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Deformation structures associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for sill and laccolith emplacement mechanisms

Wilson, P.I.R.; McCaffrey, K.J.W.; Wilson, R.W.W.; Jarvis, I.; Holdsworth, R.E.

Deformation structures associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for sill and laccolith emplacement mechanisms Thumbnail


Authors

P.I.R. Wilson

R.W.W. Wilson

I. Jarvis



Abstract

Deformation structures in the wall rocks of igneous intrusions emplaced at shallow crustal depths preserve an important record of how space was created for magma in the host rocks. Trachyte Mesa, a small Oligocene age intrusion in the Henry Mountains, Utah, is composed of a series of stacked tabular, sheet-like intrusions emplaced at 3–3.5 km depth into sandstone-dominated sedimentary sequences of late Palaeozoic–Mesozoic age. New structural analysis of the spatial distribution, geometry, kinematics and relative timings of deformation structures in the host rocks of the intrusion has enabled the recognition of distinct pre-, syn-, and late-stage-emplacement deformation phases. Our observations suggest a two-stage growth mechanism for individual sheets where radial growth of a thin sheet was followed by vertical inflation. Dip-slip faults formed during vertical inflation; they are restricted to the tips of individual sheets due to strain localisation, with magma preferentially exploiting these faults, initiating sill (sheet) climbing. The order in which sheets are stacked impacts on the intrusion geometry and associated deformation of wall rocks. Our results offer new insights into the incremental intrusion geometries of shallow-level magmatic bodies and the potential impact of their emplacement on surrounding host rocks.

Citation

Wilson, P., McCaffrey, K., Wilson, R., Jarvis, I., & Holdsworth, R. (2016). Deformation structures associated with the Trachyte Mesa intrusion, Henry Mountains, Utah: Implications for sill and laccolith emplacement mechanisms. Journal of Structural Geology, 87, 30-46. https://doi.org/10.1016/j.jsg.2016.04.001

Journal Article Type Article
Acceptance Date Apr 5, 2016
Online Publication Date Apr 7, 2016
Publication Date Jun 1, 2016
Deposit Date Apr 7, 2016
Publicly Available Date Apr 7, 2017
Journal Journal of Structural Geology
Print ISSN 0191-8141
Electronic ISSN 1873-1201
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 87
Pages 30-46
DOI https://doi.org/10.1016/j.jsg.2016.04.001
Public URL https://durham-repository.worktribe.com/output/1387187

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