Preliminary mineralogy of barite-associated sulphide mineralization in the Ordovician Zn-Pb-Cu-Ag-Au Lemarchant volcanogenic massive sulphide deposit, Newfoundland and Labrador

Abstract

The 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.

Multiple sulphur and lead sources recorded in hydrothermal exhalites associated with the Lemarchant volcanogenic massive sulphide deposit, central Newfoundland, Canada

“…Fraser et al 2012; Gill and Piercey 2014;Gill 2015). In addition to typical VMS 189 sulphides (pyrite, sphalerite, galena, and chalcopyrite), the massive sulphides also contain 190 tetrahedrite-tennantite, bornite, stromeyerite, and electrum Gill 191 2015).…”

Geology, Mineralogy, and Lithogeochemistry of Metalliferous Mudstones Associated with the Lemarchant Volcanogenic Massive Sulfide Deposit, Tally Pond Belt, Central Newfoundland

“…2B) is 1.7 to 30.4 m thick and consists of a barite-rich outer zone that grades into a Pb-Zn sulfide-rich zone, and an interior zone with Zn-Cu sulfides, which grades into stringer mineralization at depth, typical of bimodal felsic/Kuroko-style mineralization (Copeland et al, 2009;Fraser et al, 2012;Gill and Piercey, 2014).…”

“…The sulfosalt-rich mineralogy, barite-calcite textures, and anomalous element suite in the ores have led to the interpretation that the Lemarchant deposit was a shallow-water VMS deposit with both VMS and epithermal features (Gill and Piercey, 2014).…”

“…The deposit contains typical VMS sulfides (pyrite, sphalerite, galena, and chalcopyrite) but also abundant sulfosalts (e.g., tetrahedrite-tennantite), bornite, stromeyerite, electrum, bladed barite, and calcite; as well as minerals that contain enrichments in epithermal suite elements (e.g., Au, Ag, As, Hg, Sb, Bi; Gill and Piercey, 2014). The sulfosalt-rich mineralogy, barite-calcite textures, and anomalous element suite in the ores have led to the interpretation that the Lemarchant deposit was a shallow-water VMS deposit with both VMS and epithermal features (Gill and Piercey, 2014).…”

Role of metalliferous mudstones and detrital shales in the localization, genesis, and paleoenvironment of volcanogenic massive sulphide deposits of the Tally Pond volcanic belt, central Newfoundland, Canada

“…Precision and accuracy of the analyses were determined using duplicates and 82 reference materials following methods described in Jenner (1996) and Piercey (2014). 83…”