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Brocker M.,University of Munster | Lowen K.,University of Munster | Rodionov N.,Ap Karpinsky Russian Geological Research Institute Vsegei
Lithos | Year: 2014

The focus of this study is on meta-ophiolitic rocks from Samos and the Attic-Cycladic Crystalline Belt, Greece. SHRIMP U-Pb zircon geochronology, Sr-Nd isotope and bulk-rock geochemistry have been applied to meta-gabbros that occur as blocks and lenses in blueschist-facies mélanges on Samos and Evia, and in the greenschist-facies Upper Unit on Tinos. The geodynamic significance of these meta-ophiolite fragments within the overall pattern of the Eastern Mediterranean region is unclear. Regional correlations within the Cyclades archipelago and with the Jurassic meta-ophiolites of the Balkan region or the Cretaceous occurrences in Turkey are uncertain. Although field, petrological and geochemical similarities among some mélange occurrences suggest a common genetic relationship, such interpretations remain speculative if not supported by robust geochronological data. SHRIMP U-Pb zircon dating of three meta-gabbro blocks from Samos yielded Cretaceous ages with weighted mean 206Pb/238U ages of 78.3±1.3Ma, 76.8±1.4Ma and 77.8±1.4Ma and almost identical intercept ages, interpreted to indicate the time of magmatic crystallization. These results further substantiate models suggesting a correlative relationship with mélanges on the islands of Syros and Tinos, central Aegean Sea, where similar rocks yielded almost identical U-Pb zircon ages.Published and new Sr-Nd isotope data of meta-gabbros from Andros, Samos, Tinos (Lower Unit) and from mainland Greece (Pindos, Othris) reveal distinctive differences among ion probe-dated samples with Jurassic and Cretaceous protolith ages. Three groups can clearly be distinguished in a 87Sr/86Sr vs. 143Nd/144Nd diagram. However, these geochemical parameters do not allow assigning tentative age estimates for yet undated meta-gabbros from southern Evia and the Upper Unit of Tinos. The situation is further complicated by the observation that the Jurassic and Cretaceous meta-gabbros do not show other discriminating geochemical characteristics that could provide plausible arguments for an approximate age assignment to undated rocks. © 2014 Elsevier B.V.


Lorenz H.,Uppsala University | Gee D.G.,Uppsala University | Larionov A.N.,Ap Karpinsky Russian Geological Research Institute Vsegei | Majka J.,Uppsala University
Geological Magazine | Year: 2012

Throughout the high Arctic, from northern Canada (Pearya) to eastern Greenland, Svalbard, Franz Josef Land, Novaya Zemlya, Taimyr and Severnaya Zemlya and, at lower Arctic latitudes, in the Urals and the Scandinavian Caledonides, there is evidence of the Grenville-Sveconorwegian Orogen. The latest orogenic phase (c. 950 Ma) is well exposed in the Arctic, but only minor Mesoproterozoic fragments of this orogen occur on land. However, detrital zircons in Neoproterozoic and Palaeozoic successions provide unambiguous Mesoproterozoic to earliest Neoproterozoic (c. 950 Ma) signatures. This evidence strongly suggests that the Grenville-Sveconorwegian Orogen continues northwards from type areas in southeastern Canada and southwestern Scandinavia, via the North Atlantic margins to the high Arctic continental shelves. The widespread distribution of late Mesoproterozoic detrital zircons far to the north of the Grenville-Sveconorwegian type areas is usually explained in terms of long-distance transport (thousands of kilometres) of either sediments by river systems from source to sink, or of slices of lithosphere (terranes) moved on major transcurrent faults. Both of these interpretations involve much greater complexity than the hypothesis favoured here, the former involving recycling of the zircons from the strata of initial deposition into those of their final residence and the latter requiring a diversity of microcontinents. Neither explains either the fragmentary evidence for the presence of Grenville-Sveconorwegian terranes in the high Arctic, or the composition of the basement of the continental shelves. The presence of the Grenville- Sveconorwegian Orogen in the Arctic, mainly within the hinterland and margins of the Caledonides and Timanides, has profound implications not only for the reconstructions of the Rodinia supercontinent in early Neoproterozoic time, but also the origin of these Neoproterozoic and Palaeozoic mountain belts. © Copyright Cambridge University Press 2012.


