U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1378 Deformation of the Josephine Peridotite, California and Oregon By JAMES G. EVANS U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 137 UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987 DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Evans, James George, 1938- Deformation of the Josephine Peridotite, California and Oregon. (U.S. Geological Survey Professional Paper 1378) Bibliography: p. 44-45 Supt. of Docs. No.: I 19.16:1378 1. Rock deformation Klamath Mountains (Calif, and Oreg.). 2. Geology, stratigraphic Mesozoic. 3. Peridotite Klamath Mountains (Calif, and Oreg.). 4. Geology Klamath Mountains (Calif, and Oreg.). I. Title. II. Series: United States. Geological Survey. Professional Paper 1378. QE604.E88 1986 551.8'09794'21 87-600231 For sale by the Books and Open-File Reports Section, U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 CONTENTS Page Abstract __________________________________ 1 Structural analysis Continued Introduction ______________________________ 2 Mesoscopic fabric Continued Geologic setting__________________ __________ 2 Fabric of the Vulcan Peak area __ ____________ 32 Josephine Peridotite_________________________ 5 Petrofabric studies ___________________________ 33 Structural analysis __________________________ 7 Introduction ____________________________ 33 Introduction ___________________________ 7 Description of microfabrics ____________________ 33 Descriptions of minor structures _____ __________ 9 Sample Jl ___________________________ 33 Layers and foliations __________ __________ 9 Sample J2 ___________________________ 34 Folds _____ _____ ________________. 11 Sample J3 ___________________________ 35 Rods ______________________________ 13 Sample J4 ___________________________ 36 Mineral lineations_____________________ 14 Sample J5 ___________________________ 37 Dikes _____________________________ 14 Sample J6 ___________________________ 37 Summary ___________________________ 15 Sample J7 ___________________________ 38 Mesoscopic fabric ________________________ 16 Sample J8 ___________________________ 39 Area I: Low Plateau Mountain _______________ 16 Discussion of olivine fabrics ___________________ 40 Area II: High Plateau Mountain ____________ 18 Summary ___________ ________ _____________ 42 Area III: Stony Creek ____________________ 22 Origin _______________________________ 42 Area IV: Chrome No. 1 ___________________ 22 Deformation 1 _________________________ 42 Area V: Elk Camp Ridge__________________ 22 Deformation 2 ______________ ____________ 42 Area VI: Elk Camp _____________________ 23 Deformation 3 ___________________________ 42 Area VII: Low Divide ____________________ 23 Deformation 4 _______ ______ ________ _ __ 43 Area VIII: High Divide ______________________ 26 Deformation 5 ______________________ ____ 43 Area IX: Pine Flat Mountain ________________ 27 Deformation 6 ______________________ ____ 43 Area X: Cleopatra's Lookout _______________ 27 Deformation 7 __________________ ________ 43 Area XI: Biscuit Hill ___________________ 28 Deformations 8 and 9 ______________________ 43 Area XII: Buckskin Peak __________________ 28 Age of crystalline deformations _________________ 43 Area XIII: Red Mountain __________________ 30 Limitations of this study _____________________ 43 Summary ____________________________ 31 References cited ____________ ________________ 44 ILLUSTRATIONS Page FIGURE 1. Index map of northern California and southern Oregon, showing location of study area ____________________ 3 2. Geologic sketch map of study area, showing internal macroscopic structures of the Josephine Peridotite _____ ___ ___ 4 3-5. Photographs of: 3. Chromitiferous dunite showing ehromite-net and occluded-silicate textures _______________________ 6 4. View northward from Red Mountain toward Rattlesnake Mountain ______________________________ 7 5. Orthopyroxenite layers and dunite layers in harzburgite __________________________________ 9 6. Sketches illustrating layers in harzburgite exhibiting pullapart structure ___________________________ 10 7-9. Photographs of: 7. Chromite foliation in dunite at high angle to dunite-harzburgite contact _________________________ 10 8. Deformed chromite-net texture in dunite __________________________________________ 11 9. Flattened rods of ehromite in dunite at an angle to dunite-harzburgite contact _____________________ 11 10-12. Sketches illustrating: 10. Isoclinal folds in peridotite ___ ________ _____ _ _ _____ _____ _______________ ______ 11 11. Refolded early isoclinal folds in peridotite ___ _ ____ _ ___ __ __ _ ____________________ ___ __ 12 12. Open folds in peridotite __________________________________________________________ 