Preliminary geochemical prospecting of thermal sources was carried out. Twenty-three samples, taken from around the lake were analyzed. Values range from 1.1 to 169 ppb, with 50 ppb average. Thus, the Lake Vanda area with rather high mercury content would suggest the existence of a thermal source under the ground, strongly supporting the occurrence of some hydrothermal minerals around the lake. It is, however, still uncertain whether the heat supply has continued up to date or not. In order to gain further information on geothermal sources around Lake Vanda, more detailed mercury survey would be required.