LINK<\/strong><\/a><\/p>\n\n\n\n“In situ U\u2010Pb measurements on zircons of the Ries impact crater are presented for three samples from the quarry at Polsingen. The U\u2010Pb data of most zircons plot along a discordia line, leading to an upper intercept of Carboniferous age (331 \u00b1 32 Ma [2\u03c3]). Four zircons define a concordia age of 313.2 \u00b1 4.4 Ma (2\u03c3). This age most probably represents the age of a granite from the basement target rocks. From granular textured zircon grains (including baddeleyite and anatase\/Fe\u2010rich phases, first identified in the Ries crater), most probably recrystallized after impact (13 analyses, 4 grains), a concordia age of 14.89 \u00b1 0.34 Ma (2\u03c3) and an error weighted mean 206Pb\/238U age of Ma 14.63 \u00b1 0.43 (2\u03c3) is derived. Including the youngest concordant ages of five porous textured zircon grains (24 spot analyses), a concordia age of 14.75 \u00b1 0.22 Ma (2\u03c3) and a mean 206Pb<\/em>\/238U age of 14.71 \u00b1 0.26 Ma (2\u03c3) can be calculated. These results are consistent with previously published 40Ar\/39Ar ages of impact glasses and feldspar. Our results demonstrate that even for relatively young impact craters, reliable U\u2010Pb ages can be obtained using in situ zircon dating by SIMS. Frequently the texture of impact shocked zircon grains is explained by decomposition at high temperatures and recrystallization to a granular texture. This is most probably the case for the observed granular zircon grains having baddeleyite\/anatase\/Fe\u2010rich phases. We also observe non\u2010baddeleyite\/anatase\/Fe\u2010rich phase bearing zircons. For these domains, reset to crater age is more frequently for high U,Th contents. We tentatively explain the higher susceptibility to impact resetting of high U,Th domains by enhanced Pb loss and mobilization due to higher diffusivity within former metamict domains that were impact metamorphosed more easily into porous as well as granular textures during decomposition and recrystallization, possibly supported by Pb loss during postimpact cooling and\/or hydrothermal activity.”<\/p>\n","protected":false},"excerpt":{"rendered":"Winfried H. Schwarz, Michael Hanel, Mario Trieloff Meteoritics & Planetary Science First Published: 27 January 2020 LINK “In situ U\u2010Pb measurements on zircons of the Ries impact crater are presented for three samples from the…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[90],"tags":[3874,3259,2119,831,1923,1934,184],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/21313"}],"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=21313"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/21313\/revisions"}],"predecessor-version":[{"id":21314,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/21313\/revisions\/21314"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=21313"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=21313"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=21313"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}