Bandara Dilshan, Smit Jeroen, Wohnlich Stefan, Heinze Thomas
Institute of Geology, Mineralogy and Geophysics, Ruhr-University Bochum, Universitätsstraße 150, 44801 Bochum, Germany.
iScience. 2025 Apr 8;28(5):112370. doi: 10.1016/j.isci.2025.112370. eCollection 2025 May 16.
Hot springs in orogenic geothermal systems are usually within 5-15 km of the recharge zone, either within the mountain range or along the mountain front. However, in Sri Lanka, hot springs are in the foreland up to 100 km away from their recharge zones in the Highland Complex. The absence of a sedimentary cover provides the opportunity to study fluid pathways along basement faults and fractures. We identify a fracture network that connects the recharge and discharge zones oriented 015°-090°. Its orientation to the regional stress field indicates that the majority of the faults and fractures are permeable to allow fluid transport. With a geothermal gradient of ∼20°C/km obtained from 1D modeling, the estimated maximum circulation depth of the hot spring water is 3.5-5 km. Such foreland geothermal systems may also occur in other parts of the world hidden under a sedimentary cover, which could provide an immense geothermal resource.
造山带地热系统中的温泉通常位于补给区5 - 15公里范围内，要么在山脉内部，要么沿着山前地带。然而，在斯里兰卡，温泉位于前陆地区，距离高地杂岩中的补给区可达100公里。缺乏沉积盖层为研究沿基底断层和裂缝的流体路径提供了机会。我们识别出一个连接补给区和排泄区的断裂网络，其走向为015° - 090°。它与区域应力场的方向表明，大多数断层和裂缝具有渗透性，能够允许流体运移。根据一维模型得到的约20°C/公里的地热梯度，温泉水的估计最大循环深度为3.5 - 5公里。这种前陆地热系统也可能出现在世界其他被沉积盖层覆盖的地区，这可能提供巨大的地热资源。
