¹Yuki Masuda,²Sota Niki,²Takafumi Hirata,¹Tetsuya Yokoyama
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14190]
¹Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo, Japan
²Geochemical Research Center, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, Japan
Published by arrangement with John Wiley & Sons

Calcium–aluminum-rich inclusions (CAIs) in chondrites are one of the oldest materials in the solar system. Presence of refractory minerals in CAIs suggests that they formed thorough a condensation process from nebular gas of solar composition. In particular, fine-grained CAIs (FGs) have escaped melting after condensation, and thus, the elemental distribution of rare earth elements (REEs) in FG minerals provides key information for elucidating the condensation processes. Although the REE abundances of FG fragments have been investigated in previous studies, the distribution of REEs in individual FG constituent minerals remains poorly explored. Here, we demonstrate the utility of laser imaging of REE distribution in CAIs by analyzing five FGs found in the Allende CV3 chondrite using multiple-spot femtosecond laser ablation (msfsLA)-ICP-MS. The msfsLA-ICP-MS imaging system allows for a rapid acquisition of a wider range of REE distributions than previously achieved by Secondary ion mass spectrometry-based imaging techniques. Out of the five FGs examined in this study, three showed the homogeneous REE patterns, while the other two indicated variable REE patterns within each FG. These observations presumably reflect differences in the chemical processes experienced by the FGs, and indicate that multi-step chemical processes were recorded in some of the FGs. The msfsLA-ICP-MS imaging technique can characterize the elemental distribution of individual FGs under the comparable spatial resolution with high-analysis throughput, and thus, it is an effective new method for advancing the taxonomy of FGs, which will improve our understanding of the physicochemical conditions that prevailed in the early solar system.

¹Andrew F. Parisi,¹Elizabeth J. Catlos,¹Michael E. Brookfield,^2,3Axel K. Schmitt,¹Daniel F. Stöckli,⁴Daniel P. Miggins,¹Daniel S. Campos
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14183]
¹Jackson School of Geosciences, University of Texas at Austin, Center for Planetary Systems Habitability, Austin, Texas, USA
²Institut für Geowissenschaften, Ruprecht-Karls-Universität Heidelberg, Heidelberg, Germany
³John de Laeter Centre, Curtin University, Bentley, Western Australia, Australia
⁴Oregon State University, Oregon State University Argon Geochronology Laboratory, Corvallis, Oregon, USA
Published by arrangement with John Wiley & Sons

The Slate Islands (Ontario) is one of Canada’s larger impact structures at 32 km in diameter and has been linked to the Ordovician meteorite event (OME). We report zircon U–Pb dates from two suevite and two syenite samples collected from the Slate Islands. Plagioclase 40Ar/39Ar dates were also obtained from one of the samples. The plagioclase and most zircon dates record pre-impact ages with links to known tectonic events, including those associated with the assembly of the Superior Craton at approximately 2700 Ma. However, Neoarchean zircon grains appear to be reset at 456.1 ± 6.9 Ma (±2σ) based on the lower intercept of discordia for all dated samples. The date overlaps its previously accepted age of 450 Ma and would be 2–19 million years following the parent asteroid breakup if related to the OME.