HR: 08:15h
AN: V31F-02    [Abstracts]
TI: Icelandic Rift Relocations: Melting Models and Geochemical Observations
AU: * Walters, R L
EM: waltersr@tcd.ie
AF: Department of Geology, Trinity College Dublin, Dublin, 2, Ireland
AU: Jones, S M
AF: Department of Geology, Trinity College Dublin, Dublin, 2, Ireland
AU: Maclennan, J
AF: Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, United Kingdom
AU: Park, S
AF: Korea Polar Research Institute, KOPRI, Incheon, 406-840, Korea, Republic of
AB: Rift relocations are distinctive features associated with plume-ridge interaction. The underlying processes controlling these relocations are not well understood. Observations of crustal thickness and basalt composition have been commonly used to investigate plume-ridge interaction, but both of these observations are affected by the rift relocation cycle. We therefore need to understand the rift relocation process better in order to isolate its effects from those caused by other processes, such as variations in plume flux, temperature or distance from the ridge. We present the first quantitative model of variations in melt production rates and composition during a rift relocation cycle including the growth and death of spreading centres. The two dimensional time-dependent model of passive upwelling beneath a spreading ridge is based on simple corner flow. The thermal structure is calculated using a control volume approach. The resulting melting structure is then calculated and used to predict the variation in crustal thickness and composition through time. The model shows an initial phase of small melt fractions as the ridge grows, moving into the steady-state phase showing much larger melt fractions and thicker crust. Finally, as the ridge dies and spreading rate decreases, conductive cooling results in a reduction in the melt fraction. The results of the model are compared to geochemical and geophysical observations of the current rift relocation in southern Iceland and a palaeo-rift relocation in northern Iceland. A comparison is also made with the abandoned Phoenix Ridge, Drake Passage, Antartica. The geochemical observations are consistent with smaller degrees of melting at both the birth and death of rift zones. Combination of these observations and the model results will be used to constrain the rate of transfer of spreading between rift zones.
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8137 Hotspots, large igneous provinces, and flood basalt volcanism
DE: 8178 Tectonics and magmatism
DE: 8410 Geochemical modeling (1009, 3610)
DE: 8416 Mid-oceanic ridge processes (1032, 3614)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting