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TitleInsight on the chemostratigraphy of the volcanic and intrusive rocks of the Lalor auriferous volcanogenic massive-sulphide deposit host succession, Snow Lake, Manitoba
AuthorCaté, A; Mercier-Langevin, P; Ross, P -S; Duff, S; Hannington, M; Gagné, S; Dubé, B
SourceGeological Survey of Canada, Current Research (Online) 2014-06, 2014, 23 pages, (Open Access)
PublisherNatural Resources Canada
Mediaon-line; digital
File formatpdf
AreaSnow Lake; Lalor
Lat/Long WENS-102.0000 -98.0000 56.0000 54.0000
Subjectseconomic geology; geochemistry; stratigraphy; mineral deposits; mineral assemblages; mineralization; gold; volcanogenic deposits; sulphides; deformation; metamorphism; alteration; hydrothermal alteration; volcanic rocks; igneous rocks; paragenesis; geochemical interpretations; Flin Flon Greenstone Belt; Lalor Deposit; chemostratigraphy; Precambrian; Proterozoic
Illustrationslocation maps; cross-sections; plots; tables
ProgramTargeted Geoscience Initiative (TGI-4), Volcanogenic Massive Sulfide Ore Systems
Released2014 11 18
AbstractLalor is a recently discovered auriferous Zn-Cu volcanogenic massive-sulphide deposit. It is located in the Paleoproterozoic Snow Lake arc assemblage, host to numerous past producing Cu-Zn and Zn-Cu volcanogenic massive-sulphide deposits. With an estimated tonnage of 25 Mt of ore (reserves+resources) including 73 t Au, Lalor is the largest volcanogenic massive-sulphide deposit in the Snow Lake area and its Au-rich nature provides a unique opportunity to document processes responsible for precious-metal enrichment in volcanogenic massive-sulphide systems. The Lalor deposit host rocks are predominantly volcanic (± intrusive) rocks that have been variably altered, deformed, and metamorphosed to amphibolite grade. A combination of immobile element geochemistry and petrographic observations is necessary to properly characterize the volcanic rocks due to major postemplacement modifications. Seven distinct chemostratigraphic units and two postvolcanogenic massive-sulphide intrusive (dyke) units are present in the Lalor host succession. Mafic to felsic volcanic units have calc-alkaline to transitional magmatic affinities. Some of these units are compositionally similar to the Moore basalt (units M1a and M1b) and Powderhouse dacite (unit F2) which represent the footwall of the Chisel, Chisel North, Ghost, and Lost volcanogenic massive-sulphide deposits; this suggests that the Lalor deposit is located within the volcanogenic massive-sulphide-fertile uppermost portion of the lower Chisel subsequence. The presence of massive-sulphide ore lenses in calc-alkaline mafic rocks lying above the Powderhouse dacite-like unit indicates the continuation of volcanogenic massive-sulphide-forming hydrothermal activity after the cessation of felsic volcanism in the lower Chisel subsequence. The presence of dykes with a trace-element signature similar to that of the Threehouse basalt, which is present immediately above the other volcanogenic massive-sulphide deposits of the lower Chisel subsequence, suggests the presence of this unit at a higher stratigraphic position in the now structurally truncated sequence.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. The Lalor deposit was recently discovered in the Snow Lake region of northern Manitoba. It consists of a large zinc, copper, gold, silver and lead deposit, the largest of the area. The concentration of gold in that deposit is exceptional when compared with similar deposits of the same type and the this report summarizes the local geologic setting and some of the principal characteristics indicating the presence of the deposit and possibly explaining the auriferous nature of the ore. The preliminary results presented in this report were obtained through the Targeted geoscientific Initiative 4, a Natural Resources Canada program that aims at developing tools in support of more effective exploration for buried ore deposits.