Porphyry Copper Model Flashcards
What is the geotectonic setting of Philippine porphyry copper deposits according to Sillitoe & Gappe (1984)?
They are associated with island arc magmatism in a convergent margin setting, specifically related to the westward subduction of the Philippine Sea Plate beneath the Eurasian Plate.
What is the primary host rock lithology of Philippine porphyry copper deposits?
The deposits are predominantly hosted by calc-alkaline dioritic to quartz-dioritic plutons, often emplaced within andesitic volcanic arcs.
What are the structural controls that localize porphyry copper deposits in the Philippines?
Mineralization is primarily controlled by arc-parallel fault systems, pre-existing basement structures, and magmatic-hydrothermal breccia zones that act as conduits for metal-bearing fluids.
Describe the zonation of hydrothermal alteration in Philippine porphyry copper systems.
Potassic core: K-feldspar + biotite ± magnetite ± quartz; Phyllic zone: Quartz + sericite + pyrite; Argillic zone: Kaolinite + illite ± smectite; Propylitic halo: Epidote + chlorite + calcite ± pyrite.
What is the primary ore mineral assemblage in Philippine porphyry copper deposits?
The dominant ore minerals are chalcopyrite and bornite, often associated with molybdenite in stockwork veinlets and disseminated within the altered host rock.
What role do hydrothermal fluids play in the formation of porphyry copper deposits?
Metal-bearing magmatic-hydrothermal fluids, derived from oxidized arc magmas, ascend through fractures and breccia zones, precipitating sulfides upon cooling and fluid-rock interaction.
What are the key geochemical signatures of Philippine porphyry copper deposits?
They exhibit enrichment in Cu, Au, Mo, and S, with associated LREE anomalies, high Sr/Y ratios, and low Nb/Ta ratios, indicative of an oxidized, water-rich magmatic source.
What is the typical depth range for porphyry copper mineralization in the Philippines?
Ore deposition occurs at depths of 1–5 km, corresponding to the epizonal to mesozonal emplacement of dioritic to granodioritic intrusions.
What are some of the major porphyry copper deposits identified in the Philippine arc system?
Atlas (Cebu): Classic porphyry copper system with strong potassic alteration; Tampakan (South Cotabato): High-sulfidation overprint on a porphyry Cu-Au system; Far Southeast (Benguet): Deep-seated porphyry Cu-Au mineralization beneath a high-sulfidation lithocap.
What exploration techniques are commonly used to identify porphyry copper systems in the Philippines?
Geophysical surveys: Magnetics and IP resistivity to detect alteration zones; Geochemical anomalies: Cu, Mo, and Au dispersion halos in stream sediments; Drilling programs: Deep diamond drilling to delineate ore bodies and alteration zones.
