Precious metals in the Mid-Atlantic ridge fundamental rocks (15 degrees-20' fracture zone)

Investigation results of the main rock types (ultrabasites, gabbro, dolerit es and basalts) are presented. Samples were taken from the oceanic lithosph ere of the Mid Atlantic Ridge (MAR) from the 15 degrees 20'. Fracture Zone Gold and PGE contents of the "platinum" association increase upward on the crossection from ultrabasites to basalts with simultaneous decrease in PGE of the "iridium" group. Lateral tendencies of precious metal differentiatio n are expressed in an increase of their total contents from north to south. The total accumulation of PGE of the "iridium" association occurs parallel with an increase in water content and fluid oxidation degree, when transit ing from normal magmatic systems (NMORB, north intersection) to anomalous s ystems enriched by fluids (EMORB, south intersection). In mantle ultrabasit es the increase of water content and secondary serpentinization processes l ead to the increase in PGE contents of the "iridium" association.