Paleogene volcanic ash layers in the Danish Basin: compositions and source areas in the North Atlantic Igneous Province

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• 作者：Larsen ; Lotte M. ; Fitton ; J. Godfrey ; Pedersen ; Asger K.
• 关键词：Denmark ; North Atlantic Igneous Province ; Paleogene ; Tephra ; Volcanic ash
• 刊名：Lithos
• 出版年：2003
• 出版时间：November, 2003
• 年：2003
• 卷：71
• 期：1
• 页码：47-80
• 全文大小：1.98 M

文摘

The Paleogene mo clay basin in Denmark contains ca. 200 layers of mostly well-preserved volcanic ash. Of these, ca. 77 layers have been analysed for major and trace elements by X-ray fluorescence spectrometry (XRF), 22 for rare-earth elements (REE), and 11 for Sr and Nd isotopes. The ‘negative’ ash series (layers −39 to −1) comprise tholeiitic basalt, crustally contaminated trachyte, and rhyolite; alkaline basalt, trachybasalt, trachyte, and rhyolite; and Ti-rich nephelinite and phonolite. The ‘positive’ ash series (layers +1 to +140) comprise enriched tholeiitic ferrobasalt and two rhyolite layers. The ferrobasalts form one comagmatic group; however, oscillations are seen up-section between less-enriched and more-enriched compositions, as indicated by variations in Zr/Nb, REE contents, and isotope compositions, suggesting heterogeneities in the mantle source. Two samples of Eocene ash from Greifswalder Oie in northern Germany are identical to the positive series ashes.