Effects of glacial ice on subsurface temperatures of hydrothermal systems in Yellowstone National Park, Wyoming: Fluid-inclusion evidence

Geochemistry and Dynamics of the Yellowstone National Park Hydrothermal System

“…Also, because the presence of glacial ice seems to be required to explain elevated boiling point curves, it can be concluded that hydrothermal activity beneath the major geyser basins has been continuous since sometime within or before the last glaciation, a minimum of 14,000-45,000 yr. The fluorite and much of the hydrothermal quartz used in the Bargar & Fournier (1988) study were deposited relatively late in the sequence of hydrothermal events, after most of the surrounding rock had already been thoroughly altered by hydrothermal activity, but before the last glacial ice decreased in thickness to less than 450-750 m. The data are consistent with a model in which hydrothermal activity within the 0.6-Ma Yellowstone caldera started soon after the formation of that structure and continued unabated thereafter, with significant variations in intensity and places of discharge in response to pulses of volcanism and the waxing and waning of glacial episodes.…”

“…Muffler et al (1971) postulated that boiling-point curves and rock temperatures were raised within the upper parts of some hot spring systems at Yellowstone during times of glacial cover, and that sudden decreases in the water table (as by draining of an ice-dammed lake) resulted in major hydrothermal explosive activity. Primary and secondary fl uid inclusions in material from several cored holes in Yellowstone National Park (White et a1 1975) have been studied by Bargar & Fournier (1988) to quantify thermal effects that may have accompanied a raising of the water table and the corresponding boiling-point curve during times of thick glacial ice cover. The results from two holes (Y-6 and Y-13) have been reported as parts of other investigations (Bargar & Beeson 1984, Bargar et al 1985.…”

Dynamics of the Yellowstone hydrothermal system

“…Whereas enhanced hydrothermal activity and explosions were associated with glacial retreat [ Bargar and Fournier , ] and likely occurred over centuries and millennia, the extreme seasonal variations and large volumes of snow melt and ice thaw in May and June result in significant modulation of hydrothermal activity [ Hurwitz et al ., , , ]. Statistical analysis of a 20 year seismic data set (1984–2003) revealed that earthquake occurrence in the shallow crust beneath Yellowstone Lake is correlated with the annual lake level cycles, with peak seismicity between September and October [ Christiansen et al ., ].…”

Geologic field-trip guide to the volcanic and hydrothermal landscape of the Yellowstone Plateau

“…Temperatures were elevated relative to current conditions because the boiling temperature is much higher at pressures found beneath thousands of feet of glacial ice. Fluid inclusions in minerals sampled from geothermal drill holes confirm that downhole temperatures in many geothermal reservoirs at Yellowstone were 10 to 50 °C higher during glacial periods (Bargar and Fournier, 1988).…”