TRACKING COMPOSITION OF SEARLES LAKE BRINES AND MINERAL FLUID INCLUSIONS WITH PROGRESSIVE EVAPORATION VIA RAMAN AND LASER INDUCED BREAKDOWN SPECTROSCOPY

Fluid inclusions are micron-scale volumes of fluid incorporated into a mineral upon precipitation from brine solution and are commonly related to the parent composition of the environment from which the mineral formed. The details of how fluid inclusions may represent some past environments are less well understood. In relatively shallow evaporative settings, fluid inclusions can host a variety of microorganisms and can vary in geochemical composition; thus, they have been proposed as targets of interest for life preservation and detection, as evaporite minerals have been detected on Mars. However, processes like meteoric influence, desiccation, rehydration and microbial growth processes (e.g., nutrient cycling, mat formation) may affect the geochemical composition of the fluid inclusions in contrast to the original environment of precipitation. Here, we experimentally evaporate brines of known composition collected from Searles Lake, California and track the brine and fluid inclusion composition to compare to the starting brine. Using Raman spectroscopy and Laser-Induced Breakdown spectroscopy (LIBS), we present a time-series progression on precipitates from fluids collected at various depths from the Searles Lake basin. The dominant mineralogy consists of halite and sulfate salts at shallow depths. Microbial pigments were observed within precipitates at a depth of 81 meters below surface waters. Samples collected at various depths in Searles Lake provide a snapshot of varying aquifer geochemical compositions. Studies of this kind can be applied to potential fluid inclusions found within Martian minerals, offering a unique insight into the geochemical history of the surrounding environment and paleoclimate changes.