| 1. |
- Arkhipov, Victor P., et al.
(författare)
-
Dynamic and structural properties of oxyethylated isononylphenols
- 2016
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Ingår i: Mendeleev communications (Print). - : Elsevier BV. - 0959-9436 .- 1364-551X. ; 26:4, s. 355-357
-
Tidskriftsartikel (refereegranskat)abstract
- Diffusion coefficients, dielectric relaxation times and refraction coefficients were measured, and activation energies of translational and rotational mobilities were determined for a series of oxyethylated phenols (neonols AF9-n) p-C9H19C6H4-O(CH2CH2O)nH, n = 4, 6, 8, 9, 10, 12, at different temperatures. The results demonstrated the existence of contraction and transition phenomena that changed the structure of neonol molecules at n ∼ 9 from a zigzag to a meander form.
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| 2. |
- Bibikova, EV, et al.
(författare)
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Evolution of the Belomorian Belt: NORDSIM U-Pb zircon dating of the Chupa paragneisses, magmatism, and metamorphic stages
- 2004
-
Ingår i: Petrology. - 1556-2085. ; 12:3, s. 195-210
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Tidskriftsartikel (refereegranskat)abstract
- The U-Pb systematics of accessory zircons were studied by secondary ion mass spectrometry (NORDSIM ion microprobe). This study revealed two main age groups of terrigenous zircons, 3000 and 2900 Ma, in the metasedimentary rocks of the Chupa nappe of the Belomorian belt. Zircon older than 3200 Ma was not found, which is consistent with the available Sm-Nd model ages. Older terrigenous zircons (3100-3200 Ma) were found only in the northern part of the belt, which is probably a consequence of the input of Mesoarchean material from the Karelian craton and/or the Kola province. The oldest metamorphic zircons of Belomorian paragneisses were formed 2820 +/- 15 Ma ago. Zircons with an age of 2710 15 Ma provide a record of collisional metamorphism of the high-pressure granulite, eclogite, and amphibolite facies, which was completed by several magmatic and migmatitic events 2615 +/- 15 Ma ago. The basic magmatism of 2450-2400 Ma did not produce accessory zircons in the supracrustal complexes of the Belomorian belt. In contrast, the later Svecofennian metamorphism of the amphibolite facies resulted in the reequilibration of the U-Pb isotopic system of sphene and growth of a new zircon generation, especially in the zones of migmatization and pegmatite formation between 1900 and 1800 Ma. Early Proterozoic tectonothermal processes only partially obliterated the record of the Archean history of the Belomorian belt, which does not prevent the reconstruction of Archean tectonic settings. New more accurate isotopic data supported the previously proposed geodynamic model of the evolution of the Belomorian belt. According to this model, its formation occurred under the influence of oceanic crust subduction 2900-2800 Ma ago and subsequent collision with the Karelian craton 2730-2710 Ma ago.
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| 3. |
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| 4. |
- Bibikova, E. V., et al.
(författare)
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Sarmatia-Volgo-Uralia junction zone: Isotopic-geochronologic characteristic of supracrustal rocks and granitoids
- 2009
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Ingår i: Stratigraphy and Geological Correlation. - 0869-5938. ; 17:6, s. 561-573
-
Tidskriftsartikel (refereegranskat)abstract
- The geochronologic (U-Pb isotopic system of zircons) and isotopic-geochemical (Sm-Nd isotopic system of the bulk rock) studies were performed along the profile extending from the eastern Sarmatia (in the west) to the Middle Volga megablock of Volgo-Uralia (in the east), i.e., across the entire junction zone for dating the integration of Sarmatia and Volgo-Uralia, representing two segments of the East European Craton. It is established that the examined rocks are characterized by the Paleoproterozoic Nd isotopic model age, which varies from 2.1 and 2.4 Ga, except for some samples indicating a similar age of the crust through the entire Sarmatia-Volgo-Uralia junction zone. The highly metamorphosed complexes of the granulite and amphibolite facies constituting the southwestern margin of Volgo-Uralia are Paleoproterozoic, not Archean, in age, contrary to previous views. Two Early Paleoproterozoic lithotectonic complexes are defined in Volgo-Uralia: South Volga metasedimentary and Tersa metasedimentary-volcanogenic. The obtained data confirm the asynchronous integration of individual segments into the East European Craton: the integration of Sarmatia and Volgo-Uralia approximately 2100-2000 Ma ago was followed by the conjunction of this newly-formed continent with Fennoscandia ca. 1800 Ma ago.
