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RRS James Cook JC024
Cruise summary report
Cruise Info. | |
Ship name (ship code) | RRS James Cook (740H) |
Cruise identifier | JC024 |
Cruise period | 2008-05-23 — 2008-06-28 |
Status | Completed |
Port of departure | Ponta Delgada, Portugal |
Port of return | Southampton, United Kingdom |
Purpose | Research |
Objectives | Objectives
1. To determine the life cycle of an AVR (estimates range from 10ka to 500ka). 2. To test whether the AVR ha a common parental magma derived from a single pulse of mantle melt. 3. To test whether AVRs develop systematically with an evolving volcanic style (e.g., sheet flows > pillow ridges > central volcanoes). 4. To determine how, if at all, these different volcanic components are linked. Are they derived successively from separate magma reservoirs? Are lateral terraces fed from axial vents? 5. To examine whether effusion rate and volume vary with time during AVR development. Are they reflected in volcanic style, run-out length and eruptive position within the AVR? Summary JC24 involved the first use of the ROV Isis on an active mid-ocean ridge axis. We departed Ponta Delgada on 23 May 2008 and finished in Southampton on 28 June. A breakdown of the Isis winch on 9 June required us to return to Ponta Delgada to pick up a spare part, involving a loss of four days. Altogether, we spent approximately 9.5 days on passage and 26.5 days on station at 45° 30'N, including one day lost due to bad weather. We completed a 6-day TOBI survey extending approximately 30 km along axis, completely insonifying the AVR with both north- and south-looking sidescan and phase data and obtaining three-component magnetic data on 22 E-W tracks spaced 1.5 km apart. Ship-based EM120 multibeam echosounder and gravity data were logged throughout the cruise, and sea-surface magnetometer was logged during the passage to and from the study area and during the TOBI survey. Eleven Isis sampling and video imaging dives were completed, and a further two dives carried out detailed bathymetry surveys. 270 rock samples were acquired. A WHOI three-component magnetometer was carried on all Isis dives. The sidescan data were fully processed on board. In addition to the expected hummocky and flat-topped volcanoes, they revealed a number of lateral hummocky |
Chief scientist | Roger C Searle (University of Durham, Department of Earth Sciences) |
Cruise report | (5.58 MB) |
Ocean/sea areas | |
General | North East Atlantic Ocean (limit 40W) |
Specific | Mid-Atlantic Ridge |
Track charts | (0.43 MB) |
Measurements | |
Physical oceanography | |
Other physical oceanographic measurements | Quantity: activity duration in hours = 234 Description: ISIS MAPR data |
Other physical oceanographic measurements | Quantity: activity duration in hours = 31 Description: Tow-yo MAPR (Miniature Autonomous Plume Recorder) data, used for detecting hydrothermal plumes |
Biology and fisheries | |
Other biological/fisheries measurement | Quantity: number of samples = 37 Description: Coral samples, for shore-based DNA analysis |
Geology and geophysics | |
Bottom photography | Quantity: number of images = 9788 Description: ISIS still photos |
Bottom photography | Quantity: activity duration in hours = 234 Description: ISIS video |
In-situ seafloor measurement/sampling | Quantity: number of samples = 272 Description: Rock samples, half of each to each PI, to be used for shore-based major- and trace-element geochemistry and U-series dating |
Geophysical measurements made at depth | Quantity: survey square kilometres = 1200 Description: TOBI LSS (Light Scattering Sensor) data |
Geophysical measurements made at depth | Quantity: survey square kilometres = 8 Description: ISIS 3-component magnetics |
Geophysical measurements made at depth | Quantity: survey square kilometres = 1200 Description: TOBI magnetics (3 component) |
Multi-beam echosounding | Quantity: survey square kilometres = 8 Description: ISIS MS2000 high-resolution bathymetry |
Multi-beam echosounding | Quantity: survey square kilometres = 1200 Description: Ship-mounted EM120 with multibeam bathymetry |
Long/short range side scan sonar | Quantity: survey square kilometres = 1200 Description: TOBI sidescan sonar |
Gravity measurements | Quantity: survey square kilometres = 1200 Description: Ship-based gravity |
Magnetic measurements | Quantity: survey square kilometres = 1200 Description: Sea-surface magnetics |
Other geological/geophysical measurements | Quantity: survey square kilometres = 1200 Description: TOBI phase bathymetry |