An Extraction System to Measure Carbon-14 Terrestrial Ages of Meteorites with a Tandetron AMS at Nagoya University

Abstract

We have constructed a system to extract carbon from meteorites using a vacuum-tight RF melting method in order to study radiocarbon activities in meteorites. The extraction system was examined using iron standards of known carbon content. The carbon extraction efficiencies and 14C ages of the iron standards by this method were compared with the results obtained previously by our older melting system and a wet oxidation method. Higher collection efficiencies of about 90% for the iron samples of relatively high carbon content were achieved by the new system. The efficiency of extracting a small amount of carbon is also near 90% after improving the extraction procedure. The 14C ages of the iron standards were compared to the ages by the wet method. The results indicate that contamination by modern carbon is negligible in the system. Furthermore, terrestrial 14C ages of two Antarctic meteorites, Y-75102 and ALH-77294, from the Yamato and Allan Hills ice fields, respectively, were determined. The age of Y-75102 is estimated 4.0 +/1.0 ka, and the age of ALH-77294 is 19.5 +/1.2 ka. The 14C ages on the meteorites roughly agree with the literature value. However, further study is needed in improvement on reducing a background value and of complete fusion of a meteorite in the extraction system.