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British Tertiary Igneous Province
Abundant igneous activity in NorthWest Britain due to the tension related to the opening
of the North Atlantic Ocean
Thing to be found
Igneous body Example
Flood Basalts Isle of Mull
Plutons (granite and gabbro) Isle of Skye
Dyke Swarms Isle of Arran
Sills Drumadoon Sill
Columnar jointing Giant's Causway
Flood basalts developed as partial melting in the mantle below
the continental crust resulting from tension and this resulted in; Columnar jointing
due to slow cooling of lava flows
Magmatic differentiation in magma chambers developed, leading to mafic and silicic
intrusions. E.G Skye has two magma chambers one mafic and one silicic. The Black
Cuillins are made of gabbro with many dolerite dykes and the Red Cuillins are made of
Volcanic activity was explosive and further tension led to extensive dyke swarms.
Important to remember that at the same time as the British tertiary igneous province,
the Alpine Orogeny was occurring too. Britain was on the `edge' of Destructive Plate
margin and we were on the outer fringes of collision between Africa and Europe
forming Alps. Structural evidence folding in southern England (Lulworth Crumple)
British Tertiary Igneous Province Tension
Alpine Orogeny Compression
Mantle plume develops beneath northwest UK and Greenland.
Rifting and development of spreading centre, opening of North Atlantic.
Large volume of (flood) basalt associated with mantle plumes.
Hot spot trail to Iceland. Mid ocean ridge still active.
Evidence of tension (dykes etc.)
Later granitic intrusions due to melting of continental crust.