Sheme showing the distribution of greenstone structures in Russian Karelia and Finland.
Based on a general gelogical map of the Baltic Shield (1985)
1 - Phanerozoic strata,
2 - Caledonides,
3 - Middle and Upper Proterozoic (Riphean, Jotnian and sub - Jotnian, 1600 - 700 Ma),
4 - 1750 - 1550Ma rapakivi granites,
5 - 1900 - 1750Ma Karelian (Svecokarelian) granites,
6 - 2000 - 1900Ma Svecofennian (Kalevian, Vepsian, Ludicovian) sedimentary and volcanogenic rocks and their analogues,
7 - 2500 - 2200Ma Middle and Lower Karelian (Ludicovian, Jatulian, Sariolian Sumian, Lapponian) rocks and their analogues,
8 - Archean granulite and gneiss complexes,
9 - 3100-2600Ma Upper Archean greenstone belts,
10 - Lower Archean (Saamian) and partly Upper Archean strata,
11 - block boundaries and faults,
12 - Upper Archean greenstone structures:
1 - Hautavaara, 2 - Manga, 3 - Koikary,
4 - Semch, 5 - Palaselga, 6 - Saezero,
7 - Bergaul, 8 - Sovdozero, 9 - Jalonvaara,
10 - Gimoly, 11 - Ilomantsi, 12 - Tipasjarvi,
13 - Kuhmo, 14 - Suomussalmi, 15 - Kostomuksha,
16 - Hedozero, 17 - Matkalahta, 18 - Toksha,
19 - Senegozero, 20 - Lake Kamennoye, 21 - South Vygozero,
22 - Korosozero, 23 - Parandovo, 24 - Pebozero,
25 - Keret, 26 - Hisovaara, 27 - Tikshozero,
28 - Kichany, 29 - Tersk - Allarechka, 30 - Kolmozero - Voronye.
Greenstone belts: Vedlozero - Segozero (1, 2, 3, 4, 5, 6, 7, 8), Jalonvaara - Ilomantsi (9, 11) , Kuhmo - Suomussalmi (12, 13 , 14), Gimoly - Kostomuksha (10, 15, 16) , Matkalahta (17), Sumozero - Kenozero (18 , 19 , 20 , 22) , South Vygozero (21) , Parandovo - Tikshozero (23, 24 , 25 , 26 , 27 , 28), Tersk - Allarechka (29) , Kolmozero - Voronya (30).
The age of Vedlozero-Segozero komatiites is estimated at 2935-3000 Ga, as shown by the isotope data obtained by the U-Pb zircon method for cross-cutting dykes.
Type sections of Archean greenstone structures in the Baltic Shield
Geochronological ages of rocks in the Vedlozero - Segozero greenstone belt.
Rock and locality | Method | Age (Ma) | Reference |
Andesite, Palaselga stucture | Pb-Pb isochron whole-rock | 3000 | A.F.Loginov, 1982 |
Dacite, subvolcano, Koikary stucture | U-Pb (zircon) | 2935+/-20 | E.V.Bibikova, 1983 |
Andesidacite subvolcano, Ignoila, Hautavaara stucture | U-Pb (zircon) | 2995+/-20 | S.A.Sergeyev, 1989 |
Rhyolite dike, Ignoila, Hautavaara stucture | U-Pb | 2854+/-14 | S.A.Sergeyev, 1989 |
1. Introduction
2. Geology
3. Layered flows
4. Structures
5. Petrography
6. Geochemistry
7. Mantle sources
8. References
9. Researcher (Sergei Svetov)