Urmantseva L.N.,RAS Institute of Geology and Mineralogy | Turkina O.M.,RAS Institute of Geology and Mineralogy | Kapitonov I.N.,Ap Karpinsky Russian Geological Research Institute Vsegei
Russian Geology and Geophysics | Year: 2012

The paper presents data on high-grade silicate-carbonate rocks (calciphyres) from the Irkut block (Sharyzhalgai uplift, southwestern Siberian craton). Their origin and age were determined from the rock characteristics, U-Pb dating, REE content, and Hf isotope composition of zircon. The calciphyres occur both as independent section fragments and as interbeds within Paleoproterozoic garnet-bearing and high-alumina (cordierite- and sillimanite-bearing) gneisses. They were produced by metamorphism of terrigenous-carbonate sediments. The terrigenous sediments range in maturity from arenites and wackes to argillaceous rocks; this is consistent with the reconstruction of the sedimentary protoliths of paragneisses, which are predominant in the metasedimentary rocks. The petrogeochemical features of the calciphyres, their LREE enrichment relative to "pure" carbonate rocks, and a distinct Eu anomaly were inherited from the terrigenous component of calc-silicate sediments. The Nd model age (2.4-2.7 Ga) of the calciphyres and the value THf(DM-2st) = 2.5-3.0 Ga for zircon from these rocks indicate that carbonate accumulation was accompanied by the supply of terrigenous material, which formed during the erosion of Archean and Paleoproterozoic crust. Zircon from the calciphyres is similar to metamorphic zircon in REE patterns and Th/U ratios. It might have been of detrital origin and then recrystallized during high-temperature metamorphism. Terrigenous-silicate rocks were metamorphosed at ca. 1.87 Ga. This is close to the previous age estimates for the terrigenous rocks metamorphism (1.85-1.86 Ga) and the age of baddeleyite from apocarbonate metasomatic rocks (1.86 Ga). © 2012.


Proskurnin V.F.,Ap Karpinsky Russian Geological Research Institute Vsegei | Vinogradova N.P.,Ap Karpinsky Russian Geological Research Institute Vsegei | Gavrysh A.V.,Ap Karpinsky Russian Geological Research Institute Vsegei | Naumov M.V.,Ap Karpinsky Russian Geological Research Institute Vsegei
Russian Geology and Geophysics | Year: 2012

A detailed petrographic study of a 0.4-1.2 m thick Carnian diamondiferous bed of the Angardam-Tasa Ridge (Ust'-Olenek area, northern Siberia) was performed. It showed that the bed earlier referred to as a terrigenous deposit might be interpreted as an intensely altered volcanoclastic lapilli tuff of basic and, probably, ultrabasic composition. The tuff occurs within a 100 m thick Ladinian-Carnian volcanosedimentary sequence. It consists mainly of resurgent material: altered lithoclasts (nodules of basic-ultrabasic? lithology), devitrified volcanic glass, fragments of autolithic breccia, etc. The thin volcanoclastic sheet is supposed to have formed within a sedimentation basin as a result of phreatomagmatic eruptions of kimberlite volcanoes. The substantiation of the volcanogenic origin of the Carnian diamondiferous bed might be a new approach to elucidate the primary source of widespread placer diamonds in Arctic Siberia. © 2012.


