The Ligurian Ophiolites: a journey through the building and evolution of slow spreading oceanic lithosphere

The Ligurian ophiolites constitute an accessible and unique window to track the opening and evolution of slow spreading oceanic lithosphere. The Internal Ligurian ophiolites consist of km-scale gabbroic bodies intruded into depleted mantle peridotites and bear remarkable structural and compositional similarities to oceanic lithosphere from slow and ultra-slow spreading ridges. The External Ligurian ophiolites are associated with continental crust material and include mantle sequences retaining a subcontinental lithospheric origin. This field trip explores two gabbro-peridotite associations from the Internal Ligurian ophiolites: i) the Bracco-Levanto ophiolite, which includes a km-scale gabbroic body recalling the oceanic core complexes from modern spreading centres (e.g. the Atlantis Massif, Atlantic ocean); ii) the Scogna-Rocchetta Vara ophiolite, which lacks the basalt layer similar to the nonvolcanic sections from Atlantic and Indian oceans. The peridotites and the gabbros from both these ophiolites record a composite history involving deformation and alteration from high temperature to seafloor conditions. The field excursion also explores peridotite bodies from the External Ligurian ophiolites, representing a nice example of MORB-type pyroxenite-bearing mantle.