LINK<\/strong><\/a><\/p>\n\n\n\n“New \u03b413C and \u03b418O values were measured to constrain the formation mechanisms of two previously identified generations (Antarctica and Houston) of terrestrial weathering carbonates, nesquehonite, which formed on the surface of the Lewis Cliff 85320 ordinary chondrite. These two nesquehonite generations exhibit a characteristic carbon and oxygen isotopic trend which starts with a linear \u03b413C\u2010\u03b418O covariation followed by a continuous increase in \u03b418O with little to no change in \u03b413C. Based on the newly developed nesquehonite\u2010water oxygen isotope thermometry and the measured \u03b418O value of melted ice from Antarctica, the formation temperature of the Antarctic nesquehonite generation was estimated to be \u22121.9 \u00b1 3 \u00b0C. Houston nesquehonite generation was most likely formed from an evaporative residue of the melted Antarctic ice at 30 \u00b1 4 \u00b0C. Modeling the isotopic trend of the two generations suggests that evaporation created large \u03b418O variations in the nesquehonite while carbon isotopes were stabilized by exchange between the parent liquid and atmospheric CO2. Thus, we suggest that carbonates formed by terrestrial weathering in Antarctica should possess a wide spread in \u03b418O values and a narrow range in \u03b413C values under dry and cold conditions. Finally, the observed wide spread of \u03b418O in Martian carbonates (e.g., Allan Hills 84001 and Nakhla) can be explained by evaporation near 0 \u00b0C and may have formed by a similar mechanism to that of the nesquehonite in the LEW 85320. Meanwhile, the wide spread of \u03b413C suggests that two carbon reservoirs with distinct isotope compositions on Mars (e.g., the atmospheric carbon and magmatic carbon) may be actively participating in the formation process.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Mohammed I. El\u2010Shenawy, Paul B. Niles, Doug W. Ming, Rick Socki, Kevin Righter Meteoritics & Planetary ScienceFirst Published: 26 September 2020 LINK “New \u03b413C and \u03b418O values were measured to constrain the formation mechanisms of…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,64],"tags":[250,701,5725,1858,5726,1807,2414,5727,5728],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23907"}],"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=23907"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23907\/revisions"}],"predecessor-version":[{"id":23908,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23907\/revisions\/23908"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=23907"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=23907"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=23907"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}