Volatile-element signatures of volcanogenic massive sulfide deposits in the Bathurst mining camp, New Brunswick, Canada
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Date
2017
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University of New Brunswick
Abstract
Presented here is a comprehensive study of volatile-element signatures from massive sulfide deposits of the Bathurst Mining Camp (BMC), Canada. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) methods were developed and applied to measure As, Bi, Cd, Hg, In, Ga, Ge, Sb, Se, Sn, Te, and Tl in sulfides (pyrite, sphalerite, galena, chalcopyrite, pyrrhotite, arsenopyrite, and tetrahedrite/tennantite) and phyllosilicates (white mica, chlorite, and biotite). In addition, LA-ICP-MS analyses yielded concentrations of unpublished volatile elements in standards including Hg = 0.46 ppm and Te = 296 ppm in NIST610 (n = 245), Tl = 69 ppm in MASS-1 (n = 232), and Hg = 4.57 ppm and Te = 233 ppm in GSE-1G (n = 33).
Pyrite from the BMC displays extensive textural arrays, which are categorized in two main types of pre-deformation and deformation textures. Texturally-distinct pyrite assists fabricating the evolutionary history of pyrite and consequently the massive sulfide deposits of the BMC. Most forms of pyrite from the BMC are arsenian, containing up to 7.3 wt. % As, as well as significant abundances of Tl, Sb, Sn, Bi, Ag, and Se. The examined sulfide minerals accommodate volatile elements to different extents. The integrated LA-ICP-MS data of all sulfides provide a means of differentiating the hydrothermal sulfide facies. Comparison the volatile-element budget of the examined minerals within host rocks demonstrates that white mica represents the most highly concentrated source of Tl, Sn, Hg, In, as well as Ba. On the other hand, sulfide minerals host the main concentration of Bi, As, Sb, Se, Cd, Pb, Ni, Cu, and Co. Chlorite, and to a lesser degree white mica, is distinctly enriched in Zn, relative to sulfide minerals (except sphalerite) of the host rocks.
The abundances and compositional variation of sulfides, in particular, pyrite, chlorite, and white mica in the host rocks of the known VMS deposits investigated in the present study offer potential micro-chemical vectoring tools. The elevated concentration of volatile elements in sulfide minerals, in particular pyrite, and chlorite and white mica, occurred proximal to ore horizons as well as the subtle occurrence of volatile elements in white mica and pyrite distal to ore horizon present the potential footprint of buried sulfides.