LINK<\/strong><\/a><\/p>\n\n\n\n“Ureilites are carbon\u2010rich ultramafic achondrites that have been heated above the silicate solidus, do not contain plagioclase, and represent the melting residues of an unknown planetesimal (i.e., the ureilite parent body, UPB). Melting residues identical to pigeonite\u2010olivine ureilites (representing 80% of ureilites) have been produced in batch melting experiments of chondritic materials not depleted in alkali elements relative to the Sun\u2019s photosphere (e.g., CI, H, LL chondrites), but only in a relatively narrow range of temperature (1120 \u00baC\u20131180 \u00baC). However, many ureilites are thought to have formed at higher temperature (1200 \u00baC\u20131280 \u00baC). New experiments, described in this study, show that pigeonite can persist at higher temperature (up to 1280 \u00baC) when CI and LL chondrites are melted incrementally and while partial melts are progressively extracted. The melt productivity decreases dramatically after the exhaustion of plagioclase with only 5\u20139 wt% melt being generated between 1120 \u00baC and 1280 \u00baC. The relative proportion of pyroxene and olivine in experiments is compared to 12 ureilites, analyzed for this study, together with ureilites described in the literature to constrain the initial Mg\/Si ratio of the UPB (0.98\u20131.05). Experiments are also used to develop a new thermometer based on the partitioning of Cr between olivine and low\u2010Ca pyroxene that is applicable to all ureilites. The equilibration temperature of ureilites increases with decreasing Al2O3 and Wo contents of pyroxene and decreasing bulk REE concentrations. The UPB melted incrementally, at different fO2, and did not cool significantly (0 \u00baC\u201330 \u00baC) prior to its disruption. It remained isotopically heterogenous, but the initial concentration of major elements (SiO2, MgO, CaO, Al2O3, alkali elements) was similar in the different mantle reservoirs.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Max Collinet, Timothy L. Grove Meteoritics & Planetary ScienceFirst Published: 19 April 2020 LINK “Ureilites are carbon\u2010rich ultramafic achondrites that have been heated above the silicate solidus, do not contain plagioclase, and represent the melting…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[28,137,39],"tags":[5515,245,1952],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/21808"}],"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=21808"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/21808\/revisions"}],"predecessor-version":[{"id":21809,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/21808\/revisions\/21809"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21808"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21808"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21808"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}