GEOPHYSICAL RESEARCH, 2017, vol. 18, no. 1, pp. 37-48. DOI: 10.21455/gr2017.1-3
UDC 550.382
Abstract References Full text (in Russian)
THE EFFECT OF CHEMICAL MAGNETIZATION ON THE PALEOINTENSITY DETERMINED BY THE THELLIER METHOD: EXPERIMENTAL STUDY ON TITANOMAGNETITE-CONTAINING BASALTS
S.K. Gribov
Borok Geophysical Observatory of Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Borok (Yaroslavl region), Russia
Abstract. The simulation of the Thellier–Coe paleointensity experiments was performed on laboratory oxyexsolved titanomaghemite-bearing basaltic samples with either a separately created chemical remanent magnetization (CRM) or a partial thermoremanent magnetization (pTRM) or a combination of both.
It is shown that the Thellier method makes it possible to determine the magnetic field of ‘pure’ pTRM with an error not exceeding 10 %. In contrast, the field estimate for CRM by this method is understated by 40–60 % relative to the true value. At the same time, however, CRM cannot be distinguished from TRM on the Arai–Nagata graphical construction of the stepwise heating Thellier–Coe procedure. In the paleomagnetic aspect, all of this means that igneous rocks containing magnetite formed through oxyexsolution of highly cation-deficient titanomagnetites and carrying thermochemical magnetization may be the source of a significant error in determination of the paleointensity of geomagnetic field by the Thellier method when a natural CRM is not recognized and is mistakenly interpreted as a TRM in the Thellier-type experiments.
Keywords: titanomagnetites, oxyexsolution, chemical remanent magnetization, Thellier method, paleointensity.
References
Carvallo C., Özdemir Ö., and Dunlop D. Paleointensity determinations, palaeodirections and magnetic properties of basalts from the Emperor seamounts, Geophys. J. Int., 2004, vol. 156, no. 1, pp. 29-38.
Coe R.S. The determination of paleointensities of the Earth’s magnetic field with special emphasize on mechanisms which could cause nonideal behavior in Thellier method, J. Geomag. Geoelectr., 1967, vol. 19, no. 3, pp. 157-179.
Coe R.S., Gromme C.S., and Mankinen E.A. Geomagnetic paleointensities from radiocarbon-dated lava flows on Hawaii and the question of the Pacific nondipole low, J. Geophys. Res., 1978, vol. 83, no. B4, pp. 1740-1756.
Draeger U., Prévot M., Poidras T., and Riisager J. Single-domain chemical, thermochemical and thermal remanences in a basaltic rock, Geophys. J. Int., 2006, vol. 166, no. 1, pp. 12-32.
Dunlop D. and, Özdemir Ö. Rock magnetism: fundamentals and frontiers. New York: Cambridge Univ. Press, 1997.
Gribov S.K., Dolotov A.V, and Tselmovich V.A. Peculiarities of magnetic and mineralogical transformation og natural titanomagnetites in air under isothermal conditions, Uchenye Zapiski Kazanskogo Universiteta. Seriya Estestvennye Nauki (Scientific Notes of the Kazan’ State University, Natural Sciences), 2014, vol. 156, no. 1, pp. 64-78.
Grommé S., Mankinen E., Marshall M., and Coe R.S. Geomagnetic paleointensities by the Thelliers’ method from submarine pillow basalts: effects of seafloor weathering, J. Geophys. Res., 1979, vol. 84, no. B7, pp. 3553-3575.
Haggerty S.E. Oxide textures: a mini-atlas. In: D.H. Lindsley (ed). Oxide Minerals: Petrologic and Magnetic Significance. Mineral. Soc. Am., 1991, vol. 25, no. 1, pp. 129-219.
Herrero-Bervera E. and Valet J.P. Testing determinations of absolute paleointensity from the 1955 and 1960 Hawaiian flows, Earth Planet. Sci. Lett., 2009, vol. 287, pp. 420-433.
Kissel C. and Laj C. Improvements in procedure and paleointensity selection criteria (PICRIT-03) for Thellier and Thellier determinations: application to Hawaiian basaltic long cores, Phys. Earth Planet. Inter., 2004, vol. 147, no. 2-3, pp. 155-169.
Laj C., Kissel C., Scao V., Beer J., Thomas D.M., Guillou H., Muscheler R., and Wagner G. Geomagnetic intensity and inclinations at Hawaii for the past 98 kyr from core SOH-4 (Big Island): a new study and a comparison with existing contemporary data, Phys. Earth Planet. Inter., 2002, vol. 129, no. 3-4, pp. 205-243.
Maksimochkin V.I. and Tselebrovskiy A.N., The influence of the chemical magnetization of oceanic basalts on determining the geomagnetic field paleointensity by the Thellier method, Moscow University Physics Bulletin, 2015, vol. 70, no. 6, pp. 566–576
Nagata T., Arai Y., and Momose K. Secular variation of the geomagnetic total force during the last 5000 years, J. Geophys. Res., 1963, vol. 68, no. 18, pp. 5277-5281.
Prévot M., Mankinen E., Grommé S., and Lecaille A. High paleointensities of the geomagnetic field from thermomagnetic studies on rift valley pillow basalts from the Mid-Atlantic Ridge, J. Geophys. Res., 1983, vol. 88,. no. B3, pp. 2316-2326.
Selkin P.A. and Tauxe L. Long-term variations in palaeointensity, Philos. Trans. R. Soc. London, ser. A. 2000, vol. 358, no. 1768, pp. 1065-1088.
Thellier E. and Thellier O. Sur l’intensité du champ magnétique terrestre dans le passé historique et géologique, Ann. Geophys., 1959, vol. 15, pp. 285-376.
Yamamoto Y., Tsunakawa H., and Shibuya H. Palaeointensity study of the Hawaiian 1960 lava: implications for possible causes of erroneously high intensities, Geophys. J. Int., 2003, vol. 153, no. 1, pp. 263-276.