Baltic shield

Porcelli D, Andersson PS, Baskaran M, Wasserburg GJ (2001) Transport of U- and Th-series nuclides in a Baltic Shield watershed and the Baltic Sea. Geochim Cosmochim Acta 65 2439-2459 Puls RW, Powell RM (1992) Acquisition of representative ground-water quality samples for metals. Ground Water Monitor Remediat 12 167-176... 

Table 9.31 Determination of rare earth elements in Precambrian zircon and monazite from Baltic Shield by SSMS (concentration in Pgg-1,)36.

An age of 2000-2700 m.y. has been established for the iron cherts of the Bazavluk zone of the Ukrainian shield, the Olenogorsk deposit on the Baltic shield, the Singhbum deposit in India, and the Algoma-type BIF of the Lake Superior area. 

On the Baltic shield, BIF are known in three major structural-facies zones the Karelian zone of the Karelides the Kola-Norwegian zone of the Kare-lides, and the vast zone of the Svecofennides in the southwestern part of the shield. The first two zones are separated by the Belomorides, which most investigators consider to be older than the Karelides. (Polkanov, 1939 Chernov et al., 1970). The question of the age relationships of the Svecofennides of Sweden and Finland to the Karelides is in dispute. 

Despite the diversity of the BIF and the complexity of their interrelationships with the enclosing rocks, some general features have been established. In a detailed formational analysis, Chernov showed that the cherty iron-formations constitute the lower parts of the sections both in the Karelides and in the Svecofennides, and that their formation reflects the initial stages of geosynclinal development of the Baltic shield. In many areas the BIF are underlain by thick piles of conglomerates which rest on an old basement more than 2600 m.y. old. The BIF are overlain by volcanic rocks of the spilite-diabase series or by clastic flyschoid formations formed in the final stages of geosynclinal development. 

Chernov et al. (1970), who studied the cherty iron-formations of Karelia, concluded that they are related to volcanism not only of basic, but mainly also of acid composition. In turn, on the basis of the composition of the parent lavas, they distinguished spilite-diabase and leptite-porphyry formations among those of eugeosynclinal type, formed simultaneously but in different paleotectonic conditions. A large part of the formations of the spilite-diabase series of the Baltic shield is confined to the junctions between geosynclinal depressions and central massifs. The leptite-porphyry series of geosynclinal formations is characterized by a close association of acid and basic volcanics with iron cherts and less often with limestones and clastic sediments (Fig. 9). 

Puchtel I. S., Hofmann A. W., Mezger K., Jochum K. P., Shchipansky A. A., and Samsonov A. V. (1998) Oceanic plateau model for continental crustal growth in the Archaean a case study from the Kostomuksha greenstone belt, NW Baltic Shield. Earth Planet. Sci. Lett. 155, 57-74. 

Puchtel I. S., Brilgmann G. E., and Hofmann A. W. (1999) Precise Re-Os mineral isochron and Pb-Nd-Os isotope systematics of a mafic-ultramafic sill in the 2.0 Ga Onega plateau (Baltic Shield). Earth Planet. Sci. Lett. 170, 447-461. 

Puchtel I. S., Briigmann G. E., Hofmann A. W., KuMkov V. S., and Kulikova V. V. (2001b) Os isotope systematics of komatiitic basalts from the Vetreny belt, Baltic Shield evidence for a chondritic source of the 2.45 Ga plume. Contrib. Mineral. Petrol. 140, 588-599. 

S. Norway 12-13 1.5-2.0Ga Baltic Shield, (2) 35 Unknown Quartzofeldspathic gneiss, amphibolite, metasediments Felsic granulite, mafic granulite, metasediments... 

Kempton P. D., Downes H., Sharkov E. V., Vetrin V. R., Ionov D. A., Carswell D. A., and Beard A. (1995) Petrology and geochemistry of xenoliths from the northern Baltic shield evidence for partial melting and metasomatism in the lower crust beneath an Archaean terrane. Lithos 36 (3—4), 157-184. 

Luosto U. and Korhonen H. (1986) Crustal structure of the baltic shield based on off-fennolora refraction data. Tectonophysics 128, 183-208. 

Mean heat production. Standard deviation on the heat produetion distribution. Number of sites. Analyses were made on mixed powders, implying that the standard deviation of the analyses underestimates the true spread of values for individual rock samples. Average calculated by weighting according to the abundances of the different rock types. Baltic Shield data compiled from Hanski (1992), Eilu (1994),... 

Shaw et al, 1994), the Baltic Shield (Joeleht and Kukkonen, 1998), and the Indian Shield (Roy and Rao, 2000). Nevertheless, these efforts remain limited to a few exceptional areas (Rudnick and Fountain, 1995). One outstanding problem is that the lowermost crust cannot be sampled directly, except perhaps in the Ivrea Zone, Italy, or in the Kohistan arc, Pakistan (Miller and Christensen, 1994). In seismic Shield models, the lowermost crust, identified by seismic P-wave velocities in the range 6.8-7.2kms makes up 16 km out of 45 km of the crustal column (Durrheim and Mooney, 1991 Christensen and Mooney, 1995). This large fraction of the crust remains elusive. 

Kremenentsky A. A., Milanovsky S. Y., and Ovchinnikov L. N. (1989) A heat generation model for the continental crust based on deep drilling in the Baltic Shield. Tectonophysics 159, 231-246. 

Sumozero-Kenozero Belt Baltic Shield 3.0-2.8 Puchtel et al (1999)... 

Onega Plateau Baltic Shield 1.98 Puchtel et al (1998a)... 

Puchtel I. S., Arndt N. T., Hofmann A. W., Haase K. M., Kroner A., Kulikov V. S., Kulikova V. V., Garbe Schonberg C. D., and Nemchin A. A (1998a) Petrology of mafic lavas within the Onega plateau, central Karelia evidence for 2.0 Ga plume-related continental crustal growth in the Baltic Shield. Contrib. Miner. Petrol. 130, 134-153. 

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