UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY
Preliminary geologic map of the Colville Indian Reservation, Ferry and Okanogan Counties, Washington
Compiled by
Brian F. Atwater and C. Dean Rinehart 1
With a table of potassium-argon ages compiled by
Robert J. Fleck1
Open-File Report 84-389 (this pamphlet accompanies 4 oversize sheets)
Prepared in cooperation with the Bureau of Indian Affairs
This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards and stratigraphic nomenclature.
1Menlo Park, California
1984 Contents
Introduction 1 Portrayal of geologic age on plate 4 1 Acknowledgement s 2 Description of map units 2 Surficial materials (units 1 and 2) 2 Younger plutonic rocks and related hypabyssal and volcanic rocks 3 Extrusive rocks (units 3 and 4) 3 Hypabyssal intrusive rocks (units 5 and 6) 3 Plutonic rocks (units 7-17) 4 Brecciated rocks (units 18 and 19) 5 Characteristically mylonitic rocks of the gneiss domes (units 20-24) 6 Older plutonic rocks 7 Hornblende-free rocks (units 25-36) 7 Hornblende-bearing rocks (units 37-46) 9 Mixed rocks (units 47-50) 10 Non-mylonitic metamorphosed rocks sedimentary and mafic igneous (units 51-58) 11 References 15 Conventional symbols 16 Additional symbols 19
Tables Table 1. Potassium-argon ages from volcanic and intrusive rocks of the Colville Indian Reservation 13
Illustrations Figure 1. 15-minute and 30- by 60-minute quadrangles in the Colville Indian Reservation ii 2. Sources of geologic mapping iii 3. Large-scale geologic map of type area for the hypabyssal intrusive suite of Cody Lake, by Grace McCarley and R. Wade Holder iv 120' AS' 30' 15' 119° 45' 30' 15' 118! 30
o N E S P E L E 15'
8°
COULEE DAM
Figure 1. 15-minute and 30- by 60-minute quadrangles in the Colville Indian Reservation.
ii 1. Campbell, A. B. 1963-64(7)
2. Campbell, A. 8., and Raup, 0. B. (1964)
3. Fox, K. F., Jr. 1980-83; Becraft, G. E. 1964-73
4. Becraft, G. E. (1966); Goodge, J. W. 1983
5. Rinehart, C. D. a, 1980-81; b, and N. Wilson 1982; c, and M. Gaona 1983; d, and J. Deen 1983
6. Holder, R. W. a, 1980; and G. McCarley 1982; b, and G. McCarley 1983
7. Moye, F. J. and E. King 1980; and D. Jennings 1981
8. Atwater, B. F. a, and E. King 1980; and M. McGroder 1981; b & c, and N. Wilson 1982; d, and J. Deen 1983
9. Staatz, M. H. (1964)
10. Carlson, D. H. a, 1981; and L. Peters 1982; b, and C. Closson 1983
11. Singer, S. H. a, and V. Lueth 1982; b, and M. Gaona 1983
12. Goodge, J. W., and Hansen, V. L. 1983
13. Hansen, V. L. 1982
14. Goodge, J. W. 1982
15. a, Utterback, W. C., 1979-1980; b, Cochran, D. S., and Warlow, J. C. (1980) Figure 2.---Sources of geologic mapping. Numbers 2, 4, 9, and 15b: published maps cited in reference list; date is that of publication. Others: unpublished mapping; dates indicate field work. iii R. Warfe Holder,J I98Z.
