, H., 1988. K-Ar and 40Ar/39Ar study of metamorphic rocks asociated with the Oman ophiolite: tectonic implications. Tectonophysics, 151: 345–262.CrossRefGoogle Scholar
  23. Nehlig, P., 1989. Etude d’un système hydrothermal fossile: l’ophiolite de Semail (Oman). Thèse Doc. Univ. Brest, 308 p.Google Scholar
  24. Nicolas, A.. 1989. Structures of ophiolites and dynamics of oceanic lithosphere. Kluwer ed., London, 367 pp.CrossRefGoogle Scholar
  25. Nicolas, A., Ceuleneer, G., Boudier, F. and Misseri, M., 1988a. Structural mapping in the Oman ophiolites: mantle diapirism along an oceanic ridge. Tectonophysics, 151: 27–56.Google Scholar
  26. 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
  27. Pallister, J.S., 1981. Structure of the sheeted dike complex of the Samail ophiolite near Ibra, Oman. J. Geophys. Res.. 86: 2661–2672.CrossRefGoogle Scholar
  28. Park, J.K., Tanczyk, E. and Desbarats, A., 1988. Magnetic fabric and its significance in the 1400 Ma Mealy diabase dikes of Labrador, Canada, J. Geophys. Res. 93: 4301–4319.CrossRefGoogle Scholar
  29. Pearce, J.A., Alabaster, T., Shelton, A.W. and Searle, M.P., 1981. The Oman ophiolite as a Cretaceous arc-basin complex: evidences and implications. Phil. Trans. R. Soc. London, 300: 299–317.CrossRefGoogle Scholar
  30. Pecher, A., 1989. Schmidt Mac, a program to display and analyse directionnal data. Computer & Geosciences. 15: 1315–1326.CrossRefGoogle Scholar
  31. Potter, D.K. and Stephenson, A., 1988. Single-domain particles in rocks and magnetic fabric analysis. Geophys. Res. Lett. 15: 1097–1100.CrossRefGoogle Scholar
  32. Rautenschlein, M., Jenner, G.A., Hertogen J., Hofmann A.W., Kerricn R., Schmincke, H.U. and White, W.M., 1985. Isotopic and trace element composition of volcanic glasses from the Akaki Canyon, Cyprus. implication for the origin of the Troodos ophiolite. Earth Planet. Sci. Lett.. 75: 369–383.CrossRefGoogle Scholar
  33. Reuber, I.. 1988. Complexity of the crustal sequence in northern Oman ophiolite (Fizh and southern Aswad block): the effect of early slicing ? Tectonophysics. 151: 137–165.CrossRefGoogle Scholar
  34. Rochette, P.. 1988. Inverse magnetic fabric in carbonate bearing rocks, Earth planet. Sci. Lett.. 90: 229–237.CrossRefGoogle Scholar
  35. Sempéré, J.C., Purdy, G.M. and Schouten, S., 1990. Segmentation of the Mid-Atlantic Ridge between 24°N and 30°40’N. Nature, 344: 427–431.CrossRefGoogle Scholar
  36. Shelton, A.W., 1984. Geophysical studies on the northern Oman ophiolite. Ph. D. Thesis, Open Univ. Milton Keynes, 353 pp.Google Scholar
  37. Shelley, D., 1985. Determining paleo-flow directions from groundmass fabrics in the Lyttelton radial dikes. J. Volcanol Geotherm. Res., 25: 69–79.CrossRefGoogle Scholar
  38. Tapponnier, P., Armijo, R., Manighettti, I. and Courtillot, V., 1990. Bookshelf faulting and horizontal block rotations between overlapping rifts in southern Afar. Geophys. Res. Lett., 17: 1–4.CrossRefGoogle Scholar
  39. Thomas, V., Pozzi, J.P. and Nicolas, A., 1988. Paleomagnetic results from Oman ophiolites related to their emplacement. Tectonophysics, 151: 297–322.CrossRefGoogle Scholar
  40. Viereck, L.G., Flower, M.F.J., Hertogen, J., Schmincke, H.U. and Jenner, G.A., 1989. The genesis and significance of N-MORB sub-types. Contrib. Mineral. Petrol., 102: 112–126.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1991

Authors and Affiliations

  • P. Rochette
    • 1
  • L. Jenatton
    • 1
  • C. Dupuy
    • 2
  • F. Boudier
    • 2
  • I. Reuber
    • 2
  1. 1.LGIT, Observatoire de GrenobleGrenoble CedexFrance
  2. 2.Université Scientifique et Technique du LanguedocMontpellier CedexFrance

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