(A brief introfuction to the Loch Borralan Carbonatite)
Between the NE shore of Loch Urigill and Loch Borralan lies Britain’s only carbonatite pluton. The presence of a carbonatite in the Assynt area was first reported to the geological community by Young, Parsons and Threadgould in 1994 . The pluton was actually discovered by an undergraduate from the University of Aberdeen in the late 1980s who was mapping in the area. He puzzled over the rocks and eventually was bold enough to confront his supervisors about it. Sure enough, his speculation was soon corroborated and a fuller investigation was launched.
So what is known about the carbonatite? Well there has been relatively little work conducted on it since it was reported in the Journal of the Geological Society of London in 1994. It was reported that there are 4 varieties that occur:
The latter of three of the four types above were only observed in situ after part of the pluton was excavated. Since then mineralogical and whole rock analyses were conducted on the four different lithologies. Those chemical analyses revealed that the Loch Borralan carbonatite is chemically and isotopically (carbon) distinct from the surrounding Durness Dolomites in which the pluton is enveloped.
There are many unanswered questions about the pluton. Amazingly, there has been little interest in the body since the mid 1990s. I visited the carbonatite earlier this summer, and collected a sample of the porphyritic sövite. A thin section of this has revealed some interesting minerals which I am in the process of having analysed. Hopefully a report into further findings in the mineralogy of the body will follow some time next year.