Uer-itklencfe - bear'm* p»r^livr> (3 »n«.ppa.b/e van'cf-res^ HypabyssaI i n + r u s i ve 5 of Lake Horn L 'to^C -f rtt porohyrv I
Figure 3. "Large-scale geologic ioap of type area for hypabyssal intrusive suite of Cody Lake, by Grace McCarley and R. Wade Holder. Country rock (the granite of Daisy Trail) is riddled by the Cody Butte. Seventeenmile Mountain quadrangle, about 1 mi south of Twentythree Mile Creek.
iv INTRODUCTION of aplite, alaskite, and pegmatite. "Miles" rather than "kilometers" are used as standard units of The accompanying map presents a generalized view distance because the land net is based on miles. of the bedrock geology of the Colville Indian We use "gneiss dome" as a purely descriptive term Reservation, northeastern Washington. The for structures defined by mylonitic rock that grades Reservation, covering about 2,175 «i in Okanogan and downward into non-mylonitic gneiss and granite. The Ferry Counties, is bounded on the south and east by term was applied to our study area by Fox, Rinehart, the Columbia River, on the west by the Okanogan River, Engels, and Stern (1976); some geologists prefer and on the north by a line near latitude 48*30'. "metamorphic core complex" (Coney, 1980, p. 10, 25-26) Plutonic rocks predominate but metamorphic, or simply "dome" (Cheney, 1980). One of the gneiss hypabyssal-intrusive, and volcanic rocks also cover domes (Lincoln gneiss dome) has not been recognized large areas. J. T. Pardee (1918), during a two-summer previously. All of the gneiss domes in the map area reconnaissance, sketched the distribution of eight of are highly asymmetric: the boundary between mylonite the principal rock types on a primitive 1:250,000- and carapace, shown on the map as a low-angle fault, scale bese. Subsequent geologic and topographic is exposed only on the west side of the western mapping at scales of . 1:62,500 and larger allows (Okanogan) gneiss dome and only on the east side of delineation of the 72 bedrock units whose distribution each of the eastern (Kettle and Lincoln) gneiss and distinguishing character are the subjects of this domes. These three gneiss domes together may open-file report. represent but a single gneiss dome, bisected by the Nearly all of the bedrock mapping on the Republic and Keller grabens. reservation since Pardee's reconnaissance, has been done during the pest 25 years (figs. 1, 2). During PORTRAYAL OF GEOLOGIC AGE ON PLATE 4 the 1950's and I960 1 a, U.S. Geological Survey work in the eastern half of the reservation yielded three Plate 4 shows the known or inferred age of each published 15-minute quadrangles Bald Knob (Staatz, map unit relative to other units and relative to 1964), Hunters (Campbell and Raup, 1964), and Wilmont several divisions of geologic time. A solid-line box Creek (Becraft, 1966) and unpublished mapping of shows the age of lithologic features that characterize parts of the Inchelium quadrangle (by Arthur B. the unit; a dashed-line box shows age of the protolith Campbell), and Twin Lakes quadrangle (by George E. (p) of rock that characteristically has been reconsti Becraft). To the west, Newcomb (1937) mapped part of tuted (r) by metamorphism, brecciation, or hydro- the Disautel quadrangle; Snook's (1965) 1:137,000- thermal alteration. Lengths of boxes indicate scale map includes part of the Omak Lake quadrangle; allowable age range; the actual age range may be L. G. Fritz (1978) made a reconnaissance of the less. Box length is not necessarily proportional to Okanogan and Bridgeport quadrangles at a scale of absolute time. 1:62,500; and large-scale maps by Broch (1979) and Numbered triangles and diamonds within a unit box Orazulike (1982) cover parts of the Alameda Flat identify units with which the boxed unit has one or quadrangle. Interest in molybdenum deposits led to more exposed contacts. A triangle pointing up mining-company mapping during the 1970's in the indicates that the unit intrudes the boxed unit; a vicinity of Mount Tolman, near Keller. Some of the triangle pointing down Indicates that the unit is Mount Tolman mapping is presented at a scale of intruded by the boxed unit; diamonds indicate 1:6,000 by Cochran and Warlow (1980), and much of the equivocal age relations. Contact relations between rest is summarized in an unpublished, 1:24,000-scale pre-Tertiary