Известия Томского политехнического университета: Инжиниринг георесурсов (May 2019)
Interaction of natural and technogeneous brines of Verkhnekamskoe salt deposit with basic minerals of salt strata
Abstract
The relevance of the discussed issue is caused by the need to increase the reliability of identification of "accidental" suprasalt brines in mines of the Verkhnekamskoe salt deposit. The main aim of the study is to investigate the equilibrium of suprasalt and mine brines of the Verkhnekamskoe salt deposit with basic chloride (halite, sylvine, carnallite) and sulfate minerals (gypsum, anhydrite). The methods used in the study. The saturation of brines relative to minerals of the salt strata were calculated based on physico-chemical modeling for normal atmospheric pressure and at solution temperature of 10 °C. The saturation index (SI) was used for characterizing the degree of saturation with respect to minerals. Taking into account the high salinity of brines the model of K. S. Pitzer was applied when calculating the activity coefficients. Geochemical modeling code PHREEQC (prepared by David Parkhurst and Tony Appelo) was used as the main calculation module. The results of the study have shown that the mine brines of the deposit of both natural (postsedimentation) and technogeneous (condensation, hydraulic stowing) genesis is in equilibrium or as close to equilibrium as possible with halite (mean SI=0,00; Std. Dev 0,09) and sylvine (mean SI=0,00; Std. Dev. 0,16) based on data of 324 samples obtained in 2011-2014. Depending on genesis and chemical composition the brines are saturated in varying degree with carnallite (mean SI= -2,00; Std. Dev.1,08). The brines are in equilibrium with gypsum and slightly undersaturated with anhydrite. Suprasalt high salinity brines distributed in the bottom of the salt-marl strata and related to leaching of overlying rock salt, due to their Cl-Na composition, are in equilibrium or near to equilibrium with halite but undersaturated with respect to sylvine.
