/ Zeolites and Associated Authigenic Silicate Minerals in Tuffaceous Rocks of the Big Sandy· Formation, Mohave County, Arizona By RICHARD A. SHEPPARD and ARTHUR J. GUDE 3d GEOLOGICAL SURVEY PROFESSIONAL PAPER 830 Physical properties, chemistry, and origin of silicate minerals formed in tuffaceous rocks of a Pliocene lacustrine deposit I~ UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1973 UNITED STATES DEPARTMENT OF THE INTERIOR -;f.r ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director Library of Congress catalog-card No. 73-600206 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.05 (paper cover) Stock Number 2401-02404 CONTENTS Page Page Abstract _______________ ---- ~----------- Authigenic minerals- Continued Introduction ____________________________ _ Phillipsite _______________ ---__ - ____ -- 18 Location _ __ _ __ __ _ _____ __ ___ ___ ___ ___ I Potassium feldspar _____________________ _ 19 Previous work _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Quartz _______________ - _ ---__ ------ - 21 Scope of investigation--------------------- 2 Diagenetic facies _________________________ _ 21 Laboratory methods _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 Distribution _________________________ _ 21 Acknowledgments _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 Field description _______________________ _ 21 Geologic setting _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 Petrography _________________________ _ 23 Stratigraphy and lithology of the Big Sandy Formation _ _ _ _ 4 Nonanalcimic zeolite facies ______________ _ 23 Conglomerate, sandstone, and siltstone _ _ _ _ _ _ _ _ _ _ _ 4 Analcime facies _· ____________________ _ 31 Mudstone _ _ __ __ __ __ ____ ___ ___ ______ _ 6 Potassium feldspar facies _______________ _ 31 Limestone _______________ --------____ 6 Genesis of authigenic silicate minerals _____________ _ 32 Tuff_______________________________ 8 Interpretation of a saline, alkaline depositional Authigenic minerals _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 8 environment for parts of the Big Sandy Formation __ _ 33 Analcime____________________________ 8 Correlation between the water chemistry of the Chabazite ______________ ...! _ _ _ _ _ _ _ _ _ _ _ _ 10 depositional environment and the authigenic silicate Clay minerals ---------·---------------- 12 'mineralogy ..... _________ ---------------- 33 Clinoptilolite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 13 Formation of zeolites from silicic glass __________ _ 33 Erionite _ ___ __ __ __ ___ ___ ___ ___ ___ ____ 15 Reaction of alkalic, silicic zeolites to form analcime ___ _ 34 Harmotome -------------------------- 16 Reaction of zeolites to form potassium feldspar _____ _ 35 Mordenite --------------------------- 17 References cited ______________ ---___ - ----- 35 Opal __ __ __ __ _ __ __ ____ __ __ ___ ___ ___ 17 ILLUSTRATIONS Page FIGURE I. Index map showing the distribution of the Big Sandy Formation _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 2. Diagrammatic sketch showing X-ray diffractometer patterns of authigenic silicate minerals _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 3 3. Map of the Big Sandy Formation, showing sample localities -------------------------------- 5 4. Generalized columnar section of the Big Sandy Formation __________ ..:_______________________ 6 5-8. Photomicrographs of analcime, showing: 5. Thin section of analcimic tuff and individual crystals and clusters of crystals _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 9 6. Pseudomorphs after prismatic clinoptilolite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ I 0 7. Pseudomorphs of shards _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 10 8. Irregular patches _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ t'l 9. Histogram showing the distribution of Si: AI ratios of analcime in tuff _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ II 10. Scanning electron micrograph of chabazite-rich tuff, showing rhombohedral morphology of the chabazite _ _ _ _ _ _ _ 12 II -18. Ph9tomicrographs: II. Veinlet of prismatic clinoptilolite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 14 12. Cavity lined with phillipsite and clinoptilolite ----------------------------------- 14 13. Sandstone cemented by finely crystalline clinoptilolite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 15 14. Prismatic erionite --------------------------------------------------- 16 15. Fibrous erionite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 16 16. Radial aggregates of harmotome _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 17 17. Stubby prismatic crystals of phillipsite --------------------------------------- 18 18. Spherulitic phillipsite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 19 19. Stereographic pair of electron micrographs of potassium feldspar __________ -:-___________________ 20 20. Plot of the band c dimensions of potassium feldspar ------------------------------------ 22 21. Photomicrograph of spherulitic quartz _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 23 22. Map showing the diagenetic facies for a composite of all the tuffaceous rocks in the Big Sandy Formation _ _ _ _ _ _ 24 23. Map showing the diagenetic facies for the lower marker tuff of the Big Sandy Formation ___ .:... _ _ _ _ _ _ _ _ _ _ _ _ 25 24-27. Photographs: 24. Natural. exposure of nonanalcimic zeolitic tuff that consists of erionite and clinoptilolite and minor amounts of chabazite_____________________________________________________ 30 Ill IV CONTENTS l r. Page FIGURES 24-27. Photographs - Continued 25. Natural exposure of chabazite-rich tuff _______________________ - ___ ----------- 30 "· 26. Natural exposure of erionite-rich upper marker tuff _____ -,- _________________ ------- 30 27. Natural ezposure of analcime-rich lower marker tuff __________________________ ---- 30 28-29. Photomicrographs of nonanalcimic zeolitic tuff, showing preservation of vitroclastic texture _______ ---- 31 30. Photomicrograph of nonanalcimic zeolitic tuff, showing pseudomorphs of shards -------------------- 32 -~ TABLES Page TABLE I. Mineralogic composition of mudstone, as estimated from X-ray diffractometer patterns of bulk samples ______ ---- -· 7 ~-.r 2. Semiquantitative spectrographic analyses of mudstone ______________________ --____ ---------- 7 3. Formulas of selected alkalic zeolites __________________________________ ---_---------- 8 4. Checklist of associated authigenic silicate minerals in tuffs of the Big Sandy Formation ___________________ _ 9 5. Chemical analysis and composition of unit cell of analcime ______________________________ ----- II 6. Chemical analysis and composition of unit cell of chabazite ________________________________ -- - 12 7. Semiquantitative spectrographic analyses of chabazite-rich and clinoptilolite-rich tuffs ____________________ _ 13 8. Chemical analysis and composition of unit cell of clinoptilolite _______________________________ --- 15 9. Chemical analysis and composition of unit cell of erionite _________________________________ --- 17 c 10. Chemical analysis and composition of unit cell ofharmotome _________________________ --------- 18 II. Chemical analysis and composition of unit cell of phillipsite _____________________________ ------ 19 12. Semiquantitative spectrographic analyses of potassium feldspar-rich tuffs __________________ ---------- 20 13. Unit-cell parameters and boron content of authigenic potassium feldspar ___________ ----------------- 21 14. Mineralogic composition of tuffaceous rocks of the Big Sandy Formation, as estimated from X-ray diffractometer patterns of bulk sa1nples ______________________ ---------------------------:-------- 26 \ ZEOLITES AND ASSOCIATED AUTHIGENIC SILICATE MINERALS . IN TUFFACEOUS ROCKS OF THE BIG SANDY FORMATION, MOHAVE COUNTY, ARIZONA By RICHARD A. SHEPPARD and ARTHUR J. GuDE 3D ABSTRACT creasing salinity and alkalinity. The lake water was probably moderately to The Big Sandy Formation of Pliocene age covers an area of about 30 highly saline with a pH of 9 or higher, except near the lake margin.