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Eclogites were relatively recently found in the Belomorian Mobile Belt (BMB) (Volodichev et al., 2004; Shchipanskii et al., 2005; Konilov et al., 2004). The very first isotopic dates (Volodichev et al., 2004; Mints et al., 2010) were obtained for these rocks in the northwestern (in the Salma and Kuru-Vaara areas) and central (Gridino area) portions of BMB and corresponded to the Archean: approximately 2.72–2.87 Ga. Because no crustal eclogites older that 2.0 Ga (Möller et al., 1995) had been known before these dates were obtained, these eclogites were regarded as unique. It is commonly believed that no crustal eclogites could be formed in the Archean because the crust was then relatively thin (Kröner, 2010), and hence, the find of crustal eclogites of Archean age in BMB called for a fundamental revision of geodynamic reconstructions of the crustal evolution and was one of the main arguments invoked to support the hypothesis that currently operating geodynamic mechanisms of plate tectonic can be extrapolated to the Early Precambrian (Rozen et al., 2008). However, these finds were practically immediately followed by serious doubts that the primary estimates of the timing of the eclogite metamorphism in the Belomorian Belt may be incorrect (Mitrofanov et al., 2009; and others). 相似文献
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S. G. Skublov B. Yu. Astaf’ev Yu. B. Marin A. V. Berezin A. E. Mel’nik S. L. Presnyakov 《Doklady Earth Sciences》2011,439(2):1163-1170
The repeated isotopic and geochemical study of zircons of the eclogite from Stolbikha Island (Gridino settlement area) allows
one to interpret the U-Pb age value of about 2700 Ma by central parts of zircon grains as a magmatic event time, probably
rejuvenated to a degree by intense manifestation of the eclogite metamorphism of about 1880 Ma age. The Svecofennian high-pressure
metamorphism caused a partial recrystallization of zircons of magmatic origin and the appearance of their rims showing typical
geochemical characteristics of eclogite zircons. 相似文献
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E. V. Berezin I. B. Konovalov S. A. Gromov M. Beekmann E. -D. Schulze 《Russian Meteorology and Hydrology》2013,38(11):750-758
Presented are the results of the model study of wildfire impact on the spatial distribution of deposition fields of sulfur and nitrogen compounds in the regions of Siberia and the Russian Far East. The CHIMERE chemistry transport model was used for computing the deposition fields taking account of pyrogenic emissions specified using satellite measurements of intensity of wildfire heat radiation. Carried out is the model validation using the data of ground-based measurements of nitrate and sulfate concentrations in precipitation at the Russian EANET stations as well as the data of satellite measurements of carbon dioxide content in the troposphere and aerosol optical depth carried out by IASI and MODIS instruments, respectively. It is demonstrated that wildfires considerably influence deposition of sulfur and nitrogen compounds and redistribution of nitrogen compounds assimilated by plants within the regions under consideration. 相似文献
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First HF radar measurements of summer mesopause echoes at SURA 总被引:3,自引:0,他引:3
A. N. Karashtin Yu. V. Shlyugaev V. I. Abramov I. F. Belov I. V. Berezin V. V. Bychkov E. B. Eryshev G. P. Komrakov 《Annales Geophysicae》1997,15(7):935-941
HF sounding of the mesosphere was first carried out at SURA in summer 1994 at frequencies in the range 8–9 MHz using one of the sub-arrays of the SURA heating facility. The observations had a range resolution of 3 km. Almost all measurements indicated the presence of strong radar returns from altitudes between 83 and 90 km with features very similar to VHP measurements of mesopause summer echoes at mid-latitudes and polar mesopause summer echoes. In contrast to VHP observations, HF mesopause echoes are almost always present. 相似文献
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S. G. Skublov A. V. Berezin A. E. Melnik B. Yu. Astafiev O. A. Voinova V. I. Alekseev 《Petrology》2016,24(6):594-607
Several types of metabasites of different age were identified in the southern part of Pezhostrov Island: eclogites with a magmatic protolith age of about 2200 Ma and 2500 Ma old metagabbroanorthosites that retained no eclogitic assemblage. It is shown that the Paleoproterozoic eclogites dominate volumetrically over Archean eclogites in the Belomorian eclogitic province. Eclogites with the youngest Jatulian protolith age (no older than 2200 Ma) occur with the same frequency as those with the Archean protolith age. A new find of eclogites with a Paleoproterozoic age of magmatic protolith and generalization of accumulated geochronological data confirm the recognition of an extended zone of high-pressure metamorphism with an age around 1900 Ma in the Belomorian mobile belt. 相似文献
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The paper represents results of a comprehensive geochemical and isotopic-geochemical (SIMS) study of eclogites from the northwestern
part of the Belomorian Belt (Salma eclogites). A detailed fieldwork was carried out at the quarry of the Kuru-Vaara deposit
of ceramic pegmatite in the northwestern part of the study area, in which tonalite-trondhjemite gneisses include bodies and
blocks of eclogite and Grt-Aug eclogite-like clinopyroxenite and are cut across by numerous pegmatite veins. The least altered types of the Grt-Cpx rocks selected for our further research included: (1) widespread massive homogeneous fine-grained Grt-Omp eclogite that replaced gabbro and contained symplectites of Pl + low-Na-Cpx around omphacite and Pl-Hbl kelyphite rims around Grt; and (2) coarse-grained eclogite-like Grt-Hbl-Aug clinopyroxenite beds up to 20 cm thick in the central parts of high-Mg metaultrabasites, which are mostly tremolite-actinolite
schists. The REE patterns of garnet, clinopyroxene, and amphibole from the eclogites confirm that they crystallized simultaneously,
under a high pressure, and in the absence of plagioclase. Local U-Pb dates of the zircons and their geochemistry are at variance
with the earlier hypothesis that the eclogite metamorphism occurred in the Archean. The eclogites and Grt-Hbl-Aug clinopyroxenite were determined to contain zircons of Svecofennian age (approximately 1900 Ma), which show all geochemical
characteristics of classic eclogitic zircons and occur either as individual crystals or as rims around Archean magmatic zircons
from the primary gabbroids. 相似文献
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