The energy demand is increasing exponentially on the global scale. To meet this demand, new alternative energy sources are explored, and geothermal energy makes one of the important renewable resources. Inherently, the north-eastern states of India have enormous geothermal potential; however, detailed studies evaluating their geothermal potential are quite limited. In view of this, the Garampani and Gelekipung thermal spring clusters of Karbi Anglong district, Assam (India), were evaluated for their geochemical characteristics and geothermal reservoir potential. Water samples from the thermal springs along with groundwater and river water from the surrounding areas were collected seasonally and investigated for various parameters. Thermal waters are NaCl type and show distinct physico-chemical characteristics, as compared to groundwater (Na-HCO3) and surface water (Ca-HCO3 type). The chemistry of thermal water indicates long-term water-rock interactions with the basement rock and does not show an appreciable seasonal variability. The influence of thermal water on groundwater chemistry has been observed during the pre-monsoon season. However, in the post-monsoon season, the delayed monsoonal freshwater influxes seem to diminish any such effect on the groundwater chemistry. The placement of thermal waters in the mature water field of the anion variation diagram confirms their suitability for chemical geothermometry. Silica and cation geothermometry indicates that the geothermal reservoir temperature ranges between 76.3 and 105.8 degrees C. Thus a low-enthalpy geothermal system exists in the Garampani and Gelekipung thermal spring areas. The radiogenic heat production of the granitic basement rock of the study area was found to range between 2.49 and 8.14 mu W/m(3).
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