Pinpointing Deep Geothermal Upflow in Zones of Complex Tectono-volcanic Degassing: New Insights from Aluto Volcano, Main Ethiopian Rift

Abstract

Active rifts release large amounts of volcanic gases from deep sources to the atmosphere. The objective of this paper is to present a geothermal exploration strategy for areas, which have limited hydrothermal surface expressions and are unsuitable for fluid sampling and analyses. In such areas soil gas surveys can complement established exploration strategies. We report CO2, 222Rn and 220Rn emissions from the Aluto volcanic complex (Ethiopia) to improve our understanding of tectonic and volcanic controls on the existing geothermal system. Results will help to optimize the understanding of geothermal systems and to identify major, deep-reaching permeable structures with active fluid circulation, suitable as drilling targets for geothermal production wells. Significant differences in gas signatures have been used to identify predominantly volcanically and/or tectonically influenced compartments. Major gas emissions have been observed in areas jointly affected by tectonic structures and volcanic driving forces (tectono-volcanic) indicating significant fluid circulation at depth. Predominantly fault-controlled sectors also show hydrothermal fluid circulation, but to a lower extent compared to tectono-volcanic sectors. Within the Aluto volcanic complex geothermal production wells mainly target such fault-controlled domains, whereas results of the study indicate strongest fluid circulation in tectono-volcanic sectors. This result should be considered for the future exploration and development strategy of the site. This paper is a brief summary of the following publication: Pinpointing Deep Geothermal Upflow in Zones of Complex Tectono‐Volcanic Degassing: New Insights from Aluto Volcano, Main Ethiopian Rift (Jolie et al., 2019).