Different PT paths recorded in a tectonic mélange (Voltri Massif, NW Italy): implications for the exhumation of HP rocks

• DOI: 10.3166/ga.20.3-19
• Publication Date: 2007-03-20T15:21:56Z
• Authors: Laura Federico; Laura Crispini; Marco Scambelluri; Giovanni Capponi
• Keywords: Blueschist; Greenschist; Massif; Lawsonite

Abstract The Cascine Parasi Mélange (CPM) of the high-pressure, meta-ophiolitic Voltri Massif (Ligurian Western Alps), consists a foliated chlorite-actinolite greenschist matrix enclosing lenses metabasites and metasediments. surrounding units consist serpentinites not these metamorphic rocks. records three sets folds: (i) Dm1/Dm2 (blueschist to greenschist-facies conditions), which can be correlated folds in metasedimentary blocks; (ii) Dm3, are most obvious field partially re-orient previous structures. metabasite preserve internal High-Pressure (HP) schistosities unrelated foliation. equilibrated at different peak conditions (ranging from eclogite- blueschist-facies) some recorded prograde transition lawsonite-bearing assemblages garnet blueschists. Individual display segments typical subduction PT paths apparently converge blueschist facies. A late stage re-equilibration is particularly widespread rims HP lenses. These structural features suggest that mélange was active during early phases evolution area, least through exhumation emplacement blocks into shallower crustal levels transitional blueschist- greenschist-facies; older history only preserved inside blocks. Keywords: tectonic mélangehigh-pressure metamorphismLigurian Alpsexhumation