Thursday, 8 September 2005 - 9:10 AM

This presentation is part of: Astrophysics and Cosmochemistry II

3He, 20,21,22Ne, 14C, 10Be, 26Al and 36Cl in magnetic fractions of terrestrial collections of cosmic dust from Greenland and Antarctica

A. J. Timothy Jull1, Devendra Lal2, Susan Taylor3, Michel Maurette4, Rainer Wieler5, Ansgar Grimberg5, Loic Vacher2, Lanny R. McHargue1, Stewart P.H.T. Freeman6, Colin Maden6, Christoph Schnabel6, Sheng Xu6, Robert C. Finkel7, and Kurt Marti8. (1) NSF Arizona AMS Laboratory, Univ of Arizona, 1118 East Fourth St, Tucson, AZ 85721, (2) Scripps Institution of Oceanography, University of California San Diego, Geosciences Research Division, La Jolla, CA 92093, (3) Cold Regions Research & Engineering Laboratory, Hanover, NH 03755, (4) IN2P3, Bat 108, CSNSM, Orsay, 91405, France, (5) Isotope Geology and Mineral Resources, ETH Zurich, Zuerich, 8092, Switzerland, (6) Scottish Universities Environmental Research Centre, Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride, G75 0QF, United Kingdom, (7) CAMS, Lawrence Livermore National Laboratory, Livermore, CA 94550, (8) Department of Chemistry, University of California San Diego, La Jolla, CA 92093

We have measured the concentrations of the nuclides 3He, 20,21,22Ne, 14C, 10Be, 26Al and 36Cl in two samples of magnetic fractions in separates from particulates recovered from the South Pole Water Well (SPWW) (Taylor et al., 2000) and from Blue Lake in Greenland (Maurette et al., 1990). Previous studies on 2 radionuclides, 10Be and 26Al in cosmic dust collections were performed on single spherules from marine sediments and ice (e.g. Raisbeck and Yiou, 1987; Nishiizumi et al., 1987). 14C measurements were made by two methods: combustion in O2 at a series of temperatures, and by acid-etching in vacuo. Aqueous solutions from acid-etching were analyzed for 10Be, 26Al and 36Cl. Concentrations of 14C, 10Be, 26Al and 36Cl were determined using the AMS technique. 3He and 20,21,22Ne measurements were made in aliquots of magnetic fractions in releases at 2 temperatures: 850ｰC and 1750ｰC.

These data clearly suggest that the magnetic fractions analyzed have (spallogenic) cosmogenic 14C, 10Be, 26Al and 36Cl, and possibly 21Ne. The 3He /4He, 20Ne/22Ne and 4He/20Ne ratios show a solar wind signature, indicating that at least some of the grains were irradiated as small particles in space. The 26Al and 36Cl data allow us to estimate the level of terrestrial adsorbed 14C and 10Be in the samples. The latter is expected in both the collections. The SPWW (Antarctic) samples are known to contain magnetic materials as contamination arising from the mass wastage of the boiler used to heat water (Taylor et al., 2000).

 

Detailed analyses of the data will be presented. These results on the magnetic fractions of terrestrial materials expected to be relatively rich in extra-terrestrial component, open up a new window for the study of extraterrestrial material in terrestrial reservoirs. The magnetic component is likely more resistant to weathering and can be easily separated from terrestrial components.

Maurette M. et al. (1990) In: “From mantle to meteorites”, Eds.: K. Gopalan, V. K. Gaur. B. L.K. Somayajulu and J. D. Macdougall, pp. 87-126.

Nishiizumi K. et al. (1991) EPSL, 104, 315-324.

Raisbeck G. M. and Yiou F. (1987) Meteoritics, 22, 485-486.

Taylor S. et al. (2000) Meteorit. Planet. Sci. 35, 651-666.


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