Porphyry copper (PCu) deposits represent the largest and most important sources of copper, representing almost 75% of the world's supply. In addition, PCu deposits also contribute 50% of the world's supply of molybdenum, and about 20% of the world's Au.
Aguila is exploring the Lida and Cora porphyry copper projects in the Western United States.
Province and District Scale
Porphyry copper deposits normally form at convergent plate boundaries within magmatic arc (including backarc) environments. They are predominantly associated with Mesozoic to Cenozoic orogenic belts in western North and South America, around the western margin of the Pacific Basin, and in the Tethyan orogenic belt in eastern Europe and southern Asia. Regionally, they have a tendency to occur in linear, orogen-parallel belts, which range from a few tens to sometimes thousands of kilometers long, and have a strong structural component to their formation. These belts commonly occur as clusters or alignments that may between 5 to 30 km across.
Lee and Tang (2020).
Park et al. (2021).
The deposits are closely related to underlying composite plutons at paleodepths of 5 to 15 km. These plutons represent the supply chambers for the magmas and fluids that form the vertical, elongate stocks or dike swarms that are felsic to intermediate in nature, and associated mineralization. High and low sulfidation epithermal deposits, skarn deposits, and sediment hosted systems are commonly associated with porphyries and magmatic-hydrothermal fluids.
Mineralization is usually represented as large, and low-to medium-grade orebodies. Economic grades typically range from about 0.3 to 1.5% Cu, however, within the deposit grades can vary, especially if a PCu has both a hypogene sulfide zone (i.e, chalcopyrite-rich), and a supergene enrichment blanket.
Mineral exploration strategies
Exploration methods for PCu deposits encompass several facets. Key characteristic alteration mineral zonations, passing centrally from the bottom upward, include sodic-calcic, potassic, chlorite-sericite, sericitic, and advanced argillic. Chloritic and propylitic alteration develop distally at shallow and deeper levels, respectively. Pathfinder element geochemistry including Cu, Mo, Re, Au, Zn, Pb, As, and Sb are particularly useful at identifying prospective locations at district/regional scale surficial exploration. Additionally, whole rock and mineral geochemistry can be used to assess porphyry magma fertility.
Geophysical and remote sensing strategies commonly include induced polarization (IP), magnetic surveys, gamma, and hyperspectral and a widely established as effective targeting tools.