A series of column transport experiments ranging from 25 degrees C to 275 degrees C, as well as batch sorption experiments at 25 degrees C, were conducted to estimate cation exchange parameters for lithium and cesium at the Newberry Crater Enhanced Geothermal System demonstration site. The experiments were designed to facilitate interpretation of single-well field tracer tests to interrogate fracture surface area. Lithium column transport from 125 degrees C to 275 degrees C showed a strong temperature dependence, with much greater cation exchange at higher temperatures than in 25 degrees C experiments. Cesium column transport at 225 degrees C indicated a weaker temperature dependence, and unlike Li+, its exchange decreased at higher temperatures. Published by Elsevier Ltd.