Evolution of the subaqueous to near-emergent Joutel volcanic complex, Northern Volcanic Zone, Abitibi Subprovince, Quebec, Canada

The 5–7 km thick Archean Joutel volcanic complex (JVC), composed of basalt to rhyolite, is represented by five volcanic phases. Initial volcanic construction features effusive mafic volcanism characterized by massive, pillowed and pillow breccia flows with an interdigitated lapilli–tuff–breccia and lapilli–tuff (phases 1 and 1′). The principal construction phase of the JVC (phase 2) is host to volcanogenic massive sulphide deposits and is associated with massive, flow banded and lobate rhyolite to dacite flows with associated lapilli–tuff–breccias derived either from autoclastic or hydroclastic fragmentation processes. Felsic volcanism continued with the emplacement of massive to brecciated flows (phase 3b), whereas deposition of turbiditic tuffs, lapilli–tuffs, lapilli–tuff–breccias is associated with resedimented mafic volcanics (phase 3a). Phases 4 and 5 are associated with the construction of a second volcanic center. Phase 4 is interpreted as mostly pyroclastic deposits, whereas tuffs, lapilli–tuffs and lapilli–tuff–breccias of phase 5 are host to synvolcanic Au–Ag mineralisation and are interpreted as talus deposits. The Zr/Y and La/Yb ratios of phase 1 show a tholeiitic affinity, whereas phases 2 and 3 are transitional and phases 1′, 4 and 5 are calc-alkaline. Uranium–lead geochronology indicates 7 Ma between construction of the transitional and the calc-alkaline centers (2728–2721 Ma). The geochemistry suggests that all phases (except phase 1) are consistent with variable input of subduction-related processes. The mafic-felsic JVC, a composite volcano that formed on a paleo-sea floor, displays deep-water effusive dominant to shallow-water pyroclastic and volcaniclastic dominant volcanic construction, as indicated by pillowed flows, turbiditic tuffs, stromatolite fragments and synvolcanic alteration types. Geochemistry and physical volcanology of the JVC are consistent with construction in a rifted island arc or back arc setting.