Western Washington University Western CEDAR WWU Graduate School Collection WWU Graduate and Undergraduate Scholarship Winter 1977 Petrology and Major Element Geochemistry of Albite Granite near Sparta, Oregon Robert Brayton Almy III Western Washington University Follow this and additional works at: https://cedar.wwu.edu/wwuet Part of the Geochemistry Commons, and the Geology Commons 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 This Masters Thesis is brought to you for free and open access by the WWU Graduate and Undergraduate Scholarship at Western CEDAR. It has been accepted for inclusion in WWU Graduate School Collection by an authorized administrator of Western CEDAR. For more information, please contact [email protected]. PETROLOGY AND MAJOR ELEMENT GEOCHEMISTRY OFJ\LBITE GRANITE NEAR SPARTA, OREGON A Thesis ' Presented to The Faculty of Western Washington State College In Partial Fulfillment Of the Requirements for the Degree Master of Science by Robert B. Almy III March, 1977 345c 112 MASTER'S THESIS In presenting this thesis in partial fulfillment of the requirements for a master's degree at Western Washington University, I grant to Western Washington University the non-exclusive royalty-free rightto archive, reproduce, distribute, and display the thesis in any and all forms, including electronic format, via any digital library mechanisms maintained by WWU. I represent and w/arrant this is rhy original work and does not infringe or violate any rights of others. I warrant that I have obtained written permissions from the owner of any third party copyrighted material included in these files. I acknowledge that I retain ownership rights to the copyright of this work, including but not limited to the rightto use all or part of this work in future works, such as articles or books. Library users are granted permission for individual, research and non-commercial reproduction of this work for educational purposes only. Any further digital posting of this document requires specific permission from the author. Any copying or publication of this thesis for commercial purposes, or for financial gain, is not allowed without my written permission. Date: I PETROLOGY AND MAJOR ELEMENT GEOCHEMISTRY OF ALBITE GRANITE NEAR SPARTA, OREGON by Robert B. Altny III Accepted in Partial Completion of the Requirements for the Degree Master of Science Dean of Graduate School ADVISORY COMMITTEE Chairperson ABSTRACT Albite granite near Sparta, Oregon occurs in an igneous complex con­ taining 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. TABLE OF CONTENTS ABSTRACT LIST OF FIGURES LIST OF PLATES LIST OF TABLES INTRODUCTION ‘ ^ ACCESS GENERAL GEOLOGY ^ Paleozoic Rocks 7 Mesozoic Plutonic Rocks 7 Mesozoic Sedimentary Rocks -jO Jurassic-Cretaceous Plutonic Rocks -12 Tertiary Unconformity and Post-Cretaceous Rocks 12 PURPOSE 13 FIELD RELATIONS AND PETROGRAPHY OF UNITS STUDIED Gabbro 13 Diorite and Tonalite 15 Granite 21 Clover Creek Greenstone 31 Dikes 35 WHOLE ROCK CHEMICAL ANALYSES Method 40 Discussion 40 METASOMATISM Gilluly's Theory 49 Evidence of the Present Study 51 Field Evidence 5I Textural Alteration 52 Chemical Evidence 53 Discussion 54 Summary of Alteration Data 61 CONCLUSIONS ACKNOWLEDGEMENTS BIBLIOGRAPHY APPENDIX I APPENDIX II LIST OF FIGURES Figure Page 1 Location of the study area. 2 2 Previous study areas. 3 3 Typical vegetation cover on the northern portion of Sparta uplands, Wallowa Mountains in the background. 4 4 Typical exposure along Goose Creek near Sucker Creek. 4 5 Shallow gorge of the Powder River, 25 kilometers west of Richland, Oregon on State Route 89. 5 6 Flat undissected uplands near Sparta, Oregon in the middle background, view is toward the west. 5 7 Generalized stratographic section of pre-Tertiary geology near Sparta, Oregon. 6 8 Regional occurrence of major orogenic events in the northwestern United States, from Rogers et al (1974), p. 1922. 9 9 Sketch map of the regional geology of northwestern Oregon. 