This article evaluates the known rare earth elements (REE), Ti and Li occurrences and exploration potential in Finland, based on existing data combined with new geochemistry and mineralogy, heavy mineral studies, geophysical measurements, geologic mapping and recent drilling of new targets. The potential rock types for REE include carbonatite (Sokli, Korsnäs), alkaline rocks (Otanmäki, Lamujärvi, and Iivaara), rapakivi granite and pegmatite (Kovela), and kaolin-bearing weathering crusts in eastern and northern Finland. The highest REE concentrations occur in late magmatic carbonatite veins in the fenite area of the Sokli carbonatite complex. Detailed mineralogical investigations have revealed three distinct types of REE mineralization as phosphates, carbonates and silicates in the studied areas. Mineralogical and mineral chemical evidence demonstrates that hydrothermal processes are responsible for the REE mineralization in the studied rocks and confirms that such processes are predominant in the formation of REE minerals in carbonatite, calc-silicate rocks and albitite. Titanium occurs as ilmenite in hard rock deposits in Paleoproterozoic subalkaline mafic intrusions. The Otanmäki ilmenite was mined together with vanadium-rich magnetite from 1953 to 1985 from a small gabbro—anorthosite complex, which still contains potential for Ti resources. Other major ilmenite deposits are within the Koivusaarenneva ilmenite gabbro intrusion and Kauhajärvi apatite—ilmenite—magnetite gabbro complex. Possible Ti resources are included in Ti-magnetite gabbro of the large layered mafic intrusions in northern Finland, such as at the former Mustavaara vanadium mine. For several years, Rare Element (RE)-pegmatite of the Kaustinen and Somero—Tammela areas has been the objective of Li exploration by the Geological Survey of Finland (GTK). At Kaustinen, Li-pegmatite occurs as subparallel dyke swarms in an area of 500 km2 within Paleoproterozoic mica schists and metavolcanic rocks. Li pegmatite contains more than 10% spodumene as megacrysts (1–10 cm), albite, quartz, K-feldspar, muscovite and accessory minerals such as columbite-group minerals, apatite, tourmaline, beryl, Fe-oxide minerals and garnet. The Kaustinen spodumene pegmatite and Somero—Tammela petalite—spodumene pegmatite contain potential Li resources for the battery industry in EU countries.
A circular Bouguer gravity anomaly with a minimum of -4.0 mGal and halfamplitude width of 2 km was recognized at Lake Iso-Naakkima (62°11'N, 27°09'E), southeastern Finland.The gravity low is associated with subdued aeromagnetic signature and notable airborne and ground electromagnetic anomalies that indicate low bedrock resistivity.The drilling record beneath the recent (Quaternary) glacial sediments, 25-40 m thick, reveals a 100 m thick sequence of unmetamorphosed shale, siltstone, quartz sandstone, kaolinitic clay and conglomeratic sandstone that rest on a weathered mica gneiss basement.The upward fining sequence is characterized by red colour, high kaolinite content, and tilted, distorted and brecciated beds.According to the geophysical modelling the diameter of the whole basin is 3 km and that of the sedimentary rocks 2 km, and the depth is 160 m.Shock lamellas in quartz clasts of the basal conglomeratic sandstone, almost omnipresent kink banding in micas of the rocks beneath the basin floor and the occurrence of polymictic dike breccia in the underlying mica gneiss suggest shock metamorphism.It was concluded that the basin originated by a meteorite impact.However, the impact-generated rocks were subsequently eroded before the sedimentation and only minor marks of shock metamorphism were preserved.Lateritic weathering took place prior to deposition of the sediments.Quartz sandstone and siltstone are interpreted as fluvial deposits and the thinly laminated shales as transgressi ve lacustrine or lagoonal deposits.The microfossil assemblage in the shale includes sphaeromorphs of acritarchs from Late Riphean (Neoproterozoic).Postdepositional subsidence of the Iso-Naakkima basin, shown by tilted sediments, preserved the sequence from further erosion.
