Basaltic andesite with cordierite nodule
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Fact sheet
Description: 

This sample is a xenolith from the upper part of a sill sheet in the Loch Scridain Sill Complex on the Isle of Mull, Scotland. The Scridian Complex is intruded into Moine (Neoproterozoic) crystalline basement rocks beneath the Mull central volcano. It consists of a series of high-level, inclined, xenolithic sheets, ranging in composition from basalt, through andesite and dacite, to rhyolite. This sample is an unusual composition xenolith in a basaltic andesite sill.

In thin section the xenolith is dominated by large cordierite crystals that appear to have back reacted with the liquid magma. The cordierite is relatively inclusion-free although brown-stained adjacent to the liquid, and exhibits characteristic strong polysynthetic twinning. The basaltic andesite is fine-grained and appears to have invaded the xenolith while liquid. Away from the xenolith the plagioclase crystals are randomly oriented, but between the cordierites the crystallisation appears to vary, often forming radiating bundles.

In Place
In Time
infoImage: 
Location description: 
Loch Scridain, Isle of Mull, Scotland
Accuracy:
Location precision: 
Poor
Timescale:
Timescale: 
Paleogene
Ma = Millions of years ago
In Focus
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Type:
Type: 
metamorphic
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