Geology of the Chewelah-Loon Lake Area, Stevens and Spokane Counties, Washington GEOLOGICAL SURVEY PROFESSIONAL PAPER 806 Prepared in cooperation with the Washington Division of Mines and Geology _J Geology of the Chewelah-Loon Lake Area, Stevens and Spokane Counties, Washington · By FRED K. MILLER and LORIN D. CLARK With a section on POTASSIUM-ARGO:N AGES OF THE PLUTONIC ROCKS By JOAN C. ENGELS G E 0 L 0 G I CAL SURVEY P.R 0 FE S S I 0 N A. L PAPER 8 0 6 Prepared in cooperation with the Washington Division of Mines and Geology UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1975 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY V. E. McKelvey, Director / Library of Congress catalog-card No. 73-600314 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 -Price $2.15 (paper cover) Stock Number 2401-02587 CONTENTS Page Page Abstract ····································································-·················· 1 Paleozoic rocks-Continued Introduction ................................................................................ 1 Carbonate rocks-Continued Location and .accessibility.................................................. -1 -·Devonian -or Mississippian carbonate rocks-Con. Previous work ...................................................................... 2 Unit 2 ............................... -..................................... 30 Present work .................................................. :..................... 3 Unit 3 ................... ·.-......................... :...................... 31 Mississippian carbonate rock. ......:............................. 31 ~~~:~e::::;~ s~W~~~~~~~~~~~~~~~~~~~~~~~~~-~~~~~~~~~~::::::::::::::::::: : Paleozoic carbonate· rocks, undivided...................... 32 Precambrian rocks ......•............................... -............................... 4 Mesozoic plutonic rocks ......................................... ................... _33 Belt Supergroup .................................................................. 4 Flowery ·Trail Granodiorite......................... :.................... 34 Prichard Formation .................................................... 4 Starvation Flat Quartz Monzonite.................................. 38 Ravalli Group ........................................... .................. 6 Phillips Lake· Granodiorite (and associated dikes).... 40 Burke Formation ········"···················· ................... 6 Two-mica quartz monzonite.............................................. 44 Revett Formation ~--·····---~---································· 7 Coarse-grained quartz monzonite.................................... 45 St. Regis Formation.......................................... :. 8 Muscovite quartz monzonite............................................ 46 Wallace Formation .................................................... 9 Cenozoic plutonic rocks.......................................... ~................... 47 Missoula Group .......................................................... 11 Silver Point Quartz Monzonite........................................ 47 Striped Peak Formation .................................... 11 Granodiorite ........................................ ................................ 50 Membera ...................................................... 12 Fine-grained quartz monzonite ........................................ 50 Memberb ...................................................... 12 Differentiation of the plutonic rocks............................ ~........... 51 Member c ...................................................... 13 Potassium-argon ages of the plutonic rocks, by Joan C. Memberd ...................................................... 16 Engels.................................................................................... 52 Deer Trail Group ...........-..................................................... 16 Togo(?) Formation ........................................... :........ 17 Cenozoic hypabyssal, volcanic, and sedimentary rocks......... 58 Edna Dolomite ....... .,................................. ................... 17 Mafic dikes .......................................................................... 58 McHale Slate ........................................... ................... 17 Andesite ................................................................................ 60 Stensgar Dolomite ...................................................... 17 Basalt.................................................................................... 60 Buffalo Hump(?) Formation ........ ,........................... 18 Latah Formation ........ ~....................................................... 61 Deer Trail Group, undivided.................................... 18 Conglomerate ...................................................................... 61 Relation between the Belt Supergroup and the Glacial, alluvial, and talus deposits, undifferentiated.... 61 Deer Trail Group............................................................ 18 Structure ...................................................................................... 62 Metamorphic rocks, undivided ........................................ 24 Structures in the Belt Supergroup block........................ 62 Windermere Group ......................................... ................... 24 Folds .............................................................................. 62 Huckleberry Formation ............................................ 24 Faults ............................................................................ 64 Monk Form_ation ..................................... ................... 26 Structures in the Deer Trail Group biock. ................... 65 Paleozoic rocks ............................................................................ 27 Other differences between the two blocks........................ 66 Addy Quartzite ................................... -............ ................... 27 .Structure separating the two blocks................................ 67 Carbonate rocks .................................................................. 29 Other faults .......................................................................... 69 Metaline Formation ............................... ................... 29 Mineral deposits ..................................................... ................... 69 Devonian or Mississippian .carbonate rock............ 30 References. cited .......................................................................... 71 Unit 1 .................................................................... 30 Index .................................................................................-............. 73 ILLUSTRATIONS Page PLATE 1. Geologic map of the north half of the Chewelah-Loon ·Lake-area, Stevens and Spokane Counties, Washington ............................................................................................................................................................... In pocket 2. Geologic map .of. the .south .half.of.the.. Chewelah-.Loon.. Lake area,.Stevens-and Spokane Counties, Washington .............................................................................................................................................. , ................. In pocket FIGURE 1. Index map showing location of Chewelah-Loon Lake area .............................................................................................. 2 2. Map showing location of some geographic features referred to in the text.. ....... :....... -..................................................... 3 3. Generalized columnar section of the Prichard Formation .................................... :............................................................. 5 4 ..- Generalized, columnar.. section of .member. c of, -the· Striped Peak -Formation ·on Quartzite ·Mountain...................... 14 III IV CONTENTS _ Page FIGURE 5. Photograph showing argillite and breccia from member c of the Striped Peak Formation.......................................... 14 6. Photograph showing soft-sediment breccia in the McHale Slate, probable correlative of member c of the Striped Peak Formation .................................................................................................................................................... 15 7. Columnar sections showing possible correlations between the Deer Trail Group and the Belt Supergroup............ 21 8. Generalized geologic map showing the distribution of the Belt Supergroup and Deer Trail Group in and around the Chewelah-Loon Lake area···············-··········································································································· 22 9. Photograph showing the bold cliffs (dip slopes) of Addy Quartzite which form the west side of Quartzite Mountain ............................................................................................................................................................................. 27 10. Photograph showing the contact between the Addy Quartzite and member d of the Striped Peak Formation.......... 27 11. Ternary plots of modes of plutonic rocks ................... _........................................................................................................... 34 12-15. Photographs showing: 12. Fine-grained dike-fomi mass of graphically intergrown rock that intrudes