Chemostratigraphy at the Brunswick No. 6 Volcanic-Sediment-Hosted Massive Sulfide Deposit, New Brunswick: Resolving Geometry from Drill Core in Deformed Felsic Volcanic Rocks

Abstract

Diamond-drill hole DDH-B357, located 1.5 km north of the Brunswick No. 6 Zn-PbCu-Ag volcanic-sediment-hosted massive sulfide (VSHMS) deposit, intersects three exhalative horizons within variably altered felsic volcanic rocks of the Nepisiguit Falls and Flat Landing Brook formations. These three petrographically indistinguishable iron formation intervals (Fe 2 O 3 T ≥ 21.4 wt.%) likely represent cogenetic hydrothermal sedimentary units because they display a common geochemical signature: Fe 2 O 3 T = 42.9 ± 10.5 wt.%, MnO = 5.4 ± 3.1 wt.%, elevated base metal values (Zn+Pb = 1999 ± 1091 ppm), strong enrichment in additional exhalative components (CaO = 5.3 ± 3.9 wt.%; P 2 O 5 = 1.43 ± 1.00 wt.%), oxidized signature (Fe/Mn = 10 ± 6), as well as a common immobile element signature (Zr/TiO 2 = 0.025 ± 0.007) representative of a pelagic source. The calc-alkaline to transitional host volcanic rocks can be discriminated by Zr/TiO 2 , and to a lesser extent by Th/Nb: Nepisiguit Falls Formation: Zr/TiO 2 = 0.053 ± 0.004, Th/Nb = 1.08 ± 0.37; Flat Landing Brook Formation: Zr/TiO 2 = 0.107 ± 0.043, Th/Nb = 0.86 ± 0.17. A symmetrical repetition of the footwall-iron formation-hanging wall stratigraphic sequence is observed in DDH-B357, with distinct felsic volcanic rock domains separated by the three iron formations. This is best explained by parasitic F 2 folds on the west flank of the south-plunging Brunswick antiform, similar to the fold closures known to host massive sulfide accumulations in the Brunswick No. 6 and No. 12 mines. Iron formation geochemistry and felsic volcanic rock chemostratigraphy from drill core sampling can provide an effective mineral exploration tool for the structurally complex rocks of the Bathurst Mining Camp.Sommaire -Le forage au diamant DDH-B357, situé à 1.5 km au nord du gisement de Sulfures Massifs à Encaissant Volcanique et Sédimentaire (SMEVS) de Zn-Pb-Cu-Ag Brunswick No. 6 recoupe trois horizons exhalatifs au sein des roches volcaniques felsiques diversement altérées des formations de Nepisiguit Falls et de Flat Landing Brook. Ces trois intervalles de formation de fer, impossibles à distinguer pétrographiquement les uns des autres, représentent vraisemblablement des unités sédimentaires hydrothermales cogénétiques sur la base de leur signature géochimique commune: Fe 2 O 3 T = 42.9 ± 10.5 % poids, MnO = 5.4 ± 3.1 % poids, des teneurs élevées en métaux usuels (Zn+Pb = 1999 ± 1091 ppm), un fort enrichissement en composantes exhalatives additionnelles (CaO = 5.3 ± 3.9 % poids; P 2 O 5 = 1.43 ± 1.00 % poids), une signature oxydée (Fe/ Mn = 10 ± 6), ainsi qu'une signature d'éléments immobiles communs (Zr/TiO 2 = 0.025 ± 0.007) indicative d'une source pélagique. Les roches volcaniques encaissantes calco-alcalines à transitionnelles peuvent êtres reconnues par leur rapport Zr/TiO 2 , et à un moindre degré par leur rapport Th/Nb: Formation de Nepisiguit Falls: Zr/TiO 2 = 0.053 ± 0.004, Th/Nb = 1.08 ± 0.37; Formation de Flat Landing Brook: Zr/TiO 2 = 0.107 ± 0.043, Th/Nb = 0.86 ± 0.17. Une répétiti...

Microfabrics, In Situ Trace Element Compositions of Pyrite, and the Sulfur Isotope Chemistry of Sulfides from the Xitieshan Pb-Zn Deposit, Qinghai Province, Northwest China: Analysis and Implications

“…On the other hand, previous S isotope studies have been carried out on deposits of the Iberian Pyrite Belt, Bathurst Mining Camp and Finlayson Lake District (Wolverine) [81][82][83][84]. These are considered a transitional type named VSHMS deposit, which occurs between typical VMS and SEDEX deposits [84][85][86][87]. The studies showed that δ 34 S values in the sulfides of these deposits are roughly positive with minor negative values.…”