By: magic-gigapans
Image: Callan Bentley, Mid-Atlantic Geo-Image Collection
License: Creative Commons Non Commercial ⧉

Uploaded: 10 Apr 2020
Last Updated: 29 May 2020

916 megapixels
33,040 x 27,736 pixels
110.1 in X 92.5 in at 300dpi

Sample from the site of the original Ramsay and Graham shear zones on the Isle of Lewis, Outer Hebrides, Scotland. The sample is interesting because of the mineral’s strain response. In granites, it is common for shear zones to involve crystal plastic deformation of quartz and mica surrounding brittle ferromags and feldspars (±dynamically recrystallized sigma/delta tails). Here, the rock is gabbro and the feldspars are plastically deformed. Not as stringy as quartz because they don’t have the basal slip mechanism. The dark minerals are mainly amphibole but that is retrograded from pyroxene.