Gypsum Past studies have determined that the gypsum occurring in Bristol Lake precipitated displacively within the sediment where groundwater saturated with gypsum recharges around the mud lithofacies. This is supported by the geometry of the deposit and by chemical data, which suggests that water precipitating gypsum in the playa is more associated with groundwater than the brine at the basin center. microorganisms have the potential to rework large lenticular crystals, high concentrations of
NaCl in inflow waters can decrease nucleation density of minerals resulting in larger crystal sizes. It is likely that a combination of these processes was needed in order to form the gypsum crystals mentioned because gypsum crystals formed from low Ca/SO4 ratios or from microbial activity alone would not result in gypsum crystals large enough, and because gypsum crystal size increases toward the center of the playa where sodium chloride concentrations are greatest.
Possible magma chamber The brine chemistries at Bristol Lake are different from those predicted to form by the evaporative concentrations of the two inflow waters currently accounted for. • Na-HCO3-SO4 will precipitate CaCO3 which will deplete the water in calcium. These waters evolve into Na-HCO3-CO3-Cl-SO4 brines with minor magnesium and potassium. They will precipitate halite, Na-Sulfate, and Na-carbonate mineral upon further evaporation. • Cl-SO4 is predicted to precipitate calcite and then gypsum and form neutral Na-SO4-Cl brines with subordinate K and Mg. These brines are predicted to precipitate halite and sodium-sulfate salts during further evaporative concentration. The basin center brines of BDL (saline mudflats and saline pan areas) are Na-Ca-Cl rich with lower concentrations of potassium and magnesium and little sulfate and
bicarbonate. Differing from their predicted chemical composition mostly by lacking sulfate, carbonate and bicarbonate and having high levels of chlorine. Rosen 1991 attributed increased concentration of chlorine to be from atmospheric precipitation, however the Ca-Cl concentrations present at Bristol Lake are not compatible with normal low temperature surface weathering and evaporative concentration processes. It is speculated that a magma chamber drives the formation of Ca-Cl brines at elevated temperatures and drives the transportation of these brines to the surface. Other evidence of a magma chamber in the area is the
Amboy Crater and its associated lava flows, which occur directly North of Bristol Lake. ==Industry==