Chemical procedure for extracting 129I, 60Fe and 26Al from marine sediments:: Prospects for detection of a ∼2.8 My old supernova

For the past three years, we have been developing a procedure to measure carrier-free I-129/I in gram size quantities of marine sediments containing microgram quantities of iodine. Potential applications involve dating of old (>10 My) sediments and the detection of I-129 (t(1/2) = 15.7 My) from a purported supernova (SN) explosion similar to 2.8 million years ago, that has been inferred from a Fe-60 (t(1/2) = 1.5 My) signal in a deep-sea ferromanganese crust [K. Knie, G. Korschinek, T. Faestermann, E.A. Dorfi, G. Rugel, A. Wallner, Phys. Rev. Lett. 93 (2004) 171103]. The procedure consists in washing the sediment with a NH2OH center dot HCl-HOAc mixture, extraction of iodine from the organic phase with TMAH, separation and purification using anion-exchange chromatography, and coprecipitation as Agl-Agl(2)O. We realized the washing step, which extracts authigenic iron and aluminum, could also be used to measure Fe-60/Fe-56 and Al-26/Al-27 in this phase of the same sediment sample. We outline here the chemical procedures developed, and briefly comment on their possible application to the supernova problem. We also point out a large discrepancy between the theoretically calculated I-129/I-127 ratio in pre-anthropogenic marine sediments, and that derived from experimental measurements. (c) 2007 Elsevier B.V. All rights reserved.