The early development of an Archean submarine caldera complex with emphasis on the Mattabi ash-flow tuff and its relationship to the Mattabi massive sulfide deposit

Abstract

The south Sturgeon Lake area of northwestern Ontario is underlain by an Archean submarine caldera complex which is host to six massive sulfide deposits. The complex is approximately 30 km in strike length and is partly filled by mesobreccias, subaqueous debris-flow deposits and other epiclastic rocks, as well as five major ash-flow tuff units. The most voluminous of these, the Mattabi ash-flow tuff, is up to 800 m in thickness and can be traced for more than 15 km across the caldera complex. Based on flow morphology and composition, the Mattabi ash-flow tuff is divisible into two distinct units: a bedded quartz crystal and pumice-rich unit (150-650 m thick), and a massive to poorly bedded ash unit (20-150 m thick). The bedded unit is host to the Mattabi massive sulfide deposit, as well as numerous other massive sulfide occurrences. In addition, this unit exhibits a pronounced stratigraphic and geochemical cyclicity. Individual beds (flow units) can be subdivided into basal quartz-and pumice-rich lower sections which are overlain by bedded ash tops; thicknesses of individual beds vary from 14 to 155 m. Each bed also exhibits a pronounced zonation of trace elements with high concentrations of Zr, Y, and Nb at and/ornear the base gradually decreasing upward into the ash tops. The overlying massive ash unit contains no known massive sulfide mineralization and lacks any pronounced geochemical zoning.The bedded nature and geochemical zonation of individual flow units can be explained by periodic eruptions from a zoned or layered, recharged siliceous magma chamber. The difference in flow morphology between the bedded unit and the overlying massive ash-flow tuff most likely reflects the deeper submarine nature of the eruptive vents associated with the bedded deposits. The periodic and subaqueous nature of the Mattabi eruptions is indicated by the presence of exhalites and massive sulfide lenses between flow units. The ore lenses, which comprise the Mattabi deposit, formed between eruptive events from high temperature fluids whose origin may be related to processes within the magma chamber.

Geodynamic setting, crustal architecture, and VMS metallogeny of ca. 2720 Ma greenstone belt assemblages of the northern Wawa subprovince, Superior Province

“…The dominance of siderite and chloritoid alteration associated with the Vanguard VMS prospect (Farrow 1993;Lodge and Chartrand 2013) is typical of Mattabi-type alteration systems. At the Mattabi VMS deposit, the siderite and chloritoid alteration is interpreted to have formed in relatively shallow water during effervescence of CO 2 that was derived from magmatic fluids or CO 2 -enriched seawater (Morton et al 1991;Franklin 1997;Holk et al 1998). The Calvert-Stares VMS prospect is dominated by Zn-Au mineralization with muscovite and iron-carbonate alteration (Bottrill 2003) and is typical of boiling hydrothermal system that may have had input from magmatic fluids, resulting in a volatile-rich, hydrothermal fluid capable of mobilizing gold (Hannington et al 1995;Dubé et al 2007).…”

Architecture et origine du système de minéralisation polymétallique du secteur lac Line, région de Chibougamau, Québec /

“…Il s'agit là d'une indication démontrant qu'à l'instar de plusieurs autres caideiras archéennes (Morton et al, 1991;Gibson et al, 1999;Mueller et al, 2004;Mueller et al, 2008;Pearson et Daigneault, 2009), on a affaire à un environnement de formation essentiellement sous-marin, bien que peu profond et localement émergeant à l'échelle régionale (Archer, 1983;Dimroth et al, 1984). Tavua, Fiji, Eaton et Setterfïeid, 1993;Banska Stiavnica, Slovaquie, Kodera et al, 2004).…”

Géologie de la mine East-Sullivan, Abitibi-Est, Val-d'or, Québec /

“…On retrouve des tufs, des coulées pyroclastiques et hyaloclastiques et des brèches de coulées (Morton et Franklin 1987;Groves et al 1988;Morton et al 1991). La minéralisation est associée aux unités de tufs fins lités d'origine pyroclastique (Morton et al 1991).…”

“…On retrouve des tufs, des coulées pyroclastiques et hyaloclastiques et des brèches de coulées (Morton et Franklin 1987;Groves et al 1988;Morton et al 1991). La minéralisation est associée aux unités de tufs fins lités d'origine pyroclastique (Morton et al 1991). Les laves bréchiques et à coussins sont aussi présentes (Groves et al 1988) avec un important pourcentage d'amygdules (jusqu'à 50 %) (Morton et Franklin 1987).…”

“…Les laves bréchiques et à coussins sont aussi présentes (Groves et al 1988) avec un important pourcentage d'amygdules (jusqu'à 50 %) (Morton et Franklin 1987). Ces assemblages de roches hautement vésiculaires et bréchiques sont interprétés comme des gites formés par l'interaction explosive de l'eau et du magma en milieu sous-marin peu profond ou subaérien (Morton et Franklin 1987;Groves et al 1988;Morton et al 1991). L'absence de vésicularité dans les roches produites à grande…”