Freiburg 2024 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 7: Accelerator Mass Spectrometry III

MS 7.6: Talk

Thursday, March 14, 2024, 12:30–12:45, HS 3042

⁵³Mn burial dating at Cologne-AMS — •Gereon Hackenberg¹, Markus Schiffer¹, Steven Binnie², Alfred Dewald¹, Tibor Dunai², Stefan Heinze¹, Timm-Florian Pabst¹, and Dennis Mücher¹ — ¹Insitute for Nuclear Physics, University of Cologne — ²Instiute for Geology and Mineralogy, University of Cologne

The CRC1211 Earth - Evolution at the Dry Limit investigates the formation and evolution of life and landscapes in severely water-limited environments, which constitute significant portions of the Earth. Age determination of sporadically deposited sediments in hyper-arid and arid regions poses challenges due to the absence of age-indicating fossils. In this presentation we discuss a novel approach using Accelerator Mass Spectrometry (AMS) to measure the cosmogenic ⁵³Mn/³He concentration in iron-titanium oxides (hematite, magnetite, titanomagnetite, ilmenite). Notably, ⁵³Mn, with a half-life of T=3.74*Ma, offers extended exposure times compared to 26Al/10Be burial dating.

The utilization of AMS for 53Mn demands a Tandem accelerator with a high terminal voltage, exemplified by the 10MV FN-Tandem accelerator at the University of Cologne, coupled to a gas-filled magnet. Systematic optimization, including the development of a new Bragg detector and enhanced stability of the accelerator voltage via active slit control, has resulted in stable conditions for ⁵³Mn burial dating, achieving a low blank level of ⁵³Mn/⁵⁵Mn < 10⁻¹³. Our presentation includes dating results from Namibian iron oxide surface samples and a discussion of their implications for advancing our understanding of the geological dynamics within the Namibian desert.

Keywords: Mangan; AMS; 53