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

Persistent Link:
http://hdl.handle.net/10150/185423
Title:
Visible and near infrared reflectance of tuff rings and tuff cones.
Author:
Farrand, William Halsey.
Issue Date:
1991
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)
Keywords:
Dissertations, Academic; Geology -- Remote sensing.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Singer, Robert B.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleVisible and near infrared reflectance of tuff rings and tuff cones.en_US
dc.creatorFarrand, William Halsey.en_US
dc.contributor.authorFarrand, William Halsey.en_US
dc.date.issued1991en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © 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.en_US
dc.description.abstractHydrovolcanic 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.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectDissertations, Academicen_US
dc.subjectGeology -- Remote sensing.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSinger, Robert B.en_US
dc.contributor.committeememberSlater, Philen_US
dc.contributor.committeememberMarsh, Stuarten_US
dc.contributor.committeememberGlass, Charlesen_US
dc.contributor.committeememberBaker, Victor R.en_US
dc.identifier.proquest9123475en_US
dc.identifier.oclc709777800en_US
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