units 53-58 and younger rocks, are compilation that was begun by S. A. Mellon and omitted for convenience. completed in 1980 by William C. Utterbeck. A nearby Potassium-argon ages (for example, 49.4 ± 0.3 molybdenum deposit in the Wilbur quadrangle was mapped (b)) are given only for samples from the map area. by R. 0. White (1981). The most recent work, which Minerals dated are (b) biotite, (h) hornblende, (m) has led to the present map, was carried out during the muscovite, K (K-feldspar), and (s) sericite. period 1980-1983 by the Geological Survey at scales of Analytical data are presented in table 1; samples are 1:24,000 and 1:62,500. In addition to Atwater and located by coordinates in that table and by circled Rinehart, persons primarily responsible for that dots on the map itself (plates 1-3). mapping are Diane H. Carlson, Kenneth F. Fox, Jr., Vertical positions of many unit boxes in plate 4 John W. Goodge, Vicki L. Hansen, R. Wade Holder, James depend at least partly on one or more of three P. Minard, Falma J. Moye, and Stephen H. Singer. presumptive datums: (1) Solidification of the The present map was compiled on newly prepared hornblende-bearing granitoid rocks of Swimptkin Creek Geological Survey l:100,000-scale base maps by and the diorite of Devils Elbow. Both of these units manually transferring the geology from clear-film yield nearly concordant hornblende and biotite K/Ar photographic reductions made from the larger-scale ages near 49 m.y. (2) Solidification of the maps. Only minor generalization of the geology was porphyritic granite of Coyote Creek, the porphyritic necessary, mainly for clarity in cluttered areas, and granite of Keller Butte, and the relatively old parts for continuity where compilers prerogative made of the granite of Daisy Trail. These rocks appear to merging of some units seem appropriate, or neces be approximately coeval because of similarities in sitated contact adjustment at quadrangle boundaries. lithology (all are hornblende-free, light-colored, Atwater is primarily responsible for generalization, porphyritic, medium-grained granite) and relative age and also for compiling descriptions of map units, in (all are probably intermediate between the porphyritic the Nespelem and Coulee Dam 1:100,000 quadrangles; granodiorite of Manila Creek and the hypabyssal Rinehart is primarily responsible for these things in porphyry of Cody Lake). The discrepancy in biotite the Omak 1:100,000 quadrangle. K/Ar ages between the Keller Butte (about 60 m.y.) and Five of the map units were previously given the Coyote Creek and Daisy Trail (both about 50 m.y.) formal names Columbia River Basalt Group, Sanpoil can be explained by differences in history of cooling Volcanics, O'Brien Creek Formation, Tonasket Gneiss, after solidification (compare Fox and others, 1977, p. and Covada Group but no new formal names are proposed 12-13). (3) Mylonitic deformation associated with herein. Plutonic nomenclature follows that recom formation of the gneiss domes. We presume that the mended by Streckeisen (1973). Minerals modifying a Okanogan, Kettle, and Lincoln gneiss domes underwent rock name (for example, biotite-hornblende diorite) mylonitization at about the same time, there being no are listed in order of increasing abundance; minerals evidence to the contrary. We further presume that shown in parentheses for example, (muscovite)-biotite this mylonitization is mostly older than datum (1) and granite are present only locally. CI denotes color entirely younger than datum (2). The Swimptkin Creek index. The term "aplo-pegmatite" denotes assemblages and Devils Elbow [datum (1)] cut and(or) contain inclusions of penetratively mylonltized rock and are OF MAP WITS themselves scarcely mylonitic. By contrast, gneiss- dome mylonlte cuts, but is not cut by, the porphyritlc SURFICIAL MATERIALS granite of Coyote Creek and relatively old parts of the granite of Daisy Trail [datum (2)]. Possibly the Sediment and basalt are thinner than 100 m in most Coyote Creek solidified late in the period of gneiss- areas dome mylonitizatlon (Fox and others, 1976, p. 1221); mylonitic foliation and lineation of the Okanogan UNCONSOLIDATED DEPOSITS (Quaternary) Glacial, gneiss dome die out within the Coyote Creek, south 1 alluvial, lacustrine, eolian, and landslide eastward