Geology, geochemistry and tectonic setting of Pan-African serpentinites of Um Salim-Um Salatit area, Central Eastern Desert, Egypt

This research aims at integrating remote sensing data and field studies for lithological mapping of different rock units. Geological interpretation of Landsat ETM+ image and field studies revealed that the study area is mainly covered by ophiolitic ultramafic rocks, ophiolitic metgabbros, schistose metavolocanics and alkaline granites.The serpentinites masses occur in the form of dipping or steeply inclined sheets or lenses generally emplaced along thrust faults .They are elongated in a ENE-WSW direction. They are composed essentially of antigorite, clinochrysotile and lizardite with subordinate amount of magnesite, chromite, magnetite, talc and chlorite.Geochemically, the studied serpentinites are rich in MgO, Cr, Ni and high Ni/Co ratio. The examined serpentinites belong to the ultramafic cumulate ophiolite rocks and it was originally a harzburgite that represents a fragment of the oceanic lithosphere formed in a back arc basin, i.e., they belong to an ophiolitic mantle sequence which was formed above subduction zone (SSZ).Several mineral deposits are associated with the ophiolitic ultramafic rocks such as magnesite, talc and chromite. Chromite lenses are mainly encountered at wadi level in a podiform shape. Microprobe analyses of chromite show that the chromite is an aluminum chromite type. The podiform chromite is characterized by low TiO2 (<0.3%) and MnO (<0.27% contents) which are considered as distinct feature of Alpine type chromite deposits. The presence of podiform chromites in the serpentinites are related typically to supra subduction zone ophiolites (SSZ). The studied serpentinites show similarities to the Alpine type serpentinites.