Titan-aegirine from early Tertiary ash layers in northern Denmark |
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Authors: | JG Rønsbo AK Pedersen J Engell |
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Institution: | 1. Institut for Mineralogi, Geologisk Centralinstitut, Øster Voldgade 5-7, DK-1350 København K, Danmark Denmark;2. Mineralogisk Museum, Geologisk Centralinstitut, Øster Voldgade 5-7, DK-1350 København K, Danmark Denmark;3. Laboratorium A, Danmarks tekniske Højskole, Bygning 207, DK-2800 Lyngby, Danmark Denmark |
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Abstract: | Microprobe analyses on a xenocrystic suite of salites, aegirine-augites, aegirines, titan-aegirines and acmites from a lower Tertiary ash layer in northern Denmark are presented. The sodic pyroxenes show an unusual titan-enrichment and up to 42 mol.% of the component , is estimated. Optical absorption measurements show no evidence for Ti3+. The titan-aegirines were formed during late to post-magmatic crystallization in a system with a high Ti4+/Fe2+ ratio and were followed by acmite showing enrichment in jadeite. Comparison with experimentally investigated titan-aegirine indicates crystallization far below the Mn2O3Mn3O4f02 buffer. |
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