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Date Permissions Signed

5-24-2018

Date of Award

Fall 1973

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Babcock, R. Scott (Randall Scott)

Second Advisor

Brown, Edwin H.

Third Advisor

Ellis, Ross C.

Abstract

The study area extends from Phantom Creek to Crystal Creek, a distance of approximately 10 miles along the Colorado River. The units exposed are the Precambrian Vishnu Schist granitic to granodioritic units in Phantom Canyon, Trinity Canyon, and near Crystal Creek, and pegmatites and aplites. The Vishnu Schist is composed mostly of quartzo-feldspathic schists. The assemblage quartz-oligoclase-muscovite-biotite-sillimanite-K-feldspar indicates metamorphic conditions in the upper amphibolite facies between Phantom Creek and Mile 95. Between Mile 95 and Crystal Creek, assemblages indicate lower amphibolite to greenschist facies conditions.

The Phantom Granitic Complex consists of granodioritic and quartz monzonitic units. The presence of a contact breccia, rotated xenoliths, and cross-cutting apophyses indicate the pluton is intrusive. The rocks cluster around the 3 kb cotectic in the Ab-Or-Qtz system which suggests a magmatic origin.

The Trinity Gneiss is a homogeneous granodioritic gneiss. Intercalated layers of quartzite and schist and calc-silicate lenses support a meta-sedimentary origin. Chemical data suggest that the biotite-rich layers are meta-sedimentary but the granitic layers plot along cotectic troughs and may represent rhyolitic or rhyodacitic flows.

The Crystal Creek Granite is a post-tectonic, epidoterich granitic rock. Field evidence suggest the pluton is intrusive. Quartz and schistose inclusions and the unusual mineralogical and chemical composition suggest the granite has been contaminated. Late low grade metamorphism has resulted in dominantly metamorphic textures.

The Vishnu Schist has been cut by pegmatite and aplite dikes. Apophyses and cross-cutting relationships indicate the pegmatite/aplites are intrusive. Chemical data clusters around the cotectic minimums in the Ab-0r-Qtz-H20 system suggesting a magmatic source. Large crystals and quartz cores suggest the pegmatites are of hydrothermal origin.

Type

Text

Keywords

Petrogenesis, Precambrian Vishnu Schist

Publisher

Western Washington University

OCLC Number

1084668311

Subject – LCSH

Granite; Geochemistry; Petrology--Arizona--Grand Canyon

Geographic Coverage

Grand Canyon (Ariz.)

Format

application/pdf

Genre/Form

masters theses

Language

English

Rights

Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.

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