English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Open

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the zaia usage as premium feature

ZAIA

Zendy Tools

Zendy Plus

Presents the access of premium content as premium feature

Premium Content

The rare CI carbonaceous chondrites are the most aqueously altered andchemically primitive meteorites but due to their porous nature and highabundance of volatile elements are susceptible to terrestrial weathering. TheIvuna meteorite, type specimen for the CI chondrites, is the largesttwentieth-century CI fall and least affected by terrestrial alteration. Themain mass of Ivuna (BM2008 M1) has been stored in a nitrogen atmosphere atleast since 2008 and is the most pristine CI chondrite stone. We report themineralogy, petrography and bulk elemental composition of BM2008 M1 and asecond Ivuna stone (BM1996 M4) stored in air. Both Ivuna stones are brecciasconsisting of multiple rounded, phyllosilicate-rich clasts formed throughaqueous alteration followed by impact processing. A polished thin section ofBM2008 M1 analysed immediately after preparation was found to containsulphate-bearing veins formed when primary sulphides reacted with oxygen andatmospheric water. A section of BM1996 M4 lacked veins but had sulphate grainson the surface recently formed (last 6 years). Differences in the extent ofterrestrial alteration recorded by BM2008 M1 and BM1996 M4 probably reflectvariations in the post-recovery curation history of the stones before enteringthe NHM collection, and indicate that where possible pristine samples ofhydrated carbonaceous should be kept out of the terrestrial environment in astable environment to avoid modification. The bulk elemental composition of thetwo Ivuna stones show some variability due to their heterogeneous nature but ingeneral are similar to previous analyses of CI chondrites. We combine ourelemental abundances with literature values to calculate a new averagecomposition for the Ivuna meteorite, which is in good agreement with existingcompilations of CI chondrites and the most recent solar photosphericabundances.

Terrestrial modification of the Ivuna meteorite and a reassessment of the chemical composition of the CI type specimen