| Abstract |
Al-Qafr geothermal field is one of Yemen’s significant fields, so it is important to carry out geological and surface hydrothermal alteration mapping for this geothermal field. The main manifestations mapped include thermal spring, some of them associated with gas discharge, boiling pool and hot wells as well as travertine deposits along with slight hydrothermal alteration. Geology of the area is mainly composed of Tertiary basalts, Cretaceous sandstone (Tawilah Group), with small outcrops of sandy limestone and Quaternary deposits of travertine, pediment deposit and alluvium with several acidic, basic and silicified dykes. Structural features are represented by several extensional faults and fracture system striking NW-SE, almost parallel with the main Red Sea trend. The main goal of this study is to conduct mapping of the geothermal manifestations in order to find out probable correlation existing between geothermal, volcanic, hydrothermal as well as tectonic setting and structural patterns in this field. The surface alteration and manifestations are found to be of linear distribution trending in the same direction as the major fault system (NW-SE). Hot spring surface temperatures (75-97 °C) are measured at Al-Qafr area, along with precipitation of SiO2 on the surface as indicated by geothermometric analysis of these thermal waters. The geothermal map illustrates the distribution of the alterations, which are concentrated in the central part of the study area at the vicinity of the hot springs, indicating that the center of geothermal activity extends from northwest to the southeast of the study area. Different hydrothermal alteration products, including quartz, calcite, zeolite, albite and clay mineralization are indicated by XRD analysis. |