  An analytical expression is derived for the thermal response observed during
spontaneous imbibition of water into a dry core of zeolitic tuff. Sample
tortuosity, thermal conductivity, and thermal source strength are estimated
from fitting an analytical solution to temperature observations during a single
laboratory test. The closed-form analytical solution is derived using Green's
functions for heat conduction in the limit of "slow" water movement; that is,
when advection of thermal energy with the wetting front is negligible. The
solution has four free fitting parameters and is efficient for parameter
estimation. Laboratory imbibition data used to constrain the model include a
time series of the mass of water imbibed, visual location of the wetting front
through time, and temperature time series at six locations. The thermal front
reached the end of the core hours before the visible wetting front. Thus, the
predominant form of heating during imbibition in this zeolitic tuff is due to
vapor adsorption in dry zeolitic rock ahead of the wetting front. The
separation of the wetting front and thermal front in this zeolitic tuff is
significant, compared to wetting front behavior of most materials reported in
the literature. This work is the first interpretation of a thermal imbibition
response to estimate transport (tortuosity) and thermal properties (including
thermal conductivity) from a single laboratory test.