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| 5. |
- Bibikova, E. V., et al.
(författare)
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The early crust of the Volgo-Uralian segment of the East European Craton: Isotope-geochronological zirconology of metasedimentary rocks of the Bolshecheremshanskaya Formation and their Sm-Nd model ages
- 2015
-
Ingår i: Stratigraphy and Geological Correlation. - 0869-5938. ; 23:1, s. 1-23
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of isotope-geochronological study of metasedimentary rocks of the Bolshecheremshanskaya Formation of the Volgo-Uralian segment of the East European Craton carried out to identify their protoliths. 16 samples of high-alumina gneisses from well cores were studied using the Sm-Nd isotope method and T-Nd(DM) model ages. Accessory zircons were selected from rocks with the most ancient model ages (more 3.2 Ga) in three wells: Minnibaevskaya 20000, Novo-Elkhovskaya 20009, and Zai-Karatayskaya 12930 in South Tatarstan. The isotope U-Pb dating of 200 zircon grains was performed on a Cameca 1280 NORDSIM secondary ion mass spectrometer at the Natural History Museum (Stockholm, Sweden). The most applicable sites for analysis of zircon crystals were pre-selected based on cathodoluminescence images. The analytical results demonstrate the diversity of zircon groups in age from 3.8 to 2.6 Ga and together with geochemical features of metasedimentary rocks of the Bolshecheremshanskaya Formation suggest the heterogeneous composition and age of provenance areas under denudation. Occurrence of Eoarchean and Paleoarchean zircons in the clastic material of the protolith of the Bolshecheremshanskaya gneisses indicates the existence of Early Archean crustal terrains in Volgo-Uralia.
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| 6. |
- Bogdanova, Svetlana, et al.
(författare)
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Assembly and Breakup of Rodinia (Some results of IGCP project 440)
- 2009
-
Ingår i: Stratigraphy and Geological Correlation. - 0869-5938. ; 17:3, s. 259-274
-
Forskningsöversikt (refereegranskat)abstract
- The principal results of project 440 "Assembly and Breakup of Rodinia" of the International Geological Correlation Programme (IGCP) are reviewed in this work. A map of that supercontinent compiled using geological and paleomagnetic data describes global paleogeography 900 Ma ago. The assembly of Rodinia, which comprised most of Precambrian continental blocks, lasted ca. 400 m.y. (from 1300 to 900 Ma). Its breakup presumably triggered by mantle superplume took place between 830 and 650 Ma. The correlation between tectonic events in different continental blocks is considered. Some problems concerning the Rodinia reconstruction and history, e.g., the slow growth of juvenile crust and effects of mantle-plume events during the amalgamation period and of glaciations at the breakup time, are discussed. The latter caused changes in the biosphere and climate, whereas postglacial periods stimulated progress in biota evolution.
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| 7. |
- Bogdanova, Svetlana, et al.
(författare)
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Danopolonian migmatization of Mesoproterozoic sedimentary rocks in southernmost Sweden: a SIMS zircon study
- 2014
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Ingår i: GFF. - : Informa UK Limited. - 2000-0863 .- 1103-5897. ; 136:2, s. 410-428
-
Tidskriftsartikel (refereegranskat)abstract
- To assess the age and origin of the metasedimentary migmatites in southernmost Sweden and their relationships with the Mesoproterozoic granitoid magmatism in the area, we have dated migmatite zircon using the secondary ion mass spectrometry U-Pb method. The studied metasedimentary migmatites, here called the Noteboda migmatites, occur along the southwestern boundary of the 1442 Ma Taghusa granitoid intrusion in southeastern Skane. They contain the mineral assemblage garnet + biotite +/- muscovite + cordierite + sillimanite + quartz + plagioclase + K-feldspar and were formed during a retrograde evolution from c. 750-720 degrees C and 6 kbar (peak conditions) to c. 675 degrees C and 4 kbar. Zircon is characterized by detrital cores surrounded by U-rich rims and overgrowths. Separate rounded metamorphic grains also exist. The age probability-density distribution peaks for detrital zircon are at c. 1700, 1670, 1650, 1610, 1570 and 1530 Ma. These ages suggest Gothian orogenic rocks in the present west as the most probable principal source. Sedimentation occurred after c. 1530 Ma, the age of the youngest detrital zircon, indicating the existence of a previously unknown period of Mesoproterozoic sedimentation in southernmost Sweden. A homogeneous zircon overgrowth yielded a concordant Pb-207/Pb-206 age of 1439 +/- 5 Ma, which dates the migmatization and is close to the age of the Taghusa intrusion. We conclude that the burial of the sediments down to c. 20 km, their metamorphism and progressive migmatization took place concurrently with granitic magmatism, NE-SW compression, folding and shearing of the crust between 1460 and 1440Ma during the Danopolonian orogeny.
