Syenite – Borralan
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Fact sheet
Description: 

This syenite is known locally as Borralanite and comes from the vicinity of Loch Borralan, Assynt District, Scotland. This rock type forms the main mass of the Borralan intrusion which lies in the SW corner of the Assynt region bordered by the Moine Thrust zone. This intrusive complex is the only plutonic complex composed largely of silica-undersaturated (i.e. feldspathoid-bearing) igneous rocks in the British Isles. Several members of the Borralan suite of intrusion are exceptionally alkaline. It provides Britain's only example of truly ultra-potassic magmatism.

The thin section exhibits large plates of orthoclase feldspar, nepheline with low birefringence colours, large brown euhedral garnets, and small equant grains of phlogopite mica.

In Place
In Time
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Location description: 
Borralan complex, Assynt District, Sutherland, Scotland
Accuracy:
Location precision: 
Good
Timescale:
Timescale: 
Silurian
Ma = Millions of years ago
In Focus
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Type:
Type: 
igneous
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