Open AccessA paleointensity technique for multidomain igneous rocks
Author(s) -
Wang Huapei,
Kent Dennis V.
Publication year - 2013
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/ggge.20248
Subject(s) - geology , remanence , magnetization , natural remanent magnetization , magnetite , paleomagnetism , rock magnetism , demagnetizing field , earth's magnetic field , thermoremanent magnetization , mineralogy , igneous rock , geophysics , magnetic field , physics , geochemistry , paleontology , quantum mechanics
We developed a paleointensity technique to account for concave‐up Arai diagrams due to multidomain (MD) contributions to determine unbiased paleointensities for 24 trial samples from site GA‐X in Pleistocene lavas from Floreana Island, Galapagos Archipelago. The main magnetization carrier is fine‐grained low‐titanium magnetite of variable grain size. We used a comprehensive back‐zero‐forth (BZF) heating technique by adding an additional zero‐field heating between the Thellier two opposite in‐field heating steps in order to estimate paleointensities in various standard protocols and provide internal self‐consistency checks. After the first BZF experiment, we gave each sample a total thermal remanent magnetization (tTRM) by cooling from the Curie point in the presence of a low (15 µT) laboratory‐applied field. Then we repeated the BZF protocol, with the laboratory‐applied tTRM as a synthetic natural remanent magnetization (NRM), using the same laboratory‐applied field and temperature steps to obtain the synthetic Arai signatures, which should only represent the domain‐state dependent properties of the samples. We corrected the original Arai diagrams from the first BZF experiment by using the Arai signatures from the repeated BZF experiment, which neutralizes the typical MD concave‐up effect. Eleven samples meet the Arai diagram post‐selection criteria and provide qualified paleointensity estimates with a mean value for site GA‐X of 4.23 ± 1.29 µT, consistent with an excursional geomagnetic field direction reported for this site.