Plattform Platform	Reise-Nr. Cruise-No.	Zeitraum Period	Projekt Project	Arbeitsgebiet Working area
Pelagia	INDEX2021	09.10.2021 - 29.12.2021	INDEX	Indian Ocean

Fahrtleiter Chief Scientist	Institut Institute	Auslaufhafen Port of departure	Einlaufhafen Port of return	Stationskarte Station map	Schiffsroute Trackchart
Barckhausen Udo	Bundesanstalt fur Geowissenschaften und Rohstoffe, Hannover	Port Louis	Port Louis

Ziel der Reise / Objectives of Cruise:

The expedition INDEX 2021 with the Dutch RV Pelagia took place from October 9th through December 29th, 2021 as part of BGR's program for the exploration of massive sulphides in the Indian Ocean. It was scheduled into three legs: Leg 1 was dedicated to geophysical work, Leg 2 focussed on regional exploration and regional environmental investigations, and Leg 3 was reserved for local work mainly with ROV ROPOS. All legs started and ended at the harbour of Port Louis, Mauritius. Apart from BGR personnel, the cruise was supported by personnel from Helmholtz Center for Ocean Research Geomar Kiel, University of Hamburg, HafenCity University Hamburg, DZMB Senckenberg Am Meer Wilhelmshaven and INES, Laurentian University Sudbury (Canada), the Royal Dutch Institute for Sea Research (NIOZ), and the Canadian Scientific Submersible Facility (CSSF). Moreover, one ISA trainee from Mauritius and one from India could take part in Leg 1. Leg 1 was dedicated to the geophysical investigation of two large hydrothermal areas with massive sulphide deposits in cluster 12. The electromagnetic profiler GOLDEN EYE was used for a systematic mapping of the magnetic and electric properties of the sub-surface along densely spaced survey lines over the known massive sulphide occurrences and their surroundings. In addition, very high resolution deep-tow bathymetry surveys in combination with magnetic and self-potential mapping were carried out. Two newly acquired passive electromagnetic Vulcan receivers were towed astern of the HOMESIDE deep-tow instrument just 30 - 80 m above the seafloor with good success. The measurements were complimented with a profile of heatflow measurements between the two fields and continuous gravity data acquisition throughout the leg. 132 hours of seafloor video observations provided by cameras mounted on the GOLDEN EYE were used by the marine biologists to complete a systematic assessment of marine fauna in the entire HUNA-PENUMBRA area. The focus of our work on Leg 2 was the recovery and re-deployment of six sediment trap moorings throughout the contract area, the detection of locations with increased hydrothermal potential based on high-resolution HOMESIDE bathymetry and mineral potential mapping, and the optical mapping of hydrothermal fields. At least four new locations with increased potential for the occurrence of sulphide mineralisation could be detected. In addition, we were able to obtain numerous water and sediment samples for biological and geological work. Local investigations carried out during Leg 3 with ROV ROPOS were realized at different hydrothermal fields. Geological mapping, sampling, and drilling at various hydrothermal fields showed that their sulphide mounds have different morphologies and surface characteristics. One major objective of Leg 3 was the first application of the ROV-mounted drill tool ROCS. It has been shown that massive sulphides can be reliably drilled with ROCS. As long as there is no lithology change, extraordinarily high recovery rates of up to 80 % were achieved. Altered rocks could be drilled to a limited extent and with significantly lower recovery rates. Low-temperature, hydrothermal precipitates (Fe-oxide crusts, solidified Si-rich sediments) as well as hydrothermal weathering products could not be recovered with ROCS in most tests. Biological investigations during Leg 3 focussed on ROV sampling.

Messungen / Measurements

Verankerungen / Moorings