Geology and petrology of the Parkdale Gneiss, Fremont County, Colorado

dc.creatorSchaefer, William Alvin
dc.date.accessioned2016-11-14T23:26:38Z
dc.date.available2011-02-18T22:00:06Z
dc.date.available2016-11-14T23:26:38Z
dc.date.issued1969-12
dc.degree.departmentGeologyen_US
dc.description.abstractThe Farkdale Gneiss in Fremont County, Colorado, Is a massive homogeneous rock unit 9 miles long and 4 1/2 miles wide. The massiveness, homogenity, lack of relic structures, and porphyroblastic texture suggest an original igneous intrusive body. The long axis is in a north-south direction which is characteristic of the regional structural trends in the Colorado Front Range and Wet Mountains. The north-south strike of the enclosing metasedimentary rocks suggests the bedding served as a guide to the emplacement of the Farkdale unit. The Farkdale Gneiss changes character from a strongly foliated, dark-gray gneiss in the southern part of the unit and a weakly foliated, pinkish-gray gneiss in the northern area. Mode analysis and zircon study indicate the two rock types to be members of the same intrusive body. Petrographic work shows that a gradation exists between the two rock types. The prophyroplastic character and pinkish color of the rock in the northern area are accompanied by a gradational increase in potassium-feldspar and corresponding decrease in biotite. It is postulated that the breakdown of biotite during subsequent metamorphism produced the potassium ion needed for the porphyr9blasts of potassium-feldspar.
dc.format.mimetypeapplication/pdf
dc.identifier.urihttp://hdl.handle.net/2346/17359en_US
dc.language.isoeng
dc.publisherTexas Tech Universityen_US
dc.rights.availabilityUnrestricted.
dc.subjectPetrology -- Colorado -- Parkdale Gneissen_US
dc.subjectGeology -- Colorado -- Parkdale Gneissen_US
dc.titleGeology and petrology of the Parkdale Gneiss, Fremont County, Colorado
dc.typeThesis

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