Publication Type:Journal Article
Source:Canadian Journal of Earth SciencesCanadian Journal of Earth Sciences, National Research Council of Canada, Ottawa, ON, Canada, Volume 54, Number 6, p.654-676 (2017)
Keywords:Birch Lake, Canada, Canadian Shield, chemical composition, eruptions, felsic composition, Flin Flon Belt, igneous rocks, isotope ratios, Isotopes, Lead, lithofacies, lithostratigraphy, Manitoba, metals, Nd-144/Nd-143, neodymium, North America, Paleoproterozoic, Pb-206/Pb-204, Pb-207/Pb-204, Pb-208/Pb-204, plate tectonics, Precambrian, proterozoic, pyroclastic flows, pyroclastics, radioactive isotopes, rare earths, rifting, Snow Lake Manitoba, Stable isotopes, stratigraphic units, tectonics, upper Precambrian, volcanic rocks, VOLCANISM, Western Canada
The thrust-bounded McLeod Road - Birch Lake (MB) sequence occurs within the Paleoproterozoic Snow Lake arc (SLA) assemblage of the Flin Flon belt. Stratigraphic correlation of volcanic strata of the MB sequence with strata of the thrust-bounded Chisel sequence indicates that distinctive, submarine, eruption-fed, pyroclastic flow deposits are more extensive and voluminous than previously recognized (>10 km (super 3) ). These voluminous felsic pyroclastic deposits define a distinct magmatic and explosive volcanic event during bimodal volcanism that accompanied rifting of the SLA. The felsic pyroclastic deposits define the remnants of a basin, or of nested basins, that formed during arc rifting and subsidence, and their eruption immediately preceded formation of the Chisel sequence volcanogenic massive sulfide (VMS) deposits. Although the Chisel sequence ore interval is recognized in the MB sequence, the lack of VMS-related alteration indicates that VMS hydrothermal activity was restricted to the Chisel portion of the basin. However, the MB sequence is host to the younger Snow Lake gold mine, a 1.4M oz (43 699 kg) gold producer. The overlying MORB-like Birch Lake basalts, if conformable with the MB sequence, may represent a progression from a rifted-arc to a back-arc setting. However, if they are thrust fault bounded, then they may represent the initial phases of arc-rifting, prior to the voluminous felsic pyroclastic eruptions. Correlation and integrity of stratigraphy between the thrust-bounded MB and SLA sequences indicates that the bounding thrust faults, which developed during accretionary processes, have less regional significance than previously interpreted.
GeoRef, Copyright 2018, American Geological Institute.<br/>2017-068536