Thermometrical studies of fluid inclusions in the Badenian halite of the Carpathian region in the context of determining the depth of the salt basin

Abstract

It was established that in order to avoid errors in the interpretation of paleotectonic conditions of salt formation based on fluid inclusions in halite, the primary stage of the research should be the genetic identification of the sedimentation textures of halite and fluid inclusions in this mineral. For the thermometric study of inclusions and to determine the depth of the sedimentation basin based on the obtained data, only thermal test chambers are suitable which provide the possibility of observing groups of inclusions in different zones of sedimentary halite, as, for example, in the micro thermal test chamber designed by Prof. V. A. Kalyuzhny. In the course of the research, the equipment of the thermometric method, which is based on the use of a microthermal test chamber designed by V. A. Kalyuzhny, was modernized. In particular, the material of the thermal chamber (stainless steel) was replaced with copper, which made it possible to avoid excessive thermal gradients into chamber and to increase the permissible heating rate by 20 times due to the higher thermal conductivity of copper. For the same purpose, the glass optical windows of the camera were replaced with leukosapphire windows, which have a much higher thermal conductivity. The measuring system of the installation is made on a miniature platinum resistance thermometer with an electronic measuring unit. These improvements made it possible to achieve high system stability and good reproducibility of measurement results. Using the thermometric method, it was established that the temperature of sedimentation at the bottom of the Badenian salt basin of the Carpathian region was 19.5–20.5; 20.0–22.0; 24.0–26.0 °C, and on the surface of the brine was 34.0–36.0 °C. On this basis, a model of the basin with a pronounced thermocline and a total thickness of the water column of up to 30 meters was built, which is the most likely to establish the features of sedimentation. Crystallization of halite at different depths in basins with a thermocline can explain the presence of so-called “low-temperature” (24.0–25.0 °C) and “high-temperature” (37.8–42.6 °C) bottom halite in a number of ancient salt-bearing basins.