Apatites of markedly different chemical composition and origin were studied using 19F magic-angle spinning nuclear magnetic resonance. Synthetic carbonate fluorapatites (CFAp) containing 2.6 to 4.7 wt% F, 0 to 4 wt% CO2 and 0 to 1 wt% Na2О, hydroxylfluorapatite (OH:F ≈ 1:1) containing about 3 wt% Y (Y-HFAp), natural REE-apatites, and CFAp and Y-HFAp heated at temperature from 700 to 1000 oC were researched. The spectra of apatites with isomorphic substitutions show the signals (chemical shift δ) caused by fluoride ions in fluorapatite structure and, possibly, near defects in Ca sites (from −102.5 to −100 ppm), near water molecules (H2Os) incorporated in the channels (about −96.5 ppm), and one or two signals with δх from −91 to −86 ppm. The spectra of synthetic CFAp and Y-НFAр heated up to 900 oС and original natural REE-apatites show two components, δх1 and δх2 shifted with 2 − 3 ppm, in this range. It is shown that the component δx2 is new, it hasn’t been observed in the spectra previously. Signals in the δх range are caused by Fх ions (up to 12% F) whose structural environment is different substantially from the "ideal" fluorapatite structure. It is found that the contents of Fх ions and CO2 in synthetic CFAp correlate linearly. It is shown that Fx (Fх1) ions can occupied sites in the channels near single vacancies Ca, and Fх2 ions — near double vacancies, Ca and anionic those in the channels, in CFAp with the F content not higher than stoichiometric and Y-НFАр. These vacancies can form through different heterovalent isomorphism mechanisms such as РО43− → СО32− and/or Са2+ → M3+ (М = REE, Al, Fe), vacancies in the channels of heated apatites with partial substitutions F → H2Os, OH — through dehydration and/or dehydroxylation.
Проведено исследование фторапатитов (FAp) из сиенитов (FAp s) и карбонатитов с примесью доломита (FAp cd) и пироксенов (FAp c) Черниговской зоны разломов Приазовского блока украинского щита с применением методов ядерного магнитного резонанса (ямр) 1 H, 19 F и 31 P, инфракрасной спектроскопии (икс), FAp s и FAp c ,-рентгенофлуоресцентного анализа (рФа). установлен ряд особенностей структуры и изоморфизма F → он исследованных FAp. в структуру всех образцов внедрены oH-группы, в основном, "изолированные" в окружении ионов F, молекулы H 2 o str в вакансиях структуры, со 3-группы, преимущественно, в-типа, примеси Ree, Sr, Mn и Fe и, возможно, ионы F x вне каналов (≤0,02 apfu). исследованные апатиты различаются содержанием и, частично, составом изоморфных примесей. в апатитах из карбонатитов присутствуют микровключения воды, в FAp s и FAp c-кластеры он•••сl. в FAp cd наиболее высокое содержание воды в разных формах (0,33 wt % oH-групп, по 0,07 wt % молекул H 2 o str и воды в газово-жидких включениях, по данным ямр 1 H) и со 3групп. в FAp s и FAp c содержание oH-и со 3-групп и молекул H 2 o str заметно ниже. сопоставление полученных данных показало, что часть oH-групп и молекул H 2 o str не проявляется в спектрах ямр 1 H из-за наличия в образцах парамагнитных примесей Mn, ряда Ree и, возможно, Fe. наиболее упорядочена структура FAp c с самым низким содержанием oH-и со 3-групп. Предполагается, что кристаллизация исследованных апатитов происходила при относительно высоких значениях PT параметров. Ключевые слова: фторапатит, изоморфизм, ядерный магнитный резонанс, инфракрасная спектроскопия.
The article concerns results of studying two significant seismic events — an explosion (23.09.2020 09:00) and an earthquake (30.09.2020 20:00), which occurred in the area of the city of Kryvyi Rih. There were developed algorithms to process records by the Kryvyi Rih seismic station. There was done a comprehensive interpretation of the seismologic and geological-geophysical data. The seismic events’ coordinates were determined, the quality of seismological data processing was evaluated based on the expert method, the level of trustworthiness of the resulting parameters was estimated. The nature of the eathquake’s origin was analyzed based on the shape and the records’. The structure of the mechanism of the earthquake center shows that this was a natural seismic event of the induced type. The article also provides results of geotectonics study of the region of its origin and shows the connection of the geological structures with the epicenter’s parameters. The parameters of the stress-strain state of the crust in the Kryvyi Rih iron-ore basin are calculated, and the parameters of the epicenter of the induced earthquake (2020.09.30 20:00:40.836, UTC) are established. The experimentally calculated depth of the epicenter of local earthquake coincides with the hypothetical depth of 15 km at the lower edge of faults according to the model of the distribution of the depths of the earthquake hypocenters on the Eastern European platform. The proposed methods and algorithms open new opportunities for modern geophysical research in the long-term seismic hazard assessment of Kryvyi Rih. Meanwhile, for a more precise determination of the place, time and nature of local seismic events in the area it is necessary to develop, here and on adjacent territories, a network of seismic stations capable of recording events of comparable and lesser magnitude.
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