LINK<\/strong><\/a><\/p>\n“Highlights<\/p>\n
\u2022 Pyroxene in most igneous CAIs becomes 16O-enriched during crystallization.
\n\u2022 O isotopes in type A, type B and FUN CAIs are consistent with spinel dissolution.
\n\u2022 CAIs behaved as closed-system with regard to O during cooling.
\n\u2022 16O-depletion of CAI melts is related with melilite partial melting\/crystallization.”<\/p>\n
“In several Calcium\u2013Aluminum-rich Inclusions (CAIs) from the CV3 chondrites Allende and Efremovka, representative of the most common igneous CAI types (type A, type B and Fractionated with Unknown Nuclear isotopic anomalies, FUN), the relationship between 16O-excesses and TiO2 content in pyroxene indicates that the latter commonly begins to crystallize with a near-terrestrial 16O-poor composition and becomes 16O-enriched during crystallization, reaching a near-solar composition. Mass balance calculations were performed to investigate the contribution of spinel to this 16O-enrichment. It is found that a back-reaction of early-crystallized 16O-rich spinel with a silicate partial melt having undergone a 16O-depletion is consistent with the O isotopic evolution of CAI minerals during magmatic crystallization. Dissolution of spinel explains the O isotopic composition (16O-excess and extent of mass fractionation) of pyroxene as well as that of primary anorthite\/dmisteinbergite and possibly that of the last melilite crystallizing immediately before pyroxene. It requires that igneous CAIs behaved as closed-systems relative to oxygen from nebular gas during a significant fraction of their cooling history, contrary to the common assumption that CAI partial melts constantly equilibrated with gas. The mineralogical control on O isotopes in igneous CAIs is thus simply explained by a single 16O-depletion during magmatic crystallization. This 16O-depletion occurred in an early stage of the thermal history, after the crystallization of spinel, i.e. in the temperature range for melilite crystallization\/partial melting and did not require multiple, complex or late isotope exchange. More experimental work is however required to deduce the protoplanetary disk conditions associated with this 16O-depletion.”<\/p>\n","protected":false},"excerpt":{"rendered":"
J\u00e9r\u00f4me Al\u00e9on Earth and Planetary Science Letters Volume 482, 15 January 2018, Pages 324\u2013333 LINK “Highlights \u2022 Pyroxene in most igneous CAIs becomes 16O-enriched during crystallization. \u2022 O isotopes in type A, type B and…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[66,14,3064,65,2531,2532],"tags":[395,4292,108,1846,687],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/13930"}],"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=13930"}],"version-history":[{"count":2,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/13930\/revisions"}],"predecessor-version":[{"id":13932,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/13930\/revisions\/13932"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=13930"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=13930"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=13930"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}