Masoch, S;
Gomila, R;
Fondriest, M;
Jensen, E;
Mitchell, T;
Pennacchioni, G;
Cembrano, J;
(2021)
Structural evolution of a crustal‐scale seismogenic fault in a magmatic arc: The Bolfin Fault Zone (Atacama Fault System).
Tectonics
, 40
(8)
, Article e2021TC006818. 10.1029/2021tc006818.
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Abstract
How major crustal-scale seismogenic faults nucleate and evolve in crystalline basements represents a long-standing, but poorly understood, issue in structural geology and fault mechanics. Here, we address the spatio-temporal evolution of the Bolfin Fault Zone (BFZ), a >40-km-long exhumed seismogenic splay fault of the 1000-km-long strike-slip Atacama Fault System. The BFZ has a sinuous fault trace across the Mesozoic magmatic arc of the Coastal Cordillera (Northern Chile) and formed during the oblique subduction of the Aluk plate beneath the South American plate. Seismic faulting occurred at 5–7 km depth and ≤ 300°C in a fluid-rich environment as recorded by extensive propylitic alteration and epidote-chlorite veining. Ancient (125–118 Ma) seismicity is attested by the widespread occurrence of pseudotachylytes. Field geologic surveys indicate nucleation of the BFZ on precursory geometrical anisotropies represented by magmatic foliation of plutons (northern and central segments) and andesitic dyke swarms (southern segment) within the heterogeneous crystalline basement. Seismic faulting exploited the segments of precursory anisotropies that were optimal to favorably oriented with respect to the long-term far-stress field associated with the oblique ancient subduction. The large-scale sinuous geometry of the BFZ resulted from the hard linkage of these anisotropy-pinned segments during fault growth.
| Type: | Article |
|---|---|
| Title: | Structural evolution of a crustal‐scale seismogenic fault in a magmatic arc: The Bolfin Fault Zone (Atacama Fault System) |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1029/2021tc006818 |
| Publisher version: | https://doi.org/10.1029/2021TC006818 |
| Language: | English |
| Additional information: | © Wiley Periodicals LLC. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10131943 |
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