Raman microscopy of inclusions in blue halites

This paper presents preliminary results of the investigation of fluid inclusions in blue halite from the Kłodawa salt mine (Central Poland). According to earlier studies, blue halite occurs relatively frequently in almost all of the mining levels in this salt diapir. Various types of blue halite inclusions, generally of epigenetic genesis, were identified under a transmitted light polarizing microscope. Their size, shape and position in relation to crystallographic axes suggest the presence of diverse generations of inclusions. Micro-Raman spectra were measured for both natural halite (colourless and blue) and artificial halite crystals. Colourless part presents dominant in the spectrum, asymmetric 335 cm−1 band consisting of NaCl vibrations as well as vibrations of other alkali halogens, particularly of KCl and KBr. Generally, the same band was obtained for the artificially crystallized NaCl. The band at 199 cm−1 is attributed to the presence of KCl in natural blue halite. Raman depth profiles were collected to study the size and contents of inclusions in several selected blue halite samples. The dominant component seems to be a mixture of various hydrocarbons and CO2. The liquid in inclusions may sometimes contain large amounts of SO42− and CO32− ions. There were also inclusions recognized with organic matter (bands at 1240, 1407 cm−1 and in the 3600–3000 cm−1 region).