| Abstract |
The Makushin geothermal system consists of a magmatic heat source, a deep boiling hot water reservoir and a shallow, discontinuous vapor dominated zone that discharges steam and gases at elevations above 360 m. Numerous low C1, HCO3 So4 rich thermal springs emanate down slope from fumaroles found in exposed portion of the host reservoir rock, the Makushin diorite pluton. Thermodynamic consideration of a 152°C superheated fumarole indicated steam separates form the main reservoir at temperatures of >185°C. Gas geothermometry gives reservoir temperatures ranging from 230°C to 297°C. Alkali C1, HCO3, SO 4 rich thermal spring waters in lower Glacier Valley appear to be mainly derived form subsurface down valley flow of HCO3, SO4 thermal waters from the flanks of HCO3 SO4 thermal waters from the flanks of the Makushin Volcano. The C1 may originate from seawater contaimination or from mixing of C1 waters from a deep reservoir. Halite deposits at the head of Glacier Valley suggest the underlying C1 rick hot water reservoir has recently become self sealed or has undergone rapid depletion of water. |