The Triassic Nicola Group and its northern continuation the Takla Group compose most of the Quesnel oceanic island arc terrane and host the majority of the known alkalic porphyry Cu-Au deposits in British Columbia. Despite their importance as metallotect, the Triassic arc sequences have not extensively been studied in the context of regional metallogeny.
This two year project will investigate along strike variations in the physical volcanology, geochemistry and related changes in physical properties of the Nicola Group and parts of the Takla Group. The goals are to identify characteristics indicative for proximity of known porphyry ore deposits and tectonomagmatic processes that led to porphyry ore formation.
The study will concentrate on five key areas within the Geoscience BC Quest geophysical surveys and its southern continuation. These are the areas around the Mount Milligan, Mount Polley and Afton/Ajax alkalic porphyry Cu-Au deposits, as well as two reasonably exposed areas within the Nicola arc without known alkalic porphyry deposits. The latter will include the Canim Lake area and exposures 50-100 km S of Kamloops.
We will obtain major and trace element whole rock geochemical data, backed up by limited microanalysis of mineral phases and geochronology (Fossils, U/Pb) where necessary (and if possible) to clarify stratigraphic relationships. We also plan to routinely analyze the samples by portable XRF to establish its use for field based large scale geochemical vectoring to mineralization.
Physical rock properties such as magnetic susceptibility, density and electrical conductivity will also be measured and related to petrographic observations and chemical variations. The rock property data provide the critical link between the geology of the Quesnel arc and the recently acquired high-quality airborne geophysical data (QUEST project), and will enhance the application of the geophysical inversion codes to map the geology under cover and consequently will allow for an improved understanding of the geology from the geophysics.
Field based observations and standard petrographical and geochemical techniques will provide prospectivity indices; this includes fingerprinting regionally significant changes in lithogeochemistry which reflects magmatic and/or hydrothermal processes related to alkalic porphyry ore formation.