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

Abstract

Exploration under thick glacial sediment cover is an important facet of modern mineral exploration in Canada and northern Europe. Till heavy mineral concentrate (HMC) indicator mineral methods are well established in exploration for diamonds, gold, and base metals in glaciated terrain. Traditional methods rely on visual examination of >250 µm HMC material. This study applies mineral liberation analysis (MLA) to investigate the finer (<250 µm) fraction of till HMC. Automated mineralogy (e.g., MLA) of finer material allows for the rapid collection of precise compositional and morphological data from a large number (10,000–100,000) of heavy mineral grains in a single sample. The Sisson W-Mo deposit has a previously documented dispersal train containing the ore minerals scheelite, wolframite, and molybdenite, along with sulfide and other accessory minerals, and was used as a test site for this study. Wolframite is identified in till samples up to 10 km down ice, whereas in previous work on the coarse fraction of till it was only identified directly overlying mineralization. Chalcopyrite and pyrite are found up to 10 km down ice, an increase over 2.5 and 5 km, respectively, achieved in previous work on the coarse fraction of the same HMC. Galena, sphalerite, arsenopyrite, and pyrrhotite are also found up to 10 km down ice after only being identified immediately overlying mineralization using the >250 µm fraction of HMC. Many of these sulfide grains are present only as inclusions in more chemically and robust minerals and would not be identified using optical methods. The extension of the wolframite dispersal train highlights the ability of MLA to identify minerals that lack distinguishing physical characteristics to aid visual identification.

Stream Sediment Indicator Mineral Signatures of the Casino Porphyry Cu-Au-Mo Deposit, Yukon, Canada

“…Automated SEM-based methods (e.g., mineral liberation analysis, quantitative evaluation of materials by SEM, TES-CAN integrated mineral analyzer [TIMA-X]) are useful for detecting indicator minerals in the fine (<0.25 mm) fraction of heavy mineral concentrates of sediment samples that cannot be seen because they are too small to be observed using a binocular microscope or occur as inclusions within other minerals (Lehtonen et al, 2015;Lougheed et al, 2020Lougheed et al, , 2021Layton-Matthews and McClenaghan, 2022;Kelley et al, 2022). Automated SEM-based methods are not yet routinely applied to heavy mineral samples in industry or government surveys.…”

Interface Sampling and Indicator Minerals for Detecting the Footprint of the Lancefield North Gold Deposit under the Permian Glacial Cover in Western Australia

“…Indicator mineral methods have been thoroughly integrated into mineral exploration protocols in late Pleistocene glaciated terrains in Canada, the USA, and Fennoscandia [15][16][17][18][19][20][21]. Subglacial erosion of mineralization can produce a dispersal train of metal-rich debris that resembles the primary composition of the bedrock source [18,[21][22][23].…”