A MICROSTRUCTURAL ANALYSIS OF THE UPPERMOST UNIT OF CRETE, GREECE

The island of Crete, Greece, is composed of thrust nappes accreted from the actively subducting African Plate. The Uppermost nappe is the structurally highest unit in the Cretan tectonostratigraphy and represents oceanic lithosphere from the middle Jurassic Vardar Ocean. This lithologically heterogeneous ophiolitic sequence includes peridotites which exhibit varying degrees of serpentinization, along with many other rocks of oceanic origin that underwent low grade metamorphism in the upper Jurassic. We collected a suite of samples from the Uppermost Unit in central Crete for petrological and microstructural analysis. Most samples show evidence for pervasive serpentinization, with widespread alteration to lizardite (displaying both mesh and bastite texture). In some samples, relict olivine, clino-, and orthopyroxene are preserved. To better characterize the deformation conditions within the ophiolite, we measured the olivine crystallographic fabric in one minimally-altered peridotite by electron backscatter diffraction. Preliminary results suggest that the sample has a B-type olivine fabric, characterized by a point maxima of [001] subparallel to mesoscopic lineation (X) and [010] aligned subparallel to the pole to foliation (Z). The [100] axes define a weak girdle perpendicular to the lineation but with a concentration parallel to the Y direction of the pole figure. Olivine B-type fabric is found in other ophiolites and indicates deformation under low temperature, high stress, and/or high strain rate conditions. This interpretation supports previous studies that envision emplacement of the Uppermost Unit in the upper crust while the deeper structural units were progressively accreted at depth.