LINK<\/strong><\/a><\/p>\n“Highlights<\/p>\n
\u2022 The CAI USNM 3898 \u2261 ALL, the lowest measured initial 87Sr\/86Sr in the Solar System.
\n\u2022 USNM 3898 does not have (predicted) initial Al26\/27Al\u226b5\u00d710\u22125.
\n\u2022 USNM 3898 has a complex history involving later reheating and melt evaporation,”<\/p>\n
“The Allende CAI USNM3898 is the basis for \u201cALL\u201d, the lowest measured initial 87Sr\/86Sr value in any solar system material including other CAIs (Gray et al., 1973). If the value ALL is correct (debated), then USNM3898 must be 1\u20132 million years older than other CAIs (Podosek et al., 1991). This would require in turn that it have a much higher initial 26Al\/27Al value than other CAIs, on the order of 4 \u00d7 10\u22124. Podosek et al. (1991) showed that this is not the case, with initial 26Al\/27Al = (4.5 \u00b1 0.7) \u00d7 10\u22125, but their Mg-isotopic data had large error bars and there was clear isotopic disturbance in the data having the highest 27Al\/24Mg. Without the latter data, the slope of their isochron is higher (5.10 \u00b1 1.19) \u00d7 10\u22125) and within (large) error of being supracanonical. We used high-precision SIMS to re-determine the initial 26Al\/27Al in this CAI and obtained a value of (5.013 \u00b1 0.099) \u00d7 10\u22125, with an intercept \u03b426Mg\u204e=\u22120.008\u00b10.048\u03b426Mg\u204e=\u22120.008\u00b10.048 and MSWD = 1.3. This value is indistinguishable from that measured in many other CAIs and conclusively shows that USNM3898 is not uniquely ancient. We also confirmed evidence of later isotopic disturbance, similar to what Podosek et al. found, indicating a re-melting and evaporation event some 200,000 years after initial CAI solidification.”<\/p>\n","protected":false},"excerpt":{"rendered":"
G.J. MacPherson, C. Defouilloy, N.T. Kita Earth and Planetary Science Letters Volume 491, 1 June 2018, Pages 238\u2013243 Available online 6 April 2018 LINK “Highlights \u2022 The CAI USNM 3898 \u2261 ALL, the lowest measured…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[66,72,68,57,71],"tags":[448,3389,108,1846,1748,1067,4457],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/14604"}],"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=14604"}],"version-history":[{"count":4,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/14604\/revisions"}],"predecessor-version":[{"id":14608,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/14604\/revisions\/14608"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=14604"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=14604"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=14604"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}