SIMS analyses of Mg, Cr, and Ni isotopes in primitive meteorites and short-lived radionuclides in the early solar system

SIMSanalyses of 26Al–26Mg, 60Fe–60Ni, and 53Mn–53Cr systems in unequilibrated enstatite chondrites provide evidence for the former existence of 26Al, 60Fe, and 53Mn in this highly reduced meteorite group, suggesting the widespread of these short-lived radionuclides in the early solar system. Calcium–aluminum-rich inclusions and Al-rich chondrules in enstatite chondrites show 26Al–26Mg characteristics similar to their counterparts in other types of chondrites. Assuming its homogenous distribution, finescale 26Al relative chronology can be obtained for differentcomponents inmeteorites.Well-defined isochrons yield initial 60Fe/56Fe ratios of ð0:3 1Þ 10 6 in sulfides from enstatite chondrites. The former presence of 60Fe suggests a stellar source and its possible high abundance points to a supernova origin. 26Al and 60Fe could be important heat sources for the early planetary processes. The large variations of initial 60Fe/56Fe and 53Mn/55Mn ratios and the discordance between 60Fe–60Ni and 53Mn–53Cr systems observed in sulfides indicate later disturbance of the two isotopic systems, and therefore, bear no strict chronological significance. SIMS isotopic analysis can be utilized to attain important information about the early evolution of the solar system. # 2004 Elsevier B.V. All rights reserved