Abstract
The model of a large steady state magma chamber for the crystallization of ophiolitic cumulates encounters a number of geophysical problems, and has not been evidenced in present day oceans. Detailed mapping in several areas of the Oman ophiolite has shown a complex structure for the plutonic sequence that is more likely the product of superposed magmatic events, than of fractional crystallization in one huge magma chamber.
In the Salahi massif (northern Oman), though known for its regular, flat lying cumulate sequence, it can be shown that:
-
the tectonites-cumulates transition (MOHO) is an irregular, domed surface;
-
distinct layers are commonly sills;
-
layers marked by grain size variations may be due to recrystallisation;
-
magmatic lineations may be dispersed on the same outcrop from one layer to the next;
-
steepening of layers is a very early event;
-
gabbros with a dominantly linear fabric in near to vertical position appear to trace feeder zones, that are in relation with wehrlites rooted in dunite domes.
Consequently successive cycles of magma generation and intrusion can be traced in the studied area.
These structures can be related to the progressive inflation of the transition zone, that consequently becomes unstable and intrudes upwards into more or less solidified pre-existing plutonics. Large amounts of magma appear to be injected as sills, that give the sequence its distinctly layered aspect.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Preview
Unable to display preview. Download preview PDF.
Similar content being viewed by others
References
Alabaster, T., Pearce, J.A. and Malpas, J., 1982. The volcanic stratigraphy and petrogenesis of the Oman ophiolite complex. Contr. Mineral. Petrol., 81: 168–183.
Bédard, J.H., Sparks, R.S.J., Renner, R., Cheadle, M.J. and Hallworth, M.A., 1988. Peridotite sills and metasomatic gabbros in the eastern layered series of the Rhum complex. J. Geol. Soc. London, 145: 207–224.
Benn, K. and Allard, B., 1989. Preferred mineral orientations related to magmatic flow in ophiolite layered gabbros. J. Petrol., 1989: 925–946.
Beurrier, M., 1987. Géologie de la nappe ophiolitique de Samail dans les parties orientale et centrale de l’Oman. Thèse Doc. Etat, Paris 6, 406p.
Beurrier, M., 1990. The ophiolites of the central Oman mountains: an example of propagating rift into former oceanic crust. Symp. ophiol. genesis and evol. oc. lithosphere, Muscat-Oman, abstract.
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 and Planet. Sci. Lett., 75: 215–221.
Campbell, I.H. and Turner, J.S., 1986. The influence of viscosities on fountains in magma chambers. J. Petrol. 27: 1–30.
Ceuleneer, G., 1986. Structure des ophiolites d’Oman: flux mantellaire sous un centre d’expansion océanique et charriage à la dorsale. Thèse Doc. Univ. Nantes, 217 p.
Coleman, R.G., 1981. Tectonic setting for ophiolite obduction in Oman. J. geophys. Res., 86: 2497–2508.
Detrick, R.S., Bulh, P., Vera, E., Mutter, J., Orcutt, J., Madsen, J. and Brocher, T., 1987. Multichannel seismic imaging of a crustal magma chamber along the East Pacific Rise. Nature, 326: 35–41.
Ernewein, M., 1987. Histoire magmatique d’un ségment de crotte océanique téthysienne: pétrologie de la séquence plutonique du massif ophiolitique de Salahi (nappe de Semail, Oman). Thèse Doc. Univ. Strasbourg, 205 p.
Ernewein, M. and Whitechurch, H., 1986. Les intrusions ultrabasiques de la séquence crustale de l’ophiolite d’Oman: un évènement témoin de l’extinction d’une zone d’accrétion océanique? C.R. Acad. Sci. 303: 379–384.
Ernewein, M., Pflumio, C. and Whitechurch, H., 1988. The death of accretion zone as evidenced by the magmatic history of the Sumail ophiolite (Oman). Tectonophysics, 247–274.
Fisk, M.R., 1986. Basalt magma interaction with harzburgite and the formation of high-magnes-ium andesites. Geophys. Res. Lett., 13: 467–470.
