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Now showing items 41-60 of 160
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(1988)The europium minimum often observed in Archean ultramafic and mafic rocks reflects both the effect of protomagmatic processes (fractional crystallization, accompanied by removal of feldspars and clinopyroxene from the ...
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(2001)Petrological, geochemical, and geochronological data for the basic-ultrabasic rocks of the Bulun block from the Sharyzhalgai uplift are reported, and the age and geodynamic environments of these geologic structures are ...
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(2001)Metamorphic rocks-hydrolysates, which are strongly enriched in Al and Fe (sericite, pyrophyllite, chloritoid, diaspore, and hematite schists), are developed in the interformational contact zone between Precambrian pre-Uralide ...
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GEOCHRONOLOGY AND FORMATION SUBDIVISIONS OF THE LOWER PRECAMBRIAN IN THE NORTHWESTERN LADOGA REGION (1996)A brief geological review of the northwestern Ladoga region and systematics of the Lower Precambrian subdivisions in this territory are presented. The respective stratigraphic scale and supplementary geologic scheme include ...
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(1990)In seismic sections of many regions in the world, there are discrete intracrustal wave-guide or inversion layers with low elastic-wave velocities relative to the host rocks. From our model of the development of intracrustal ...
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(2002)This paper describes the Late Precambrian geologic complexes from the southern margin of the Siberian Craton, associated with the extension epochs. Analysis of the data available suggests that there were two episodes of ...
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(1992)The late Precambrian and Cambrian world experienced explosive evolution of the biosphere, including the development of biomineral skeletons, and notably of phosphate and siliceous skeletons in the initial stages of the ...
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(1988)Geologists have repeatedly formulated ideas concerning great renewals of short duration in the Precambrian history of the Earth, i.e., colossal structural reorganizations, collapses, extensive inversions and changes in ...
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(1999)The paper gives the definition of the North-Asian craton as a geological structure. The evolution of conception and views of its structure and boundaries is considered, and a brief overview of its geologic history in terms ...
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(2004)Study of the Khitoostrov, Varatsk, and other corundum occurrences in kyanite-garnet-biotite plagiogneisses of the Chupa section (Belomorian Mobile Belt) has revealed their association with products of low-alkaline Ca-Na ...
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(1989)The boundary dated at 200 to 1800 m.y. marks an event that is of fundamental importance in the Earth's history and separates the early stages of planetary evolution from the Neogaean with its present type of geodynamics. ...
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(1992)Banded iron formations (BIF) are prominent in sediments older than 2 Ga. However, little is known about the absolute abundance of BIF in Archean and Early Proterozoic sediments, and the source of the Fe is still somewhat ...
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(1988)We studied the possibility of using metamorphic diopside-rich and diopside-bearing rocks, virtually devoid of iron, titanium and alkali oxides, in various silicate technologies. Such rocks are widespread in the Precambrian ...
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(1989)The tracing of the geochemical evolution of carbonate deposits in the earth's history is a major scientific problem. Our understanding of this evolution is in inverse relation to the age of sedimentary sequences. However, ...
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(2015)The Jiamusi massif is a major tectonic unit in the eastern part of NE China and composed chiefly of the Early Paleozoic (about 500 Ma) metamorphosed crystalline basement containing Precambrian, even Archean crust and three ...
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(1983)The available data on radiometric dating of Riphean and Vendian deposits in the European part of the U.S.S.R. enabled us to establish the age of geochronological boundaries. The Riphean lower boundary was adopted as 1650 ...
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(1989)The linear fold tectonics that determines the structural look of the continental crust expresses a P-T regime of the crust that assumes the presence of a thick 'load-bearing' mesozonal layer (with a temperature range of ...
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(1997)Stratigraphic investigations of the Precambrian in Karelia and the Kola Peninsula, which are the type area for the pre-Riphean part of the Proterozoic of northern Eurasia, demonstrate a priority of local stratigraphic ...
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(2003)The isotopic composition of carbon and oxygen was determined by two techniques in whole-rock samples and single grains of carbonates from rocks of various morphogenetic types from the Aldan Shield. The isotopic values ...
Now showing items 41-60 of 160