IODP Expedition 336: initiation of long-term coupled microbiological, geochemical, and hydrological experimentation within the seafloor at North Pond, western flank of the Mid-Atlantic Ridge

摘要

Integrated Ocean Drilling Program (IODP) Expedition 336 addressed questions concerningsubseafloor microbial life and its relation to seawater circulation and basalt–seawaterreactions in the basaltic ocean crust. Sediment and basement samples were recovered atthree drill sites located in the North Pond area, an 8 × 15 km large sedimentpond on the 8 Ma western flank of the Mid-Atlantic Ridge around 22°45' N and46°05' W in roughly 4450 m water depth. The average core recovery ratein basement was approx. 31%. The subseafloor depth of the basement holes ranges from90 to 332 m; sediment thickness is between 36 and 90 m. Two of the holes (U1382A, and U1383C)were equipped with advanced Circulation Obviation Retrofit Kit (CORK) observatories,employing – for the first time – fiberglass casing. Another CORK string was deployedin Deep Sea Drilling Project (DSDP) Hole 395A, but the wellhead broke off upon final installment.Nonetheless, the North Pond observatory is fully operational and post-cruise observatoryresearch is already underway. Combined geochemical and microbiological studies ofthe drill core samples and experimental CORK materials will help understand(1) the extent and activity of microbial life in basalt and its relation to basaltalteration by circulating seawater, and (2) the mechanism of microbial inoculationof an isolated sediment pond.