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U-Pb geochronology of volcanic rocks from the Jurassic Talkeetna Formation and detrital zircons from prearc and postarc sequences: Implications for the age of magmatism and inheritance in the Talkeetna arc

By
Jeffrey M. Amato
Jeffrey M. Amato
1
Department of Geological Sciences, New Mexico State University, Las Cruces, New Mexico 88003, USA
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Matthew E. Rioux
Matthew E. Rioux
2
Department of Geological Sciences, University of California, Santa Barbara, California 93106, USA
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Peter B. Kelemen
Peter B. Kelemen
3
Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Palisades, New York 10964, USA
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George E. Gehrels
George E. Gehrels
4
Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA
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Peter D. Clift
Peter D. Clift
5
School of Geosciences, University of Aberdeen, Aberdeen, UK
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Terry L. Pavlis
Terry L. Pavlis
6
Department of Geological Sciences, University of Texas, El Paso, Texas 79968, USA
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Amy E. Draut
Amy E. Draut
7
Department of Earth Sciences, University of California, Santa Cruz, California 95064, USA
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Published:
January 01, 2007

Six samples collected from pre-, syn-, and post-Talkeetna arc units in south-central Alaska were dated using single-grain zircon LA-MC-ICP-MS geochronology to assess the age of arc volcanism and the presence and age of any inherited components in the arc. The oldest dated sample comes from a volcanic breccia at the base of the Talkeetna Formation on the Alaska Peninsula and indicates that initial arc volcanism began by 207 ± 5 Ma. A sedimentary rock overlying the volcanic section in the Talkeetna Mountains has a maximum depositional age of <167 Ma. This is in agreement with biochronologic ages for the top of the Talkeetna Formation, suggesting that the Talkeetna arc was active for ca. 40 m.y.

Three samples from interplutonic screens and roof pendants in the Jurassic batholith on the Alaska Peninsula provide information about the tectonic setting of Talkeetna arc magmatism. All three samples contain Paleozoic to Proterozoic zircons and require that arc magmas on the Alaska Peninsula intruded into detritus that contained older continental zircons. This finding is distinct from observations from eastern exposures of the arc in the Chugach and Talkeetna Mountains, where there is only limited evidence for pre-Paleozoic zircons, and it suggests that there were along-strike variations in the tectonic setting of the arc.

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Contents

GSA Special Papers

Tectonic Growth of a Collisional Continental Margin: Crustal Evolution of Southern Alaska

Kenneth D. Ridgway
Kenneth D. Ridgway
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Jeffrey M. Trop
Jeffrey M. Trop
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Jonathan M.G. Glen
Jonathan M.G. Glen
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J. Michael O'Neill
J. Michael O'Neill
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Geological Society of America
Volume
431
ISBN print:
9780813724317
Publication date:
January 01, 2007

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