RRS James Cook JC007
Cruise summary report
|Ship name (ship code)||RRS James Cook (740H)|
|Cruise period||2007-03-05 — 2007-04-17|
|Port of departure||Santa Cruz de Tenerife, Spain|
|Port of return||Santa Cruz de Tenerife, Spain|
|Objectives||The three key objectives of our original proposal were to test:
1. The hypothesis that mantle upwelling and melting is focused at the centres of slow spreading ridge segments and transposed by sub-horizontal flow away from there.
2. The hypothesis that plate accretion and separation mechanisms are fundamentally different in 'magma-starved' areas.
3. Mechanisms of detachment faulting and extensional strain localisation in the lower crust and upper mantle.
We proposed to achieve these objectives by detailed surveying and sampling across an extensive region of magma-poor seafloor spreading around Fifteen Twenty Fracture Zone (FTFZ), coupled with microstructural, geochemical and palaeomagnetic analyses. TOBI deep-towed sidescan and magnetic data were to be obtained both to inform the choice of sampling sites and to aid in structural, lithological and geodynamic interpretations.
We spent 29 days on the Mid-Atlantic Ridge (MAR) in the vicinity of 13 to 15N. We collected multibeam ship-based bathymetry, gravity and magnetic data and TOBI sidescan, magnetic and water-column data from a total area of about 8,000 km2. We recovered samples from 47 drill and dredge stations throughout the area, in support of the objectives.
|Chief scientist||Roger C Searle (University of Durham, Department of Earth Sciences)|
|Cruise report||(9.57 MB)|
|General||North Atlantic Ocean|
|Specific||Tropical North Atlantic|
|Track charts||(0.16 MB)|
|Subsurface temperature and salinity measurements||Quantity: activity duration in days = 11|
Description: TOBI deep-towed continuous CTD measurements
|Geology and geophysics|
|Dredge||Quantity: number of hauls = 30|
Description: Dredge hauls recovering a variety of rock types
|Core - rock||Quantity: number of cores = 7|
Description: 7 oriented 8 unoriented rock cores using BGS oriented rock drill (''BRIDGE" drill)
|Geophysical measurements made at depth||Quantity: activity duration in days = 11|
Description: TOBI deep-towed continuous 3-component magnetic field data
|Multi-beam echosounding||Quantity: activity duration in days = 40|
Description: Simrad EM120 multibeam echosounding, depth and backscatter data.
|Long/short range side scan sonar||Quantity: activity duration in days = 11|
Description: TOBI deep-towed 30 kHz sidescan sonar, 6 km swath width
|Gravity measurements||Quantity: activity duration in days = 42|
Description: Continuous gravity measurements with LaCoste & Romberg marine meter S-75, tied to Earth Gravity Network stations in Tenerife
|Magnetic measurements||Quantity: activity duration in days = 20|
Description: Continuous measurements on passage and in survey area