The technique is still used as an exception rather then the rule, but it is easy to see it becoming an essential part of the exploration tool kit, just like gravity, magnetic and electromagnetic surveys.

The emergence of hard rock seismic in Australia and abroad is largely due to the efforts of Perth-based HiSeis, formed in 2009 to commercialise the breakthrough techniques developed by Curtin University’s Centre for High Definition Geophysics.

HiSeis is led by chairman and geophysicist, Dr Don Pridmore, who learnt the business of exploration under legendary Western Mining chief geologist, Roy Woodall.

It is little surprise that HiSeis developed something genuinely innovative and offering a step-change in the effectiveness of exploration efforts.

The early adopters are already running with it. More than 50 surveys have been conducted by HiSeis since 2009, and its client list includes names such as AngloGold Ashanti, Northern Star Resources, Evolution Mining, Gold Fields and Toronto-based Lundin Mining.

Of course, most of us think of seismic as an exploration tool of the oil and gas industry. It got its start in the 1920s when oil companies ran out of outcropping oil reservoirs and needed a tool that could see underground and pinpoint where drilling would most likely hit the payzone.

Almost 100 years later, mineral explorers are the ones who have run out of outcropping deposits and need new remote sensing tools.

In the past 30 years, a number of attempts were made at transferring seismic technology from oil to mineral exploration, but these failed because the survey design was basically unchanged.

HiSeis and others then started with a clean sheet of paper and looked at how best to survey mineral deposits, which typically have a complex 3D geometry over a scale of hundreds of metres, rather than flat-lying oil and gas reservoirs that stretch over many kilometres.

The other big difference is rock hardness and hence the time taken for sound energy to travel through the rocks.

Seismic energy travels two to three times faster in hard rocks compared to sedimentary layers, which has an impact on how the survey is shot, and how data is acquired and processed.

Luckily, the world also entered the digital age at about the same time as the renewed push to develop hard rock seismic.

This means the huge amounts of data collected in 3D surveys are quite easily managed and processed into subsurface pictures of stunning quality.

So how can hard rock seismic improve your chances of discovery, and how much does it cost?

A typical deployment would be to shoot a 3D block measuring a few kilometres in each dimension in an area where there is some drill data showing mineralisation.  The seismic may well image structure, alteration and/or stratigraphy depending on the in situ rock properties.

Hard rock seismic is well suited to exploration for extensions or repetitions of mineralisation associated with existing deposits, particularly at depth where other geophysical techniques have limited effectiveness.

For example, HiSeis recently completed a 3D survey over and around AngloGold Ashanti’s Geita gold mine in Tanzania, which had been actively mined by open pit but also had underground potential.

In Western Australia’s eastern goldfields, Northern Star Resources has reported great results with a 2D seismic line at the Pegasus underground mine in the Kundana belt.

Hard rock seismic can also be used as a regional greenfield exploration tool by shooting 2D lines at distances of between 10km and 20km apart.

The insights from mineral seismic surveys, when combined with an explorer’s knowledge about a target from other exploration methods, can mean big savings on drill costs and speed up discovery times.

For small, high-grade and complex deposits, hard rock seismic could easily mean the difference between discovery and failure.

HiSeis CEO Joe Dwyer said a seismic survey offered great value when compared to the costs of drilling alone to build up a subsurface picture and eventually make a discovery.

“The cost of a high resolution 3D seismic survey over an existing prospect may be equivalent to two or three deep drill holes,” he said.

“That’s the value proposition we put to our customers. If you can have a 3D cube of the geology to a resolution of 7m x 7m x 3m, and you can get that over a block 3km x 3km x 5km deep, why wouldn’t you go for it?

“The mining company can then target every drill hole off the 3D seismic image rather than applying more pattern drilling.

“Advances in seismic processing also mean that the mining company can use the 3D geological model acquired through seismic to assist in mine design, mine planning and geotechnical design.”

Dwyer said hard rock seismic would not be suited to all locations because it relied on some degree of contrast between the rocks of interest and surrounding country rocks.

However, more often than not, modern seismic has a great deal to offer and could provide the insights that compress the timeframe to discovery.