RRS James Cook JC138
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | RRS James Cook (740H) |
| Cruise identifier | JC138 |
| Cruise period | 2016-07-08 — 2016-08-24 |
| Status | Completed |
| Port of departure | Ponta Delgada, Portugal |
| Port of return | Falmouth, United Kingdom |
| Purpose | Research |
| Objectives | Cruise JC138 was designed to test several technologies and acquire data about the geological processes associated with the formation and preservation of extinct seafloor massive sulphide (eSMS) deposits on the seafloor. The aims of cruise JC138 were two fold: to demonstrate technologies for the exploration and assessment of extinct seafloor massive sulphides (eSMS) and to understand the formation, alteration and preservation of eSMS deposits after high-temperature fluid flow has ceased. Our methodology included the use of a variety of electromagnetic survey instruments (DASI, Vulcan, Sputnik and Martamis) , a robotic underwater vehicle (HyIS), a robotic seafloor rock drill (RD2) and gravity, mega and box coring (for the sediments).
Our chosen study area was the TAG segment of the Mid-Atlantic Ridge at 26°N; 44°W. Here, several eSMS deposits were already known, as well as the active TAG hydrothermal field. The known eSMS mounds are 100-200m in diameter and up to 60 m high. These include: Shinkai Mound, Southern Mound, Double Mound, and the MIR zone. Previous work had shown Shinkai and Double mounds to be steep and unsuitable for our studies, whereas Southern Mound and the MIR zone were found to be more prospective due to their subdued topography and roughness. Following the previous Blue Mining cruise, RV Meteor cruise M127 (May-June 2016), where an AUV (Abyss) was used to map the area in high resolution (2m to 50cm), a further number of eSMS mounds were discovered, the most prospective being a dome-shaped body ~100m in diameter and ~30m high, we called Rona Mound. Overall, cruise JC138 occupied 77 stations over 32.2 science days, for which 72% of the time was employed successfully while 28% of the time was beset with technical difficulties. Of these operations, DASI, HYBIS and the coring operations were the most reliable, followed by Sputnik, COIL and the OBEM's. The RD2 was the least reliable with 16 of the 23 deployments failing due to technical issues before drilling. This constitutes, by number of deployments, a 30% success rate of the RD2 seafloor robotic drilling system. A total of 9.7m of drill core was recovered from 6 holes with a maximum depth of 12.7mbsf; 13 sediment cores were acquired with a total of 17m from a maximum depth of 2.3mbsf, 31 individual HyBIS samples were collected, one complete DASI/Vulcan survey and two COIL/Martamis surveys occupied over the entire TAG area. |
| Chief scientist | Bramley J Murton (National Oceanography Centre, Southampton) |
| Cruise report |  (163.54 MB) |
| Ocean/sea areas | |
| General | North West Atlantic Ocean (limit 40W) |
| Specific | Mid-Atlantic Ridge |
| Track charts | (1.05 MB) |
| Measurements | |
| Physical oceanography | |
| Surface measurements underway (T,S) | Quantity: activity duration in days = 56 Description: The Surfmet system was run throughout the cruise. |
| Current profiler (eg ADCP) | Quantity: activity duration in days = 56 Description: Both the 75 kHz and 150 kHz ADCP systems were run during the cruise although not requested. To summarise the configuration, the 75 kHz was run in broadband mode with 48 bins of 16 m with an 8 m blank. The 150 kHz was run in narrowband mode with 96 bins of 4 m with an 4 m blank. Bottom tracking was enabled on the run into port to allow the orientation of the transducers to be calibrated. |
| Other physical oceanographic measurements | Quantity: activity duration in days = 46 Description: The Sonardyne USBL system was used to track every deployment.?A WSM beacon was configured with address QSY1 with power and gains set to high and installed in a cable clamp and kept charged and serviceable, this was used for the Gravity Core, Mega Core, OBEM deployment and Coil experiment. |
| Geology and geophysics | |
| Core - rock | Quantity: number of samples = 76 Description: Hard rock samples from RD2 drill core |
| Core - rock | Quantity: number of samples = 33 Description: Hard rock samples from HyBIS RUV |
| Core - soft bottom | Quantity: number of stations = 2 Description: Soft sediment drill cores |
| Core - soft bottom | Quantity: number of stations = 13 Description: Soft sediment gravity cores |
| Core - soft bottom | Quantity: number of stations = 2 Description: Soft sediment multi cores |
| Single-beam echosounding | Quantity: activity duration in days = 56 Description: The EA600 single-beam echo-sounder was run throughout the cruise while in international waters. All depths were logged to the Techsas and Level-C data loggers and raw files in raw Kongsberg .all format. |
| Multi-beam echosounding | Quantity: activity duration in days = 1 Description: The EM710 multi-beam echo sounder was run at the end of the cruise while shallow waters. Data was logged in Kongsberg .all format. |
| Multi-beam echosounding | Quantity: activity duration in days = 50 Description: The EM120 multi-beam echo sounder was run throughout the cruise while in international waters. Data was logged in Kongsberg .all format. The centre beam depth was logged to Techsas and Level-C. |
| Single channel seismic reflection | Quantity: activity duration in days = 56 Description: The SBP120 Sub Bottom Profiler was run throughout the cruise while in international waters. There are breaks in the data due to the acoustic instrumentation being isolated during OBEM deployment and recovery. Data was recorded in Kongsberg raw format and in Seg-Y format. |
| Moorings, landers, buoys | |
| Geology and geophysics | |
| Grab | 26° 9' 29" N 44° 49' 0" W — Sixty hours of HyBIS robotic underwater vehicle video survey and rock sampling |
| Core - rock | 26° 9' 29" N 44° 49' 0" W — 384 hours of seafloor drilling (using the BGS' RD2 drill-rig) into massive sulphide mounds |
| Core - soft bottom | 26° 9' 29" N 44° 49' 0" W — Fifty four hours of gravity coring into soft sediments |
| Bottom photography | 26° 9' 29" N 44° 49' 0" W — Sixty hours of HyBIS robotic underwater vehicle video survey and rock sampling |
| Bottom photography | 26° 9' 29" N 44° 49' 0" W — Two days of HyBIS RUV hyperspectral image surveying |
| In-situ seafloor measurement/sampling | 26° 9' 29" N 44° 49' 0" W — Thirty six hours of COIL (active source electromagnetic coil transceiver) survey |
| In-situ seafloor measurement/sampling | 26° 9' 29" N 44° 49' 0" W — Two days of SPUTNIK (active source electromagnetic transmitter) survey |
| In-situ seafloor measurement/sampling | 26° 9' 29" N 44° 49' 0" W — Re-deployment of three OBEM. |
| In-situ seafloor measurement/sampling | 26° 9' 29" N 44° 49' 0" W — Deployment of six ocean bottom electromagnetic receivers (OBEM) |
| In-situ seafloor measurement/sampling | 26° 9' 29" N 44° 49' 0" W — Three days of DASI (deep active source instrument) electromagnetic transmitter survey |
