Neodymium, strontium and chromium isotopic studies of the LEW86010 and Angra dos Reis meteorites and the chronology of the angrite parent body

摘要: Neodymium, stontium, and chromium isotopic studies of the LEW86010 angrite established its absolute age formation interval between crystallization condensation Allende CAIs from solar nebula. Pyroxene phosphate were found to contain approximately 8% Sm Nd inventory. A conventional Sm-147-Nd-143 isochron yielded an 4.53 +/- 0.04 Ga (2 sigma Epsilon(sub sup 143)) = 0.45 1.1. An Sm-146-Nd-142 gives initial Sm-146/Sm-144 0.0076 0.0009 Epsilon (sub 142) -2.5 0.4. The Rb-Sr analyses give Sr-87/Sr-86 Iota(sub Sr 87) 0.698972 8 0.698970 18 for LEW ADOR, respectively, relative 0.71025 NBS987. difference, Delta Sup 87), Iota sr angrites literature values CAIs, corresponds Ma growth in a nebula with CI chondrite value Rb-87/Sr-86 0.91, or 5 photospheric 1.51. Excess Cr-53 extinct Mn-53(t(sub 1/2) 3.7 Ma)in Mn-53/Mn-55 4.4 1.0 x 10(exp -5) inclusions as previously reported by Paris group (Birck Allegre, 1988). system (Sm-146/Sm-144) 0.0080 after Allende, difference Pb-Pb ages 0.0086 crystallation using Mn-Cr interval. data are discussed context model which undifferentiated 'chondritic' parent body formed subsequently underwent differentiation accompanied loss volatiles. Parent bodies Rb/Sr similar that CI, CM, CO chondrites could satisfy Cr systematics. If had CV meteorites, it would have form slightly later, 2.6 CR