Few published studies of Cenozoic regional uplift and erosion exist for the Eastern (Russian) part of the Barents Sea. The study presented here used several methods to estimate uplift/erosion values for the region, the principal technique being the use of generalised porosity-depth trends. Geophysical well logging data for 33 Russian offshore wells were compiled and processed. The joint interpretation of sonic, gamma-ray, resistivity and spontaneous potential logs was used to calculate porosity and shale fraction for siliciclastic rocks. Comparison of smoothed exponential porosity-depth curves from different wells revealed the rate of compaction for different kinds of sediments and different level of erosion as reference. Vitrinite reflectance and sonic logs were used to provide independent evaluation of the uplift and erosion for calibration. Differential exhumation had occurred throughout the study area. The wells in the centre of the South Barents Basin experienced the least exhumation (400-500 m); the magnitude increases northward up to 2000 m on Franz Josef Land. Uplift/ erosion also increases eastward (the total thickness of eroded rocks for the Admiralteyskaya-1 well near Novaya Zemlya is about 1500 m). Preliminary estimates of exhumation on the Pechora Sea shelf suggest about 1000-1300 m (using both porosity trends and vitrinite Ro data). The improved estimation of burial and uplift history was used to constrain 1D petroleum systems modelling. © 2012 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.


Turkina O.M.,Novosibirsk State University | Urmantseva L.N.,Novosibirsk State University | Berezhnaya N.G.,Ap Karpinsky Russian Geological Research Institute Vsegei | Presnyakov S.L.,Ap Karpinsky Russian Geological Research Institute Vsegei
Stratigraphy and Geological Correlation | Year: 2010

The Early Precambrian granulite-gneiss complex of the Irkut Block (Sharyzhalgai salient of the Siberian Craton basement) with the protoliths represented by a wide range of magmatic and sedimentary rocks, has a long-term history including several magmatic and metamorphic stages. To estimate the age of sedimentation and metamorphism of the terrigenous deposits, the composition of the garnet-biotite, hyper-sthene-biotite, and cordierite-bearing gneisses has been studied; their isotopic Sm-Nd values have been revealed; and the U-Pb zircon dating has been performed using the SHRIMP II ion microprobe. The protoliths of the terrigenous sediments metamorphosed under conditions of the granulite facies correspond to a rock series from siltstones and graywackes to pelites. The Nd model ages of paragneisses range from 2.4 to 3.1 Ga. Zircons of the cordierite-bearing and hypersthene-biotite gneisses show the presence of cores and rims. The clastic, smoothed, and irregular shape of the cores indicates their detrital character and relicts of oscillatory zoning suggest the magmatic origin of zircon. The rim's metamorphic genesis is indicated by the lack of zoning and by the lower Th/U ratio compared to that of the cores. The age of the detrital cores (≥2.7, ~2.3, and 1.95-2.0 Ga) and metamorphic rims (1.85-1.86 Ga) defines the time of sedimentation at 1.85-1.95 Ga ago. Potential sources for the Archean detrital zircons were metamagmatic rocks of the granulite-gneiss complexes in the southwestern margin of the Siberian Craton. The age of the dominant detrital cores at 1.95-2.0 Ga ago, together with the minimal TNd(DM) values, indicates the contribution of the juvenile Paleoproterozoic crust to the formation of sediments. The juvenile Paleoproterozoic crust was likely represented by magmatic complexes similar to the volcanic and granitoid associations of the Aldan shield, which were formed 1.99-2.0 Ga ago and showthe model age of 2.0-2.4 Ga. The isotopic Sm-Nd data show that the Late Paleoproterozoic metasedimentary rocks occur not only in the Sharyzhalgai salient but in the Aldan and Anabar shields of the Siberian Craton as well. © Pleiades Publishing, Ltd., 2010.


Vuks V.J.,Ap Karpinsky Russian Geological Research Institute Vsegei
Paleontological Journal | Year: 2013

Based on the analysis of distribution of Middle-Late Jurassic foraminifers of the western Caucasus in each particular paleotectonic zone, the evolutionary dynamics of foraminiferal assemblages and their relationships are reconstructed. The evolutionary rates of Callovian-Tithonian foraminiferal assemblages in the paleotectonic zones are considered against a background of facies changes. Common and distinctive features in the change of foraminiferal communities and facies at different stages of foraminiferal evolution and the quality of environments for the development of foraminiferal associations are recognized. © 2013 Pleiades Publishing, Ltd.


