pdf № 313, January

DOI: 10.19110/geov.2021.1.1

The results of palynological study of the Synya Formation (Middle Triassic) in outcrops along the Kydz'rasyu River banks are presented. The published and archival results of previous palynological investigations of the Synya deposits were used as an additional record. It was shown that the species composition of the palynological assemblage (PA) of the Synya Formation on the Kydz'rasyu River fully corresponded to the PA Converrucosisporites conferteornatus — Florinites pseudostriatus and determined the Triassic, Ladinian, age of the enclosing deposits. The results of reconstruction of the growing vegetation testified to the existence of rich and diverse vegetation in the Ladinian Age on the studied territory, where the flora of highly moistened biotopes prevailed.

Keywords: spores and pollen, Synya Formation, Middle Triassic, Ladinian, the Timan-Northern Urals region.

Download full text

 A potentially new mineral, ^M2Na-dominant analogue of eudialyte from the Khibiny alkaline massif, was investigated using the methods of electron probe microanalysis, X-ray diffraction, and IR spectroscopy. The crystal structure was refined to R = 5.7% in the anisotropic approximation of atomic displacements using 2577 independent reflections with F > 3σ(F). The unit-cell parameters are: a = 14.277(1), c = 30.400(1) Å, V = 5328.7(1) ų; the space group is R-3m. The idealized formula of the mineral is (Z = 3): Na₁₄Ca₆Zr₃[Na₂(Fe,Mn)][Si₂₆O₇₂](OH)₂(H₂O_1.0Cl_0.6S^2-_0.5)(OH,H₂O)_2.5. Distribution of cations in the M2 micro-region is established: Fe in the flat-square coordination, Mn in the square pyramid and Na in the seven-vertex polyhedron. A comparative analysis of crystal chemical features of eudialyte ^М2Na-analogue samples from the Khibiny-Lovozero alkaline complex and Ilimaussaq alkaline pluton, Greenland is given. The mechanism of blocky isomorphism with the replacement of ^IVFe²⁺ with ^VIINa in the M2 micro-region is discussed. IR spectra of the ^М2Na-dominant eudialyte analogue are given: essentially hydrated sample (Na,H₃O,H₂O)₁₅Ca₆Zr₃[Na₂Fe][Si₂₆O₇₂](OH)₂Cl∙2H₂O from Ilimaussaq, less hydrated ^М2Zr-bearing sample (Na,H₃O)₁₃(Ca₄Mn₂)Zr₃(Na₂Zr)[Si₂₆O₇₂](OH)₂Cl∙H₂O from Lovozero and low-hydrated sample Na₁₄Ca₆Zr₃[Na₂(Fe,Mn)][Si₂₆O₇₂](OH)₂Cl(OH,H₂O)₃ from Khibiny studied in this work.

Keywords: mineral, eudialyte group, crystal structure, IR spectroscopy, isomorphism, M2 key site, Khibiny alkaline complex.

DOI: 10.19110/geov.2021.1.2

Download full text

DOI: 10.19110/geov.2020.1.3

The results of studying the lithological and geochemical characteristics of sandstones of the Upper Devonian Tayaokuyakhinskaya Formation in the southeastern part of the Kanin Nos Peninsula are presented. The accumulation of sandstones of the Tayaokuyakhinskaya Formation occurred in the absence of volcanic activity in a shallow basin with small periodic fluctuations in sea level, which led to a change in the degree of maturity, sorting, and the ratio of clay and sandy components in the rock. The accumulation of the psammitic strata occurred due to the destruction and redeposition of weakly weathered sedimentary rocks in a moderately warm climate. It was established that the formation of the composition of sandstones was influenced by at least two sources of clastic material — garnet-bearing crystalline shales and feldspar-quartz sandstones metamorphosed into the greenschist facies. The latter, most likely, were the source of the indicative gold contents found in the Devonian clastic rocks.

Keywords: sandstone, chemical composition, clastic material, source of demolition, area of formation, conditions of sedimentation.

Download full text

DOI: 10.19110/geov.2020.1.4

The evidence of the existence and fractionation of the global magmatic ocean on the Earth allows us to distinguish two stages of the formation of diamonds of increased size. The largest giant diamonds arose at an early stage of crystallization and fractionation of the peridotite layer of the magmatic ocean, since its bottom layer at that time was blocked by still hot upper ones and therefore cooled and crystallized very slowly and long. The mafic composition of this layer and the low viscosity of its magmas caused mainly octahedral cutting of the formed giant diamonds. Later crystallized mainly rhombododecahedral diamonds have increased coarseness due to the formation mainly by the growth of early octahedral crystals.

Keywords: diamond genesis, giant diamonds, magmatic ocean, hot accretion.

Download full text

DOI: 10.19110/geov.2020.1.5

The article is devoted to the scientific activities of one of the first Russian women geologists, paleontologists — Tatyana Alekseevna Dobrolyubova in connection with the anniversary date — the 130th birthday anniversary. A whole stage in the history of geological studies of the natural resources of the Northern Urals, as well as paleontological studies of the Carboniferous and Permian corals of the Russian Platform and the Urals, are associated with her name. The most important directions of her research and the most significant achievements, as well as the stages of her life, are briefly highlighted.

Keywords: women-geologists, T. A. Dobrolyubova, Pechora Territory, paleontology, corals.

Download full text

DOI: 10.19110/geov.2020.1.6

The paper presents Tatyana V. Maydl’s researches of formation and patterns of distribution of natural reservoirs in carbonate deposits of the Timan-Pechora oil and gas province. Tatyana Viktorovna Maydl is a recognized specialist in oil and gas geology. Her significant contribution to the development of the theoretical base of formation of carbonate deposits in the region, reconstruction of sedimentation conditions, finding degree of influence of secondary transformations on the reservoir and filtration properties of carbonate rocks, development of the basis for geological models of carbonate reservoirs, are analyzed. In the field of studying the morphology of the void space in low-capacity carbonate reservoirs, T. V. Maydl found that in the Lower Silurian dolomites with a shadow biohermal structure had the best filtration features, and in the Upper Silurian — bioclastic limestones. The main volume of the void space in the first type is associated with caverns and cracks, in the second — with matrix porosity. We showed that the results of T. V. Maydl’s work were not only of theoretical, but also of practical importance.

Keywords: hydrocarbons, carbonate rocks, oil and gas reservoirs, pore space, T. V. Maydl.

Download full text