Armitage, J.J., Henstock, T.J., Minshull, T.A. and Hopper, J.R.
Lithospheric controls on melt production during continental breakup at slow rates of extension: Application to the North Atlantic
Geochemistry, Geophysics, Geosystems, 10, . (doi:10.1029/2009GC002404).
Rifted margins form from extension and breakup of the continental
lithosphere. If this extension is coeval with a region of hotter lithosphere,
then it is generally assumed that a volcanic margin would follow. Here
we present the results of numerical simulations of rift margin evolution by
extending continental lithosphere above a thermal anomaly. We find that unless
the lithosphere is thinned prior to the arrival of the thermal anomaly
or half spreading rates are more than ? 50mmyr?1, the lithosphere acts
as a lid to the hot material. The thermal anomaly cools significantly by conduction
before having an effect on decompression melt production. If the lithosphere
is thinned by the formation of extensional basins then the thermal
anomaly advects into the thinned region and leads to enhanced decompression
melting. In the North Atlantic a series of extensional basins off the coast
of northwest Europe and Greenland provide the required thinning. This observation
suggests that volcanic margins that show slow rates of extension,
only occur where there is the combination of a thermal anomaly and previous
regional thinning of the lithosphere.
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