LINK<\/strong><\/a><\/p>\n“Boriskino is a little studied CM2 chondrite composed of millimeter-sized clasts of different lithologies and degrees of alteration. Boriskino thus offers a good opportunity to better understand the preaccretionary alteration history and collisional evolution that took place on the CM parent body. The least altered lithology displays 16O-poor Type 1a calcite and aragonite grains (\u03b418O \u2248 30-37\u2030, \u03b417O \u2248 15-18\u2030 and \u039417O \u2248 -2 to 0\u2030, SMOW) that precipitated early, before the establishment of the petrofabric, from a fluid whose isotopic composition was established by isotopic exchange between a 16O-poor water and 16O-rich anhydrous silicates. In contrast, the more altered lithologies exhibit 16O-rich Type 2a and veins of calcite (\u03b418O \u2248 17-23\u2030, \u03b417O \u2248 6-9\u2030 and \u039417O \u2248 -4 to -1\u2030, SMOW) that precipitated after establishment of the deformation, from transported 16O-rich fluid in preexisting fractures. From our petrographic and X-ray tomographic results, we propose that the more altered lithologies of Boriskino were subjected to high intensity impact(s) (10-30 GPa) that produced a petrofabric, fractures and chondrule flattening. Taking all our results together, we propose a scenario for the deformation and alteration history of Boriskino, in which the petrographic and isotopic differences between the lithologies are explained by their separate locations into a single CM parent body. Based on the \u03b413C-\u03b418O values of the Boriskino Type 2a calcite (\u03b413C \u2248 30-71\u2030, PDB), we propose an alternative \u03b413C-\u03b418O model where the precipitation of Type 2a calcite can occurred in an open system environment with the escape of 13C-depleted CH4 produced from the reduction of C-bearing species by H2 released during serpentinization or kamacite corrosion. Assuming a mean precipitation temperature of 110\u00b0C, the observed \u03b413C variability in T2a calcite can be reproduced by the escape of \u2248 15-50% of dissolved carbon into CH4 by Rayleigh distillation.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Lionel G. Vacher, Yves Marrocchi, Johan Villeneuve, Maximilien J. Verdier-Paoletti, Matthieu Gounelle Geochimica et Cosmochimica Acta In Press, Accepted Manuscript, Available online 10 August 2018 LINK “Boriskino is a little studied CM2 chondrite composed of…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61,9,18,127],"tags":[4643,4078,1392,1241,3273,3254,105,3646],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/16075"}],"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=16075"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/16075\/revisions"}],"predecessor-version":[{"id":16076,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/16075\/revisions\/16076"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16075"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16075"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16075"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}