Abstract
| Original language | English |
|---|---|
| Pages (from-to) | 222-234 |
| Number of pages | 13 |
| Journal | Journal of Structural Geology |
| Volume | 114 |
| Early online date | 30 Jun 2018 |
| DOIs | |
| Publication status | Published - Sep 2018 |
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Keywords
- Conglomerates
- Numerical modelling
- Strain analysis
- North China Craton
Cite this
High-strain deformation of conglomerates : Numerical modelling, strain analysis, and an example from the Wutai Mountains, North China Craton. / Ran, Hao; Bons, Paul D. (Corresponding Author); Wang, Genhou; Steinbach, Florian; Finch, Melanie A.; Griera, Albert; Gomez Rivas, Enrique; Llorens, Maria-Gema; Ran, Shuming; Liang, Xiao; Zhou, Jie.
In: Journal of Structural Geology, Vol. 114, 09.2018, p. 222-234.Research output: Contribution to journal › Article
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TY - JOUR
T1 - High-strain deformation of conglomerates
T2 - Numerical modelling, strain analysis, and an example from the Wutai Mountains, North China Craton
AU - Ran, Hao
AU - Bons, Paul D.
AU - Wang, Genhou
AU - Steinbach, Florian
AU - Finch, Melanie A.
AU - Griera, Albert
AU - Gomez Rivas, Enrique
AU - Llorens, Maria-Gema
AU - Ran, Shuming
AU - Liang, Xiao
AU - Zhou, Jie
N1 - Fieldwork in the Wutai Mountains area, China was supported by the China Geological Survey (grant No. 12120114076401). We appreciate the help for the fieldwork from Zhongbao Zhao, Changshun Wen, Chao Li and Gongyao Xu and the constructive suggestions from Guoli Yuan, Zhongbao Zhao and Changshun Wen. HR thanks the financially support by the China Scholarship Council (CSC; No. 201506400014). EGR acknowledges the support of the Beatriu de Pinós programme of the Government of Catalonia's Secretariat for Universities and Research of the Department of Economy and Knowledge (2016 BP 00208). We thank two anonymous reviewers for their constructive comments.
PY - 2018/9
Y1 - 2018/9
N2 - 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.
AB - 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.
KW - Conglomerates
KW - Numerical modelling
KW - Strain analysis
KW - North China Craton
U2 - 10.1016/j.jsg.2018.06.018
DO - 10.1016/j.jsg.2018.06.018
M3 - Article
VL - 114
SP - 222
EP - 234
JO - Journal of Structural Geology
JF - Journal of Structural Geology
SN - 0191-8141
ER -