| 講演要旨(和文) | | 電気・電磁探査法を，海底熱水鉱床の調査に適用するにあたって，探査の指標となる電気・磁気的特性の把握が不可欠である．本研究では，沖縄トラフ海域の伊是名海穴と伊豆・小笠原海域のベヨネーズ海丘の鉱床の鉱石の比抵抗と充電率および帯磁率の測定を行い，X線回折分析，蛍光X線分析，微量元素分析，肉眼及び偏光顕微鏡観察結果と合わせて，探査指標としての検討を行った．海底熱水鉱床の鉱石は海域によって比抵抗の範囲は異なるが，海域によらず高い充電率を示した．分析の結果より，比抵抗の違いは結晶性鉱物の含有率の違いによるものと考えられ，開発対象品位が決定すれば，品位に対応した電気的特性を設定することができる事が示唆された．さらに海底熱水鉱床サンプルを使用した電気探査水槽実験を行い，充電率異常をとらえることができた．帯磁率測定では，伊是名海穴でFeの含有率に比例して，高い帯磁率を示した。 |
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| | 講演要旨(英文) | | Electric and Electromagnetic exploration technologies are prevailing for the onshore mineral deposits due to the significant differences of the electric properties. The electric and magnetic properties such as resistivities, chargeabilities and magnetic susceptibilities of the ocean bottom samples from Bayonnaise Knoll and Izena Cauldron are measured and analyzed using XRD, XRF and ICP-MS. Mineral compositions are determined also with visual and reflecting microscope observations. The resistivity values from the Izena samples range from 0.1 to several ohm-ms, while those from Bayonnaise range from 1 to several 10s of ohm-ms, while chargeability values are found to be high for those two areas. The results of our resistivity measurements show good agreements with the mineral composition obtained from the XRD analysis and the differences between those 2 areas can be explained. From the results of ICP-MS analysis, Au and Ag contents are practically no differences between Bayonnaise Knoll and Izena Cauldron, but associate with Zn and Pb. The water tank experiments using the seabed mineral samples showed high chargeability values in the conducting environments. The magnetic susceptibilities of the ore samples from Izena Cauldron are higher than those from Bayonnaise Knoll, and proportional to the Fe contents. |
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