An area of Lewisian Gneiss some 150 sq km in extent is described, Coll in some detail, Tiree only partially. A history of deformation of at least seven phases is envisaged for the complex, although other indistinguishable phases occurred at an earlier stage in the history of the complex. Quartzo-felspathic gneisses, metasediments, basic, intermediate and ultramafic rocks, and early concordant Granites show the varying effects of three metamorphic episodes. The earliest was at granulite facies and succeeded by amphibolite facies and greenschist facies metamorphism. Some tectonic phases may be correlated with metamorphic events. Certain Geochemical evidence points to a pre-granulite facies lower grade metamorphism. Many of the macroscopic features of the complex have been caused primarily by deformation. The types of structure in each phase were probably controlled by prevailing conditions, especially the presence or absence of hydrous fluids. Much evidence points to a chemical evolution of the complex perhaps analogous to a crustal layering of the metamorphic facies in basement rocks, and having a bearing on the processes active early in the history of this portion of the continental crust.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:727125 |
| Date | January 1970 |
| Creators | Drury, Stephen A. |
| Publisher | University of Birmingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://etheses.bham.ac.uk//id/eprint/8023/ |
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