The Manuguru geothermal area, situated in the Telangana state, is one of the least explored geothermal fields in India. In this study, the chemical characteristics of the groundwater (thermal and non-thermal waters) are investigated to elucidate the source of the solutes dissolved in the water and to determine the approximate residence time of the thermal waters. The major hydrogeochemical processes controlling the groundwater geochemistry have been deciphered using multivariate statistical analysis, conventional graphical plots and geochemical modelling (PHREEQC). Geochemically different groundwater clusters (bicarbonate type, bicarbonate–chloride type and chloride type) can clearly be identified from the chemometric analysis, i.e. PCA and HCA. Thermal waters are mostly Na–HCO₃ type having low EC and TDS compared to non-thermal groundwaters. Silicate weathering and ion exchange mainly contribute to the dissolved ion budget in the groundwater of the study area. The carbon isotopic composition of DIC (δ¹³C) points to silicate weathering with soil CO₂ coming from C₃ type of plants. Stable isotopes (δ¹⁸O, δ²H) data confirm the meteoric origin of the thermal waters with no oxygen-18 shift. The low tritium values of the thermal water samples reveal the long circulation time (> 50 years) of the recharging waters. Radiocarbon dating (¹⁴C) shows that the approximate residence time of the thermal waters ranges from 9952 to 18,663 year BP (before present).

中文翻译：

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同位素-地球化学综合方法表征印度中焓地热系统

位于Telangana州的Manuguru地热区是印度勘探最少的地热田之一。在这项研究中，研究了地下水（热水和非热水）的化学特性，以阐明溶解在水中的溶质的来源，并确定热水的近似停留时间。使用多变量统计分析，常规图形图和地球化学模型（PHREEQC），已经解释了控制地下水地球化学的主要水文地球化学过程。从化学计量学分析中可以清楚地识别出地球化学上不同的地下水团簇（碳酸氢盐类型，碳酸氢盐-氯化物类型和氯化物类型），即PCA和HCA。热水主要是Na–HCO ₃与非热地下水相比，其EC和TDS较低。硅酸盐的风化作用和离子交换作用主要是导致研究区域地下水中溶解离子的收支平衡的原因。DIC的碳同位素组成（δ ¹³ C）指向硅酸盐风化与土壤CO ₂由C来₃型植物。稳定同位素（δ ¹⁸ O，δ ² 2H）数据确认没有氧18移热水域的大气原点。热水样品的t值低，表明补给水的循环时间长（> 50年）。放射性碳测年（¹⁴ C）表明，热水的近似停留时间为BP的9952至18,663年（之前）。