LINK<\/strong><\/a><\/p>\n\n\n\n“Boriskino is a poorly studied CM chondrite with numerous millimeter\u2010 to centimeter\u2010scale clasts exhibiting sharp boundaries. Clast textures and mineralogies attest to diverse geological histories with various degrees of aqueous alteration. We conducted a petrographic, chemical, and isotopic study on each clast type of the breccia to investigate if there exists a genetic link between brecciation and aqueous alteration, and to determine the controlling parameter of the extent of alteration. Boriskino is dominated by CM2 clasts for which no specific petrographic type could be assigned based on the chemical compositions and modal abundances of constituents. One clast stands out and is identified as a CM1 lithology, owing to its lack of anhydrous silicates and its overall abundance of dolomite\u2010like carbonates and acicular iron sulfides. We observe that alteration phases near clast boundaries exhibit foliation features, suggesting that brecciation postdated aqueous alteration. We measured the O\u2010isotopic composition of Ca\u2010carbonates and dolomite\u2010like carbonates to determine their precipitation temperatures following the methodology of Verdier\u2010Paoletti et al. (2017). Both types of carbonates yield similar ranges of precipitation temperatures independent of clast lithology, ranging from \u221213.9 \u00b1 22.4 (2\u03c3) to 166.5 \u00b1 47.3 \u00b0C, precluding that temperature alone accounts for the differences between the CM1 and CM2 lithologies. Instead, we suggest that initial water\/rock ratios of 0.75 and 0.61 for the CM1 and CM2 clasts, respectively, might control the extent of aqueous alteration. Based on these estimates, we suggest that Boriskino clasts originated from a single parent body with heterogeneous distribution of water either due to local differences in the material permeability or in the initial content of ice available. These conditions would have produced microenvironments with differing geochemical conditions thus leading to a range of degrees of aqueous alteration.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Maximilien J. Verdier\u2010Paoletti, Yves Marrocchi, Lionel G. Vacher, J\u00e9r\u00f4me Gattacceca, Andrey Gurenko, Corinne Sonzogni, Matthieu Gounelle Meteoritics & Planetary Science First Published: 29 May 2019 LINK “Boriskino is a poorly studied CM chondrite with numerous…<\/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],"tags":[1842,1392,2746,3273,105,4997],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/19652"}],"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=19652"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/19652\/revisions"}],"predecessor-version":[{"id":19653,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/19652\/revisions\/19653"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=19652"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=19652"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=19652"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}