pdf № 288, December

DOI: 10.19110/2221-1381-2018-12-3-11

The article presents the results of complex geophysical studies of the fault zones of the Vychegda depression. At the first stage of the investigation, fault tracing was performed based on seismic data and potential fields, followed by radon monitoring. The results showed that the faults of the Vychegda depression were reliably identified in seismic time sections. According to the data of potential fields, faults were most distinctly expressed in a magnetic field. In the radon field, the dislocations corresponded to the areas of increased the volume radon activity. Using the methods listed above, the Vychegodsko-Lokchimskiy, Keltminskiy, and Visherskiy faults were identified and the location of the Predtimanskiy fault was corrected. Thus, the presented complex of methods allows mapping the faults covered by the sedimentary cover within the platforms.

Keywords: faults, seismic methods, gravimagnetic studies, volume radon activity.

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DOI: 10.19110/2221-1381-2018-12-12-15

We found garnets, penetrated by numerous etch channels, in a stream-sediment sample from alluvium of the Syuzyu River (South Timan). We studied morphological features, internal structure and chemical composition of the garnet by a scanning electron microscope. We established that they were andradite-grossulars, typical for skarns, but with peculiar negative relief — etch channels and wedge-shaped depressions. Such forms, which are traditionally considered a typomorphic feature of pyropes of diamondiferous associations, were for the first time discovered in calcareous garnets. We assumed that the negative forms of relief was conditioned by epigenetic changes resulted from occurring of the mineral in the weathering crust.

Keywords: garnet, microstructure, skarn, etch channels, weathering crust.

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DOI: 10.19110/2221-1381-2018-12-16-22

The results of lithological, palynological and radiocarbon methods for the study of the deposits of paleochannel in the lower Kuya River valley in the northwest of the Bolshezemelskaya tundra are presented. The complex study made it possible to trace the history of the development of the river, to reveal the paleogeographic features of the formation of the oxbow-lake, to characterize the conditions and processes of sedimentation, to reconstruct the natural and climatic conditions of the late Holocene in the subarctic zone of the European North of Russia, attracting researchers in connection with the development of the territories of the Far North. The formation of old stream channel and the time of its sediments is the Subatlantic (SA) period of Holocene. Plant communities reflect fluctuations in climatic conditions: periods of cooling of the early and late subatlantics, shared by warming in the middle of the period.

Keywords: Holocene, old stream channel, palaeogeography, palynology, facies.

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DOI: 10.19110/2221-1381-2018-12-23-30

Petrographic, petrochemical and preliminary geochemical (ICP MS) and isotope geochemical (O_Zrn, Sm–Nd, (Lu–Hf)_Zrn) data allow us to consider granitoids of the Gerdizsky massif as forming in an intraplate setting and represent A-type with crust-mantle characteristics. The new U-Pb (SIMS) geochronologic data show that the granitoids of the northern part of the Gerdizsky massif in the northern Urals are (496±7) Ma.

Keywords: A-type granites, isotopic and geochemical characteristics, Gerdiz massif, Polar Urals.

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DOI: 10.19110/2221-1381-2018-12-31-38

The composition and structure of the Lower Carboniferous part of the Yajyu Suite, common in the eastern subzone of the Lemva structural-formational zones of the Urals is given. It is an indicator of collision processes beginning in the northern part of the Urals and it reflects the geological history of this period. The scaly-thrust structure of the region, small isoclinal folds, numerous discontinuous disturbances and redeposition of organic remains strongly obscured layers succession. The discovery of the lithological marker allowed to decipher the geological structure of one of the tectonic «scales» (plates).

Keywords: Urals, Lemva zone, Lower Carboniferous deposits, Yajyu Suite, sedimentary rocks, stratigraphy, lithological marker.

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DOI: 10.19110/2221-1381-2018-12-39-45

The Chudnoe gold-ore deposit, located in the Maldin ore zone of the Subpolar Urals, is of great interest in terms of formation conditions. Gold is mainly concentrated in fuchsitic veinlets of rhyolites, in association with palladium and rare earth minerals. For the first time, the authors conducted a study of the local areas of rhyolite bleaching, characteristic of the deposit, which do not contain fuchsite, but are also gold-bearing. It was found that rhyolite bleaching is a result of Fe evacuation. Along with gold, there are small amounts of sulfides, uranium and rare earth minerals in the bleaching areas. In composition, native gold in bleached rhyolites is not fundamentally different from this in fuchsitic veinlets. Silver, copper, and palladium are established as elements-impurities in it. The deposition of gold in fuchsitic veinlets and areas of rhyolite bleaching was, most likely, due to the manifestation of a single hydrothermal process in the Late Paleozoic. The presence of palladium in native gold, as well as chromium in fuchsite, indicates the important role of deep sources of matter.

Keywords: the Chudnoe deposit, gold, brannerite, coffinite, fuchsite, rhyolite bleaching.

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DOI: 10.19110/2221-1381-2018-12-46-51

The features of the spectra of weakly ordered graphite-like substances upon excitation of Raman scattering by lasers of different wavelengths (633, 515, and 244 nm) have been analyzed. The advantages of the ultra-violet Raman spectroscopy (244 nm) in comparison to visible (633, 514 nm) have been presented. For the first time spectroscopic characteristics of nanocrystalline graphite, glass-like carbon and shungite, obtained on ultraviolet radiation are described. Features of the method of ultraviolet Raman spectroscopy can be useful for carrying out a phase analysis of multicomponent carbon substances containing sp²- and sp³-carbons.

Keywords: Raman spectroscopy, nanostructured matter, graphite, shungite, glassy carbon.

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