12 13-19. Photographs of: 13. Chromite in dunite _________________________________________________________ 13 14. Irregular dunite body in harzburgite ___ __ ______________ _____ _____ _________________ 14 15. Dunite dike in harzburgite ___________________________________________________ 14 16. Intersecting dunite dikes in harzburgite _____________________________________________ 15 17. Warped orthopyroxenite dike ___________________________________________________ 15 18. Faulted orthopyroxenite dike ___________________________________________________ 15 19. Composite dunite-orthopyroxenite dike in harzburgite __ _ ___ _____ ______________ _ ___ _ _____ 16 20. Fabric diagrams for area I _____________________________________________________ 16 21. Fabric diagrams for subarea Ila ____________________________________________________ 19 in IV CONTENTS FIGURE 22. Photograph of multiply folded peridotite ___ _______________________________________________ 20 23. Photograph of multiply folded peridotite viewed along late-fold hinge ________________________________ 20 24-29. Fabric diagrams for: 24. Subareallb -____________________________-___________________________________ 21 25. Subarea lie _____________________________________________________________________ 22 26. Area III______________________________________________________________________ 22 27. Area IV ___________________________________________________________________ 23 28. Area V____________________________________________________________________ 23 29. AreaVI__________________________________________________________________________ 24 30. Photograph of harzburgite pod in dunite ____________________________________________________ 24 31 37. Fabric diagrams for: 31. AreaVII ____________________________________________________________________________________________________ 25 32. Area VIII _________________________________________________________________________________________________ 26 33. Area IX________________________________________________________________________ 27 34. AreaX _____________________________________________________________________________________________________ 27 35. Area XI __________________________________________________________________________________________________ 28 36. Area XII ___________________________________________________________________________________________________ 29 37. Area XIII _____________________________________________________________________ 31 38. Diagram of poles to mean attitudes of subpopulations of layering and foliations in areas I, II, and V through XIII _______ 32 39. Synoptic diagram of linear elements in areas I through XIII __________________________________________ 32 40. Photomicrograph of thin section of sample Jl, a harzburgite __________________________________________ 33 41. Olivine-fabric diagrams for sample Jl __________________________________________________ 34 42. Photomicrograph of thin section of sample J2, a dunite _________________________________________ 34 43. Olivine-fabric diagrams for sample J2 _______________________________________________ 35 44. Photomicrograph of thin section of sample J3, a dunite _______________ ___________________________ 35 45. Olivine-fabric diagrams for sample J3 _______________________________-_______________________ 35 46. Photomicrograph of thin section of sample J4, a dunite ____________________________________ 36 47. Olivine-fabric diagrams for sample J4 _________________________________________________ 36 48. Photomicrograph of thin section of sample J5, a dunite ______________________________________________ 37 49. Olivine-fabric diagrams for sample J5 ____________________________________________________ 37 50. Photomicrograph of thin section of sample J6, a dunite _____ _______________________________________ 38 51. Olivine-fabric diagrams for sample J6 _________________________________________________ 38 52. Photomicrograph of thin section of sample J7, a dunite ________________________________________ 38 53. Olivine-fabric diagrams for sample J7 ______________________________________________________ 39 54. Photomicrograph of thin section of sample J8, a wehrlite ______________________________________ 39 55. Diopside-fabric diagrams for sample J8 ___________________________________________________ 39 56. Synoptic diagram of Z maxima for samples Jl through J7 _____________________________________41 TABLE Page TABLE 1. Summary of structures, and the orientations and ages of structures, for deformations affecting the Josephine Peridotite _ 8 DEFORMATION OF THE JOSEPHINE PERIDOTITE, CALIFORNIA AND OREGON By JAMES G. EVANS ABSTRACT Other dunite dikes cut early layering and foliation