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Том 53, № 6 (2018)
- Год: 2018
- Статей: 7
- URL: https://journals.rcsi.science/0024-4902/issue/view/9880
Article
Specific Features of Sulfide Ores in the Pobeda Hydrothermal Cluster, Mid-Atlantic Rise 17°07′–17°08′ N
Аннотация
Based on materials obtained in Cruise 37 of the R/V Professor Logatchev (2014‒2015), the paper discusses formation conditions, morphology, isotope age, and mineral and chemical composition of sulfide ores in the Pobeda-1 (17°08.7′ N MAR) and Pobeda-2 (17°07.45′ N MAR) hydrothermal ore fields (Pobeda ore cluster) discovered in blocks 37 and 39 confined to the Russian exploration area. Morphogenetic types of ores are defined and their formation conditions are examined.
431-454
Glauconite Sand from the Terrace of the Patagonian Continental Slope, Southwestern Atlantic
Аннотация
This brief communication describes the first finding of glauconite sand alternating with calcareous foraminiferal–coccolithic ooze on the Piedra Buena contourite terrace of the Patagonian continental slope at a depth of 2327 m. It is suggested that the fine-sand glauconite grains were supplied from the shelf during glaciations, rewashed and sorted by alongslope (contour) currents of the Circumpolar Antarctic waters with the formation of sandy glauconite contourites.
455-459
Architecture of the Southern Marginal Zone of the Upper Jurassic–Valanginian Carbonate Platform of the Northeastern Caucasus (Dagestan, Shakhdag Massif)
Аннотация
The structure of the southern marginal zone of the Upper Jurassic–Valanginian carbonate platform, Northeastern Caucasus, is considered with the Dagestan sector of the Shakhdag Massif as example. The massif consists of several large genetically diverse sedimentary complexes: (1) Upper Jurassic basal complex represented by the shallow-water terrigenous and carbonate sediments, which were formed under unstable sedimentation conditions; (2) reef complex ascribed to the barrier reef system; and (3) sedimentary sequence with the typical clinoform structure and the southwestward dip, toward the Dibrar trough. The formation of the marginal zone of the carbonate platform was mainly determined by (1) climatic conditions (transition from the humid climate in the Early and Middle Jurassic to the arid climate in the Late Jurassic) and (2) differences in the tectonic evolution of different structural-facies zones (weak subsidence of the Northeastern Caucasus, where carbonate platform was formed, and intense subsidence to the south in the flysch trough area). The formation of the internal structure of the Shakhdag Massif was mainly defined by the eustatic sea-level fluctuations.
460-472
Postglacial Deposits of the Dal’nyaya Taiga Group: Early Vendian in the Ura Uplift, Siberia. Communication 2. Ura and Kalancha Formations and History of the Basin
Аннотация
The paper presents the facies characteristics and sequence-stratigraphic reconstructions of the Lower Vendian postglacial deposits of the Dal’nyaya Taiga Group (Ura Uplift, Patom basin, Siberia). The section is divided into two sequences: the first sequence corresponds to the Barakun Formation; the second sequence, to the Ura and Kalancha formations. Together, they make up a continuous transgressive-regressive succession, with its significant part formed in a deep-water zone of the low-angle (about 1°) homoclinal carbonate–terrigenous and clayey–carbonate ramps. The upper sequence boundary passing along the top of deposits in the Kalancha carbonate platform corresponds to the stratigraphic hiatus at the Zhuya Group base. The fine-grained siliciclastic material, which makes up as much as 50 vol % of the Ura sediments, has an eolian origin. Probably, high activity of eolian processes promoted by a moderately cold arid or semiarid climate at that time was one of the reasons for high bioproductivity in the paleobasin. The consequent large-scale burial of organic matter could foster the reactivation of methanogenic processes. The lithological features of sediments were responsible for their thixotropic state that provoked the slumping of sedimentary masses during high seismic activity.
473-488
Thermobaric Depth Settings of Sedimentary Rock Basins and Their Fluid Dynamics: Communication 1. Zonation of the Stratispheric Structure and Constraints of Anomalous High and Superhigh Fluid Pressures
Аннотация
The paper addresses zonation of the stratisphere: thermobaric conditions in its deep zones with anomalous high (AHP) and superhigh (SHP) fluid pressures, as well as main types of fluid-dynamic setting in the upper zone. Mechanisms of the clay dehydration and processes of oil-and-gas formation governing the development of superhigh fluid pressures in the lower zone of rock formation are also discussed.
489-506
Variability in Contents of the Major Ore Components of Ferromanganese Formations in the Lakes–Seas–Oceans Series
Аннотация
Based on statistical methods, the available literature data were processed to analyze regularities in the distribution of five ore elements (Fe, Mn, Cu, Co, Ni) in ferromanganese nodules and crusts in an idealized lakes–seas–oceans profile. Application of the cluster analysis confirmed the regularities revealed by calculations of the mean contents of these elements and unraveled some additional features of their distribution.
507-524
Isotope Compositions (δ13C, δ18O) of Manganese Carbonates of the Porozhinsk Deposit (Yenisei Ridge, Krasnoyarsk Region)
Аннотация
New carbon and oxygen isotope data are reported on carbonate ores and host dolomites (upper Pod”emsk subformation) of the Porozhinsk manganese deposit. Manganese carbonates filling the karst depression of the Porozhinsk area are characterized by low δ13C (–14.6…–9.5‰, PDB) and δ18O (18.8…22.1‰, SMOW). These data indicate that the carbonate formation was contributed by the isotopically light carbon, which was released during the decomposition of organic matter, while waters of the ore-precipitating solutions were presumably of meteoric origin. Host dolomites (Porozhinsk and Mokhovoi areas) are characterized by the heavier carbon (–1.9…2.0‰) and oxygen (23.3…27.7‰) isotope compositions, which are presumably typical of carbonate sediments of the Late Neoproterozoic sea basin.
525-532