Jet Gold resembles Cu-AU porphyry system
Porphyry
Porphyry copper deposits consist principally of stockworks of quartz veinlets, quartz veins, closely spaced
fractures and breccias containing pyrite and chalcopyrite with lesser molybdenite, bornite and magnetite
(Panteleyev, 1995). Disseminated sulphide mineralization is generally present in subordinate quantities.
Mineralization is relatively evenly distributed throughout large volumes of rock, forming high tonnage,
low to moderate grade ore deposits. Porphyry deposits are temporally and genetically associated with
hydrothermal alteration of the host intrusions and country rock. Intrusions can be calcalkaline (quartz
diorite to granodiorite to quartz monzonite) or alkalic (syenites and related rocks), and widespread
propylitic alteration, with more localized phyllic, potassic and silicic alteration zones are typical of many
porphyry deposits. In calcalkaline porphyry deposits the principal commodities are copper, molybdenum
and gold (+/-silver); in alkalic porphyry deposits copper and gold (+/-silver) are commonly co-products.
Porphyry copper deposits occur 1) in orogenic belts at convergent tectonic plate boundaries, and are
commonly linked to subduction-related magmatism, and 2) in association with the emplacement of
hypabyssal stocks during extensional tectonism (Panteleyev, 1995). Porphyry copper deposits commonly
are centered around small, high-level cylindrical porphyry stocks or swarms of dykes that intrude their
coeval and cogenetic volcanic piles. Deposits can form at near surface depths of less than 1 km in
subvolcanic settings (‘Volcanic’ type), at shallow depths of 1-2 km in association with cylindrical
porphyritic intrusions (‘Classic’ type), and at relatively deep levels of 2-4 km in large plutonic to batholithic
intrusions. The geometry and dimensions of porphyry copper deposits vary greatly; undeformed deposits
range from 0.1 to 1.0 km in diameter and vertical extent (John et al, 2010). Alkalic porphyries commonly
are expressed as clusters of deposits having pipe-shaped geometries. Calcalkaline porphyries, by
comparison, commonly relate to a single intrusive event. A supergene enrichement (copper oxide) zone
sometimes overlies the hypogene ore zone. In British Columbia, porphyry deposits typically formed in the
Triassic/Jurassic (210-180 Ma) and Cretaceous/Tertiary (85-45 Ma).
A variety of mineral deposits may be genetically associated with porphyry systems, including skarns and
polymetallic veins (John et al, 2010).