LINK<\/strong><\/a><\/p>\n\n\n\n“Disagreement regarding the origin of the bulk silicate Earth\u2019s (BSE) superchondritic carbon\/nitrogen (C\/N) ratio is due, in part, to the unknown C\/N ratios of differentiated planetesimals \u2212 the building blocks of Earth-like rocky planets. In this study we report solid-liquid metal partitioning experiments for C and N that allow us to reconstruct, from the C and N contents of iron meteorites, the C\/N ratios of the cores of the earliest formed planetesimals. Due to their siderophile character, most of the C and N retained in these bodies after differentiation resides in their cores. Therefore, estimates of the bulk C and N contents and C\/N ratios of the cores yield confident estimates of these quantities in the complete parent bodies of iron meteorites. Our experimental data, at 1 GPa and 1200-1400 \u00b0C, show that C and N are incompatible in solid metal relative to S-poor liquids but compatible in solid metal relative to S-rich liquids. Crucially, N is approximately an order of magnitude more compatible than C in S-rich systems. S itself is incompatible in solid metal and so the late-crystallizing liquids persisting at the end of core freezing were S-rich for most cores. Although these late-crystallizing liquids are unsampled by iron meteorites, we infer that their N contents and C\/N ratios were generally lower and higher, respectively, than those in iron meteorites. Depending upon the fraction of unsampled late-crystallizing liquids as well as their S contents, the C\/N ratios of the bulk cores and complete parent bodies are either similar to or higher than those measured in iron meteorites. The reconstructed C\/N ratios of most of the parent bodies of iron meteorites are chondritic, except that the volatile-rich IC and IIC groups have superchondritic C\/N ratios. Importantly, the C\/N ratio of the parent body of the IC iron meteorite group lies within the estimated range of the BSE, whereas the C\/N ratios of all other groups are distinctly lower. Correlated depletion of moderately volatile elements like Ge and Ga with C and N, variations in metallographic cooling rates, and Pd-Ag isotope systematics suggest that the parent cores of the volatile-depleted iron meteorite groups were likely affected by volatile degassing. If volatile-rich iron meteorites like the IC group better capture the C and N inventories of the parent cores of the earliest formed planetesimals, then delivery of C and N via such planetesimals makes the superchondritic C\/N ratio of the BSE a natural consequence of the Earth\u2019s accretion history. Otherwise, poorly constrained processes like atmospheric erosion or C and N delivery by exotic materials are required to explain the superchondritic C\/N ratio of the BSE.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Damanveer S. Grewal, Paul D. Asimow Geochimica et Cosmochimica ActaAvailable online 20 January 2023 LINK “Disagreement regarding the origin of the bulk silicate Earth\u2019s (BSE) superchondritic carbon\/nitrogen (C\/N) ratio is due, in part, to the…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[214,73],"tags":[4819,4817,587,3944,1874,4515,654,239,695,257],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/32136"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=32136"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/32136\/revisions"}],"predecessor-version":[{"id":32137,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/32136\/revisions\/32137"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=32136"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=32136"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=32136"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}