The Quesnel terrane is a distinct package of rocks oriented roughly northwest-southeast across BC that hosts several significant copper-gold deposits. In much of the CICGR program area, the Quesnel terrane is buried under thick glacial deposits. With the Mount Milligan mine to the north and the Gibraltar mine to the south, it is believed that similar mineral deposits may be hidden below the thick glacial deposits between these mines.
This project is using new surficial geology mapping based on aerial photograph interpretations and field verification to inform the collection and interpretation of new till geochemical and mineralogical data that can be used to help ‘see through’ the glacial deposits and improve understanding of the rocks below, and their potential to host mineral deposits.
Glacial drift is composed of various sediment types, from well-sorted clay to cobble and boulder gravels, deposited during glaciation. Subglacial till, one component of glacial drift, is an unsorted mixture of fine- and course-grained sediment (i.e. clay to boulder) derived through glacial abrasion and entrainment of bedrock that is transported and deposited in the direction of ice flow. Subglacial till’s predictable relationship with bedrock makes it an optimal material to guide mineral exploration. Till covers large portions of the landscape throughout BC and can range from a few centimetres to hundreds of metres in thickness. For till to be used as a mineral exploration tool, it is necessary to understand its characteristics, including transport directions, thickness, distribution and geochemical and mineralogical composition.
This project fits under Geoscience BC’s Strategic Objective of ‘Identifying New Natural Resource Opportunities’ and our goal to:
- Continue regional-scale surveys that deliver large data sets in support of identifying prospective targets and increasing discovery rates of deposits
This project is part of the CICGR series and is:
- Generating surficial geology, till sample suitability and drift thickness map sets:
- These will identify the distribution and characteristics of surficial sediments and associated sediment transport directions. The map sets will be used to identify the most suitable locations for till sampling in later stages of this project and will guide follow-up mineral exploration initiatives.
- Re-analyzing up to 1,750 previously collected till samples:
- Collecting new till samples and adding to provincial archive:
- New till geochemical and mineralogical data will be added to the provincial database, increasing the sample density where it is currently low and providing new data in prospective areas where none currently exists.
- Creating new reports and presentations:
- This project is generating map sets and spatial data packages for surficial geology and derivative mapping along with new and updated till geochemical and mineralogical data packages.
- Training junior mappers and samplers:
- The next generation of mineral explorers will be trained in glacial drift prospecting methods including surficial geology interpretations and till sampling.
The maps, reports and database of till geochemical and mineralogical concentrations from this project will provide a better understanding of the geology and mineral potential of BC’s North Central and South Central regions where much of the bedrock is obscured by thick drift. This will help to inform decisions relating to mineral exploration and to attract new investment to the area.
This project covers around 9,000 km2 of BC’s North Central and South Central regions in areas around Fort St James, Mackenzie, Prince George, Quesnel, Vanderhoof and Williams Lake.
What Was Found
In June 2021, the first two reports for this project were published. Report 2021-09 contains results for reanalysis results from the first batch of archived subglacial till samples collected in the 1990s and 2000s and stored at the Geological Survey of Canada in Ottawa and the British Columbia Geological Survey in Victoria.
1,039 recovered till samples were analyzed by Bureau Veritas Commodities Laboratory in Vancouver, BC for 53 minor and trace elements by inductively coupled plasma–mass spectrometry (ICP-MS) and inductively coupled plasma–emission spectrometry (ICP-ES). The reanalysis of archived samples using current laboratory techniques significantly improves the utility of the existing provincial till geochemical database.
The digital data is presented in two database files:
- GBC Report 2021-09 Digital Data File 1: Includes new analytical results for archived till samples collected during regional till surveys conducted by the GSC in the 1990s.
- GBC Report 2021-09 Digital Data File 2: Includes new analytical results for archived till samples collected during regional till surveys completed as part of Geoscience BC’s QUEST Project.
A set of surficial geology, till sampling suitability and drift thickness maps were also released for the northern portion of the CICGR project area in June 2021 as Report 2021-03. Three maps were released for each of the following six 1:50K NTS map sheets:
- NTS 093J/03 – Saxton Lake area
- NTS 093J/07 – Summit Lake area
- NTS 093K/09 – Pinchi Lake area
- NTS 093K/16 – Tezzeron Creek area
- NTS 093O/03 – Tudyah Lake area
- NTS 093O/04 – Philip lake area
A set of surficial geology, till sampling suitability and drift thickness maps for the southern portion were released in April 2022, with the analytical results and reports expected to be published later in the year. Three maps were released for each of the following six 1:50K NTS map sheets:
- NTS 093A/13 – Swift River area
- NTS 093G/01 – Cottonwood area
- NTS 093G/07 – Pinchi Lake area
- NTS 093G/09 – Hixon area
- NTS 093G/10 – Pitoney Lake area
- NTS 093G/16 – Wansa Creek area
The purpose of the surficial map series is to inventory and characterize surficial materials and landforms, which in turn informs resource exploration and infrastructure development. The surficial geology polygons are based on surficial material and their expression, and are overlain by geomorphological process information. The till sampling suitability maps are derived from the surficial geology, with suitability being a function of the proportion of a surficial geology polygon that contains subglacial till that is suitable for sampling. Drift thickness mapping provides an indication of the relative thickness of Quaternary sediment cover based on the results of the surficial geology interpretations and can be used to identify areas where deep till sampling may be necessary or can inform drift-based mineral exploration programs and where bedrock mapping and prospecting programs can be focussed.
The January 2023 project report (Geoscience BC Report 2023-03) presents a summary of the till geochemical and mineralogical surveys conducted during the 2020 and 2021 field seasons, along with the results of the Talon Drill(TM) drill-supported till sampling work. This sampling program infilled the historic dataset gaps identified at the start of the project.
Till samples were analyzed via instrumental neutron activation analysis (INAA), and inductively coupled plasma-mass and -emission spectrography (ICP-MS and ICP-ES).
In testing drill-supported sampling to achieve more optimal sampling distributions, it was found that the Talon Drill, combined with customized bits and samplers, was an effective tool for the purpose and extended sample coverage into areas where standard opportunistic sampling methods were not successful.