The end of April saw our group in the Caldew Valley and at the foot of Carrock Fell on a visit delayed from the previous autumn because of vegetation hindering access. The confluence of the River Caldew with Grainsgill Beck was our initial objective. Skiddaw granite was intruded as a steep sided dome into the surrounding Skiddaw Group mudstones in the early Devonian, c385Ma. The heat from the granite intrusion metamorphosed the folded Skiddaw Group country rock into a very hard, fine grained, granular rock called hornfels. The pluton is about 4.5km in diameter and is surrounded by a concentric thermal metamorphic aureole.
Up Grainsgill Beck we briefly visited the Carrock Fell and Brandy Gill mines. German miners were brought over in the time of Queen Elizabeth I to mine for copper and silver (for coins) but during WW1 tungsten was mined here. There have been over 160 different mineral species identified in the Caldbeck Fells area,
a lot of them considered rare. We then went on to look at the Gabbro at various sites on the East side of Carrock Fell, and ended the day looking at the fluvioglacial deposits in the esker known as Long Hill.