Gass, I.G. et al., 1980. The Open University Oman Project - map 2.
Greenbaum, D., 1972. Magmatic processes at ocean ridges: evidence from the Troodos massif, Cyprus. Nature, 238: 18–21.
Hale, L.D., Morton, C.J. and Sleep, N.H., 1982. Reinterpretation of seismic reflection data over the East Pacific rise. J. geophys. Res., 87: 7707–7717.
Huppart, H.E. and Sparks, R.S.J., 1980. The fluid dynamics of basaltic magma replenished by influx of hot dense ultrabasic magma. Contrib. Mineral. Petrol., 75: 279–289.
Huppart, H.E., Sparks, R.S.J. and Turner, J.S.,1983. Laboratory investigations of viscous effects in replenished magma chambers. Earth PLanet. Sci. Lett. 65: 377–381.
Huppart, H.E., Sparks, R.S.J., Whitehead, J.A. and Hallworth, M.A., 1986. Replenishment of magma chambers by light inputs. J. Geophys. Res. 91: 6113–6122.
Juteau, T., Ernewein, M., Reuber, I., Whitechurch, H. and Dahl, R., 1988a. Duality of magmatism in the plutonic sequence of the Sumail nappe, Oman. Tectonophysics, 151: 107–135.
Juteau, T., Cannat, M. and Lagabrielle, Y., 1988b. Peridotites in the upper oceanic crust away from transform zones: a comparison of the results of previous DSDP and ODP legs. Proc. ODP, Init. Repts, pp. 106–109.
Karson, J.A. and Winters, A.T., 1987. Tectonic extension on the Mid-Atlantic Ridge. EOS, 68: 1508.
Karson, J.A., Thompson, G., Humphris, S.E., Edmond, J.M., Bryan, W.B., Brown, J.R., Winters, A.T., Pockalny, R.A., Casey, J.F., Campbell, A.C., Klinkhammer, G., Palmer, M.R., Kinzler, R.J. and Sulanowska, M.M., 1987. Along-axis variations in seafloor spreading in the MARK area. Nature, 328: 681–685.
Kelemen, P.B., 1990. Reaction between ultramafic rock and fractionating basaltic magma I. Phase relations, the origin of calc-alkaline magma series, and the formation of discordant dunite. J. Petrology, 31: 51–98.
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. Petrology, 31: 99–134.
Kusznir, N.J., 1980. Thermal evolution of the oceanic crust; its dependence on spreading rate and effect on crustal structure. Geophys. J. r. astron. Soc., 61: 167–181.
Lewis, B.T.R., 1983. The process of formation of ocean crust. Science, 220: 151–157.
Lippard, S.J., Shelton, A.W. and Gass, I.G., 1986. The ophiolite of Northern Oman. Geol. Soc. London Mem., 11, 178 p.
Lister, C.R.B., 1977. Qualitative models of spreading center processes, including hydrothermal penetration. Tectonophysics, 37: 203–218.
Lister, C.R.B., 1983. On the intermittency and crystallization mechanisms of sub-seafloor magma chambers. Geophys. J. r. Astron. Soc., 73: 351–365.
Lister, C.R.B., (in press). The upward migration of self-convecting magma bodies.
McClain, J.S., Orcutt, J.A., and Burnett, M., 1985. The East Pacific Rise in cross section: a seismic model. J. geophys. Res., 90: 8627–8639.
McLeod, C.J. and Reuber, I., 1990. Complex rift geometry in the northern Oman ophiolite: a possible overlapping spreading center. Symp. ophiol genesis and evol. oc. lithosphere, Muscat-Oman (abstract).
Nicolas, A., 1989. Structures of ophiolites and dynamics of oceanic lithosphere. Kluwer Academic Publishers, 666p.
Nicolas, A., Ceuleneer, G., Boudier, F. and Misseri, M., 1988a. A structural mapping in the Oman ophiolites: mantle diapirism along an oceanic ridge. Tectonophysics, 151: 27–56.
