Discovering mineral deposits through till: "mythbusting" the silver-bullet
Theatre 1 Capitol Theatres
2pm Wednesday 15 November 2017
Dr. Peter Winterburn
NSERC/AcmeLabs/Bureau Veritas Minerals Industrial Research Chair in Exploration Geochemistry
MDRU - EOAS - The University of British Columbia
Canada, as with many northern latitude environments, presents a challenge to mineral exploration in having many prospective mineral belts covered with a blanket of glacial products, including till, alluvium, organic veneers and post-glacial re-worked materials. Whilst indicator mineral trains have proved highly successful at identifying broad target areas, the pre-drilling surface evaluation of individual discrete targets remains an obstacle to effective and efficient mineral exploration. Ongoing research at the University of British Columbia over a range of mineralisation styles and utilizing commercial inorganic and organic geochemical techniques of soil and vegetation coupled with landscape mapping, has identified distinct pathways by which geochemical responses can develop on the land surface without invoking complex processes. Two sites in contrasting settings: the DO18 kimberlite, Northwest Territories, and the Highmont South deposit, Highland Valley Copper Mine, Central BC, will demonstrate that glacial processes, groundwater movement and vegetation are the principal ingredients in anomaly formation directly above mineralisation. Ongoing experiments with low-concentration blends of ore and till have demonstrated that geochemical and bacterial responses change rapidly in the presence of mineralisation and are likely directly related to the production of organic signatures.
At the DO-18 kimberlite, concealed by 10m of till, a distinct low-level Nb-Ni-Cr-Mg-organic response is identified directly over the kimberlite and tails off in the down-ice direction. The response dominantly resides with resistant mineral phases, and although subtle (6ppm Nb, 45ppm Cr, 20ppm Ni), can be identified by portable XRF. A portion of the anomaly is concealed by post-glacial alluvial processes and demonstrates the value of surface material mapping. The response was generated through ice transported clastic material in the till plume being locally enhanced by frost boil transport to the surface.
At Highmont South, where ice movement parallels the strike of an elongate mineralised body buried under 5-10m of till; a tight Cu (>360ppm) – Mo (>10ppm) – Ag (>0.054ppm) – Bi (>0.24ppm) signature is present directly over and down-ice of mineralisation within a broader regional anomaly from Highland Valley. The Mo surface response has been enhanced through vegetation (lodgepole pine) cycling, which has significantly enriched Mo (7-19ppm) in needles directly over mineralisation. Geochemical responses are also evident directly over major structures, however are limited to elements soluble in the ambient conditions. Organic signatures are present over both mineralisation and cross-cutting structures.
At both locations, conventional exploration geochemical techniques including fp-XRF, coupled with a clear knowledge of the glacial and post-glacial history, would have identified the presence of mineralisation as distinct drill targets without the necessity to utilize poorly understood selective extraction, proprietary or other commercial “Silver-bullet” techniques.
Dr Peter Winterburn is an Exploration Geochemist with over 25 years of experience in industry prior to joining the Mineral Deposit Research Unit as a professor of Exploration Geochemistry at the University of British Columbia in 2014.
Peter was previously employed by Anglo American plc as their Regional Geochemist in Africa and subsequently in South America, based out of Santiago, Chile following which he held the post of Chief Geochemist: Global Exploration with Vale based out of Toronto. Peter has worked in over 60 countries representing a range of environments from tropical to arctic to arid deserts in both mountainous and subdued terrains.
Peter is currently the NSERC/AcmeLabs/Bureau Veritas Minerals Research Chair in Exploration Geochemistry at MDRU, where he directs a program aimed at answering many of the questions and providing practical applications with respect to the discovery of minerals deposits through transported overburden. Peter has active research projects and students in British Columbia, the Northwest Territories, Colombia and Chile, where he is working on a dominant theme of understanding the processes of anomaly generation and anomaly retention in the surface soils. This research includes themes as diverse as regolith mapping, surface organic and inorganic geochemistry, soil mineralogy, extractive geochemistry and microbial genomics.