Manned submersible studies have delineated a large and actively growing Kuroko-type volcanogenic massive sulfide deposit 400 kilometers south of Tokyo in Myojin Knoll submarine caldera. The body is located on the caldera floor at depth 1210 to 1360 meters, has an area by 30 notably rich gold silver. discovery polymetallic this arc-front raises possibility that numerous unexplored silicic calderas elsewhere might similar deposits.

Research Article| July 01, 2001 Submarine silicic caldera at the front of Izu-Bonin arc, Japan: Voluminous seafloor eruptions rhyolite pumice Richard S. Fiske; Fiske 1Department Mineral Sciences, National Museum Natural History, Smithsonian Institution, Washington, DC 20560, USA Search for other works by this author on: GSW Google Scholar Jiro Naka; Naka 2Deep Sea Department, Japan Marine Science and Technology Center, Yokosuka 237, Kokichi Iizasa; Iizasa 3Marine Geology Geological Survey...

Abstract Considerable effort has been expended in studying the Izu–Bonin Arc over past 15 years. In particular, 43 dives of Shinkai 2000 have undertaken there to discover and evaluate extent submarine hydrothermal activity mineralization. Most focused on Myojin Knoll (23 dives), Suiyo Seamount (6 Kaikata Caldera (10 dives). The is divided two by Sofugan Tectonic Line. Eight caldera are located north this line but only one south it. physiography northern sector arc quite different from that...

We have developed an underwater gravity measurement system that uses autonomous vehicle (AUV) for exploration of seafloor mineral deposits. An improved air/sea gravimeter mounted on a gimbal mechanism in pressure capsule 50 cm diameter was installed the AUV Urashima. carried out 11 dives Sagami Bay as well deep-sea deposit areas offshore Japan. The navigated at constant speed 2 knots and either depth or altitude above sea bottom. obtained high-resolution Bouguer anomaly data through...

It is known that there are mineral deposits below seafloor. Gravity survey one of powerful methods for exploration underground deposits. A new system needed to a wide area quickly with higher resolution. Recent technology an autonomous underwater vehicle (AUV) enables us measure gravity in environment. We have developed measurement seafloor using AUV. Our consists gravimeter and gradiometer. The resolution approximately 0.1 mgal 10 Eötvös gradient required the exploration. For system, we...

Recently, hydrothermal deposits below the seafloor are believed to be useful for human activity. Because size of each deposit is much smaller than that an offshore oil field, detailed exploration position and estimated mass needed. An underwater gravity survey just above can directly give localized distribution seafloor. Therefore, we have developed measurement system onboard autonomous vehicle (AUV), which suitable wide area surveys close with high resolution. improved gravimeter was...

A huge hydrothermal field of 500 by 700 m across associated with a modern analogue Kuroko-type deposit was first found in the Bayonnaise knoll caldera nascent rift zone westward volcanic front Izu-Ogasawara (Bonin) island arc, Japan during April 2003 Hakurei-maru No.2 cruise since two major deposits had been reported on front. The dacite post-caldera dome has slightly ellipsoidal rim 3 2.5 km wide about 200 relief, and its floor is 840-920 below sea level. field, which occurs between water...

Gravity surveys are useful for profiling underground density structures. We propose a hybrid gravity survey method using gravimeters and gradiometers to detect submarine ore deposits, such as massive sulfides buried below the seafloor. This paper describes gradiometer, which can be implemented in an AUV (Autonomous Underwater Vehicle) this purpose. developed new gradiometer comprising of two vertically separated accelerometers with astatic reference pendulums, whose motions precisely...

We are developing a hybrid gravity survey system using gravimeter and gradiometer to sub-seafloor density structure. This paper describes the development of with forced gimbals for this purpose. The aimed precision is about 0.1 mgal, one order better than sea surface gravimetry. After successful feasibility study by Scintrex CG-3M under condition pitching rolling as well heaving, we new underwater sensor Micro-G LaCoste. design, performance, future tasks described.

Gravity surveys are useful in profiling the underground density structure. We propose a hybrid gravity survey method using gravimeters and gradiometers to detect submarine ore deposits. This paper describes development of gradiometer for this purpose. The required resolution is estimated be finer than approximately 10 E (= 1 × <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> /s xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ),...

Gravity survey is one of powerful methods for exploration mineral deposits. Recent technology an autonomous underwater vehicle (AUV) enables us to quickly a wide area in environment with high resolution. We have developed gravity measurement system seafloor deposits using AUV. Our consists gravimeter and gradiometer. A model calculation shows that the resolution approximately 0.1 mgal 10 Eötvös (E) gradient required detect typical deposit. For system, we adopted improved sea/air sensor...

We developed an underwater gravimeter for exploration of a seafloor hydrothermal deposit. Our hybrid system consists and gravity gradiometer. adopted Micro-g LaCoste S-174 as sensor. The sensor is mounted on gimbal mechanism with fiber gyroscope. A titanium sphere contains the system. Maximum depth rating 4,200 m. data are sent to recording housed in another cylinder-shape capsule. whole controlled monitored via acoustic link AUV. In September 2012, first practical measurement marine area...

In August 2005, we succeeded in operating AUV "r2D4", which was constructed July 2003 as one of fruits R-Two project, into Myojin-sho underwater Caldera full autonomous mode. The caldera is located about 800 km the south Tokyo, and 8 diameter. There an active volcano at Northeastern part outer rim caldera, erupted repeatedly 1952. Kuroshio current usually running over Caldera, so that speed around it sometimes more than 3 knots. It can be said diving human occupied vehicle remotely operated...

Pavements of manganese nodules and crusts outcrops Miocene limestones were observed on the flanks flat top Tenpo Seamount during three Shinkai 2000 dives. The pre‐Miocene volcano supplied nuclei volcanic rocks hydrothermal deposits, subsequent slow or no sedimentation promoted deposition abundant hydrogenetic crusts, mainly upper flank seamount. Nodule pavements generally cover calcareous sand surface sediments, while hard composed probably rocks. fields are sparsely distributed with each...

We develop an effective method for exploring seafloor hydrothermal deposits using acoustic apparatus. The important thing exploration is to carry out the efficiently detailed after narrowing down a promising area from vast by wide-area exploration. Here, we aim establish such method, examining methods obtaining bathymetric data and normalization of backscattering strength. Compared conventional methods, density increased in both transverse traveling directions swath width dropping vessel...