{"id":22742,"date":"2020-07-22T09:57:42","date_gmt":"2020-07-22T07:57:42","guid":{"rendered":"http:\/\/karmaka.de\/?p=22742"},"modified":"2020-07-22T09:57:47","modified_gmt":"2020-07-22T07:57:47","slug":"discovery-of-coesite-from-the-martian-shergottite-northwest-africa-8657","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=22742","title":{"rendered":"Discovery of coesite from the martian shergottite Northwest Africa 8657"},"content":{"rendered":"\n<p>Sen Hu, Yang Li, Lixin Gu, Xu Tang, Ting Zhang, Akira Yamaguchi, Yangting Lin, Hitesh Changela<\/p>\n\n\n\n<p>Geochimica et Cosmochimica Acta<br>In Press, Journal Pre-proof, Available online 22 July 2020<\/p>\n\n\n\n<p><a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0016703720304415\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK<\/strong><\/a><\/p>\n\n\n\n<p class=\"justify-text\">&#8220;We report occurrences of coesite in a martian meteorite, expending previously-reported silica polymorphs such as stishovite (El Goresy et al., 2000), seifertite (Goresy et al., 2008; Sharp et al., 1999), and post-stishovite (El Goresy et al., 2000). The coesite was found in the shock-induced melt regions of NWA 8657, usually coexisting with deformed quartz and silica glass. Three morphological types of coesite have been identified: (I) in a silica-maskelynite assemblage, (II) needle grains, and (III) granular grains embedded in maskelynite. Transmission Electron Microscopy (TEM) shows that all types of coesite appear distributed in silica glass and\/or nano-phase maskelynite. The stishovite-like morphology of Type II coesite and the presence of deformed quartz suggest coesite to have inverted from stishovite during decompression. The impact-induced peak pressures and temperatures are estimated at \u223c 18-30 GPa and \u223c 2000 \u2103 respectively, based on static high pressure experiments (Langenhorst and Deutsch, 2012; Zhang et al., 1996). The polymorphs aggregates of silica in NWA 8657 indicate that the shock-induced melts in this meteorite cooled slower than those in other stishovite-bearing martian meteorites, but fast enough to preserve coesite.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Sen Hu, Yang Li, Lixin Gu, Xu Tang, Ting Zhang, Akira Yamaguchi, Yangting Lin, Hitesh Changela Geochimica et Cosmochimica ActaIn Press, Journal Pre-proof, Available online 22 July 2020 LINK &#8220;We report occurrences of coesite in&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[42,43],"tags":[2653,1828,4766,1829],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/22742"}],"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=22742"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/22742\/revisions"}],"predecessor-version":[{"id":22743,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/22742\/revisions\/22743"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=22742"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=22742"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=22742"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}