Accretion of the lower oceanic crust at fast-spreading ridges: a rock drill and near-bottom seafloor survey in support of IODP drilling in Hess Deep.

Lead Research Organisation: Cardiff University
Department Name: School of Earth and Ocean Sciences


Generation of ocean lithosphere by seafloor spreading at mid-ocean ridges is one of the fundamental geological processes operating on Earth. One of the most important yet most intractable problems is to understand how the magma reservoir beneath ridges generates the lower crust, especially at fast spreading rates. Gabbroic rocks from fast-spread lower crust are normally inaccessible; only in the Hess Deep rift valley (E Pacific) is a substantial section known to be exposed. We propose to survey this unique section using a remotely-operated vehicle in order to satisfy site survey requirements for the highly-ranked IODP proposal #551. In addition we plan to conduct our own sampling programme using the British Geological Survey's 'BRIDGE' seabed rock drill to obtain large numbers of short (1 m) orientated cores in transects through the gabbro section. Constraining heat and mass flux from the Earth's mantle to crust and crust to ocean, and testing conflicting models for the functioning of mid-ocean ridge magma chambers, can only be tested by direct observation and sampling. Fully oriented cores are imperative to address many of the outstanding questions and these capabilities of the BRIDGE drill remain unique. This survey will not only augment the IODP proposal but will in its own right also answer many critical questions that IODP operations cannot tackle.


10 25 50
Description (1) Collected essential site survey data that allowed Integrated Ocean Drilling Program Proposal 551 to be scheduled for drilling and subsequently drilled on Expedition 345.
(2) At the same time, made the first sampling of an essentially complete section of in situ fast-spread lower ocean crust, and by so doing directly test conceptual models for mid-ocean ridge magma chamber processes.
Exploitation Route Our results are key for all IODP Expedition 345 participants. Our scientific models, when all are finally completed, will form the basis for a new paradigm for understanding mid-ocean ridge magma chamber processes.
Sectors Education,Environment,Culture, Heritage, Museums and Collections,Other

Description Integrated Ocean Drilling Program
Amount $17,000,000 (USD)
Funding ID IODP Expedition 345 
Organisation Integrated Ocean Drilling Program 
Sector Academic/University
Country Global
Start 12/2012 
End 02/2013
Description Extensive site survey data package submitted to Integrated Ocean Drilling Program Site Survey Data Bank in support of IODP Proposal 551. 
Type Of Material Database/Collection of data 
Year Produced 2010 
Provided To Others? Yes  
Impact As a direct result of the site survey data submission, Proposal 551 was scheduled as IODP Expedition 345 in December 2012.