La marge européenne de la Téthys jurassique en Corse : datation de trondhjémites de Balagne et indices de croûte continentale sous le domaine Balano-Ligure

Abstract

The European margin of the Jurassic Tethys in Corsica: dating of Balagne trondhjemites and evidence to support a continental crust beneath the Balagne-Ligurian domain. Vein trondhjemite in gabbro of the Carnispola Bridge has been dated to 169 ± 3 Ma (U-Pb on zircon). This date indicates that E-MORB-type ophiolites were emplaced in the marginal Balagne part of the Ligurian Jurassic basin about some 10 Ma before the emplacement of N-MORB ophiolites in the most central part of the ocean. In addition, the presence of inherited zircons with Ordovician (431 ± 8 Ma) and Archean (2693 ± 12 Ma) ages reveals that the Balagne ophiolites were emplaced on a thinned continental crust. Finally, the 298 ± 4 Ma age of zircons from eclogitised meta-arkose in the eclogitic Morteda-Farinole unit ('Schistes lustrés' zone) confirms the attribution of these rocks to a palaeogeographic area that laid between continent and ocean, along the edge of the Hercynian granite batholith in Corsica. To cite this article: P. Rossi et al., C. R. Geoscience 334 (2002) 313-322.  2002 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS ophiolites / Jurassic / U-Pb dating / CorsicaRésumé -La datation (par la méthode U-Pb sur zircons) à 169 ± 3 Ma de trondhjémites en veines dans les gabbros du pont de Carnispola indique que la mise en place des ophiolites de type E-MORB dans la partie marginale, en Balagne, du Bassin jurassique ligure est intervenue une dizaine de millions d'années avant la mise en place des ophiolites N-MORB de la partie la plus centrale de l'océan. La présence de zircons hérités ordoviciens (431 ± 8 Ma) et archéens (2693 ± 12 Ma) révèle, en outre, que l'installation des ophiolites s'est déroulée, au moins pour partie, sur une croûte continentale amincie. Par ailleurs, dans l'unité éclogitique de Morteda-Farinole (zone des Schistes lustrés), la datation à 298 ± 4 Ma de zircons de méta-arkoses éclogitisées conforte l'attribution de ces dernières à une zone paléogéographique intermédiaire entre continent et océan, en bordure du batholite granitique hercynien corse.

New isotopic constraints on age and magma genesis of an embryonic oceanic crust: The Chenaillet Ophiolite in the Western Alps

“…Sm-Nd isochron and Ar/Ar or K-Ar age data are not included, because they are either imprecise or susceptible to Alpine overprinting, and do therefore not necessarily date the age of accretion of a given piece of ophiolite. Rossi et al (2002), Rubatto and Scambelluri (2003), Rubatto et al (1998), Rubatto et al (2008), Schaltegger et al (2002), Stucki et al (2003); this study.…”

“…The U-Pb zircon dates for the plagiogranites are highly variable ranging from 142 to 169 Ma (Borsi et al, 1996, Costa and Caby, 2001, Ohnenstetter et al, 1981, Rossi et al, 2002, Rubatto and Scambelluri, 2003, Rubatto et al, 2008, Schaltegger et al, 2002and Stucki et al, 2003. While the plagiogranites from the Platta, Lanzo and Chenaillet Ophiolites are dated at 161-165 Ma, coeval with the co-exiting MOR gabbros (Rubatto et al, 2008 andSchaltegger et al, 2002; this study), others are either poorly dated or differ in age significantly from the co-existing gabbros.…”

Dike magmatism in the Sila Grande (Calabria, southern Italy): Evidence of Pennsylvanian–Early Permian exhumation

“…A close match of the ages in the various regions cannot be established owing to the different dating methods adopted (Ferrés, 1998;Carmignani et al, 1999;Ronca et al, 1999;Atzori et al, 2000;Rossi et al, 2002;Cocherie et al, 2005). Notwithstanding this problem, it can be deduced that most of this magmatic activity affected the southern Hercynian domain between 295 and 270 Ma (Fig.…”

“…Dike swarms postdate most of the plutonic complexes, and are mainly related to calc-alkaline and alkaline magmatic affi nity, and more rarely to tholeiitic series (Orejana et al, 2008, and references therein). In the central and western Mediterranean, dike swarms, mainly of Early Permian age, are well developed in different sectors of the southern Hercynian belt of Europe, such as the Catalan Coastal Range (Enrique, 1984(Enrique, , 1990Ferrés, 1998), Corse (Rossi et al, 1993(Rossi et al, , 2002Carmignani et al, 1999;Traversa et al, 2003;Cocherie et al, 2005), and Sardinia (Carmignani et al, 1999;Ronca et al, 1999;Atzori et al, 2000;Traversa et al, 2003) (Fig. 1).…”

The architecture of an incipient oceanic basin: a tentative reconstruction of the Jurassic Liguria-Piemonte basin along the Northern Apennines–Alpine Corsica transect

“…This breccia is characterized by fragments of olivine-gabbro, Fe-gabbro, plagiogranite and basalt. U-Pb (SHRIMP) dating of zircons indicated an age of 169 ± 3 Ma for the plagiogranites (Rossi et al 2002). In addition, the arenitic matrix of the breccia includes detrital mineral grains of zircon, whose typology indicates an origin from calco-alkaline rocks, similar to those cropping out in the Variscan basement of Corsica.…”