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March 12, 2013
On Tuesday March 26, 2013 the TGDG will host a selection of speakers for a mini-symposium at Hart House on ‘Laterites or Laterwrongs: Making the Pieces Fit’. Speakers include Ravi Anand (CSIRO), Peter Winterbourne (Vale), and Ron Schonewille (Xstrata)...
March 11, 2013
Hailing from industry, government and academia, high profile Australian and internationally-based researchers will join the CET fortnightly to share their experience on a wide variety of geoscience topics.These seminars are FREE and all interested Geologists are welcome to attend...
February 25, 2013Is regulation robbing exploration properties of their worth?
You can’t get chickens if you don’t allow the eggs to develop. Joe Hinzer, president of geological consulting firm Watts, Griffiths and McOuat (WGM), uses this analogy to illustrate how many early-stage exploration projects are being stifled by current mineral valuation regulations before they have a shot at becoming mines...
February 04, 2013
It has been a busy 24 hours as the Association for Mineral Exploration British Columbia (AME BC) kicked off its Mineral Exploration Roundup 2013...
January 29, 2013Where do I meet the geologists of Africa?
Africa is more than 20 per cent of the world’s land area, is home to 15 per cent of human population but still earns its label as the Dark Continent through generating only 2 per cent of the world’s electricity. Where can you find the geologists exploring this sleeping giant with its inevitable future in the resources sector?
January 28, 2013
As exploration programs focus on remote and concealed targets, the ability to recognize large ore-forming systems – from the most distal margins to high-grade cores – becomes increasingly important. Efforts are therefore under way to generate sophisticated “footprint” or “signature” models of high-value deposits.
December 2, 2012
The December 4th Greenland Day, taking place in Perth, will feature industry and geoscience experts from across the globe, discussing Greenland’s burgeoning exploration opportunities and recent research advances...
November 1, 2012
Some of the sector's leading minds will be looking into their crystal balls on November 8th, trying to summon a picture of what the future might hold for exploration and mining in Canada...
September 11, 2012
Brazilian state-run energy giant Petroleo Brasileiro, or Petrobras, said Tuesday that it had started oil production at the Baleia Azul presalt field in the offshore Campos Basin...
September 11, 2012
Barrick Gold CEO Jamie Sokalsky speaks with Carl Quintanilla on CNBC about Barrick's strategy to drive shareholder value...
September 10, 2012
The tie between energy supply, population, and the economy goes back to the hunter-gatherer period...
July 12, 2012
A massive two thirds of Western Australia remains unexplored for minerals and geologists say the territory presents huge potential...
July 12, 2012
Shale and other unconventional resources are being called the biggest game changer in a generation - and as land and other costs escalate, the industry continues to apply lessons gleaned from the early successes...
July 11, 2012
In this exclusive interview with Professor David Thiel, Director at the Centre for Wireless Monitoring and Applications at Griffith University, he discusses how electromagnetic geophysics can help those who are conducting a feasibility study and opens up on the real cost benefits of this technology...
July 11, 2012
Improved security has started to open up new areas for mineral exploration in Latin America....
by Dan Zlotnikov on June 5, 2012 applied
Application of aeromagnetic structural analysis techniques for greenfields gold exploration.
Ground selection is a crucial stage in every greenfields exploration program. This process frequently relies on data acquired from State or Federal Government organizations seeking to encourage exploration activity; many jurisdictions offer their databases to the public at zero or very low cost.
The data thus acquired can come in a variety of forms, but one type commonly available is the result of aeromagnetic surveys. Conducted from the air and able to “see” through vegetation and snow cover, these surveys can reach remote areas at a relatively low cost. Aeromagnetic surveys are particularly beneficial for gold exploration because geology that favours the formation of gold deposits is frequently also associated with changes in rock magnetism. This makes aeromagnetic data particularly useful to gold explorers, but analysis of considerate volume of magnetic data requires significant time and effort in looking for areas of interest.
The analysis of the data is usually performed manually, with a geologist reviewing the maps and seeking to identify potentially gold-bearing areas. When the data cover millions of square kilometres of surveyed land, the process is not only complex but also extremely tedious. Fortunately, tedious, quantitative analysis of large volumes of data is a prime candidate for automation.
Automating the process is exactly what Eun-Jung Holden, a co-leader of geophysics and image analysis and Associate Professor at the Centre for Exploration Targeting (CET) within the University of Western Australia and her colleagues aimed to do. Their paper Identifying structural complexity in aeromagnetic data: An image analysis approach to greenfields gold exploration, published in Ore Geology Reviews in 2012, details the process and the results of two field applications of the CET Grid Analysis techniques.
The study targeted Archean orogenic-gold deposits formed during the Archean eon, some 3.8 to 2.5 billion years ago. These deposits are located in areas where tectonic plate activity during that period produced mountains. A side-effect of the tectonic upheaval was to break up the solid rock and form channels and cavities into which gold-bearing fluid could rise. Although the fluids are long gone, the gold remains. Today, Archean orogenic deposits represent one of the most important types of gold mineralization, accounting for roughly 20% of global gold production.
Besides being a major source for gold, Archean orogenic-type deposits are also excellent targets for magnetic surveying. The same fluid that brought up gold also served to remove magnetite ores in the vicinity, and on aeromagnetic data, the fluid channels show up as distinct lines or lineaments of diminished magnetism.
Algorithms intended to automate the search for such linear features have been proposed before; the innovation this study advances lies in the combination of an automated search for lineaments and for what is known as “structural complexity.” Simply put, the more lineament contacts there are in vicinity and less parallel they are to each other, the more structurally complex an area is considered to be. Such areas have been known to correlate with the location of gold deposits, making areas of higher complexity that much more attractive for further investigation.
The CET team applied their technique to two areas known for Archean orogenic gold discoveries in the Eastern Goldfields Superterrane of Western Australia and in the Abitibi greenstone belt in Ontario, Canada. Both are mature, gold-producing areas with many known deposits, which allowed the researchers to compare the results of the automated analysis with existing maps of deposits.
The automated approach has shown itself well in the testing. “Our experimental results demonstrate there is a high correlation between known mineralisation and the regions of structural complexity that are generated by the proposed method,” Holden and her co-authors conclude. They also point out that the same analysis technique can be applied to other inputs, such as traces from a digital geologic map and for other types of deposits.
Holden acknowledges a number of limitations of the technique. The approach cannot identify the time of formation of a particular lineament, ranking ones that formed at the same time as gold mineralization and ones that appeared after (and are not helpful to mineral explorers). The paper also points out, “Mineral exploration decisions are always based on a combined analysis of multiple datasets, typically geology, geophysics, geochemistry and satellite remote sensing. Our structural complexity maps should complement the other datasets used in the exploration decision-making process.”
Source: Holden, E.-J., et al., Identifying structural complexity in aeromagnetic data: An image analysis approach to greenfields gold exploration, Ore Geol. Rev. (2012), doi:10.1016/j.oregeorev.2011.11.002.