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TitleGeology and Au enrichment processes at the Paleoproterozoic Lalor auriferous volcanogenic massive sulphide deposit, Snow Lake, Manitoba
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AuthorCaté, A; Mercier-Langevin, P; Ross, P -S; Duff, S; Hannington, M D; Dubé, B; Gagné, S
SourceTargeted Geoscience Initiative 4: Contributions to the understanding of volcanogenic massive sulphide deposit genesis and exploration methods development; by Peter, J M (ed.); Mercier-Langevin, P (ed.); Geological Survey of Canada, Open File 7853, 2015 p. 131-145, https://doi.org/10.4095/296549 (Open Access)
LinksCanadian Database of Geochemical Surveys, downloadable files
LinksBanque de données de levés géochimiques du Canada, fichiers téléchargeables
Year2015
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediaon-line; digital
RelatedThis publication is contained in Peter, J M; Mercier-Langevin, P; (2015). Targeted Geoscience Initiative 4: Contributions to the understanding of volcanogenic massive sulphide deposit genesis and exploration methods development, Geological Survey of Canada, Open File 7853
File formatpdf
ProvinceManitoba
NTS63K/16
AreaSnow Lake; Lalor
Lat/Long WENS-102.0000 -98.0000 56.0000 54.0000
Subjectseconomic geology; stratigraphy; Archean; volcanogenic deposits; sulphide deposits; alteration; metamorphism; mineral assemblages; mineralization; exploration guidelines; volcanic rocks; mineral deposits; gold; sulphides; deformation; hydrothermal alteration; igneous rocks; paragenesis; geochemical interpretations; hydrothermal alteration; Flin Flon Greenstone Belt; Lalor Deposit; Precambrian; Proterozoic
Illustrationslocation maps; plots; photomicrographs
ProgramVolcanogenic Massive Sulfide Ore Systems, Targeted Geoscience Initiative (TGI-4)
Released2015 06 11
AbstractThe Paleoproterozoic Lalor auriferous volcanogenic massive sulphide deposit, located in the Snow Lake mining camp, Manitoba, is hosted in a complex volcanic package referred to as the Lalor volcanic succession. The deposit consists of stratigraphically and structurally stacked Zn-rich, Au-rich, and Cu-Au-rich ore lenses. The host volcanic succession comprises mafic to felsic tholeiitic to calc-alkaline extrusive to intrusive volcanic rocks of the ca. 1.89 Ga Lower Chisel subsequence, and the ore is hosted in both mafic and felsic rocks. Atypical of the other Zn-rich deposits of the Snow Lake district, the Lalor deposit is not situated at the top of the Lower Chisel subsequence, but is at a slightly lower stratigraphic position. The volcanic rocks that host the deposit were affected by intense and laterally extensive ore-related hydrothermal alteration. These altered rocks were subsequently subjected to syndeformational amphibolitegrade metamorphism that resulted in the development of distinct minerals and metamorphic mineral assemblages of varying composition from variably altered precursor lithologies. Five distinct alteration- and metasomatism- related chemical associations (K, K-Mg-Fe, Mg-Fe, Mg-Ca, and Ca) are recognized based on mineralogical (mineral assemblages) and bulk geochemical compositions. Mapping of the host volcanic rocks and ore-related mineral assemblages and chemical associations at Lalor indicates the following: 1) the Zn-rich massive sulphide lenses are preferentially associated with the low- to high-temperature K and Mg- Ca alteration zones; 2) the Cu-Au-rich zones, which occur at depth, stratigraphically below the Zn-rich mineralization, are hosted in transposed, presumably originally discordant high-temperature Mg-Fe altered rocks; and 3) Au has been in part locally remobilized into low-strain sites that are not now spatially associated with any particular chemical association. The Lalor volcanic succession is affected by polyphase deformation that has strongly influenced the geometry of the Lalor deposit. Pre-D2 (synvolcanic?) deformation is evidenced by the abrupt termination of the intensely altered Lalor volcanic succession to the southwest and the presence of chemically distinctive and unaltered volcanic rocks of the Western succession. The present geometry of the deposit is largely controlled by D2 deformational structures with important stretching (L2), flattening (S2), and structural staking (F2 folding and syn- to late-D2 transposition and shearing). The D2 deformation and associated peak metamorphic conditions are thought to be responsible for the local remobilization of Au sulphosalts and some sulphides.
GEOSCAN ID296549