REE‐rich minerals were identified and analyzed by electron microprobe from different targets located in the northern and central Finland. Both primary and hydrothermal minerals were found namely: phosphates (monazite‐Ce), fluor‐carbonates (bastnaesite‐Ce), hydrated carbonates (ancylite‐Ce), hydrated aluminium silicates, (allanite), oxides (fergusonite) and U‐Pb rich minerals. Sokli Jammi‐ Kaulus carbonatite veins are enriched in LREE, P, F, Sr and Ba hosting in ancylite, bastnaesite, apatite and monazite. Allanite‐(Ce) and fergusonite (Y) are abundant in alkaline gneiss of the Katajakangas REE‐occurrence. The Korsnas Pb‐REE deposit includes apatite with monazite inclusions, calcio‐ancylite and bastnasite. The Makara‐ Vaulo REE‐prospect in arkosic gneisses is dominated by monazite, allanite and xenotime. Albitites at Enontekio contain bastnaesite, monazite, allanite, xenotime and U‐rich minerals includes davidite, masuyite and sayrite. The Honkilehto Au‐Co‐S‐mineralization at Kuusamo is characterized by U‐rich minerals with bastnaesite and allanite. The results obtained provide vital insights into the mineralizing processes associated with REE‐prospects in northern and central Finland.
P283 GEOPHYSICAL INVESTIGATIONS OF THE HYYPIÄMÄKI CALCITE MARBLE DEPOSIT SOUTHWESTERN FINLAND JAANA LOHVA and OLLI SARAPÄÄ Introduction The Geological Survey of Finland (GTK) has increased the exploration capacity of industrial minerals during the last few years. In Finland carbonate rocks including marbles are consumed yearly about four million tons value of this being about 350 millions euros. Two third of needed carbonate rocks are produced in Finland. Since 1994 GTK has explored calcite marble from Uusimaa Belt SW-Finland for production of micronised calcite using in paper industry. The Uusimaa Belt is a part of an accretionary arc complex of southern
The Jammi area consists of Archaean mafic volcanic rock and tonalitic gneiss, which were intruded by the Devonian Sokli carbonatite, causing large-scale and intense fenitization of the country rocks. The rocks are albite-fenites, crosscutting late carbonatite veins, with the mineral assemblages of calcite-dolomite-aegirine-albite-apatite-phlogopite. Geochemical analyses indicate that the total content of rare earth elements (REE) in the carbonatite veins is 0.11–1.83%, including 0.11–1.81% LREE and 0.002–0.041% HREE. Seven rare earth minerals have been analysed in detail from the area, including Sr-apatite, monazite, ancylite (Ce), bastnäsite (Ce), strontianite, baryte and brabanite. The Jammi carbonatite and fenite samples display similar REE patterns, with highest enrichment of LREE, and steep slopes towards the HREEs. The REE distribution in the whole-rock data is controlled by carbonates and apatite. REE-rich accessory phases such as monazite and ancylite (Ce) influence the REE pattern only when present in large amounts. Mineralogical and chemical evidence demonstrates that hydrothermal processes were responsible for the REE mineralization. During late-stage processes, apatite and carbonate minerals were replaced by various assemblages of REE–Sr–Ba minerals. Apatite could be a potential source for REE as a by-product of phosphate production in the Sokli area.
The study deals with the bacterial type discovered in a Jatulian deposit at Kiihtelysvaara.The morphology of the microbic fossil, when compared with current forms, suggests that it is an early sulphur bacterium, named Hyypiana jatulica.The deposit is part of the Marine Jatulian dated at c. 2000 Ma.The fossile type occurs in chert nodules within the dolomite.
The Mäkärä Au-rare earth element (REE) prospect area is located in the Tana Belt, south of the 1.9 Ga Lapland Granulite Belt, in northern Finland. The Belt has prominent lanthanum (La) and yttrium (Y) anomalies in regional till and bedrock geochemical data. High Y indicates enrichment of heavy REE in the bedrock. At Mäkärä, promising narrow Au-hematite-quartz veins occur in connection with tensional fractures in the great shear zone. Under the latest ice divide of the last glaciation, subglacial erosion was weak and glacial transport distance short. High Au contents in saprolite and till together with deep weathering have a strong positive correlation with the positive electromagnetic anomalies caused by the sulphidic gneisses. The highest La and Y contents in till correlate well with the Th maxima of airborne-radiometric datasets. Locally, the <0.06 mm till size fraction contains up to 0.4% REE. A recent exploration project in Mäkärä revealed a 13 m wide Au-hematite-quartz vein with a mean of 3 ppm Au and 0.04–0.1% REE in kaolinitic saprolite derived from arkosic gneiss. The elevated REE content resembles that of ionic adsorption clays in China. Typical REE-rich minerals are monazite, rhabdophane, xenotime and kaolinite. Till geochemistry proved useful in REE exploration.
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