Significance of Pre-1860 Ma Granitoid Magmatism for Crustal Evolution and Exploration Targeting in the Flin Flon Assemblage, Trans-Hudson Orogen, Canada

Abstract

Granitoid plutonism, a significant contributor to orogenic evolution, is a commonly overlooked vector in exploration targeting. Using the Flin Flon-Glennie Complex of the Trans-Hudson orogen as a template, we show that the geochemistry of granitoid rocks can be a useful parameter in differentiating prospective and nonprospective areas for volcanic-hosted massive sulfide (VHMS) deposits. The Flin Flon-Glennie Complex includes 1910 to 1860 Ma plutonic rocks that can be subdivided into three suites: (1) juvenile arc-related rocks of ferroan and magnesian subtypes, (2) contaminated arc-related rocks, and (3) successor arc-related rocks of both low and high Sr/Y ratio. Petrogenesis of ferroan juvenile and low Sr/Y successor arc plutons indicates they formed in regions of thinner crust and hence would have been associated with higher heat flow and arc rifting—conditions that favor VHMS endowment. Regions of the orogen with both ferroan and low Sr/Y plutonic subtypes were long-lived zones of thin crust and preserve VHMS mineralization related to both juvenile and successor arc magmatism. In contrast, volcanic belts dominated by contaminated arc or high Sr/Y successor arc plutons formed on thicker substrates, with contaminated arc rocks built on Archean-Paleoproterozoic pericratonic slivers and high Sr/Y successor arc rocks associated with submarine to subaerial arc systems. These regions of thicker crust demonstrably lack VHMS deposits and were also the locus for late unroofing. Our results suggest that pluton geochemistry regionally correlates with mineral occurrence and could represent a useful regional exploration tool in buried or poorly exposed parts of the Flin Flon-Glennie Complex and other Paleoproterozoic orogens.