Alteration Mineralogy and Fluid Inclusion Microthermometry of the Hes-Daba Area in Gagade, Republic of Djibouti

Abstract

This study focuses on fluid inclusions from the Hes-Daba area. Microthermometric measurements were conducted on quartz collected from surface veins that hosted inclusions in two phases: liquid and vapor. The mean homogenization temperature ranged from 150 °C to 367 °C and the melting point of ice ranged from −0.05 °C to −1.14 °C, indicating that the inclusion solutions consisted of 0.1 to 1.9 eq. wt% NaCl. The thermal history and thermal structure were evaluated to estimate the formation temperature. Selected samples were analyzed via x-ray diffraction to provide direct data on geothermal reservoirs; this was necessary because geothermal fluids, through their interactions, can alter the composition and properties of rocks. The main alteration minerals were quartz, calcite, alunite, epidote, hematite, illite, smectite, and chlorite. Therefore, the clay constituted a transition to a hightemperature environment, as evidenced by high temperature hydrothermal alteration minerals such as quartz (>180 °C) and epidote (~250 °C). © 2025, Murat Yakar. All rights reserved.