Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/162697
Title: High-strain deformation of conglomerates: Numerical modelling, strain analysis, and an example from the Wutai Mountains, North China Craton
Author: Ran, H.
Bons, P.D.
Wang, G.
Steinbach, F.
Finch, M.
Griera, A.
Gómez Rivas, Enrique
Llorens, M.
Ran, S.
Liang, X.
Zhou, J.
Keywords: Geologia estructural
Roques sedimentàries
Xina
Structural geology
Sedimentary rocks
China
Issue Date: 30-Jun-2018
Publisher: Elsevier Ltd
Abstract: Conglomerates have been widely used to investigate deformation history and rheology, strain, vorticity and viscosity. Previous studies reveal that several factors, such as pebble shapes and concentrations, as well as material properties, affect conglomerate deformation. However, how pebble concentration and interaction between pebbles affect deformation is not understood very well. We use the 2D numerical modelling platform ELLE coupled to the full field crystal visco-plasticity code (VPFFT) to simulate the deformation of conglomerates with various viscosity contrasts between pebbles and matrix and different pebble concentrations, with both linear (stress exponent n = 1) and power-law (n = 3) viscous rheologies, under simple shear conditions up to a shear strain of ten. Pebbles can behave as effectively passive, deformable or effectively rigid. An increase in pebble concentrations/viscosity contrasts enhances pebble deformation, but reduces their rotation. A mean aspect ratio (Rf) - orientation (ϕ) plot is proposed to gain an estimate of pebble deformation behaviour and the amount of bulk strain. Closely spaced rigid or deformable pebbles can form clusters that mechanically act as single inclusions. Rigid clusters rotate and survive for only short strain increments, whereas the more stable deformable ones keep on elongating with minor rotation. We provide a natural example of deformed conglomerates from the Wutai Mountains, North China Craton. These consist of banded-iron-formation (BIF) pebbles embedded in a schistose matrix. Using the mean Rf-ϕ plot, a finite strain of ∼6 under simple shear could be determined. The viscosity of the pebbles is estimated at about 5-8 times that of the matrix for a linear rheology (n = 1), or 2 to 5 times if a power-law rheology with n = 3 is assumed.
Note: Versió postprint del document publicat a: https://doi.org/10.1016/j.jsg.2018.06.018
It is part of: Journal of Structural Geology, 2018, vol. 114, p. 222-234
URI: http://hdl.handle.net/2445/162697
Related resource: https://doi.org/10.1016/j.jsg.2018.06.018
ISSN: 0191-8141
Appears in Collections:Articles publicats en revistes (Mineralogia, Petrologia i Geologia Aplicada)

Files in This Item:
File Description SizeFormat 
687146.pdf893.37 kBAdobe PDFView/Open


This item is licensed under a Creative Commons License Creative Commons