Geochemical Interpretation of Thermal Water and Gas Samples from Krisuvik, Iceland and Alid, Eritrea

Abstract

Alid, Eritrea is one of the geothermal fields located within plate tectonic rift zones; an environment characterized by high heat-flow. In this paper, geochemical data of the system is reviewed and interpreted. The objective of this study is to explore the potential of geochemical methods to predict the reservoir temperatures and evaluate equilibrium conditions for the Alid fields.

The Alid water samples are characterized by low pH and high sulphate content, typical of steam heated surface waters. As a result, solute geothermometers do not represent temperatures of the geothermal reservoir. This is reflected by low quartz geothermometer temperatures (80-224ºC) compared to the gas-thermometer temperatures that range between 163 and 364°C with an average of 272ºC. The results indicate that the geothermal reservoir at Alid is vapour-dominated and surface thermal waters are derived from shallow, steam heated ground water reservoirs