UThPb systematics of the eucrite “Juvinas”: Precise age determination and evidence for exotic lead

Abstract

The U-Th-Pb isotope systematics of the eucrite “Juvinas” have been studied in whole rock fragments as well as in plagioclases and pyroxenes. The results show that this monomict breccia crystallized with a very high U Pb initial ratio at T = 4.539 ± 0.004 AE ago. There is evidence for a less radiogenic Pb component ( 206Pb 204Pb = 13.0 ; 207Pb 204Pb = 13.5 ; 208Pb 204Pb = 32.71 ) interpreted as “exotic lead” induced by a meteoritical impact at the surface of the Juvinas parent body, 1.92 ± 0.06 AE ago.