Olivine gabbro - Huntly
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Fact sheet
Description: 

This coarse-grained olivine gabbro sample comes from one of several large basic intrusions in NE Scotland that were intruded during the Grampian orogeny. The sample was collected from the Bin quarry, Huntly, Aberdeenshire, where the intrusion displays overturned cumulate layering with compositions varying from gabbro to troctolite. The variation in composition of the gabbro at this locality reflects processes such as fractional crystallisation and contamination by the surrounding Dalradian metasediments. The rock is a plagioclase-olivine-augite cumulate gabbro and this example is about 489 million years old.

In thin section the large olivine grains exhibit black alteration minerals, such as hematite, along internal cracks, and dominantly green-coloured chlorite alteration at the grain margins. The pyroxene is also cracked but exhibits well-defined cleavage with some grains showing two cleavages at the characteristic 90 degree separation. Plagioclase feldspar crystals have an aligned cumulate texture and exhibit strong lamellar twinning.

 

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Location description: 
Bin quarry, near Huntly, Scotland
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Location precision: 
Good
Timescale:
Timescale: 
Ordovician
Ma = Millions of years ago
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Type: 
igneous
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