LINK<\/strong><\/a><\/p>\n\n\n\n“Coarse-grained, igneous Ca-Al-rich inclusions (CAIs) in CV chondrites formed through multiple melting events. We conducted in situ O-isotope analysis and Al-Mg systematics by secondary ion mass spectrometry of relict and overgrown minerals from a partial melting event in an Allende Type B CAI, Golfball. Golfball has a Type B CAI bulk composition and a unique structure: a fassaite-rich mantle enclosing a melilite-rich core. Many of the blocky melilite crystals in the core have irregularly shaped, Al-rich (\u00c5k5\u201315) cores enclosed in strongly zoned (\u00c5k30\u201370) overgrowths. Since the Al-rich melilite grains could not have formed from a melt of Golfball, they are interpreted as relict grains that survived later melting events. The O-isotopic compositions of the blocky melilite crystals plot along the carbonaceous chondrite anhydrous mineral line, ranging between \u039417O ~ \u221214\u2030 and \u22125\u2030. The Al-rich relict melilite grains and their overgrowths exhibit the same O-isotopic compositions, while the O-isotopic compositions are varied spatially among melilites. We found that the O-isotopic compositions steeply change across several melilite crystals within few tens of micrometers, indicating the O-isotopic compositions of the melt could not have been homogenized during the partial melting in that scale. According to the time scale of O self-diffusivity in the melt, the cooling rate of the partial melting event is calculated to be >6 \u00d7 104 K h\u22121. Al-Mg isotope data for core minerals plot on a straight line on an Al-Mg evolution diagram. A mineral isochron for Golfball gives initial 26Al\/27Al of (4.42 \u00b1 0.20) \u00d7 10\u20135 and initial \u03b426Mg* of \u22120.035 \u00b1 0.050\u2030. The chemical and O-isotopic compositions of melilite and those initial values imply that its precursor consisted of fluffy Type A and\/or fine-grained CAIs. The partial melting event for Golfball may have occurred in very short order after the precursor formation.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Noriyuki Kawasaki, Shoichi Itoh, Naoya Sakamoto, Steven B. Simon, Daiki Yamamoto, Hisayoshi Yurimoto Meteoritics & Planetary ScienceVersion of Record online: 07 July 2021 LINK “Coarse-grained, igneous Ca-Al-rich inclusions (CAIs) in CV chondrites formed through multiple…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[66,9,14,2531],"tags":[2669,1846,1718,3315,1812,1845,135,727],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28360"}],"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=28360"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28360\/revisions"}],"predecessor-version":[{"id":28361,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28360\/revisions\/28361"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=28360"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=28360"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=28360"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}