Technical note: An analytical approach for (U–Th) /He dating of goethite by sample encapsulation in quartz ampoules under vacuum, with an example from the Amerasian Basin, Arctic Ocean

Abstract

We propose an analytical approach for (U–Th) / He dating of Fe-(oxyhydr)oxides that includes sealing samples in quartz ampoules and demonstrates its suitability as a reliable tool for the investigation of geological processes. The (U–Th) / He ages of goethite clasts and veins from Fe- and Mn-oxide cemented rocks recovered from the slope of the Chukchi Borderland in the Amerasia Basin demonstrate reproducibility, yielding a weighted mean age of 8.6 ± 0.3 Ma (n = 4) and 4.8 ± 0.4 Ma (n = 2), respectively, providing insights into the Neogene mineralization history of the region. This study also focuses on the sample preparation technique, which might influence the (U–Th) / He ages. Our data indicate that some of U can be leached from the goethite during sonication by distilled water, which might result in erroneous (U–Th) / He ages of multi-mineral grains. However, the analyzed goethite samples were formed in a specific underwater environment; so far it is not clear whether the same behavior of U would be observed in a terrestrial supergene goethite.