Stable potassium isotopes are one of the emerging non-traditional isotope systems enabled in recent years by the advance of Multi-Collector Inductively-Coupled-Plasma Mass-Spectrometry (MC-ICP-MS). In this review, we first summarize the geochemical and cosmochemical properties of K, its major reservoirs, and the analytical methods of K isotopes. Following this, we review recent literature on K isotope applications in the fields of geochemistry and cosmochemistry. Geochemically, K is a highly incompatible lithophile element, and a highly soluble, biophile element. The isotopic fractionation of K is relatively small during magmatic processes such as partial melting and fractional crystallization, whereas during low-temperature and biological processes fractionation is considerably larger. This resolvable fractionation has made K isotopes promising tracers for a variety of Earth and environmental processes, including chemical weathering, low-temperature alteration of igneous rocks, reverse weathering, and the recycling of sediments into the mantle during subduction. Sorption and interactions of aqueous K with different clay minerals during cation exchange and clay formation are likely to be of fundamental significance in generating much of the K isotope variability seen in samples from the Earth surface and samples carrying recycled surface materials from the deep Earth. The magnitude of this fractionation is process- and mineral-dependent. Comprehensive quantification of pertinent K isotope fractionation factors is currently lacking and urgently needed. Significant fractionation during biological activities, such as plant uptake, demonstrates the potential utility of K isotopes in the study of the nutrient cycle and its relation to the climate and various ecosystems, enabling new and largely unexplored avenues for future research.

Of significant importance to the cosmochemistry community, K is a moderately volatile element with large variations in K/U ratio observed among chondrites and planetary materials. As this indicates different degrees of volatile depletion, it has become a fundamental chemical signature of both chondritic and planetary bodies. This volatile depletion has been attributed to various processes such as solar nebula condensation, mixing of volatile-rich and -poor reservoirs, planetary accretional volatilization via impacts, and/or magma ocean degassing. While K isotopes have the potential to distinguish these different processes, the current results are still highly debated. A good correlation between the K isotope compositions of four differentiated bodies (Earth, Mars, Moon, and Vesta) and their masses suggests a ubiquitous volatile depletion mechanism during the formation of the terrestrial planets. It is still unknown whether any of the K isotopic variation among chondrites and differentiated bodies can be attributed to inherited signatures of mass-independent isotopic anomalies.

稳定钾同位素是近年来随着多接收器电感耦合等离子体质谱 (MC-ICP-MS) 的进步而出现的新兴非传统同位素系统之一。本文首先对钾的地球化学和宇宙化学性质、主要储集层以及钾同位素的分析方法进行了综述。接下来，我们回顾了钾同位素在地球化学和宇宙化学领域应用的最新文献。从地球化学角度来看，K 是一种高度不相容的亲石元素，也是一种高度可溶的亲生物元素。在部分熔融和分级结晶等岩浆过程中，钾的同位素分馏相对较小，而在低温和生物过程中，钾的同位素分馏则相当大。这种可分辨的分馏使钾同位素成为各种地球和环境过程的示踪剂，包括化学风化、火成岩的低温蚀变、逆风化以及俯冲过程中沉积物再循环到地幔中。在阳离子交换和粘土形成过程中，水性钾与不同粘土矿物的吸附和相互作用可能对于产生地球表面样品和携带来自地球深处回收的表面材料的样品中观察到的钾同位素变异性具有重要意义。这种分馏的程度取决于工艺和矿物。目前缺乏且迫切需要对相关 K 同位素分馏因子进行全面量化。植物吸收等生物活动过程中的显着分馏证明了钾同位素在营养循环及其与气候和各种生态系统的关系研究中的潜在效用，为未来的研究开辟了新的、很大程度上尚未探索的途径。

K 对宇宙化学界具有重要意义，它是一种中等挥发性元素，在球粒陨石和行星材料中观察到 K/U 比率变化很大。由于这表明不同程度的挥发性损耗，它已成为球粒陨石和行星体的基本化学特征。这种挥发物的消耗归因于各种过程，例如太阳星云凝结、富含挥发物和贫挥发物的储存库的混合、通过撞击造成的行星吸积挥发和/或岩浆海洋脱气。虽然钾同位素有可能区分这些不同的过程，但目前的结果仍然存在很大争议。四个不同天体（地球、火星、月球和灶神星）的钾同位素组成与其质量之间存在良好的相关性，这表明在类地行星形成过程中存在普遍存在的挥发性消耗机制。目前尚不清楚球粒陨石和分化体之间的 K 同位素变化是否可以归因于与质量无关的同位素异常的遗传特征。