{"id":6400,"date":"2015-12-16T06:57:43","date_gmt":"2015-12-16T05:57:43","guid":{"rendered":"http:\/\/karmaka.de\/?p=6400"},"modified":"2016-12-21T06:59:28","modified_gmt":"2016-12-21T05:59:28","slug":"stable-chromium-isotopic-composition-of-meteorites-and-metal-silicate-experiments-implications-for-fractionation-during-core-formation","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=6400","title":{"rendered":"Stable chromium isotopic composition of meteorites and metal\u2013silicate experiments: Implications for fractionation during core formation"},"content":{"rendered":"<p>P. Bonnand, H.M. Williams, I.J. Parkinson, B.J. Wood, A.N. Halliday<\/p>\n<p>Earth and Planetary Science Letters<br \/>\nVolume 435, 1 February 2016, Pages 14\u201321<br \/>\ndoi:10.1016\/j.epsl.2015.11.026<\/p>\n<p><a href=\"http:\/\/www.sciencedirect.com\/science\/article\/pii\/S0012821X1500730X\" target=\"_blank\"><strong>LINK (open access)<\/strong><\/a><\/p>\n<p>&#8220;We present new mass independent and mass dependent Cr isotope compositions for meteorites measured by double spike thermal ionisation mass spectrometry. Small differences in both mass independent 53Cr and 54Cr relative to the Bulk Silicate Earth are reported and are very similar to previously published values. Carbonaceous chondrites are characterised by an excess in 54Cr compared to ordinary and enstatite chondrites which make mass independent Cr isotopes a useful tool for distinguishing between meteoritic groups. Mass dependent stable Cr isotope compositions for the same samples are also reported. Carbonaceous and ordinary chondrites are identical within uncertainty with average \u03b453Cr\u03b453Cr values of \u22120.118\u00b10.040\u2030\u22120.118\u00b10.040\u2030 and \u22120.143\u00b10.074\u2030\u22120.143\u00b10.074\u2030 respectively. The heaviest isotope compositions are recorded by an enstatite chondrite and a CO carbonaceous chondrite, both of which have relatively reduced chemical compositions implying some stable Cr isotope fractionation related to redox processes in the circumstellar disk. The average \u03b453Cr\u03b453Cr values for chondrites are within error of the estimate for the Bulk Silicate Earth (BSE) also determined by double spiking. The lack of isotopic difference between chondritic material and the BSE provides evidence that Cr isotopes were not fractionated during core formation on Earth. A series of high-pressure experiments was also carried out to investigate stable Cr isotope fractionation between metal and silicate and no demonstrable fractionation was observed, consistent with our meteorites data. Mass dependent Cr isotope data for achondrites suggest that Cr isotopes are fractionated during magmatic differentiation and therefore further work is required to constrain the Cr isotopic compositions of the mantles of Vesta and Mars.&#8221;<\/p>\n<p><strong>Corrigendum<\/strong><\/p>\n<p>The authors have corrected a few minor mistakes that appear in Table 2, that is, four \u03b554Cr\u03b554Cr values have been updated (JP-1, Bremerv\u00f6rde, Kernouve and Saint-Severin). These minor changes do not affect the figures or the conclusions of the article.<\/p>\n<p>Available online 20 December 2016  Editor: B. Marty<\/p>\n<p><a href=\"http:\/\/www.sciencedirect.com\/science\/article\/pii\/S0012821X1630663X\" target=\"_blank\"><strong>LINK<\/strong><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>P. Bonnand, H.M. Williams, I.J. Parkinson, B.J. Wood, A.N. Halliday Earth and Planetary Science Letters Volume 435, 1 February 2016, Pages 14\u201321 doi:10.1016\/j.epsl.2015.11.026 LINK (open access) &#8220;We present new mass independent and mass dependent Cr&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,922,112,8,7],"tags":[2270,121,462,1810,2268,2003,2269,2271],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/6400"}],"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=6400"}],"version-history":[{"count":3,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/6400\/revisions"}],"predecessor-version":[{"id":11082,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/6400\/revisions\/11082"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6400"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6400"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6400"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}