Abstract
Mafic dikes and dunite veins are observed in the mantle section of the Oman – United Arab Emirates (O-UAE) ophiolites, as well as diabase dikes and hydrothermal veins in the crust section. They have been systematically measured during the mapping of this ophiolite and are represented by their trajectories in the folded map 3 in the back of this volume, and by local stereoplots included in this study. Mafic dikes in the mantle section correspond to basaltic melt being injected at decreasing temperatures from above or at peridotite solidus, down to below 450 °C. Hydrothermal veins associated with dioritic dikes issued from hydrous melting of host gabbros are observed down to the base of the crust, bearing evidence for sea water penetration into basal gabbros at or above 900 °C, that is very close to the ridge axis. Dike orientations record the stress field at the time of their injection. In most places, all types of dikes are dominantly parallel to the general trend of the nearest sheeted dike complex; thus the stress field has not visibly changed from melt injection in the asthenosphere below the ridge of origin to injection in a lithosphere up to a few Myr old, at distances beyond 100 km from the axis. Local preferred orientations, when they are considered in the frame of the paleo-ridge system of O-UAE, result in a coherent model throughout the belt: the sheeted dike complex dips moderately away from the presumed ridge axis and the mantle dikes, toward this axis. These opposite directions are explained by the presumed effect of subsidence toward the axis for the sheeted dikes and by the central feeding from an asthenospheric uprise for the mantle dikes.
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References
Benoit, M., Ceuleneer, G. and Polvé, M., 1999, The remelting of hydrothermally altered peridotite at mid-ocean ridges by intruding mantle diapirs, Nature 402: 514–518.
Bodvarsson, G. and Walker, G.P.L., 1964, Crustal drift in Iceland, Geophys. J. R. Astron. Soc. 8: 285–300.
Boudier, F. and Coleman, R.G., 1981, Cross-section through the peridotite in the Samail ophiolite, southeastern Oman mountains, J. Geoph. Res. 88: 2573–2592.
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.
Boudier, F. and Nicolas, A., 1995, Nature of the Moho transition zone in the Oman ophiolite, J. Petrol. 36: 777–796.
Cassard, D., Nicolas, A., Rabinovitch, M., Moutte, J., Leblanc, M. and Prinzhofer, A., 1981, Structural classification of chromite pods in southern New Caledonia, Econ. Geol. 76: 805–831.
Ceuleneer, G., 1986, Structure des ophiolites d'Oman: flux mantellaire sous un centre d'expansion océanique et charriage à la dorsale, Unpublished thèse de Doctorat, Université de Nantes.
Ceuleneer, G., Monnereau, M. and Amri, I., 1996, Thermal structure of a fossil mantle diapir inferred from the distribution of mafic cumulates, Nature 379: 149–153.
Cormier, M.H., Macdonald, K.C. and Wilson, D.S., 1995, A threedimensional gravity analysis of the East Pacific Rise from 18 degrees to 21 degrees 30′ S, J. Geoph. Res. 100: 8063–8082.
Gnos, E. and Nicolas, A., 1996, Structural evolution of the northern end of the Oman Ophiolite and enclosed granulites, Tectonophysics 254: 111–137.
Gudmundsson, A., 1990, Emplacement of dykes, sills and crustal magma chamber at divergent plate boundaries, Tectonophysics 176: 257–275.
Hooft, E., Schouten, H. and Detrick, R.S., 1996, Constraining crustal emplacement processes from the variation in seismic layer 2A thickness at the East Pacific Rise, Earth Planet. Sci. Lett. 142: 289–309.
Ildefonse, B., Nicolas, A. and Boudier, F., 1993, Evidence from the Oman ophiolite for sudden stress changes during melt injection at oceanic spreading centres, Nature 366: 673–675.
Ildefonse, B., Billiau, S. and Nicolas, A., 1995, A detailed study of mantle flow away from diapirs in the Oman ophiolite. In R.L.M. Vissers and A. Nicolas (eds) Mantle and lower crust exposed in oceanic ridges and in ophiolites, Kluwer, Dordrecht, pp. 163–177.
Jousselin, D., 1998, Structure détaillée et propriétés sismiques des diapirs de manteau dans l'ophiolite d'Oman, Unpublished PhD, Université Montpellier II.
Jousselin, D., Nicolas, A. and Boudier, F., 1998, Detailed mapping of a mantle diapir below a paleo-spreading center in the Oman ophiolite, J. Geoph. Res. 103: 18153–18170.
Jousselin, D. and Nicolas, A., this issue, Structural mapping of an off-axis mantle diapir in theMansah region (Sumail massif in the Oman ophiolite).
Kelemen, P.B., Hirth, G., Shimizu, N., Spiegelman, M. and Dick, H.J.B., 1997, A review of melt migration processes in the adiabatically upwelling mantle beneath oceanic spreading ridges, Phil. Trans. R. Soc. London A355: 283–318.
Knight, M.D. and Walker, G.P.L., 1988, Magma flow directions in dikes of the Koolau complex, Oahu, determined from magnetic studies, J. Geoph. Res. 93: 4301–4319.
