The Canadian Cordillera contains numerous classic porphyry
deposits and several unusual subtypes, including the alkaline suite of porphyry
Cu-Au deposits and the
Tombstone
magmatic suite and associated AuW
deposits. The alkaline suite formed in collisional settings in island arcs
whereas the
Tombstone
suite was emplaced in an active fold
and thrust belt in a continental arc. In addition to different regional
settings, these suites differ in the type of underlying basement, metallogeny,
and the styles of mineralization. Both magmatic suites were emplaced over short
intervals, probably in response to specific tectonic events. In the case of the
alkaline suite, the tectonic event promoted magmatic processes suitable for the
formation of porphyry Cu-Au deposits. The tectonic environment is less well
constrained for the
Tombstone
suite, but the result was the
formation of distinctive porphyry and intrusion-related AuW
deposits.