Details of Award
NERC Reference : NE/K007386/1
IODP A 4.5 million year record of arc volcanism in the Lesser Antilles
Training Grant Award
- Lead Supervisor:
- Professor MR Palmer, University of Southampton, Sch of Ocean and Earth Science
- Grant held at:
- University of Southampton, Sch of Ocean and Earth Science
- Science Area:
- Earth
- Marine
- Terrestrial
- Overall Classification:
- Earth
- ENRIs:
- Environmental Risks and Hazards
- Global Change
- Science Topics:
- None
- Abstract:
- Subduction zones are a key feature of Phanerozoic plate tectonics and represent the site where oceanic crust is recycled into the mantle. The release of volatiles from the subducting plate is generally thought to initiate melting in the overlying mantle wedge, which then leads to volcanism on the overlying crust. The composition of volcanic rocks in this setting is a mixture of material derived from the mantle wedge and overlying crust (which may or may not have formed in the subduction zone), as well as material released from the subducted plate - i.e. sediments and altered oceanic crust. These sources of material result in rocks that vary from basaltic to andesitic in character, although it is noteworthy that most of the volcanic rocks have compositions that are from one end of this spectrum or the other, with relatively few rocks of intermediate composition. In addition to representing a site of recycling of material between the crust and the mantle, subduction zone volcanism is also an important mechanism for growth of continental crust. Hence, developing an understanding of the types of volcanic rocks that are formed in this setting is important both for quantifying rates of recycling between two of the Earth's most important reservoirs and for discerning the nature of continental crust and how it has evolved through time. Much information has been gained from examining the composition of subduction zone volcanic rocks exposed on land, but it is difficult to gain a complete picture of the evolution of an individual volcanic centre through time. This because older rocks are covered by younger rocks, steep-sided andesitic volcanic edifices are particular prone to collapse, and erosion and soil development removes and obscures volcanic outcrops. In the case of island arc volcanism, much of the products of the volcanic activity are rapidly transported to the adjacent oceans. For example, it is estimated that ~75% of the material erupted from the Soufriere Hills volcano on Montserrat, Lesser Antilles, since 1995 is now in the Caribbean Sea. By comparison with volcanic islands, the deep sea is a relatively stable environment. Hence, deep sea sediment cores taken nearby to volcanoes can preserve a record of the products of successive eruptions laid down over the lifetime of an individual island arc volcanic centre that is not preserved on the island itself. During IODP Expedition 340 to the Lesser Antilles (March-April 2012) we obtained 100% recovery of sediments from site U1396, lying approximately 30 km southwest of the island of Montserrat. These sediments largely comprise hemipelagic carbonate with at least 150 visible tephra layers extending back over 4 million years. The site is located on a basement high and sedimentary logging on board indicates that the tephra layers are all air fall deposits, with no lateral deposition from debris flows. The location of the site makes it likely that the majority of the tephra layers are derived from Montserrat. Although some tephra is also likely derived from Guadeloupe, these can be distinguished on the basis of their lead isotope compositions, and no layers thicker than 0.5 cm are expected from any other island. The aims of this studentship are therefore: 1) to derive a record of the geochemical and petrological evolution of volcanism on Montserrat since its formation and thus provide deeper insights into the processes outlined above 2) to compare the record of volcanism from the IODP site with that preserved on land to examine the extent to which the two records differ and thus aid in assessing how representative on-land records from other island arc centres are of their volcanic history These objectives will be met by detailed geochemical analyses of ~50 tephra layers already sampled from U1396 by the PI and additional samples collected from Montserrat. The latter activity will be conducted in association with the project partner - the Montserrat Volcano Observatory.
- NERC Reference:
- NE/K007386/1
- Grant Stage:
- Completed
- Scheme:
- DTG - directed
- Grant Status:
- Closed
- Programme:
- Open CASE
This training grant award has a total value of £75,446
FDAB - Financial Details (Award breakdown by headings)
| Total - Fees | Total - RTSG | Total - Student Stipend |
|---|---|---|
| £13,978 | £12,275 | £49,194 |
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