Crenulation cleavage and secondary compositional layering in greenschist facies semipelitic rocks (Lower Palaeozoic) of Sunnhordland region, SW Norway
作者:
RoaldB. Færseth,
Subimal Sinha-Roy,
期刊:
Geologiska Föreningen i Stockholm Förhandlingar
(Taylor Available online 1982)
卷期:
Volume 103,
issue 3
页码: 305-316
ISSN:0016-786X
年代: 1982
DOI:10.1080/11035898209453701
出版商: Taylor & Francis Group
关键词: Lower Palaeozoic rocks;greenschist facies;crenulation cleavage;classification;secondary compositional layering;differentiated layering;folding;flattening;strain;microstructures;stylolite;pressure solution;mica orientation;cleavage septa;microlithon;nuclea
数据来源: Taylor
摘要:
Greenschist facies semipelitic metamorphic rocks of Lower Palaeozoic age in Sunnhordland region, SW Norway contain a well-developed crenulation cleavage of the second generation. In the generation of the crenulation cleavage from a pre-existing fabric, gradations exist between discrete crenulation cleavage to zonal crenulation cleavage. The orientation of phyllosilicates within the cleavage septa is controlled primarily by the relative dominance of solution transfer of materials in discrete cleavage and by microfolding mechanism in zonal cleavage. In the former, new phyllosilicates may lie sub-parallel to the cleavage, but in the latter, phyllosilicate orientation may be variable, usually bimodal. The sites of discrete (solution) planes in variably tight folds, and the degree of development of zonal cleavage are dependent on the flattening strain. The secondary dominal character of the rock is a feature related to compositional differentiation through microfolding and essentially, solution transfer.
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