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La marge continentale sud-téthysienne en Oman : structure et volcanisme au Permien et au Trias

Abstract : Formation of the Oman Mountains is linked to the tectonic inversion of the Arabian continental margin which bounded the southern part of the Neotethys Ocean, between the end of Palaeozoic and the Upper Cretaceous. The under-ophiolitic units of the Oman Mountains are studied in the aim to characterize the different formation stages of this part of the Neotethyan margin. Study is focalised on the Permian and Triassic volcanic activities which have accompanied the formation of the Arabian margin and among remnants are found along the southern Tethyan realm (Himalaya, Oman, East Mediterranean).
A syn-rift reconstitution of the Oman continental platform is proposed during the Middle Permian, on the base of new structural and stratigraphic observations which were conducted in the Saih Hatat and Jabal Akhdar areas. Structural analyses particularly rest on Permian synsedimentary extensional structures, and on the regional scale comparison of the facies and thickness lateral variations (Saiq Formation in Jabal Akhdar and Saih Hatat). Extensional structures indicate stretching directions mainly oriented ENE-WSW. A NS stretching component is locally observed and associated to weak amplitude motions. Unfolding of the deformed series of the platform indicates that these stretching directions correspond to the principal directions of the thickness and facies variations of the Permian sedimentary series. This suggests they represent the inverted remnants of major structures which have controlled the Arabian platform. The observed structures are contemporaneous of the Murgabian within plate volcanic activity, and correspond to a short tectonic episode (< 5 Ma).
The Middle to Upper Triassic magmatic event in Oman produces low volume of lavas, on various compartments of the Arabian margin. It is contemporaneous of a remobilisation of the margin, associated to local uplift, and to gravitary sliding of the sedimentary cover. Geochemical analyses show the volcanism is of within plate type, and suggest it has probably underwent crustal contamination. Isotopic compositions (Nd, Pb) of the Triassic Lavas are comparable to Permian alkaline lavas, suggesting a remobilisation of an inherited mantle (mainly of the Permian episode) more than the intervention of a new mantle plume.
Finally, we propose a polyphased model for the formation and evolution of the continental Oman margin. Initial formation corresponding to a volcanic margin associated to the Permian mantle plume, centred on the Panjal Traps. Orientations of the observed structures indicate this segment of the margin could be localised in the northern extremity of the India-Madagascar/Arabia-Africa rift system. The remobilisation and Triassic volcanism could be generated by a cinematic reorganization of the Tethyan realm, during the beginning of the Cimmerian blocs (Iran) collision against Laurasia.
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https://tel.archives-ouvertes.fr/tel-00202524
Contributor : François Chauvet <>
Submitted on : Monday, January 7, 2008 - 12:08:35 PM
Last modification on : Thursday, November 19, 2020 - 3:54:26 PM
Long-term archiving on: : Friday, November 25, 2016 - 8:46:33 PM

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  • HAL Id : tel-00202524, version 1

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François Chauvet. La marge continentale sud-téthysienne en Oman : structure et volcanisme au Permien et au Trias. Géologie appliquée. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00202524⟩

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