An assessment of the use of halogens and volatile compounds in vegetation, soil and snow in the exploration for concealed deposits: case histories from Lara and Mount Washington, Vancouver Island (NTS 092B/13 and 092F/14)

Project code: 2016-007

Project type: Minerals and Mining

Principal Proponent: Heberlein Geoconsulting

Principal Investigators: David Heberlein and Colin Dunn

Project location: Lara VMS deposit (near Chemainus) and Mount Washington Epithermal Gold prospect (near Courtenay), Vancouver Island


Summary
This project aimed to build an understanding of mineralization at Lara and Mount Washington by analyzing soil, plant and snow samples in the area. It also aimed to improve the commercially-available process for analysing samples.

The Need
Low-impact and effective methods for identifying mineral deposits help the minerals and mining industry to reduce the impact of exploration activity. They can also lower costs and increase efficiency of mineral exploration. This project helps to verify previous data from two sites while also helping to develop new and innovative technologies for future commercial use.

Project Goals
This project aimed to:

  • Broaden the range of sample media used at two sites to identify potential mineral deposits.
  • Demonstrate the effectiveness of commercially-available analytical methods and new instrumentation for detecting mineralization-related elements and compounds

Project Benefits
The innovative methods used in this study will help to develop new and low impact ways of identifying potential mineral deposits in British Columbia and beyond.

Survey Area
The Lara site is in Cowichan and Halalt territory approximately 25 kilometres southwest of Chemainus and 75 kilometres north of Victoria on Vancouver Island. Access to the site is by existing logging and drilling roads, and by BC Hydro right-of-way.

The Mount Washington site lies immediately north of the Mount Washington Alpine Resort in K'ómoks territory. Access to the sampling sites is by existing mining and drilling roads.

How was the data collected?
The presence of halogen elements (fluorine, chlorine, bromine and iodine) in soil, plant and snow samples can indicate the possibility of minerals below the ground.

At Lara, samples of the predominant tree species - Douglas-fir, western hemlock and western redcedar were collected, along with soil samples taken from the same location. At some sites samples of understorey species (plants that below beneath the forest canopy) -- such as Western sword fern -- were also collected.

At Mount Washington 18 passive ion collectors were installed, along with samples of foliage and fluids from mountain hemlock at some locations. Snow samples were also collected and analyzed.

The main challenge for this project was defining a method of analyzing the halogens and anions to geologically meaningful detection limits while dealing with the interferences caused by high organic contents of the chosen sample media. Identification of an effective analytical method involved a significant amount of research that was carried out at the BC Ministry of Environment in Victoria, BC and at ALS Minerals Ltd. in North Vancouver. Details of the development of the analytical methods are summarized in the final reports for each site.

What was found?

This project demonstrates that sampling and analyzing halogen elements can be an effective new tool when exploring for buried mineral deposits. It also highlights the appropriate sample type and analytical methods to use.

However, these are specific to one forest type and surficial environment and do not encompass all potential environments in BC. More work is therefore needed to optimize sample types in other common forest types such as the spruce, lodgepole pine or Douglas-fir forests of the Interior. Further development of the analytical methods is important if halogen elements are to become widely used by the mineral exploration community.

Final Deliverables

  • Geoscience BC Map 2017-11: Halogens and Other Volatile Compounds in Surface Sample Media as Indicators of Mineralization, Part 1: Lara VMS Deposits, Vancouver Island, BC (NTS092B/13) - Released August 9, 2017
  • Geoscience BC Report 2017-12: Halogens and Other Volatile Compounds in Surface Sample Media as Indicators of Mineralization, Part 2: Mount Washington Epithermal Gold-Copper-Silver Prospect, Vancouver Island, BC (NTS 092F/14) - Released August 9, 2017

The Detail

  • Preliminary results of a geochemical investigation of halogen and other volatile compounds related to mineralization: Lara volcanogenic massive-sulphide deposit (NTS092F/13) and Mount Washington epithermal gold prospect (NTS 092F/14), Vancouver Island, BC (Roundup Poster 2017) (PDF, 10.6 MB)
  • Report 2017-1: Summary of Activities - Preliminary Results of a Geochemical Investigation of Halogen and Other Volatile Compounds Related to Mineralization, Part 1: Lara Volcanogenic Massive-Sulphide Deposit, Vancouver Island (NTS 092B/13) (PDF, 2.6 MB)
  • Report 2017-1:Summary of Activities - Preliminary Results of a Geochemical Investigation of Halogen and Other Volatile Compounds Related to Mineralization, Part 2: Mount Washington Epithermal Gold Prospect, Vancouver Island (NTS 092F/14) (PDF, 2.2 MB)

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