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| 8. |
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| 9. |
- Bogdanova, Svetlana, et al.
(författare)
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Late Palaeoproterozoic mafic dyking in the Ukrainian Shield of Volgo-Sarmatia caused by rotation during the assembly of supercontinent Columbia (Nuna)
- 2013
-
Ingår i: Lithos. - : Elsevier BV. - 0024-4937. ; 174, s. 196-216
-
Tidskriftsartikel (refereegranskat)abstract
- The Ukrainian Shield comprises the exposed crust of the large Palaeoproterozoic protocraton Volgo-Sarmatia, which together with the Fennoscandian crustal segment constitutes the East European Craton ("Baltica"). Geological and geophysical data indicate that 1.80 to 1.75 Ga mafic dykes related to anorthosite-mangerite-charnockite-granite (AMCG) plutons are widespread within the Ukrainian Shield. We examined their ages, distribution patterns, orientations and compositions in three different crustal blocks (Volyn, Ingul and Azov), and found close spatial relationships with major strike-slip fault systems developed during two phases of extension. The early, 1.80-1.77 Ga, generation of mafic dykes mostly follows NW (330 +/- 20 degrees) and more rarely N-S- or E-W-trending faults corresponding to major NE-SW extension (the Submoshorino phase). These dykes contain olivine dolerites, picrites, camptonites, lamprophyres, kimberlites and other rocks belonging to tholeiitic and subalkaline jotunitic series. The compositions of these dykes differ between the host blocks, but all feature upper mantle geochemical signatures such as high contents of Ni and Cr, and positive values of epsilon Nd-(1800) up to + 2.8. High degrees of REE fractionation indicate deep levels of mantle melting, which is particularly characteristic of the Ingul block as marked by the most extensive and dense mafic dyke swarms. The later, 1.76-1.75 Ga, dyke swarms occur close to the most voluminous AMCG suites of similar age and were emplaced during the second (Korsun) phase of faulting when all the older strike-slip fault zones were reactivated and partly transformed to tensional faults by E-W extension. These dyke swarms mainly trend 030 +/- 20 degrees. They are jotunitic and their isotopic signatures indicate a greater participation of crustal sources in the parent melts. The overall transtensional tectonic setting of the mafic dyking associated with the AMCG magmatism in Volgo-Sarmatia was created by convergent tectonics and postcollisional collapse of the thickened lithosphere, as well as by mantle delamination coupled with the rotation of Volgo-Sarmatia between 1.80 and 1.75 Ga. This agrees with palaeomagnetic reconstruction suggesting rotation(s) of Volgo-Sarmatia during its protracted oblique docking with Fennoscandian terranes and Laurentia as supercontinent Columbia (Nuna) was assembled. (C) 2012 Elsevier B.V. All rights reserved.
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| 10. |
- Bogdanova, Svetlana, et al.
(författare)
-
MEMOTATUR in SE Fennoscandia
- 2010
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Ingår i: [Publication information missing]. ; Record 2010/24, s. 26-26
-
Konferensbidrag (refereegranskat)
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| 11. |
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| 12. |
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| 13. |
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| 14. |
- Bogdanova, Svetlana, et al.
