LINK<\/strong><\/a><\/p>\n\n\n\n“The Tarda meteorite is a recently recovered C2-ungrouped carbonaceous chondrite that preserves evidence of early Solar System aqueous alteration. Tarda was found to share reflectance spectra with P-type asteroids, possibly enabling these elusive asteroids to be studied in the laboratory for the first time. Furthermore, Tarda has been shown to share many petrological and isotopic affinities with Tagish Lake \u2013 a pristine C2-ungrouped chondrite that is widely considered to source a D-type asteroid. Thus Tarda, Tagish Lake, and their respective spectral classes are probably genetically related, and potentially source a shared parent body. Despite their similarities, however, Tagish Lake hosts different lithologies and carbonate species than Tarda, suggesting distinct aqueous alteration histories between the two meteorites. Here, we present in-situ oxygen, carbon, and 53Mn\u201353Cr isotopic analyses of dolomite and magnetite in Tarda using Secondary Ion Mass Spectrometry to (i) investigate the conditions associated with aqueous alteration on the early Tarda parent body, and to (ii) compare our findings with Tagish Lake to assess heterogeneous aqueous alteration of their unique and likely shared parent body. For dolomite, we found that \u03b413C ranged from 55.8\u202f\u2030 to 72.9\u202f\u2030, while \u03b418O ranged from 23.3\u202f\u2030 to 28.8\u202f\u2030 with an average \u039417O of 0.1\u202f\u00b1\u202f1.6. Dolomite additionally contained widespread 53Cr excesses that, if interpreted to have chronological significance, corresponds to a live [(53Mn\/55Mn)0] value of (3.08 +\/- 0.52)x10^-6. For magnetite, the \u03b418O values ranged from \u22125.5\u202f\u2030 to 5.8\u202f\u2030 with an average \u039417O of 2.4\u202f\u2030\u202f\u00b1\u202f1.7. Oxygen isotope thermometry of a co-precipitating dolomite\u2013magnetite pair indicates alteration temperatures of 87 +28\/-24\u00b0C. Compared to carbonates in Tagish Lake, dolomite in Tarda exhibits systematically lower \u03b417O, \u03b418O, and \u039417O signatures, but similar \u03b413C signatures. Temporally, the carbonates in both meteorites have identical ages within uncertainty. We conclude that Tarda has experienced greater aqueous alteration than Tagish Lake, likely due to increased water\u2013rock interaction and\/or higher temperatures”<\/p>\n","protected":false},"excerpt":{"rendered":"
Bennett J.K. Wilson, Kazuhide Nagashima, Thomas J. Barrett, Veronica E. Di Cecco, Kimberly T. Tait, Michael G. Daly Geochimica et Cosmochimica Acta, In Press, Journal Pre-proof, Available online 21 December 2025 LINK “The Tarda meteorite…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[61,9,5746,335,47],"tags":[5708,4859,1842,4958,250,3273,5037,994,1845,5747,1832,4205,4390,5728],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/39948"}],"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=39948"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/39948\/revisions"}],"predecessor-version":[{"id":39949,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/39948\/revisions\/39949"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=39948"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=39948"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=39948"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}