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Mesozoic magmatism in an upper- to middle-crustal section through the Cordilleran continental margin arc, eastern Transverse Ranges, California

By
Sarah K. Needy
Sarah K. Needy
Department of Earth Sciences, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
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J. Lawford Anderson
J. Lawford Anderson
Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA
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Joseph L. Wooden
Joseph L. Wooden
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA
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R.J. Fleck
R.J. Fleck
U.S. Geological Survey, 345 Middlefield Road, Menlo Park, California 94025, USA
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Andrew P. Barth
Andrew P. Barth
Department of Earth Sciences, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
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Scott R. Paterson
Scott R. Paterson
Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA
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Valbone Memeti
Valbone Memeti
Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA
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Geoffrey S. Pignotta
Geoffrey S. Pignotta
Department of Earth Sciences, University of Southern California, Los Angeles, California 90089, USA
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Published:
January 01, 2009

The eastern Transverse Ranges provide essentially continuous exposure for >100 km across the strike of the Mesozoic Cordilleran orogen. Thermobarometric calculations based on hornblende and plagioclase compositions in Mesozoic plutonic rocks show that the first-order distribution of rock units resulted from differential Laramide exhumation. Mesozoic supracrustal rocks are preserved in the relatively little exhumed eastern part of the eastern Transverse Ranges and south-central Mojave Desert, and progressively greater rock uplift and exhumation toward the west exposed rocks originating at mid-crustal depths. The eastern Transverse Ranges thus constitute a tilted, nearly continuously exposed crustal section of the Mesozoic magmatic arc and framework rocks from subvolcanic levels to paleodepths as great as ~22 km. The base of this tilted arc section is a moderately east-dipping sheeted magmatic complex >10 km in width by 70 km in length, constructed structurally beneath, yet synchronous with Late Jurassic and Cretaceous upper-crustal plutons. Geochronology and regional structural relations thus suggest that arc magmas generated in the lower crust of this continental arc interacted in a complex mid-crustal zone of crystallization and mixing; products of this zone were parental magmas that formed relatively homogeneous upper crustal felsic plutons and fed lavas and voluminous ignimbrites.

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GSA Special Papers

Crustal Cross Sections from the Western North American Cordillera and Elsewhere: Implications for Tectonic and Petrologic Processes

Robert B. Miller
Robert B. Miller
San José State University, San José, California, USA
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Arthur W. Snoke
Arthur W. Snoke
University of Wyoming, Laramie, Wyoming, USA
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Geological Society of America
Volume
456
ISBN print:
9780813724560
Publication date:
January 01, 2009

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