Accretion of Warm Chondrules in Weakly Metamorphosed Ordinary Chondrites and Their Subsequent Reprocessing
Sponsor
Research was supported by the National Aeronautics and Space Administration (Grant 80NSSC19K0517).
Document Type
Dataset
Publication Date
2024
Abstract
To better understand chondrite accretion and subsequent processes, the textures, crystallography, deformation, and compositions of some chondrite constituents in ten lithologies of different cluster texture strength were studied in seven weakly metamorphosed (Type 3) and variably shocked ordinary chondrites (Ragland—LL3 S1, Tieschitz—H/L3 S1, NWA 5421—LL3 S2, NWA 5205—LL3 S2, NWA 11905—LL3-5 S3, NWA 5781—LL3 S3, NWA 11351—LL3-6 S4) using optical and electron microscopy and microtomography techniques. Results support a four-stage model for chondrite formation. This includes 1) limited annealing following collisions during chondrule crystallization and rapid cooling in space prior to accretion, as evidenced by olivine microstructures consistent with dislocation recovery and diffusion; 2) initial accretion of still-warm chondrules into aggregates at an effective chondrite accretion temperature of ~900- 950 °C with nearly in situ impingement deformation between adjacent chondrules in strongly clustered lithologies (NWA 5781, Tieschitz, NWA 5421, NWA 5205 Lithology A), as evidenced by intragranular lattice distortions in olivine consistent with high-temperature slip systems, and by evidence that some olivine-rich objects in Tieschitz accreted while partly molten; 3) syn- or post-accretion bleaching of chondrule mesostases, which transferred feldspathic chondrule mesostasis to an interchondrule glass deposit found in strongly clustered lithologies, as evidenced by chemical data and textures; and 4) post-bleaching weak or strong shocks that resulted in destruction of interchondrule glass and some combination of brecciation, foliation of metal and sulfide, and melting and shock-overprinting effects, as evidenced by poor cluster textures and presence of clastic texture, alignment of metal and sulfide grains caused by shock compression, presence of impact-generated glass, and changes in olivine slip systems. The data support the model of Metzler (2012), who suggested that chondrules in ordinary chondrites accreted while still warm to form cluster chondrite textures as a “primary accretionary rock” (our Stage 2), and that subsequent brecciation destroyed this texture to create chondrites with weak cluster texture (our Stage 4).
Rights
This work is marked with CC0 1.0 Universal
DOI
10.15760/geology-data.06
Persistent Identifier
https://archives.pdx.edu/ds/psu/40953
Recommended Citation
Ruzicka, Alexander M.; Hugo, Richard C.; Friedrich, Jon M.; and Ream, Michael Tyler, "Accretion of Warm Chondrules in Weakly Metamorphosed Ordinary Chondrites and Their Subsequent Reprocessing Inferred From Electron Backscatter Diffraction (EBSD), Petrographic, and Micro-Tomography Data" (2023). Geology Faculty Datasets. 6. https://doi.org/10.15760/geology-data.06
comma-delimited text file
Description
This data supports an article being published in Geochimica et Cosmochimica Acta.
Data include information about the samples that were studied, crystallographic data, tomography data, chemical data, inferences about the processes that affected each lithology, the types of data products that were acquired, and information about SEM data files.
The file contains eight tables.