VIII. Methods and techniques of experiment

A number of experimental apparatuses has been designed at the Institute of Experimental Mineralogy for experimental investigations in mineralogy, new methods of substance analysis have been developed. The most essential of them are as follows:

Chichagov A.V., Dilanyan R.A., Dokina T.N., Drozhzhina N.A., Samokhvalova O.L., and Ushakovskaya T.V. The information processing system on crystal structures of minerals (MINCRYST).

The MINCRYST is the original self-consistent combination of the database on crystal structures of minerals, the subordinate database on calculated polycrystal standards, and applied software package.

The MINCRYST is a universal system that contains data on chemical composition, crystal structures, and X-ray diffraction properties of minerals. These data characterize a mineral both as a single crystal (basic parameters are the coordinates of atomic sites) and a polycrystal (basic parameters are interplanar spaces).

The MINCRYST is a complex system, for it employs the newly created information resources (Database on Crystal Structures), enlarges the volume of the information resources by means of its calculation tools (automatically formed Subordinate Database on Polycrystal Standards and calculated Information Cards), and contains the Applied Software Package, which allows using the newly created resources for analytical aims (crystal chemistry and X-ray diffraction analyses).

The Applied Software Package based on the Database on Crystal Structures offers the following opportunities:

    (a) Calculation of the information cards containing complete X-ray diffraction data of minerals (TRANS + XRAYPOL software);

    (b) Calculation of X-ray diffraction parameters of a polycrystal standard and creation of the Subordinate Data-

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    base of Polycrystal Standards (TRANS + XRAYPOL and CHAIN softwares);

    (c) Calculation and visualization (on the monitor) of crystal structure models; calculation of bond lengths and angles (CRYSTRIC software);

    (d) Calculation and visualization of the entire X-ray patterns of a polycrystalline phase or polycrystalline mixtures with given phase proportions (MIXIPOL software);

    (e) Quantitative standard-free X-ray diffraction analysis of mineral mixtures with modeling the entire X-ray patterns for the polycrystalline phases constituting the mixture (QUANTPOL software);

    (f) Qualitative X-ray diffraction analysis of minerals and mineral mixtures using the Subordinate Database on Polycrystal Standards (OPTIDENT and MIXIDENT softwares).

A significant advantage of the MINCRYST is that it is controlled within the Unified Data Processing System (EIVS, DELPHI, WINDOWS). EIVS-96 allows the combined data storage and operation of the Database on Crystal Structures and the Subordinate Database on Polycrystal Standards and provides all the necessary functions (import, export, edition of records, data retrieval based on sign combinations, etc.). Moreover, information cards and exported input files for the Applied Software Package can be calculated by employing the TRANS+XRAYPOL software. The format of the MINCRYST Database corresponds to PARADOX 5.0 for WINDOWS. The inquiry service is realized in SQL language. EIVS-96 (= MINCRYST-96) can be operated both at a personal computer or in a local network.

Least requirements to the computer used: PC IBM 486 - compatible; memory - 8 Mb; operation environment - WINDOWS 3.1 or 3.11. Owing to its high-level software support, the MINCRYST can be linked to a database of higher rank, such as ORACLE or INFORMIX.

By the beginning of 1997, the MINCRYST Information Base has contained 3800 records in the Database on Crystal Structures of minerals. By the end of 2000, the MYNCRYST is expected to contain about 5000 records. The database will include the abstracts of all published papers dealing with decoding crystal structures of minerals.

References:

  1. Chichagov A.V., Belonozhko A.B., Lopatin A.L. Dokina T.N., Samokhvalova O.L., Ushakovskaya T.V., and Shilova Z.V. (1990) The Information Processing System on Crystal Structures of Minerals (MINCRYST). // Kristallografiya, vol. 35, no. 3, pp. 610-616.

  2. Chichagov A.V. (1994) Information-Calculating System on Crystal Structure Data of Minerals (MINCRYST), Materials Science Forum Trans. Tech. Publications, Switzerland, v. 166-169, pp. 193-198.

Chudinovskikh L.T. High-pressure-high temperature experimental studies on the physical properties of deep-seated minerals using a laser-heated diamond anvil cell.

