The ophiolite-bearing Schistes lustrés nappe in Alpine Corsica: A model for the emplacement of ophiolites that have suffered HP/LT metamorphism

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Abstract
The Adria microplate has been thrust westward onto the Corsican microplate by a distance of at least 150 km. This crustal duplication followed the Late Cretaceous easterly directed subduction of the eastern Corsican continental margin after consumption of intervening Tethyan oceanic crust. The suture zone separating the two micro-plates is delineated by the ophiolite-bearing Schistes lustrés nappe, which suffered a Late Cretaceous HP-LT metamorphism. The Corsican blueschists crystallised during a major thrusting event at depths probably in excess of 35 km, and were overprinted by post-tectonic greenschist facies assemblages at 15-20 km during Late Eocene times. Eventual uplift and exposure of the Schistes lustrés and ophiolites were probably the result of isostatic compensation and erosion during and following their emplacement onto continental basement. It is proposed that the major thrusting event occurred within a subducted oceanic portion of the Corsican microplate, in the footwall of a leading, overriding oceanic portion of the Adria microplate. Thrusts probably propagated in a dominantly piggyback sequence within the subducted oceanic slab, first involving the most deeply buried rocks, then progressively the less deeply buried rocks. This is evident from the fact that the ophiolites and Schistes lustrés that preserve the highest metamorphic "grade" are the most easterly, and structurally highest. The model deduced for emplacement of the Corsican ophiolite nappe may be applicable to the Schistes lustrés nappe that forms a major tectonic unit in the internal zones of the western Alps, and to the metamorphic ophiolite-bearing nappes in western Liguria.

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