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Information × Registration Number 0222U001843, 0120U000193 , R & D reports Title Optical spectroscopy study of the upper mantle high-pressure minerals and their synthetic analogues by means of an authomized single-beam optical microspectrometer. popup.stage_title Head Taran Mykhailo M., Доктор геологічних наук Registration Date 03-02-2022 Organization M. P. Semenenko Institute of geochemistry, mineralogy and ore formation popup.description2  High-pressure natural and synthesized β- and γ-modifications of olivine (Mg, Fe)2SiO4, the minerals, which in accordance with existing theories are predominant constituents of the transition zone between upper and lower mantles of Earth (the depth from 410 to 660 km) were studied by a series of spectroscopic methods, mainly by optical absorption spectroscopy, and in lesser extent by Furrier infrared and Moessbauer spectroscopies. Particularly, ringwoodite, γ-(Mg, Fe)2SiO4, is regarded as the most probable constituent of the low part of the transition zone. Because of that investigations of this mineral is important for understanding and prediction of geophysical characteristics of the earth depths. It is established that under hydrostatic compression up to ~13 GPa and then consequent released to atmospheric pressure of ringwoodite there were changes in the spectra and related changes in the crystal color. This is a clear indication that some Fe2+ was oxidized to Fe3+. The spectra of both ringwoodite and wadsleyite change after annealing in air at temperatures up to 300 C. The intensities of electronic spin-allowed bands of Fe2+ decrease and the intensity of the charge-transfer electronic transition O2– -> Fe3+, as given by the low-energy absorption edge in the UV region, increases. These crystal-chemical changes are shown by a weakening of the blue (ringwoodite) and green (wadsleyite) colors and a concomitant increase in yellowish tints. The effects of Fe2+ oxidation to Fe3+, upon decompression from high pressures as well as through annealing at relatively low temperatures, can cause the disintegration of both phases. Thus, both minerals have not yet been reliably identified at near surface Earth conditions after originating from deep-seated volcanism or deep subduction zone processes. Product Description popup.authors Kylishova Emiliya Pavlivna Manzyuk Lyubov Pavlivna Steshyn Vitalij Andriyovich Taran Mykhailo Mykolayovych Tarashchan Alla Yakivna Tarashchan Arkadij Mykolayovych Khomenko Volodymyr Mykhailovich popup.nrat_date 2022-03-09 Close