第四紀火山灰についての段階的 I RM獲得実験と三成分 I RMの熱消磁実験
スポンサーリンク
概要
- 論文の詳細を見る
Paleomagnetic studies of widespread late Pleistocene tephras have been carried out in orderto construct geomagnetic charts for Japan in prehistoric times. Magnetic minerals containedin the welded tuff specimens are likely to be titanomagnetite and magnetite on the basis ofthe thermal demagnetization (ThD) results. Since ThD experiments were not performed onthe ash samples, it is not certain what magnetic minerals are in the ash samples. Progressiveacquisition of isothermal remanent magnetization (IRM) and ThD of a three-component IRM,therefore, were investigated to identify the ferromagnetic mineral content in the ash samples.For the IRM experiments, one sample from each site was arbitrarily chosen after thepaleomagnetic measurements. Because they are unconsolidated and readily disintegrate, theash samples were held in plastic cubes, which melt at about 160 ℃. Synthetic specimens wereprepared using the ash samples and plaster of Paris for ThD of the induced IRM.The IRM acquisition experiments were carried out using a pulse magnetizer in magneticfields with intensities up to 3000 mT. A three-component IRM was produced by applying adifferent DC field (3000, 400, and 120 mT) to each of the three perpendicular axes of thespecimen with the pulse magnetizer.The acquisition and ThD curves of the IRM components for almost all the specimens showsimilar features (A-type). The smooth IRM acquisition curves rise steeply up to 100 mT, andreach saturation by 500 mT. The ThD of each IRM component is plotted separately in thedemagnetization diagram. The ThD curves show that the soft (＜120 mT) coercivity fractionis the largest, and that the medium (120 to 400 mT) and hard (400 to 3000 mT) fractions are minor. The soft coercivity fraction was demagnetized smoothly to zero by 580 ℃, indicatingthat the specimens’magnetic mineralogy is also dominated by titanomagnetite and magnetite.The IRM acquisition curves for other some samples rise steeply at first but does not reachsaturation even in 3000 mT. The ThD curves show that the medium and hard fractionsexhibit evidences for unblocking of hematite at 680 ℃ (B-type), or unblocking of goethite at100 ℃ (C-type).
- 福井大学の論文
著者
関連論文
- 山口県に分布する阿蘇4火砕流堆積物の定置温度の推定
- 音海流紋岩と面谷流紋岩の外部ディテクター法によるフィッション・トラック年代
- 388 岐阜県北部に分布する白亜紀〜古第三紀火成岩類のFT年代
- O-37 山口県に分布する阿蘇4テフラの古地磁気方位
- 鬼界アカホヤテフラと福井県勝山市の池ケ原堆積物の古地磁気研究
- 第四紀火山灰についての段階的 I RM獲得実験と三成分 I RMの熱消磁実験
- 阿蘓4テフラ堆積時の日本列島における地磁気分布
- Paleomagnetic directions of the Aso pyroclastic-flow and the Aso-4 co-ignimbrite ash-fall deposits in Japan
- 山口県に分布する阿蘇4テフラの古地磁気方位
- 大谷女子大学博物館所有の考古地磁気測定装置と広域テフラの古地磁気研究について
- 阿蘇4火山灰および阿蘇火砕流堆積物の古地磁気方位
- 第四紀広域テフラの古地磁気方位
- 中部日本北部の鮮新〜更新世火山岩類の古地磁気
- 姶良Tnテフラの古地磁気方位
- 第4紀テフラの帯磁率
- 福井県中新世国見累層の古地磁気層序
- 考古地磁気年代推定試料の交流消磁実験
- 地磁気の逆転とエクスカーション
- Paleomagnetism of Miocene Rocks in the Western Area of Baragoi, Northern Kenya
- 福井県内浦層群の古地磁気
- 北陸地方の Miogypsina-Operculina 層準のフィッション・トラック年代
- 福井県第3系のフィッション・トラック年代
- 福井県丹生山地の河岸段丘堆積物の古地磁気
- 岡山・鳥取県に分布する大山上部火山灰層の古地磁気