Fundamental rock magnetic
requires studying the magnetic properties of natural and synthetic magnetic
minerals as function of chemical composition, crystallinity and grain size.
This research determined
diagnostic rock magnetic parameters of hematite and maghemite. These magnetic
ferric oxides are common in a wide variety of rock types and soils. Hence,
their importance for paleomagnetism, soil- and environmental sciences and
paleoclimate reconstructions is evident. |
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Hematite
(a-Fe2O3
)
This most
stable iron oxide is named after the Greek word haimatitis (blood
red), in allusion to its colour. The magnetic properties of hematite
appear to be extremely variable and are susceptible to the distorting effect
of minute amounts of magnetic contaminants.
Hematite is referred
to as canted antiferromagnetic. De
Boer and Dekkers (1998) measured the thermomagnetic behaviour of a
pure and defect-poor hematite. |
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Maghemite
( g-Fe2O3
)
The name of this highly
magnetic iron oxide is formed from the first syllables of magnetite (Fe3O4)
and hematite. It has the same chemical composition as hematite, but its
structure is similar to magnetite. In nature, maghemite is predominantly
formed by low-temperature oxidation of magnetite. It is, however, thermodynamically
metastable and inverts to hematite on heating above ~250 °C. Average
hysteresis properties resemble those of magnetite, but De Boer and Dekkers
(1996) found small but significant differences.
For
4 years, you are trapped in the dungeons of the Fort
|
| With the International
Institute for Aerospace Survey and Earth Sciences (ITC) we were involved
in the research and the fight against the subsurface coal
fires in China by dating the paleo-coal fires magnetostratigraphically.
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2004
-
Zangh, X. Kroonenberg,
S.B. and de Boer, C.B. (2004). Dating of coal fires in Xinjiang, north-west
China, Terra Nova, 16, 68-74.
2001
-
De Boer, C.B. and Dekkers,
M.J. (2001). Unusual thermomagnetic behaviour of haematites: neoformation
of a highly magnetic spinel phase on heating in air. Geophys.
J. Int., 144,
481-494.
-
De Boer, C.B., Mullender,
T.A.T. and Dekkers, M.J. (2001). Low-temperature behaviour of haematite:
susceptibility and magnetization increase on cycling through the Morin
transition, Geophys. J. Int., 146, 201-216.
-
De Boer, C.B., Dekkers,
M.J. and Van Hoof, A.A.M. (2001). Rock magnetic properties of TRM carrying
baked and molten rocks straddling burnt coal seams, Phys. Earth Planet.
Inter.,
126, 93-108
2000
-
Vlag, P., Alva-Valdivia,
L., de Boer, C.B., Gonzalez, S. and Urrutia-Fucugauchi, J. (2000). A rock-
and paleomagnetic study of a Holocene lava flow in Central Mexico,
Phys.
Earth Planet. Inter., 118, 259-272.
1999
-
De Boer, C.B. (1999).
Rock-Magnetic studies on Hematite, Maghemite and Combustion-Metamorphic
Rocks (PhD thesis, Utrecht University), Geologica Ultraiectina, 177,
254 pp.
1998
-
De Boer, C. and Dekkers,
M.J. (1998). Thermomagnetic behaviour of haematite and goethite as a function
of grain size in various non-saturating magnetic fields. Geophys. J.
Int., 133, 541-552.
1996
-
De Boer, C.B. and Dekkers,
M.J. (1996). Grain-size dependence of the rock magnetic properties for
a natural maghemite, Geophys. Res. Lett.,23, 2815-2818.
-
Petrovsky, E., Kropacek,
V. Dekkers, M.J., de Boer, C., Hoffman, V. and Ambatiello, A. (1996). Transformation
of hematite to maghemite as observed by changes in magnetic parameters:
Effects of mechanical activation ?, Geophys. Res. Lett., 23,
1477-1480.
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