Deep‐sea magnetic vector anomalies over the Hakurei hydrothermal field and the Bayonnaise knoll caldera, Izu‐Ogasawara arc, Japan
Deep‐sea magnetic vector anomalies over the Hakurei hydrothermal field and the Bayonnaise knoll caldera, Izu‐Ogasawara arc, Japan
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DOI：
10.1002/jgrb.50382
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发表时间：
2013-10
期刊：
影响因子：
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通讯作者：
C. Honsho;T. Ura;Kangsoo Kim-
中科院分区：
文献类型：
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作者：
C. Honsho;T. Ura;Kangsoo Kim-
我们使用自主水下航行器在Bayonnaise小山丘破火山口、伊豆-小笠原岛弧进行了深海磁场测量，该岛弧拥有大型的Hakurei热液田。改进了传统的校正方法，消除了车辆磁化的影响，从而大大提高了矢量异常的精度。从矢量异常数据中获得的磁化分布显示，有一个宽约1.2 km的高磁化带，走向为NNW-SSE，穿过破火山口，还有一个面积为1.300 m × 1.500 m的低磁化带，延伸到Hakurei现场。通过对矢量异常和总强度异常结果的比较表明，矢量异常比总强度异常能更准确地确定磁场，特别是在数据分布稀疏的地区。我们提出了一个地质动机模型，即与弧后裂谷相关的玄武质火山活动发生在破火山口形成之后，导致破火山口下方形成高磁化带。白井热液场位于玄武质火山活动带和破火山口壁断层的交汇处，表明火山活动产生的热量产生的热水通过破火山口壁断层喷出的机制。存款显然延伸到低磁化区之外，爬上破火山口壁。这可能表明，从深部上升通过蚀变带的热水在接近海底时，沿沿着破火山口壁的裂缝和断裂被横向输送。
We conducted deep‐sea magnetic measurements using autonomous underwater vehicles in the Bayonnaise knoll caldera, the Izu‐Ogasawara island arc, which hosts the large Hakurei hydrothermal field. We improved the conventional correction method applied for removing the effect of vehicle magnetization, thus greatly enhancing the precision of the resulting vector anomalies. The magnetization distribution obtained from the vector anomaly data shows a ∼2 km wide belt of high magnetization, trending NNW‐SSE going through the caldera, and a low‐magnetization zone ∼300 m by ∼500 m in area, extending over the Hakurei site. Comparison between the results obtained using the vector anomaly and the total intensity anomaly shows that the magnetic field is determined more accurately, especially in areas of sparse data distribution, when the vector anomaly rather than the total intensity anomaly is used. We suggest a geologically motivated model that basaltic volcanism associated with the back‐arc rifting occurred after the formation of the caldera, resulting in the formation of the high‐magnetization belt underneath the silicic caldera. The Hakurei hydrothermal field lies in the intersection of the basaltic volcanism belt and the caldera wall fault, suggesting a mechanism that hot water generated by the heat of the volcanic activity has been spouting out through the caldera wall fault. The deposit apparently extends beyond the low‐magnetization zone, climbing up the caldera wall. This may indicate that hot water rising from the deep through the alteration zone is transported laterally when it comes near the seafloor along fissures and fractures in the caldera wall.