Platinum-group minerals from the Santiago River, Esmeraldas Province, Ecuador

Resumen

ABSTRAC| The first platinum-group minerals (PGM) to be described in detail from Ecuador come from placers in the Santiago River' Esmeraldas hovince. This area is situated between the Cordillera de Toisdn and the Pacific coast in the northwestem part ofthe country. The only PGM found as individual mineral grains in the placen are h-Fe alloys, mainly native platinum with minor isofenoplatinum. Minerals found as inclusions in ft-Fe alloys are hongshiite, osmium, bowieite, cuprorhodsitg. laurite' erlichmanite, cooperite, braggite, unknown phases in the systems Pd-As-Te, Pd{u-S and Pt{u-S, and chalcopyrite. The PGM in the placen arejnfened to derive from a mafic-ultramafic Alaskan-type intrusion that has yet to be identified.