Details of Award
NERC Reference : NE/H011986/1
Measuring the pulse of the Iceland plume
Grant Award
- Principal Investigator:
- Professor G Fitton, University of Edinburgh, Sch of Geosciences
- Grant held at:
- University of Edinburgh, Sch of Geosciences
- Science Area:
- Terrestrial
- Marine
- Freshwater
- Earth
- Atmospheric
- Overall Classification:
- Earth
- ENRIs:
- Natural Resource Management
- Global Change
- Science Topics:
- Ocean Circulation
- Tectonic Processes
- Mantle & Core Processes
- Climate & Climate Change
- Abstract:
- Mantle plumes are solid-state convective mantle upwellings that provide the principal means by which heat and material are transferred from the deep Earth to the surface. They are responsible for much of the world's intraplate volcanism (e.g. Hawaii) and their initiation is accompanied by massive outpourings of magma on a scale not seen today. These massive volcanic episodes produce large igneous provinces, two of the largest of which coincided with global mass-extinction events at the Permian-Triassic (Siberia) and Cretaceous-Palaeocene (Deccan) boundaries. Understanding the nature and origin of mantle plumes is a first-order goal of the Earth Sciences. Iceland is arguably the best place on Earth to investigate the nature of mantle plumes because the juxtaposition of a large mantle-melting anomaly on an oceanic spreading centre allows the anomalous mantle to decompress to shallow levels and therefore melt to the maximum possible extent. Large melt fractions allow much less ambiguous estimates of mantle composition and temperature than do smaller melt fractions. The mantle beneath Iceland appears to be hotter than the ambient North Atlantic upper mantle and is also compositionally different, but the relative importance of temperature and composition in generating the melting anomaly is unclear. It has even been argued that the Iceland melting anomaly is entirely due to extra fertility in the mantle source and therefore doesn't require a mantle plume at all. Whatever the source of the melting anomaly, its effects appear to be pulsing. Diachronous V-shaped ridges (VSRs) in basement topography straddling the Reykjanes Ridge (RR) south of Iceland, expressed most clearly in the gravity field, represent variations in crustal thickness produced on a time scale of ~5 million years. The principal questions posed here are: (1) whether this variation in crustal thickness is caused by variations in temperature, mantle fertility, or both; and (2) whether plume outflow is radial or channelled down the RR. An application for ship time on the RV Celtic Explorer to dredge samples from the VSRs in order to address these questions was submitted to the Irish Marine Institute by Dr Steve Jones (Trinity College, Dublin) in August 2007 and was funded and scheduled extremely quickly. The dredging cruise (CE0806) took place in April and May of that year and we now have a suite of basalt samples from two of the VSRs. We propose to analyse these samples and compare their chemical and isotopic composition with that of basalt from the adjacent axial zone, thus allowing us to say whether the mantle beneath the ridge axis at the time of VSR formation was hotter and/or more fertile than it is at present. The adjacent ridge axis was dredged some time ago and data from these samples is available in the published literature. We also recovered samples from a long and previously unsampled section of the southern RR where it is likely to intersect the projection of the second prominent VSR. If the point of intersection can be clearly identified then it will be possible to determine whether the VSRs are slightly curved (as predicted by radial flow) or straight (channelled flow). Beside its importance to our understanding of deep-Earth processes, the work proposed here will also have implications for palaeoceanography and hydrocarbon exploration. Fluctuation in mantle temperature should cause correlated fluctuation in water depth along the Greenland-Iceland-Faroes ridge, and this will affect the flow of northern component water southwards from the North Atlantic. The work proposed here should advance our understanding of the link between mantle and surface processes. Transient thermally induced uplift-subsidence events also affect passive continental margins, and there is evidence that such oscillations have influenced the sedimentary record in the North Sea. Understanding these oscillations will clearly be of interest to the oil industry.
- NERC Reference:
- NE/H011986/1
- Grant Stage:
- Completed
- Scheme:
- Small Grants (FEC)
- Grant Status:
- Closed
- Programme:
- Small Grants
This grant award has a total value of £33,784
FDAB - Financial Details (Award breakdown by headings)
| DI - Other Costs | Indirect - Indirect Costs | DA - Investigators | DA - Estate Costs | DA - Other Directly Allocated | DI - T&S |
|---|---|---|---|---|---|
| £18,745 | £3,988 | £7,271 | £1,259 | £1,048 | £1,472 |
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