RRS James Cook JC228
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | RRS James Cook (740H) |
| Cruise identifier | JC228 |
| Cruise period | 2022-12-03 — 2023-01-09 |
| Status | Completed |
| Port of departure | Caldera, Costa Rica |
| Port of return | Caldera, Costa Rica |
| Purpose | Research |
| Objectives | The formation, evolution, subduction, and recycling of oceanic lithosphere is a fundamental tenet of plate tectonics. This cycle is the primary mechanism for thermal and chemical exchanges between the solid Earth and the hydrosphere. In collaboration a German-UK consortium conducted an integrated geophysical and geological study during the barter cruise JC228 aboard the British RRS JAMES COOK, sampling fast-spreading ocean lithosphere of the northern Cocos Plate from its formation to subduction in the Mid-America Trench. We collected seismic reflection (MCS) and refraction (WAS) data along a linear transect with grids in three focus areas; two were on the passively cooling oceanic plate, the third spanned the transition into the subduction zone. There, faults that form as the plate bends allow seawater to penetrate through the crust and into the upper mantle and thereby hydrate mantle just before it subducts. Fluid flow associated with these plate bending faults were investigated using geophysical and pore water data, including high-resolution bathymetry, heat flow and coring. The cruise JC228 is going to deliver key information on the evolution of oceanic lithosphere as well as provide essential site survey information for two IODP Proposals: the flagship MoHole to Mantle initiative (M2M; IODP-805MDP) and the Bend Fault Serpentinization experiment (approved IODP-876Pre).
The cruise was split into two legs due to the amount of equipment needed exceeding what can be handled on board the RRS James Cook, with a mid-cruise port call at Caldera. JC228 collected MCS and WAS data. JC228A collected cores and heatflow data, with two unsuccessful attempts to deploy Autosub 5. |
| Chief scientist | Ingo Grevemeyer (GEOMAR Helmholtz Centre for Ocean Research, Kiel (East Shore Campus)), Ingo Klaucke (GEOMAR Helmholtz Centre for Ocean Research, Kiel (East Shore Campus)) |
| Project | MoHole to Mantle initiative; Bend Fault Serpentinization experiment |
| Ocean/sea areas | |
| General | North East Pacific Ocean (limit 180W) |
| Specific | Guatemala Basin |
| Track charts |  (3.15 MB) |
| Measurements | |
| Physical oceanography | |
| Surface measurements underway (T,S) | Quantity: activity duration in days = 53 Description: Underway surface water sampling, standard NMF suite |
| Bathythermograph | Quantity: number of stations = 19 Description: T7 XBTs |
| Other physical oceanographic measurements | Quantity: number of stations = 2 Description: Sound velocity profiles, Valeport MIDAS SVP |
| Meteorology | |
| Routine standard measurements | Quantity: activity duration in days = 53 Description: Standard NMF Met observations |
| Geology and geophysics | |
| Core - soft bottom | Quantity: number of cores = 16 Description: Gravity cores, 3-12m barrel length |
| In-situ seafloor measurement/sampling | Quantity: number of stations = 64 Description: Heatflow stations |
| Single-beam echosounding | Quantity: track kilometres = 9650 Description: Kongsberg EA640 single beam echo sounder |
| Multi-beam echosounding | Quantity: survey square kilometres = 47500 Description: Kongsberg EM122 12kHz multibeam echo sounder recording depths and backscatter |
| Single channel seismic reflection | Quantity: track kilometres = 9470 Description: Kongsberg SBP27 Sub-bottom profiler |
| Multichannel seismic reflection | Quantity: track kilometres = 1575 Description: MCS recorded on Sercel Seal, mostly 6km streamer, some 3km streamer. Note the distance here excludes turns, although shooting continued since the data were recorded by the OBS |
| Seismic refraction | Quantity: number of stations = 96 Description: OBS deployments - mixture of instruments from GEOMAR and OBIC |
| Gravity measurements | Quantity: track kilometres = 10050 Description: S84 Gravity meter (Note, this instrument recorded data strongly suggesting that it is broken, and it should not be regarded as reliable) |
| Gravity measurements | Quantity: track kilometres = 10050 Description: AT1M Gravity meter |
| Magnetic measurements | Quantity: track kilometres = 6510 Description: Seaspy magnetometer |
