Outgassing history and early atmospheric processes recorded by paleoatmospheric noble gases in Archaean rocks

行星大气的起源和演化是决定行星宜居性的关键条件。重要的大气形成过程是固体地球（即地幔和地壳）挥发物的输送和脱气过程，这在很大程度上受行星地球动力学的支配。地球稀有气体系统（如129I-129Xe）表明，很大一部分陆地挥发物从地球上消失了，大规模的地幔脱气发生在地球历史的早期。另一方面，地幔和地壳脱气是一个持续的过程。地球大气40Ar/36Ar比值的演化是约束地幔和地壳脱气模式和强度的敏感参数。我们提出的项目旨在a)测量古岩石中捕获的古大气氩和氙b)约束大气40Ar/36Ar比例的演变和固体地球的脱气)约束地球大气氙的起源，与其他太阳系储层（火星大气除外）相比，地球大气氙的组成是独特的。它们的意义取决于对各种核效应的数据校正。我们打算通过测量Kaapvaal克拉通和澳大利亚的太古代岩石（如燧石、页岩、热液石英）来改进现有的数据库。样品可从SPP1833内的合作和自己以前的研究中获得。样品将在中子辐照（以校正原位40K衰变和40Ar产生）和未辐照后进行测量，稀有气体将通过逐步加热和破碎提取，以区分包裹体中捕获的气体和矿物基质中的气体（例如来自放射性衰变）。这可以识别流体成分（高盐-高40Ar/36Ar，或低盐-低40Ar/36Ar），并通过Cl产生的中子38Ar进行识别。在破碎后不暴露于空气中，也可以逐步加热和逐步燃烧提取，并且对于耐酸残留物，可以在没有质量分馏的情况下从干酪根（来自页岩和燧石）中提取稀有气体。在有希望的样品中，氩和氙将同时提取，随后使用不同的质谱仪进行测量，特别是对于低氙量，我们将使用配备多离子计数的高灵敏度Noblesse质谱仪。

Origin and evolution of planetary atmospheres are key conditions that determine the habitability of a planet. Important atmosphere shaping processes are delivery of volatiles and degassing processes of the solid Earth, i.e. mantle and crust, which is largely governed by planetary geodynamics. Terrestrial noble gas systematics (e.g., 129I-129Xe) implies that a significant fraction of terrestrial volatiles were lost from the planet, and that massive mantle degassing occurred early in Earth´s history. On the other hand, mantle and crustal degassing are ongoing processes. The evolution of the 40Ar/36Ar ratio of the terrestrial atmosphere is a sensitive parameter that can constrain the modes and intensity of mantle and crustal degassing. Our proposed project aims at a) measuring paleoatmospheric argon and xenon trapped in ancient rocks b) constrain the evolution of the atmospheric 40Ar/36Ar ratio and degassing of the solid Earthc) constrain the origin of terrestrial atmospheric xenon, which is unique in composition when compared to other solar system reservoirs (except for the Martian atmosphere)Although recent studies reported interesting new results, they yielded only few values, and their significance depends on data correction for various nuclear effects. We intend to improve the present data base by measuring Archean rocks (e.g., cherts, shales, hydrothermal quartz) from the Kaapvaal craton and Australia. Samples are available from cooperations within SPP1833 and own previous studies. Samples will be measured after neutron irradiation (to correct for in situ 40K decay and 40Ar production) as well as unirradiated, and noble gases will be extracted by both stepwise heating and crushing, in order to differentiate between gases trapped in inclusions and those in mineral matrices (e.g. from radioactive decay). This enables recognition of fluid components (either high saline-high 40Ar/36Ar, or low saline-low 40Ar/36Ar) and their identification via neutron-produced 38Ar from Cl. Stepwise heating and also stepwise combustion extractions will also be possible after crushing without air exposure, and for acid resistant residues, enabling extraction of noble gases form kerogen (from shales and cherts) without mass fractionation. In promising samples, argon and xenon will be extracted simultaneously and subsequently measured by different mass spectrometers, especially for low xenon amounts we will apply a high sensitivity Noblesse mass spectrometer equipped with multi ion counting.