(författare)
-
The 1.80-1.74-Ga gabbro-anorthosite-rapakivi Korosten Pluton in the Ukrainian Shield: a 3-D geophysical reconstruction of deep structure
- 2004
-
Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951. ; 381:1-4, s. 5-27
-
Tidskriftsartikel (refereegranskat)abstract
- The deep structure of the gabbro-anorthosite-rapakivi granite ("AMCG-type") Korosten Pluton (KP) in the northwestern Ukrainian Shield was studied by 3-D modelling of the gravity and magnetic fields together with previous seismic data. The KP occupies an area of ca. 12,500 km(2) and comprises several layered gabbro-anorthositic intrusions enveloped by large volumes of rapakivi-type granitoids. Between 1.80 and 1.74 Ga, the emplacement of mafic and associated granitoid melts took place in several pulses. The 3-D geophysical reconstruction included: (a) modelling of the density distribution in the crust using the observed Bouguer anomaly field constrained by seismic data on Moho depth, and (b) modelling of the magnetic anomaly field in order to outline rock domains of various magnetisation, size and shape in the upper and lower crust. The density modelling was referred to three depth levels of 0 to 5, 5 to 18, and 18 kin to Moho, respectively. The 3-D reconstruction demonstrates close links between the subsurface geology of the KP and the structure of the lower crust. The existence of a non-magnetic body with anomalously high seismic velocity and density is documented. Most plausibly, it represents a gabbroic stock (a parent magma chamber) with a vertical extent of ca. 20 km, penetrating the entire lower crust. This stock has a half-cylindrical shape and a diameter of ca. 90 kin. It appears to be connected with a crust-mantle transitional lens previously discovered by EUROBRIDGE seismic profiling. The position of the stock relative to the subsurface outlines of the KP is somewhat asymmetric. This may be due to a connection between the magmatism and sets of opposite-dipping faults initially developed during late Palaeoproterozoic collisional deformation in the Sarmatian crustal segment. Continuing movements and disturbances of the upper mantle and the lower crust during post-collisional tectonic events between 1.80 and 1.74 Ga may account for the long-lived, recurrent AMCG magmatism.
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| 15. |
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| 16. |
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| 17. |
- Bogdanova, Svetlana, et al.
(författare)
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Trans-Baltic Palaeoproterozoic correlations towards the reconstruction of supercontinent Columbia/Nuna
- 2015
-
Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 259, s. 5-33
-
Tidskriftsartikel (refereegranskat)abstract
- A comparative study of the central and southern parts of the Palaeoproterozoic Svecofennian orogen in the Baltic/Fennoscandian Shield and the platform area to the east and south of the Baltic Sea indicates that at least these parts of the orogen are built up of several NW-SE trending, 100-300 km wide tectonic megadomains separated from each other and complicated by major zones of mostly dextral shearing. The generation of these zones occurred successively between 1.86 and 1.75 Ga, concomitantly with continuing crustal accretion younging towards the southwest. Even considering the distorting presence of a number of microcontinents, this indicates the one-time existence and repeated episodic activity of a master subduction zone stepwise falling back to the present south-southwest. At 1.82-1.80 Ga, the oblique collision of protocontinents Volgo-Sarmatia and Fennoscandia interfered with the accretionary growth of the crust in the Svecofennian orogen. In the west, the system of Svecofennian tectonic domains and shear zones is delimited by 1.70-1.55 Ga orogenic belts marking the Laurentia-Greenland-Baltica margin of Columbia. Altogether, the available U-Pb zircon datings and studies of key rocks and structures in the South Baltic region allow more detailed Trans-Baltic correlation and the creation of new integrated models of the structural and tectonic evolution of the Svecofennian orogen in particular and northern Europe in general. The new findings will be important also in the continuing study of supercontinent formation and supercontinent cycles, and the drifting of Palaeoproterozoic protocontinents during the assembly of Columbia/Nuna. (C) 2014 Elsevier B.V. All rights reserved.
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| 18. |
- Bogdanova, Svetlana V., et al.
