If basaltic magmas provide half the CO2 degassed at
Yellowstone (the rest coming from carbonate rocks), associated
intrusion, cooling, crystallization, and/or large-scale
convection could provide much of the observed heat flow.
Parental basalts from Kilauea (Hawai‘i) are estimated to
have 0.7 wt% CO2 (Gerlach et al. 2002); more-fertile mantle,
as would be expected beneath Yellowstone, would be more
CO2 rich (Thordarson and Self 1996; Dixon et al. 1997;
Lowenstern 2001). Assuming 1 wt% CO2 in mantle-derived
basalt, an intrusion rate of 0.3 km3 y-1 would be required to
produce the observed gas flux. An intrusion rate of 0.3 km3
y-1 is comparable to, though slightly higher than, those estimated
for Kilauea and the Columbia River Basalt (Gerlach
et al. 2002; Lange 2002). This intrusion rate would create a
power output of 22 GW (assuming full crystallization and
further cooling of 300°C), about 3 times the minimum
observed heat flow (Fournier 1989). Less heat might be
expected if the intruding basalt loses heat laterally, or if it
degasses during ascent with minimal cooling and crystallization.