LINK<\/strong><\/a><\/p>\n\n\n\n“Highlights<\/p>\n\n\n\n
\u2022 The coordination number of Al in melilite glasses and melts were observed by NMR (predominant 4 coordinated Al and small fraction of five coordinate Al).
\u2022 The network connectivity and structural disorder in type A CAI-like melts were revealed using NMR.
\u2022 Despite the strong preference of Si over Al for NBOs, Ca-O-Al is observed in type A CAI-like melts.
\u2022 The structural changes should be considered to interpret the melt properties including viscosity, diffusivity, and oxygen isotopic composition.”<\/p>\n\n\n\n
“Exploring the polymerization and structural disorder of Ca-Al-rich inclusion (CAI)-like melts is a key question in cosmochemistry due to strong implications for macroscopic properties of melts (i.e., viscosity and diffusivity). Here, we report experimental results showing the effect of composition on the structure of melilite glasses and melts [\u00e5kermanite (\u00c5k, Ca2MgSi2O7) – gehlenite (Gh, Ca2Al2SiO7)] in type A CAIs with varying composition using high-resolution solid-state nuclear magnetic resonance (NMR). The 27Al magic angle spinning (MAS) and 3Q (triple quantum) MAS NMR spectra of melilite glasses show predominant [4]Al. A non-negligible fraction of [5]Al is observed in \u00c5k50Gh50 and \u00c5k72Gh28 glasses and it slightly increases with increasing \u00e5kermanite content. The 17O 3QMAS NMR spectra of melilite glasses show that bridging oxygens (BOs, Si\u2013O\u2013Si, Al\u2013O\u2013Al, and Si\u2013O\u2013Al) and non-bridging oxygens (NBOs, Ca\u2013O-Si, Ca-O-Al, and mixed {Ca, Mg}\u2013NBO) are partially resolved. Despite the strong preference of Si over Al for NBOs, for the first time, Ca-O-Al is observed in natural melts (i.e., gehlenite and \u00c5k25Gh75 glasses and melts). The results show that Al-NBO (~150\u202fppm in MAS dimension) can be distinguished from Si-NBO (~110\u202fppm) in melilite glasses and melts. The fraction of NBO increases with increasing \u00e5kermanite content. The experimental results suggest that composition-induced structural changes should be considered to interpret the melt viscosity, diffusivity, and oxygen isotopic composition of CAI-like melts in the early Solar System.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Sun Young Park, Changkun Park, Hyun Na Kim, Seoyoung Lee, Sung Keun Lee Chemical GeologyIn Press, Journal Pre-proof, Available online 16 September 2020 LINK “Highlights \u2022 The coordination number of Al in melilite glasses and…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[66,72,71,2531],"tags":[1846,5706,3701,5181,675],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23844"}],"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=23844"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23844\/revisions"}],"predecessor-version":[{"id":23845,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/23844\/revisions\/23845"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=23844"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=23844"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=23844"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}