(författare)
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Palaeoproterozoic reworking of early Archaean lithospheric blocks : Rocks and zircon records from charnockitoids in Volgo-Uralia
- 2021
-
Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 360
-
Tidskriftsartikel (refereegranskat)abstract
- The Volgo-Uralia segment, which constitutes one fourth of the East European Craton, is covered by sedimentary deposits. From geophysical studies and examination of thousands of drillcores, Volgo-Uralia has been recognised as a vast high-grade terrain with a complex crustal history extending from the Palaeoarchaean to the Palaeoproterozoic. Our recent studies are focused on the search for the oldest crust formation event by extracting whole rock Sm-Nd and zircon U-Th-Pb and Lu-Hf isotope information from samples recovered by drilling in southern Volgo-Uralia. Particular attention is devoted to the Kolyvan charnockitoid rock suite, which makes up several large areas of gneisses and granitoids of enderbite, charnockite and tonalite composition. The zircon from the granitoids show complex internal structures and consists of large magmatic cores with oscillatory zoning, surrounded by CL black-and-bright bands of metamorphic rims. The crystallisation age of the cores is defined as 3140 ± 7 Ma (SHRIMP) and 3127 ± 46 Ma (LA-ICPMS), while the CL-bright rims are dated at 1950 ± 25 Ma (LA-ICPMS). The ingressive recrystallisation of primary magmatic zircon correlates with depletion in REE, which is observed in each studied core-rim pair. No differences in O-isotopic compositions have been detected between the cores and the rims. δO18 values with an average of 5.8 ± 0.3‰ (1SD) implying that no supracrustal rocks were involved in the source of the Kolyvan melts. The Hf-isotope compositions of magmatic cores (−3 to −9 εHfT) and metamorphic rims (−14 to −28 εHfT), and their similar crustal model ages from 3.42 to 3.86 Ga indicate Eo- to Palaeoarchaean crustal sources for the charnockitic magmas. Sm-Nd model ages of ca 3.46 Ga for the Kolyvan rocks are consistent with the zircon Hf-isotope data and indicate a long crustal prehistory of a source of the Mesoarchaean magmas. We conclude that the Mesoarchaean Kolyvan suite rocks was formed by reworking of Eo- to Palaeoarchaean lithosphere, which probably had been widespread throughout Volgo-Uralia. The obtained geochemical and isotope data can be reconciled in a model of deep mantle-plume activity at 3.1 Ga causing mantle underplating, extension of the Palaeoarchaean crust and high-T magmatism.
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| 19. |
- Bogdanova, Svetlana, et al.
(författare)
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Volgo-Uralia: The First U-Pb, Lu-Hf and Sm-Nd Isotopic Evidence of Preserved Paleoarchean Crust
- 2010
-
Ingår i: American Journal of Science. - : American Journal of Science (AJS). - 0002-9599. ; 310:10, s. 1345-1383
-
Tidskriftsartikel (refereegranskat)abstract
- The crustal segment Volgo-Uralia is the least known part of the East European Craton. Its crystalline crust is hidden beneath a thick Neoproterozoic to Phanerozoic cover but disclosed by thousands of drill holes. In conjunction with the recent "Tatseis" reflection seismic profile, we conducted the first isotopic study of the Bakaly granitoid block in eastern Volgo-Uralia, which represents a subsurface section of the layered upper-middle crust. The study included whole-rock Sm-Nd and ion-probe zircon U-Th-Pb (SIMS) and Lu-Hf (LA-ICPMS) analyses of granitoids from seven drill cores. The Bakaly block was also targeted because its rocks have never been subjected to granulite facies metamorphism, making it possible to date pristine, pre-metamorphic zircon. Our study showed that the four principal suites of granitoids in the Bakaly block are different in age, each corresponding to a particular stage of Archean crustal evolution between 3.3 and 2.6 Ga. The Tashliar monzonitic suite, belonging to an alkaline series yielded zircon ages of 3.3 and 3.2 Ga, which are the oldest ages yet found in Volgo-Urafia. The epsilon(Hf)(T) values of the dated zircon and the epsilon(Nd)(T) values of their host rocks indicate that a Paleo- to Eoarchean protolith with model T-DM ages up to 3.8 Ga had been involved in the formation of the Tashliar melts. Three Neoarchean rock suites, one comprising quartz dioritic and tonalitic gneisses (the Bak 1), another K-rich granodiorites, granites and migmatites (the Bak 2), and the third monzonitic granitoids (the Aktanysh suite) were formed sequentially between 2.72 and 2.60 Ga. The 2.72 Ga Bak 1 suite is chemically diverse. It includes granitoids of the TTG type related to slab/subduction melts as well as rocks formed by the re-melting of older crust with whole-rock Nd T-DM and Hf T-DM model ages of 3.4 to 3.2 Ga. The 2.69 to 2.65 Ga Bak 2 suite was probably associated with a major collisional event, which defined the stacked structure of the Archean crust in Volgo-Uralia and its seismic layering. Our data suggest that the Bak 2 melts originated partly from juvenile sources with epsilon(Hf)(T) zircon values up to +4.8, as well as mixed crustal and juvenile mantle materials. Some crustal contamination of the melts appears to have occurred as evidenced by incorporated xenocrystic zircon. The chemical compositions of Bak 2 granitoids from the different plutons, their zircon epsilon(Hf) values, and the Hf- and Nd T-DM ages all mirror a heterogeneous, collisional, crustal structure. During post-collisional extension at 2.6 Ga, the intrusion of Aktanysh monzonitic granitoids took place. These rocks also bear evidence of a long crustal pre-history with Nd and Hf T-DM model ages of 3.3 to 3.5 Ga. The Aktanysh rocks are coeval with the Tuymazy gabbro-norite-anorthosite intrusions, which are widely distributed along post-collisional shear zones in the Bakaly block. They could have provided the heat necessary to melt the crust at this stage. Altogether, the isotopic evidence suggests several episodes of crustal growth and recycling possibly reaching back to 3.6 and 3.8 Ga. Metamorphic zircon rims show that the Archean crust in the Bakaly block were subjected to several tectonothermal overprints in the Paleoproterozoic between 2.4 and 1.9 Ga ago.
