Dhoon Granodiorite Intrusion

A major igneous intrusion on the NE coast, exposed in the beautiful Dhoon Glen and along sea cliffs. The Dhoon intrusion is a granodiorite (coarser than granite, with more plagioclase) that was emplaced into the Manx Group sediments. Where igneous rock meets sedimentary rock (the 'contact zone'), mineralisation is most intense — this is where hot fluids from the magma deposited metals in fractures. WHY COLLECT HERE: Dhoon Glen is one of IoM's most spectacular glens — a deep wooded ravine with waterfalls. The glen exposes the granodiorite beautifully, and stream boulders contain quartz veins with pyrite and occasionally chalcopyrite. The coastal cliffs show the intrusion in cross-section. Best specimens are in stream-washed boulders where weathering has exposed the mineral veins. This is also a great site for understanding IoM geology — the contact between sedimentary and igneous rocks is clearly visible.