Geochemical Data and Fluid Inclusion Study of the Middle Miocene Halite from Deep Borehole Huwniki-1, Situated in the Inner Zone of the Carpathian Foredeep in Poland

Abstract

The geochemical data and the study of fluid inclusions in primary halite are invaluable sources of saline basin information. Most of the previous analyses of salt from the Carpathian area have been obtained by studying the halite samples collected from depths not exceeding 1000 m (i.e., from salt mine outcrops or boreholes). In this article, for the first time, we present the results of samples obtained from a deep well where salt occurs below the frontal orogenic wedge at a depth of ~5000 m. The salt core’s petrological studies showed, quite unexpectedly, the presence of the chevron relics, typical for primary halite. Their geochemical data and fluid inclusion study can be used to reconstruct the environment of the salt sedimentation. The bromine, strontium, and rubidium content values indicated that primary brines were of marine origin, and salts may have undergone partial dissolution and redeposition under lower salinity water inflows. The main ions’ (K, Mg, SO4) ratios in the fluid inclusions were typical for those of the Badenian brines collected from the Carpathian Foredeep’s eastern part. Compared with modern seawater’s chemical composition, this brine contained a slightly lower content of sulfate ions. This was associated with evolutionary changes occurring in the contents of sulfate ions during the Cenozoic.