Meteorites are frequently not the pristine record of early solar system processes that we would like them to be. Many unique meteorites, samples that can further our understanding of the environment of the early solar system, are finds, so a knowledge of terrestrial weathering becomes a requirement to accurately interpret their preterrestrial history. This chapter outlines the weathering proces...

Introduction: Short-lived radionuclides were synthesized either by irradiation with energetic particles or by stellar nucleosynthesis. The recent discovery in CAIs from carbonaceous chondrites of evidence for live 10 Be [1], which is only produced by energetic-particle irradiation , has led to suggestions that the major portion of many short-lived radionuclides (was produced by irradiation. How...

Introduction: In our series of experiments to determine the noble gases of phase Q in various classes of meteorites [1,2] we analysed the HF/HCl-resistant residue of an enstatite chondrite [3]. We have chosen the EH5 chondrite St. Mark’s because of its short cosmic-ray exposure age (~1Ma [4]) which is essential to reliably determine the He-Q and Ne-Q isotopic composition. E-chondrites might hav...

Using a synthesized fayalite (Fe2SiO4) standard for improved 53Mn-53Cr radiometric age dating, Patricia Doyle (previously at the University of Hawai‘i and now at the University of Cape Town, South Africa) and coauthors from Hawai‘i, the National Astronomical Observatory of Japan, University of Chicago, and Lawrence Livermore National Laboratory in California, analyzed aqueously formed fayalite ...

CLUES FROM Os, W AND Cr ISOTOPES. G. Quitté, E. Robin, F. Capmas, S. Levasseur, R. Rocchia, J. L. Birck and C. J. Allègre, Laboratoire de Géochimie et Cosmochimie, IPGP, 4 Place Jussieu, Paris, France, CEA/CNRS – UMR1572, Laboratoire des Sciences du Climat et de l’Environnement, Avenue de la Terrasse, Gifsur-Yvette, France, 3 Department of Earth Sciences, ETH Zentrum, Sonneggstrasse 5, Zürich, ...

We measured O-isotopic compositions of equilibrated ordinary chondrites (EOCs) using the CO 2 laser-BrF 5 fluorination technique at Korea Polar Research Institute. Fifty one EOC falls from UCLA collections were selected for this study. About 30-50 mg from each chondrite was gently crushed using agate mortar and pestle. About 2 mm-size fragment each was used to make polished thick sections. We o...

Ion-microprobe studies yield DO (5dO 2 0.52 z dO) values in magnetite from the Rumurti chondrite (RC) PCA91241 (which is paired with PCA91002) of 13.1 to 13.9‰, slightly higher than that in O from whole-rock R samples. Despite DO values in whole-rock RCs that are much (by ca. 1.6‰) higher than in whole-rock LL chondrites, the DO in R magnetite is much lower (by ca. 2‰) than the values (14 to 17...

We report O-, Al-Mg-, K-, Ca-, and Ti-isotopic data for a total of 96 presolar oxide grains found in residues of several unequilibrated ordinary chondrite meteorites. Identified grain types include Al2O3, MgAl2O4, hibonite (CaAl12O19), and Ti oxide. This work greatly increases the presolar hibonite database, and is the first report of presolar Ti oxide. O-isotopic compositions of the grains spa...

Introduction: The Mn-Cr analyses of several H chondrites including Forest Vale, Dimmitt, Ste Mar-guerite and Richardton [1-3], have all shown reasonable agreement between the obtained 'Mn-Cr ages' and the known Pb-Pb ages determined on phosphates. These studies imply that the best fit lines in the 53 Mn-53 Cr evolution plots for these meteorites are isochrons rather than mixing lines and that t...

Introduction: The detailed study of individual lunar soil grains provides evidence that the major optical properties of the lunar surface are primarily related to the production of fine-grained (< 20 nm, super-paramagnetic) Fe-particles in agglutinitic impact melts and to iron-rich vapor deposits on the surfaces of individual grains [1]. These Fe-rich materials are derived from oxidized species...