Precambrian lode gold deposits - a summary of TGI-4 contributions to the understanding of lode gold deposits, with an emphasis on implications for exploration

Abstract

The TGI-4 Lode Gold project, which comprises numerous site-specific and thematic research activities, covers the entire spectrum of crustal settings for lode gold deposits, from orogenic banded iron formationhosted and greenstone-hosted quartz carbonate vein-type gold deposits formed deep in the crust (>5 km), to intrusion-related deposits that are formed at shallower crustal levels (~2-5 km), and to deposits formed at or near the seafloor. Herein we synthesize a number of important project contributions that have significant implications for on-going mineral exploration for hidden deposits. Among the key findings is a newly established link between major faults, their early evolution, syntectonic magmatism and synorogenic sedimentary basin evolution, and gold metallogenesis in various greenstone belts. The revised model incorporates a phase of tectonic extension-a distinct feature recognized in gold-rich settings worldwide-that is applicable to mineral exploration targeting across the Canadian Shield. Importantly, the simultaneous multidisciplinary study of a number of large banded iron formation-hosted gold deposits and districts allows for the development of a unifying genetic model for such deposits that integrates critical structural, stratigraphic, hydrothermal, and metamorphic elements. Several key features that are common to all of the studied deposits, but elements specific to dominantly banded iron formation-hosted gold deposits or to deposits that are only partly hosted in banded iron formation, were also established. The Lode Gold project also bridges a major knowledge gap by characterizing a spectrum of "unusual" or "atypical" gold deposits in the Superior Province. The new and revised models incorporate synvolcanic as well as pre-deformation and synorogenic synmagmatic or intrusion-related gold deposits that represent a large part of the newly discovered resources in the Canadian Shield in both "brownfield" and "greenfield" exploration environments.

Results of LA-ICP-MS sulfide mapping from Algoma-type BIF gold systems with implications for the nature of mineralizing fluids, metal sources, and deposit models

“…Algoma-type banded iron formations (BIFs), which are chemical sedimentary rocks comprised of alternating layers of ironrich minerals (oxides, carbonates, silicates) and chert, represent a significant host rock for gold mineralization in Precambrian terranes (e.g., Homestake and Musselwhite deposits; Frei et al 2008;Oswald et al 2015). The timing and genesis of this style of gold mineralization (syngenetic versus epigenetic models) have been the subject of considerable research and debate over the past few decades and continues in light of new discoveries (Kerswill 1993;Groves et al 1998;Goldfarb et al 2001Goldfarb et al , 2005Dubé et al 2015;Steadman and Large 2016).…”