The development of cavities and clastic infills along fault-related fractures in Tertiary basalts on the NE Atlantic margin

Walker, Richard James, Holdsworth, Robert E., Imber, J. and Ellis, D. 2011. The development of cavities and clastic infills along fault-related fractures in Tertiary basalts on the NE Atlantic margin. Journal of Structural Geology 33 (2) , pp. 92-106. 10.1016/j.jsg.2010.12.001

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Abstract

Field-based geological observations have revealed the hitherto unrecognised development of post-magmatic, brittle deformation structures cutting Tertiary volcanic rocks in the Faroe Islands. These faults and fractures are characteristically associated with different styles of clastic sedimentary infill including: 1) 0.3–1.0 m thick clastic units infilling open fractures formed along pre-existing steeply-dipping to sub-vertical faults; 2) 0.1–0.6 m thick sub-horizontal clastic units displaying internal features consistent with deposition from flowing water passing through complex open subterranean cavity systems within fractured basalts; 3) Anastomosing mm-scale and planar dm-scale clastic intrusion features mobilised and emplaced during transient, fault-related overpressuring events along pre-existing fractures cutting the surrounding volcanic units. The infill features provide evidence for the existence of sustained open cavities in the sub-surface. The clastic materials are commonly internally affected by later fault-related deformation and lack mineralisation, unlike all preceding faulting episodes in the Faroes region, perhaps reflecting their near-surface development. We believe structures equivalent to these features may occur widely in other parts of the NE Atlantic margin, particularly along the outer arcs of gentle regional-scale fold hinges. The uncemented fracture-hosted clastic infills potentially represent important fluid migration pathways within the otherwise low permeability Cenozoic volcanic sequences of the NE Atlantic region.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Subjects:	G Geography. Anthropology. Recreation > GC Oceanography Q Science > QE Geology
Uncontrolled Keywords:	NE Atlantic; Passive margin; Clastic intrusion; Clastic infill; Faults in basalt
Publisher:	Elsevier
ISSN:	0191-8141
Last Modified:	19 Mar 2016 22:18
URI:	https://orca.cardiff.ac.uk/id/eprint/11312

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