In Scottish Highlands the presence of garnets is diagnostic of a particular depth of burial and metamorphism in the roots of the Caledonian mountain chain. In NW of Loch Lomond national park Ben Oss is speckled with garnet but Ben Lui alongside has none at all.
As you may know it was the Scottish sequence of metamorphic grades (with garnet indicating one of them) that was defined by George Barrow. I learned it as the Barrovian Sequence, and it is applied world-wide in regional (burial) metamorphism. These rocks here were metamorphosed locally, by contact with the hot magma, but even in contact metamorphism the sequence based on distance from heat can be observed in places.
In Scottish Highlands the presence of garnets is diagnostic of a particular depth of burial and metamorphism in the roots of the Caledonian mountain chain. In NW of Loch Lomond national park Ben Oss is speckled with garnet but Ben Lui alongside has none at all.
As you may know it was the Scottish sequence of metamorphic grades (with garnet indicating one of them) that was defined by George Barrow. I learned it as the Barrovian Sequence, and it is applied world-wide in regional (burial) metamorphism. These rocks here were metamorphosed locally, by contact with the hot magma, but even in contact metamorphism the sequence based on distance from heat can be observed in places.