Chemical composition and petrography of recent type 1 and 2 carbonaceous chondrite falls

We analysed the recent (2019 - 2021) brecciated carbonaceous chondrite falls Flensburg (C1), Tarda (C2,) Kolang (CM1/2), Aguas Zarcas (CM2), and Winchcombe (CM2) together with Murchison and Paris for their chemical composition using ICP-MS and for Hg abundances using a direct mercury analyser. Chemical variations were evaluated considering new and published petrological and mineralogical data.

Aguas Zarcas #1 is enriched in Hg relative to a CI reference value of 258 ng/g, while Flensburg, Kolang, Winchcombe and the fusion crust-rich samples Aguas Zarcas #3a and 3b are depleted. The Hg contents in Aguas Zarcas #2 and 4 and both Tarda specimens are roughly similar to those extrapolated from plateau volatile element abundances, with a best fit if a CI Hg content of about 210 ng/g is assumed.

For Flensburg, Kolang, Aguas Zarcas #1 and 2, Murchison and Paris, elements analysed by ICP-MS display a typical CM composition, but Tarda shows less depletion of moderately volatile elements. Deviations for Ca, Sr, Ba, Na, Rb, and Cs in the pre-rain samples Aguas Zarcas #3a and 3b suggest that these elements were mobile within the parent body. The metal-rich lithology of Aguas Zarcas #4 displays no systematic enrichment in siderophile elements, but peculiar enrichments of refractory elements, most significantly for Zr, Hf, W, Ir, and some heavy REE. The enrichment of Ca, Sr, Mn, and Mg esp. in Tarda #1 reflects the high abundance of carbonates. Unlike for Tarda and some Aguas Zarcas samples, the Flensburg CM-related composition was not affected by intense aqueous alteration.