Mineralización de elementos del grupo del platino (EGP) en las cromititas de los macizos ultramáficos del Complejo de Cabo Ortegal

Abstract

Many different platinum-group minerals (PCM) have been observed in the chromitites of the Cabo Ortegal complex, one of five Paleozoic ultramafic bodies that crop out in the NW of the Iberian Peninsula. Chomitites are inhomogeneously distributed within the >1100 m-thick serpentinized ultramafic sequence, and can contain up to 13 ppm of total platinum-group elements. Six PCM assemblages are described in these samples including Pt-Pd-sulphides, Pt-Rh alloys, As-, Bi-, Sb- and Te-bearing PGM, PCM enclosed in chromite grains, Hg-, Pb- and Au-bearing PCM and Pt-Pd-bearing oxides. Whereas the PCM enclosed in chromite rims, mostly laurites, are interpreted as being of primary origin, most of the PCM occurring on chromite rims, or distributed within the serpentinized silicates, have complex alteration textures indicating a secondary origin.