{"id":29617,"date":"2021-11-26T17:47:22","date_gmt":"2021-11-26T16:47:22","guid":{"rendered":"https:\/\/karmaka.de\/?p=29617"},"modified":"2021-12-02T07:33:48","modified_gmt":"2021-12-02T06:33:48","slug":"oxygen-and-aluminum-magnesium-isotopic-systematics-of-presolar-nanospinel-grains-from-ci-chondrite-orgueil","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=29617","title":{"rendered":"Oxygen and Aluminum-Magnesium Isotopic Systematics of Presolar Nanospinel Grains from CI Chondrite Orgueil<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"\n<p>Nan Liu, Nicolas Dauphas, Sergio Cristallo, Sara Palmerini, Maurizio Busso<\/p>\n\n\n\n<p>Geochimica et Cosmochimica Acta<br>In Press, Journal Pre-proof, Available online 26 November 2021<\/p>\n\n\n\n<p><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0016703721006773\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK<\/strong><\/a><\/p>\n\n\n\n<p><a rel=\"noreferrer noopener\" href=\"https:\/\/arxiv.org\/ftp\/arxiv\/papers\/2112\/2112.00512.pdf\" target=\"_blank\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<p class=\"justify-text\">&#8220;Presolar oxide grains have been previously divided into several groups (Group 1 to 4) based on their isotopic compositions, which can be tied to several stellar sources. Much of available data was acquired on large grains, which may not be fully representative of the presolar grain population present in meteorites. We present here new O isotopic data for 74 small presolar oxide grains (\u223c200 nm in diameter on average) from Orgueil and Al-Mg isotopic systematics for 25 of the grains. Based on data-model comparisons, we show that (i) Group 1 and Group 2 grains more likely originated in low-mass first-ascent (red giant branch; RGB) and\/or second-ascent (asymptotic giant branch; AGB) red giant stars and (ii) Group 1 grains with (26Al\/27Al)0 \u2a86 5\u00d710\u22123 and Group 2 grains with (26Al\/27Al)0 \u2a85 1\u00d710\u22122 all likely experienced extra circulation processes in their parent low-mass stars but under different conditions, resulting in proton-capture reactions occurring at enhanced temperatures. We do not find any large 25Mg excess in Group 1 oxide grains with large 17O enrichments, which provides evidence that 25Mg is not abundantly produced in low-mass stars. We also find that our samples contain a larger proportion of Group 4 grains than so far suggested in the literature for larger presolar oxide grains (\u2265 400 nm). We also discuss our observations in the light of stellar dust production mechanisms.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Nan Liu, Nicolas Dauphas, Sergio Cristallo, Sara Palmerini, Maurizio Busso Geochimica et Cosmochimica ActaIn Press, Journal Pre-proof, Available online 26 November 2021 LINK PDF (OPEN ACCESS) &#8220;Presolar oxide grains have been previously divided into several&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[65,76],"tags":[2669,2536,125,110,1845,1853,6178],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/29617"}],"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=29617"}],"version-history":[{"count":2,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/29617\/revisions"}],"predecessor-version":[{"id":29669,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/29617\/revisions\/29669"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=29617"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=29617"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=29617"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}