Summary:
The Keliber Project is located in the Kaustinen Lithium Pegmatite (KLP) Province of western Finland, covering an area of about 500 km² (SRK, 2023 and references therein). The underlying geology comprises Palaeoproterozoic (1.95-1.88 Ga) supracrustal rocks of the northern Pohjanmaa Belt (also referred to as the Ostrobothnia Schist Belt) which forms a 350 km long and 70 km wide arcuate belt between the Central Finland Granitoid Complex to the east (Vaasjoki et al., 2005) and the Vaasa Granitoid Complex in the west (Aviola et al., 2001).
Syväjärvi Geology
The Syväjärvi lithium pegmatite deposit is overlain by an average of 8 m (ranging from <1 m to approximately 20 m) of sandy till cover (SRK, 2023 and reference therein). Outcrop within the Project is limited to an isolated exposure of a host rock comprising plagioclase porphyrite (porphyritic metavolcanic). The geological model used to define the morphology, attitude, and thicknesses of the various pegmatites and contact relationships with host rocks was derived entirely from surface drilling. At Syväjärvi, five modelled spodumene-bearing pegmatite veins are intruded into mica schists, metagreywackes, and metavolcanics following a broad antiformal structure forming "saddleback" type reefs. This has resulted in a series of shallow northerly dipping pegmatite veins, the largest of these attaining thicknesses of up to 20 m in places. The strike length totals 365 m for all veins, extending approximately 810 m down dip and to a maximum depth below surface of 170 m.
Rapasaari Geology
The Rapasaari lithium pegmatite deposit is covered by a variable cover of till and overburden averaging 12.5 m, ranging from 2.5 m to 30 m in thickness, and outcrops are rare. In places, the till is overlain by peat which can reach up to 2 m in thickness. The pegmatites that make up the Rapasaari deposit are intruded as a series of curvilinear, structurally controlled pegmatites with variable thicknesses resulting in a series of bifurcating lenses and veins that follow a southwesterly plunging synformal structure.
Pegmatite contacts are typically sharp, with the frequent development of weakly mineralised or un-mineralised zones of muscovite-rich pegmatite within and along pegmatite margins. The style of pegmatite emplacement has also resulted in the frequent inclusions/xenoliths/rafts of country rocks throughout all the modelled pegmatites at Rapasaari, with these representing internal dilution to the modelled pegmatites.
The three largest modelled pegmatites vary in thickness from 10 m to 30 m, with most of the minor (modelled) pegmatites having thicknesses of less than 10 m. The strike extent totals 1,300 m for all veins - approximately 700 m in the primary dip orientation (east-west) - to a maximum depth below surface of 330 m. Due to the variability in the strike and dip of the pegmatite/s, true pegmatite thicknesses were generally 70-90% of the drill intercept length.
Länttä Geology
The Länttä lithium pegmatite deposit is covered by a thin veneer of sediments and till averaging 5.5 m and ranging from 2 m to 10 m in thickness. The deposit was discovered during road excavation work in the 1950s. Subsequent drilling completed by historical operators (Suomen Mineraali Oy and Partek Oy) and Keliber delineated three parallel-trending pegmatite veins with a 420 m northeasterly strike and steep southeasterly dips (>60°) to a maximum depth of 220 m below surface, extending approximately 100 m southeast of the outcrop location.
Emmes Geology
The Emmes lithium pegmatite deposit is largely located under Lake Storträsket, close to the village of Emmes. Overburden thickness is highly variable ranging from 2.5-17 m, reaching 17 m thickness under the lake and 10 m closer to the village, and average overburden thickness is approximately 8 m. Exploration drilling completed to date has identified and delineated a single 400 m long pegmatite vein, striking southeast-northwest, extending down dip for 260 m and dipping at ~45-50° to the southwest and a depth of 225 m below surface.
The spodumene, which is similar to that observed in the other pegmatites, is light grey to green in colour as is modal mineralogy which is dominated by feldspar, quartz, spodumene, and muscovite. No inclusions or xenoliths of country/host rock have been identified within the Emmes pegmatite.
Outovesi Geology
The Outovesi deposit was discovered by Keliber in 2010 and is covered by surficial till sediments that range from 8.5 m to 18.5 m and average 14 m in thickness. The deposit was subsequently drilled and comprises a single pegmatite vein striking northeast-southwest for approximately 550 m, reaching a maximum thickness of 10 m. The vein has a variable dip to the southeast at between ~40-80° to a depth of 100 m below surface. Host rocks are dominated by homogenous mica schists and metagreywackes, with the northern parts of the deposit being hosted by more graphite-rich schists. The Outovesi pegmatite has intruded almost at right angles to the host rock fabric, which is different to that at the Länttä and Rapasaari deposits where the pegmatites have generally intruded parallel to host rock fabrics. Contacts with the host rocks are sharp, with true pegmatite thicknesses being generally 90% of drill length.
Leviäkangas Geology
The Leviäkangas lithium pegmatite deposit is located in the Kaustinen Municipality of Western Finland approximately 10 km north of Kaustinen town.
Exploration drilling has identified a single sigmoidal shaped spodumene pegmatite with a strike length of 500 m along a north-northwest strike and dips at between 45° and 60° to the west. The pegmatite is conformably intruded into host rocks comprising mica schists interlayered with metagreywacke and black schist layers and, locally, plagioclase porphyritic rocks units are present (PL Mineral Reserve Services, 2016 and SRK, 2023). The thickness of the pegmatite varies from a few metres to approximately 20 m. The overburden is formed by till with some peat at the surface at Leviäkangas and varies in thickness from 3.5 m to 14 m, averaging 7.5 m.
Close to, and at the contact with the host rocks, the spodumene in the pegmatite is altered to muscovite. This persists for a few tens of centimetres up to 1.5 m. In addition, there are a few narrow (0.5-3 m) internal waste zones in the pegmatite comprising mica-schist xenoliths or where the spodumene is replaced by muscovite resulting in low Li2O grades.
Spodumene typically occurs as coarse-grained, light greyish-green lath-shaped crystals between 2 cm and 10 cm long and orientated perpendicular to the contacts of the veins with the wall rock. The pegmatite consists predominantly of albite (37-41%), quartz (28%), potassium feldspar (orthoclase) (15%), spodumene (10%), and muscovite (6-7%), with accessory minerals comprising apatite, cassiterite, cookeite, garnet, graphite, Mn-Fe phosphate, montebrasite, Nb-Ta oxides, sphalerite, tourmaline, and zeolite (Ahtola et al., 2015).
Tuoreetsaaret Geology
The Tuoreetsaaret lithium pegmatite deposit, also located in the Kaustinen Municipality of western Finland was discovered by Keliber using a combination of geological, geochemical, and geophysical data and led to the first intersection by diamond core drilling in March 2020 (SRK, 2023). The deposit comprises three north-south striking and one northwest striking lithium-bearing pegmatite vein-like bodies intruded into country rocks comprising intermediate meta-tuffite, plagioclase porphyrite, mica schist, and sulphide-bearing mica schist. The hanging wall is generally formed by intermediate meta-tuffite and the footwall by mica schist and sulphide-bearing mica schist. Plagioclase porphyrite generally forms the middling between the pegmatite veins. The pegmatite veins and their wall rocks are covered by 10 m to 35 m, averaging 22 m of glacial till with peat at the top.