Abstract

The south of Hunan is rich in low temperature geothermal water resources, yet their formation mechanism has not been well investigated. This study focused on the occurrence conditions of geothermal water and estimation the thermal reservoir temperature and the circulation depth of geothermal water in this area. The hydrogeochemical analyses of 23 geothermal water samples are proceeded with the help of Origin, PHREEQC and Aquachem software. The results show that the main hydrochemical type of geothermal water in the study area is HCO₃·SO₄–Ca·Mg and HCO₃–Na. The δD and δ¹⁸O of the geothermal water samples show a linear right-up trend, indicating the geothermal waters were recharged by meteoric water. The mineral saturation index was calculated by PHREEQC, which indicated that the quartz and chalcedony minerals were close to the saturation state. The reservoir temperature range of geothermal water is estimated to be 38–122°C by using a silica (quartz) geothermometer, with an average of 73°C. The geothermal water circulation depth range calculated by the geothermal gradient is 1–4 km, with an average of 2.13 km.

中文翻译：

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湘南低温地热水水文地球化学及形成

摘要

湘南地区低温地热水资源丰富，但其形成机制尚未得到深入研究。本研究重点研究了地热水的赋存条件，估算了该地区的热库温度和地热水循环深度。借助 Origin、PHREEQC 和 Aquachem 软件对 23 个地热水样品进行了水文地球化学分析。结果表明，研究区地热水主要水化学类型为HCO ₃ ·SO ₄ –Ca·Mg和HCO ₃ –Na。δD 和 δ ¹⁸地热水样品的O呈现线性右上趋势，表明地热水受到了大气水的补给。通过PHREEQC计算出矿物饱和指数，表明石英和玉髓矿物接近饱和状态。通过硅（石英）地温计测得地热水库温度范围为38～122℃，平均为73℃。按地温梯度计算的地热水循环深度范围为1～4 km，平均2.13 km。