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The influence of crustal strength on rift geometry and development – insights from 3D numerical modelling

Phillips, Thomas B.; Naliboff, John B.; McCaffrey, Ken J.W.; Pan, Sophie; van Hunen, Jeroen; Froemchen, Malte

The influence of crustal strength on rift geometry and development – insights from 3D numerical modelling Thumbnail


Authors

Thomas B. Phillips

John B. Naliboff

Sophie Pan



Abstract

The lateral distribution of strength within the crust is non-uniform, dictated by crustal lithology and the presence and distribution of heterogeneities within it. During continental extension, areas of crust with distinct lithological and rheological properties manifest strain differently, influencing the structural style, geometry, and evolution of the developing rift system. Here, we use 3D thermo-mechanical models of continental extension to explore how pre-rift upper-crustal strength variations influence rift physiography. We model a  km volume containing 125 km wide domains of mechanically “strong” and “weak” upper crust along with two reference domains, based upon geological observations of the Great South Basin, New Zealand, where extension occurs parallel to the boundaries between distinct geological terranes. Crustal strength is represented by varying the initial strength of 5 km3 blocks. Extension is oriented parallel to the domain boundaries such that each domain is subject to the same 5 mm yr−1 extension rate. Our modelling results show that strain initially localises in the weak domain, with faults initially following the distribution of initial plastic strain before reorganising to produce a well-established network, all occurring in the initial 100 kyr. In contrast, little to no localisation occurs in the strong domain, which is characterised by uniform strain. We find that although faults in the weak domain are initially inhibited at the terrane boundaries, they eventually propagate through and “seed” faults in the relatively strong adjacent domains. We show characteristic structural styles associated with strong and weak crust and relate our observations to rift systems developed across laterally heterogeneous crust worldwide, such as the Great South Basin, New Zealand, and the Tanganyika Rift, East Africa.

Citation

Phillips, T. B., Naliboff, J. B., McCaffrey, K. J., Pan, S., van Hunen, J., & Froemchen, M. (2023). The influence of crustal strength on rift geometry and development – insights from 3D numerical modelling. Solid Earth, 14(4), 369-388. https://doi.org/10.5194/se-14-369-2023

Journal Article Type Article
Acceptance Date Mar 8, 2023
Online Publication Date Apr 5, 2023
Publication Date 2023
Deposit Date May 16, 2023
Publicly Available Date May 16, 2023
Journal Solid Earth
Print ISSN 1869-9510
Electronic ISSN 1869-9529
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 14
Issue 4
Pages 369-388
DOI https://doi.org/10.5194/se-14-369-2023
Public URL https://durham-repository.worktribe.com/output/1174959

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