A rock- and paleomagnetic study of a Holocene lava flow in Central Mexico
| Autor: | Silvia Gonzalez, L Alva-Valdivia, C.B de Boer, J Urrutia-Fucugauchi, P. Vlag |
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| Jazyk: | angličtina |
| Rok vydání: | 1999 |
| Předmět: |
Paleointensities
Paleomagnetism Lavas Physics and Astronomy (miscellaneous) Lava Aardwetenschappen Geochemistry Astronomy and Astrophysics Geophysics engineering.material Rock magnetism chemistry.chemical_compound chemistry Space and Planetary Science Remanence engineering Curie temperature Mexico Geology Holocene Ilmenite Magnetite |
| Zdroj: | Physics of the Earth and Planetary Interiors, 118, 259. Elsevier Science B.V. |
| Popis: | Magnetic measurements of the Tres Cruces lava flow (ca. 8500 years BP, Central Mexico) show the presence of two remanence carriers, a Ti-rich titanomagnetite with a Curie temperature between 350 and 400°C and a Ti-poor magnetite with a Curie temperature close to 580°C. Magnetic changes after heating indicate that the titanomagnetite exsolves into magnetite and ilmenite when the sample is heated to 580°C. Paleointensity estimates with the Thellier and Thellier method [Thellier, E., Thellier, O., 1959. Sur l'intensite du champ magnetique terrestre dans le passe historique et geologique. Ann. Geophysique., 15, 285–376] were only successful up to temperatures of 350 to 400°C. This temperature corresponds with the Curie temperature of the titanomagnetite, which is probably pseudo-single or multi-domain. Therefore, the paleointensities should be interpreted with caution. The magnetic composition changes after 580°C heating may explain the large variations in previous paleointensity determinations for the Tres Cruces rocks [Gonzalez, S., Sherwood, G., Bohnel, H., Schnepp, E., 1997. Palaeosecular variation in Central Mexico over the last 30,000 years: the record from lavas. Geophys. J. Int., 130, 201–219] using the Shaw method [Shaw, J., 1974. A new method of determining the magnitude of the palaeomagnetic field: application to five historic lavas and five archaeological samples. Geophys. J. R. Astr. Soc., 39, 133–141]. |
| Databáze: | OpenAIRE |
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