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Perspectives on the architecture of continental crust from integrated field studies of exposed isobaric sections

Michael L. Williams, Karl E. Karlstrom, Gregory Dumond and Kevin H. Mahan
Perspectives on the architecture of continental crust from integrated field studies of exposed isobaric sections (in Crustal cross sections; from the western North American Cordillera and elsewhere; implications for tectonic and petrologic processes, Robert B. Miller (editor) and Arthur W. Snoke (editor))
Special Paper - Geological Society of America (2009) 456: 219-241

Abstract

Depth-dependent variations in the structure and composition of continental crust can be studied via integrated investigations of isobaric terranes. In this contribution, we summarize three isobaric terranes in Archean to Proterozoic crust. In western Canada, 35-45-km-deep lower crust is exposed over an area of more than 20,000 km2. The Upper Granite Gorge of Grand Canyon, Arizona, provides a transect of 20-25-km-deep middle crust. The Proterozoic basement of central Arizona represents an isobaric exposure of 10-15-km-deep middle crust. Isobaric terranes yield a conceptual image of continental crust that can be compared to seismic images, xenolith data, and drill core data to clarify rheology, coupling/decoupling of crustal levels, and the interplay between deformation, metamorphism, and plutonism. General observations include: (1) The crust is heterogeneous at all levels and cannot be accurately modeled as a simple progression from quartz-rich to feldspar-rich lithologies or from felsic to mafic bulk compositions. (2) The crust is segmented into foliation domains that alternate between steeply dipping and shallowly dipping. (3) Magmatism is expressed differently at different depths due to different background temperatures and a general upward distillation from mafic to felsic composition, and may be the most important control on crustal architecture and rheology. The strength of continental crust (and its potential for low-viscosity flow) is not simply a function of temperature, depth, and compositional layering, but is controlled by the size and distribution of rheological domains. The rheological character of a particular layer can vary in space and time at any crustal level.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 456
Title: Perspectives on the architecture of continental crust from integrated field studies of exposed isobaric sections
Title: Crustal cross sections; from the western North American Cordillera and elsewhere; implications for tectonic and petrologic processes
Author(s): Williams, Michael L.Karlstrom, Karl E.Dumond, GregoryMahan, Kevin H.
Author(s): Miller, Robert B.editor
Author(s): Snoke, Arthur W.editor
Affiliation: University of Massachusetts, Department of Geosciences, Amherst, MA, United States
Affiliation: San Jose State University, Department of Geology, San Jose, CA, United States
Pages: 219-241
Published: 2009
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 124
Accession Number: 2010-004839
Categories: Solid-earth geophysicsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., geol. sketch maps
N34°00'00" - N35°00'00", W113°00'00" - W111°00'00"
N36°01'60" - N36°01'60", W117°25'00" - W117°25'00"
N59°00'00" - N60°00'00", W107°00'00" - W105°00'00"
Secondary Affiliation: University of Wyoming, USA, United StatesUniversity of New Mexico, USA, United StatesCalifornia Institute of Technology, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 201003
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