Rockmagnetism and palaeomagnetism of an Early Cretaceous/Late Jurassic dike swarm in Rio Grande do Norte, Brazil

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C. Bucker
A. Schult
W. Bloch
S.D.C. Guerreiro


Ten sites from a dike swarm of early Cretaceous/Late Jurassic age in northeast Brazil (5.7°S, 36.6°W) yielded a pole at 80.6°N, 95°E with A95 = 9.5°, K = 26.7 after AF cleaning. Rock-magnetic investigations and chemical analyses revealed titanomagnetites and maghemites, both with low titanium content showing ilmenite exsolution lamellae (oxidation class III). These are due to an internal high-temperature oxidation during cooling of the large dikes, follwed by low-temperature oxidation and/or hydrothermal alterations. There is evidence that with low-temperature oxidation the Ti-to-Fe ratio increases, a finding that is consistent with previous studies. Hysteresis parameters and susceptibility versus temperature curves can be interpreted in terms of pseudosingle-domain behavior with a trend toward multidomain behavior in accordance with moderate-to-weak stability of the remanence.

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Bucker, C., A. Schult, W. Bloch, and S.D.C. Guerreiro. 1986. “Rockmagnetism and Palaeomagnetism of an Early Cretaceous/Late Jurassic Dike Swarm in Rio Grande Do Norte, Brazil”. Journal of Geophysics 60 (1), 129-35.
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