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Continental growth and recycling by accretion of deformed turbidite fans and remnant ocean basins: Examples from Neoproterozoic and Phanerozoic orogens

By
David R. Gray
David R. Gray
School of Earth Sciences, University of Melbourne, Melbourne 3010, Victoria, Australia
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David A. Foster
David A. Foster
School of Geological Sciences, University of Florida, Gainesville, Florida 32611-2120, USA
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Roland Maas
Roland Maas
School of Earth Sciences, University of Melbourne, Melbourne 3010, Victoria, Australia
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Catherine V. Spaggiari
Catherine V. Spaggiari
Geological Survey of Western Australia, Perth 6004, Western Australia, Australia
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Robert T. Gregory
Robert T. Gregory
Department of Geological Sciences, Southern Methodist University, Dallas, Texas 75275, USA
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Ben Goscombe
Ben Goscombe
School of Earth and Environmental Sciences, University of Adelaide, Adelaide 5005, South Australia, Australia
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K.H. (Charlie) Hoffmann
K.H. (Charlie) Hoffmann
Namibian Geological Survey, Private Bag 13297, Windhoek, Namibia
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Published:
January 01, 2007

Convergent margin tectonic settings involving accretion of large turbidite fans represent important sites of growth and regeneration of continental crust. The newly accreted continental crust consists of an upper crustal layer of recycled crustal detritus (turbidites) underlain by a lower crustal layer of tectonically imbricated oceanic crust, and/or rifted and thinned continental crust, along with underplated magmatic materials; the new lower crust represents additions to continental crustal volume differentiated from the mantle. This two-tiered crust is of average continental crustal thickness and is isostatically balanced near sea level, resulting in remarkable stability. The Paleozoic Tasman orogen of eastern Australia is the archetypal example of this style of orogeny, representing continental growth rates of cubic kilometers per year of material that does not return to the mantle by oceanic plate-tectonic recycling. The Neoproterozoic Pan-African Damara orogen of SW Africa is a similar orogen, whereas the Mesozoic Rangitatan orogen or Rakaia wedge of New Zealand illustrates the transition of the convergent margin from a Lachlan-type to more recognizable “ring of fire”-type orogen. These orogens illustrate continental growth from the shortening of deep marine successions and their oceanic crustal basement involving subduction-accretion. The spatial and temporal variations in deformation, metamorphism, and magmatism across these orogens illustrate how large volumes of monotonous turbidites and their relict oceanic basement eventually become stable continental crust. The timing of deformation and metamorphism reflect the crustal thickening phase, whereas the posttectonic granitoids and surficial volcanic deposits give the timing of cratonization. The turbidites represent fertile sources for crustal melting and are the main sources for the S-type granites.

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Contents

GSA Memoirs

4-D Framework of Continental Crust

Robert D. Hatcher, Jr.
Robert D. Hatcher, Jr.
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Marvin P. Carlson
Marvin P. Carlson
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John H. McBride
John H. McBride
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José R. Martínez Catalán
José R. Martínez Catalán
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Geological Society of America
Volume
200
ISBN print:
9780813712000
Publication date:
January 01, 2007

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