MINERALIZATION, INTRUSIONS AND FACIES CONTROLLED BY BASEMENT TECTONIC HEREDITY, SOUTHEASTERN BRITISH COLUMBIA

Intermittently active old structures in the crystalline basement underlying the southeastern Canadian Cordillera have exerted an important influence on the subsequent sedimentary, intrusive, deformation and mineralization history. The most important structures formed during Paleoproterozoic and Archean growth and assembly of the underlying crystalline basement and are oriented transverse to the Cordilleran structural trend. Other structures, oriented subparallel to the Cordilleran structural trend, formed during Mesoproterozoic, Neoproterozoic or Cambrian rifting events. Much mineralization in the lower Purcell including the Sullivan Mine formed in areas where both transverse and basin parallel structures were active. The importance of the transverse Vulcan Low basement domain in localizing mineralization, intrusions and major thickness and facies changes in the southern Purcell Basin and Kootenay Arc has been recognized for some time. New work suggests a more northern transverse basement structural zone at the north end of the Archean Hearne Province had a similar effect. In this area, Pb-Zn showings, the southeast end of the Cambrian and Ordovician carbonate platform (Kickinghorse Rim), a cluster of Late Ordovician - Early Devonian diatreme breccia pipes, and a series of anomalous northeast-trending faults form a northeast-trending zone extending across the Rocky Mountains. These features palinspastically restore to original positions directly above a major crustal boundary in the North American craton and its along strike projection. Intermittent activity along this basement structure localized facies changes, intrusions, mineralization and subsequent structural trends in the Rocky Mountains, facies changes in the northern Purcell Basin, and normal faults under Kootenay Lake. Activity along this basement structure likely influenced intrusions and structurally controlled veins/mineralization above its westward extension in the Purcell Mountains and Kootenay Arc. It should form a prospective target for mineral exploration, particularly near the intersection with basin parallel structures.