The Matagami District, Abitibi Greenstone Belt, Canada: Volcanic Controls on Archean Volcanogenic Massive Sulfide Deposits Associated with Voluminous Felsic Volcanism

Abstract

Volcanogenic massive sulfide (VMS) deposits and seafloor massive sulfide (SMS) deposits have a spatial and genetic connection with contemporaneous volcanism. The control exerted by the volcanic succession (e.g., rock type, architecture and facies) on the nature and style of the ore and alteration (e.g., subsea-floor replacement vs. exhalative, or discordant vs. conformable) is significant, making it imperative to understand the local volcanology in developing better genetic and exploration models.

Volcanology, chemo-stratigraphy, geochronology, hydrothermal alteration and VMS potential of the Lemoine Member of the Waconichi Formation, Chibougamau district, Abitibi greenstone belt, Québec

“…(5) the geology is similar to that of the prolific Matagami district (Debreil et al 2018). The high abundance of felsic to mafic intrusions within the lower part of the Lemoine Member, and the proximity with the intrusive LDC, means that focused heat flow was likely (Galley 2003).…”

“…A less commonly employed strategy is to map facies variations within the stratigraphy in order to locate volcanic vents and reconstruct the volcanic architecture of a prospective area (Gibson et al 1999;Rogers et al 2008;Debreil et al 2018). The importance of locating volcanic vents, or at least identifying vent-proximal environments, is that volcanic vents may coincide with hydrothermal vents, the two being often controlled by syn-volcanic faults (Gibson et al 1999).…”

“…The importance of locating volcanic vents, or at least identifying vent-proximal environments, is that volcanic vents may coincide with hydrothermal vents, the two being often controlled by syn-volcanic faults (Gibson et al 1999). Before facies variations can be mapped within individual units, a detailed stratigraphy of the volcanic rocks has to be established, by combining primary textures, such as phenocrysts, and immobile element ratios (MacLean and Barrett 1993;Barrett and MacLean 1999;Rogers et al 2008;Debreil et al 2018). This detailed stratigraphic knowledge is also useful to follow prospective horizons laterally, since VMS deposits tend to occur at specific stratigraphic positions within a district (Franklin et al 2005;Galley et al 2007) that are often, but not always, manifested by thin "marker" horizons referred to as iron formations, exhalites, or tuffites, depending on their compositions.…”

“…Only two significant VMS deposits, Lemoine and Scott Lake, are known so far in the Chigougamau district. Further west, the Matagami district, which has a very similar geology and age, contains 20 known VMS deposits, including the Mattagami Lake (Roberts 1975) and Bracemac-McLeod deposits (Genna et al 2014;Debreil et al 2018).…”

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“…3). The succession includes the Watson Lake and Wabassee groups (Sharpe, 1968;Debreil et al, 2018). Given the great thickness of the Wabassee Group, the lithologic succession is dominated by mafic to intermediate flows with a smaller proportion of felsic flows.…”