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Brine-pool deposition for the Zn-Pb-Cu massive sulphide deposits of the Bathurst mining camp, New Brunswick, Canada. II. Ocean anoxia during mineralisation
journal contribution
posted on 2023-05-16, 23:35 authored by Solomon, MCurrent models of massive sulphide ore genesis in the Bathurst mining camp, New Brunswick, involve settling of sulphide particles from a stagnating, low-salinity hydrothermal plume spreading laterally in an anoxic ocean layer with minimal sulphate content. There is fragmentary evidence of ocean anoxia in the form of local fine lamination in the shales that host some of the deposits but the total organic carbon, S, Fe, U/Th, Ni/Co, V/Ni and V/Cr relationships indicate deposition under oxic or dysoxic conditions. Vanadium and Mn values range from oxic to anoxic and sulphate-reducing to non-sulphate reducing but Mn may be anomalously low due to derivation by erosion of acidic volcanic rocks. The somewhat equivocal physical and chemical data, combined with the likely disturbing effects of penecontemporaneous volcanism, considerably weaken the case for an anoxic bottom layer in a static ocean. The presence of barite with ambient seawater 34S values in Brunswick no. 12 ore, and the abundance of sulphate in modern euxinic basin waters, make a sulphate-free layer unlikely, even if anoxic. Sulphate-bearing, low-salinity fluids mixing with seawater would lead to growth of barite-bearing chimneys and baritic rubble mounds, which are not observed. A model involving brine-pool deposition better explains the major features of the Bathurst ores. © 2007 Elsevier B.V. All rights reserved.
History
Publication title
Ore Geology ReviewsVolume
33Issue
3-4Pagination
352-360ISSN
0169-1368Department/School
School of Natural SciencesPublisher
ELSEVIER SCIENCE BV,Place of publication
AMSTERDAM, NETHERLANDSRepository Status
- Restricted