Indicator mineral and geochemical signatures associated with the Sisson W–Mo deposit, New Brunswick, Canada

Abstract

An indicator mineral and geochemical case study was carried out around the Sisson W–Mo deposit to test modern indicator mineral and analytical methods and document glacial and fluvial dispersal from a significant W–Mo source. Indicator minerals in the 0.25 – 2.0 mm non-ferromagnetic heavy mineral fraction of till and stream sediments include the primary ore minerals scheelite, wolframite and molybdenite, as well as chalcopyrite, joseite, native Bi, bismutite, bismuthinite, galena, sphalerite, arsenopyrite, pyrrhotite and pyrite. Indicator minerals in c. 12 – 14 kg samples define glacial dispersal of at least 10 km down ice (SE) of the deposit and fluvial dispersal at least 4 km downstream. The presence of very coarse (0.5 – 2.0 mm) indicator minerals in till and stream sediments marks proximity (<1 km) to the mineralized source. Indicator elements for the deposit in the <0.063 mm fraction of till, the <0.177 mm fraction of stream sediments, and in stream water include W and Mo, and various combinations of pathfinder elements Ag, As, Bi, Cd, Cu, In, Pb, Te and Zn. This list of elements is more extensive than previously identified for the Sisson deposit or other studies around W mineralization in glaciated terrain. The study demonstrates that indicator mineral methods, so well known for diamond and gold exploration, have a broader application that includes W–Mo exploration.

Exploration Potential of Fine-Fraction Heavy Mineral Concentrates from Till Using Automated Mineralogy: A Case Study from the Izok Lake Cu–Zn–Pb–Ag VMS Deposit, Nunavut, Canada

“…Future work should investigate the use of trace-element compositional analysis of epidote grains to assess terrane fertility, after the work of Plouffe et al [8] on porphyry systems. Fe-oxide minerals can indicate the incorporation of gossanous material into till [72] or the weathering of sulfide grains during transport or following deposition. Not all gossans will be found with associated mineralized sulfide bodies (i.e., the WIZ showing) but the fact that they indicate that a mineralized system existed at one point in time makes them an important exploration target.…”

Automated Indicator Mineral Analysis of Fine-Grained Till Associated with the Sisson W-Mo Deposit, New Brunswick, Canada

“…Density concentration of samples was carried out using a combination of wet screening and shaking table, followed by heavy liquid separation (methyl iodide) at 3.2 SG, acid-washing, and ferromagnetic separation to produce a coarse (250-2000 µm), nonferromagnetic HMC (>3.2 SG) fraction. This coarse fraction was visually examined, and indicator minerals were counted, with results reported by McClenaghan et al [40,41]. The archived by-product of sample processing was the nonferromagnetic, <250 µm HMC fraction that is the basis of our study.…”

“…The train was defined by various combinations of W, Mo, As, Bi, Cu, F, Pb, and Sn contents in several different size fractions of till matrix [20,33,[35][36][37]. Till indicator mineral studies carried out by McClenaghan et al [20,[38][39][40][41] combined with stream-sediment indicator mineral data [21,41] indicate that the 250-2000 µm HMC fraction of sediment contains the ore minerals scheelite, wolframite, and molybdenite, along with sulfide and Bi-bearing minerals. Scheelite was found in till samples collected at least 10 km down ice of mineralization, whereas the other ore minerals were only found in till samples immediately overlying mineralization.…”

“…Five till samples collected in 2011 by McClenaghan et al [38,[40][41][42] were chosen for this study based on their locations relative to mineralization (Figure 1) and the reported indicator mineral content in the 250 to 2000 µm HMC fraction. Sample 11-MPB-520 is the farthest up ice till sample available (4 km from mineralization) and was chosen to represent background values compared to down ice sample locations.…”

“…Samples 11-MPB-525 and 11-MPB-539 (4.3 and 10 km down ice of mineralization, respectively) represent proximal and distal down ice samples, respectively, within the known glacial dispersal train. Previous work identified the ore mineral scheelite in the coarse (250-2000 µm) HMC fraction of till from each of these overlying and down ice sites [38,[40][41][42].…”