Paleomagnetic and Rock Magnetic Results From the Chenaillet Ophiolite (French/Italian Alps) and its Interpretation as a Former Oceanic Core Complex

Abstract:

The Chenaillet ophiolite lies at the Franco-Italian border in the Alps and consists of a rather well-exposed, undeformed and complete ocean-floor sequence. This sequence was formed within the Alpine Tethys oceanic domain at about 160 Ma and was subsequently obducted during Europe-Adria convergence. Well preserved pillow lavas, gabbros and serpentinized mantle rocks can be found following a stratigraphic order. It has been recently suggested, based on stratigraphic observations, that Chenaillet could be a remnant Oceanic Core Complex (Manatschal et al., 2011). In order to have a better understanding of the nature of this ophiolite, a paleomagnetic and rock magnetic study was undertaken. Results are compared with a set of data from a recent (less than 1 Ma) serpentinized ultramafic complex at the Atlantic ridge (ODP leg 153) and from various ophiolites. Our results show that the magnetic behavior of the serpentinized section from Chenaillet is rather different than in most other ophiolites but shows strong similarities with that observed for the Atlantic set. This suggests that serpentinization at Chenaillet occurs in an environment which share similarities with slow spreading ridges. In addition preliminary paleomagnetic results show that the mantle section from the Chenaillet ophiolite may have been rotated during unroofing as observed in recent Oceanic Core Complexes.