Fabrizzio Abello, MSc

The late Triassic - early Jurassic Iron Mask Batholith (IMB) in southern British Columbia hosts several alkalic porphyry Cu-Au mineralized centers such as New Afton, Ajax, Copper King, and Python. This research identifies mineral and chemical footprints of the alkalic porphyry deposits in the IMB through fieldwork, petrography, geochronology, and geochemistry. Results were compared with the footprint of the nearby Nora and other BC calc-alkalic deposits.   

Pathfinder elements in the studied alkalic porphyry deposits extend horizontally from a central core of Pd, Pt, Cu, and Au (~100m x 800m) to Te, Re, and Se (~700m x 1.5km) and further distal V, As, and Sb (>~1 km x >1.5km). Vertically, at New Afton, a higher concentration of Mo occurs at depth (~750m deep) along with depleted Zn and Mg. This is overlain by a zone of high concentrations of Cu, Au, Pd, and Pt. Near surface Te, V, As, and Sb have higher concentrations. K-feldspar-rich veins occur proximal to the mineralization, surrounded by calc-potassic (k-feldspar + epidote ± sulfides ± magnetite) and more distal calcic veins (epidote ± carbonates).

Results indicate that hydrothermal alteration in alkalic porphyry deposits is more cryptic than calc-alkalic deposits. Porphyry emplacement and alteration is typically asymmetric and structurally controlled. Similarly, anomalous values of pathfinder elements are typically less pronounced than those in the calc-alkalic porphyry deposits except locally for Te, Pd, As, Ag, and V, which have higher concentrations and display concentric zoning. These results help to identify the signature of the alkalic porphyry mineralization early during exploration and vector toward potential mineralization.