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51.
A. V. Maslov 《Lithology and Mineral Resources》2010,45(5):443-464
Lithochemical features of the Early-Late Paleozoic and Cenozoic glaciogenic and related sedimentary rocks around the world
are considered. Comparison of the bulk chemical composition of diamictites with the average Post-Archean Australian Shale
(PAAS) revealed that the diamictites do not show any lithochemical characteristics unambiguously indicating their formation
under cool climatic conditions. The chemical index of alteration (CIA) often used in the paleoclimatic reconstructions should
be considered as additional (though very important) tool, because it is controlled by local factors. Taking into account these
facts, there are likely no grounds to expect that the amount of the redeposited sedimentary material in the Late Paleozoic
and Cenozoic glaciogenic rocks is more than in their Early Proterozoic and Late Riphean-Vendian analogues. 相似文献
52.
A. V. Maslov A. D. Nozhkin V. N. Podkovyrov E. F. Letnikova N. V. Dmitrieva Yu. L. Ronkin 《Russian Journal of Pacific Geology》2010,4(5):379-397
The clarkes of concentrations (Kc) of a wide range of trace elements (Li, Be, B, Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Ge, As, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, In,
Sb, Cs, Ba, REE, Hf, Ta, Hg, Tl, Pb, Bi, Th, and U) were analyzed for fine-gained terrigenous rocks (mudstones, metapelites)
from the reference Riphean sections of the Uchur-Maya region and the Yenisei Range. It was established that the shales and
mudstones of the Uchur and Aimchan groups in the Riphean hypostratotype section are characterized by moderate (2.5 < Kc < 5) and intense (Kc > 5) geochemical specialization for Li, B, and Zn. At the same time, the similar rocks of the Lakhanda and Ui groups do not
exhibit any distinct geochemical specialization, although they are notably enriched in HREE. The metapelites from the basal
formations of the Riphean sedimentary successions in the Yenisei Range are distinctly specialized for B and slightly for Li,
Rb, Be, Nb, Ta, Th, Ge, and Cd. In addition, moderate specialization for Cu is characteristic of the metapelites from the
Korda and Lopatino formations; for Bi, Sb, Hg, and V, for their analogs from the Potoskui Formation; and, for Hg and Cs, for
the similar rocks from the Lopatino Formation. The metapelites of the Lower Riphean Korda Formation from the central zone
of the Yenisei Range have elevated contents of significantly more elements (Li, Be, Sc, V, Cr, Co, Ni, Zn, As, Rb, Y, Zr,
Nb, Sb, Ag, In, Hf, Hg, and others) than their counterparts from its eastern near-platform part. The mudstones of the ore-bearing
(Pb, Zn) Gorevo Formation are characterized by elevated concentrations of several ore elements such as Pb, Cd, As, Sb, and
Bi. The elevated Kc values of the rare lithophile and of several ore elements in the metapelites of the Yenisei Range are determined by the high
geochemical differentiation of the Early Precambrian blocks constituting the western margin of the Siberian Craton, which
were eroded in the Riphean, and the syn-sedimentary riftogenic and intraplate magmatism. On the contrary, the fine-grained
and terrigenous rocks from the basal part of the Riphean section in the Uchur-Maya region are compositionally closer to the
immature Late Archean substrates or their Early Proterozoic analogs. 相似文献
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S. F. Abdullaev V. A. Maslov B. I. Nazarov T. Kh. Salikhov 《Izvestiya Atmospheric and Oceanic Physics》2014,50(4):431-434
The results of studies of aerosol optical thickness (AOT) in Dushanbe conducted from July 2010 to March 2011 within the AERONET program are discussed. The statistical characteristics of AOT have been shown to significantly vary during dust intrusions. The seasonal variations in the dustiness of the atmosphere have been analyzed. 相似文献
58.
Lithogeochemical features of the Vendian mudstones and silty mudstones taken from Borehole Keltma 1 in the southern part of
the Vychegda trough of the Mezen syneclise are discussed. It is shown that fine-grained clastic rocks of the Ust-Pinega, Krasavino,
and Mezen formations have similar chemical compositions, suggesting their accumulation in sufficiently similar settings. The
main part of the studied samples has K2O/Al2O3 < 0.4. This fact, in combination with the absence of TM-FM and NPM-HM correlations, indicates a significant contribution
of recycled aluminosiliciclastics in their composition. At the same time, the absence of correlation between CIA and indicator
ratios of rock composition in the paleodrainage basins, such as Th/Cr and Th/Sc, indicates that CIA and some other lithochemical
indicators appropriately reflect the paleoclimatic conditions in source areas surrounding a basin. The CIA value in most of
the analyzed samples is no more than 70. Thus, the Keltma section is similar to Upper Vendian sequences of the Kvarkush-Kamennogorsk
anticlinorium and the Shkapovo-Shikhany depression. It has been established that felsic and intermediate magmatic rocks coupled
with a significant contribution of quartz-rich sediments served as the source of fine aluminosiliciclastics for the southern
Vychegda trough during the Vendian. High Ce/Cr values in the mudstones and silty mudstones suggest that the geochemically
primitive Archean protoliths were not involved in the washout. In the SiO2-K2O/Na2O diagram, the Vendian mudstones and silty mudstones are plotted in the field of sediments of active continental margins.
Typical low values of Mo/Mn and some other redox indices in these rocks indicate that oxidizing environment predominated in
bottom waters of the sedimentation basin during the entire Vendian. Analysis of variations of the lithochemical indicators
upward the Vendian sedimentary successions in borehole Keltma 1 made it possible to divide the section into three sequences
of different lithofacies and paleontological compositions. 相似文献
59.
A. V. Maslov G. M. Vovna V. I. Kiselev M. T. Krupenin Yu. L. Ronkin 《Doklady Earth Sciences》2011,439(1):933-938
The results of application of the LA-ICP-MS method for analysis of U-Pb ages of detrital zircons from Serebryanka Group (Middle
Urals) has been presented for the first time. It has been found that the detrital zircon population in tillite-like conglomerates
of the Tany Formation is represented nearly in equal shares by grains with Neoarchean and Paleoproterozoic U-Pb ages. This
allows the basement crystalline rocks from the eastern part of the East European Craton to be considered as the principal
source of aluminosilicate clastic material in the beginning of the Serebryanka. The population of detrival zircons in sandstones
from the Kernos Formation consists of Meso- and Neoarchean (approximately 15%), Paleoproterozoic (∼60%), and Mesoproterozoic
(∼26%) zircon grains. Comparison of the obtained data with the materials on detrital zircons from Tonian and Ediacarian sandstones
in the southern Urals has shown that the principal role in formation of Tonian and Ediacaran sedimentary sequences was played
by the products of Mid- and Late Paleoproterozoic crystalline rock erosion in the craton socle. In addition to this, accumulation
of the Serebryanka Group took place with visible participation of more ancient—Early Paleoproterozoic, Neo- and Mesoarchean—rock
associations on the paleo-water catchment areas. The end of the Serebryanka period differed from its beginning by the additional
appearance of Mesoproterozoic complexes in alimentation zones; for comparison, the role played by these complexes in formation
of Ectasian-Ediacarian deposits of the adjacent southern Urals segment is insufficient, judging by the currently available
data. All these facts may indicate that there are significant differences in the spatiotemporal distribution of clastic material
sources for Upper Precambrian deposits in the West Megazone of the southern and middle Urals. 相似文献
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