Interplay between melt infiltration and deformation in the deep lithospheric mantle (External Liguride ophiolite, North Italy)

Abstract Mantle peridotites from the External Liguride Jurassic ophiolites (Northern Apennines, Italy) show diffuse occurrence of pyroxenite bands, recording melt migration and crystallization at lithosphere-asthenosphere boundary, during old, pre-Jurassic stages their subcontinental lithospheric mantle evolution. We present coupled microstructural geochemical study profiles across various types pyroxenite-peridotite layering in these ophiolites, aiming to constrain relative timing potential interplay between infiltration deformation. The sequence is composed lherzolite harzburgite, occasionally interleaved with dunite, crosscut by centimeter- decimeter-wide layers. have a porphyroclastic texture penetrative tectonic foliation subparallel layering. Peridotite-pyroxenite contacts are irregular grain scale. Olivine pyroxenes both pyroxenites record moderate strong crystallographic preferred orientations (CPO) alignment olivine [100] [001] axes stretching lineation marked elongation. This compatible coeval deformation high-temperature, spinel lherzolite-facies event. major trace element compositions metasomatic imprint that decreases distance layers, whereas strength CPO country towards parallelism layers peridotite foliation, contacts, as well spatial correlation changes, consistent syn- late-kinematic emplacement pyroxenites. These observations point transport processes mantle, characterized focusing conduits parallel changes due presence melts. Exhumation this section resulted partial replacement spinel-facies assemblage plagioclase-bearing assemblage. Topotaxial relationship plagioclase precursor minerals suggests exhumation was not associated pervasive peridotite, but rather accommodated localized discrete shear zones, sampled study.