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Cooling rates of pyroclastic deposits inferred from mineral magnetic investigations: a case study from the Pleistocene Mýtina Maar (Czech Republic)

Lied, Philipp; Kontny, Agnes; Nowaczyk, Norbert; Mrlina, Jan; Kämpf, Horst

Abstract:
Tephra layers of the Mýtina Maar, Czech Republic, contain ferrimagnetic Mg–Al-rich titanomagnetite, which is suggested to originate from a fractionated alkaline CO$_{2}$-rich lithospheric mantle melt. We investigated the magnetic mineralogy and Curie temperature (T$_{C}$) from tephra deposits of two drill cores (< 9 m depth). T$_{C}$ calculated (208 ± 14 °C) from chemical composition (Fe$^{2+}$$_{0.8}$Mg$_{0.5}$Fe$^{3+}$$_{1.1}$Al$_{0.3}$Ti$_{0.3}$O$_{4}$) is in accordance with TC retrieved from cooling curves of temperature-dependent magnetic susceptibility measurements (195–232 °C). However, thermomagnetic curves are irreversible either with lower (type I) or higher (type II) TC in the heating curve. All curves show transition temperatures above ca. 390 °C, indicating maghemitization. We interpret the irreversibility of TC (ΔT$_{C}$) in terms of different degrees of cation ordering, overprinted or masked by different degrees of maghemitization, which is a low-temperature phenomenon. Negative ΔT$_{C}$ indicates that original deposited titanomagnetite has cooled faster and, therefore, has stored a lower degree of cation ordering compared to heating/cooling rate of 11 °C/min in the Kappabridge. ... mehr

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Postprint §
DOI: 10.5445/IR/1000119422
Veröffentlicht am 13.06.2020
Originalveröffentlichung
DOI: 10.1007/s00531-020-01865-1
Scopus
Zitationen: 1
Web of Science
Zitationen: 1
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Angewandte Geowissenschaften (AGW)
Institut für Angewandte Materialien - Angewandte Werkstoffphysik (IAM-AWP)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 1437-3254, 1437-3262
KITopen-ID: 1000119422
HGF-Programm 31.03.09 (POF III, LK 01) Strukturmaterial f. Blanket und Divertor
Erschienen in International journal of earth sciences
Verlag Springer Verlag
Band 109
Seiten 1707-1725
Vorab online veröffentlicht am 13.05.2020
Schlagwörter Eger rift system, Maar-diatreme volcano, Titanomagnetite, Curie temperature, Cation ordering effect, Maghemitization, Pyroclastic emplacement mechanism
Nachgewiesen in Scopus
Web of Science
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