GEODYNAMICS

Abstract

Determining the physical parameters of geomaterials under high temperature and pressure conditions is necessary in connection with the fundamental issues of geology and geophysics. It is also aimed at solving applied problems, such as establishing relationships between physical parameters and chemical components of rocks under the earthly conditions of temperature and pressure. The purpose of the paper is to study the peculiarities of the influence of chemical components on the elastic and density properties of igneous and metamorphic rocks of the continental and oceanic lithosphere under high temperature and pressure conditions. The elastic and density characteristics of the rocks of the continental and oceanic lithosphere were determined by the ultrasonic pulse method. The experiments were carried out in a high-pressure solid-phase installation of a cylinder-piston type. The technique provides for the simultaneous determination of the longitudinal and transverse waves velocity and density in the course of one experiment on one rock sample at high temperature and pressure conditions up to 1.5-2.0 GPa. Based on an experimental study of the elastic and density properties of the rocks of the continental and oceanic lithosphere, the research revealed a qualitative connection between these parameters and chemical composition of the samples under high temperature and pressure conditions. It is first established that the studied rocks demonstrate regional dependence in the influence of oxides on the elastic wave velocity and density magnitude. Therefore they increase with the growing pressure in some areas, and decrease in others. This phenomenon is explained by the difference in the atomic structure of matter. It was revealed that in the section of the lithosphere, the speed and density of elastic waves increase with depth. Moreover, chemical composition of rocks changes from acid to medium, basic, and, finally, ultrabasic composition. The relationship of the chemical composition of rocks and minerals with elastic and density properties makes it possible to directly search for solid minerals.