Skip to Main Content
Book Chapter

Emplacement and assembly of shallow intrusions from multiple magma pulses, Henry Mountains, Utah

By
Eric Horsman
Eric Horsman
University of Wisconsin–Madison, Madison, Wisconsin, USA
Search for other works by this author on:
Sven Morgan
Sven Morgan
Central Michigan University, Mt Pleasant, Michigan, USA
Search for other works by this author on:
Michel de Saint-Blanquat
Michel de Saint-Blanquat
CRNS-LMTG, Observatoire Midi-Pyrénées, Université Paul-Sabatier, Toulouse, France
Search for other works by this author on:
Guillaume Habert
Guillaume Habert
CRNS-LMTG, Observatoire Midi-Pyrénées, Université Paul-Sabatier, Toulouse, France
Search for other works by this author on:
Andrew Nugent
Andrew Nugent
Central Michigan University, Mt Pleasant, Michigan, USA
Search for other works by this author on:
Robert A. Hunter
Robert A. Hunter
University of Wisconsin–Madison, Madison, Wisconsin, USA
Search for other works by this author on:
Basil Tikoff
Basil Tikoff
University of Wisconsin–Madison, Madison, Wisconsin, USA
Search for other works by this author on:
Published:
October 01, 2010

This paper describes three mid-Tertiary intrusions from the Henry Mountains (Utah, USA) that were assembled from amalgamation of multiple horizontal sheet-like magma pulses in the absence of regional deformation. The three-dimensional intrusion geometries are exceptionally well preserved and include: (1) a highly lobate sill; (2) a laccolith; and (3) a bysmalith (a cylindrical, fault-bounded, piston-like laccolith). Individual intrusive sheets are recognised on the margins of the bodies by stacked lobate contacts, and within the intrusions by both intercalated sedimentary wallrock and formation of solid-state fabrics. Finally, conduits feeding these intrusions were mostly sub-horizontal and pipe-like, as determined by both direct observation and modelling of geophysical data.

The intrusion geometries, in aggregate, are interpreted to reflect the time evolution of an idealised upper crustal pluton. These intrusions initiate as sills, evolve into laccoliths, and eventually become piston-like bysmaliths. The emplacement of multiple magma sheets was rapid and pulsed; the largest intrusion was assembled in less than 100 years. The magmatic fabrics are interpreted as recording the internal flow of the sheets preserved by fast cooling rates in the upper crust. Because there are multiple magma sheets, fabrics may vary vertically as different sheets are traversed. These bodies provide unambiguous evidence that some intrusions are emplaced in multiple pulses, and that igneous assembly can be highly heterogeneous in both space and time. The features diagnostic of pulsed assembly observed in these small intrusions can be easily destroyed in larger plutons, particularly in tectonically active regions.

You do not currently have access to this article.

Figures & Tables

Contents

GSA Special Papers

Sixth Hutton Symposium on The Origin of Granites and Related Rocks: Proceedings of a Symposium held in Stellenbosch, South Africa, 2- 6 July 2007

John D. Clemens
John D. Clemens
Department of Earth Sciences, University of Stellenbosch, South Africa
Search for other works by this author on:
Colin Donaldson
Colin Donaldson
EESTRSE Editor:
Search for other works by this author on:
Carol D. Frost
Carol D. Frost
Guest Editors:
Search for other works by this author on:
Alexander F.M. Kisters
Alexander F.M. Kisters
Guest Editors:
Search for other works by this author on:
Jean-François Moyen
Jean-François Moyen
Guest Editors:
Search for other works by this author on:
Tracy Rushmer
Tracy Rushmer
Guest Editors:
Search for other works by this author on:
Gary Stevens
Gary Stevens
Guest Editors:
Search for other works by this author on:
Geological Society of America
Volume
472
ISBN print:
9780813724720
Publication date:
October 01, 2010

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal