The characteristics of the metamorphosed banded iron formation (meta-BIF) in the Mt. Riiser-Larsen area, Amundsen Bay, Enderby Land, Antarctica were investigated in order to understand why a large magnetic anomaly appeared in this region. The study found many meta-BIF layers, consisting of one to nine layers within 30 m thickness in felsic gneiss. The thicknesses of individual layers were usually 0.5–2 m but sometimes varied from zero to 6 m. Almost all strong magnetic anomalies reported by Dolinsky et al. (2002) could be explained by the magnetization of the meta-BIF layers. To explain the source of the magnetic anomaly, the natural remanent magnetization of meta-BIF and its susceptibility are taken in to account. The largest layer including meta-BIF is estimated to be more than 7400 × 213 m. Magnetite in the layer was examined by thermomagnetic, magnetic hysteresis and microscopic analyses. The results indicated that almost pure magnetite with pseudosingle-domain (PSD) and multi-domain structure is the dominant composition of meta-BIF as well as quartz. The PSD magnetite grains were along the quartz crystal boundaries and formed a network structure. The electric conductivity of the meta-BIF is explained by this network structure rather than being due to the high magnetite concentration.
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- Characteristics of Metamorphosed Banded Iron Formation and Its Relation to the Magnetic Anomaly in the Mt. Riiser-Larsen Area, Amundsen Bay, Enderby Land, Antarctica
- Springer Berlin Heidelberg
- Chapter 2.1