R/V POSEIDON Cruises 252/253 (1999)
Preface The cruises 252 and 253 of RV "Poseidon" were performed for a common project on the investigation of hydrothermal activities in the area of the Tjoernes-Fracture-Zone north of Iceland. The main objectives were focussed on the invest igation of the structure and morphology of hydrot...
| Other Authors: | , , |
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| Format: | Report |
| Language: | English |
| Published: |
Institute for Geosciences, Departments of Geophysics and Geology/Palaeontology
2000
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| Subjects: | |
| Online Access: | https://oceanrep.geomar.de/id/eprint/41779/ https://oceanrep.geomar.de/id/eprint/41779/1/Poseidon252.pdf |
| Summary: | Preface The cruises 252 and 253 of RV "Poseidon" were performed for a common project on the investigation of hydrothermal activities in the area of the Tjoernes-Fracture-Zone north of Iceland. The main objectives were focussed on the invest igation of the structure and morphology of hydrothermal vents. Multichannel reflection seismic investigations were performed during the first leg as a pre-site survey for the subsurface structures beneath recent hydrothermal vents and the seismic characterisation of the seafloor, whereas the second leg was dedicated to the investigation of the morphology in the vent areas using cores and the research submersible "JAGO". The main strategy of the combination of a geophysical and a geological / geochemical cruise leg was to illustrate the relationships between heat sources in the subsurface and the formation of vent fields at the sea floor in order to get a more comprehensive understanding of the dynamic processes of fluid circulation and the formation of the uppermost sediments. Two reflection seismic sections show clearly the position of a magma chamber beneath a vent field thus indicating the energy source which is driving the thermal fluid circulation in the overlying sediments that showed quite clearly when cores were heaved on board and they were still boiling. The combined interpretation of the data shows a clear correlation between phase reversals in seismic response and high gas accumulations as well as anhydrite in cores and expected seismic reflections coefficients of this sampled material. Thus combination of geophysical and geological methods have prooven that reflection seismic investigations can reveal sea floor characterisics and their spatial distributions after calibration by groundtruthing in a very effective way. For future cruises a complete bathymetric survey should be included in the research programme as many subsurface features are imaged in the bottom morphology of the sea floor. |
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