Understanding alteration processes in geothermal systems through remote sensing can help assess the prospectivity of a geothermal field. As a result of which, alteration detection and mapping are vital in the early exploration stage. However, many geothermal surface manifestations, which are evidence of alteration processes, often occur in densely vegetated areas, particularly in tropical regions. Current lithological mapping techniques using passive remote sensing systems can have problems with vegetation canopy completely blocking the signal. LiDAR, an active remote sensing system, can be a solution since it can (partially) penetrate vegetation canopy. It collects information from the ground in 3D-coordinated points with laser return intensity (LRI) values. In this study, we test for the first time the possibility of differentiating hydrothermally altered rocks through their LRI values in a laboratory experiment. We scanned selected altered and unaltered rocks under different moisture and temperature conditions using a terrestrial laser scanner (at 1550 nm wavelength). Our results show LRI values follow the degree of alteration: strongly altered rocks have the highest LRI, unaltered rocks are at the lowest, and weakly altered rocks show an intermediate response. Varying moisture conditions decrease LRI values for all rocks, but the relative LRI order due to alteration remains intact. We recorded no significant temperature effect on LRI values for any of the alteration stages. Our results provide the first evidence that rocks with different hydrothermal alteration phases can be distinguished by their LRI values which opens up the potential for airborne mapping of geothermal surface manifestations with LRI.

通过遥感了解地热系统的蚀变过程有助于评估地热田的前景。因此，蚀变检测和绘图在早期勘探阶段至关重要。然而，作为蚀变过程证据的许多地热表面表现通常发生在植被茂密的地区，特别是在热带地区。当前使用被动遥感系统的岩性测绘技术可能存在植被冠层完全阻挡信号的问题。LiDAR 是一种主动遥感系统，可以作为一种解决方案，因为它可以（部分）穿透植被冠层。它从具有激光返回强度 (LRI) 值的 3D 坐标点中收集来自地面的信息。在这项研究中，我们首次在实验室实验中测试了通过 LRI 值区分热液蚀变岩石的可能性。我们使用地面激光扫描仪（波长 1550 nm）在不同湿度和温度条件下扫描了选定的蚀变和未蚀变岩石。我们的结果表明 LRI 值遵循蚀变程度：强烈蚀变的岩石具有最高的 LRI，未蚀变的岩石最低，弱蚀变的岩石表现出中等响应。不同的水分条件会降低所有岩石的 LRI 值，但由于蚀变导致的相对 LRI 顺序保持不变。我们记录到任何变化阶段的 LRI 值都没有显着的温度影响。