Calc silicate skarn
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Fact sheet
Description: 

The intrusion of the main Central complex on Rum caused heating and alteration of the surrounding Precambrian and Cretaceous sediments. Contact metamorphism (probably over 600 °C) and hot fluids created most of the textures in this rock, which has been completely recrystallised. The rock probably originated as a Cretaceous limestone, and the metasomatism transformed it into a calc silicate skarn rock. Skarn is a term applied to rocks that have been transformed by the intrusion of an igneous rock, introducing both heat and fluids and sometime causing mineralisation, which is why skarns are often the sites of ancient mining activity. This sample came from Allt nam Ba on the Isle of Rum.

In thin section most of the rock is composed of metamorphic calcite, although it is rich in impurities. The rock also contains several unusual metamorphic minerals that are difficult to identify. One such mineral is tilleyite, a calcium silicate mineral named after the famous Cambridge academic Cecil Edgar Tilley (1894—1973). Rotation 1 shows lamellar twinned tilleyite.

In Place
In Time
infoImage: 
Location description: 
Isle of Rum, Scotland
Accuracy:
Location precision: 
Good
Timescale:
Timescale: 
Paleogene
Ma = Millions of years ago
In Focus
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Type:
Type: 
metamorphic
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