Some Illustrations of Igneous Layering
The following sixteen pages contain a selection of photographs, supplied by workshop members, showing striking or thought-provoking layering not otherwise discussed in the text, or representing rock-types not otherwise treated. References are given below, wherever possible, to full published descriptions, and as in the main text the examples are arranged in order from the most evolved to the most basic intrusions. Captions were supplied by the authors given, with sane editorial modifications and amplifications for consistency. As elsewhere in this book, descriptive terminology borrowed from sedimentary rocks need not necessarily imply a ‘sedimentary’ origin for the igneous textures. It should be noted that the rather large number of illustrations of structures in granites and syenites does not give a balanced impression of the frequency with which similar structures are encountered: layering is almost ubiquitous in large basic intrusions, but a rarity in evolved rocks. When it does occur it is usually of limited lateral or vertical extent. The similarity between the latter structures and those in more basic rocks is in other ways striking, however.
KeywordsModal Layering Nepheline Syenite Slump Structure Basic Intrusion Igneous Texture
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