Rayleigh distillation models are developed to describe theoretical growth zoning of Lu, Hf, Rb, Sr, Sm, and Nd in typical garnet crystals from metapelites and metabasites. Effects of diffusion-limited transport within the matrix and intracrystalline diffusion are also considered qualitatively. Theoretical zoning profiles show strong depletions of Lu in garnet rims compared to cores, but virtual...

Four crustal xenoliths from Scotland have been dissected in order to evaluate the effects of magma-xenolith interaction on Rb-Sr and Sm-Nd isotopic systematics, and hence the use of the xenoliths for accurate determination of source compositions. Each xenolith was sampled from the edge to the center, The Nd isotopic compositions are virtually uniform across each xenolith; however, there are sig...

Introduction: Many lunar samples record some degree of disturbance to their U-Pb isotopic systematics [e.g., 1,2]. This disturbance may be reflected in Pb-Pb, U-Pb, U-Pb, or concordia ages that are discordant among the U-Pb systems as well as with more robust Sm-Nd and Rb-Sr ages. Both mare basalt 10017 and norite 78238 fail to yield consistent geochronologic results among their Pb-Pb, U-Pb, an...

The results of our combined U–Pb, Rb–Sr, and Sm–Nd isotope study of mare basalt 10017 contribute to the understanding of the petrogenetic processes involved in the origin of geochemical diversity in lunar mare basalt sources, as well as the U–Pb isotope systematics of the Moon. The Rb–Sr, Sm–Nd, and U–Pb isotope systems yield concordant crystallization ages of 3.633 ± 0.057 Ga, 3.678 ± 0.069 Ga...

The assumptions of conventional whole-rock and mineral isochron radioisotope dating were tested using a suite of radioisotopes from two Precambrian rocks. Amphibolite from the Beartooth Mountains of Wyoming shows evidence of thorough metamorphism by isochemical processes from andesite by an early Precambrian magma-intrusion event. A diabase sill, exposed within the wall of Grand Canyon at Bass ...

New Rb-Sr, (146,147)Sm-(142,143)Nd and Lu-Hf isotopic analyses of Mg-suite lunar crustal rocks 67667, 76335, 77215 and 78238, including an internal isochron for norite 77215, were undertaken to better define the time and duration of lunar crust formation and the history of the source materials of the Mg-suite. Isochron ages determined in this study for 77215 are: Rb-Sr=4450±270 Ma, (147)Sm-(143...

Lunar Mg-suite norite 78238 was dated using the Sm–Nd, Rb–Sr, and U–Pb isotopic systems in order to constrain the age of lunar magma ocean solidification and the beginning of Mg-suite magmatism, as well as to provide a direct comparison between the three isotopic systems. The Sm–Nd isotopic system yields a crystallization age for 78238 of 4334 ± 37 Ma and an initial e Nd value of 0.27 ± 0.74. T...

Introduction: The crystallization age of Zagami has been well established by the Rb-Sr and Sm-Nd isochron techniques. Isotopic analysis on purified mineral fractions yield Rb-Sr ages of 178±3, 174±14, and 163±19 Ma [1-2], and a Sm-Nd age of 163±7 Ma [2]. Whole rock and leachate pairs have also been analyzed for U-Th-Pb isotopes and yield a Th-Pb age of 230±5 Ma and a U-Pb age of 229±8 Ma [3]. C...