Roineabhal
Geological Conservation Review site | GCR #2442 | Structural and Metamorphic Geology | Lewisian
Scotland's geosites are chosen because of their local, national or international importance. Take only photos, leave only footprints: avoid causing any damage to this site. You can walk almost anywhere in Scotland without the need to ask permission or keep to paths, but you have a responsibility to care for your own safety, to respect people's privacy and peace of mind and to cause no damage.
The right of access does not extend to quarries, building sites or any land where public access is prohibited, or to the collection of geological samples.
Summary
Anorthosites - the largest occurrence in the UK - part of the South Harris Igneous Complex.
The anorthosite body of Roneval is unique in Britain. Central parts of the anorthosite mass preserve a granulite-facies assemblage, and show evidence of a complex magmatic history with late magmatic phases disrupting foliated earlier ones. Gabbro-anorthositic banding in the central part of the area is disrupted and irregular. The margins of the anorthosite are mylonitic shear zones; good exposures occur in the Ligarabay quarry and north-west of Loch na Clachaidh. Above Loch na Clachaidh there are fine exposures of ultrabasic net veining of anorthosite by ultramafic material. The veining clearly pre-dates the granulite facies metamorphism. Late pseudotachylyte veining follows the early net vein structures. The slopes east of Leverburgh have good exposures which show shear zones in anorthosite, and also demonstrate the complex early history of the anorthosite. This site is of critical importance in containing the best exposure of Lewisian anorthosite. This is the only large body of anorthosite in the UK, and here it is possible to demonstrate evidence bearing on its place in the structural and magmatic history of the Lewisian complex.