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| 20. |
- Cecys, Audrius, et al.
(författare)
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The Stenshuvud and Taghusa granitoids: new representatives of Mesoproterozoic magmatism in southern Sweden
- 2002
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Ingår i: GFF. - 2000-0863. ; 124, s. 149-162
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Tidskriftsartikel (refereegranskat)abstract
- New sites of Mesoproterozoic granitoid magmatism in southern Sweden have been discovered by recent fieldwork and U-P zircon age determination. In the area around Stenshuvud, in eastern Skane, granitic melts were intruded into country-rock gneisses of unknown age at c. 1450 Ma. The 1458 6 Ma Stenshuvud intrusion is composed of several rock varieties including quartz monzonite, tonalite, monzogranite, and late aplites. The Stenshuvud granitoids proper have glomeroporphyritic textures defined by monomineralic aggregations of feldspar or quartz and polymineralic aggregations of amphibole, biotite and magnetite. At 1442+/-9 Ma, the Taghusa granites were intruded along the contact between the Stenshuvud granitoids and the country-rock gneisses. These granites have streaky appearances, which are due to the presence of short, sub-parallel mafic mineral aggregations. The subsequent intrusion of leucogranites as cross-cutting veins and small bodies was the last phase of the entire magmatic event. All these granitoids appear to be co-genetic and belong to a metaluminous to marginally peraluminous, ferro-potassic, high-K calc-alkaline to shoshonitic sequence. Trace elements indicate similar source materials for both principal intrusions. An epsilon(Nd)-value of -0.6 and a T-DM model age of 1.85 Ga indicate involvement of older crustal materials in the generation of the melt(s). The studied granitoids feature both I- and A-type characteristics but are not typical of either type. While the Stenshuvud granitoids were intruded during NE-SW compressional stress that caused shearing an folding, the Taghusa granites are post-compressional and show no solid-state deformation.
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| 21. |
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| 22. |
- Johansson, Ake, et al.
(författare)
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A revised geochronology for the Blekinge Province, southern Sweden
- 2006
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Ingår i: GFF. - 2000-0863. ; 128, s. 287-302
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Tidskriftsartikel (refereegranskat)abstract
- Zircon grains from nine samples of metavolcanic rocks, gneisses, granitoids and migmatites from the Blekinge Province in southeasternmost Sweden have been dated by U-Pb using ion microprobe. The results suggest that most of the Blekinge bedrock was formed within a narrow time interval of 1.77-1.75 Ga, including the Vastana supracrustal formation and 'coastal gneisses' previously dated to c. 1.70 Ga. One sample, the 1.81 Ga Nattraby gneissic granite, appears to represent a sliver of slightly older proto-crust. An age of c. 1.75 Ga for an aplitic granite crosscutting the deformed Tving granitoids in eastern Blekinge brackets their deformation to between 1.77 and 1.75 Ga, whereas zircon grains of similar age from a migmatite neosome at Lindo may be inherited, making the result inconclusive. Thin metamorphic zircon overgrowths and resetting of the U-Pb system in titanite indicate a regional tectonothermal event at 1.45 to 1.40 Ga, accompanying the intrusion of the Karlshamn-type granites. The crust of the Blekinge Province thus was formed at 1.77-1.75 Ga from relatively juvenile sources in a subduction-related environment along the southern edge of Fennoscandia. It was deformed and partly uplifted relative to the undeformed TIB-1 granitoids of the Smaland block further north, prior to the intrusion of the Karlshamn-type granites at 1.45 Ga.
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| 23. |
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| 24. |
- Li, Z. X., et al.
