《我国干热岩地热资源赋存及开发利用调查》参考2020年第1期（总第44期）
详细信息
- 编辑：雒毅
- 发布日期：2020 年1月30日
- 分类：C
- 期次：2020年第1期（总第44期）
- 发布单位：咨询服务室
- 正文：1. Major, trace, and rare earth element geochemistry of the Ayder and İkizdere (Rize, NE Turkey) geothermal waters: Constraints for water–rock interactions
作者: EsraHatipoğlu Temizel
文献源：Geothermics
摘要：This study aims to determine the sources of rare earth elements (REEs) in the geothermal and cold waters of the Ayder and İkizdere (Rize) geothermal fields (NE Turkey). The differentiation stages of REEs in water–rock interactions as well as the migration processes of aqueous complexes of rare earth elements (REEs) in the waters were evaluated. Based on results for major ions, the kizdere geothermal water with a temperature of 61 °C can be classified as Na-Ca-HCO3 type water, whereas the Ayder geothermal water with a temperature of 54 °C can be classified as Na-Ca-CO3−SO4 type water. ΣREE concentrations were between 0.64–2.13 μg/L in the kizdere geothermal field and between 0.01–0.32 μg/L in the Ayder geothermal field. As well as lower pH values, the waters in the kizdere geothermal field were found to have higher REE concentrations than those of the Ayder geothermal field. Geochemical characteristics of REEs from the host rocks and water samples indicate that the REEs are derived from granite and granodiorite host rocks. Normalized REE plots for the host rocks and waters showed similar patterns, and in particular, the waters interacting with granitic rocks display a pronounced positive Eu anomaly and a less clear Ce anomaly. The positive Eu anomaly in the altered surrounding rocks is associated with argillization of feldspars in the granitic host rocks that the waters have passed through. Application of a speciation model showed that amorphous iron oxy-hydroxide complexes of REEs were significant for a pH value of nearly 9 in the Ayder geothermal waters whereas fluoride complexes are dominant in the İkizdere geothermal waters whose pH is just below 7.
2. Geochemical constraints on supercritical fluids in geothermal systems
作者：MatyldaHeřmanská
文献源：Journal of Volcanology and Geothermal Research
摘要：Supercritical fluids with temperatures of ~400–500 °C have been reported from several active geothermal fields worldwide. Although the utilization of such fluids may multiply power production from new and already exploited geothermal systems, the fluid origin and chemical controls on their composition remain unclear. We performed flow-through high-temperature (<400–420 °C) experiments at 34–69 bar to study the chemical and mineralogical changes associated with supercritical fluid formation upon boiling of subcritical geothermal fluids of varying chemical composition. Based on geochemical modeling and laboratory results, we propose that an important mechanism of supercritical fluid formation is conductive heating and boiling of subcritical geothermal groundwater by a magmatic intrusion. Such supercritical fluids will display low concentrations of mineral-forming elements (Si, Na, K, Ca, Mg, Al) with their concentrations being controlled by the solubility of salts, oxides, and aluminum silicates in high-temperature (>400 °C) and low-density (ρ < 0.3 g cm−3) fluids. In contrast, supercritical fluids will show elevated concentrations of volatile elements (C, S, B) of crustal and/or mantle origin with their concentrations often being similar to those of subcritical geothermal fluids. Associated mineral deposition, dominated by quartz, aluminum silicates, and salts, may form in the vicinity of the intrusion. Comparison of the modeling and laboratory results with observed chemical composition of natural supercritical fluid discharges indicates that conductive heating and boiling of subcritical geothermal groundwater may indeed be the formation mechanism of such fluids observed for example at Krafla (Iceland), Menengai (Kenya), Los Humeros (Mexico), and Larderello (Italy) with an addition of volcanic gases in many cases. Metal and salt-rich supercritical fluids, for example at Kakkonda (Japan), may also exist in geothermal systems. However, such supercritical fluids are considered to have been trapped upon crystallization of the magmatic intrusion.
中文摘要
© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |