• 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

    Visible and near infrared reflectance of tuff rings and tuff cones.

    • CSV
    • RefMan
    • EndNote
    • BibTex
    • RefWorks
    Thumbnail
    Name:
    azu_td_9123475_sip1_m.pdf
    Size:
    7.075Mb
    Format:
    PDF
    Description:
    azu_td_9123475_sip1_m.pdf
    Download
    Author
    Farrand, William Halsey.
    Issue Date
    1991
    Keywords
    Dissertations, Academic
    Geology -- Remote sensing.
    Advisor
    Singer, Robert B.
    
    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.
    Abstract
    Hydrovolcanic basaltic tephras from tuff rings and tuff cones were studied in order to better understand their origin and alteration processes. The visual and near infrared reflectance of tephras collected from Basin and Range tuff rings and tuff cones was measured in the laboratory. Further mineralogic and chemical information was gained through petrographic microscopy, X-ray diffraction, electron microprobe analysis and iron Mossbauer spectrometry. In addition, remotely sensed data from several airborne sensors was obtained for the Lunar Crater Volcanic Field in Nye County, Nevada and the Pavant Butte tuff cone in Millard County, Utah. Fresh tuff rings, resulting from dry pyroclastic surges, are composed of a variable mix of country rock fragments and unaltered sideromelane which has a dark reflectance spectrum dominated by Fe²⁺ crystal field bands near 1 and 2 μm. If water condenses on the sideromelane, a process of nearly syn-depositional hydration can occur. With increasing hydration, water and OH vibrational absorptions develop at 1.4 and 1.9 μm. Smectite clay minerals were recognized within thinly bedded tuff rings by the presence of a 2.2 μm absorption and by XRD results. These minerals have developed without extensive palgonitization. Tuff ring tephras can also become oxidized to the extent that a well developed Fe³⁺-O²⁻ charge transfer edge develops with weak Fe³⁺ crystal field features shortwards of 0.8 μm. The poorly inflated pyroclastic “flow”, that characterizes tuff cone formation, produces hot, wet, cohesive ash deposits that can alter relatively rapidly to palagonite. The reflectance of these highly palagonitized tephras is twice as high as that of tuff ring deposits, H₂O and OH vibrational absorption bands are also stronger and a 2.3 μm Mg-OH band is generally present. Increasing oxidation causes spectral features resulting from Fe³⁺ to become more pronounced. These include a shortwards shift in position and shallowing of the “1-μm” crystal field band and steepening of the Fe³⁺-O²⁻ charge transfer edge. Differences in spectral reflectance are ascribed primarily to differences in the degree of alteration which in turn is influenced by the water/magma ratio extant at the time of eruption. Remotely sensed data of hydrovolcanic vents acquired by several different air- and spaceborne sensors was also examined. These data sets were analyzed using a linear spectral mixture model. It was found that palagonite tuff constitutes an easily mapped spectral endmember, while the hydrated tuff typical of tuff rings is difficult to distinguish from other dark materials. The best mapping was performed with the systems with high spatial resolution such as the NSOO1 Thematic Mapper Simulator and the Geoscan Mk II advanced multispectral scanner. Airborne Visible/lnfrared Imaging Spectrometer (AVIRIS) data, calibrated to reflectance through reference endmember modelling, revealed previously undetected 2.2 μm absorption features in the palagonite tuff at Pavant Butte. The 1-μm feature in Pavant Butte palagonite tuff was mapped from the AVIRIS data using a band depth mapping routine although the resulting discrimination of palagonite tuffs was not as good as was obtained with the spectral mixture model.
    Type
    text
    Dissertation-Reproduction (electronic)
    Degree Name
    Ph.D.
    Degree Level
    doctoral
    Degree Program
    Geosciences
    Graduate College
    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.