#ThinSectionThursday I've been thinking about lovely Lewisian rocks from the island of Iona today.
So here's a very weird Iona rock I collected a few years ago: marble with a large diopside crystal, showing intense stripy strain/shock lamellae in crossed polar light. something dramatic has happened to this rock (and to others nearby), but we don't know what, or when. So many mysteries....
Field of view 2mm wide. More info in Alt txt.
Today I was given this fabulous rock specimen from the Lewisian Complex in Iona.
We have a grey banded garnet-gneiss on the left side of the image. This banding is truncated by the dark rock on the right, indicating that the dark rock must have been intruded after the banding had formed.
Then both rocks have been heated, and the grey banded rock has partially melted, forming a granitic melt which has then intruded into the dark rock.
More in Alt txt.
A #FridayFold from the west coast of the #IsleofLewis.
The dark mafic #OuterHebrides dykes were intruded into the #Lewisian gneiss. The original cross cutting relationship has been brought into near concordance during subsequent #Laxfordian deformation which also generated these folds.
Attenuation of the limbs in these folds has left some of the fold hinges essentially floating.
#Laxfordian folding on the north west coast of the #IsleofLewis
John Faithfull ππͺπΊπ΄σ §σ ’σ ³σ £σ ΄σ Ώπ§‘βπ»βπΏ
Peter L Bowden