BC’s northern Interior Plateau south of Vanderhoof and west of Quesnel is covered by a thick layer of glacial sediments and young volcanic rocks. This cover hides the complex geology of the area and potentially untapped mineral wealth and geothermal resources hidden within. Surficial sediment geochemical and mineralogical anomalies can be used to locate buried mineralization.
New tools that can see through this cover without causing disturbance at the surface can potentially be useful for mineral exploration programs. This study assesses the value of an alternative sampling medium for local‐ and regional‐scale geochemical sampling programs in areas where conventional soil‐sampling methods might be found ineffective.
The project:
Indigenous groups, communities, the mineral exploration sector and land managers need access to reliable earth science information to make informed decisions in the TREK area where mineral resource potential is high.
Tree sap is potentially useful for regional and local scale exploration. Where a single species of tree is common and widespread it has the potential advantage over traditional media, such as tills and soils, in that it has a matrix that is compositionally consistent over large areas. It therefore provides samples of similar appearance and consistency. It is also less prone to the hard‐to-interpret variations caused by matrix variability encountered in other media. Once sap has congealed on the tree bark, it is chemically inert, easy to find and quick to sample, including in recent clear cut areas where it can be found on fallen logs and tree stumps.
This project was focused on the northwestern corner of the TREK project area, in the area around the Endako Mine (Minfile 093K 006) and Nithi Mountain prospect (093F 012).
Congealed sap samples were collected in two sampling campaigns (September 2013 and May 2014) from the surfaces of more than 100 white spruce trees from an area over 1,000 km2 surrounding the Endako Molybdenum mine. For comparison, soil pH measurements were made and organic soil samples (Ah horizon) were collected at the same locations. Lodgepole pine sap was also obtained from select sample locations to compare the white spruce sap chemistry with that of lodgepole pine. An additional database of element concentrations in pine bark collected in the 1990s from the same general area was also available for comparison.
Geoscience BC Report 2015-02 presents the results of a geochemical study undertaken to determine if tree sap could provide a useful and possibly unique geochemical signal to buried mineralization.
This project concluded that if appropriate sampling protocols are followed, spruce sap is an effective sample medium for regional scale exploration for porphyry molybdenum mineralization and there seems no impediment to using this method with exploration for other minerals. Spruce sap is easy to collect and can be submitted to a laboratory for analysis with no further preparation. Element concentrations are mostly in the parts per billion range, so precision is likely to be inferior to that usually obtained from the analysis of soils or live vegetation. However, in areas of suspected contamination the sap might be a preferred sample medium since it derives its chemical signature from deep in the ground. Furthermore, the digestion procedure developed for this project further excludes potential dust contamination from the analytical sample. The congealed sap contains the geochemical signature of major elements that are surplus to the trees’ metabolic function as well as pathfinder elements that perform no known function in plant growth and health, and so become readily exuded.