11 10 Layering in gabbro, Ih kilometers south of the Macey Mine along State Route 86. 14 11 Rhodonized gabbro, 2 kilometers south of the Macey Mine along State Route 86. 14 12 Photomicrograph of aligned plagioclase grains, layered gabbro, crossed Nicols. 16 13 Photomicrograph of hornblende crystal with pyroxene cores, hornblende gabbro, crossed Nicols. 16 14 Weakly foliated quartz hornblende diorite, 40 meters west of J. N. Bishop Spring, scale is 15 cm. 17 15 Irregular grain size in diorite, middle Goose Creek, scale is 6 inches. 17 16 Pegmatitic biotite quartz plagioclase pod, 100 meters east of J. N. Bishop Spring, scale is 15 cm. 18 17 Photomicrograph of oscillitory zoning in plagioclase (red) and interstitial orthoclase (yellow), tonalite stained chip, reflected light. 19 fl3.ure Page 18 Photomicrograph of chlorite replacing hornblende, quartz hornblende diorite, plane polarized light. 18 19 Photomicrograph of porphyritic albite granite, crossed Nicols. 23 20 Photomicrograph of granophyric texture, albite granite, crossed Nicols. 23 21 Photomicrograph of porphyritic albite granite, quartz intergrowths in margins of albite pheno- cryst, embayed quartz phenocryst, crossed Nicols. 24 22 Photomicrograph of zoned plagioclase (An«^20- An5) with orthoclase overgrowth, oligoclase albite granite, crossed Nicols. 24 23 Photomicrograph of mortar texture in albite granite, crossed Nicols. 25 24 Photomicrograph of sheared quartz hornblende diorite with sutured quartz grains, same field as Fig. 25, crossed Nicols. 25 25 Photomicrograph of sheared quartz hornblende diorite with sutured quartz grains, same field as Fig. 24, plane polarized light. 26 26 Photomicrograph of stain twinning in plagioclase, crossed Nicols. 26 27 Photomicrograph of sheared "augen" of quartz and a quartz albite glomerblast, crossed Nicols. 28 28 Photomicrograph of extremely fine-grained quartz albite intergrowths, albite granite, crossed Nicols. 28 29 Photomicrograph of fine-grained quartz albite intergrowths, albite granite, crossed Nicols. 29 30 Photomicrograph of medium-grained quartz albite intergrowths (granophyric textures), albite granite, crossed Nicols. 29 31 Photomicrograph of medium-grained granophyric texture with interstitial orthoclase (yellow), orthoclase albite granite, stained chip, reflected light. 30 Fiqu Page 32 Photomicrograph of poikill tic quartz, albite granite, plane polarized light. 32 33 Photomicrograph of zoned amygdule filled with chlorite (core), albite and quartz (rim), spilite, plane polarized light. 32 34 Photomicrograph of clear albite rimming a weakly zoned albite phenocryst, cal cite filled amygdule, spilite, crossed Nicols. 34 35 Photomicrograph of a stained, embayed quartz phenocryst, quartz keratophyre, crossed Nicols. 34 36 Photomicrograph of twinned albite and quartz phenocrysts, quartz keratophyre, crossed Nicols. 36 37 Photomicrograph of quartz in veinlets and fine ­ grained rims on albite phenocrysts, quartz keratophyre, same field as Fig. 38, crossed Nicols. 36 38 Photomicrograph of quartz in veinlets and fine ­ grained rims on albite phenocrysts, quartz keratophyre, same field as Fig. 37, plane polarized light. 37 39 Small silicic dike, west side of Goose Creek near Sucker Creek, scale is 15 cm. 37 40 Diorite porphyry dike crosscutting silicic dike, west side of Goose Creek near Sucker Creek, hammer handle is 1 m. 38 41 Photomicrograph of zoned hornblende phenocrysts, diorite porphyry, plane polarized light. 39 42 Frequency histogram, weight % SiO-, Sparta igneous rocks. ^ 42 43 Weight % Si02 vs. weight % K^O (log scale) plot of Sparta igneous rocks. ^ 43 44 Weight % KpO vs. weight % CaO plot of Sparta igneous rocks. 44 45 Weight % Si Op vs. FeoVMgO plot of Sparta igneous rocks. 45 46 AFM ternary diagram showing distribution of Sparta igneous rocks. 46 Weight % Na^O vs. FeoVwgO plot of Sparta igneous rocKS. Ca-Na-K atomic ratio ternary diagram showing distribution of Sparta Igneous rocks. Weight % K^O vs. Weight % CaO