Deep‐sea magnetic vector anomalies over the Hakurei hydrothermal field and the Bayonnaise knoll caldera, Izu‐Ogasawara arc, Japan

Honsho, Chie; Ura, Tamaki; Kim, Kangsoo

doi:10.1002/jgrb.50382

Cited by 41 publications

(47 citation statements)

References 30 publications

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“…Figures a and b show a 3‐D view of the Hakurei site from the northwest (no vertical exaggeration) and one overlain by the magnetization of the seafloor [ Honsho et al ., ], respectively. The magnetization values represent averages over depths of a few kilometers below the seafloor, not those of surface rocks.…”

Section: Geomorphological Features Of Calderamentioning

confidence: 99%

“…Topography of the Hakurei site. (a) Three‐dimensional view from northwest (no vertical exaggeration) and (b) that draped by the magnetization intensity (color scale and white contour lines) obtained from deep‐sea magnetic anomalies [ Honsho et al ., ]. (c) Topographic cross section along line AB shown in Figure 16a.…”

Section: Geomorphological Features Of Calderamentioning

confidence: 99%

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High‐resolution acoustic mapping to understand the ore deposit in the Bayonnaise knoll caldera, Izu‐Ogasawara arc

et al. 2015

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We collected deep‐sea multibeam, side scan, and subbottom profiler data using an autonomous underwater vehicle at the Bayonnaise knoll, a submarine caldera located in the rift zone of the Izu‐Ogasawara arc. We aimed to reveal topographic and geological features and the origin of a hydrothermal field called the Hakurei site in the caldera. We performed seafloor classification by textural analysis using calibrated side‐scan sonar data, which provided an effective means to understand the geology and to highlight potential areas of hydrothermal constructions. The high‐resolution bathymetric map illustrates that the Hakurei hydrothermal field is distributed over a landslide landform in the caldera wall. The distribution of hydrothermal vents indicates that the slip surface has served as a major route of hydrothermal fluids. The radial alignment of chimneys and mounds indicates radial routes of hydrothermal fluid and/or belching along fragile lines in the landslide landform. Various postcaldera activities are inferred including the formation of a lava dome, a pyroclastic cone, and subsequent phreatic explosions. A general volcano‐tectonic structure extending across the caldera in a NW‐SE direction is interpreted as an inferred boundary fault of the North Myojin Rift. Analogous to the Hokuroku basin and land kuroko deposits, it is suggested that the main contributing factor in the formation of kuroko deposits was volcano‐tectonic activity that dominated the margin of the back‐arc rift basin. The intersections between the margin of a rift basin and the surrounding knolls have a high potential for ore‐forming areas.

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Section: Geomorphological Features Of Calderamentioning

confidence: 99%

Section: Geomorphological Features Of Calderamentioning

confidence: 99%

High‐resolution acoustic mapping to understand the ore deposit in the Bayonnaise knoll caldera, Izu‐Ogasawara arc

et al. 2015

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“…The results of a deep sea magnetic survey, which was conducted using autonomous underwater vehicles, also revealed a high-magnetic anomaly on the caldera wall (Honsho et al 2010(Honsho et al , 2012(Honsho et al , 2013 This implies the existence of a fault in this part. Figure 4b presents a detailed bathymetry map around the Bayonnaise Knoll caldera that was constructed along the MCS survey line.…”

Section: Discussionmentioning

confidence: 96%

Structural characteristics of the Bayonnaise Knoll caldera as revealed by a high-resolution seismic reflection survey

