Volcanic reconstruction of the paleoproterozoic powderhouse formation, Snow Lake, Manitoba, Canada: implications for controls on volcanogenic massive sulfide formation
Date
2019-02-08
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Abstract
The Powderhouse formation of the Paleoproterozoic Snow Lake arc assemblage comprises the
stratigraphic footwall to six volcanogenic massive sulfide deposits (VMS) at Snow Lake,
Manitoba, Canada. It is interpreted to be a product of voluminous pyroclastic eruptions and
concomitant subsidence followed by a period of relative volcanic quiescence that was dominated
by suspension sedimentation, the reworking of these previously deposited pyroclastic units by
debris flows and bottom currents, and localized emplacement of rhyolite domes. The rhyolite
domes are spatially associated with the Chisel, Chisel North, Lost, Ghost, Photo and Lalor
deposits.
The Chisel, Lalor and Lost members comprise the Powderhouse formation and are
subdivided into thirteen lithologically and chemically distinct lithofacies and allows, for the first
time, correlation between the South Chisel basin and Lalor area. The Chisel and Lalor members
contain lithofacies and bedforms that are characteristic of emplacement by subaqueous
pyroclastic mass flows and concomitant subsidence. The Chisel member also contains coarse
volcaniclastic breccias emplaced by mass debris flows derived from movement along fault scarps
after early pyroclastic eruptions, and during continued subsidence. The Lost member consists of
lithofacies deposited by mass flows generated from faults scraps during continued subsidence,
but also contains lithofacies reworked by bottom currents and those deposited by suspension
sedimentation, and locally coherent rhyolite. The Lost member represents a time stratigraphic
interval, the “Ore Interval”, that marks contemporaneous rhyolite dome eruption, VMS
formation, and a hiatus in explosive volcanism.
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Keywords
Paleoproterozoic powderhouse formation, Snow Lake, Manitoba, volcanogenic massive sulfide deposits (VMS), Chisel, Lalor, Lost members, voluminous pyroclastic eruptions, concomitant subsidence, rhyolite dome eruption, explosive volcanism