CHARACTERIZATION OF ABIOGENIC VS. BIOGENIC CARBONATE PRECIPITATION IN SIMULATED MODERN GREAT SALT LAKE CONDITIONS

The Great Salt Lake in northern Utah, remnant of the Pleistocene Lake Bonneville, is characterized by hypersaline conditions and abundant evaporate accumulation. The lake is also renowned for being a “carbonate factory”. However, in part due to its high salinity, the carbonate system of the Great Salt Lake is not well characterized. Carbonate precipitation is controlled by numerous factors such as pH, temperature, degassing, pressure, biological factors, and solute concentration. In this study, laboratory precipitation experiments were conducted in controlled conditions to determine the conditions under which carbonates precipitate abiogenically. Carbonates were forced to precipitate by varying conditions to favor carbonate production, including degassing by constant bubbling, and the addition of NaOH, NaHCO₃ and CaCl₂. Mineralogy was confirmed using scanning electron microscopy with energy-dispersive x-ray analysis (SEM-EDX). Cultures of microorganisms with different metabolic pathways were then introduced in an attempt to generate biogenic carbonate. The latter experiments are ongoing; so far, no biogenic carbonate has precipitated. Results of this study will be used to interpret shoreline carbonate deposits at Great Salt Lake.