Abstract The first gas and thermal measurements at the summit of the Gamalama volcano indicate that the system is dominated by hydrothermal processes. This is highlighted by the prevalence of H2S over SO2 (H2S/SO2 = 2–8), a high CO2/SO2 ratio (76–201), and a low heat transfer (3.0 MW) to the surface. A relative variation in gas composition is observed along the degassing fracture zone, possibly due to partial S scrubbing. Despite this surface hydrothermal signature, the system exhibits high gas equilibrium temperatures (425–480 °C), indicating that fluids are not exclusively derived from a boiling hydrothermal aquifer, but also sourced by cooling and crystallizing basaltic magma at deep that continues to inject magmatic fluids into the system. This hydrothermally dominated activity on Gamalama possibly persisted over the last two decades, during which a high number of eruptive events were witnessed. The period coincides with the opening of large fractures at the summit that subsequently shifted the volcanic activity from the crater center to the peripheral fractures zones. These fractures that possibly developed in response to the regional geodynamics, have weakened the hydrothermal seal, allowing the pressure developed by the hydrothermal-magmatic system and promoted by the high annual rainfall, to rapidly exceeds the tensile strength of the seal leading to the numerous phreatic eruptions.

中文翻译：

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频繁喷发的加马拉马火山（印度尼西亚）的首次气体和热测量揭示了一个以热液为主的岩浆系统

摘要 Gamalama 火山顶峰的第一次气体和热测量表明该系统以热液过程为主。H2S 比 SO2 普遍 (H2S/SO2 = 2–8)、高 CO2/SO2 比率 (76–201) 和向表面的低传热 (3.0 MW) 突出了这一点。沿着脱气断裂带观察到气体成分的相对变化，可能是由于部分 S 洗涤。尽管有这种地表热液特征，该系统仍表现出较高的气体平衡温度（425-480 °C），这表明流体不仅来自沸腾的热液含水层，而且还来源于继续注入岩浆的深部玄武质岩浆的冷却和结晶。流体进入系统。在过去的二十年里，这种以热液为主的活动可能在加马拉马持续存在，在此期间目睹了大量的喷发事件。这一时期恰逢山顶大裂缝的打开，随后火山活动从火山口中心转移到外围裂缝区。这些可能响应区域地球动力学的裂缝，削弱了热液密封，使热液-岩浆系统产生的压力和年降雨量增加的压力迅速超过密封的抗拉强度，导致大量的潜水。喷发。