High definition exploration brings better prospects: a range of high-tech tools are now being used to aid detailed resource evaluation of mineral prospects. The result is more effective exploration throughout Africa, writes Kyran Casteel.

THE AMOUNT OF mineral resources and reserves available to a mining company underpin the value of its business for all the stakeholders in that business. That's one reason why the reporting of resource and reserve information is now rather tightly regulated in most mining countries. Frequently too, especially where the junior mining company/senior company pattern of project financing and development is adopted, more than one mining firm with contracted consultants, analytical laboratories etc will contribute to a resource's information database, making careful evaluation at the project feasibility study stage a must.

It is also important to keep in mind that the resource/technology/price relationship is dynamic since changes in product market prices, mining and/or process economics can affect the viability of exploiting deposits while or after they proceed through the various stages of exploration and evaluation. It is interesting to note in this context that a large but low-grade nickel and platinum group metals deposit in Europe which was regarded as uneconomic only four years ago will now be mined next year for treatment by a biohydrometallurgical route.

Although mineral exploration is expensive, especially the detailed core drilling phase, it is essential to do it properly, gathering all the relevant data in as much detail as possible. It is calculated that the evaluation of detailed exploration data can take up to 70 per cent of the total time spent on producing resource and reserve statements for a deposit.

Unless the mineral deposit is unusually rich in grade and simple in mineralogy, successful competitive exploitation will depend on a full understanding of the implications of geology and geometallurgy for mining and processing. This, as Anglo American puts it, is the foundation of the value chain--and this is why the company not only spends a large amount of money acquiring geodata but also constantly assesses techniques for extracting more information from this data.

The airborne magnetic SQUID

Anglo Platinum and De Beers were both initial supporters of the development of a revolutionary technology for airborne magnetic exploration. This is the Superconducting Quantum Interference Device (SQUID) manufactured by the Institute of Physical High Technology which is located at Jena in Germany. Subsequently AngloGold and the Anglo Technical Division have both backed the project.

The niobium devices become superconductive at approximately--270[degrees]C and six of them are built into a cryostat which in turn is built into a cylinder together with an Inertial Measuring Unit, which is a position measuring device similar to GPS. The cylinder is suspended from a survey helicopter and data is fed to a laptop computer in the aircraft. After compensation for flight movements the magnetic data is interpreted by a geophysicist who creates an image recording magnetic intensities and gradients in the magnetic field.

One application for Anglo Platinum is the identification of dykes and iron-rich ultramafic replacement pegmatoids within the mining area that can be mining hazards, causing falls of ground if they are not taken into account. In diamond exploration the SQUIDs can detect kimberlite structures. Anglo says that tests over the past three years have advanced the functionality of the technology and initial teething problems are being eliminated. Spectem Air was selected as the preferred operator to conduct surveys for the participating Business Units and ordered the first commercialised SQUID from the Institute for delivery in the third quarter of 2007.

More powerful modelling

One tool that Anglo's Geosciences Resource Group (GRG) in South Africa has started using is the Gocad 3D modelling software package distributed by Mira Geoscience. Gocad's major advantage is its ability to integrate various data types generated in the mining industry, including geological, geophysical, geochemical, hydrogeological, rock mechanical and metallurgical information. Consequently staff from various disciplines can share one quantitatively-consistent and visually-comprehensible model.

According to the GRG, Gocad also arguably provides the industry's most advanced geological surface- and volume-modelling tools, allowing construction of large-scale geological models direct from primary data. Models can also be imported and quantitatively assessed by incorporating geophysical and other datasets. The software can produce structural, rock mechanical and uncertainty models fairly simply, either manually or by using predefined work flows.

The workflows can be fully audited and they create an HTML document recording all the steps taken. Because Gocad is a true topological 3D modelling environment it can query all the integrated data in true 3D space using GIS functionality. This allows the user to test the models against the data in order to reveal and characterise relationships and define targets based on complex criteria.

For example, a deposit block model can be analysed to see if there is a correlation between ore grade and fault proximity. Gocad is also one of the few commercially available 3D packages able to accommodate the 3D seismic data acquired for Anglo Platinum and allows the GRG to integrate borehole geophysics and borehole radar data as well.

Working with Mira, the GRG is developing Hazmap, a tool designed to flag potential hazards in the open pit or underground mining environments. The software automatically computes a hazard index, highlighting areas that are potentially unstable. Initially started with AngloGold Ashanti, Hazmap is being modified for use in coal and platinum mines.

More powerful drill rig suppliers

The consolidation process that created two main worldwide suppliers of both surface and underground development and production drilling rigs has now taken a fairly firm hold of the exploration drilling market as well. And the same two groups, Atlas Copco and Sandvik, are the key players.

It is some time since Atlas Copco decided to build on the very successful Craelius operation, building exploration core drilling equipment near Stockholm, Sweden, by acquiring JKS Boyles in Canada and elsewhere.

Further purchases followed, together with expansions in other geotechnical areas. Last year Sandvik decided to compete in this area too, buying Australian companies UDR and SDS, which also operates in Africa. Sandvik has also acquired Hagby, Swedish manufacturer of the Onram core drilling rig range. Mineral Exploration is now one of Sandvik's five mining and construction business segments, albeit the smallest in earnings terms at present.