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Three‐dimensional finite strain analysis in the high‐grade part of the Sanbagawa Belt using deformed meta‐conglomerate
Author(s) -
Moriyama Yoshinori,
Wallis Simon
Publication year - 2002
Publication title -
island arc
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.554
H-Index - 58
eISSN - 1440-1738
pISSN - 1038-4871
DOI - 10.1046/j.1440-1738.2002.00360.x
Subject(s) - overprinting , flattening , conglomerate , geology , ellipse , strain (injury) , finite strain theory , deformation (meteorology) , strain rate , mineralogy , geometry , seismology , geochemistry , composite material , materials science , finite element method , tectonics , structural engineering , mathematics , anatomy , medicine , oceanography , engineering , sedimentary rock
Regional ductile deformation of the Sanbagawa belt is generally thought to be characterized by constrictional strain, based on strain analysis using deformed radiolarians in the low‐grade regions. Similar strain analysis could not be carried out in the medium‐ to high‐grade zones, because it is very difficult to identify individual radiolarians after strong recrystallization. However, discovery of the first known meta‐conglomerate in the high‐grade region of the Sanbagawa Belt allows quantitative 3‐D strain to be estimated in this region. Using a development of the Rf‐φ method, an evaluation of appropriate errors for this estimate can be determined. The principal strain ratios and estimated errors are X/Y = 5.4–6.6 and Y/Z = 3.8–3.9 implying deformation in the flattening field and refuting the idea of uniform constrictional strain. Semi‐quantitative markers of the shape of the strain ellipse throughout the high‐grade regions suggest that the deformation of the Sanbagawa Belt is dominantly in the flattening field. The difference with the earlier results may be due to late‐stage overprinting by upright folding of the main ductile fabric in the low‐grade region of western Shikoku.