Testing an integrated chronology: I‐Xe analysis of enstatite meteorites and a eucrite

Abstract— We have determined initial ¹²⁹I/¹²⁷I ratios for mineral concentrates of four enstatite meteorites and a eucrite. In the case of the enstatite meteorites the inferred ages are associated with the pyroxene‐rich separates giving pyroxene closure ages relative to the Shallowater standard of Indarch (EH4, 0.04 ± 0.67 Ma), Khairpur (EL6, ?4.22 ± 0.67 Ma), Khor Temiki (aubrite, ?0.06 Ma), and Itqiy (enstatite achondrite, ?2.6 ± 2.6 Ma), negative ages indicate closure after Shallowater. No separate from the cumulate eucrite Asuka (A?) 881394 yielded a consistent ratio, though excess ¹²⁹Xe was observed in a feldspar separate, suggesting disturbance by thermal metamorphism within 25 Ma of closure in Shallowater. Iodine‐129 ages are mapped to the absolute Pb‐Pb time scale using the calibration proposed by Gilmour et al. (2006) who place the closure age of Shallowater at 4563.3 ± 0.4 Ma. Comparison of the combined ¹²⁹I‐Pb data with associated ⁵³Mn ages, for objects that have been dated by both systems, indicates that all three chronometers evolved concordantly in the early solar system. The enstatite chondrites are offset from the linear array described by asteroid‐belt objects when ⁵³Mn ages are plotted against combined ¹²⁹I‐Pb data, supporting the suggestion that ⁵³Mn was radially heterogeneous in the early solar system.