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Now showing items 41-60 of 325
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(2006)Rare earth elements (REE) concentrations of Archean and Proterozoic chemical sediments are commonly used as proxies to study secular trends in the geochemistry of Precambrian seawater. In addition, similarities in the REE ...
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(1989)The oldest supracrustal rocks of the Olekma granite-greenstone region constitute a large 0.8 × 9.5-km erosion remnant among infracrustal formations of the Olekma granite-gneiss complex. They are components of the so-called ...
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(2003)The analysis of radiometric ages of Early Precambrian basites of the Fennoscandian shield, from the most ancient ones, > 3.1 Ga, to 2.40 Ga, resolves five age groups of the basites. Each of these stages is shown to time ...
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(2001)The main peculiarity of the tectonic and magmatic development of the Moon is its resemblance to the Paleoproterozoic stage of the Earth development. The Moon shows no analogues of both the ancient (Archean) terrestrial ...
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(2000)We report detailed high precision combined single grain U-Pb and Lu-Hf studies of early zircons to obtain more reliable indications of the extent of mantle depletion and crustal recycling in the Archean. Despite the ...
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(1998)Using an invariant-polarization ultrasound method, we have studied the velocities of elastic waves in the gneisses and amphibolites of the second rock mass of the Archean complex of the Kola superdeep borehole (7622-9456 ...
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(1986)Abstract Station “Khibiny”, equipped with a powerful magnetohydrodynamic (MHD) generator and/or diesel generator, has been successfully used since 1976 to study the electrical conductivity of the Earth's crust in the ...
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(1996)Major- and trace-element concentrations and Nd-, Sr- and Pb-isotopic ratios are reported for the Dovyren layered mafic-ultramafic intrusion in the northern Baikal region, eastern Siberia. SmNd internal isochrons for an ...
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(2005)Komatiite samples from the 2.8-Ga Kostomuksha greenstone belt in the Baltic Shield define Pt–Os and Re–Os isochrons with ages of 2816 ± 190 and 2880 ± 83 Ma, respectively. The mean initial 186Os / 188Os and 187Os / 188Os ...
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(2004)The Archean bedrock of the Ukrainian Shield is divided into western and central blocks by a N–W trending tectonic zone known as the Golovanevsk suture zone. Within this zone, there are numerous mafic-ultramafic bodies ...
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(2001)The crust in the south of the Siberian Craton includes the tonalite-trondhjemite complex of the basement, the highly metamorphozed rocks of the Kitoi Suite, the rocks of the Onot greenstone belt, ultrametamorphic rocks, ...
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(2001)Different stages of evolution of geological structures are recorded in time dynamics of their gravity field. The regularities of the crust evolution on the territory of Belarus were investigated through claculation and ...
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(1999)It has long been known that the measured kappa (232Th/238U, or κ) of mid-ocean ridge basalts (MORB) and, by inference, the upper mantle, is much lower than the time-integrated κ recorded by Pb isotope ratios (κPb). We ...
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(1989)A newly discovered structure on the southeastern margin of the Baltic Shield, in an area where finds of Saamian high-magnesium volcanic rocks are likely, is the Vodlozero Block, with an area of as much as 40,000 km2. In ...
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(1988)Ultramafic rocks in the Precambrian sequence of the Eastern Sayan were traditionally classified as plutonic. Within the Khan-Ashkasok synclinorial trough of Early Proterozoic age studied by us, such rocks were mapped as ...
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(1998)Metamorphic rocks of the Archean Central Kola granulite area, Baltic Shield, contain two major fluid-inclusion types: gaseous and salt-bearing aqueous (brines). Most of the abundant gaseous inclusions are CO2-rich, containing ...
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(2002)We use published and new trace element data to identify element ratios which discriminate between arc magmas from the supra-subduction zone mantle wedge and those formed by direct melting of subducted crust (i.e. adakites). ...
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(2002)Deep lithospheric roots, commonly extending to the diamond stability field, are distinctive characteristics of Archean cratons, but their origin remains controversial. The 2.7 Ga Abitibi greenstone belt initially developed ...
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(2003)Subduction of oceanic crust at an unusually low-angle has been proposed as a model for the growth of continental crust older than about 2.5 Ga. At modern zones of low-angle-, or flat-subduction, magmatic additions to new ...
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(2001)The rate of growth of Earth's continental crust is commonly estimated from the age distribution of present continental crust and from the geochemistry of ancient mantle-derived lavas. In this paper, I assess the rate of ...
Now showing items 41-60 of 325