Contexte lithostructural, âges 40K40Ar et géochimie du volcanisme calco-alcalin tertiaire de Cap-d'Ail dans le tunnel ferroviaire de Monaco

Abstract

Le contexte lithostratigraphique et structural, la chronologie et la géochimie du volcanisme andésitique tertiaire de Capd'Ail (Alpes-Maritimes, France) sont précisés grâce aux nouvelles données acquises pendant les travaux de mise en souterrain du réseau ferré entre Cap-d'Ail et Monaco. Deux événements magmatiques distincts sont mis en évidence sur le site, l'un paléogène, l'autre néogène.

Beginning of the Apennine subduction system in central western Mediterranean: Constraints from Cenozoic “orogenic” magmatic activity of Sardinia, Italy

“…As concerns the possibility to distinguish between the hypotheses of lateral expulsion of crustal wedges or the classical back‐arc formation above a west directed, east retreating subduction system, igneous petrology cannot provide any unequivocal constraint. However, the emplacement of coeval igneous rocks with roughly similar geochemical subduction‐related characteristics in Sardinia [e.g., Beccaluva et al , 1989; Lustrino et al , 2004], offshore Corsica [e.g., Rossi et al , 1998], along the Provençal [e.g., Ivaldi et al , 2003; Beccaluva et al , 2005] and Catalonian margins [ Martì et al , 1992], as well as the spatial NE–SW distribution of the Oligo‐Miocene magmatic activity (i.e., in a predrift position) is more consistent with a petrogenetic process involving partial melting of a mantle wedge above a NW directed subducting oceanic lithosphere and a concomitant SE retreat of the subduction hinge. Worth to note is that all the geological, sedimentological, structural and geophysical evidences converge to the common hypothesis that the Ligurian‐Provençal Basin must be considered a back‐arc basin [e.g., Beccaluva et al , 1989; Faccenna et al , 1997; Carminati et al , 1998; Doglioni et al , 1999; Lustrino , 2000b; Finetti et al , 2001; Rosenbaum and Lister , 2004; Schettino and Turco , 2006].…”

Structure and evolution of a passive margin in a compressive environment: Example of the south-western Alps–Ligurian basin junction during the Cenozoic

“…The reworking of the lower-Miocene deposits in the Cap d'Ail thrusts, between Beaulieu and Monaco (Fig. 3), indicates that the deformation did not reach the shoreline before the middle Miocene (Ivaldi et al, 2003). Near the coast, large olistoliths of Jurassic carbonates found within the BurdigalianeLanghian conglomerates of the Roquebrune Cap Martin basin (Fig.…”

“…Onshore, the base of the Nice and Castellane thrust sheets is always marked by unconformities related to differential erosion during their tectonic emplacement, even where the thrusts are guided by the Triassic level of evaporites that underlines the Mesozoic terranes (e.g. Ivaldi et al, 2003;Laurent et al, 2000;Rouire et al, 1980). Moreover, the Triassic evaporites always correspond to highly deformed and heterogeneous plastic levels (Gèze, 1963;Malavieille and Ritz, 1989;Ritz, 1986;Rouire et al, 1980), suggesting a variable nature and thickness of the Trias along the basal decollement (Laurent et al, 2000).…”

Oppositely directed pairs of propagating rifts in back‐arc basins: Double saloon door seafloor spreading during subduction rollback

“…Map of the Valencia Trough (VT), Gulf of Lion (GL), and the Liguro‐Provencal Basin (LPB) [after Bellon , 1981; Rehault et al , 1984; Beccaluva et al , 1989; Marti et al , 1992; Saula et al , 1994; Maerten and Séranne , 1995; Mauffret et al , 1995; Rossi et al , 1998; Goula et al , 1999; Maillard and Mauffret , 1999; Roca et al , 1999; Séranne , 1999; Roca , 2002; Rollet et al , 2002; Savelli , 2002; Ivaldi et al , 2003; Maillard et al , 2003; Nehlig et al , 2003]. Numbers refer to radiometric ages of volcanics.…”

“…As yet, no deep drilling has determined the age or character of deeply buried transitional and oceanic domains of the Liguro‐Provencal Basin. However, on the Ligurian Margin, erupted volcanic rocks [ Ivaldi et al , 2003] generally young to the northeast toward Genoa, with 33–26 Ma calc‐alkaline volcanics on the northeast flank of the Maures‐Esterel Massif and Villeneuve‐Loubet, 27 and 19 Ma volcanics farther northeast at Cap d'Ail, and finally 12–11 Ma alkali basalts at Monte Doria in the center of the Cape Mele–Cape Corse Fracture Zone (Figure 6).…”