LINK<\/strong><\/a><\/p>\n\n\n\n“Fine-grained Ca-Al-rich inclusions (FGIs) in CV chondrites are suggested to be condensates from the solar nebular gas and thus captured O-isotopes from the gas. We conducted a combined study of petrographic observations and in situ O-isotope analysis using secondary ion mass spectrometry for an FGI, named HKD01, from the reduced CV chondrite Northwest Africa 8613. HKD01 has an irregular shape and petrographically three-layered structures: a hibonite-rich core, a spinel-rich core, and a mantle. Each petrographic domain contains melilite, hibonite, and spinel with variable proportions of those minerals. The O-isotopic compositions of the constituent minerals plotted along the slope-1 line on an O three-isotope diagram ranged between \u039417O \u223c \u221223\u2030 and 1\u2030. Hibonite and spinel are uniformly 16O-rich (\u039417O = \u221223\u2030) irrespective of their occurrences, while melilite crystals exhibit wide O-isotope variations ranging between \u039417O \u223c \u221223\u2030 and 1\u2030. The O-isotopic composition in a melilite crystal changes abruptly within \u223c2 \u00b5m, indicating that disturbances of O-isotopes in melilite after condensation are less than \u223c2 \u00b5m. Because the melilite in the FGI typically has grain sizes of 5\u221210 \u00b5m, the abrupt change of O-isotopic composition demonstrates that melilite crystals in the FGI preserve the O-isotopic composition of the nebular gas from which they condensed. In the mantle, aggregates of melilite crystals, having relatively large grain sizes (10\u221225 \u00b5m) and oscillatory chemical zoning, exhibit 16O-poor compositions with small variations ranging between \u039417O \u223c \u22124 and 1\u2030. Among them, a large melilite crystal (\u223c20 \u00b5m) with homogeneously 16O-poor composition (\u039417O \u223c 0\u2030) across the single crystal was found. The coexistence of 16O-poor and 16O-rich melilite crystals without O-isotope disturbances in the FGI reveals that 16O-poor (\u039417O \u223c 0\u2030) nebular gas existed in the formation region of the FGI HKD01 in addition to 16O-rich (\u039417O \u223c \u201323\u2030) nebular gas.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Sohei Wada, Noriyuki Kawasaki, Changkun Park, Hisayoshi Yurimoto Geochimica et Cosmochimica ActaIn Press, Journal Pre-proof, Available online 17 August 2020 LINK “Fine-grained Ca-Al-rich inclusions (FGIs) in CV chondrites are suggested to be condensates from the…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9,14,72,71],"tags":[3895,1353,3273,1812,5662,5181,5161,3624],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23297"}],"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=23297"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23297\/revisions"}],"predecessor-version":[{"id":23298,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23297\/revisions\/23298"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=23297"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=23297"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=23297"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}