HAL : insu-00559080, version 1

DOI : 10.1016/j.lithos.2010.12.006

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Lithos 122, 1-2 (2011) pp.122-136

Triassic alkaline magmatism of the Hawasina Nappes: Post-breakup melting of the Oman lithospheric mantle modified by the Permian Neotethyan Plume

François Chauvet 1, 2, Henriette Lapierre 2, René C. Maury 3, Delphine Bosch 4, Christophe Basile 2, Joseph Cotten 3, Pierre Brunet 5, Sylvain Campillo 2

(02/2011)

Middle to Late Triassic lavas were sampled within three tectonostratigraphic groups of the Hawasina Nappes in the Oman Mountains. They are predominantly alkali basalts and trachybasalts, associated with minor sub-alkaline basalts, trachyandesites, trachytes and rhyolites. Their major, trace elements and Nd-Pb isotopic compositions are very similar to those of the Permian plume-related high-Ti basalts which also occur in the Hawasina Nappes. The Triassic lavas derive from low-degree melting of an enriched OIB-type mantle source, characterized by εNdi = 0.3-5.3 and (206Pb/204Pb)i = 16.96-19.31 (for t = 230 My). With time, melting depths decreased from the garnet + spinel to the spinel lherzolite facies and the degree of melting increased. The oldest are distinguished from the others by unradiogenic Nd and Pb signatures, with εNdi = − 4.5 to − 1.2 and (206Pb/204Pb)i = 16.35-17.08, which we attribute to their contamination by Arabo-Nubian lower crust. The lavas likely derived from the Oman lithospheric mantle, the original DMM-HIMU signature of which was overprinted during its pervasive metasomatism by the Permian plume-related melts. We suggest that these lavas were emplaced during post-breakup decompression-triggered melting in the Middle Triassic during global kinematic reorganization of the Tethyan realm.

1 :	Laboratoire de Planétologie et Géodynamique de Nantes (LPGN)
	CNRS : UMR6112 – INSU – Université de Nantes
2 :	Institut des sciences de la Terre (ISTerre)
	CNRS : UMR5275 – IFSTTAR – Université de Savoie – Université Joseph Fourier - Grenoble I – INSU – OSUG – Institut de recherche pour le développement [IRD] : UR219
3 :	Domaines Océaniques
	Institut Universitaire Européen de la Mer (IUEM) – Université de Bretagne Occidentale [UBO] – Observatoire des Sciences de l'Univers – CNRS : UMR6538
4 :	Géosciences Montpellier (GM)
	CNRS : UMR5243 – Université Montpellier II - Sciences et techniques
5 :	Laboratoire des Mécanismes et Transfert en Géologie (LMTG)
	CNRS : UMR5563 – Observatoire Midi-Pyrénées – Université Paul Sabatier [UPS] - Toulouse III – Institut de recherche pour le développement [IRD] : UMR154

Équipe de recherche : Tectonique reliefs et bassins

domaine

:

Planète et Univers/Sciences de la Terre/Géochimie Sciences de l'environnement/Milieux et Changements globaux Planète et Univers/Sciences de la Terre/Pétrographie

mots-clés : Neotethys – Passive margin – Post-breakup magmatism – Triassic – Hawasina – Oman Mountains

insu-00559080, version 1

http://hal-insu.archives-ouvertes.fr/insu-00559080

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Contributeur : Dominique Gac <>

Soumis le : Vendredi 18 Mars 2011, 15:52:51

Dernière modification le : Lundi 26 Mars 2012, 13:16:20