A new line in investigation of physical properties of rocks and minerals at high pressures and temperatures

S. M. Kireenkova, G. A. Efimova
2003 Russian Journal of Earth Science  
The decisive problems at present in the experimental investigation of rocks and minerals at high pressures and temperatures are the problems of studying processes which are going on inside using various physical methods. The most important avenue of experiments is investigation of changes of physical properties of the rocks and minerals at high pressures and temperatures. The majority of papers in this line give a quantitative assessment of the physical characteristics, establish factors these
more » ... lish factors these characteristics depend on, and major patterns of their variation at high pressure and temperature parameters. Aside of this, abnormal manifestations of physical properties of the rocks were revealed prior to destruction, in the dehydration processes and in the phase changes [Levykin, 1991; Parkhomenko, 2000; Volarovich et al., 1974 Volarovich et al., , 1975 Volarovich et al., , 1979a . These investigations suggested that the abnormal changes of the rock physical parameters at high pressures and temperatures indicate to one or another process and are connected with the microstructure changes in the rocks and minerals. With allowance for the main direction, problems were set before the laboratory working on simulation and analysis of processes in the seismic zones to investigate a physical nature of the earthquake preparation processes and the attendant forerunners, at different scale levels, on the basis of experimental investigations of the rock and mineral properties and their variation at high pressures and temperatures. The neutron diffraction method, as the method possessing optimum capabilities among other microstructure methods of investigation of the matter, was selected as a physical investigation method. Calcite, that have received the most study at high pressure and temperature parameters and which is prevailing in the Earth, was selected as the first object of investigation. First, we have made a set of tests on the calcite containing rock -marble of different graininess, with the purpose of assessing capability of the neutron diffraction method for investigation of processes in the rocks. It is well known that reversible polymorphous transitions take place in the marble, and it should be noted that these are observed under certain loading conditions, while they are not observed under other loading conditions. Therefore, the marble samples were tested under different loading conditions. The tests were made on a solid phase cylinder-piston machine up to 1.6 GPa and on a high-pressure hydraulic machine at a constant hydrostatic pressure 10 MPa with an additional uniaxial compression at a speed of 1.8×10 −6 mm/s [Efimova et al., 1998 ]. At the beginning reading was made of the neutron diffraction spectra on each sample and complete pole figures were obtained showing orientation of grains in the sample under investigation in corpore and not in one plane, as a conventional microscopy allows to have. Afterwards, the samples were subjected to different loading conditions and new spectra were recorded after the tests and new pole figures were obtained. The neutron diffraction measurements were made in the UINI (Dubna), on the NSVR spectrometer, sheaf no. 7 of the IBR-2 reactor. A time-of-flight neutron diffraction method was employed for the textural measurements. Two transitions at 0.4 MPa and at 1.6 MPa were 283
doi:10.2205/2003es000127 fatcat:s5xypjdzkzfuhjfkslf5u3mee4