LINK<\/strong><\/a><\/p>\n\n\n\n“Enstatite achondrites (including aubrites) are the only differentiated meteorites that have similar isotope compositions to the Earth-Moon system for most of the elements. However, the origin and differentiation of enstatite achondrites and their parent bodies remain poorly understood. Here, we report high-precision mass-independent and mass-dependent Cr isotope data for 10 enstatite achondrites, including eight aubrites, Itqiy and one enstatite-rich clast in Almahatta Sitta, to further constrain the origin and evolution of their parent bodies. The \u03b554Cr (per 10,000 deviation of the mass bias corrected 54Cr\/52Cr ratio from a terrestrial standard) systematics define three groups: main-group aubrites with \u03b554Cr = 0.06 \u00b1 0.12 (2SD, N =7) that is similar to the enstatite chondrites and the Earth-Moon system, Shallowater aubrite with \u03b554Cr = -0.12 \u00b1 0.04 and Itqiy-type meteorites with \u03b554Cr = -0.26 \u00b1 0.03 (2SD, N =2). This shows that there were at least three enstatite achondrite parent bodies in the Solar System. This is confirmed by their distinguished mass-dependent Cr isotope compositions (\u03b453Cr values): 0.24 \u00b1 0.03 \u2030, 0.10 \u00b1 0.03 \u2030 and -0.03\u00b1 0.03 \u2030 for main-group, Shallowater and Itqiy parent bodies, respectively. Aubrites are isotopically heavier than chondrites (\u03b453Cr =-0.12 \u00b1 0.04 \u2030), which likely results from the formation of an isotopically light sulfur-rich core. We also obtained the abundance of the radiogenic 53Cr (produced by the radioactive decay of 53Mn, T1\/2= 3.7 million years). The radiogenic \u03b553Cr excesses correlate with the 55Mn\/52Cr ratios for aubrites (except Shallowater and Bustee) and also the Cr stable isotope compositions (\u03b453Cr values). We show that these correlations represent mixing lines that also hold chronological significance since they are controlled by the crystallization of sulfides and silicates, which mostly reflect the main-group aubrite parent body differentiation at 4562.5 \u00b1 1.1 Ma (i.e., 4.8 \u00b1 1.1 Ma after Solar System formation). Furthermore, the intercept of these lines with the ordinate axis which represent the initial \u03b553Cr value of main-group aubrites (0.50 \u00b1 0.16, 2\u03c3) is much higher than the average \u03b553Cr value of enstatite chondrites (0.15 \u00b1 0.10, 2SD), suggesting an early sulfur-rich core formation that effectively increased the Mn\/Cr ratio of the silicate fraction of the main-group aubrite parent body.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Ke Zhu (\u6731\u67ef), Fr\u00e9d\u00e9ric Moynier, Martin Schiller, Harry Becker, Jean-Alix Barrat,Martin Bizzarro Geochimica et Cosmochimica ActaIn Press, Journal Pre-proof, Available online 8 June 2021 LINK “Enstatite achondrites (including aubrites) are the only differentiated meteorites that…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,17,137],"tags":[3514,1826,462,1813,4265],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28000"}],"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=28000"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28000\/revisions"}],"predecessor-version":[{"id":28001,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28000\/revisions\/28001"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=28000"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=28000"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=28000"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}