ABSTRACT
The Boléo deposit is a low-grade, large tonnage, sediment-hosted, stratiform Cu-Co-Zn deposit that developed in response to early continental rifting leading to the opening of the Gulf of California. Ore deposition is interpreted to be synsedimentary, as supported by metal zonation, stratigraphic position, sedimentary textures and structures, and K-Ar geochronology. Leaching of metals from the underlying volcanic pile, crystalline basement or a sedimentary source cannot account for the total amount of metal in the deposit. Trace element geochemistry of coeval volcanic units and oxygen stable isotope geochemistry of Mn-oxides indicate that there may be a magmatic fluid component to the ore-forming fluids.
