Influence of crystallised igneous intrusions on fault nucleation and reactivation during continental extension

Craig Magee, Kenneth G. McDermott, Carl T E Stevenson, Christopher A L Jackson

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)
217 Downloads (Pure)

Abstract

Continental rifting is commonly accommodated by the nucleation of normal faults, slip on pre-existing fault surfaces and/or magmatic intrusion. Because crystallised igneous intrusions are pervasive in many rift basins and are commonly more competent (i.e. higher shear strengths and Young's moduli) than the host rock, it is theoretically plausible that they locally intersect and modify the mechanical properties of pre-existing normal faults. We illustrate the influence that crystallised igneous intrusions may have on fault reactivation using a conceptual model and observations from field and subsurface datasets. Our results show that igneous rocks may initially resist failure, and promote the preferential reactivation of favourably-oriented, pre-existing faults that are not spatially-associated with solidified intrusions. Fault segments situated along strike from laterally restricted fault-intrusion intersections may similarly be reactivated. This spatial and temporal control on strain distribution may generate: (1) supra-intrusion folds in the hanging wall; (2) new dip-slip faults adjacent to the igneous body; or (3) sub-vertical, oblique-slip faults oriented parallel to the extension direction. Importantly, stress accumulation within igneous intrusions may eventually initiate failure and further localise strain. The results of our study have important implications for the structural of sedimentary basins and the subsurface migration of hydrocarbons and mineral-bearing fluids.

Original languageEnglish
Pages (from-to)183-193
Number of pages11
JournalJournal of Structural Geology
Volume62
Early online date22 Feb 2014
DOIs
Publication statusPublished - May 2014

Keywords

  • Continental rift
  • Dyke
  • Igneous intrusion
  • Normal fault
  • Reactivation
  • Sill

ASJC Scopus subject areas

  • Geology

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