Snow as proxy for mineral exploration – a case study from Northern Finland

Modern mineral exploration techniques for Europe are required to be sustainable, environmental friendly and social acceptable. Especially for the geochemical exploration of the ecologically sensitive areas of northern Europe this poses a challenge, because any heavy machinery or invasive methods might cause long-lasting damage to the natural systems. One way of reducing the impact of mineral exploration on the environment during early stages of the exploration is to use surface media, such as upper soil horizons, water, plants and snow. Of these options, snow has several advantages: Sampling and analysing snow is fast and low in costs, it has no impact on the environment, and it is (in winter time) ubiquitous, i.e. available independent of land cover and environment.
In the “New Exploration Technologies (NEXT)” project, funded by the European Union’s Horizon 2020 research and innovation programme, 171 snow samples and 13 field duplicate snow samples for quality control, were collected in March-April 2019 to strengthen the idea of using snow as a sampling material for mineral exploration. The Rajapalot Au-Co prospect in northern Finland, 60 km west from Rovaniemi and operated by Mawson Oy, was selected as a test site. Stratified random sampling was used to create the uneven sampling net over the test area. The samples were analysed at GTK using a Nu AttoM single collector inductively coupled plasma mass spectrometry (SC-ICPMS) which returned analytical results for 52 elements at the ppt level. Due to strict quality control, only Ba, Ca, Cr, Cs, Ga, Li, Mg, Rb, Sb, Sr, Tk, V and Zn passed and were used in the final data analysis.
The preliminary results based on PCA show a strong dependency of snow composition on the soil type. That is, there is a difference if the snow sample was taken above mineral soil or organic soil. Thus, the soil type should be included in the models or the data analysis should be looked separately for different soil types. The linear model predictions were used to test if the snow geochemistry can predict the bedrock geochemistry. For Al, Ca, Li, Sr and Na the prediction works well. Instead of using snow directly for detecting the mineralization for pinpointing drill targets for exploration purposes, snow geochemistry could be used as a lithogeochemical mapping tool to delineate the areas where to continue exploration with more sensitive methods.