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Influence of crystal chemical features, temperature and pressure on the isomorphism of elements of the iron group in rock-forming minerals of igneous and metamorphic origines

ABSTRACT

The report on scientific project: 253 p., 111 figs., 39 tables, 285 references.

The aim of the work is investigation of features of isomorphic entering of transition metals ions in structure of minerals.

The object of investigation are transition metal ions in natural silicates and oxides of magmatic and metamorphic geneses and their synthesized analogous.

The methods of investigations are optical absorption and diffuse reflectance spectroscopy, including those at different temperatures and pressures, photo- and X-ray luminescence, Fourier-transform infrared spectroscopy (FTIR), high-pressure synthesis, the classic chemical and microprobe analyses.

The transition metal ions, predominantly Ti⁴⁺, Cr³⁺, Fe²⁺, Fe³⁺, because just they constitute the major part of the transition metal ions in natural crystals, participate in many processes of minerals and rocks formations and cause coloration, thermal and electric conductivity and other properties of minerals, rocks, geological complexes and geological landscapes on the whole. Because of the specificspectroscopic features and electronic structure, Cr³⁺ was used asa model ion, particularly for studying the temperature and pressure effect on dimension and local symmetry of structural Cr³⁺ - centered octahedra and character of chemical bonding in them, phenomenon of local structural relaxation and deviationsfrom Vegard’s rule, influence of pressure on solubility of Cr3+ in natural solid solutions, clasterization at isomorphic substitutions etc. The phenomenon of Mg, Fe²⁺ - ordering in annealedolivines and the appearance of this effect in natural crystals of various geneses were studied by optical absorption and FTIR spectroscopies. It was established that a weak ordering of Fe²⁺ as in M1, as in M2 site takes place, the phenomenon, which is most likely caused by different speed of samples’ cooling after crystallization. On the base of experimentally obtained dependence of concentration of isomorphic admixture of titanium on the temperature of crystallization at different pressures, the high-temperature rutile-quartz geothermobarometer is proposed for approximate evaluation of PT-condition of crystallization of quartz-bearing rocks.

Authors:

Taran Mykhailo Mykolaiovych

Tarashchan Arkadii Mykolaiovych

Khomenko Volodymyr Mykhailovych

Other authors:

Keywords:

isomorphism, transition metals, rock-forming silicates, temperature, pressure

Head of the research:

Taran Mykhailo Mykolaiovych

Registration Card (RC):

0106U000682

Execution period of the research:

2006 - 2010