LINK<\/strong><\/a><\/p>\n\n\n\n“We report in situ ion-microprobe analyses of Li- and O-isotope compositions for olivine, low-Ca pyroxene, high-Ca pyroxene, and chondrule mesostasis\/plagioclase in nine chondrules from the Allende CV3 chondrite. Based on their mineralogy and O-isotope compositions, we infer that the chondrule mesostasis\/plagioclase and ferroan olivine rims were extensively modified or formed during metasomatic alteration and metamorphism on the Allende parent asteroid. We excluded these minerals in order to determine the correlations between Li and both O and the chemical compositions of olivines and low-Ca pyroxenes in the chondrules and their igneous rims. Based on the O-isotope composition of the olivines, nine chondrules were divided into three groups. Average \u039417O of olivines (Fo>65) in group 1 and 2 chondrules are \u22125.3 \u00b1 0.4 and \u22126.2 \u00b1 0.4\u2030, respectively. Group 3 chondrules are characterized by the presence of 16O-rich relict grains and the \u039417O of their olivines range from \u221223.7 to \u22126.2\u2030. In group 1 olivines, as Fa content increases, variation of \u03b47Li becomes smaller and \u03b47Li approaches the whole-rock value (2.4\u2030; Seitz et al., 2012), suggesting nearly complete Li-isotope equilibration. In group 2 and 3 olivines, variation of \u03b47Li is limited even with a significant range of Fa content. We conclude that Li-isotope compositions of olivine in group 1 chondrules were modified not by an asteroidal process but by an igneous-rim formation process, thus chondrule olivines retained Li-isotope compositions acquired in the protosolar nebula. In olivines of the group 3 chondrule PO-8, we observed a correlation between O and Li isotopes: In relict 16O-rich olivine grains with \u039417O of \u223c \u2212 25 to \u221220\u2030, \u03b47Li ranges from \u221223 to \u22123\u2030; in olivine grains with \u039417O > \u221220\u2030, \u03b47Li is nearly constant (\u22128\u00b14\u2030). Based on the Li-isotope composition of low-Ca pyroxenes, which formed from melt during the crystallization of host chondrules and igneous rims, the existence of a gaseous reservoir with a \u03b47Li \u223c \u221211\u2030 is inferred.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Tak Kunihiro, Tsutomu Ota, Eizo Nakamura Geochimica et Cosmochimica Acta In Press, Accepted Manuscript, Available online 6 March 2019 LINK “We report in situ ion-microprobe analyses of Li- and O-isotope compositions for olivine, low-Ca pyroxene,…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[55,56],"tags":[108,3273,1839,1812],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/18110"}],"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=18110"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/18110\/revisions"}],"predecessor-version":[{"id":18111,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/18110\/revisions\/18111"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=18110"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=18110"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=18110"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}