{"id":417,"date":"2012-05-30T22:51:56","date_gmt":"2012-05-30T20:51:56","guid":{"rendered":"http:\/\/karmaka.de\/?p=417"},"modified":"2014-10-22T16:54:54","modified_gmt":"2014-10-22T14:54:54","slug":"uranium-isotope-compositions-of-the-basaltic-angrite-meteorites-and-the-chronological-implications-for-the-early-solar-system","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=417","title":{"rendered":"Uranium isotope compositions of the basaltic angrite meteorites and the chronological implications for the early Solar System"},"content":{"rendered":"<p>Gregory A. Brennecka and Meenakshi Wadhwa<\/p>\n<p>NAS 2012 109 (24) 9299-9303; published ahead of print May 30, 2012, doi:10.1073\/pnas.1114043109<\/p>\n<p><a href=\"http:\/\/www.pnas.org\/content\/109\/24\/9299.full.pdf+html?sid=3d373bdd-7ea1-4376-a087-94ea295e12e7\" target=\"_blank\"><strong>PDF LINK<\/strong><\/a><\/p>\n<p><a href=\"http:\/\/www.pnas.org\/content\/suppl\/2012\/05\/30\/1114043109.DCSupplemental\/pnas.1114043109_SI.pdf\" target=\"_blank\"><strong>LINK (Supporting Information)<\/strong><\/a><\/p>\n<p><a href=\"http:\/\/www.pnas.org\/content\/109\/26\/10239.abstract?sid=3d373bdd-7ea1-4376-a087-94ea295e12e7\" target=\"_blank\"><strong>LINK (abstract)<\/strong><\/a><\/p>\n<blockquote>\n<div id=\"abstract-1\" class=\"section abstract\">\n<h2><span style=\"font-size: 10pt;\">Abstract<\/span><\/h2>\n<p id=\"p-3\">Events occurring within the first 10 million years of the Solar System\u2019s approximately 4.5 billion-year history, such as formation of the first solids, accretion, and differentiation of protoplanetary bodies, have determined the evolutionary course of our Solar System and the planetary bodies within it. The application of high-resolution chronometers based on short-lived radionuclides is critical to our understanding of the temporal sequence of these critical events. However, to map the relative ages from such chronometers onto the absolute time scale, they must be \u201canchored\u201d to absolute ages of appropriate meteoritic materials using the high-precision lead\u2013lead (Pb\u2013Pb) chronometer. Previously reported Pb\u2013Pb dates of the basaltic angrite <span class=\"search-term-highlight\">meteorite<\/span>s, some of which have been used extensively as time anchors, assumed a constant <sup>238<\/sup>U\/<sup>235<\/sup>U ratio (= 137.88). In this work, we report measurements of <sup>238<\/sup>U\/<sup>235<\/sup>U ratios in several angrites that are distinct from the previously assumed value, resulting in corrections to the Pb\u2013Pb ages of \u22651 million years. There is no resolvable variation in the <sup>238<\/sup>U\/<sup>235<\/sup>U ratio among the angrite bulk samples or mineral separates, suggesting homogeneity in the U isotopic composition of the angrite parent body. Based on these measurements, we recalculated the Pb\u2013Pb age for the commonly used anchor, the D\u2019Orbigny angrite, to be 4563.37 \u00b1 0.25 Ma. An adjustment to the Pb\u2013Pb age of a time anchor (such as D\u2019Orbigny) requires a corresponding correction to the \u201cmodel ages\u201d of all materials dated using that anchor and a short-lived chronometer. This, in turn, has consequences for accurately defining the absolute timeline of early Solar System events.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Gregory A. Brennecka and Meenakshi Wadhwa NAS 2012 109 (24) 9299-9303; published ahead of print May 30, 2012, doi:10.1073\/pnas.1114043109 PDF LINK LINK (Supporting Information) LINK (abstract) Abstract Events occurring within the first 10 million years&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[37,72,68,71],"tags":[237,132],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/417"}],"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=417"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/417\/revisions"}],"predecessor-version":[{"id":418,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/417\/revisions\/418"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=417"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=417"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=417"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}