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Why did you drill there?

You've put your work in; gathered soil, grab, chip and trench samples; compiled the historical and newly acquired data; acquired financing; hired contractors; and marked "X's" on the maps where you are going to drill. But how do you know you have picked the right spots?

The pressure to drill can be immense and come from varying sources such as investors, management and shareholders. Drill results can make, or break, a project very quickly. It's shocking how much a project's success relies on a small, 3 to 6 centimetres wide section of rock out of many square kilometres within a mineral claim.

Let's take a look at how we decide where to drill ...

Wastell and friends (2010) took a look at the decision making process in mineral exploration and the quality of their outcomes. They found that, although the cohort of 94 experts had access to the same standardized scientific data, they returned with widely varying mineral endowment estimates. In addition, further investigative techniques recommended by the experts were very diverse indicating, to the researchers, that mineral exploration does not have a well-established and uniform method for developing a mineral project. They also found that there was not a significant relationship between the probability estimates of finding an economic mineral deposit and the commitment to spend more money on exploration: for example, irrespective of the number of prior failures to produce good drill results, given a further $200,000, the experts chose to drill more holes.

Alternatively, Kreuzer and his colleagues (2015), compared prospectivity modelling results with past exploration data and expenditures within the Macquarie Arc in eastern Australia. They found the region to be highly successful with a 5 % chance of an exploration licence progressing into a mining operation, however, this success was achieved by only a few companies. They also noted that a large majority of exploration investment was targeted outside the main mining areas and, based on the authors' prospectivity mapping, these areas had the lowest geological potential (possibly a case of proximity to success = a higher chance of success): approximately 72 % of the exploration licences were located on poorly prospective ground. Staking the least prospective areas likely led to the results that 56 % of the licences did not record any drilling activity within the time period with 24 % of the licences drilling prior to their third year of tenure. The authors believe that past exploration of the Macquarie Arc did not efficiently test all the prospective areas and that the region has not yet matured with respect to its exploration potential.

Since 2011, there has been a marked rise in exploration expenditures and a significant decrease in the number of major discoveries. It is thought that the recent changes are due to the extra costs associated with exploration in remote locations, the need to explore deeper underground and the apparent lack of easy-to-find targets. A change in how we model deposits, explore and where to drill appears necessary to try to control the costs of discovery.

How do we increase our likelihood of getting good drill results?

1. Interpret the regional data.

  • Look beyond the "highs" and include pathfinder anomalies.

  • Use updated deposit models based on regional mines.

2. Do historical compilations.

  • Look for alternate commodities and pathfinder halos.

  • Update the model.

3. Hire and work with prospectors.

  • Prospectors will have done a lot of the leg work already if they are optioning off a claim.

  • Geologists tend to have a more systematic approach compared to prospectors who are more focused on finding mineralized zones (both are needed to develop a property).

4. Invest in newer technology and methods.

  • Utilize hand-held technology for quicker results to direct current activities: XRF metal analysers, multi- and hyper-spectral radiometers, physical property scanners (magnetic susceptibility, conductivity and density), and core drills for outcrop sampling

  • Skid-mounted rotary-percussion drilling for mini-bulk sampling

  • Alternative sampling: vegetation, soil-gas, indicator minerals, etc.

5. Build a diverse team of specialists to find the not-so-obvious characteristics of mineralization and encourage communication.

  • Include geologists, geophysicists, geochemists, geostatisticians and data scientists.

  • Collaborate with universities.

About the Author:

Dr. Diana Benz has over 20 years of experience working in the mineral exploration industry searching for diamonds and metals in a range of roles: from heavy minerals lab technician to till sampler, rig geologist, project manager and business owner. She has a Bachelor of Science in General Biology, a Master of Science in Earth Sciences researching diamond indicator mineral geochemistry and a Ph.D. in Natural Resources and Environmental Studies researching geochemical multivariate statistical analysis techniques for use in interpreting biogeochemical data for mineral exploration. Diana has conducted field work in Canada (BC, NWT, YT and ON) as well as in Greenland. She has also been involved, remotely through a BC-based office, on mineral exploration projects located in South America, Africa, Eurasia, Australia and the Middle East. Currently, Diana is the owner of Takom Exploration Ltd., a small geological and environmental consulting firm focused on metal exploration in BC and the Yukon.

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