Genetic Role of Calcium Content in Olivine Crystals of Ultramafic and Mafic Rocks
Ponomarev Georgy,
Vladykin Nikolay,
Radomskaya Tatyana
Issue:
Volume 9, Issue 2, June 2020
Pages:
16-26
Received:
14 April 2020
Accepted:
15 May 2020
Published:
29 May 2020
Abstract: The results of genetic systematization of olivine compositions formed both under experimental conditions and its natural differences from rocks of basic and ultramafic compositions of various depth facies and formed in various geodynamic settings are presented. Similar work [53], performed in the 70s of the last century and has been actively cited to this day. Generalization of the subsequent accumulated data showed the error of one of the main conclusions in this work – the dependence of the Cao content in olivine on the hydrostatic pressure during its formation from the melt. According to experimental studies conducted in recent years, up to a pressure of 29 GPA, the content of calcium in olivine, which has grown from the main-ultrabasic melts, does not depend on the pressure and is not lower than 0.1 wt.% CaO. Experiments in solidus conditions involving fluid and natural data have demonstrated that one of the leading factors affecting the calcium content in olivine are metasomatic processes that lead to the removal of calcium from olivine crystals. The role of metasomatic transformations of olivine in terms of calcium content, despite the apparent insignificance of secondary changes in it, is clearly visible in the examples of basalts and gabbro of the modern oceanic crust and the same facies differences in ophiolite complexes. The wide development of metasomatic transformations of igneous rocks of various facies and ages indicates the need to take into account the calcium content in olivine as an equilibrium criterion when calculating temperatures and pressures for paragenesis involving olivine. Olivines, which are part of ultrabasic xenoliths carried out by sub-alkaline magmas, including those carried out by kimberlites, are overwhelmingly represented by low-calcium differences. Low levels of calcium in olivines from these mantle fragments suggest that magmatic melts of the main-ultramafic compositions are not in equilibrium with the mantle substance to depths of about ~ 200 km, and possibly more. Among the compositions of olivines from fresh effusive rocks, its inclusions and microlites are mostly represented by calcium-containing differences. Only in kimberlites, almost all the differences in its crystals (inclusions, microlites) in the rock are represented by low-calcium differences. Olivines included in diamonds are also overwhelmingly represented by low calcium differences. This suggests that the composition of kimberlite olivine is associated with metasomatic transformations, and the growth of diamonds from kimberlites is due to the fluid. Inside the natural single crystals of diamond, there are polymetallic films buried in the body of crystals. Similar films were formed on the faces of diamond crystals formed in the Lav pores (that is, almost on the surface of the day) in 2012-13 of the Tolbachinsky Fissure eruption. These data allow us to create artificial "soft" conditions (CVD, solution, etc.) for the growth of single-crystal diamond films on similar polymetallic or single-element films. For these purposes, elements such as zirconium, dysprosium, erbium, and others can be used.
Abstract: The results of genetic systematization of olivine compositions formed both under experimental conditions and its natural differences from rocks of basic and ultramafic compositions of various depth facies and formed in various geodynamic settings are presented. Similar work [53], performed in the 70s of the last century and has been actively cited ...
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Calculation of the Chemical Composition of Air - PMMA Mixtures Thermal Plasmas
Kagoné Abdoul Karim,
Kohio Nièssan,
Yaguibou Wêpari Charles,
Koalaga Zacharie,
Zougmoré François
Issue:
Volume 9, Issue 2, June 2020
Pages:
27-35
Received:
6 May 2020
Accepted:
27 May 2020
Published:
3 June 2020
Abstract: Knowledge of the chemical composition of plasma is necessary for calculations and modeling in thermal plasmas. Indeed, from the knowledge of this composition we can calculate the thermodynamic properties, the transport coefficients and the radiative properties of a plasma medium. In this work, we propose to study at thermodynamic equilibrium the influence of pressure and of the PMMA polymer on the composition of the plasma of the Air - PMMA gas mixture. We are studying in particular the evolution of the density of the species created in this plasma as a function of temperature (5000 - 30000 K) and pressure (1 bar - 10 bar) for variable mixtures at thermodynamic equilibrium. When we want to take into account a large number of chemical species in the plasma, two main methods are usually used, one is based on the law of mass action and the other on the minimization of Gibbs’ free enthalpy. In our study, we used the mass action law method to calculate the composition of plasma. The results obtained show that when the plasma is in thermodynamic equilibrium the densities of the different species present in the plasma are only a function of the temperature, the pressure and the percentage of the polymer in the mixture.
Abstract: Knowledge of the chemical composition of plasma is necessary for calculations and modeling in thermal plasmas. Indeed, from the knowledge of this composition we can calculate the thermodynamic properties, the transport coefficients and the radiative properties of a plasma medium. In this work, we propose to study at thermodynamic equilibrium the in...
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Reactions’ Mechanisms and Applications of Hydrogen Peroxide
Gheorghe Duca,
Sergey Travin
Issue:
Volume 9, Issue 2, June 2020
Pages:
36-44
Received:
15 May 2020
Accepted:
1 June 2020
Published:
17 June 2020
Abstract: Hydrogen peroxide is a key substance in the appearance of life and maintenance of the life-supporting conditions on the Earth. Electron transfer processes between H2O2 and various reducers are of major interest for the environment, natural life, technology, etc. An overview of structure, proprieties and main reactions of hydrogen peroxide in model and real systems is presented. The authors try to find the answers to the following questions: why this substance has the unique and specific dual reduction-oxidation properties, what is the connection between its structure and reactions, what role it plays in the catalytic reduction processes occurring in the natural environment and technological systems, accompanied by the formation of intermediate compounds, active radicals, complete and partial charge transfer complexes, etc. The thermodynamic possibility of the synchronous two-electron transfer during the inner sphere reaction with the involvement of metal ion complexes capable of changing the valence by two units is discussed. The role of the partial charge transfer structures which combine the properties of the initial reagents and the expected reaction products is demonstrated. Such complexes can be decomposed both reversibly and irreversibly. In case when the single-electron transfer is thermodynamically preferable, the main oxidizing particle is OH-radical, capable to interact non-selectively with almost all the water-soluble organic substances. Special attention is paid to the photo initiation of peroxidase transformation processes. The results of our multi-annual research of these issues are reported.
Abstract: Hydrogen peroxide is a key substance in the appearance of life and maintenance of the life-supporting conditions on the Earth. Electron transfer processes between H2O2 and various reducers are of major interest for the environment, natural life, technology, etc. An overview of structure, proprieties and main reactions of hydrogen peroxide in model ...
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