GEOCHEMICAL EVOLUTION AND ERUPTION DYNAMICS IN CRYSTAL GEYSER - GREEN RIVER, UTAH

Climate change due to anthropogenic carbon dioxide emissions is a growing concern within the scientific community. Geologic storage of carbon dioxide (CO₂) continues to garner interest yet there are concerns about its efficacy. Abandoned wells are found throughout areas proposed to store CO₂ and hence would serve as potential leakage pathways. Crystal Geyser in Utah, a CO₂ driven cold water geyser, is one such abandoned well and serves as a natural analogue for a geologically stored CO₂ leak. Understanding the driving forces for Crystal Geyser will prove beneficial in developing knowledge about how a failed geologic CO₂storage site works.

In situ changes of pressure, temperature, pH, dissolved oxygen and electrical conductivity were monitored at depths of 6 m and 14 m during August, September and December of 2010. Additionally, 22 water samples emitted from the geyser were collected at various times during an eruption cycle in December of 2010. From various measurements the comprehensive periodicity of the geyser and its temporal chemical evolution were determined.

A single eruption cycle is roughly 40 hours long and consists of 6 intervals. There are two minor eruption periods (Type A and C), two major eruption periods (Type B and D) and two recharge periods which follow the major eruptions. The major eruptions can be broken into five intervals based upon their trends in pressure and temperature. Evolution of brine chemistry during the eruptions supports the hypothesis that mixing of Navajo Sandstone deep brines with fresh groundwater from shallow aquifers occurs. The pH is predominately constant at 6.55, but distinctively drops during CO₂eruptions coupled with the reduction of dissolved oxygen content. The geochemical speciation shows that the water in Crystal Geyser is supersaturated with respect to aragonite,calcite, dolomite, hydrated iron oxide, hematite, strontianite, goethite as well as various forms of jarosite and ferrite. Finally, we also sampled naturally occurring spring and geyser to the south near the Salt Wash fault and identified spatial hydrogeochemical trends.