Baltic Shield


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Baltic Shield,

the continental core of Europe, composed of Precambrian crystalline rock, the oldest of Europe. The tectonically stable region was not affected by the Caledonian, Hercynian, and Alpine mountain-building periods of Europe, although mountains did rise along the edges. The exposed portion of the Baltic Shield is found in Finland, Sweden, and Norway. During the Pleistocene epoch, great continental ice sheets scoured and depressed the shield's surface, leaving a thin covering of glacial material and innumerable lakes and streams. The ancient rocks have yielded a rich variety of minerals, especially iron and copper. In W former USSR the Russian Platform is that portion of the Baltic Shield buried beneath a great thickness of sedimentary rock.

Baltic Shield

 

a major structural uplift in the northwestern part of the Eastern European Platform, where its Pre-cambrian folded basement emerges on the surface, while the rock of the younger sedimentary mantle is almost completely absent. The Baltic Shield occupies the Karelian ASSR, Murmansk Oblast, and part of Leningrad Oblast in the USSR and Finland and Sweden. The highly metamorphosed and complexly dislocated Precambrian rock of the basement, which has been pierced by intrusions of an acid and basic composition, can be divided into a number of variously aged complexes which form the Precambrian folded systems. The Archean gneisses, the crystalline schists and intrusions (White Sea, Kola, and other complexes) have an absolute age of from 3.5 billion to 2.7–2.5 billion years. The younger Karelian and Svecofennian complexes of the Proteiozoic are widely developed; they were formed 1.85–1.75 billion years ago. Rapakivi granites also developed 1.64–1.62 billion years ago. On small areas, Upper Protero-zoic rock of the Jotnian age (1.4–1.3 billion years ago) has remained, and this occurs as the platform mantle.

On the Baltic Shield there are iron ore deposits (Kiruna and the Grangesberg region in Sweden, the Olenegorsk and Kovdor regions in the USSR), as well as copper-nickel ores (Monchetundra, the Pechenga region of the USSR); apatite deposits are associated with the Paleozoic alkali intrusions (Khibiny in the USSR).

REFERENCES

Kratts, K. O., N. Mangusson, A. Simonen, and O. Khol’tedal’. “Baltiiskii shchit.” Tektonika Evropy. Moscow, 1964.
Kratts, K. O., E. K. Gerling, and S. B. Lobach-Zhuchenko. “Geokhronologiia dokembriia. Baltiiskogo shchita.” Geologiia dokembriia. Leningrad, 1968. (Mezhdunarodnyi geologicheskii kongress. XXIII sessiia. Doklady sovetskikh geologov. Problema 4.)

M. F. MIKUNOV

References in periodicals archive ?
The Metsahovi (MEF) and Laitila (RAF) stations are located on the Baltic Shield, the Matsalu (MTSE) and Vasula (VSU) stations on the southern slope of the Baltic Shield, the Slitere (SLIT), Paberze (PABE) and Paburge (PBUR) stations on the East European Platform, within the Baltic Syneclise and the Suwalki (SUW) station lies at the border between the Baltic Syneclise and the Mazuro-Belorussian Anteclise.
For the stations located on the Baltic Shield (MEF and RAF), the HVSR curve has almost flat characteristics, with a step-by-step increase towards high frequencies (Fig.
On the geological structure of the crystalline basement of the southern slope of the Baltic Shield. Acta Comment.
Korja & Heikkinen (1995) as well as Puura & Floden (1999) suggested that the long-lasting voluminous AMCG magmatism at 1.65-1.50 Ga in the Baltic Shield and beneath the Baltic Sea could have been a result of decompressional melting caused by the extension of the lithosphere and thinning of the crust during post-collisional collapse in the latest Svecofennian.
The obtained 1625 [+ or -] 6 Ma magmatic crystallization age of the Velaiciai-2 granodiorite agrees well with the latest Palaeoproterozoic-early Mesoproterozoic extension of the crust and widespread AMCG and A-type granitoid magmatism in Estonia and Latvia as well as Finland and Sweden in the Baltic Shield. We suggest that all these processes, including the development of the EW-trending Telsiai deformation zone in Lithuania, represent a far-field feedback response of the Palaeoproterozoic continental crust to the Gothian orogeny at the SW margin of the East European Craton.
Continental growth by accretion: a tectonostratigraphic analysis of the evolution of the western and central Baltic Shield, 2.5 to 1.75 Ga.
On the geological age of the crystalline basement of the southern slope of the Baltic Shield (SSBS).
Interpretation of gravity anomalies along the POLAR Profile in the northern Baltic Shield. Tectonophysics, 162, 135-150.
An integrated geophysical interpretation of the 2000 km FENNOLORA section of the Baltic Shield. In The European Geotraverse: Integrative Studies (Freeman, R., Giese, P.
An outline of the Precambrian Evolution of the Baltic Shield. Precambrian Research, 35,15-52.
On the geological structure of the crystalline basement of the southern slope of the Baltic Shield. Acta et Commentationes Universitatis Tartuensis, 972, 16-39.

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