NEW VENTS · New Zealand Cold Vents: Integrative petrographical, geochemical and geophysical investigations on active marine vents and fossil vents on land

Final Activity Report Summary - NEW VENTS (New Zealand Cold Vents: Integrative petrographical, geochemical and geophysical investigations on active marine vents and fossil vents on land)

The research focus of the Marie Curie action NEW VENTS was the study of marine methane-seep sites offshore New Zealand. These methane seeps were areas at which fluids were expelled from the seafloor due to dewatering caused by sediment compaction, reactions of minerals and organic matter in the sediment and tectonic stress. The released pore water transported geochemical components, such as hydrogen sulphide (H2S), methane (CH4), ammonium (NH4) and barium (Ba) towards the sea surface and caused microbially mediated reactions when these fluids came into contact with pore waters rich in sulfur tetroxide (SO4), calcium (Ca) and oxygen (O2) that were in direct contact with the ocean bottom water. One result of these microbe-mediated reactions was the formation of CH4-derived carbonates, which constituted one topic of the studies undertaken within NEW VENTS. The strong methane enrichment of the sediment could also cause the formation of gas hydrates. Gas hydrate, an ice-like substance capturing gas, mainly CH4, in water cages in its lattice could be a potential future energy resource. Gas hydrates were identified at the Hikurangi Margin, i.e. the offshore working area at the east coast of New Zealand's north island, by using seismic methods which revealed a widespread Bottom-simulating reflector (BSR) in the seismic sections. Together with bathymetric mapping and hydroacoustic surveys of bubble-releasing seeps, representing free CH4 gas, accurate positioning of active seep sites and their link to fluid pathways in the seabed could be achieved. The necessary data were acquired during three cruises in 2006 and 2007 with research vessels 'RV Tangaroa' and 'RV Sonne' during 16 weeks of work at sea. The cruises were TAN0607, TAN0616 and SO191. The main project objectives were: 1. to find active seep sites, map their spatial distribution and study their bubble release activity by visual and hydroacoustic methods; 2. to conduct geochemical analyses of pore waters and the water column so as to define the major geochemical reactions driving the seep habitat and determine the flux intensity; 3. to sample carbonates, which were the archives of past seep activity, and study their formation mechanism; 4. to integrate these data into a database and present and publish the scientific results during conferences or talks as well as in scientific journals. The specific goals that were achieved by the fellow during the action were: 1. the participation in three cruises, one as the co-chief scientist; 2. the collection and scientific interpretation of bathymetric and geochemical data from several seep sites offshore New Zealand and onshore fossil sites; 3. the organisation of a special session at the European Geosciences Union (EGU) 2008 regarding the joint research carried out, along with the initiation and managing of a special issue of Marine Geology, including 23 papers in total, on CH4 seep-relevant studies along the Hikurangi Margin since 2004.

Data: CORDIS, © European Union