Highlights
\n\u2022 Ureilites have smaller 182W deficits than most magmatic iron meteorites.
\n\u2022 Hf\u2013W model age dates silicate melt extraction at 3.3\u00b10.7 Ma3.3\u00b10.7 Ma after CAI formation.
\n\u2022 This is \u223c2\u20133 Ma later than core formation in most iron meteorite parent bodies.
\n\u2022 Ureilite parent body accreted at \u223c1.6 Ma after CAI formation.
\n\u2022 Ureilite parent body contained too little 26Al to induce complete melting. <\/p>\n
Determining the timescales of the accretion and chemical differentiation of meteorite parent bodies provides some of the most direct constraints on the formation of planetesimals and the earliest stages of planet formation. We present high-precision Hf\u2013W isotope data for a comprehensive set of ureilites, ultramafic mantle restites derived from a partially melted and incompletely differentiated asteroid. All samples are characterized by strong 182W deficits, indicating that silicate melt extraction on the ureilite parent body at 3.3\u00b10.7 Ma3.3\u00b10.7 Ma after CAI formation postdated core formation in iron meteorite parent bodies by \u223c2\u20133 Ma. Thermal modeling of planetesimal heating by 26Al-decay combined with the new Hf\u2013W data indicates that the ureilite parent body accreted at \u223c1.6 Ma after CAI formation and, therefore, more than \u223c1 Ma later than iron meteorite parent bodies, but more than \u223c0.5 Ma earlier that most chondrite parent bodies. Due to its relatively \u2018late\u2019 accretion, the ureilite parent body contained too little 26Al to cause complete melting and, therefore, would have probably remained incompletely differentiated even without exhaustion of 26Al by silicate melt segregation. Our results show that both in terms of degree of differentiation and accretion timescale the ureilite parent body is intermediate between fully differentiated and undifferentiated bodies, implying that there is an inverse correlation between extent of melting and metal\u2013silicate separation versus time of accretion and differentiation.<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
Gerrit Budde, Thomas S. Kruijer, Mario Fischer-G\u00f6dde, Anthony J. Irving, Thorsten Kleine Earth and Planetary Science Letters Volume 430, 15 November 2015, Pages 316\u2013325 LINK<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[75,137,29,39],"tags":[238,1951,462,1950,1949,245,1952],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/5467"}],"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=5467"}],"version-history":[{"count":2,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/5467\/revisions"}],"predecessor-version":[{"id":5469,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/5467\/revisions\/5469"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=5467"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=5467"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=5467"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}