Majka J.,Uppsala University | Larionov A.N.,Ap Karpinsky Russian Geological Research Institute Vsegei | Gee D.G.,Uppsala University | Czerny J.,AGH University of Science and Technology | Prsek J.,AGH University of Science and Technology
Polish Polar Research | Year: 2012

Neoproterozoic (c. 640 Ma) amphibolite facies metamorphism and deformation have been shown recently to have affected the Isbjørnhamna and Eimfjellet Complex of Wedel Jarlsberg Land in southwestern Spitsbergen. New SHRIMP zircon U-Pb and in situ electron microprobe monazite and uraninite U-Th-total Pb ages are presented here on a pegmatite occurring within the Isbjørnhamna metasedimentary rocks. Although the dated zircons are full of inclusions, have high-U contents and are metamict and hence have experienced notable Pb-loss, the new Cryogenian ages are consistent with the age of regional metamorphism of the host metasediments, providing additional evidence for a clear distinction of the Southwestern Province from the other parts of the Svalbard Caledonides.


Ryabchuk D.,Ap Karpinsky Russian Geological Research Institute Vsegei | Kolesov A.,State Institution Saint Petersburg Center for Hydrometeorology and Environmental Monitoring | Chubarenko B.,RAS Shirshov Institute of Oceanology | Spiridonov M.,Ap Karpinsky Russian Geological Research Institute Vsegei | And 2 more authors.
Boreal Environment Research | Year: 2011

Potential reasons for the drastic intensification and step-like nature of coastal erosion in the Neva Bay area (to the east of the cape Peschany-Lebyazhye line), the easternmost part of the Gulf of Finland, are analysed based on field observations and hydrometeorogical data from adjacent areas. Beaches in this area consist of easily erodible Quaternary deposits that evolve under overall sediment deficit and are relatively vulnerable with respect to changes in the external forcing factors. It is demonstrated that the most extreme erosion events occur when high waves excited by long-lasting western or south-western storms attack the coast during very high storm surges in the absence of stable sea ice. Since 2004 the frequency of occurrence of such combinations has increased mostly owing to, late freezing of the bay and an increase in the number and severity of extreme erosion events in the future is likely. The coasts are also under gradually increasing anthropogenic pressure. Submarine mining operations in the nearshore and construction of large-scale coastal engineering structures such as the Flood Protection Facility may have considerable impact upon the coasts. © 2011.


Turkina O.M.,Novosibirsk State University | Urmantseva L.N.,RAS Institute of Geology and Mineralogy | Berezhnaya N.G.,Ap Karpinsky Russian Geological Research Institute Vsegei | Skublov S.G.,Institute of Precambrian Geology and Geochronology
Russian Geology and Geophysics | Year: 2011

U-Pb dating (SHRIMP-II) and study of the internal structure and composition were carried out for zircon from hypersthene gneiss from the Irkut granulite-gneiss block (Sharyzhalgai uplift in the southwestern Siberian craton). Three generations of zircon have been revealed in the hypersthene gneiss, which differ in zoning pattern, U and Th concentrations, and REE distribution. Zircon cores with growth zoning relics show a REE pattern typical of magmatic zircon: with a high (Lu/Gd)n value (11-36) and a distinct Ce anomaly (Ce/Ce* = 15-81). They belong to early magmatic generation with an age of ≥3.16 Ga. Multifaced soccerball crystals, rims, and unzoned cores of zircon belong to metamorphic generation; they are depleted in REE and show a lower (Lu/Gd)n value (1.1-9.2) than the magmatic cores. This zircon generation formed as a result of the Mesoarchean high-temperature metamorphism at ~3.04 Ga. The latest zircon generation includes thin outer rims with low (Lu/Gd)n (11-12.4) and Th/U (0.02-0.05) values and long-prismatic crystals with an oscillatory zoning, which resulted from the Paleoproterozoic (~1.85 Ga) granulite metamorphism and partial melting. The different ages of high-temperature metamorphism in the granulite-gneiss (~3.04 and 2.55-2.6 Ga) and granite-greenstone (~3.2 Ga) blocks of the Sharyzhalgai uplift reflect the independent tectonothermal and geodynamic evolution of crust in these structures, up to the final amalgamation in the Paleoproterozoic (1.88-1.85 Ga). © 2010.

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