Understanding structure: X marks the spot

When geologists are planning a drilling program they want to have as much information as possible before the drill starts turning. Tocvan put out a press release  October 27 which, in technical language, indicated that the company’s geologists has reached some conclusions as to the geological structures at its Pilar Gold-Silver Project in Sonora, Mexico. And it is those structures which will determine where Tocvan (C.TOC) will drill.

The problem is that whenever geos start talking about structure they tend to drift off into very detailed and largely incomprehensible “geo speak” which leaves the investor no wiser. What are these structures, how do you “see” them and why do they matter? Fortunately, while he is a geologist, Mark Smethurst, COO of Tocvan, is also very good at translating geo speak into regular English.

We began our conversation talking about the tools Tocvan was using. “We used induced polarization to look down to about 300 meters, and 3D Inversion Magnetic Susceptibility to go down to 600 meters,” said Smethurst. “We collect the data and then send it to geo-physicists and specialists who interpret the data and provide 3D images that can be used in targeting the mineralization that is contained within and controlled by the structures found on the property. Structures such as faults and shear zones.”

It’s a process, as Smethurst puts it, “It’s the evolution of knowledge over time. You are testing previous knowledge. You start by walking around looking for geo clues, looking for features which occurred in the past. You look for the features in LIDAR and you line up the LIDAR image with what the geo-physicists are telling you.”

“You are trying to confirm structures which are indicated at surface,” said Smethurst. “You take your prior work and update your interpretation.”

C.TOC, Tocvan Ventures
Figure 1

“If you look at Figure 1 you will see the deep rich blue which shows magnetic susceptibility lows and red which shows magnetic susceptibility highs . . You want the lows,” said Smethurst. “This is an image of the rock 600 meters down.”

“The blue lows are openings. Where the crust has torn,” said Smethurst. “That’s where there is weakness, where there is a shear zone.”

“If you take a sheet of paper and put it on your desk and push one side up and the other down you will see the paper deform and, if you put enough pressure on, eventually tear,” said Smethurst. “Where there is a tear the features open up and there is porous space. The fluids which carry mineralization flow up through the tear.”

“Those fluids are pushed by pressure below but also sucked by the vacuum above,” said Smethurst. “The hydrothermal fluid here is molten quartz. It has the viscosity of oil on a cold winter morning. And in that fluid you’ll see gold, silver, zinc and lead.”

C.TOC, Tocvan Ventures
Figure 2

“The second figure is an image using the same technique as Figure 1 but this time 400 meters below surface. The structures are less sharply defined at this level because of weathering,” said Smethurst. “Thirty-five million years of weathering have smeared the features.”

The third figure is an image taken using Induced Polarization. IP is effective to 300 meters and it tracks structure,” said Smethurst. “We are seeing a corridor running NW/SE. We are also seeing a “pipe” in line with the structures. The system is fed by fissures which are actually bigger than faults”

C.TOC, Tocvan Ventures
Figure 3

The objective of this imaging is to find the best drilling targets. If you look at Figure 1 again, you will see dashed white lines. These are north-trending faults and those faults are co-incident with gold intercepts from historic drilling. If you overlay Figure 3 you can get a sense of the vertical structure reaching surface.

“It’s like a pirate’s treasure map. X marks the spot,” said Smethurst.

The next step for Tocvan is to choose actual drill targets and start drilling. The company has the historic drill results but it has also identified new targets which warrant drilling. Smethurst and his team have focussed the search for drilling targets. Now the drill will test the knowledge Tocvan has already developed about the Pilar property.

For the investor, this sort of meticulous pre-drilling preparation is very good news. Drilling is expensive. Being able to carefully target a drilling program means that program will have a much greater chance of success. The junior resource market is driven by drilling, a few good holes and Tocvan could easily double it’s current $0.35 share value.

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