Details of Award
NERC Reference : NE/J005401/1
IODP Expedition 330: assessing the mantle plume component in the Louisville Seamount Trail, SW Pacific Ocean
Grant Award
- Principal Investigator:
- Professor AD Saunders, University of Leicester, Geology
- Grant held at:
- University of Leicester, Geology
- Science Area:
- Atmospheric
- Earth
- Freshwater
- Marine
- Terrestrial
- Overall Classification:
- Earth
- ENRIs:
- Global Change
- Science Topics:
- Mantle & Core Processes
- Abstract:
- One of the main products from melting of the Earth's interior is basalt. Basalt underlies the ocean basins, forms the bulk of ocean islands, and is found throughout the continents. It is the closest we have to providing a window into the mantle, the vast volume of rock between the crust and core of the Earth. The Earth's mantle convects on a range of scales, and comprises several chemical reservoirs. Basalts formed by melting of these reservoirs provide information about the evolution of the Earth's interior. For example, mid-ocean ridge magmas tap the shallow, chemically-depleted upper mantle reservoir, whereas ocean island magmas tap mantle derived from deeper, more enriched reservoirs. This simple model has, however, been questioned. For example, some magmas erupted in Iceland, a classic hotspot/plume region, have been found to be chemically depleted. Similarly, some magmas erupted at the distal end of the Emperor Seamount Chain also are depleted, despite being associate with the long-lived Hawaiian hotspot and plume. Are these unusual compositions due to interaction between a deeply-sourced plume and the upper mantle, or is the depleted character inherent in the plume itself? Because of their different histories, we may expect these different depleted components (within plume mantle or upper mantle) to develop characteristic isotopic features, and indeed this has been argued on the basis of Hf isotopes. The Louisville Seamount Trial, recently drilled during IODP Expedition 330, provides an opportunity to test the idea that depleted components may be incorporated in plumes. Expedition 330 recovered >800 m of rock from 5 seamounts at the older end of the Trail, emplaced during the late Cretaceous. Importantly, the seamounts were emplaced through lithosphere of different ages and thicknesses. This is crucial, because the lithosphere controls the extent of melting in the ascending plume, which in turn controls the composition of the magmas. Plume mantle ascending beneath thin lithosphere melts more extensively; the melts sample the mantle more comprehensively, including more refractory, depleted components. Plume mantle ascending beneath thick lithosphere (e.g., present-day Hawaii) has a restricted melting regime and the melting samples the more fusible, enriched components. Results from Iceland and the older Emperor Seamounts concur with this; where the plume interacts with thin lithosphere, we see more of the 'depleted' mantle components in the erupted basalts. The Louisville Seamount Trail provides a similar opportunity. Why is this important? Knowledge of the composition and evolution of the deep mantle reservoirs is fundamental to understanding the source of heat energy within the planet, as well as its long-term evolution. If large volumes of the deep mantle are chemically depleted, this would imply that they also have lower-than-predicted contents of radioactive isotopes (U, Th, K) and heat-generating capacity. We propose to analyse a range of basaltic samples from the Louisville Seamount Trail, in order to assess the temporal and spatial variations in elemental and isotopic composition. We shall use the trace and major element data to determine the extent and depth of melting of the mantle source, and the isotope (especially Hf and Nd isotopes) and highly-incompatible trace element data to assess the relative contribution from enriched and depleted mantle sources.
- NERC Reference:
- NE/J005401/1
- Grant Stage:
- Completed
- Scheme:
- Small Grants (FEC)
- Grant Status:
- Closed
- Programme:
- Small Grants
This grant award has a total value of £15,570
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DI - Staff | DA - Estate Costs | DA - Other Directly Allocated |
|---|---|---|---|---|---|
| £480 | £6,010 | £379 | £6,092 | £2,177 | £432 |
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