The pressure dependences (up to 10 GPa) of the unit cell parameter (a) and relative volume (V/Vo) of synthetic pyrope were determined by the energy-dispersive X-ray diffractometry. By the application of the Birch-Murnaghan equation to the data obtained, the parameters of the equation of state were calculated: isothermal bulk modulus Ko = 172 ± 4 GPa and its first pressure derivative Ko' = (dK/dP) = 4.3 ± 0.8 [1, 3].

The parameters of the equations of state for MFCl compounds (M = Ba, Sr, Ca) and BaFBr were experimentally obtained up to 50 GPa using a diamond anvil cell and synchrotron radiation (HASYLAB DESY, Hamburg, Germany). Structural phase transitions of BaFCl and BaFBr were found at 21 and 27 GPa respectively, and an appropriate semiquantitative model was proposed [4]. The compressibilities of magnesiwustite (Mg0.85Fe0.15O) and wustite (Fe0.92O) were investigated to 30 GPa. The structural transition from cubic to hexagonal symmetry occurs in wustite at 6 GPa, the transition pressures differing for the phases with different stoichiometry [2].

New experimental data were obtained as to the coesite-stishovite phase transition within the pressure range 9-12 GPa and temperature range 2300-2630oC. Equilibrium was attained by laser heating in a diamond anvil cell; resulting phases were quenched at a given pressure and identified by Raman spectroscopy. The slope of the coesite-stishovite phase boundary obtained is described by the equation P(GPa) = 8.1 ± 0.001T(oC) [5].

A new method was developed for determining the rheologic properties of minerals based on the measurement of the optical transmittance of polycrystalline samples, which are placed between the diamond anvils when loaded. The equipment enabling the optical measurements and double-sided laser heating was designed. The curves of optical transmittance versus pressure at room temperature were obtained for the nine main mantle minerals, and their yield strengths were estimated. The plasticity-crystal structure systematics for minerals studied was revealed. The yield strength values were obtained for grossular and olivine at high temperatures (up to 1500 K). The new method for determining the yield strengths of polycrystalline materials offers wide opportunities for studying the mechanisms of plastic flow of minerals and rocks under the conditions simulating the earth interior [6].

References:

  1. Chudinovskikh L.T., Zharikov V.A., Nekrasov A.N., Kalinin V.A., Nasimov R.M., and Bayuk I.O. (1993) Compression of Synthetic Pyrope up to 10 GPa. // Nat. Acad. Sci. Lett., V.16, N.1.

  2. Zerr A., Chudinovskikh L.T., Li Zhang, Reichmann H. -J. and Boehler R. (1993) Pressure Induced Anisotropy of Argon, Pressure Scale and Equation of State (NaCl, Ar, and Ruby; (Mg,Fe)O; wustite-Fe0.92O), HASYLAB Jahresbericht, Hamburg, pp. 650-651.

  3. Zharikov V.A., Chudinovskikh L.T., Nekrasov A.N., Dem'yanets Yu.N., Kalinin V.A., Nasimov R.M., and Bayuk I.O. (1994) The Use of a Diamond Anvil Cell for Studying the Thermodynamic Properties of Miner-

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als. //Eksperimental'nye problemy v geologii, Moscow: Nauka, pp. 71-79.

  1. Shen Y.R., Englisch U., Chudinovskikh L., Porsch F., Haberkorn R., Beck H.P., and Holzapfel W.B. (1994) A Structural Study on the PbFCl-Type Compounds MFCl (M = Ba, Sr, and Ca) and BaFBr under High Pressure. // J. Phys.: Condens. Matter 6, pp. 3197-3206.

  2. Serghiou G., Zerr A., Chudinovskikh L., and Boehler R. (1995) The Coesite-Stishovite Transition in a Laser-Heated Diamond Cell, Geophys. Res. Lett., vol. 22, no. 4, pp. 441-444.

  3. Chudinovskikh L.T. and Boehler R. ( ) Optical Transmittance and Yield Strengths of Mantle Minerals. //Eksperimental'noe i teoreticheskoe modelirovanie protsessov mineraloobrazovaniya, Moscow: Nauka (in press).

Osadchii Eu.G. Apparatuses and methods for measurements of oxygen and sulfur activities in high temperature fumaroles.

Modern methods and apparatuses have been developed to measure in situ oxygen and sulfur activities in high temperature fumaroles [1]. The results obtained were compared with the data on chemical compositions of gas streams.

In order to determine sulfur fugacity in a gas phase in the temperature range 100-450oC, new electrochemical sensors based on the solid Agi electrolyte and sensors for the determination of oxygen fugacity based on the zirkonium ceramics with oxygen-ionic conductivity have been designed and tested. These sensors were used in the measurements of oxygen and sulfur activities in high temperature fumaroles of the volcanos Kudryavy (is.Iturup), Papandayan, and Merapy (Indonesia) [2].

Laboratory measurements of fO2 in the changed and unchanged andesite-basalt lavas from the diatremes of high temperature fumaroles (to 1000oC), in which field measurements were performed, as well as calculations on chemical composition of fumarole streams showed that lavas are not in equilibrium with gas phase and fO2 in gas is 1-2 logarithmic orders higher than in lava of the latter eruption.

Sorokin V.I. , Osadchii Eu.G., Beloborodov S.M. Development for the experimental study of mineral equilibria by the methods of high temperature electrochemistry.

For the experimental study of mineral equilibria by the methods of high temperature electrochemistry the following apparatuses have been designed:

- the cell for differentiated-thermal analysis of minerals melting and study of redox equilibria by the method of electrochemical cell on the high gas pressure apparatuses;

- telescopic device for the submarine habitable apparatuses MIR with a set of high temperature ionselective electrodes and a cartridge of replaceable bathometers (500cm3) for measurements of hydrochemical parameters: pH, Eh, pNa, pCl, pH2S, ToC, P at the depths to 6000m;

- e.m.f. cell of gas pressure to 8 kbar with the common gas space for the determination of the volume effects of solid phase reactions (calibration of geobarometers).

-hydrothermal isobaric cell GIYA-2 designed for the potentiometric measurements at P to 70 atm. and T to 3000oC as well as for calibration and certification of high temperature potentiometric probes and transducers;

- high temperature galvanic cell of high gas pressure with independent gas space for the investigation of oxygen dependent equilibria.

References:

  1. Lunin S.Eu., Osadchii Eu.G. (1993) Solid state e.m.f. studies in the systems Ag-Sb and Ag-Sb-S.// Experiment in Geosciences, Vol.2., N 1, pp. 20-23.

  2. Rosen E., Osadchii Eu., and Tkachenko S. (1993) Oxygen fugacities directly measured in fumaroles of the volcano Kudryavy (Kuril Isles). // Chemi der Erde, V.53, s. 219-226.

Romanenko I.M. Newly developed techniques in the area of X-ray spectral microanalysis.

A number of new techniques for the X-ray spectral microanalysis were developed in the Institute of Experimental Mineralogy, RAS:

(1) The universal method for quantitative evaluation of iron valence based on the difference of absorption coefficients of Fe L{alpha}-reflex between standard synthetic magnetite or hematite and sample. This technique can be applied to a wide range of samples, since the similarity of the standard and sample compositions is not necessary. For the precise adjustment of the spectrometer is required, the method can be realized only with automatic equipment.

(2) The X-ray microanalysis of carbon from carbonates and carbides. Carbon-sprayed samples are used. The method is based on the isolation of the carbon film reflex out of the total carbon reflex.

(3) Detection of fluorine in apatite and silicates at a low electron probe energy (10 keV). The background fluorine level can be concurrently measured with a Camebax microanalyzer without shifting the probe off the analytical line.

(4) X-ray microanalysis of impurity elements (Mg, Al, Cu, Si, Ni, Mo, V, Mn, Ti, Cr) in magnetite with wave spectrometers. Detection limit ranges from 0.01 to 0.07 wt % depending on element determined. The technique is based on the measurement of the background signal without shifting the probe off the analytical line, which enables the determination of low element contents with high accuracy.

References:

  1. Reed S.J.B., Romanenko I.M. (1995) Electron Probe Microanalysis, Advanced Mineralogy v. 2, Methods and Instruments, Ed., Marfunin, A.S., Springer-Verlag, Berlin, Heldeberg, , vol. 2, pp. 240-247.

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