Tafassasset is a primitive meteorite, the origin of which is still debated. Its possible relationship to either the CR chondrites \u2013 considered among the most primitive meteorites \u2013 or the brachinites \u2013 complex primitive achondrites \u2013 makes it an interesting sample for studying the initial stages of planetary accretion and differentiation in the early solar system. Here, we report tungsten (W) isotope data for bulk rock samples as well as for mineral fractions from Tafassasset, along with micro-computed tomography of a piece of the meteorite. Silicates show mass-independent W isotope anomalies, while the metal phase does not. These nucleosynthetic anomalies are interpreted as reflecting the presence of SiC presolar grains in the matrix of the meteorite, carrying s-process184W. After correction of the nucleosynthetic anomalies, a correlation is observed between the 182W\/184W isotope compositions and the Hf\/W ratios of the different fractions. A 182Hf\u2013182W age of ca. 2.9 Ma after CAIs is inferred from the 182Hf\u2013182W chronometer, slightly older than other estimates based on the 53Mn\u201353Cr, 26Al\u201326Mg, and Pb\/Pb chronometers, but consistent with the difference in closure temperatures of the different isotopic systems. Numerical modeling of the thermal evolution of Tafassasset indicates accretion of a parent-body less than \u223c50 km in diameter, \u22641 Ma after the formation of CAIs, at a time when short-lived radio-nuclides induced metal\u2013silicate separation and partial melting of the silicates with extraction of a basaltic component. According to our new data, Tafassasset may represent an inner part of a CR-like parent body, with a differentiation history similar to, but less severe than, that of brachinites.<\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
Thomas Breton, Ghylaine Quitt\u00e9, Michael J. Toplis, Marc Monnereau, Jean-Louis Birck, Christa G\u00f6pel, Cyril Charles Earth and Planetary Science Letters Volume 425, 1 September 2015, Pages 193\u2013203 LINK<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[40,12,79,127],"tags":[852,670,1810,1572,1043],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/4938"}],"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=4938"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/4938\/revisions"}],"predecessor-version":[{"id":4939,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/4938\/revisions\/4939"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4938"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4938"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4938"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}