Abstract Helium isotopes are useful for tracing terrestrial water movement and calculating residence times, which have important implications for radioactive waste disposal and carbon capture and storage projects. Helium concentrations are generally measured directly in water samples; however, this is not always possible. In this scenario, the He concentration equilibrium between pore waters and He accessible volumes (e.g., fluid inclusions, hereafter HAV) in minerals (e.g., quartz) can be utilized to determine He concentrations. In this study, the He partial pressure was measured in HAVs of quartz grains collected from cores of the Kola Super Deep Borehole (KSDB) using isothermal He extraction/saturation experiments. A large fraction of He was released from these samples during the first interval of isothermal heating, indicating a destruction of the unstable HAVs, likely due to decrepitation of fluid inclusions. We present a new approach to calculate He partial pressures using only the He fraction released from the stable HAVs. This approach gives a He partial pressure pHe of ≅ 1.5 atm at depths of ~ 10 km. When combined with solubility data, this value suggests a high He concentration in the deep pore waters nearby the KSDB, ≅ 1.3 × 10−6 mol (cc H2O)−1, indicating a long residence time of He atoms in a deep water – mineral system, close to the age of the regional metamorphism (≅1700 Ma). The 3He/4He in the deep KSDB quartz samples (and the pore waters) are ~ 3 × 10−8, typical of radiogenic He generated in 10 km deep Archean rocks of the KSDB. Importantly, external fluxes are not needed to explain He isotope abundances in rocks, minerals and pore waters at these depths.

中文翻译：

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10 公里深地下水中的氦浓度和同位素组成

摘要 氦同位素可用于追踪陆地水运动和计算停留时间，这对放射性废物处理和碳捕获和储存项目具有重要意义。通常直接在水样中测量氦浓度；然而，这并不总是可能的。在这种情况下，可以利用孔隙水和矿物（例如石英）中的 He 可接近体积（例如，流体包裹体，以下简称 HAV）之间的 He 浓度平衡来确定 He 浓度。在这项研究中，使用等温 He 提取/饱和实验测量从 Kola 超深钻孔 (KSDB) 岩心收集的石英颗粒的 HAV 中的 He 分压。在等温加热的第一个间隔期间，从这些样品中释放出大部分 He，表明不稳定的 HAV 被破坏，可能是由于流体包裹体的爆裂。我们提出了一种仅使用从稳定 HAV 释放的 He 分数来计算 He 分压的新方法。这种方法在约 10 公里的深度给出了 ≅ 1.5 atm 的 He 分压 pHe。当与溶解度数据结合时，该值表明 KSDB 附近深孔隙水中的 He 浓度较高，≅ 1.3 × 10−6 mol (cc H2O)−1，表明 He 原子在深水矿物中的停留时间较长系统，接近区域变质作用时代（≅1700 Ma）。KSDB 深部石英样品（和孔隙水）中的 3He/4He 为 ~ 3 × 10−8，典型的放射成因 He 在 KSDB 深 10 公里的太古代岩石中产生。重要的是，不需要外部通量来解释岩石中的 He 同位素丰度，