Editing Cambir Dolerite - St. Kilda: an illustrated account of the geology

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== Chapter 4 Cambir Dolerite D ==
 
== Chapter 4 Cambir Dolerite D ==
  
'''Keywords: mineral analyses, annealed textures, cooling history'''
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Keywords: mineral analyses, annealed textures, cooling history
  
 
At the north west end of the Cambir the Western Gabbro is intruded by sheets and veins of the fine-grained Cambir Dolerite. It is exposed on the Cambir cliffs facing the island of Soay, and also near sea level below Mullach Bi where south-westerly-dipping sheets of similar rock cut the Western Gabbro. On weathered surfaces small variations in grain size give the Dolerite a streaky appearance and altered poikilitic olivine crystals form vague bands of elongate black blotches. Contacts with the Western Gabbro are sharp and transgressive to the banding and lamination but variable in attitude and orientation; overall the Dolerite probably dips steeply south-east. Outcrops of Dolerite near the grass-mantled gully below and west of the Cambir summit are variable in grain size and in places distinction from the Western Gabbro is difficult. Near the top of the gully at about 500 ft (160 m) there is an isolated intrusion of medium-grained gabbro similar to some on Soay. Like the Western Gabbro, the Cambir Dolerite is intruded by coarse gabbroic and pegmatitic veins and affected by the same kinds of faulting and shearing which gave rise to the network of veins.
 
At the north west end of the Cambir the Western Gabbro is intruded by sheets and veins of the fine-grained Cambir Dolerite. It is exposed on the Cambir cliffs facing the island of Soay, and also near sea level below Mullach Bi where south-westerly-dipping sheets of similar rock cut the Western Gabbro. On weathered surfaces small variations in grain size give the Dolerite a streaky appearance and altered poikilitic olivine crystals form vague bands of elongate black blotches. Contacts with the Western Gabbro are sharp and transgressive to the banding and lamination but variable in attitude and orientation; overall the Dolerite probably dips steeply south-east. Outcrops of Dolerite near the grass-mantled gully below and west of the Cambir summit are variable in grain size and in places distinction from the Western Gabbro is difficult. Near the top of the gully at about 500 ft (160 m) there is an isolated intrusion of medium-grained gabbro similar to some on Soay. Like the Western Gabbro, the Cambir Dolerite is intruded by coarse gabbroic and pegmatitic veins and affected by the same kinds of faulting and shearing which gave rise to the network of veins.

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