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

¹ Department of Geology, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick, E3B 5A3.
² Xstrata Zinc plc., Exploration, Box 899 Matagami, Quebec J0Y 2A0.

Diamond-drill hole DDH-B357, located 1.5 km north of the Brunswick No. 6 Zn-Pb-Cu-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 (Fe₂O₃^T 21.4 wt.%) likely represent cogenetic hydrothermal sedimentary units because they display a common geochemical signature: Fe₂O₃^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.%; P₂O₅ = 1.43 ± 1.00 wt.%), oxidized signature (Fe/Mn = 10 ± 6), as well as a common immobile element signature (Zr/TiO₂ = 0.025 ± 0.007) representative of a pelagic source. The calc-alkaline to transitional host volcanic rocks can be discriminated by Zr/TiO₂, and to a lesser extent by Th/Nb: Nepisiguit Falls Formation: Zr/TiO₂ = 0.053 ± 0.004, Th/Nb = 1.08 ± 0.37; Flat Landing Brook Formation: Zr/TiO₂ = 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 F₂ 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.

Key Words: Massive sulfide deposit • Iron formation • Felsic volcanic rocks • Geochemistry • Chemostratigraphy • Deformation • Brunswick No. 6 • Bathurst Mining Camp

This article has been cited by other articles:

				D.R. LENTZ and S.R. McCUTCHEON The Brunswick No. 6 Massive Sulfide Deposit, Bathurst Mining Camp, Northern New Brunswick, Canada: A Synopsis of the Geology and Hydrothermal Alteration System Exploration and Mining Geology, July 1, 2006; 15(3-4): 1 - 34. [Abstract] [Full Text] [PDF]