Melting and Crystallization of Moderately Alkaline Volcanic Rocks: Physicochemical Modeling and Experimental Study
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ICAL METHODS OF INVESTIGATION
Melting and Crystallization of Moderately Alkaline Volcanic Rocks: Physicochemical Modeling and Experimental Study V. A. Kreneva, N. N. Efimova, P. N. Vasil’eva, D. F. Kondakova, E. N. Pechenkinaa, and S. V. Fomicheva, * a
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia *е-mail: [email protected] Received March 4, 2020; revised April 10, 2020; accepted April 27, 2020
Abstract—We studied by physicochemical modeling (PCM) how the temperature and redox properties of the crystallization atmosphere affect the equilibrium compositions of product phases using trachyandesibasalt as an example. The chemical composition of rock-forming minerals and their influence on the properties of rocks are presented. The heating, melting, and crystallization features of trachyandesibasalt are considered taking into account external conditions and the mutual influence of the minerals present in the rock. Temperature-dependent magnetization is determined for various fractions of the studied rock. The fundamental possibility is shown, and recommendations are given, for choosing methods to modify the chemical and mineral composition of trachyandesibasalt. Keywords: trachyandesibasalt, mineral composition, melting, magnetic properties DOI: 10.1134/S0036023620090107
INTRODUCTION The recent years have seen the development and expansion of the physicochemical modeling (PCM) of melting and crystallization of natural inorganic systems represented by various types of igneous rocks [1– 5]. This situation is due to the advances in computer technologies, the expansion of thermodynamic databases, and the creation of new software for calculating the phase states of complex heterogeneous systems. This brought the design of computer physicochemical models to a qualitatively new level taking into account the basic requirements of chemical thermodynamics. Computer simulation has become the fastest and most effective way to gain information about the equilibrium phase compositions of complex heterogeneous systems [6]. In addition, other igneous and metamorphic rocks came into use along with basalts with the development and improvement of technologies [7]. Currently, basic picrobasalts, pyroxenite-hornblendites, gabbroids, amphibolites, trachybasalts, andesibasalts, andesites, diorites, monzonites, trachyandesibasalts, syenites, and other rocks are attracting attention in addition to basalts. APPLICATION OF PCM METHODS The subject matter of the study reported here is trachyandesibasalt, a medium volcanic rock of the moderately alkaline series, which is identified by the fol-
lowing features: 50 ≤ SiO2 ≤ 67 and 5 ≤ (Na2O + K2O) ≤ 12 [8]. In its chemical composition trachyandesibasalt is an equivalent of plutonic rocks, namely, diorite [3] and monzodiorite [4], but differs sharply from them in mineral composition. The chemical composition of a crystalline trachyandesibasalt sample represented in an oxide form is (wt %): SiO2, 56.59; TiO2, 2.76; Al2O3, 15.97; Fe2O3, 9.
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