Offshore Oligo-Miocene volcanic fields within the Corsica-Liguria Basin: Magmatic diversity and slab evolution in the western Mediterranean Sea

► Presentation of an original collection of submarine rocks sampled by dredgings and in situ divings during 25 years within the Liguria-Corsica Basin. ► Geochemical diversity of lavas and K–Ar dating of whole rocks and 39Ar–40Ar of plagioclases and amphiboles between 30 and 6Ma in several stages. ►...

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Published in:Journal of geodynamics 2012-07, Vol.58, p.73-95
Main Authors: Réhault, J.-P., Honthaas, C., Guennoc, P., Bellon, H., Ruffet, G., Cotten, J., Sosson, M., Maury, R.C.
Format: Article
Language:English
Subjects:
Adakites
Alkali basalts
Earth Sciences
Environmental Sciences
Geochemistry
Global Changes
Ligurian margins and Basin
Mediterranean
Miocene (K–Ar and 40Ar–39Ar ages)
Normal and K-rich calc-alkaline lavas
Offshore Corsica
Sciences of the Universe
Shoshonites
Slab breakoff
Slab tearing
Slab window
Subduction
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Summary:► Presentation of an original collection of submarine rocks sampled by dredgings and in situ divings during 25 years within the Liguria-Corsica Basin. ► Geochemical diversity of lavas and K–Ar dating of whole rocks and 39Ar–40Ar of plagioclases and amphiboles between 30 and 6Ma in several stages. ► West of Corsica, discovery of adakitic emissions K–Ar dated around 16Ma. ► Transition from calc-alkaline, K-rich calc-alkaline and shoshonitic lavas to alkaline basalts in north Liguria Basin and in Toulonnais. ► Constraints on the kinematic and geodynamic evolution of the northwestern Mediterranean Sea (Liguria-Corsica Basin). The European and Corsica–Sardinia margins of the Ligurian Sea (western Mediterranean) have been affected by a geochemically diverse igneous activity, offshore and onshore, since the Eocene. This magmatism occurred in a global subduction-related framework. On the European side, the oldest Tertiary magmatism dated at ca. 35Ma was mainly calc-alkaline. It included the emplacement of plutonic bodies of adakitic affinity, such as the quartz microdiorite laccolith locally referred to as “esterellite”. Younger magmatic events on-land within the whole Ligurian domain were mostly medium-K or K-rich calc-alkaline. Miocene volcanic activity was important in Sardinia, where andesites and ignimbrites were erupted during several magmatic cycles. In Corsica, it was minor although it emplaced lamprophyres near Sisco at 15Ma. Dredging and diving cruises conducted in the Ligurian Sea during the last thirty years allowed us to collect a number of submarine samples. We discuss here their geochemistry (major and trace elements) and their whole-rock K–Ar ages and mineral 40Ar–39Ar plateau ages. Around 15Ma, minor amounts of adakitic lavas were emplaced off southwestern Corsica, in the deepest part of the Liguria-Corsica Basin. They rested over the thinnest southwestern Corsica Hercynian continental crust. Closer to the coast, contemporaneous calc-alkaline rocks erupted on a less thinned crust. The adakitic events could be indicative of either the final stages of active subduction, or alternatively of a slab tearing linked to the southeastern retreat and steepening of the slab. The latter event could be connected with the end of the Corsica–Sardinia block drifting and its correlative eastern collision. Younger volcanic effusions, dated at 14–6Ma, occurred mostly northwest and north of Corsica. K-rich calc-alkaline basalts, shoshonites and K-rich trachytes were
ISSN:0264-3707
DOI:10.1016/j.jog.2012.02.003