Chemical characteristics of the Yamato-type (CY) carbonaceous chondrites

Ebihara, Mitsuru*; Shirai, Naoki*; Osawa, Takahito  ; Yamaguchi, Akira*

The 15 elements including most major elements of 12 carbonaceous chondrites collected in Antarctica were quantified using neutron-induced prompt gamma-ray analysis. While some of these samples were observed to share affinities with CI or CM chondrites, they do not exhibit the same characteristics as the known CI or CM chondrites. As a result, a new group named "CY" has been proposed for these meteorites. Common among the 12 meteorites is the depletion of volatile elements H and chlorine, showing a correlation and being depleted compared to non-Antarctic CI levels. Based on the abundance of moderately volatile elements Mn and S, the 12 meteorites can be divided into two groups: one with levels similar to non-Antarctic CI and the other with intermediate levels between CI and CM. These results suggest that CY chondrites originate from distinct parent bodies (materials), and considering two different parent bodies (materials) is necessary.