EFFECT OF EXPOSURE AND DESICCATION ON MINERALIZATION OF GREAT SALT LAKE MICROBIALITES

To investigate how exposure and desiccation influences mineral formation in Great Salt Lake, UT, a lab experiment was set up which replicated various aquatic conditions observed in the field. Samples taken from Buffalo Point, Antelope Island (Davis County) were placed in aquaria mimicking submerged, open-system evaporation, and closed-system evaporation conditions, and subsampled weekly. Subsamples were assessed for mineral production using scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDS), confocal laser scanning microscopy (CLSM), x-ray diffraction (XRD), and petrographic analysis using thin sections. EDS and XRD results found evidence of replacement of poorly formed Mg-Si crystal formation with aragonite, as initially proposed by Pace et al (2016), based on the degradation of organic matter. This was indicated by positive correlations between Mg and Si concentrations in submerged vs. open-system evaporation conditions, a negative correlation of Si to Ca, and a positive ID of aragonite using XRD techniques. CLSM imagery revealed close spatial associations between carbonate minerals and EPS, similar to the model for thrombolytic mineralization described by Pace et al (2016) and Dunham et al (2020). The system of mineralization changes as the system is exposed to rapid desiccation, with evidence for preservation of a Mg-Si phase lacking. It appears that the mode of evaporation influences mineral production with gradual evaporation maintaining the Pace et al model while rapid desiccation samples failed to demonstrate the replacement of minerals central to that model. A critical difference between this experiment and the previous publications was the complete lack of identified dolomite in any samples.