The mineral exploration permit application was submitted in August 8, 2017 (Figure 1) and became effective on June 21, 2021. The decision can be found on Tukes’ website using the permit code ML2017: 0104 at https://tukes.fi/malminetsintaluvat-ja-valtaukset and the area can also be viewed on the Mining Authority’s website at https://gtkdata.gtk.fi/kaivosrekisteri/. The exploration permit is valid for four years from becoming effective (until 20 June 2025).
Geologically, the area is situated within the eastern Savo province of the North Karelia Schist Belt (NKSB). Petrologically, the rocks are classified as North Karelian supracrustal rocks. The lithology comprises mostly of Paleoproterozoiz sedimentogen mica schists, named historically as Savo schists, deposited into a rift basin adjacent to the Karelian craton.
Historically, the area contained a known graphite quarry and drilling had been carried out by Outokumpu Oy on several target areas in the vicinity of the quarry. The drilling intersected flake graphite associated with airborne electro-magnetic anomalies. High-grade flake graphite identified in outcrops and re-sampled from drillholes associated with the extensive conductive zones at Rääpysjärvi show the potential for undiscovered flake graphite mineralisation.
Several small scale exploration programmes have been carried out in the area by Grafintec and geology students since 2015. Bedrock mapping was conducted on the most interesting areas already in 2015 for academic purposes, however several anomalous areas were still left unexplored. In 2017, an exploration permit application was submitted and further mapping was carried out by Grafintec to follow up strong aero-electromagnetic anomalies and GTK black schist interpretations over the area, and to locate the historic graphite quarry. The quarry was eventually located at a low small outcrop ridge and is currently a 10x4m water filled pit 2-3m deep. Sampled flake graphite from the quarry has been assayed to >50% Cg.
Further assay results from graphite outcrops and boulders in other EM conductive areas have shown grades ranging between 1 and 16% Cg. Re-sampled graphite from nearby historical drillholes have shown various intercepts with grades ranging between 5 and 6.7% Cg (Figure 2), but the quarry itself and its possible extensions remain untested by drilling.
In June 2021, plans for exploration work, environmental baseline studies and stakeholder communication were continued. Continuous water quality studies were started in early 2022, a ground geophysical GEM-2 survey and follow-up mapping was completed between August-October 2022 (click) (Figure 2) and trenching, channel sampling + assay work was completed in November-December 2022 (click) (Figure 3).
Next potential work steps are drilling, bulk sampling, advanced metallurgy tests, resource estimation, environmental and feasibility studies.
Comparing the exploration results with those from the Company’s Aitolampi project, the EM conductive anomalies at Rääpysjärvi are more extensive, which indicates significant potential for a larger tonnage of graphite mineralisation in the area. Rääpysjärvi EM conductive areas cover 1.1 square kilometres, whereas Aitolampi EM conductive areas cover 0.3 square kilometres. In addition, while most of the assays at Rääpysjärvi are similar to what was sampled prior to drilling at Aitolampi, the >50% graphite assay from the quarry at Rääpysjärvi is exceptional and indicates the potential for localised very high-grade mineralisation.
In 2018, a 10kg composite grab sample from boulders and outcrops sampled in 2017 was sent to SGS Mineral Services in Canada. The testwork produced a combined concentrate grade of 97.4 per cent TGC, with 18.8 per cent in the large and jumbo flake fraction (+180 micron). The head grade of the composite grab sample was 19.8 per cent TGC.
The encouraging metallurgical testwork results, combined with high grade graphite sampled from outcrops associated with extensive EM conductive zones show significant potential for flake graphite mineralisation suitable for anode materials in the area.
Figure 1. Rääpysjärvi geophysical map with exploration highlights in 2017. Click to enlarge image.
Figure 2. The map shows the location of the 13 EM conductive zones and TGC assay results from outcrops and drilling. Click to enlarge image. (Source)
Figure 3. Map illustrating the location of the 13 EM conductive zones and the location of trenches with TGC assay results. (Source)