Method Development for the Systematic Separation of the <63 µm Heavy Mineral Fraction from Bulk Till Samples
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Undiscovered ore bodies have become increasingly more difficult to target, requiring new exploration techniques to pinpoint the undercover location. Sedimentary overburden in regions of intense glaciation have made exploration difficult, relying on dispersal-trains for evidence of mineralization. The focus of this study is on the silt-clay sized material as significant proportions of indicators of mineralization found in dispersal-trains could be contained within that fraction. This smaller size-fraction could improve spatial distances associated with ore body’s dispersal-trains and decrease exploration costs/time. This research examines the physical processes of mineral dispersal in the <63 µm size-fraction of till, analyzing individual fractions from 45-63, 20-45 and <20 µm. The laboratory research and field orientation case-study, was investigated by Queen’s University in collaboration with the GSC, to develop novel methods to examine and characterize the <63µm heavy mineral fraction of till. The research is broken down into 3 parts: 1) development of methods for separation of the <63µm size-fraction of HMC by experimenting with settings (mode/oscillation and flow-rate) using HydroseparatorTM technology based on different mineral densities and grain size 2) development of methods for the representative sampling of the <63 µm size-fraction of sperrylite in blank light-fraction till using controlled and real separation techniques; and 3) application of methods to real till samples collected from the southern Core Zone (Northern Québec, Labrador, Newfoundland). Environmental Scanning Electron Microscopy used in conjunction with Mineral Liberation Analysis was used to characterize the modal mineralogy of each sample. A comparative study analyzed the difference between the <63µm fraction (Queen’s University) and the >63 µm fraction (ODM). Many indicator minerals in bedrock sources are <0.25 mm and are rarely characterized in glacial sediments because of our inability to separate, visualize, and chemically analyze these small mineral grains. Using the <63 µm size-fraction, along with glacial history, dispersal-trains can be detected from distal regions aiding in exploration targeting below surface deposits. Past studies have begun to examine grains of similar size however, the approach used in this study differs from techniques previously used and could expand the usefulness of HMC for exploring mineral deposits within glaciated terrain.
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