| Abstract |
Utilization of low temperature geothermal fluids is an alternative energy source to fossil fuels and plays an increasingly important role in space heating in Northern China. There are about 16 local low temperature geothermal systems had been discovered in Shandong Peninsula by following the hot springs in the surface. However, the origin of geothermal water, fluid mixing, water-rock interaction processes, reservoir temperatures are still largely unexplored. In order to answer these questions, major, trace elements and water isotope analysis were performed for borehole and natural groundwaters in the Shandong Peninsula area. 16 geothermal water samples were collected and analysed in this study during Sep.,30th to Dec. 17th, 2018. Other 48 groundwater data are collected from database of former studies in the Shandong Peninsula. The analysis result showed that geothermal fluid temperatures ranging from 28 to 83°C, pH from 6.84 to 8.54, Cl from 41.4 to 5554 ppm, Na from 110 to 2781 ppm, SiO2 from 34.2 to 137 ppm, B from 0.04 to 0.91 ppm, CO2 from 29.4 to 522 ppm, δD from -72.0 to -44.3‰ and δ18O from -9.95 to -6.06‰. Based on the δD, δ18O, B, Na and Cl contents, it is shown that the groundwaters were mainly of modern meteoric origin, with some seawater mixing in the coast areas. The fluid chemical concentrations have been modified by primary rock leaching. The extent of reaction (ξ) is between 0.001 and 0.01 kg of rock dissolved per kg of geothermal water. SiO2 geothermometor might be used better in this study, which shows the reservoir temperature range from around 80 °C to 130 °C. |