On the Karelides in the Tohmajärvi area, eastern Finland
The evolution of the Karelides in the Tohmajärvi area is discussed. The Karelidic schists (metasediments) are devided into two stratigraphic groups, the Jatulian and the Kalevian, which likewise represent two different sedimentation facies. The Jatulian metasediments are so-called evolutionary sedim...
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| Format: | Article |
| Language: | English |
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Geological Society of Finland
1971-06-01
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| Series: | Bulletin of the Geological Society of Finland |
| Online Access: | http://www.geologinenseura.fi/bulletin/Volume43/sgs_bt_043_1_pages_093_108.pdf |
| Summary: | The evolution of the Karelides in the Tohmajärvi area is discussed. The Karelidic schists (metasediments) are devided into two stratigraphic groups, the Jatulian and the Kalevian, which likewise represent two different sedimentation facies. The Jatulian metasediments are so-called evolutionary sediments, deposited under relatively peaceful conditions in marginal parts of the continental block, partly in a shallow transgressive sea. These continental-epicontinental sediments were originally weathering gravel, quartz sands, bituminous and calcareous sediments, which were metamorphosed into metaconglomerates, quartzites, black schists and dolomites. The Kalevian metasediments are revolutionary sediments, chemically weakly weathered and mixed with sand and clay, which deposited rather rapidly into fold basins formed during orogenic movements. They are so-called flysch (Wegmann 1928, 1929) sediments and form the phyllite — mica schist group. Besides the normal metasediments, the Jatulian group comprises pyroclastic sediments and hypabyssic and metabasaltic effusives which erupted during the initial stages of the Svecofenno-Karelidic orogeny. In the southern part of the schist area there are smaller Late-Karelidic granite intrusions which together with the orogenic movements caused regional metamorphism under conditions of amphibolite facies where staurolite and andalusite porphyroblasts crystallized in mica schists and phyllites.
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| ISSN: | 0367-5211 1799-4632 |