(författare)
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How not to build a supercontinent: A reply to JDA Piper
- 2009
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 174:1-2, s. 208-214
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The hypothesized existence of a Neoproterozoic supercontinent called Rodinia is based on a series of geological and paleomagnetic observations, with details about the configuration and evolution of this supercontinent still a matter for debate. Regrettably, we found that the comment by Piper (this volume) lacks scientific objectiveness. The 'Palaeopangaea' that he promotes is, in our view, based on incorrect application of paleomagnetic data, and is not supported by geological evidence. (C) 2009 Elsevier B.V. All rights reserved.
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| 25. |
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| 26. |
- Lubnina, Natalia V., et al.
(författare)
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A new key pole for the East European Craton at 1452 Ma: Palaeomagnetic and geochronological constraints from mafic rocks in the Lake Ladoga region (Russian Karelia)
- 2010
-
Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 183:3, s. 442-462
-
Tidskriftsartikel (refereegranskat)abstract
- Palaeomagnetic and geochronological studies on mafic rocks in the Lake Ladoga region in South Russian Karelia provide a new, reliably dated Mesoproterozoic key paleopole for the East European Craton (Baltica). U-Pb dating on baddeleyite gives a crystallisation age of 1452 +/- 12 Ma for one of the studied dolerite dykes. A mean palaeomagnetic pole for the Mesoproterozoic dolerite dykes. Valaam sill and Salmi basalts yields a paleopole at 15.2 degrees N, 177.1 degrees E, A(95) = 5.5 degrees. Positive baked contact test for the dolerite dykes and positive reversal test for the Salmi basalts and for the dykes confirm the primary nature of the magnetisation. Comparison of this Baltica palaeopole with coeval paleomagnetic data for Laurentia and Siberia provides a revised palaeoposition of these cratons. The results verify that the East European Craton, Laurentia and Siberia were part of the supercontinent Columbia from the Late Palaeoproterozoic to the Middle Neoproterozoic. (C) 2010 Elsevier B.V. All rights reserved.
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| 27. |
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| 28. |
- Pisarevsky, Sergei A., et al.
(författare)
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Preface
- 2015
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Ingår i: Precambrian Research. - : Elsevier BV. - 0301-9268. ; 259, s. 1-4
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 29. |
- Puchkov, Victor N., et al.
(författare)
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The ca. 1380 Ma Mashak igneous event of the Southern Urals
- 2013
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937. ; 174, s. 109-124
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Tidskriftsartikel (refereegranskat)abstract
- A review of the geochronology, geochemistry and distribution of the 1380 Ma Mashak Large Igneous Province (LIP) of the eastern margin of the East European craton indicates a potential link to a major breakup stage of the Mesoproterozoic supercontinent Columbia (Nuna), link to a major stratigraphic boundary (Lower-Middle Riphean), and economic significance for hydrocarbons and metallogeny. Specifically, the Mashak event likely has much greater extent than previously realized. Two U-Pb baddeleyite (ID TIMS) age determinations on dolerite sills obtained from borehole (Menzelinsk-Aktanysh-183) confirm the western extent of the Mashak event into the crystalline basement of the East European Craton (1382 +/- 2 Ma) and into the overlying Lower Riphean sediments (1391 +/- 2 Ma), and the imprecise ages reported elsewhere indicate the possible extension into the Timan region, with an overall areal extent of more than 500,000 km(2) (LIP scale). It has tholeiitic compositions and is associated with breakup on the eastern margin of the craton - in addition, precise SHRIMP zircon ages of 1386 +/- 5 Ma and 1386 +/- 6 Ma (this paper) provide confirmation of previous approximate 1380-1383 Ma zircon age determination of the same formation, and suggest an age of ca. 1.4 Ga for the Lower/Middle Riphean boundary which was formerly considered to be 1350 +/- 10 Ma. Contemporaneous magmatic rocks in the northeastern Greenland part of Laurentia (Zig-Zag Dal and Midsommerso formations) and Siberia (Chieress dykes and other dolerites) together with the Mashak event are suggested to be fragments of a single huge LIP and to correspond to breakup stage of the Columbia (Nuna) supercontinent. The Mashak LIP also has some significance, at least in Volgo-Uralia, for hydrocarbons and metallogeny. (C) 2012 Elsevier B.V. All rights reserved.
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| 30. |
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| 31. |
- Taran, LN, et al.
