M15. Greenschist - Horn Head, Donegal
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Fact sheet
Description: 

Horn Head greenschist with blastomylonitic texture and chlorite porphyroblasts.

This greenschist-facies metabasite sample was collected from a narrow, attenuated layer of dark green rock within psammites on the cliff-top near Horn Head.  The rocks here are intensely sheared and associated with a major low-angle fault known as the Horn Head Slide.  The attenuated band of metabasite can be traced laterally into a much thicker basic intrusion in less-deformed psammites.  This intrusion is presumed to belong to the suite of dolerite and gabbro intrusions in the Dalradian Supergroup that were emplaced about 600 million years ago. In this rock chlorite porphyroblasts are fairly random in their orientation and overgrow a fine-scale compositional banding produced by intense shearing on the Horn Head Slide.

Neoproterozoic, Dalradian Supergroup  600 million years ago.

Rotation 1 - Straight extinction in biotite and chlorite

In Place
In Time
Location description: 
Horn Head, near Dunfanaghy, Co. Donegal, Ireland
Accuracy:
Timescale:
Timescale: 
Proterozoic
Ma = Millions of years ago
In Focus
Type:
Type: 
metamorphic
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