Noble gas thermometry on fluid inclusions in speleothems: Optimization and application of a new method for paleoclimate reconstruction

地下水中溶解惰性气体是古地温的优良指标。所谓惰性气体温度计的优势在于它能够提供可靠的绝对温度。它的缺点是受地下水档案的限制，在绝对测年和时间分辨率方面有局限性。碳酸盐烧结矿是可以精确测定年代和高分辨率的档案。然而，基于碳酸盐的18o值重建古温度是有问题的。最近，通过直接分析储存在微观包裹体中的滴落水中的稳定同位素，取得了一项改进。这种流体包裹体代表了一个气候档案，也可能被惰性气体温度计获取。如果可以测量碳酸盐岩流体包裹体中的惰性气体浓度并将其转化为温度，这将构成一种非常有力的古气候重建方法。它将结合稀有气体温度计和洞穴档案的优点。稀有气体将产生绝对温度重建，这将大大促进稳定同位素数据的解释。目前的项目结合了稀有气体分析和解释的经验，以及研究小组在洞穴主题方面的广泛知识。该项目计划采用最近开发的从流体包裹体中提取水的方法进行稀有气体分析，并评估该档案中稀有气体古温度计的潜力。

Dissolved noble gases in groundwater are established as excellent indicators of paleotemperatures. The strength of the so-called noble gas thermometer is its ability to provide reliable absolute temperatures. Its weakness is the confinement to the groundwater archive, which has limitations with regard to absolute dating and temporal resolution. Carbonate sinters are archives that can be dated precisely and with high resolution. However, the reconstruction of paleotemperatures based on (18O-values from carbonates is problematic. An improvement has been achieved recently by analysing the stable isotopes directly on the drip water that is stored in microscopic inclusions. Such fluid inclusions represent a climate archive that potentially can be accessed also by the noble gas thermometer. If noble gas concentrations in fluid inclusions of carbonates could be measured and converted into temperatures, this would constitute a very powerful method of paleoclimate reconstruction. It would combine the advantages of the noble gas thermometer and the speleothem archive. The noble gases would yield absolute temperature reconstructions, which would significantly facilitate the interpretation of stable isotope data. The current project combines experience in noble gas analytics and interpretation with the broad knowledge on speleothems present in the researcher group. The project plans to adapt recently developed methods of water extraction from fluid inclusions for noble gas analysis and to assess the potential of the noble gas paleothermometer in this archive.