LINK<\/strong><\/a><\/p>\n“Highlights
\n\u2022 Multi-isotopic (K\u2013Ca and Rb\u2013Sr) studies on clasts from the Y-74442 and Bhola LL-breccias were carried out.
\n\u2022 The Y-74442 clasts yield the K\u2013Ca age of image with the initial 40Ca\/44Ca = 47.1618 \u00b1 0.0032.
\n\u2022 The Rb\u2013Sr isotope system yields the age of image with the initial 87Sr\/86Sr = 0.7203 \u00b1 0.0044.
\n\u2022 The source material of Y-74442 clasts could be characterized by K\/Ca = 0.43, Rb\/Sr = 3.45 and K\/Rb \u223c 170.”<\/p>\n
“New K\u2013Ca and Rb\u2013Sr isotopic analyses have been performed on alkali-rich igneous rock fragments in the Yamato (Y)-74442 and Bhola LL-chondritic breccias to better understand the extent and timing of alkali enrichments in the early solar system. The Y-74442 fragments yield a K\u2013Ca age of 4.41\u00b10.28 Ga4.41\u00b10.28 Ga for \u03bb(40K) = 0.5543 Ga\u22121 with an initial 40Ca\/44Ca ratio of 47.1618\u00b10.003247.1618\u00b10.0032. Studying the same fragments with the Rb\u2013Sr isotope system yields an age of 4.420\u00b10.031 Ga4.420\u00b10.031 Ga for \u03bb(87Rb) = 0.01402 Ga\u22121 with an initial ratio of 87Sr\/86Sr = 0.7203 \u00b1 0.0044. An igneous rock fragment contained in Bhola shows a similar alkali fractionation pattern to those of Y-74442 fragments but does not plot on the K\u2013Ca or Rb\u2013Sr isochron of the Y-74442 fragments. Calcium isotopic compositions of whole-rock samples of angrite and chondrites are primordial, indistinguishable from mantle-derived terrestrial rocks, and here considered to represent the initial composition of bulk silicate Earth. The initial \u03b540Ca value determined for the source of the alkali clasts in Y-74442 that is \u223c0.5 \u03b5-units higher than the solar system value implies an early alkali enrichment.<\/p>\n
Multi-isotopic studies on these alkali-rich fragments reveal that the source material of Y-74442 fragments had elemental ratios of K\/Ca = 0.43 \u00b1 0.18, Rb\/Sr = 3.45 \u00b1 0.66 and K\/Rb \u223c 170, that may have formed from mixtures of an alkali-rich component (possibly an alkali-enriched gaseous reservoir produced by fractionation of early nebular condensates) and chondritic components that were flash-heated during an impact event on the LL-chondrite parent body \u223c4.42 Ga ago. Further enrichments of potassium and rubidium relative to calcium and strontium as well as a mutual alkali-fractionation (K\/Rb \u223c 50 and heavier alkali-enrichment) would have likely occurred during subsequent cooling and differentiation of this melt. Alkali fragments in Bhola might have undergone similar solid\u2013vapor fractionation processes to those of Y-74442 fragments but appear to have formed via a distinct impact melting event.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Tatsunori Yokoyama, Keiji Misawa, Osamu Okano, Chi-Yu Shih, Laurence E. Nyquist, Justin I. Simon, Michael J. Tappa, Shigekazu Yoneda Earth and Planetary Science Letters In Press, Corrected Proof, Available online 11 November 2016 LINK “Highlights…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[72,24,7,71],"tags":[3390,3389,3391,3382,3384,3388,1816,1807,3385,286,3387,3386,3383],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/10450"}],"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=10450"}],"version-history":[{"count":4,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/10450\/revisions"}],"predecessor-version":[{"id":10454,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/10450\/revisions\/10454"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10450"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10450"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10450"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}