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Doklady Earth Sciences - A first set of K–Ar isotopic ages obtained, which allowed to estimate the age of the largest volcanoes of the Anaunsky Dol (3.2, 2.2 and 1.9 Ma) and eruptive centers...  相似文献   
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IntroductionThe Late Triassic strata andflora developed andwell outcropped in southern Pri morye,Russia.Thestrata are marine and non-marine alternate for eachother and yield abundant mollusk and plant fossilsinwhich the Late Triassic Mongugai flora is well-known in the world.Kryshtofovich(1910,1921,1924)and Kryshtofovich&Prynada(1932)studiedthis florainthe earlier ti me,and consequently,Sre-brodolyskaja(1958,1961,1968),Schorokhova(1975,1977,1997,2004)and Krassilov&Schorokhova(1970,1975)ma…  相似文献   
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Doklady Earth Sciences - The K–Ar isotopic age of the beginning of formation of Ichinsky (0.35) and Khangar (0.4) stratovolcanoes is established for the first time, as well as the age of the...  相似文献   
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New 40Ar/39Ar and published 14C ages constrain voluminous mafic volcanism of the Kamchatka back-arc to Miocene (3–6 Ma) and Late Pleistocene to Holocene (<1 Ma) times. Trace elements and isotopic compositions show that older rocks derived from a depleted mantle through subduction fluid-flux melting (>20%). Younger rocks form in a back arc by lower melting degrees involving enriched mantle components. The arc front and Central Kamchatka Depression are also underlain by plateau lavas and shield volcanoes of Late Pleistocene age. The focus of these voluminous eruptions thus migrated in time and may be the result of a high fluid flux in a setting where the Emperor seamount subducts and the slab steepens during rollback during terrain accretions. The northern termination of Holocene volcanism locates the edge of the subducting Pacific plate below Kamchatka, a “slab-edge-effect” is not observed in the back arc region.  相似文献   
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Based on the geochemical characteristics of the Miocene-Quaternary volcanic rocks of the Sredinny Range of Kamchatka, we divide it into northern and southern provinces; the latter comprises the “eastern”, “western”, and “central” flanks. We present new data on the composition of Neogene-Quaternary volcanic rocks in the southern part of the Sredinny Range of Kamchatka: Khangar and Icha volcanic massifs and Mt. Yurtinaya on the “western” flank, Bystrinsky and Kozyrevsky Ridges on the “eastern” flank, and Anaunsky Dol and Uksichan massif located in between. We show systematic differences in the composition of rocks from the “western” and “eastern” flanks. During the Neogene, a typical island-arc volcanism took place within the “eastern” flank. Quaternary volcanic rocks of this area have both island-arc and within-plate geochemical features. We propose to call rocks of this type hybrid rocks. Within the “western” flank, hybrid volcanism has been manifested since the Neogene, while typical island-arc rocks are not found. Magma generation processes on the “western” flank of the Sredinny Ridge are influenced by an enriched mantle source; the effect of fluid is less pronounced here as compared to the rocks of the “eastern” flank, where it is clearly traced.  相似文献   
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Palynological samples, plant megafossils, and fossil wood taken from the upper Lipovtsy Subformation (Porechye open-pit coal mine in the Il’ichevka coalfield, Razdol’naya River Basin, southern Primorye), as well as coal samples for determining coal-forming plants from dispersed cuticles are analyzed. The taxonomic composition of the identified palynomorphs from the coals and interstratal clastic sediments indicates the Aptian age of host deposits. The palynological spectra from the lower humic–rhabdopissite coal seam are dominated by Gleicheniaceae and Cyatheaceae accompanied by Dicksoniaceae and Ginkgocycadophytus. In the palynological spectra from the upper coal seam, the share of Gleicheniaceae substantially decreases, though they remain dominant; simultaneously, single angiosperm pollen grains appear in them. The spectra from the clastic rocks are dominated by Polypodiaceae and Cyatheaceae. The taxonomical composition of the gymnosperms is relatively diverse, although their abundance is low. The share of angiosperms increases with respect to both their diversity and abundance. The angiosperm pollen, found for the first time in the Aptian deposits of the Razdol’naya River Basin, provides grounds to assume that these pants appeared earlier than previously thought (early Albian). The coal-forming plants of the Il’ichevka coalfield are determined.  相似文献   
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Taxonomic composition of plant fossils from the Aptian-Cenomanian sediments of the Alchan, Razdol’naya, and Partizanskaya depressions of Primor’e is studied in detail. Each of the established floral assemblages characterizes a particular stage of flora stabilization. Correlation of the assemblages is performed. Floral assemblages of the Alchan depression, which occur in association with macrofauna, are suggested to be the standard ones for the southern Far East. New species are described.  相似文献   
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First data on major, minor and trace element (XRF. 1CP-MS) concentrations in the volcanic rocks of the IVS 50th anniversary Fissure Tolbachik eruption are reported for the period from 27.11.2012 to 25.01.2013; scheme of lava flows distribution by March 2013 is made. The volcanic rocks of the new eruption are substantially different from the other studied volcanic rocks of Tolbachinsky Dol by their higher alkalis and incompatible elements content. The rocks of the first three days of eruption (Menyailov Vent) have higher silica and alkalis content than all previously reported volcanic rocks of Tolbachinsky Dol. Volcanic rocks of the Naboko Vent, at silica content similar to high-Al basalts of Tolbachinsky Dol, have different concentrations of trace elements and some major elements (K2O, CaO, TiO2, P2O5). REE and other incompatible element concentrations in the rocks of the Menyailov Vent are higher than in the rocks of the Naboko Vent at the same element ratios. The differences of the volcanic rocks of the two vents of the new eruption may be caused by the fact that the erupted lavas came from the different levels of the same magma chamber.  相似文献   
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