Elsevier

Tectonophysics

Volume 151, Issues 1–4, 1 September 1988, Pages 247-274
Tectonophysics

The death of an accretion zone as evidenced by the magmatic history of the Sumail ophiolite (Oman)

https://doi.org/10.1016/0040-1951(88)90248-XGet rights and content

Abstract

The ophiolitic crustal sequence of the Salahi block in the northern part of Oman shows a complex magmatic history. The oceanic accretion episode led to the formation of a main plutonic sequence consisting of layered cumulates, isotropic gabbros, a sheeted dike complex and a first tholeiitic lava series (V1) depleted in compatible elements. The second magmatic episode immediately following the accretion stage is illustrated by predominantly ultrabasic intrusions crosscutting the main plutonic sequence and by a second volcanic suite (V2) directly linked, as can be seen from field evidence, to more differentiated high-level intrusive plutons. This volcanic unit includes very primitive members and is in general characterized by depletion in incompatible elements. A third volcanic event (V3) exhibiting a transitional character enriched in LREE's. caps the ophiolite. These V3 lavas are separated from the V2 unit by a 15 m thick pelagic sedimentary section.

A geotectonic evolution of the Sumail ophiolite is proposed on the basis of field, mineralogical and geochemical data. After the oceanic accretion phase that gave birth to the main ophiolitic sequence, a second-stage melting of the upper mantle is suggested to explain the genesis of the second magmatic episode. Such a model accounts well for the depleted character of the V2 lavas. The compression linked to the beginning of the intra oceanic detachment allows the extraction from the mantle of these second-stage melts which are then emplaced in the crust and partly extruded. The V3 volcanism postdates the intraoceanic detachment of the ophiolite, but precedes its obduction onto the Arabian continental margin. It is interpreted as an intraplate seamount-type magmatism.

References (77)

  • T Alabaster et al.

    The volcanic stratigraphy and location of massive sulfide deposits in the Oman ophiolite

  • T Alabaster et al.

    The volcanic stratigraphy of the Oman ophiolite complex

    Contrib. Mineral. Petrol.

    (1982)
  • M Beurrier

    Géologie de la nappe ophiolitique de Samail dans les parties orientale et centrale des montagnes d'Oman

  • M Beurrier et al.

    Biostratigraphie des radiolarites associées aux volcanites ophiolitiques de la nappe de Samail (Sultanat d'Oman): conséquences tectogénétiques

    C. R. Acad. Sci. Paris, Sér. 2

    (1987)
  • E Bonatti

    Metal deposits in the oceanic lithosphere

  • F Boudier et al.

    Cross section through the peridotite in the Samail ophiolite, southeastern Oman mountains

    J. Geophys. Res.

    (1981)
  • F Boudier et al.

    Les ophiolites des nappes de Semail (Oman): structures internes des massifs de Nakhl et de Rustaq

    Sci. Géol. Bull.

    (1983)
  • H Bougault et al.

    Alteration, fractional crystallization, partial melting and mantle properties from trace elements in basalts recovered in the North Atlantic

  • P Browning

    Cryptic variation within the cumulate sequence of the Oman ophiolite: magma chamber depth and petrological implications

  • P Browning et al.

    Processes in magma chambers beneath spreading axes: evidence from magmatic associations in the Oman ophiolite

    J. Geol. Soc. London

    (1981)
  • R.E Burns et al.

    Site reports 203 and 205

    R.E Burns et al.

    Site reports 203 and 205

  • W.E Cameron et al.

    Petrographic dissimilarities between ophiolitic and ocean floor basalts

  • G Ceuleneer

    Structures des ophiolites d'Oman: flux mantellaire sous un centre d'expansion océanique et charriage à la dorsale

  • R.G Coleman

    Geotimes

    (1975)
  • R.G Coleman

    Ophiolites, Ancient Oceanic Lithosphere

  • R.G Coleman

    Tectonic setting for ophiolite obduction in Oman

    J. Geophys. Res.

    (1981)
  • Intraoceanic tectonism on the Gorringe Bank: observations by submersible

  • R Dahl

    Etude géométrique, pétrologique et géochimique de la séquence crustale de l'ophiolite d'Oman, massif de Rustaq (bloc d'Haylayn). Un modèle tridimentionnel de zone d'accrétion

  • R Dahl et al.

    Ophiolites des nappes de Semail (Oman): nouvelles données de terrain sur les parties plutoniques supérieures des massifs de Rustaq et de Nakhl

    Sci. Géol. Bull.

    (1983)
  • R.A Duncan et al.

    Role of multistage melting in the formation of oceanic crust

    Geology.

    (1980)
  • M Ernewein

    Histoire magmatique d'un segment de croûte océanique téthysienne: pétrologie de la séquence plutonique du massif ophiolitique de Salahi (nappe de Semail, Oman)

  • M Ernewein et al.

    Les intrusions ultrabasiques de la séquence crustale de l'ophiolite d'Oman: un événement témoin de l'extinction d'une zone d'accrétion océanique?

    C. R. Acad. Sci. Paris, Sér. 2

    (1986)
  • M Ernewein et al.

    Plutonic sequences of Cretaceous Tethyan ophiolites in Turkey and Oman: implications for magma chamber geometry and liquid evolutions beneath accretion zones

  • A Ewart

    Mineralogy and chemistry of modern orogenic lavas: some statistics and implications

    Earth Planet. Sci. Lett.

    (1976)
  • E.D Ghent et al.

    Metamorphism at the base of the Samail ophiolite, southeastern Oman mountains

    J. Geophys. Res.

    (1981)
  • K.W Glennie et al.

    Geology of the Oman Mountains

    Verh. K. Ned. Geol. Mijnbouwkd. Genoot., Geol. Ser.

    (1974)
  • S.E Haggerty

    Oxidation of opaque mineral oxides in basalts

  • Cited by (0)

    View full text