Identifying large chondrites using cosmogenic radionuclides

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Nuclear Instruments & Methods in Physics Research Section B-Beam Interactions with Materials and Atoms 268,7-8 (2010) 1185-1188;


We measured the concentrations of the cosmogenic radionuclides Be-10, Al-26, Cl-36 and Ca-41 in the metal and stone fractions of three large chondrite showers to determine their pre-atmospheric size. Large chondrites are characterized by substantial contributions of neutron-capture Ca-41 in the stone fraction (up to similar to 2 dpm/gCa), low radionuclide concentrations in the metal fraction and high Be-10(stone)/Be-10(metal) ratios. Based on the measured concentrations in comparison with calculated cosmogenic nuclide depth profiles, using a semi-empirical and a purely physical model, we conclude that these objects had pre-atmospheric radii ranging from similar to 80 cm to >3 m. We conclude that the semi-empirical model is more reliable for spallogenic production rates in large objects, while the purely physical model is more reliable for neutron-capture products. (C) 2009 Elsevier B.V. All rights reserved.

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