Hualgayoc mining district, northern Peru: Testing the use of zircon composition in exploration for porphyry-type deposits

摘要

The Hualgayoc district in the Cajamarca region, northern Peru, hosts several deposits, including the Cerro Corona Au + Cu porphyry deposit (0.55 Mt Cu, 99 t Au) and the Tantahuatay high-sulfidation epithermal Au deposit (74 t Au), plus other Au, Cu, Ag and base metal prospects. Previous studies have documented that zircon in igneous rocks associated with porphyry systems elsewhere in the world shows large positive Ce anomalies and small negative Eu anomalies, which reflect both the oxidized and hydrous nature of their parental magmas. This study presents the trace element compositions of magmatic zircon from igneous rocks associated with porphyrystyle mineralization, as well as barren stocks, sills and volcanic rocks in the district, in order to investigate the usefulness of zircon composition in exploration for porphyry-type deposits. The compositions of the zircon suggest that all parental magmas in the Hualgayoc district are oxidized, and that the magnitude of Ce and Eu anomalies is independent of the spatial and/or temporal association of igneous rocks with mineralization. Although zircon composition is not sufficient to recognize specific intrusions as fertile to generate hydrothermal ore deposits, the composition, properly applied, may be useful to target areas containing oxidized igneous rocks for further detailed exploration.