Abstract We investigated the major ion and stable isotope geochemistry and used silica and cation concentrations to assess the geothermometry of hot springs along the Malawi Rift Zone (MRZ). The MRZ is a magma-poor rift, where potential geothermal energy is postulated from elevated heat flow and the occurrence of hot springs. Our objectives were to (1) estimate hot spring reservoir temperatures, (2) identify processes that could affect hot spring water during the ascent from their geothermal reservoirs, and (3) identify the most promising areas for geothermal energy generation. New geochemistry data from 27 hot springs were analyzed and classified as Na-HCO3, Na-SO4, or Na-Cl (SO4) water types controlled mainly by the mineralogy of the host rocks. The hot springs in the MRZ are associated with the local meteoric waters that infiltrate at depth and are heated by an anomalously high geothermal gradient. Our findings indicate that a parent geothermal fluid is mixed and diluted with a proportion of more than ∼45 % of cold water from shallow aquifers. Additionally, other processes such as water-rock interaction, and CO2 outgassing take place during the ascent of the geothermal fluid to the surface. The quartz conductive silica geothermometer indicates reservoir temperatures that range from 60 °C to 130 °C, with enthalpies ranging from 250 kJ/kg to 537 kJ/kg, respectively. However, the Na-K cation geothermometer indicates reservoir temperatures from 92 °C to 190 °C with enthalpies from 388 kJ/kg to 808 kJ/kg. Three areas of potential geothermal energy generation were identified: (1) The Chiweta area, (2) Nkhotakota area, and (3) the Shire graben area. We conclude that the hot springs along the MRZ have geothermal energy capabilities of medium to low enthalpy that can be exploited for electricity generation or other direct uses.

中文翻译：

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从沿马拉维裂谷带的地温测量和温泉混合模型估计的中低焓地热储层

摘要 我们研究了主要离子和稳定同位素地球化学，并使用二氧化硅和阳离子浓度来评估马拉维裂谷带 (MRZ) 沿线温泉的地温测量。MRZ 是一个岩浆贫乏的裂谷，其中潜在的地热能是由升高的热流和温泉的出现推测出来的。我们的目标是 (1) 估计温泉水库温度，(2) 确定在从地热库上升过程中可能影响温泉水的过程，以及 (3) 确定最有希望产生地热能的区域。分析了来自 27 个温泉的新地球化学数据，并将其归类为 Na-HCO3、Na-SO4 或 Na-Cl (SO4) 水类型，主要受主岩的矿物学控制。MRZ 中的温泉与当地的大气水有关，这些水在深处渗透并被异常高的地温梯度加热。我们的研究结果表明，母地热流体与来自浅层含水层的约 45% 以上的冷水混合并稀释。此外，在地热流体上升到地表的过程中，还会发生其他过程，例如水-岩相互作用和 CO2 脱气。石英导电二氧化硅地温计显示的储层温度范围为 60 °C 至 130 °C，焓值范围分别为 250 kJ/kg 至 537 kJ/kg。然而，Na-K 阳离子地温计显示储层温度为 92 °C 至 190 °C，焓为 388 kJ/kg 至 808 kJ/kg。确定了三个潜在地热能发电领域：(1) Chiweta 地区，(2) Nkhotakota 地区，和 (3) Shire 地堑地区。我们得出结论，MRZ 沿线的温泉具有中低焓的地热能能力，可用于发电或其他直接用途。