Diamonds in Canada: Recent Advances in Exploration Methodology and Advanced Stage Assessment
Mining Rocks! CIM Toronto 2005
A review is presented of current developments in the fields of diamond prospectivity mapping, kimberlite exploration, diamond content and preservation analysis, and the advanced stage, step-wise assessment of diamond grade and value.
Since the initial discovery of the Point Lake Kimberlite in 1991, Canada has proven a fertile environment for the development of new methods in the exploration for, and delineation of, diamond deposits. Initial successes in the Lac de Gras area were based upon the application of geochemical and geophysical techniques newly derived from the exploration offices of De Beers in Southern Africa and Alrosa in Russia, such as pyrope G9/G10 Gurney plots and Mag-TEM anomaly pairings. Since then, advances in geochemistry have been made with multi-mineral assemblage geothermobarametry and its use in the delineation of Archon paleogeotherms, a more sophisticated understanding of lithospheric profiles and the role of mantle rock suites in diamond provenance, and higher standards in the sampling for, and identification of, kimberlitic indicator minerals. Likewise, geophysical advances have included the development of more refined aeromagnetic and penetrative TEM systems, reflective waveform techniques, and airborne gravity.
In the assessment of advanced stage deposits, recent CIMM guidelines for the disclosure of micro-macro diamond data have allowed for a wider dissemination of this important assessment technique and a comparative analysis tool for new discoveries. Accompanying this has come a broader awareness of the significance of sample size and diamond stone count data within staged, bulk tonnage sampling programs, and the adoption of common standards for the proper assessment of diamond grade, size distribution and value models. In addition, complex and often small, multi-facies volcaniclastic pipes, common in the main Canadian diamond fields, have necessitated new methods for comparative grade determination and reconciliation across multiple ore units.
These advances in Canada have come about not only as a result of the adaptation of existing exploration techniques to Canada’s glaciated and resistive terrains, but also because of the unique Canadian mélange of aggressive junior resource companies, an R&D oriented geophysical and mineral services community, committed, senior explorers, and academia. New exploration developments are facilitating the current boom in diamond discoveries in new, “Second Wave” areas and improving the transparency and accessibility of new projects to developers and financers.