Targeted Geoscience Initiative 5, Gold Project: a summary of contributions to the understanding of Canadian gold systems
Authors: Mercier-Langevin P , Lawley C J M , Castonguay S , Dubé B , Bleeker W , Pinet N , Bécu V , Pilote J -L , Jackson S E , Wodicka N , Honsberger I W , Davis W
J , Petts D C , Yang Z , Jautzy J , Lauzière K 
Published: June 2020

The discovery of new mineral deposits is essential to maintain a stable supply of mineral commodities, however, new mineral discoveries are in ever more remote, deeper, and/or covered geological environments, which presents significant challenges. The fifth phase
of the Targeted Geoscience Initiative (TGI-5) was developed to address these challenges and to advance our understanding of ore-forming processes at various spatial scales and across geological time. Here we present a selection of highlights from research activities comprising the Gold Project.
These research activities, all of which included significant field components, focused on different aspects of the gold mineral systems and included gold districts with variable metal endowment (e.g. southern and northern Neoarchean Abitibi greenstone belt), geological setting (e.g. pre-, syn-, and
post-orogenic processes), and geological age (e.g. Paleoproterozoic Trans-Hudson, and Phanerozoic Appalachian orogenic belts).
The southern Abitibi is host to many different types of giant gold deposits (e.g. synvolcanic and orogenic gold ore systems), although the sources of ore-components for these mineral systems remained unclear. New TGI research addressed this knowledge gap and demonstrate that (1) diagenetic sulphides
(pyrite nodules) and their host sedimentary sequences within the Superior Province are pre-enriched in gold; (2) Archean calc-alkaline felsic volcanic centres associated with large synvolcanic gold deposits further suggest that igneous differentiation in the lower crust may be associated with the
generation of synvolcanic gold-rich magmatic-hydrothermal systems; and (3) undocumented upper mantle pathways existed, which were revealed by anomalous ore-forming element concentrations within cratonic mantle samples from the southern Superior Province. Together these research activities provide
new insights into the upgrading of ore components from the mantle to the upper crust, although the role of these pre-enriched source rocks to gold ore systems remains unclear.
Other research activities focused on the complete source-to-ore pathways of gold-bearing fluids for multiple gold districts across Canada. The similar pacing of events and timing of auriferous vein development within the overall tectonic evolution for several of these gold districts likely reflects
a common driver (e.g. upwelling asthenosphere) and/or tectonic triggers (e.g. crustal extension and associated magmatism). However, the contrasting metal endowment of areas with otherwise similar histories (e.g. southern versus northern Abitibi belt) suggests that the prospectivity of gold districts
is not entirely related to the large-scale drivers and triggers of ore-forming fluids. Moreover, long-term preservation is another critical factor in gold ore systems, which is promoted by rapid burial; limited post-ore remobilization during hydrothermal and metamorphic overprinting; and long-term
craton stability. Indications of preferential preservation, such as the occurrence of synorogenic polymict conglomerate, constitute key exploration criteria.
New analytical methods that were developed as part of TGI-5 are also providing new tools (e.g. rapid in situ element mapping and data interrogation approaches; new geochronological methods; clumped isotope thermometers) for recognizing ore-proximal depositional controls from the rock record. An
improved understanding of these controls and efficient vectoring tools are increasingly important for mineral exploration targeting.