Laboratory Possibility for Revealing Stages and Conditions of High-Temperature Firing of Mud Breccia Using Acoustic Emission

• Published in: Seismic instruments 2020-07, Vol.56 (4), p.399-410
• Main Authors: Kaznacheev, P. A., Beloborodov, D. E., Maibuk, Z.-Yu. Ya, Matveev, M. A., Afinogenova, N. A.
• Format: Article
• Language: English
• Subjects: Acoustic emission; Activity patterns; Bound water; Breccia; Brittleness; Chemical analysis; Earth and Environmental Science; Earth Sciences; Elastic waves; Emission analysis; Geophysics/Geodesy; Heating; High temperature; High temperature effects; Hydrocarbons; Laboratories; Mud; Mud volcanoes; Oxidation; Oxidation-reduction potential; Redox reactions; Temperature effects; Thermal expansion; Volatile hydrocarbons; Volcanic activity; Volcanic fields; Volcanoes; Wave attenuation
• ISSN: 0747-9239; 1934-7871
• DOI: 10.3103/S0747923920040052

The process of laboratory high-temperature effect on the sample of mud breccia, collected in the Bulganak mud-volcanic field, was investigated using acoustic emission (AE) tracking. The laboratory study aimed to simulate the heating of breccia in natural conditions during a flaming eruption of the mud volcano, associated with the ignition of accompanying volatile hydrocarbons. The sample underwent several heating-cooling cycles with different maximum temperatures being attained (up to ∼750°C). Several characteristic stages, according to the analysis of variations in AE activity during the heating process, were identified and presumably compared to the characteristic physical and chemical alterations. During heating, two processes simultaneously developed to determine the changes in the AE activity pattern. First, due to thermal expansion with a simultaneous increase in brittleness of the material, microfracturing was activated. Second, a decrease in attenuation of elastic waves took place. We assumed that the main changes were associated with the loss of bound water and oxidative processes. When discussing the results, we compared them with the data on structural and chemical analysis. Inhomogeneous physical and chemical changes in the specimen’s thin sections, associated with the inhomogeneities of oxidation-reduction conditions, were recorded. The results indicate the influence of both temperature and oxidation-reduction conditions on physicochemical transformations in mud breccia, helping to assess the heating conditions and the composition of the associated hydrocarbons during flaming eruptions.