Schematic stratigraphic section. This class of deposit also contains significant amounts of cobalt, zinc, lead, silver, platinum group elements, gold, rhenium, and uranium.
Cobalt is of particular interest.
Andrew hopes to explain why only a limited number of these deposits are cobalt-bearing. Within the Boleo district, copper, cobalt, and zinc mineralization is hosted by the Miocene aged Boleo formation. The base of each these cycles consists of a tuffaceous claystone grading into tuffaceous siltstone and sandstone, with the top of the cycle consisting of either conglomerate or its gulfward equivalent of sandstone. The basal laminated claystone abruptly overlies a thin claystone veneer that drapes the upper bedding surface of the underlying conglomerate. It was this basal laminated claystone that was the economic target during the French and Mexican mining eras.