| P number: | P521375 |
|---|---|
| Caption: | Rock specimen of gneiss. Near second cairn, Shalloch, 1 1/3 miles south-west of New Galloway, Kirkcudbrightshire, Scotland. |
| Description: | The sample is a mixed granitic gneiss, with a pale area composed essentially of granite and a darker area of mafic minerals, mainly mica. British Geological Survey Petrology Collection sample number EMC3797. This sort of mixed rock is very common in areas where gneisses are present. A gneiss is a metamorphic rock of relatively high grade where partial melting of the original rock results in separation into distinct compositional layers. Gneisses that are highly segregated are termed migmatites (meaning mixed rock) and have a pale granitic component (leucosome) and a darker mafic or micaceous component (melanosome). The intrusion of the granite pluton of Cairnsmore of Fleet has resulted in a surrounding metamorphic aureole where the adjacent rocks have been altered by the great amount of heat generated by the emplacement of the granite. Away from the intrusion the effect gradually declines. Highly metamorphosed sediments occur at Knocknairling Hill, argillaceous rocks pass into andalusite-mica-schists and gritty beds become quartz-mica-schists. The rock will be Silurian in age but altered by the later contact metamorphism. |
| Date taken: | 01/12/2002 |
| Photographer: | McTaggart, F.I. |
| Associate: | T.S. Bain |
| Copyright statement: | NERC |
| Additional information: | EMC3797 |
| Orientation: | Landscape |
| Size: | 284.64 KB; 1000 x 775 pixels; 85 x 66 mm (print at 300 DPI); 265 x 205 mm (screen at 96 DPI); |
| Average Rating: | Not yet rated |
| Categories: | Unsorted Images |
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