Basalt with spinel lherzolite xenolith
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Fact sheet
Description: 

This sample is a xenolith from within a basalt lava flow, brought up from between 30 and 90 km beneath the Earth's surface from deep within the upper part of the Earth's mantle. The lava was erupted during the Carboniferous period, in an area of the Midland valley that was often beneath sea level and saw limestone deposition. The rock comes from Hillhead Quarry, Dundonald, Ayrshire, Scotland, which was created to produce aggregate for roads. The quarry is also known for the prominent columnar jointing in a thick basalt flow.

The thin section exhibits both the xenolith and encompassing basalt. The basalt contains a randomly oriented network of plagioclase grains with pyroxene and relatively unaltered olivine crystals. However some of the olivine grains may actually be fragments of the xenolith. On the left of the thin section plagioclase is absent and the lithology is dominated by coarse-grained olivine and spinel. Much of the olivine is fractured but not strongly altered, and fracturing is more pronounced towards the edge of the xenolith.

In Place
In Time
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Location description: 
Hillhead quarry, Ayrshire, Scotland
Accuracy:
Location precision: 
Moderate
Timescale:
Timescale: 
Carboniferous
Ma = Millions of years ago
In Focus
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Type:
Type: 
igneous
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