Leblanc, M. and Ceuleneer, G., 1991, Chromite crystallization in a multicellular magma flow, evidence from a chromitite dike in the Oman ophiolite, Lithos 27: 231–257.
Lee, C.E., Karson, J.A. and Hess Deep 99 Scientific Party, 1999, A New Look at fast-spread crust and the internal structure of the sheeted dike complex exposed at the Hess deep rift: a perspective from Argo-II digital image mosaics, EOS, Trans., AGU Fall meeting, 80, F984.
Lippard, S.J., Shelton, A.W. and Gass, I.G., 1986, The ophiolite of northern Oman, Geol. Soc. Mem. 11.
Michibayashi, K., Gerbert-Gaillard, L. and Nicolas, A., this issue, shear sense inversion in uppermost mantle from Hilti.
Nehlig, P., Juteau, T., Bendel, V. and Cotten, J., 1994, The root zone of oceanic hydrothermal systems: constraints from the Samail ophiolite (Oman), J. Geoph. Res. 99: 4703–4713.
Nicolas, A., 1989, Structures in ophiolites and dynamics of oceanic lithosphere, Kluwer Academic Publisher, Dordrecht, pp. 367.
Nicolas, A. and Jackson, M., 1982, High temperature dikes in peridotites: origin by hydraulic fracturing, J. Petrol. 23: 568–582.
Nicolas, A. and Al Azri, H., 1991, Chromite-rich and chromitepoor ophiolites; the Oman case. In T. Peters, A. Nicolas and R.G. Coleman (eds), Ophiolite genesis and evolution of the oceanic lithosphere, Kluwer Academic Publisher, Dordrecht, pp. 261–274.
Nicolas, A. and Boudier, F., 1991, Rooting of the sheeted dike complex in the Oman ophiolite. In: Ophiolite genesis and evolution of the oceanic lithosphere (edited by Peters, T., Nicolas, A. and Coleman, R. G.), Kluwer Academic Publisher, Dordrecht, 39–54.
Nicolas, A., Boudier, F. and Ildefonse, B., 1994, Dike patterns in diapirs beneath oceanic ridges: the Oman ophiolite. In M.P. Ryan (ed.) Magmatic systems, Academic Press, Orlando, pp. 77–95.
Nicolas, A. and Boudier, F., 1995, Mapping oceanic ridge segments in Oman ophiolites, J. Geoph. Res. 100: 6179–6197.
Nicolas, A., Boudier, F., Michibayashi, K. and Gerbert-Gaillard, in press, Aswad massif (United Arab Emirates). Archetype of the Oman-UAE ophiolite belt, Geol. Soc. Am. bull.
Nicolas, A., Boudier, F., Ildefonse, B., Ball, E., this issue, Accretion of the Oman-UAE ophiolite in a microplate system. Discussion of a new structural map.
Palmason, G., 1980, A continuum model of crustal generation in Iceland; kinematic aspects. In: W. Jacoby, A. Bjornsson and D. Moller (eds). Iceland; evolution, active tectonics and structure, J. Geoph. 47: 7–18.
Poliakov, A. and Nicolas, A., 1999, Melt extraction under MOR's: transition from channel flow to the ‘magmafracture’. J. Conf. Abstracts, EUG10, Abstract Volume, 4, 358.
Pollard, D.D., 1987, Elementary fracture mechanics applied to the structural interpretation of dykes, Geol. Assoc. canada, Spec. Paper 34, 5–24.
Rabinowicz, M., Ceuleneer, G. and Nicolas, A., 1987, Melt segregation and flow in mantle diapirs below spreading centers: evidence from the Oman ophiolite, J. Geoph. Res. 92: 3475–3486.
Raposo, M. I. B. and Ernesto, M. 1995, Anisotropy of magnetic susceptibility in the Ponta Grossa dyke swarm (Brazil) and its relationship with magma flow direction, Phys. Earth Planet. Int. 87: 183–196.
Rochette, P., Jenatton, L., Dupuy, C., Boudier, F. and Reuber, I., 1991, Diabase dikes emplacement in the Oman ophiolite: a magnetic fabric study with reference to geochemistry. In T. Peters, A. Nicolas and R.G. Coleman (eds), Ophiolite genesis and evolution of the oceanic lithosphere, Kluwer Academic Publishers, Dordrecht, pp. 55–82.
Suhr, G., 1999, Melt migration under oceanic ridges; inferences from reactive transport modelling of upper mantle hosted dunites, J. Petrol. 40: 575–599.
Woodcock, N.H. and Naylor, M.A., 1983, Randomness testing in three-dimensional orientation data, J. Struct. Geol. 5: 539–548.
Yoder, H. S., Jr. and Tilley, C. E., 1962, Origin of basalt magmas; an experimental study of natural and synthetic rock systems, J. Petrology 3: 342–529.
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Nicolas, A., Ildefonse, B., Boudier, F. et al. Dike distribution in the Oman-United Arab Emirates ophiolite. Marine Geophysical Researches 21, 269–287 (2000). https://doi.org/10.1023/A:1026718026951
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DOI: https://doi.org/10.1023/A:1026718026951