Abstract We report here on the first focused study of gas discharges and thermal spring waters at Okmok volcano since the 2008 phreatomagmatic eruptions. Results include the first compositional gas data from Okmok with minimal air contamination and the first data on magmatic carbon in Okmok spring waters. Chemical and isotopic analyses of the waters and gases are used to assess the character of Okmok fluids eight years after the eruptions ceased. Gases from vents on intracaldera Cone C have high concentrations of H2 and contain H2S rather than SO2, demonstrating the influence of a hydrothermal system, while isotope values of carbon (−10.2 to −8.9‰) and helium (~8 RA) confirm the presence of magma-derived volatiles. Estimates of equilibrium temperatures for the Cone C gas are ~230 ± 30 °C. A much cooler reservoir with a maximum temperature of ~55 °C feeds the intracaldera warm springs. Based on discharge measurements of creeks draining the caldera, the total heat output of the warm springs is estimated to be about 32 MW. Gas data from a single location of steaming ground at the Geyser Bight geothermal area southwest of the Okmok Caldera are given. The gas is typical of geothermal gases with high concentrations of H2S and an air-corrected helium isotope ratio of 7.15 RA.

中文翻译：

---

阿拉斯加奥克莫克火山喷发后的气体和热水研究

摘要 我们在此报告了自 2008 年岩浆喷发以来奥克莫克火山气体排放和温泉水的首次重点研究。结果包括来自 Okmok 的第一个空气污染最小的成分气体数据和关于 Okmok 泉水中岩浆碳的第一个数据。喷发停止八年后，水和气体的化学和同位素分析用于评估 Okmok 流体的特性。来自火山口内锥体 C 上的喷口的气体具有高浓度的 H2 并且包含 H2S 而不是 SO2，这证明了热液系统的影响，而碳（-10.2 至 -8.9‰）和氦（~8 RA）的同位素值证实了存在岩浆衍生的挥发物。Cone C 气体的平衡温度估计值为 ~230 ± 30 °C。一个温度更高的水库，最高温度约为 55 °C，为火山口内的暖泉提供水源。根据排出火山口的小溪的排放测量，估计暖泉的总热量输出约为 32 MW。给出了奥克莫克火山口西南的间歇泉湾地热区单一位置的气体数据。该气体是典型的地热气体，具有高浓度的 H2S 和 7.15 RA 的空气校正氦同位素比。