When you’re trying to extend the life of a mining project, and all surface expression has already been mined: mining companies need a survey that focuses drill targets with less risk than an airborne survey. Peace of mind for mineral exploration companies like New Nadina comes from seeing absolute data (collected at depths greater than 500 meters).
Here’s why you can use airborne surveys to identify features of interest, but not to specify drill targets:
At New Nadina’s Silver Queen Property, Geotech’s ZTEM went over the property. But the airborne Tipper MT survey, while quick and affordable, has limitations.
“An airborne system such as ZTEM uses MT Tipper to map channeled currents that may be related to strong conductors and fault-structures so that exploration can be loosely guided over large regions; but it is prudent to collect more before incurring the expense of unnecessary drilling. Thus, Titan 24 MT resistivity provides more focus, better accuracy, and deeper investigation for more robust drill targets,” says Roger Sharpe, V.P. of Research and Development at Quantec. (And 3 ways to decrease risk in mineral exploration).
3 Reasons Why Airborne Surveys Are Unable To Pinpoint Deep Drill Targets:
- Ratio Data vs. Absolute Data: Airborne tipper MT surveys do not relay absolute resistivity; they are limited to measuring a ratio of components at flight speed. Shot from a moving platform, you have one frame (a moving coil) to collect data; and because you are constantly moving, you cannot check (and double check) the results for accuracy.
A ground geophysical survey like Titan 24 (orOrion 3D using 3D technology) gives an absolute resistivity parameter (formulated from the collection of more data) to pinpoint drill targets. The multiple, independent receivers also have sensitivity control, which means Titan 24’s crew can wait for the best noise-free report from the ground-based geophysical system giving rise to more precise interpretations.
- Limited Range of Frequencies vs. Full Range of Frequencies: Airborne surveys are limited to a frequency range of 30Hz to 700Hz, which is less than two complete decades. The narrow frequency range combined with the constant movement means you simply don’t have enough time to record a lower frequency event (preventing sight at deeper depths.)
Any ground survey is able to increase the range of frequencies. But Titan 24 measures over 6 decades: a broad band between .01 Hz and 12 kHz. The upper frequency limitation means airborne tipper MT surveys like ZTEM cannot provide the shallow resolution available with Titan 24; and the lower frequency limitation prevents ZTEM from penetrating to the same depths as Titan 24’s ground MT Data.
- One Set of Data vs. an Integrated Set of Data: Since airborne surveys cannot measure the electric field (or ‘galvanic components’) they can only collect magnetic (or ‘inductive’) measurements. Titan 24 integrates both sets of data (electric and magnetic) to provide a more complete interpretation. By collecting two sets of data on the ground (which you can’t get in the air), exploration teams learn more about the mineral components of the subsurface.
The ground vs. airborne survey debate is old and well-documented for strengths and weaknesses. But now, in the case of New Nadina’s porphyry copper discovery led by Mira Geoscience’s Peter Kowalczyk, miningexploration teams are told, “The two work very well together to find big, deep porphyry deposits.”
Both ZTEM (airborne survey) and Titan 24 (ground geophysical survey) were used on New Nadina’s Silver Queen property in attempt to extend the life of the mining site . The surveys intended to pinpoint a deep porphyry copper target system for drilling.
“Using both ZTEM and Titan 24 in combination is a very good exploration strategy,” says Kowalczyk. An exploration team’s goal is to get the most well defined target before drilling. At Silver Queen, after ZTEM went over the property, it was apparent that additional work was required on the ground.
The Titan 24 IP (Induced Polarisation) data allowed the New Nadina exploration team to avoid drilling deep, expensive holes by more clearly defining the anomaly target.
“Titan 24’s ground geophysics adds a great deal of data and gives much greater confidence to site drillholes. The Titan24 IP data was used to target the drillholes, and the Titan24 MT [Magnetotelluric Survey] data provided strong evidence that the mineralizing system extended to depth,” says Kowalczyk.
Sure enough, New Nadina’s Silver Queen deep drill results came back on par with Titan 24’s mapping and interpretation , and there was great praise for Quantec’s ground geophysics exploration. If the giant porphyry had not been mapped by Titan 24’s ground geophysical survey, the team would not have drilled down far enough to pass through the fault to discover a deposit lay hidden below.
“Without the Titan24 IP anomaly, the New Nadina exploration team would not have had a well defined target at depth, and it is unlikely they would have drilled through the fault,” said the Mira geophysicist.
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