The Archean of the Baltic Shield: Geology, Geochronology, and Geodynamic settings

Geotectonics (Impact Factor: 0.71). 01/2006; 40(6):409-433. DOI: 10.1134/S001685210606001X

ABSTRACT The Archean provinces and lithotectonic complexes of the Baltic (Fennoscandian) Shield are considered. The supracrustal complexes
are classified by age: <3.2, 3.10–2.90, 2.90–2.82, 2.82–2.75, and 2.75–2.65 Ga. The data on Archean granitoid complexes and
metamorphic events are mentioned briefly, whereas the recently found fragments of the Archean ophiolitic and eclogite-bearing
associations are discussed in more detail. The Paleoarchean rocks and sporadic detrital grains of Paleoarchean zircons have
been found in the Baltic Shield; however, the relatively large fragments of the continental crust likely began to form only
in the Mesoarchean (3.2–3.1 Ga ago), when the first microcontinents, e.g., Vodlozero and Iisalmi, were created. The main body
of the continental crust was formed 2.90–2.65 Ga ago. The available information on the Paleoarchean complexes of the Baltic
Shield is thus far too scanty for judgment on their formation conditions. The geologic, petrologic, isotopic, and geochronological
data on the Meso-and Neoarchean lithotectonic complexes testify to their formation in the geodynamic settings comparable with
those known in Phanerozoic: subduction-related (ensialic and ensimatic), collisional, spreading-related, continental rifting,
and the setting related to mantle plumes.

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    ABSTRACT: References Cited in Mints, M.V., et al., East European Craton: Early Precambrian History and 3D Models of Deep Crustal Structure: Geological Society of America Special Paper 510
    East European Craton: Early Precambrian History and 3D Models of Deep Crustal Structure, Special Paper 510 (in press) edited by GSA Books Science Editors: Kent Condie and F. Edwin Harvey, 04/2015: chapter References Cited: pages 403-433; The Geological Society of America (GSA).
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    ABSTRACT: New age constraints from detrital zircon U-Pb geochronology from clastic sediments and diamict deposits obtained maximum depositional ages for the Seidorechka and Polisarka Sedimentary formations of the Imandra-Varzuga Greenstone Belt of theKola Province, NW-Russia. These delimit the deposition of Palaeoproterozoic Huronian-age glacial deposits of the Fennoscandian Shield from c. 2430 Ma to <2411 Ma. The time constraint allows comparison to the first two of three possible glacial intervals recognized in the Huronian Supergroup, Canada, and South African diamict deposits. Intercontinental comparisons support these constraints, the assumption of a glacial origin of the diamictites and, further, the eventually global extent of the event.Similar age distributions and depositional ages of c. 2400 Ma within the Neverskrukk Formation of the Pechenga Greenstone Belt support a correlation with the Imandra-Varzuga Greenstone Belt succession, which was traditionally based on lithostratigraphic observations. The detrital zircon age spectra of eight analysed samples show an Archaean dominance and reoccurring peaks around 2800-2750 Ma,which indicate similar origins for the zircons. Such peaks are corroborating with a major global crustal generation event being recorded in detrital zircon spectra worldwide. Additionally, certain age populations around 2440 Ma and 2500 Ma are present andindicate a correlation with intrusive magmatism that affected the region at that time and support a correlation based on overlapping age distributions
    Precambrian Research 06/2014; 246. DOI:10.1016/j.precamres.2014.03.014 · 6.02 Impact Factor
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    ABSTRACT: Based on relationships between Paleoproterozoic mafic dykes, lithotectonic complexes, and tectonic structures of the Gridino Zone in the Belomorian eclogite province of the Fennoscandian Shield, deformations have been divided into groups differing in age and the succession of tectonic events has been reconstructed. The formation of Neoarchean eclogite-bearing melange was related to disintegration of large eclogite sheets in the course of near-horizontal ductile flow accompanied by syntectonic granitoid magmatism, multiple migmatization, and granulite-to amphibolite-facies metamorphism. The exotic blocks, including eclogites, were incorporated into TTG gneisses as sheets and lenses up to a few hundreds of meters in thickness and oriented conformably with gneissic banding. As a result of ductile flow, the lithotectonic complexes were transported at the level of discrete brittle-ductile deformations expressed as strike-slip faults and associated folds. Under conditions of a relatively rigid medium, individual structural elements underwent rotation approximately through 90A degrees in plan view. Under the extension regime in the Early Paleoproterozoic, several swarms of mafic dykes were injected into the already cold framework rocks, as is evident from dyke morphology. The dykes crosscut all predated structures, included turned blocks, and are therefore important reference points for subdivision of Neoarchean and Paleoproterozoic processes. The Svecofennian postdyke tectonic activity was accompanied by local shearing and boudinage of metabasic rocks, development of quartz and pegmatite veins along tension cracks, disharmonic folding, and discrete retrograde metamorphism up to amphibolite-facies conditions. The postdyke deformations did not exert a substantial effect on the previously formed regional structure.
    Geotectonics 07/2014; 48(4-4):313-326. DOI:10.1134/S0016852114040025 · 0.71 Impact Factor


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Dec 28, 2014