The role of Palaeocene magmatism in the tectonic evolution of the Sea of the Hebrides Basin: implications for basin evolution on the NW Seaboard

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Abstract
Major, trace element and isotope geochemistry of the magmas of the British Tertiary Volcanic Province suggests they rose through the lithosphere in dykes and ponded as sills at the Moho and within the upper crust. In the Sea of the Hebrides basin a linked system of discrete dyke swarms, sills and normal faults record rapid NE-SW extension at the near surface. The presence of a similar system of dykes and sills within the upper crust and at the Moho could have influenced mechanisms of lithospheric extension by dissipating vertical variations in strain laterally, eliminating space problems associated with depth dependant stretching. The addition of large thicknesses of magma to basins along the NW seaboard would have resulted in local burial, but subsidence would be offset by uplift resulting from isostatic effects and thermal expansion of the lithosphere during melting. Heat loss from rising magma would have a negligible effect on the maturation history of the sediments.