Nicolas, A., Reuber, I. and Benn, K., 1988a. A new magma chamber model based on structural studies in the Oman ophiolite. Tectonophysics, 151: 87–105.
Nicolas, A., Pallister, J. and Ceuleneer, G., 1990. The ophiolite of southern Oman mountains, mantle diapir and transform zone in the Sumail and Wadi Tayin massifs. Symp. ophiol genesis and evol. oc. lithosphere, Muscat-Oman, Excusion C, guidebook, 35p.
Nehlig, P., 1989. Etude d’un système hydrothermal océanique fossile: l’ophiolite de Semail, Oman.Thèse Doc. Univ. Brest, 313 p.
Pallister, J.S. and Hopson, C.A., 1981. Samail ophiolite plutonic suite: field relations, phase variation, cryptic variation and layering, and a model of a spreading ridge magma chamber. J. geophys. Res., 86: 2593–2644.
Parrot, J.F. and Ricou, L.E., 1976. Evolution des assemblages ophiolitiques au cours de l’expansion océanique. Cahiers ORSTOM Sér. Geol., 7: 49–68.
Parsons I. (ed.) 1987. Origins of Ignous Layering, NATO ASI series 196, 666p.
Pflumio, C., 1988. Histoire magmatique et hydrothermale du Bloc de Salahi: Implications surl’origine et l’évolution de l’ophiolite de Semail (Oman). Thèse Doc. Ecole des Mines, Paris,243 p.
Pflumio, C., Michard, A. and Juteau, T. (in prep.): Petrology and Geochemistryof the volcanic sequence of the Salahi block (Northern Oman): Implications for the origin and evolution of the Sumail ophiolite.
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.
Rabinowicz, M., Ceuleneer, G. and Nicólas, A., 1987. Melt segregation and flow in mantle diapirs below spreading centers: evidence from the Oman ophiolites. J. geophys. Res., 92: 3475–3486.
Robins B., Haukvik, L. and Jansen, S., 1987. The organization and internal structures of cyclic units in the Honningsvag intrusive suite, north-Norway: implications for intrusive mechanisms, double diffusive convection, and pore magma infiltration. In: Parsons I. (ed.) Origins of Ignous Layering, NATO ASI series 196: 287–312.
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.
Reuber, I., 1990. Geométrie et dynamique de l’accrétion dans les ophiolites téthysiennes: Himalaya du Ladakh, Oman, Turquie. Thèse d’état, Univ. de Brest, pp. 389–612.
Reuber, I. (in press). Diapiric magma intrusions in the plutonic sequence of the Oman ophiolite traced by the geometry and flow pattern of the cumulates. Proc. Symposium on Diapirism, Bandarabbas-Iran.
Reuber, I., Nehlig, P. and Juteau, T. (in press). Axial segmentation at a fossil oceanic spreading center: off-axis mantle diapir and advancing ridge tip in the Haylayn block (Semail nappe, Oman). J. Geodynamics
Smewing, J.D., 1980. An upper Cretaceous ridge-transform intersection in the Oman ophiolite. In: Proc. Inter. Ophiolite Symp., Geol. Surv. Dept. Cyprus, pp. 407–413.
Author information
Authors and Affiliations
Editor information
Rights and permissions
Copyright information
© 1991 Springer Science+Business Media Dordrecht
About this paper
Cite this paper
Reuber, I. (1991). Geometry and Flow Pattern of the Plutonic Sequence of the Salahi Massif (Northern Oman Ophiolite)-A Key to Decipher Successive Magmatic Events. In: Peters, T., Nicolas, A., Coleman, R.G. (eds) Ophiolite Genesis and Evolution of the Oceanic Lithosphere. Petrology and Structural Geology, vol 5. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-3358-6_6
Download citation
DOI: https://doi.org/10.1007/978-94-011-3358-6_6
Publisher Name: Springer, Dordrecht
Print ISBN: 978-94-010-5484-3
Online ISBN: 978-94-011-3358-6
eBook Packages: Springer Book Archive