| Keywords |
Petrophysic, hydrothermal, changes, volcanic rocks, modeling, Iceland, Kamchatka, basalts, obsidian, tuffs, hyaloclastites |
| Abstract |
The purpose of this work is to study the character and dynamics of volcanic rock changes by simulating hydrothermal transformation conditions. Tasks performed include carrying out a series of autoclave experiments changing temperature, pressure and solution compositions. Methods include preparing rock samples; studying chemical and mineral composition, structure and properties of rocks and solutions before and after experiments. The following properties of rocks were investigated: density (bulk, specific), porosity (total, effective), hygroscopy, velocity of longitudinal and cross-section waves, effect hygroscopy, geomechanical characteristics (compressive and tensile strength), softening factor, magnetic susceptibility. The first similar experiments were conducted in 2006 (Nuzhdaev and Shanina, 2006). In this work 28 experiments are consideried that were carried out while altering the following parameters: temperature 200, 300 and 450 ºÑ; pressure 16, 86 and 1000 bars; four solutions (1 alkaline and 3 acid); duration (15, 23, 30 and 60 days). Study specimens include basalts, hyaloclasites and obsidian from Iceland and tuffs from Kamchatka. Each of these four groups of rocks react under hydrothermal influence. The changes observed include sample colours, microstructure, and new mineral phases creation. This changes were especially active in acid solutions. The folowing new minerals were established: 94.2 % smectite, 3.5 % kaolinite, 1.2 % crisrobalite, 1.1 % a mineral which appears similar to diopside; others pores were filled by chlorite. Amorphous silica was established in alkaline solution. The most appreciable changes in measured properties were observed in velocity of longitudinal waves and magnetic susceptibility. It should be noted that for tuffs are observed the same mentiond above changes plus changes in density and porosity. |