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Date Permissions Signed
Date of Award
Master of Science (MS)
Brown, Edwin H.
Pevear, David R.
Babcock, R. Scott (Randall Scott)
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.
Western Washington University
Subject – LCSH
Albite--Oregon--Baker County; Granite--Oregon--Baker County; Petrology--Oregon--Baker County; Geochemistry--Oregon--Baker County
Baker County (Or.)
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.
Almy, Robert Brayton III, "Petrology and Major Element Geochemistry of Albite Granite near Sparta, Oregon" (1977). WWU Graduate School Collection. 792.