(författare)
-
Metamorphism of Paleoproterozoic paragneisses in the Belarus-Podlyasie granulite belt: Prograde-retrograde evolution
- 2003
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Ingår i: Petrology. - 1556-2085. ; 11:4, s. 383-399
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Tidskriftsartikel (refereegranskat)abstract
- Metasedimentary granulites from the central portion of the Belarus-Podlyasie granulite belt were studied with the purpose to reproduce the Paleoproterozoic tectono-thermal evolution in the western part of the East European craton. The regularities identified in the compositional variations in minerals (particularly, garnet), textural relations between minerals, and thermobarometric data point to the complicated evolution of metamorphism with a well pronounced prograde stage. The latter is marked by the predominantly growth zoning of large garnet poikiloblasts from the paragneisses and corresponding variations in the composition of biotite and plagioclase inclusions in this garnet, which testify, when analyzed together with textural -structural relationships between minerals, to a temperature and pressure increase from 530-570degreesC, 3-4 kbar to 650-670degreesC, 6-7 kbar at similar to1870 Ma. The metamorphic peak is represented by the assemblages Grt +/- Crd + Sil + Bt +/- Spl +/- Ilm + Mag + Pl + Kfs + Qtz, occurred at T = 750-760degreesC, P = 7.5-8 kbar, at t similar to 1800 Ma and was coeval with intense bimodal magmatism during the postcollisional evolutionary stage of the granulite belt. Retrograde reactions proceeded as the temperature and pressure decreased from their peak values to 530-540degreesC, 3.5-4.5 kbar at 1780-1740 Ma. The fairly high uplift velocities and cooling rate of the rocks (1.4-0.2 mm/yr and 20-4degreesC/m.y., respectively), the preservation of garnet growth zoning, and a characteristic configuration of the P-T-t path suggest the relatively rapid exhumation of the granulites to upper crustal levels.
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| 32. |
- Vejelyte, Irma, et al.
(författare)
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Early Mesoproterozoic magmatism in northwestern Lithuania: a new U-Pb zircon dating
- 2015
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Ingår i: Estonian Journal of Earth Sciences. - : Estonian Academy Publishers. - 1736-7557 .- 1736-4728. ; 64:3, s. 189-198
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Tidskriftsartikel (refereegranskat)abstract
- We present new geochronological evidence of latest Palaeoproterozoic-earliest Mesoproterozoic magmatism in the Telsiai Deformation Zone, NW Lithuania. Employing the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) at the University of Tasmania, Australia, we demonstrate that a granodiorite, which had previously been considered to belong to the 1850-1820 Ma Kursiai charnockitic batholith, has a U-Pb zircon age of ca 1.62 Ga. The weighted mean Pb-207/Pb-206 age obtained from eight concordant zircon grains is 1625 +/- 6 Ma (MSWD = 0.6), while the upper-intercept concordia age is 1619 +/- 27 Ma (MSWD = 0.56). Like similar ages of granitoids from several small intrusions in Estonia, this once more indicates extensive melting of the crust at that time. We suggest that both the 1.62 Ga magmatism and the emplacement and crystallization of the large Riga anorthosite-mangerite-charnockite-rapakivi batholith in Latvia and western Estonia at 1580 Ma were far-field feedback effects of the formation of the new Palaeoproterozoic continental crust during the Gothian orogeny at the present SW margin of the East European Craton.
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| 33. |
- Vejelyte, Irma, et al.
(författare)
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Timing of ductile shearing within the Druksiai-Polotsk Deformation Zone, Lithuania: a U-Pb titanite age
- 2010
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Ingår i: Estonian Journal of Earth Sciences. - : Estonian Academy Publishers. - 1736-7557 .- 1736-4728. ; 59:4, s. 256-262
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Tidskriftsartikel (refereegranskat)abstract
- A U-Pb dating of titanite from an augen granitoid mylonite in the Druksiai-Polotsk Deformation Zone has yielded a concordant age of 1534 +/- 9 Ma. This light brown titanite follows the foliation in the host rock and was obviously formed during retrogression from amphibolite to epidote-amphibolite facies and coeval mylonitization. Shear zones of the same age are known in southern and central Sweden and in NE Poland. These E-W trending deformation zones accommodate both mafic and granitoid intrusions and are probably related to an extensional period in the Mesoproterozoic evolution in the western part of the East European Craton prior to the 1.50-1.45 Ga Danopolonian orogeny.
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