Felsic Volcanic Rock Distributions in the Abitibi Subprovince: A Monte Carlo Approach to Constrain Volcanogenic Massive Sulfide Formation and Crustal Evolution

Abstract

The Neoarchean Abitibi subprovince hosts more than half of all known Archean volcanogenic massive sulfide (VMS) deposits worldwide. Although most classify as bimodal mafic, reflecting a dominance of mafic volcanic rocks, they are commonly proximal to or hosted by felsic volcanic successions. These felsic volcanic rocks provide key insights into VMS formation, yet it remains unclear whether they are anomalously abundant in areas with VMS endowment compared with the broader volcanic stratigraphy. This study uses new assemblage and lithologic map compilations of the Abitibi subprovince that enable quantitative estimates of felsic volcanic rock proportions. Volcanogenic massive sulfide zones are defined as areas within a 15-km radius of the largest deposit. By this definition, ~70% of zones contain felsic proportions exceeding the subprovince-wide volcanic background of ~7%. Monte Carlo simulations (n = 1,000) confirm that this enrichment is highly unlikely under random placement. The results reinforce a robust empirical association between VMS deposits and localized felsic volcanic centers. These centers are interpreted as regions of unusually evolved crust within their larger assemblages, where crustal growth was concentrated and accelerated through rifting, creating deep crustal permeability and accommodating the extension required for thermally mature crust. Within or proximal to felsic centers, deep crustal structures coupled with elevated heat flow from increased volumes of volcanic and subvolcanic felsic and mafic magma produced an environment favorable for VMS formation. Collectively, this analysis provides new evidence for the role of felsic centers in VMS formation and offers an additional method for assessing VMS potential in the Abitibi and other greenstone belts.