The Neoproterozoic-Early Paleozoic Tectonic Evolution of the Peri-Gondwanan Margin of the Appalachian orogen: An Integrated Geochronological, Geochemical and Isotopic Study from North Carolina and Newfoundland

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dc.contributor.advisor Dr. Brent Miller, Committee Member en_US
dc.contributor.advisor Dr. James Hibbard, Committee Chair en_US
dc.contributor.advisor Dr. John Fountain, Committee Member en_US
dc.contributor.advisor Dr. Kevin Stewart, Committee Member en_US Pollock, Jeffrey Charles en_US 2010-04-02T19:13:47Z 2010-04-02T19:13:47Z 2008-02-27 en_US
dc.identifier.other etd-10212007-215626 en_US
dc.description.abstract LAM-ICP-MS U-Pb dates are reported from more than 1000 detrital zircons from the Neoproterozoic-early Paleozoic clastic sequences of Carolinia and Avalonia. The majority of analyzed zircon grains from Carolinia are late Neoproterozoic with minor amounts of Mesoproterozoic⁄Paleozoic and accessory Archean grains. The overall distribution of age populations of detrital zircons is consistent with derivation from the Amazonian craton and its peripheral orogenic belts on the margin of west Gondwana. The dominance of Ediacaran-early Paleozoic zircons in the Albemarle sequence suggests an underlying local protosource and deposition occurring synchronously with arc magmatism. Neoproterozoic rocks of the type area of Avalonia are dominated by Ediacaran zircons. Early Paleozoic platform units contain an abundance of grains that have ages between 1.0-1.6 Ga, with lesser Paleoproterozoic and Archean zircons. These ages are inconsistent with recycling from underlying Neoproterozoic rocks and indicate that Avalonia's provenance is a Gondwanan craton that contains Archean, Paleo-, Meso- and Neoproterozoic rocks. These data are inconsistent with a West African provenance and suggest that Avalonia originated along the margin of the Amazonian craton. The prominent change in provenance is interpreted to be related to separation of Avalonia from Gondwana during the Early Ordovician opening of the Rheic Ocean. In central North Carolina, mafic rocks of the Stony Mountain gabbro are characterized by variable LREE enrichment, prominent negative Nb anomalies and low Nb⁄Th ratios; features of tholeiitic basalts in modern island-arc, subduction related lavas. Nd isotope data indicate juvenile magmas consistent with derivation from lithospheric and asthenospheric sources during decompression melting of the mantle. The Stony Mountain gabbro can be modeled as the product of 10–15% hydrous partial melting of variable mixtures of MORB- and OIB-like mantle sources overprinted by a minor subducted-slab derived hydrous fluid component. By analogy with modern settings the Stony Mountain gabbro are comparable to MORB-like to OIB-type enriched rocks from the Lau Island and Sumisu Rift and are interpreted to have formed within an evolving early Paleozoic island arc–back arc rift-basin system. The presence of an Early Cambrian arc-back arc rift system in Carolinia is broadly coeval with arc-back arc volcanism in other peri-Gondwanan blocks of the Appalachians and may be related to the Early Paleozoic opening of the Rheic Ocean. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dis sertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject lithogeochemistry en_US
dc.subject radiogenic isotope geochemistry en_US
dc.subject U-Pb geochronology en_US
dc.subject Avalonia en_US
dc.subject Appalachian geology en_US
dc.subject Carolinia en_US
dc.title The Neoproterozoic-Early Paleozoic Tectonic Evolution of the Peri-Gondwanan Margin of the Appalachian orogen: An Integrated Geochronological, Geochemical and Isotopic Study from North Carolina and Newfoundland en_US PhD en_US dissertation en_US Marine, Earth and Atmospheric Sciences en_US

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