Reconnaissance of a Low-Temperature Geothermal Resource, Tenakee Inlet, Alaska

Abstract

A reconnaissance study of the Tenakee Inlet geothermal resource was conducted in order to evaluate its nature and determine if there is potential for power generation. The resource is in a remote, rugged area of southeastern Alaska, accessible via helicopter. A prior hot spring temperature measurement was 176 °F. Tenakee Creek is located to the immediate northeast of the hot springs. The Queen Charlotte Fairweather fault system lies to the west of the resource and is part of a transform plate boundary with associated earthquakes and linements aligned north to south. Fieldwork consisted of a shallow soil temperature survey and collection of soil, water, and rock samples. The shallow soil temperature survey indicated a broader thermal area than just around the hot springs and includes portions across Tenakee Creek. Soil samples had chemical species that were anomalous near the hot springs as well as across the creek in the same areas as the higher temperature readings. Water samples from the hot springs indicated fluids low in chlorine and bicarbonate but high in sulfate. The hot springs waters are most likely associated with volcanic waters and perhaps heated by steam from a deeper reservoir. Surface temperatures of the hot springs ranged from 161 to 177°F over the course of the 15-day long field effort. Based on the chalcedony geothermometry the hot springs fluids may have been heated to 260°F. The surface and subsurface temperatures are in the range appropriate for a binary geothermal power plant.