Petrology and Major Element Geochemistry of Albite Granite near Sparta, Oregon

Author

Robert Brayton Almy III, Western Washington University

Date Permissions Signed

5-15-2018

Date of Award

Winter 1977

Document Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Geology

First Advisor

Brown, Edwin H.

Second Advisor

Pevear, David R.

Third Advisor

Babcock, R. Scott (Randall Scott)

Abstract

Albite granite near Sparta, Oregon occurs in an igneous complex containing serpentinite, gabbro, diorite, tonalite and granite with overlying keratophyric and spilitic volcanic rocks. This igneous suite is overlain by Triassic limestones of reef origin. In all the igneous rocks primary hypidiomorphic and porphyritic textures predominate but a metamorphic overprint of the prehnite-pumpellyite facies is widespread. Whole rock chemical analyses show that albite granite has relatively high Si0₂ (69-81%) and Na₂0 (4-7%) and low K₂O (0.1-1%). Rare plagioclase potassium-feldspar granite contains up to 3.6% K₂O.

Although local isochemical alteration is demonstrable and local metasomatic replacement is probable, the albite granite body as a whole did not apparently form by metasomatic replacement of associated diorite as postulated by Gilluly (1933). Igneous contacts and variable chemical and mineralogical composition show that the Sparta granite is comprised of several bodies intruded separately but more or less contemporaneously. These intrusions were probably emplaced at shallow levels as indicated by oscillatory zoning and porphyritic textures. Albite granite and quartz keratophyre are assumed to be comagmatic on the basis of identical major element chemistry and mutually gradational textures.

The gabbro and related mafic and ultramafic rocks in northeastern Oregon may be fragments of oceanic crust. However, the albite granite and apparently cogenetic keratophyre are best interpreted to represent island arc magmatism developed on that oceanic crust.

Type

Text

Keywords

Sparta, Oregon

Publisher

Western Washington University

OCLC Number

1061199588

Subject – LCSH

Albite--Oregon--Baker County; Granite--Oregon--Baker County; Petrology--Oregon--Baker County; Geochemistry--Oregon--Baker County

Geographic Coverage

Baker County (Or.)

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.

Recommended Citation

Almy, Robert Brayton III, "Petrology and Major Element Geochemistry of Albite Granite near Sparta, Oregon" (1977). WWU Graduate School Collection. 792.
https://cedar.wwu.edu/wwuet/792