Pamukkale Univ Muh Bilim Derg. Ahead of Print: PAJES-48979 | DOI: 10.5505/pajes.2024.48979

Hydrogeochemistry and hydrothermal alteration of the Hanle geothermal field, Djibouti-East Africa

Ali Ferat Bayram¹, Moussa Hassanleh Hassan^2
1Konya Technical University, Faculty of Engineering and Natural Sciences, Deparment of Geological Engineering
²Konya Technical University, Graduate Education Institute, Geological Engineering Program

This study focuses on the geochemistry and hydrothermal alteration of the Hanle geothermal field (Djibouti-East Africa). Water from five drinking water wells, a hot spring and a steam condensate in the Hanle graben was analyzed for major and minor hydrogeochemical parameters. Analyzed items for water samples (hot spring water, groundwater, and steam condensate) are PH, electric conductivity (EC)SiO2, Cl, SO4, HCO3, F, Na, K, Ca, Mg, Al, Fe, B, As, δD, δ18O. Using the chemical compositions of the hot springs and the Phreeqc, the reservoir temperature was estimated at around 120 to 125°C. Based on the XRD analysis, the clay minerals smectite, chlorite and illite, as well as quartz, calcite, and alunite, were determined as alteration minerals in this region, which represent high temperature environment (>180°C). The obtained data suggest that the water in the Hanle region was likely formed either by the mixing of groundwater and heated fossil seawater, or by the dissolution of evaporite by heated groundwater.

Keywords: hydrothermal alteration, Hanle, Djibouti, Geochemistry

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Hanle jeotermal alanýnýn hidrojeokimyasý ve hidrotermal alterasyonu, Cibuti-Doðu Afrika

Ali Ferat Bayram¹, Moussa Hassanleh Hassan^2
1Konya Teknik Üniversitesi, Mühendislik ve Doða Bilimleri Fakültesi, Jeoloji Mühendisliði Bölümü
²Konya Teknik Üniversitesi, Lisansüstü Eðitim Enstitüsü, Jeoloji Mühendisliði Ana Bilim Dalý

Bu çalýþmada, Hanle Jeotermal Alanýnýn (Cibuti-Doðu Afrika) jeokimyasý ve hidrotermal alterasyonuna dayalý olarak alanýn jeotermal potansiyelinin araþtýrýlmasý amaçlanmýþtýr. Hanle grabenindeki beþ içme suyu kuyusundan, bir kaplýcadan ve bir buhar yoðuþmasýndan alýnan sulardan hidrojeokimyasal analizler yapýlmýþtýr (PH, elektrik iletkenliði (EC)，SiO2, Cl, SO4, HCO3, F, Na, K, Ca, Mg, Al, Fe, B, As, δD, δ18O). Bu sularýn doygunluklarý ve çeþitli jeotermometreler kullanýlarak, rezervuar sýcaklýðýnýn yaklaþýk 120- 125°C olduðu tahmin edilmiþtir. XRD çözümlemelerinde yüksek sýcaklýk ortamýný (>180°C) temsil eden smektit, klorit ve illit türü kil mineralleri ile kuvars, kalsit ve alunit gibi alterasyon mineralleri belirlenmiþtir. Elde edilen veriler, Hanle bölgesindeki suyun ya yeraltý suyu ve ýsýtýlmýþ fosil deniz suyunun karýþmasýyla ya da ýsýtýlmýþ yeraltý suyunun evaporiti çözmesiyle oluþmuþ olabileceðini göstermektedir.

Anahtar Kelimeler: hidrotermal alterasyon, Hanle, Cibuti, Jeokimya

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