Geothermal potential and origin of natural thermal fluids in the northern Lake Abaya area, Main Ethiopian Rift, East Africa

被引：24

作者：

Minissale, A. ^{[1
]}

Corti, G. ^{[1
]}

Tassi, F. ^{[1
,2
]}

Darrah, T. H. ^{[3
]}

Vaselli, O. ^{[1
,2
]}

Montanari, D. ^{[1
]}

Montegrossi, G.

Yirgu, G. ^{[4
]}

Selmo, E. ^{[5
]}

Teclu, A. ^{[6
]}

机构：

[1] CNR Italian Council Res, IGG Inst Geosci & Earth Resources, Via La Pira 4, I-50121 Florence, Italy

[2] Univ Florence, Dept Earth Sci, Via La Pira 4, I-50121 Florence, Italy

[3] Ohio State Univ, Sch Earth Sci, 275 Mendenhall Lab,125 South Oval Mall, Columbus, OH 43210 USA

[4] Addis Ababa Univ, Sch Earth Sci, Fac Sci, POB 1176, Addis Ababa, Ethiopia

[5] Dept Phys & Earth Sci, Parco Area Sci 7-A, I-43124 Parma, Italy

[6] Geol Survey Ethiopia, Hydrogeol Engn Geol & Geothermal Dept, POB 40069, Addis Ababa, Ethiopia

来源：

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH | 2017年 / 336卷

关键词：

Lake Abaya; Ethiopian Rift; Geothermal potential; Fluid chemistry; NOBLE-GAS; FIELD; WATER; GEOCHEMISTRY; EQUILIBRIA; DISCHARGES; REDUCTION; CHEMISTRY; VALLEY; CO2;

D O I：

10.1016/j.jvolgeores.2017.01.012

中图分类号：

P [天文学、地球科学];

学科分类号：

07 ;

摘要：

In this study, the occurrence, chemical composition, origin and geothermal significance of thermal springs and fumaroles naturally discharging in the area located north of the Lake Abaya (western margin of the Main Ethiopian Rift, East Africa) are reviewed in relation with recent tectonics. All thermal springs showed a dominantly Na-HCO3 composition, consistent with observations dating from at least 1972, and most of them displayed a narrow range of delta D and delta O-18 isotopic compositions for water similar to regional meteoric origins. These observations suggest that water-rock interaction processes occur in all aquifers and dominate the contributions of water that actively circulate within thermal fluids, and also suggest a similar elevation of groundwater recharge throughout the study area. Most of the thermal springs are dominated by a CO2-rich gas phase and discharge along the active faults bordering the western edge of the Main Ethiopian Rift valley. The delta C-13 values of CO2 and the (3)Fle/He-4 isotopic ratios are consistent with the presence of mantle-derived fluids similar to what is observed in many other areas along the kinematically active African Rift, especially within Ethiopia. The application of geothermometric techniques in the liquid and the gas phases suggests the presence of a deep reservoir in which the fluids equilibrated at a maximum temperature of approximately 180 degrees C. Additionally, the presence of fumaroles at boiling temperatures and water/mud boiling pools in several places suggests that the geothermal reservoir is positioned at a relatively shallow depth and likely located in the western side of the study area. The analysis of data collected throughout time reveals that the waters of Lake Abaya have experienced an increase in salinity of 20% paralleled contemporaneously with a decrease in pH and delta O-18 and delta D of water in the last 40 years; these changes do not appear to be related to climate change-induced increases in temperature or evaporation at the global scale. (C) 2017 Elsevier B.V. All rights reserved.

引用

页码：1 / 18

页数：18