Introduction
Ophiolites of southern Apennines are obducted remains of a Late Cretaceous-Oligocene accretionary wedge (Knott, 1987; Monaco, 1993; Knott, 1994; Mazzoli, 1998; Cello and Mazzoli, 1999), resulting from a northwestward subduction of the Jurassic western Tethys below the European continental margin (Dewey et al., 1989; Bortolotti and Principi, 2005). Fragments of the former European crust are now exposed in the Calabria Terrane (Fig. 1), representing the southernmost segment of the Apennine arc (Ogniben, 1969; Knott, 1987; Bonardi et al., 2001).
In this paper we have studied metadolerite dikes from the ophiolites of the southern Apennines in order to unravel their evolution from the emplacement in the Tethyan ocean and related ocean-floor metamorphism, to the HP/LT subduction-related metamorphism acquired during the growth of the Apennine accretionary wedge. A general overview of these metadolerites is given in Sansone (2010), Sansone et al. (2011) and Sansone and Rizzo (2012). These Authors suggest that the metadolerite dikes display both amphibolite and greenschists facies mineral assemblages, related to ocean-floor metamorphism, and lawsonite-glaucophane facies assemblages, typical of subduction-related metamorphism. However, textural relationships between minerals related to primary crystallization and to the subsequent metamorphic events have never been described in detail.
We have focused our study on undeformed microstructural sites where the orogenic evolution did not obliterate the original igneous structure and the oceanic mineral assemblages, leaving intact an almost complete record of their long-lasting evolution. For this purpose, we have analysed the microstructure and mineral chemistry of metadolerite dikes, with particular emphasis on the pseudomorphic and coronitic textures indicative of different metamorphic events. Detailed petrographical and microstructural data are provided to unravel the evolution from the ocean-floor metamorphism to the HP/LT orogenic overprint. Microstructural and mineral chemistry analyses, implemented with element compositional maps, have facilitated the identification of the primary (igneous) mineral assemblages related to the magmatic protolith, and of the metamorphic minerals crystallized during the subsequent metamorphic events.