Details of Award
NERC Reference : NE/D001277/1
Contingency funds for the rental of the DMT 360 degree Core Scanner for IODP Expeditions 309 and 313.
Grant Award
- Principal Investigator:
- Professor DAH Teagle, University of Southampton, Sch of Ocean and Earth Science
- Co-Investigator:
- Dr T Brewer, University of Leicester, Geology
- Grant held at:
- University of Southampton, Sch of Ocean and Earth Science
- Science Area:
- Marine
- Earth
- Overall Classification:
- Marine
- ENRIs:
- Natural Resource Management
- Science Topics:
- Biogeochemical Cycles
- Earth Resources
- Volcanic Processes
- Tectonic Processes
- Abstract:
- The mid-ocean ridges form a chain of mountains in the oceans that circuit the Earth like the seams of a baseball. These ridges are constructive plate boundaries where new ocean crust is formed by plate tectonic spreading and the eruption of magma from the mantle. This is the major process by which the Earth releases its internal heat, and through ocean spreading and subduction at arcs ~60% of the Earth's surface has been rejuvenated in the past 180 million years. Because magma from the mantle is erupted onto and intruded into the ocean crust at ~1200 deg C, the overlying seawater is vigorous heated and submarine geothermal systems can be established, commonly resulting in high temperature submarine geysers that disgorge sulfide-rich fluids known as black smokers. Clearly there is a very close relationship between magmatic activity and seawater, but many of the processes resulting from seawater interactions with the ocean crust remain very poorly understood. Although the ocean ridges are relative high points in the oceans, they are mostly beneath >2000 m of water and are difficult to observe and sample. Scientists using manned submersibles or remotely operated vehicles can only observe the most recently erupted lavas, except at rare faulted exposures. Geophysicists can also make measurements of the ocean basement through determinations of the magnetic field and crustal seismic velocity, but these regional techniques need to be calibrated against actual rocks for the geology to be understood. Sample the sub-surfacing of the ocean crust requires drilling and the recovery of basement rock cores has been a primary goal of international science collaborations such as the Deep Sea Drilling Project and the new Integrated Ocean Drilling Program. From observations of ancient oceanic rocks now preserved on land known as ophiolites, and from submarine tectonic windows, the ocean crust appears to be made of three basic layers: erupted lavas, commonly with pillowed shapes, that overly parallel-sided vertical intrusions known as sheeted dikes, which in turn overly, coarse-grained gabbroic rocks that are the frozen magma chambers. Despite more than 30 years of drilling, only one hole penetrates the erupted lavas into the dikes and no hole has sampled the sheeted dike-gabbro boundary. That boundary zone being perhaps the most critical in terms of heat exchange between magma and seawater. In mid to late 2005 IODP Expeditions 309-313 will return to Hole 1256D, a deep drillhole in the Pacific, to drill down to the frozen magma chambers. This is the first basement borehole that has been designed for deep drilling and is sited in a region where gabbros are predicted to be at the shallowest depths. This grant asks for funds to rent a special core scanner that takes 360-deg digital photographs of the outside surface of the recovered cores. Unfortunately this imager is not a standard piece of IODP equipment and must be rented when required. These core scans can only be made aboard the ship before the core is split allowing internal structures to be described and geochemical and physical properties studies undertaken. The core scans can then be compared with continuous, depth-calibrated images of the borehole walls measured using geophysical tools lowered down the borehole. Pieces of core from known depths can then be used to calibrate the continuous wireline logs to establish the architecture of the ocean crust at this site. By matching structures such as faults, magmatic fabrics or mineral veins in images of the core with the borehole walls, cores can be re-orientated about their vertical axis back to their true geographic bearing. This will allow scientists to determine the true geometry of the structural features as well as calculate the orientation of the paleomagnetic field preserved in the rocks when they cooled. Core-log integration and core re-orientation are essential to achieve the objectives on these drilling expeditions.
- NERC Reference:
- NE/D001277/1
- Grant Stage:
- Completed
- Scheme:
- Directed Pre FEC
- Grant Status:
- Closed
- Programme:
- IODP
This grant award has a total value of £10,000
FDAB - Financial Details (Award breakdown by headings)
| Total - Other Costs |
|---|
| £10,000 |
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