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TitleDeciphering the multiple hydrothermal, metasomatic and structural events responsible for the formation and post-depositional evolution of the Paleoproterozoic Lalor auriferous VMS deposit, Snow Lake, Manitoba
AuthorCaté, A; Mercier-Langevin, P; Ross, P -S; Duff, S; Hannington, M; Dubé, B; Gagné, S
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Abstracts Volume vol. 37, 2014 p. 52-53
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20140450
PublisherGeological Association of Canada
PublisherMineralogical Association of Canada
Meeting GAC-MAC 2014; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Fredericton; CA; May 21-23, 2014
Mediaon-line; digital
File formatpdf
AreaSnow Lake; Lalor
Lat/Long WENS-102.0000 -98.0000 56.0000 54.0000
Subjectseconomic geology; mineral deposits; mineral assemblages; mineralization; gold; volcanogenic deposits; sulphides; deformation; metamorphism; alteration; hydrothermal alteration; volcanic rocks; igneous rocks; paragenesis; Flin Flon Greenstone Belt; Lalor Deposit; Precambrian; Proterozoic
ProgramTargeted Geoscience Initiative (TGI-4), Volcanogenic Massive Sulfide Ore Systems
AbstractThe Lalor auriferous VMS deposit is located in the ca. 1.85 Ga Snow Lake arc assemblage that is part of the Paleopropterozoic Flin Flon greenstone belt. The Snow Lake camp is host to numerous past producing Cu-Zn, Zn-Cu and Au-Zn-Cu VMS deposits and one orogenic Au deposit. Lalor is the largest deposit of the Snow Lake camp and also the richest in gold with reserves of 15.1 Mt at 7.2% Zn, 0.6% Cu, 1.9 g/t Au and 23.3 g/t Ag and resources of 12 Mt at 2.6% Zn, 0.9% Cu, 4.0 g/t Au and 27.8 g/t Ag, for a total size of approximately 27 Mt. It potentially contains up to 75 t Au. It consists of discrete Zn-Cu-Pb±Au-Ag semi-massive to massive sulphide lenses and zones of Au-Ag-Pb-Cu disseminated sulphides to sulphide-poor lenses. The ore zones are stratigraphically and/or structurally stacked in a complexly deformed and metamorphosed succession. The Lalor volcanic succession consists of intercalated mafic to felsic, tholeitic to calcalkaline, extrusive to intrusive volcanic rocks. These rocks are attributed to the Chisel mature arc sequence that hosts other Zn-rich VMS deposits in the area. The Lalor volcanic succession is structurally bounded at the top and at the West by distinct volcanic successions. Polyphased intense hydrothermal alteration, amphibolite grade metamorphism and at least three major deformation episodes have obliterated the primary composition and textures of the host volcanic rocks and the original geometry of the hydrothermal system. Five distinct hydrothermal alteration-related chemical associations can be distinguished: K, K-Mg-Fe, Mg-Fe, Mg-Ca and Ca associations. They can be further subdivided in numerous highly variable mineral assemblages characterized by variable amounts of metamorphic minerals such as amphiboles, chlorite, cordierite, biotite, muscovite, staurolite, gahnite, garnet, kyanite, sillimanite, diopside, carbonates and epidote. Crosscutting relationships and superposition of the chemical associations indicate the simultaneous development of the K, K-Mg-Fe and Mg-Fe chemical associations, which were later overprinted by the Mg-Ca association. These chemical associations are restricted to the footwall of the orebody. The Ca chemical association is widespread and related to a late overprinting metasomatic event. While base metal-rich massive sulphide lenses are clearly associated with the initial hydrothermal events (K, K-Mg-Fe and Mg-Fe), gold-rich sulphide-poor zones seem to overprint the early chemical associations, suggesting local metamorphic remobilization and/or a late input of precious metals in the system.