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Geochemistry and Petrology

Geochemical assessment of Simav geothermal field, Turkey

Profile image of Umran SerpenUmran Serpen

Revista Mexicana de Ciencias Geológicas

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Abstract

In this study, geochemical methods are used to reliably analyze and understand the Simav geothermal field whose thermal water is rich in terms of Na-HCO3-SO4 and is affected by groundwater which is low in Cl. The water is of meteoric origin and belongs mostly to the immature water group. Quartz and Na-K geothermometers are used to calculate the reservoir temperatures as 70-195 °C and 167-249 °C, respectively, and the Na-K-Mg geothermometer indicated temperatures of approximately 230-240 °C. The isotopic evaluation of the geothermal system indicates that the water in the Simav geothermal reservoir is 18O enriched is fed by cold water from Nadarçam and that the age of the water is older than 50 years. The alteration mineralogy of the field points out to reservoir temperatures between 160 °C and 250 °C in the thermal water. The activity diagrams of the thermal water indicate the existence of fluid-rock interaction and show that the water is in equilibrium with K-feldspar, muscovite, al...

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Arzu fırat ersoy

Geothermal Energy

The Şavşat (Artvin, Turkey) Geothermal Field (ŞGF) is located on the northeastern border of Turkey. This field is characterized by thermal and mineralized springs and travertine. The temperature of the thermal water is 36 °C, whereas that of the mineralized spring in the area is approximately 11 °C. The Na-HCO 3-Cl-type thermal water has a pH value of 6.83 and an EC value of 5731 µS/cm. The aim of this study is to characterize the geothermal system by using geological, geophysical, and hydrogeochemical data and to determine its hydrochemical properties. A conceptual hydrogeological model is developed for the hydrogeological flow system in the ŞGF. According to the hydrogeological conceptual model created by geological, geophysical, and hydrogeochemical studies, the reservoir comprises volcanogenic sandstone and volcanic rocks. The cap rock for the geothermal system is composed of turbiditic deposits consisting of mudstone-siltstone-sandstone alternations. An increase in the geothermal gradient is mainly due to Pleistocene volcanic activity in the field. The isotopic values of thermal water (δ 18 O, δ 2 H, δ 3 H) indicate a deeply circulating meteoric origin. The estimated reservoir temperature calculated by silica geothermometers is 100-150 °C, and the mixing rate of cold groundwater with geothermal waters is approximately 70%. It may be possible to obtain warmer fluids from a 300-m-deep borehole cutting through a fracture zone identified by geophysical studies. Heating by conduction via the geothermal gradient resulting from young volcanic activity drives geothermal waters upwards along faults and fractures that act as hydrothermal pathways. The positive δ 13 C VPDB value (+ 4.31‰) indicates a metamorphic origin for the thermal water. The 34 S CDT value (~ 10‰) shows that the sulfur in the geothermal water is derived from volcanic sulfur (SO 2).

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Hydrogeological, Hydrogeochemical and Isotope Geochemical Faetures of Thermal Waters in Kuşadası, Turkey
ibrahim ibrahim Abubakar

Procedia Earth and Planetary Science, 2017

From Early to Middle Miocene, the continental rift zones of the Büyük Menderes, the Küçük Menderes and the Gediz were formed by extensional tectonic features, which generally strike E-W and are represented by a great number of geothermal waters, epithermal Hg, Sb and Au mineralizations, and volcanic rocks of Middle Miocene to recent age. The geothermal waters and epithermal mineralizations are related to faults, which strike preferentially NW-SE and NE-SW and are located transversely to the general strike of the rift zones. These faults are probably generated by compressional tectonic stress, which leads to the deformation of uplift between two extensional rift zones. One of these continental rift zones is the rıft zone of the Büyük Menderes which is ascribed to a great number of geothermal waters such as those issuing in very important locations of Kızıldere, Tekkehamam, Salavatlı, Germencik and others with a geothermal capacity of 860 MWe in the next future. The geothermal waters of Tekkehamam and surroundings are identified to belong to the Na+K>Ca>Na and HCO 3 >SO 4 >CI facies. According to the Cl-SO 4-HCO 3 diagram the geothermal waters might be heated by a magmatic source due to the high content of sulfate and boron in geothermal waters. Geochemical thermometers were applied to the collected samples in the region. According to the Na-K-Mg diagram (1), part of the geothermal waters can be considered as equilibrated geothermal waters. According to the results of geochemical thermometers, the reservoir temperatures of geothermal waters range from 160 to 250°C. The δ 2 H values of geothermal waters are between-61.9 to-51.8, while δ 18 O values range from-9.23 to-5.84. The tritium contents of geothermal waters are between 0.7 to 3.3 TU. These results show that there is no mixing with cold groundwaters.

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Related topics

  • Geology
  • Geochemistry
  • Mineralogy
  • geothermal gradient
  • Geothermal Fluids
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