| Title | Geochemical and Isotopic Study of North Lake Abaya Geothermal Prospect |
|---|---|
| Authors | Asfaw Teclu |
| Year | 2008 |
| Conference | ARGeo |
| Keywords | Ethiopia Rift Valley, thermal manifestations, stable isotopes, water chemistry. |
| Abstract | Abaya geothermal prospect is one of the geothermal fields in Ethiopia that was recommended for further study by the UNDP (1973). It is located about 500 km south of Addis Ababa in the southern part of the Lakes District, Main Ethiopian Rift. It is named after the Abaya Lake which is 6o 15N 37o 55E that occupies a tectonic depression in the Rift floor, because most of the thermal springs are located around the lake shore. Twenty water samples that include thermal springs, cold springs, a lake and rivers were collected in the area of study of which most are near neutral to slightly alkaline in pH. According to the Langelier Ludwig diagram the water chemistry suggests the existence of NaCl-HCO3 and NaHCO3 water types. The reservoir temperature as shown in the Giggenbach ternary diagram indicated an equilibrium temperature of 250oC and 180oC for Wache and Bolocho hot springs respectively. Furthermore the ternary diagram has indicated that Wache and Bolocho are in the quasi equilibrium zone. Soluble constituents in association with Cl may be used to determine whether the system contains one or several aquifers, therefore from the Cl versus B, Cl versus Na and Cl versus SO4 plot it was possible to observe the existence of two types of aquifers. The ä2H versus ä18O plot has revealed “18O-shift’ of 1.5‰ for Wache spring which might indicate higher circulation period and longer residence time. Others are shown to cluster in the GMWL (Global Meteoric Water Line) showing that they are meteoric in origin which implies that they are recently involved in the hydrologic circulation. |