LINK<\/strong><\/a><\/p>\n\n\n\n“We report the mineralogy and texture of magnetite grains, a magnetite\u2010dolomite assemblage, and the adjacent mineral phases in five hydrated fine\u2010grained Antarctic micrometeorites (H\u2010FgMMs). Additionally, we measured the oxygen isotopic composition of magnetite grains and a magnetite\u2010dolomite assemblage in these samples. Our mineralogical study shows that the secondary phases identified in H\u2010FgMMs have similar textures and chemical compositions to those described previously in other primitive solar system materials, such as carbonaceous chondrites. However, the oxygen isotopic compositions of magnetite in H\u2010FgMMs span a range of \u220617O values from +1.3\u2030 to +4.2\u2030, which is intermediate between magnetites measured in carbonaceous and ordinary chondrites (CCs and OCs). The \u03b418O values of magnetites in one H\u2010FgMM have a ~27\u2030 mass\u2010dependent spread in a single 100 \u00d7 200 \u03bcm particle, indicating that there was a localized control of the fluid composition, probably due to a low water\u2010to\u2010rock mass ratio. The \u220617O values of magnetite indicate that H\u2010FgMMs sampled a different aqueous fluid than ordinary and carbonaceous chondrites, implying that the source of H\u2010FgMMs is probably distinct from the asteroidal source of CCs and OCs. Additionally, we analyzed the oxygen isotopic composition of a magnetite\u2010dolomite assemblage in one of the H\u2010FgMMs (sample 03\u201036\u201046) to investigate the temperature at which these minerals coprecipitated. We have used the oxygen isotope fractionation between the coexisting magnetite and dolomite to infer a precipitation temperature between 160 and 280 \u00b0C for this sample. This alteration temperature is ~100\u2013200 \u00b0C warmer than that determined from a calcite\u2010magnetite assemblage from the CR2 chondrite Al Rais, but similar to the estimated temperature of aqueous alteration for unequilibrated OCs, CIs, and CMs. This suggests that the sample 03\u201036\u201046 could come from a parent body that was large enough to attain temperatures as high as the OCs, CIs, and CMs, which implies an asteroidal origin for this particular H\u2010FgMM.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Elena Dobric\u0103, Ryan C. Ogliore, C\u00e9cile Engrand, Kazuhide Nagashima, Adrian J. Brearley Meteoritics & Planetary Science First Published: 21 July 2019 LINK “We report the mineralogy and texture of magnetite grains, a magnetite\u2010dolomite assemblage, and…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3157],"tags":[4382,994,327],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/20109"}],"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=20109"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/20109\/revisions"}],"predecessor-version":[{"id":20110,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/20109\/revisions\/20110"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=20109"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=20109"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=20109"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}