LINK<\/strong><\/a><\/p>\n\n\n\n“Highlights<\/p>\n\n\n\n
\u2022 Mn-Cr systematics of sphalerite in five E chondrites was established by SIMS.
\u2022 Mn-Cr system appears affected by weathering processes in MAC 88136.
\u2022 Other disturbances could relate to complex thermal histories.
\u2022 Substantial variation in initial 53Mn\/55Mn still limits chronologic applications.
\u2022 Chronologic potential is recognizable but requires additional research.”<\/p>\n\n\n\n
“We investigated the 53Mn-53Cr isotopic composition of a suite of enstatite chondrites by in situ analyses of various mineral phases with the Cameca IMS 1280-HR ion probe at Heidelberg, Germany, and a Cameca NanoSIMS at Paris, France. Only in sphalerite we found anomalies in 53Cr\/52Cr-ratios correlating with 55Mn\/52Cr which are due to decay of short-lived 53Mn (t1\/2=3.7 Ma). A sphalerite in the EH-impact melt LAP 02225 showed the largest excess of 53Cr, with 53Cr\/52Cr-ratios ranging up to 2.2. The calculated initial 53Mn\/55Mn-ratios are within the range of previous Mn-Cr studies. We observed a spatial variation within a large sphalerite in LAP 02225, translating in distinct initial 53Mn\/55Mn values. In case of the EL3 chondrite MAC 88136 the initial 53Mn\/55Mn derived for one sphalerite is at the lower end of previously reported values and may reflect a variable influence of alteration-induced exchange of common Cr. This is supported by the total reset of the 53Cr\/52Cr-ratio in another sphalerite in contact with an alteration vein irrespective of high Mn\/Cr-ratios. Our observed initial 53Mn\/55Mn-ratios of Sahara 97158, Indarch and EET 96135 correspond to the I-Xe systematics and hence, show that sphalerites can preserve reasonable age information. For Indarch however, if compared with other initial 53Mn\/55Mn values from literature, a considerable scatter is obvious. This clearly demonstrates that the Mn-Cr system in sphalerite can be disturbed by various, still poorly investigated, processes (e.g., by thermal events, weathering, diffusion-controlled remobilization). Future application of Mn-Cr dating to sphalerite in enstatite chondrites thus requires a better understanding of how such processes influence the Mn-Cr systematics and demands for tools to identify the undoubtly present sphalerites carrying a true chronologic information.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Jens Hopp, Julian-Christopher Storck, Thomas Ludwig, Smail Mostefaoui, Rainer Altherr, Ulrich Ott, Hans-Peter Meyer, Mario Trieloff Geochimica et Cosmochimica ActaIn Press, Journal Pre-proof, Available online 23 July 2021 LINK “Highlights \u2022 Mn-Cr systematics of sphalerite…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,68],"tags":[671,2201,1813,1682,6053,1681,6052],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28452"}],"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=28452"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28452\/revisions"}],"predecessor-version":[{"id":28453,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/28452\/revisions\/28453"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=28452"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=28452"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=28452"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}