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TitlePreliminary mineralogy of barite-associated sulphide mineralization in the Ordovician Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive sulphide deposit, Newfoundland and Labrador
AuthorGill, S B; Piercey, S J; Devine, C A
SourceGeological Survey of Canada, Current Research (Online) no. 2013-17, 2013, 18 pages, (Open Access)
PublisherNatural Resources Canada
Mediaon-line; digital
RelatedNRCan photo(s) in this publication
File formatpdf
ProvinceNewfoundland and Labrador
AreaRed Indian Lake
Lat/Long WENS -56.7500 -56.5833 48.6667 48.5000
Subjectsmineralogy; economic geology; mineral occurrences; mineral deposits; volcanogenic deposits; mineralization; zinc; lead; copper; silver; gold; sulphides; sulphide deposits; barite; sphalerite; pyrite; chalcopyrite; bornite; enargite; tetrahedrite; tennantite; stromeyerite; galena; facies; Dunnage Zone; Newfoundland Central Mobile Belt; Red Indian Line; Lemarchant volcanogenic massive sulphide deposit; Paleozoic; Ordovician
Illustrationslocation maps; cross-sections; photomicrographs; photographs; diagrams
ProgramTargeted Geoscience Initiative (TGI-4), Volcanogenic Massive Sulfide Ore Systems
Released2013 10 24
AbstractThe bimodal felsic Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive sulphide (VMS) deposit is located in central Newfoundland. Characteristic of the deposit is a mineralized barite lens that contains abundant sulphosalts and anomalous precious metals. While much of the barite is massive, bladed aggregates of barite are locally present. The mineralized barite lens consists of three mineral assemblages (or facies) that grade from the outer barite-rich mineralization toward the sulphide-rich base as follows: 1) facies A: white to honey-coloured sphalerite+pyrite+chalcopyrite+bornite>enargite±Au; 2) facies B: white sphalerite+galena+pyrite+tetrahedrite>tennantite+stromeyerite+Ag-tetrahedrite; and 3) facies C: honey-brown (and minor red) sphalerite+chalcopyrite+pyrite±galena. Iron content of sphalerite grades from higher values in the outer barite lens and proximal rhyolite, to lower values in the central barite lens. Minor visible free gold is present in barite-rich facies A mineralization.
The interpreted primary mineralization sequence of these three facies begins with deposition of sphalerite and fine-grained pyrite, and penecontemporaneous crystallization of tennantite-tetrahedrite, galena, and enargite, followed by sulphide replacement by bornite and chalcopyrite, late-stage stromeyerite mineralization, and recrystallization of euhedral pyrite.
The Lemarchant deposit is similar to other barite-rich, Kuroko-style VMS deposits, and is especially notable for its sulphosalt-rich mineral assemblage and precious-metal-bearing minerals. Further detailed mineral chemistry, sulphur and lead isotope analyses, and thermodynamic calculations will be undertaken to understand the siting of precious metals and the processes that resulted in precious metal enrichment at Lemarchant.
Summary(Plain Language Summary, not published)
Lemarchant is a zinc-lead-barium-silver-gold deposit is located in the Tally Pond volcanic belt in Central Newfoundland; the deposit is classified as a bimodal volcanogenic massive sulfide (VMS) deposit. The distributions of the ore and gangue minerals have been determined, in order to understand the mechanism of precious metal deposition and siting in this, and other similar deposits in Canada and elsewhere. The occurrence of the minerals barite, sphalerite, galena, chalcopyrite, bornite, enargite, tetrahedrite (including silver-bearing variety), tennantite, stromeyerite, and native gold is described, and this, together with their mineralogic associations, can be used to provide insights into the depositional controls on precious metals. Three distinct mineral facies are identified.