Chemical characterization of earth's most ancient clastic metasediments from the Isua Greenstone Belt, southern West Greenland

Some of the IGB metasediments have yielded anomalous 142Nd and 182W isotopic compositions that were respectively interpreted in terms of early mantle differentiation processes and the presence of a meteorite component. Alternatively, W and possibly Nd isotopes could have been affected by thermal neutron capture on the Hadean surface. The latter process was tested in this study by analysis of Sm isotope compositions, which serve as an effective monitor for neutron capture effects. As no anomalous variation from terrestrial values was detected, we infer that isotope systematics (including 182W and 142Nd) of IGB metasediments were not affected by neutron capture, but reflect decay of radioactive parent isotopes.