et al. 2015

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The Bayonnaise Knoll caldera is a conical silicic caldera located on the eastern part of the back-arc rift zone of the Izu-Ogasawara arc. Many geological and geophysical surveys have shown that the Bayonnaise Knoll caldera contains hydrothermal sulfide deposits. The Japan Agency for Marine-Earth Science and Technology conducted high-resolution multi-channel seismic reflection surveys across the Bayonnaise Knoll caldera to ascertain details of the crustal structure, such as the configuration of faults around the caldera. A reflection profile of excellent quality was obtained by high-density velocity analysis at about 150-m intervals. We applied prestack depth migration by using the results of the high-density velocity analysis and further analyzed this region. The depth-migrated profile shows many faults, which correspond to bathymetric lineations, on the eastern side of the Bayonnaise Knoll caldera. The velocity structure of the Bayonnaise Knoll caldera resembles that of the Myojin Knoll caldera, which has been well surveyed and is associated with the hydrothermal deposit. The depth-migrated profile shows a clear reflective zone that is distributed asymmetrically to the Bayonnaise Knoll caldera center. These data suggest that caldera formation was controlled by back-arc rifting activity in the Izu-Ogasawara arc. The hydrothermal fluid migration path in the Bayonnaise Knoll caldera is estimated to be the result of faulting and magmatic intrusion on the eastern side of the structure. It is assumed that these fluids formed the Kuroko-type sulfide deposit in the eastern part of the caldera structure.

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“…The procedure used in this paper to remove the effects of the magnetic field of the AUV and its interaction with the Earth's magnetic field is similar to that used by [4]. It differs only in that the method presented here does not require the data to be placed in a geographic frame of reference prior to correction terms to be calculated, and that a correction for variable thruster motor currents is applied.…”

Section: Calibration Maneuvermentioning

confidence: 99%

“…Commercial ROV and AUV magnetic surveys are also used for undersea pipeline and cable inspections. Research surveys using AUVs in areas of hydrothermal vents and ocean ridges [3] [4] have utilized magnetic data to interpret the nature and geometry of the hydrothermal system beneath the seafloor. However, typically magnetic data is not collected during regular AUV and ROV operations, even when these vehicles are being used for mineral exploration.…”

Section: Introductionmentioning

confidence: 99%

Compensation of magnetic data for autonomous underwater vehicle mapping surveys

Bloomer

Kowalczyk

Williams

et al. 2014

2014 IEEE/OES Autonomous Underwater Vehicles (AUV)

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Magnetic surveying is well established in land based mineral exploration. Magnetic data is routinely used to map geology in covered terrains, to identify altered zones, mineralization, bedding attitudes, and fault networks. However, other than during specialized commercial, military, and academic surveys, magnetic data is not normally collected on autonomous underwater vehicles (AUVs) and remotely operated vehicles (ROVs) conducting geological mapping and hydrographic survey operations.One reason for this is the magnetic field produced by the local geology is often overwhelmed by the heading and attitude dependent magnetic fields of the vehicle when the magnetometer is mounted close to or inside the AUV. Magnetometers can be mounted away from the AUV with specialized mounting apparatus e.g. a towed body or pole-mounts, but at the cost of increased complication to operations and risk to vehicle safety. To produce useful data from a magnetometer mounted inside the body of an AUV, it is necessary to compensate not only for the attitude of the AUV in the earth's field, but also for secondary effects related to the strength of the electric currents flowing in the vehicle propulsion and vehicle control circuits.To calculate the compensation terms, both a physical calibration routine and a mathematical treatment of the data are required. Prior to each survey, flying a short calibration maneuver enables the calculation of correction terms to the raw magnetic data. The calibration maneuver consists of two sequential, coincidental squares of four calibration legs per square. These squares are flown in opposite directions with the sides of the squares aligned parallel with the primary survey and tie lines. The AUV is typically flown in terrain following (constant altitude) mode at the nominal altitude of the survey, but is changed during each leg to induce pitch into the flight of the AUV. Correction terms are then calculated from the calibration magnetic field data, AUV attitude and heading and vehicle control data. Applying these correction terms to the raw magnetic data collected during the survey produces very useful magnetic maps for interpreting regional, subsurface geology in the survey area. As shown in this paper, OFG has successfully demonstrated this process in commercial surveys.

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Deep‐sea magnetic vector anomalies over the Hakurei hydrothermal field and the Bayonnaise knoll caldera, Izu‐Ogasawara arc, Japan

Cited by 41 publications

References 30 publications

High‐resolution acoustic mapping to understand the ore deposit in the Bayonnaise knoll caldera, Izu‐Ogasawara arc

High‐resolution acoustic mapping to understand the ore deposit in the Bayonnaise knoll caldera, Izu‐Ogasawara arc

Structural characteristics of the Bayonnaise Knoll caldera as revealed by a high-resolution seismic reflection survey

Compensation of magnetic data for autonomous underwater vehicle mapping surveys

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