Proterozoic: Moine schists and the Ross of Mull Granite
With a less than desirable start to our field trip – horizontal rain which hurts the face (but hey! Its not a proper geo field trip without a bit of water) – we left our wonderful house at the bottom of Ben More and travelled to Ardalanish Bay.
Glenfinnan Group moine schists were exposed along the beach with plenty of isoclinal folding which had then undergone secondary folding but this time more open. The group comprised of politic shists with calc-silicate rich patches. These patches gave rise to massive garnets.
At a special SSSI we were able to see one of the few triple points in Britain of the metamorphic Alumo silicates. Kyanite porphyroblasts were overprinted by andalusite and we were assured that sillimanite could be found further along the coast.
After climbing around the coast we saw the contact of the Ross of Mull granite with the schist. The granite has injected itself slowly into the host rocks with veining and numerous xenoliths and rafts of country rock.
Without a doubt the a typical day in the field is spent wondering how long it is until you can eat your lunch after which it’s spent wondering when you can go home and eat tea. I justify all this food by telling myself I’m walking it off getting to the outcrops 😛