Hydrogeochemistry of geothermal waters in eastern Turkey: Geochemical and isotopic constraints on water-rock interaction

AYDIN H., Karakuş H., Mutlu H.

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, cilt.390, 2020 (SCI-Expanded) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 390
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1016/j.jvolgeores.2019.106708
  • Dergi Adı: JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, PASCAL, Aerospace Database, Aquatic Science & Fisheries Abstracts (ASFA), Artic & Antarctic Regions, Chemical Abstracts Core, Compendex, Geobase, INSPEC, Civil Engineering Abstracts
  • Anahtar Kelimeler: Hydrogeochemistry, Stable isotope, Geothermal water, Eastern Turkey, NATURAL HYDROTHERMAL SYSTEMS, ANATOLIAN FAULT ZONE, HEAT-FLOW, CRUSTAL THICKNESS, OXYGEN ISOTOPES, THERMAL WATERS, LAKE VAN, AR-AR, PLATEAU, SULFATE
  • Hacettepe Üniversitesi Adresli: Evet

Özet

The hydrogeochemistry of geothermal waters from 31 geothermal fields in eastern Turkey is investigated with regard to major ion compositions, stable(delta O-18-delta H-2-delta S-34) and tritium (H-3) isotope systematics. Discharge temperature of studied waters varies from 24 to 65 degrees C. Four different geochemical processes were found to control the major ion concentrations of waters which include dissolution of carbonates, fluid-mineral interaction, oxidation of sulfur-bearing minerals, and chloride enrichment. The northern, central and southern provinces are represented by different local meteoric water lines (LMWL) with deuterium excess of 15.0, 13.9 and 16.5 parts per thousand. V-SMOW, respectively. The stable isotope values of the thermal waters are close to LMWLs and indicate a meteoric origin. The enrichment in oxygen isotope composition (0.6 to 7.7 parts per thousand V-SMOW) in some thermal waters resulted from water-rock interaction process and O-18-exchange process between CO2 and H2O. The delta S-34 and delta O-18 contents in dissolved sulfate cover a wide range from 6.2 to 32 parts per thousand V-CDT and from -2.5 to 14.8 parts per thousand V-SMOW, respectively, indicating that the sulfate isotope systematics of the majority of waters is governed by dissolution of terrestrial sulfate and marine evaporites. The reservoir temperatures estimated by chemical and isotopic geothermometers of K-Mg (27-127 degrees C), silica (29-179 degrees C) and O-1(8)SO4-H2O (51-196 degrees C), and by the silica-enthalpy mixing model (130 to 235 degrees C) yielded inconsistent results. The geological factors (e.g., relatively thick crust, low surface heat flux, absence of ideal cover units) in eastern Turkey have resulted in the development of low- or moderate-temperature geothermal systems. (C) 2019 Elsevier B.V. All rights reserved.