Q&A on Geoscience BC Report on soil gas testing

On June 4, 2020, Geoscience BC released news about an innovative technique to rapidly test gas concentrations in soil that may help to identify new mineral exploration opportunities in British Columbia. Here is a link to their news release: New Device Provides Real-Time Measurement of Soil Gas Concentrations to Help Identify Mineral Deposits

Based on this report, AME’s President and CEO, Kendra Johnston posed some specific questions to the team at Geoscience BC to dig deeper into some of the specifics of the geochemistry. Here is the Q&A, with a big thank you to Brady Clift, David Sacco, and Ray Lett.

Q: Does it just measure CO2 and O2? 

A: The current setup only measures those two gases.

Q: Do the relative difference between non-mineralized and mineralized ground or perhaps the difference in CO2 to O2 tell you anything about the type of mineralization that might be present?

A: In general, where there is sulphide mineralization you would expect to see an increase in CO2 due to oxidation of sulphides which has consumed and decreased the amount of O2.  While you don’t get a sense of the type of mineralizing system you would expect sulphide minerals to create an anomaly in the overlying gases.

Q: Does it work or could it work for minerals other than Cu and Au?

A: There are a number of cases studies where CO2 and O2 have been used to identify all types of sulphide minerals including copper, gold, lead, zinc and iron (more information in Geoscience BC report 2020-07).  The theory/chemistry is mainly related to the creation of sulphuric acid, so any abundant enough sulphides could provide a detectable anomaly.

Q: What is the significance of new soil gas testing system to junior explorers in BC?

A: It provides a junior explorer with real-time, on site indication of a fault and/or presence of mineral sulphides to guide their mineral exploration efforts and make on-site decisions about exploration strategies. Keep in mind that it is another exploration tool for the junior explorer’s toolbox, and should be used in combination with other explorations methods. Soil gas testing could be considered analogous to using portable XRF in that it provides valuable information in the field, but anomalies should be corroborated by sampling and laboratory analysis before decisions about significant resource allocations are made.

Q: Is this a tool can help us find buried deposits, if so how deep do you think it can see?

A: Yes, the purpose of this tool is to help identify the location of buried deposits. More testing is required to define the maximum depth at which the system can be used. The functionality is dependent on both material depth and type. Pilot testing focused on relatively thin material to limit variables that could affect the results, but previous soil gas studies (see references in Geoscience BC report 2020-07) indicate a soil gas signal from bedrock can be measured in 10’s of metres of overburden.

Q: How does it work in a till environment?

A: Based on our initial testing, the system seems to function well in till. Other studies have shown soil gas anomalies detected in up to 30 m of till. We are currently searching for collaborators interested in supporting additional testing that will provide more information on the application of soil gas sampling in different surficial environments.

Q: Does the moisture level of the soil impact the reading?

A: The impact of soil moisture is currently unknown. Gas must be able to diffuse to the surface, so it is unlikely to be effective in saturated soils such as a bog or swamp. More research is needed, and we are hoping to look at a comparison of soil gas and soil moisture in the next round of testing.

Q: If I would like to make use of this tool on my project, who should I contact?

A: Dave Sacco at Palmer’s Vancouver office can be contacted if there is interest applying soil gas measurements to an exploration project.

Q: If you’re searching for a narrow vein how close do your sample sites need to be, what is the reach of the gas measurement in the soil?

A: This question will be a main focus of the next round of testing. At this point, we are unsure what the extent of the detectable soil gas ‘halo’ is and what variables may affect it. It is possible that the halo may increase in size in relation to the drift thickness.

Q: Does the type of soil (silt, clay sand) affect the reading? 

A: This is another unknown variable. Like soil sampling, we suspect the signal to be affected by extremely low permeability sediments such as clay. However, positive results in till, which generally has fairly low permeability, suggest the method should be effective over most materials.

For more information on this Geoscience BC funded research, visit the Geoscience BC website project page: https://bit.ly/2UD4zUd

Dave Sacco at Palmer can be reached at [email protected] or 778-689-2721