Erratum to “Reconstruction of millennial changes in dust emission, transport and regional sea ice coverage using the deep EPICA ice cores from the Atlantic and Indian Ocean sector of Antarctica

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• 作者：Hubertus Fischer ; Felix Fundel ; Urs Ruth ; Birthe Twarloh ; Anna Wegner ; Roberto Udisti ; Silvia Becagli ; Emiliano Castellano ; Andrea Morganti ; Mirko Severi ; Eric Wolff ; Genevieve Littot ; Regine Rö ; t
• 关键词：stishovite ; hydrogen ; lower mantle ; eclogite ; infrared spectroscopy
• 刊名：Earth and Planetary Science Letters
• 出版年：2007
• 出版时间：30 October 2007
• 年：2007
• 卷：262
• 期：3-4
• 页码：635
• 全文大小：81 K

文摘

Stishovite is an important phase in subducting oceanic crust. The post-garnet assemblage from a precursor eclogite lithology contains up to 25 % stishovite at pressures above 25 GPa. This stishovite may contain up to 5 wt. % Al₂O₃. We measured the hydrogen contents of stishovite samples synthesized at 20–25 GPa and 1200–1800 °C from several starting materials containing up to 10 wt. % Al₂O₃. FTIR spectra of stishovite show major bands at 3111–3134 cm^{− 1}, with the frequencies increasing as H₂O and Al₂O₃ contents increase, and several minor bands at 2659–2667, 3240, 3261, 3312–3334, and 3351 cm^{− 1}. The H₂O content of Al-free stishovite is in the range of 16–30 wt. ppm. The maximum H₂O content of Al-bearing stishovite (4.4 wt. % Al₂O₃) synthesized at 20 GPa and 1400 °C is 3010 ± 300 wt. ppm. Most hydrogen in stishovite is associated with Al³⁺ substitutional defects on the octahedral (Si⁴⁺) site. The hydrogen can occupy 40 % of vacancies created by incorporation of Al³⁺ at 20 GPa. This observation along with some anomalies in the FTIR spectra may indicate an alternative mechanism of Al³⁺ incorporation into stishovite via the formation of oxygen vacancies or interstitial Al_i defects. We report the highest H₂O concentrations in Al-stishovite to date, and argue that it is the most important carrier of water into the lower mantle post-garnet eclogitic assemblages.