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TitleMineralogy and styles of barite-rich Zn-Pb-Ba-Ag-Au mineralization in the Lemarchant volcanogenic massive sulfide (VMS) deposit
AuthorGill, S B; Piercey, S J; Devine, C A; Copeland, D A
SourceGeological Association of Canada-Mineralogical Association of Canada, Joint Annual Meeting, Programs with Abstracts vol. 36, 2013 p. 103
LinksOnline - En ligne
Alt SeriesEarth Sciences Sector, Contribution Series 20140464
PublisherGeological Association of Canada
PublisherMineralogical Association of Canada
MeetingGAC-MAC 2013; Joint annual meeting of Geological Association of Canada and Mineralogical Association of Canada; Winnipeg; CA; May 22-24, 2013
Mediaon-line; digital
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; tetrahedrite; tennantite; stromeyerite; galena; facies; alteration; stratiform deposits; Dunnage Zone; Red Indian Line; Lemarchant volcanogenic massive sulphide deposit; Tally Pond belt; Paleozoic; Cambrian
ProgramTargeted Geoscience Initiative (TGI-4), Volcanogenic Massive Sulfide Ore Systems
AbstractThe Zn-Pb-Ba-Ag-Au Lemarchant volcanogenic massive sulfide (VMS) deposit is a recently discovered Kuroko-style VMS deposit located in the Central Mobile Belt, Newfoundland. The deposit has a geological resource (NI43-101 compliant) of 2.58 Mt at 0.49% Cu, 4.51% Zn, 1.01% Pb, 54.62g/t Ag, and 1.00 g/t Au. Characteristic of the deposit is an upper barite-rich zone that contains abundant sulfides, sulfosalts, and anomalous precious metals. Notably, while much of the barite is massive, bladed aggregates of barite are locally observed. The ore mineral assemblage in this zone consists of barite, abundant low-Fe (white-yellow) sphalerite, and Pb-Sb-Ag-As-bearing sulfosalts, including tennantite, tetrahedrite, friebergite, boulangerite, bournonite, and jamesonite, that are intergrown with bornite, galena, and chalcopyrite. Elevated Au values are associated with the barite-rich layer. Although minor visible free gold is present in the barite of some drill holes, Au is rarely observed and exists either sub-microscopically or as inclusions in other ore minerals such as pyrite and arsenopyrite. Silver occurs primarily in tetrahedrite, and as stromeryite associated with bornite and barite. Observed precious metal and mineral associations indicate that deposition within the barite-rich mineralization was likely from low temperature (<300°C) hydrothermal fluids. The barite layer may have influenced the anomalously high Au-Ag grade found at Lemarchant, acting as an insulator or chemical trap when the system was active to prevent dissipation of Au-Ag in hydrothermal fluid. The presence of large, tabular barite crystals associated with precious metals suggests fluid boiling at shallow water depths (<1500m). Further detailed mineralogical, mineral chemistry, sulfur isotope, and thermodynamic calculations are required to better understand the setting of mineralization at Lemarchant.