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Middle Cambrian to Ordovician arc-backarc development on the leading edge of Ganderia, Newfoundland Appalachians

By
A. Zagorevski
A. Zagorevski
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, K1A0E8, Canada
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C.R. van Staal
C.R. van Staal
Geological Survey of Canada, 625 Robson Street, Vancouver, British Columbia, V6B 5J3, Canada
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N. Rogers
N. Rogers
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, K1A0E8, Canada
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V.J. McNicoll
V.J. McNicoll
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario, K1A0E8, Canada
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J. Pollock
J. Pollock
Department of Earth Sciences, Mount Royal University, Calgary, Alberta, T3E 6K6, Canada
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Published:
September 2010

The evolution of many modern intra-oceanic and continental arc systems is exemplified by cycles of arc construction, rifting, and separation of remnant and active arcs by a backarc basin floored by oceanic crust. Rifted arc complexes and backarc basins are inherently subductable, and hence only a fragmentary record of rifting and arc construction is preserved in the ancient record. In this contribution, we synthesize available geochronological, geochemical, isotopic, and stratigraphic data in order to discuss the evolution of the Cambrian to Ordovician Penobscot-Victoria Arc, which developed on the leading edge of Ganderia, a peri-Gondwanan microcontinent. Although the Penobscot and Victoria stages of arc-backarc development occurred in a predominantly extensional suprasubduction-zone setting, they each display a distinctly different character of magmatism and sedimentation. These stages are separated by an orogenic episode marked by the obduction of backarc ophiolites onto the Ganderian passive margin. The Cambrian to Lower Ordovician Penobscot Arc is characterized by the continuous migration of the magmatic front and development of multiple volcanically active rift zones. The rift basins display a variety of characteristics, including bimodal calc-alkaline magmatism, felsic-dominated incipient rift magmatism, and formation of rifts floored by tholeiitic to boninitic suprasubduction-zone ophiolite. Comparison to modern analogues suggests that part of the Penobscot Arc area developed in a similar setting to the volcanically active Havre Trough and Taupo volcanic zone. In contrast, the Victoria Arc phase was dominated by multiple epiclastic rich, volcano-sedimentary basins overlying tectonically modified Penobscot basement. Igneous rocks are sparse, typified by calc-alkaline felsic volcanic and tholeiitic to alkaline backarc basin basalts. The change in character of the backarc volcanic rocks over time is interpreted to reflect multiple tectonic factors, including the variation of slab retreat rate, degree of extension in the arc (Cambrian Penobscot Arc) versus the backarc basin (Ordovician Exploits-Tetagouche backarc), reactivation of inverted Penobscot extensional faults during Middle Ordovician rifting, and/or depletion of fertile components by the Middle Ordovician.

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Contents

GSA Memoirs

From Rodinia to Pangea: The Lithotectonic Record of the Appalachian Region

Edited by
Richard P. Tollo
Richard P. Tollo
Geological Sciences Program, George Washington University, Washington, D.C., USA
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Mervin J. Bartholomew
Mervin J. Bartholomew
Department of Earth Sciences, University of Memphis, Memphis, Tennessee, USA
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James P. Hibbard
James P. Hibbard
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina, USA
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Paul M. Karabinos
Paul M. Karabinos
Department of Geosciences, Williams College, Williamstown, Massachusetts, USA
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Geological Society of America
Volume
206
ISBN print:
9780813712062
Publication date:
2010

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