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Examples of Geological and Geothermal Mapping In Iceland and In Yemen
The first geothermal area ( Djúpavatn-Vigdísarvellir area ) is located about 30 km south of Reykjavík. Geological and Geothermal mapping was carried out in the Djúpavatn–Vigdísarvellir area which is a part of the Krýsuvík-Trölladyngja geothermal area on the Reykjanes Peninsula, SW-Iceland. The bedrock consists mainly of Late Pleistocene hyaloclastites and interglacial lava flows and Holocene lavas. They are divided into 11 hyaloclastite units and 3 interglacial lava flows. The geological age of the volcanic field extends from Holocene, through the last glaciation, the last interglacial period, the 2nd last glaciation, the 2nd last interglacial period, the 3rd last glaciation, and the 3rd last interglacial period. The oldest bedrock units outcrop in the northeast part of the study area and are from the third last interglacial period and third last glaciation, while Holocene lava flows occur in the northwest and east sides of the study area. The Krýsuvík-Trölladyngja area has two main hyaloclastite ridges, with the valley between covered by Holocene lava flows. Two tephra layers were found in the soil section on top of the youngest lava, the earlier from Reykjanes AD 1226 and the latter from the Katla volcano dated from 1485. The tectonics of the study area is controlled by the regional tectonics of the Reykjanes Peninsula. The main structural features are NE-SW trending hyaloclastite ridges. Numerous NE-SW trending normal faults were mapped in the study area. The main geothermal manifestations occur in the southern part of the study area. The alteration ranges from slight alteration to intense and indicates relatively young geothermal activity, but all of it is extinct on surface within the study area. The second geothermal area (Al Lisi–Isbil Geothermal field) is located about (100) km from Sana’a capital city of Republic of Yemen, The geothermal mapping was carried out in (Al Lisi and Isbil ) in the western area of Yemen. The rocks type in Al Lisi–Isbil Geothermal area was classified To six group, trap series, the post trappic volcanic activity, Isbil volcanic complex, Al Lisi volcanic complex, Basaltic Fissure volcanism and recent and active sedimentary deposits, The main structural feature are trend (NNE-SSW),(NE-SW). The main structural feature are trend (NE-SW). In Al Lisi and Isbil Geothermal area. The Geothermal manifestations (steam, clay alteration and slight alteration) common in many deferent site in the Geothermal area, two types of alteration zones are distinguished slight alteration mostly characterized by slight color change of the Brownish, reddish, yellowish to white colors and also involving some silica minerals (opal) and calcite veins and the some altered rocks assume a whitish color due to the presence of opline silica, clay minerals and iron oxides. In addition, the Albit, Montomornillonite, Biotite, Kaolinite, Chlorite Quartz, and Calcite are the individual minerals obtained by analysis (X- Ray) for samples taken from Al Lisi and Isbil Geothermal area. The temperatures of steam that exceed 92ºC and They are 118 hot well in the area the temperature between (25ºC) to (59ºC).