|Résumé||(disponible en anglais seulement)|
During the Geological Survey of Canada's (GSC) Targeted Geoscience Initiative (TGI-4; 2010-2015), GSC and the New Brunswick Department of Energy and Mines
(NBDEM) conducted indicator mineral case studies around the Sisson W-Mo and the Mount Pleasant Sn-W-Mo-Bi-In polymetallic deposits in New Brunswick. The objective is to document glacial dispersal patterns of W, Mo, Sn, and In-bearing indicator
minerals and matrix geochemical signatures in till at varying distances down-ice of the deposits, in support of exploration in New Brunswick and other glaciated terrains. This is the first study to document glacial dispersal of W-bearing minerals
around a significant W deposit.
At Sisson, 3 tills are present: Illinoian Northumberland till, Early-Middle Wisconsinan Caledonia till, and the geochemically barren, Younger Dryas, Collins Pond till. This presented sampling challenges as the tills
are deposited by ice flows from different source areas and are geochemically distinct but not easy to distinguish. At Sisson, 79 bulk till samples were collected up-ice, overlying, and up to 14 km down-ice (SE) of the deposit. The distribution of
sample sites was guided by previous sampling by Kidd Creek Mines and the NBDEM. Stream water, silt, and bulk samples were collected at 16 sites at Sisson to characterize scheelite abundance, size, and shape for comparison with grains in the till. At
the Adex-owned Mount Pleasant deposit, 22 bulk till samples were collected. Here, sampling was guided by previous work conducted by N. Szabo (University of New Brunswick) and the NBDEM.
Till sampling was optimized by first collecting 200 g till
samples (61 at Sisson and 50 at Mount Pleasant) and determination of W, Mo, Sn, Bi, Sn, and Cu concentrations, using a portable XRF (pXRF) spectrometer. At Sisson, anomalous pXRF concentrations match previously known NBDEM anomalies in the glacial
dispersal train extending 14 km to the SE, and correlate well with subsequent borate fusion and aqua regia/ICP-MS analyses of the <0.063 mm fraction of till (up to 815 ppm W, 65 ppm Mo, and 978 ppm Cu). Till, stream, and a suite of bedrock samples
have been processed to produce heavy mineral concentrates for assessment of indicator minerals and to characterize the indicator mineral signature of each deposit. Scheelite is abundant in both deposits, and a significant indicator mineral in till
down-ice. Other indicator minerals of the Sisson deposit include molybdenite, chalcopyrite, wolframite, Bi minerals, sphalerite, and galena. Cassiterite, topaz, beudantite, anglesite, and wolframite are indicators of the Mount Pleasant