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TitlePreliminary observations on styles of mineralization and sulphide-mineral zonation in the Cambrian Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive-sulphide deposit, Newfoundland and Labrador
AuthorGill, S B; Piercey, S J
SourceGeological Survey of Canada, Current Research (Online) no. 2014-5, 2014, 20 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; tetrahedrite; tennantite; stromeyerite; galena; facies; alteration; stratiform deposits; Dunnage Zone; Red Indian Line; Lemarchant volcanogenic massive sulphide deposit; Tally Pond belt; Paleozoic; Cambrian
Illustrationslocation maps; photomicrographs; photographs; tables; fence diagrams
ProgramTargeted Geoscience Initiative (TGI-4), Volcanogenic Massive Sulfide Ore Systems
Released2014 09 26
AbstractThe precious-metal-bearing, polymetallic, bimodal felsic Lemarchant volcanogenic massive-sulphide deposit is located in the Tally Pond belt, Dunnage Zone, Newfoundland Appalachians and consists of a stratiform, massive to semimassive sulphide zone and an underlying stringer sulphide zone. Five principal types of mineral assemblage are present: 1) semimassive white (low-Fe) sphalerite-granular barite-recrystallized pyrite-galena-minor tetrahedrite; 2A) bornite-galena-stromeyerite±chalcopyrite; 2B) bladed barite-coarse-grained tetrahedrite-galena-electrum-colusite±bournonite-polybasite-miargyrite; 3) massive red (high-Fe) sphalerite-fine- to medium-grained pyrite-chalcopyrite-galena; and 4) chalcopyrite-pyrite±orange sphalerite stringers. The stratiform sulphide zone contains the type 1 assemblage, which is crosscut by the type 2A and type 2B assemblages. The type 3 assemblage overprints the type 1 assemblage at the top of the stratiform zone. The basal stringer zone is host to the type 4 assemblage. The type 3 and type 4 assemblages represent minor zone refinement of the stratiform and stringer zones, as the hydrothermal fluids from which they were deposited were relatively hotter (>300°C) than the lower temperature fluid (<250°C) from which the type 1 and type 2 assemblages were deposited.
The Lemarchant deposit shows zone refinement typical of Kuroko-style volcanogenic massive-sulphide mineralization; however, the precious-metal-enriched low-Fe sphalerite, bornite, electrum, and sulphosalt-rich type 2 assemblages suggest processes analogous to high-sulphidation epithermal-style volcanogenic massive-sulphide mineralization early in the evolution of the deposit. A direct magmatic contribution to the hydrothermal fluid and intermittent boiling during deposition of the type 1 and type 2 assemblages may be partially responsible for precipitation of epithermal-suite minerals and precious-metal enrichment.
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. Lemarchant is a zinc-lead-barium-silver-gold deposit is located in the Tally Pond volcanic belt in Central Newfoundland. 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 (fluid temperature conditions on precious metals, and fluid boiling and possible magmatic input are implicated in precious metal sourcing and deposition.