|The mathematical functions behind implicit modelling have been around for some time. It is the relatively recent advances in computing power, however, that have helped unlock their potential for commercial application | Courtesy of ARANZ Geo
Integra Gold’s Triangle Zone deposit is structurally complex, a common trait to the many mines and gold deposits in Quebec’s Abitibi gold district. When the company continued a drilling program on the site in early 2015 it found one hidden structural trend, which changed the resource estimate for the better. The site’s Indicated Resources increased by 21 per cent to 627,810 ounces of gold, with an average grade of 7.37 grams per tonne, thanks to the discovery of “steeply dipping ‘C’ structures.”
The company detected that structural trend with the help of Leapfrog, 3D implicit modelling software made by ARANZ Geo. The software, and others based on the same principles, can create accurate, detailed 3D models that highlight the particular challenges and potential of an ore body in a fraction of the time and for a fraction of the cost of models done using explicit modelling, the traditional approach.
Traditional explicit modelling methods require geologists to input the data and connect the points by hand. Frank Bilki, technical product manager at software company Micromine, compares this to making a computer model of a loaf of bread by building a 2D model of each slice and then combining all the slices. This kind of technique could take weeks or months, depending on the size and complexity of the deposit, but it had been the standard for modelling – until implicit modelling became available.
|A stratigraphic model built using Leapfrog | Courtesy of ARANZ Geo
3D in real time
The algorithms Leapfrog and Micromine use for implicit modelling are based on radial basis functions (RBFs). These functions help interpolate the data collected during drilling programs. They do this by identifying trends in the data set, based on parameters set by the geologist, and by creating surfaces that honour those trends. Implicit modelling provides the flexibility to model many types of deposits, including complex vein systems, stratiform and porphyry deposits.
As new information and data become available the model is dynamically adjusted, all in real time. Geologists can tweak the model to examine multiple hypotheses; for example, making it more or less conservative to aid decision making. “In an exploration program when you’re spending as much money as you’re spending – and we’ve got between five and 10 drill rigs running – you need to be able to make changes on the fly to your drill patterns,” said George Salamis, a geologist and chairman of Integra Gold. “The quicker you have the data … the more efficient you’re going to be drilling and the less money you’re going to spend. It’s pretty simple.” Better yet, implicit modelling software can take models and present them with 3D contours, allowing geologists to quickly spot trends or structures. “You really need to see things in 3D to fully understand them,” said Salamis. “It’s especially key in these structurally controlled deposits that you see in Quebec and Ontario.”
Before miners got their hands on the software, ARANZ first applied implicit modelling to medicine and movies. The company’s techniques led to a hand-held portable laser scanner, which has been used to make prosthetics as well as some of the computer animations in the Lord of the Rings trilogy and the Star Wars prequels.
Leapfrog’s program has matured over the past decade as a result of working closely with the industry, according to its director of product and innovation Tim Schurr. “We pioneered this method of modelling in the mining industry in 2003, and it definitely caught people’s attention. After more than a decade of refinement the Leapfrog engine you see today, and the models you see today, are light years ahead,” he said.
Computers have been evolving as well. “The implicit modelling algorithm is actually quite old, but computers were simply unable to create an implicit model until they became powerful enough to handle the calculation,” said Micromine’s Bilki. “Only in the last decade or so have we seen computers fast enough to do so.”
Though ARANZ has established itself as the leading implicit modeller in the geology market over the past decade, the company is now facing new competition; Micromine first included implicit modelling in their 2013 software release.
“We actually love the way that others [like Micromine] are embracing implicit modelling. It’s really highlighting how game changing, effective and important it is,” Schurr said.
Integra has used implicit modelling software on-site for several years, Salamis said, ever since the company hired new employees who had Leapfrog experience from their previous work with major mining companies.
“Before, when we weren’t using Leapfrog as much as we are now, getting the data into a quick 3D visualization module took time. Now, with our more intensive use of Leapfrog, the guys and gals who know how to use it pretty well can visualize things on the fly,” he said.
However, implicit modelling has faced challenges in the past and some people remain unconvinced. Users need to be familiar with the software in order to get good results, said Peter Gleeson, a consultant with SRK. “It really does take about a year to become proficient,” he noted. “And you’ve got to understand your geology, first and foremost. It’s not a black box. You’ve got to have a good geologist behind the computer.”
Bilki echoed that users must understand what went into an implicit model if the results are to be trusted.
“[Implicit modelling] is simply another tool in the geologists’ toolkit, to be used under the appropriate conditions,” he said. “Some ore bodies are ideally suited to an implicit modelling approach, others are best modelled using traditional interpretation-and-wireframing or stratigraphic methods.”
|The software uses radial basis functions to generate models such as grade shells using drill hole data | Courtesy of Micromine
Some regulatory steps have also been taken to recognize implicit modelling’s potential. In 2014, the technique was included in the AusIMM Monograph 30, which gives a guide to best practices for mineral resource and ore reserve estimation. Although Schurr noted that some companies have begun to use implicit modelling techniques for reporting standards-compliant resource estimations and classifications, the technique has not yet entered the mainstream.
Gleeson is optimistic. “NI 43-101 does not stipulate the method you use. So long as you can justify what you’ve done, and show that it’s geologically realistic, there is no reason not to use it,” he said.
Geologists may soon be able to bring their implicit models out of the office and into the field. In September, ARANZ Geo announced a beta version of an augmented reality tool was in the field with testers. The tool should allow geologists to superimpose their models on the actual topography of the site. A release date, at this point, has not been announced.
Feedback will be key, the company stated in the release, and Schurr noted that this is the way the software has always developed. “This implicit modelling engine that we’ve built has been developed carefully, through a lot of feedback from our customers.”
Salamis said that he would love to see conditional simulations, providing what-if scenarios that could be used to determine if an ore body is economically viable. “If I was to drill 10 holes, 100 metres away from the ore body and hit this grade or this width, what does that do to the economics of this deposit? Right now, we don’t have the capability to do that. We basically have to go back from scratch and redo resource estimates to get that answer,” he explained.
But that does not mean that he is not happy with the software’s current capabilities. In fact, the company has a lot of faith in the software – so much so that they have selected Leapfrog as the 3D modelling partner for their Gold Rush Challenge. Entrants are given a Leapfrog licence for the duration of the competition to help them find new, potentially profitable trends at their Sigma-Lamaque project. This competition allows the Integra geologists to focus more on the Triangle Zone.
As implicit modelling itself becomes more established, companies like Leapfrog and Micromine continue to develop new, cutting-edge applications. Both Leapfrog and Micromine have new versions of their software on the market or nearing release; Micromine’s should be launched in the second quarter of 2016 and a new version of Leapfrog Geo was made available in November with new tools for data analysis and geologists working on stratified or layered geologies.