• Login
    View Item 
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    •   Home
    • UA Graduate and Undergraduate Research
    • UA Theses and Dissertations
    • Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

    All of UA Campus RepositoryCommunitiesTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournalThis CollectionTitleAuthorsIssue DateSubmit DateSubjectsPublisherJournal

    My Account

    LoginRegister

    About

    AboutUA Faculty PublicationsUA DissertationsUA Master's ThesesUA Honors ThesesUA PressUA YearbooksUA CatalogsUA Libraries

    Statistics

    Most Popular ItemsStatistics by CountryMost Popular Authors

    Timing and Rates of Precambrian Crustal Genesis and Deformation in Northern South America

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    etd_13574_sip1_m.pdf
    Size:
    53.39Mb
    Format:
    PDF
    Download
    Author
    Ibanez-Mejia, Mauricio
    Issue Date
    2014
    Keywords
    Geosciences
    Advisor
    Ruiz, Joaquin
    Gehrels, George E.
    
    Metadata
    Show full item record
    Publisher
    The University of Arizona.
    Rights
    Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
    Embargo
    Release 26-Nov-2017
    Abstract
    The Amazon Craton is one of the largest Precambrian landmasses on Earth, yet its crustal growth history and evolution are relatively poorly constrained. This dissertation addresses the timing and modes of continental growth and deformation of a sizable portion of the central and western Guyana Shield, mostly using a combination of texturally-resolved U-Pb, Lu-Hf and δ¹⁸O analysis of zircon. These results provide a wealth of new information that have major implications for the role of Amazonia in Precambrian supercontinent models, its significance in the global record of crustal generation and the possible tectonic processes that were involved in its construction. It is argued that, contrary to the previously accepted Proterozoic accretionary model for the growth of northwestern Amazonia, the new data suggest that sizable portions of the shield formed during an episodic extraction event in the Neorchean. This hypothesis challenges the current tectonic model for the evolution of Amazonia, and provides evidence for the continued importance that mechanisms inducing episodic crustal generation had after subduction-driven plate tectonics had been established on Earth. During the last decade, the study of crustal growth processes by means of U-Pb-Hf-O analysis of zircon has considerably improved our understanding of the mechanisms that drive planetary differentiation. However, zircon has a significant limitation, and is that basic and ultrabasic rocks have very low fertility to form this mineral owing to their low SiO₂ composition. Therefore, the global zircon U-Pb-Hf repository is biased towards the felsic portion of the crust, leaving the mafic archive mostly unconstrained. Undersaturated rocks can form baddeleyite, a phase with high affinity for Hf and U, low affinity for Yb, Lu and Pb, and slow diffusion rates with respect to all these chemical species. Consequently, baddeleyite is an extremely robust carrier of geochronological (by using the U-Pb system) and tracer (by using the Lu-Hf system) information for the origin of mafic rocks. This dissertation provides a method for the fast, accurate and precise analysis of U-Pb-Hf isotopes in baddeleyite, a tool that in the future may prove crucial for studying the timing and processes associated with the formation of mafic crust on Earth.
    Type
    text
    Electronic Dissertation
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Graduate College
    Geosciences
    Degree Grantor
    University of Arizona
    Collections
    Dissertations

    entitlement

     
    The University of Arizona Libraries | 1510 E. University Blvd. | Tucson, AZ 85721-0055
    Tel 520-621-6442 | repository@u.library.arizona.edu
    DSpace software copyright © 2002-2017  DuraSpace
    Quick Guide | Contact Us | Send Feedback
    Open Repository is a service operated by 
    Atmire NV
     

    Export search results

    The export option will allow you to export the current search results of the entered query to a file. Different formats are available for download. To export the items, click on the button corresponding with the preferred download format.

    By default, clicking on the export buttons will result in a download of the allowed maximum amount of items.

    To select a subset of the search results, click "Selective Export" button and make a selection of the items you want to export. The amount of items that can be exported at once is similarly restricted as the full export.

    After making a selection, click one of the export format buttons. The amount of items that will be exported is indicated in the bubble next to export format.