along the strike of the gneiss-dome border. deposits conservatively shown as covering But this change apparently begins northwest of the about one quarter of the reservation. The Coyote Creek, in the plutonic complex of Boot glacial deposits are primarily till, the Mountain, whose non-nylon! tic parts are largely or known southern limit of which largely wholly pre-Tertiary and probably predate the gneiss defines the terminal ice margin shown on dome. Plate 4 therefore incorporates the view that the map. Erratic boulders known beyond the the mylonitic border of the Okanogan gneiss dome loses inferred ice margin lie no higher than definition southeastward without truncation by the altitude 760 m, to which they could have porphyritic granite of Coyote Creek. been rafted by bargs (Atwater, 1983, p. Dotted lines in Plate 4 group map units that are 11). Age of most exposed till probably mylonitic at least locally within the indicated gneiss late Wisconsin; till dating from any dome. These lines extend below the presumed age-range earlier glaciation has yet to be reported of mylonitic deformation in order to enclose the from the reservation. The alluvial Coyote Creek and the Daisy Trail, predominantly deposits consist mainly of terrace-forming non-mylonitic rocks whose boxes in plate 4 show gravel, most of it probably recessional inferred age of solidification rather than inferred outwash, and fan deposits, mostly rehandled age of mylonitization. drift. Lacustrine deposits, mainly well- bedded silt and clay, are particularly ACKNOWLEDGEMENTS abundant in the Columbia River Valley, the lower Sanpoil River Valley (Keller and The success of the USGS mapping project of 1980- Wilbur quadrangles), and in French Valley 1983 owes much to the cooperation and generous support (Omak Lake and Disautel quadrangles). The from the Colville Confederated Tribes* In particular, lake in the Columbia and Sanpoil River the Tribes' Geology Department, headed by Donald A. valleys (glacial Lake Columbia) formed Aubertin, and Including John D. Erickson, Lane E. behind the Okanogan lobe of the Cordilleran Fortin, Janet Hohle, and William C. Utterback, was ice sheet, which blocked the Columbia as most helpful with support of many kinds, from making far upstream as Grand Coulee Dam during the available their office and laboratory facilities, to last glaciation (Flint, 1935). In the sharing their considerable geological knowledge of the Sanpoil River valley, rhythmic interbedding reservation. Especially helpful in sharing his between sandy, normally graded beds and expertise was William C. Utterback who, during the sets of silt-and-clay varves suggests that first two years of USGS mapping, was Chief Geologist floods from another ice-dammed lake for the AMAX Inc. Mount Tolman Project, a joint probably Lake Missoula, Montana venture with the Colville Tribes to explore Mount periodically engulfed Lake Columbia Tolman 1 s molybdenum deposit. (Atwater, 1983). Deposits of saline Others whose help contributed greatly to the post-glacial lakes southwest of Omak success of the Geological Survey mapping in 1980-1983 consist primarily of calcareous silt but include: the Jannot family of Keller, and Norman C. also, at least at White Lake (Omak Lake McClure of Nespelem, who allowed operation of field quadrangle), include coarse vi trie-crystal camps on their lands; the Omak School District, and ash of Glacier Peak layer B or G (unpub. the Bureau of Indian Affairs especially Daniel Len correlation by A. M. Sarna-Wojcicki and for similar permission; and Gary and Dennis Jackson of C. E. Meyer, 1982, based on major-element Nespelem for expert and cheerful vehicle maintenance. chemistry of glass; age about 11,200 C Excellent field assistance in USGS mapping of years according to Mehringer and others, 1980-1983 was provided by Cheryl A. Closson, Justus B. 1984). Eolian sand abounds near the mouth Deen, Michael T. Gaona, Deborah JenningSi Ellen King, of the Okanogan River, along highway 155 Virgil Lueth, Grace McCarley, Michael F. McGroder, 1-2 mi east of Omak (Minard, in press), Lisa Peters, and Nathaniel P. Wilson. Most of the about 1 ml northeast of the mouth of the contacts and faults on plates 1-3 were drafted by Sanpoil River, and farther east at Sand Cheryl A. Closson; the remainder was drafted by Justus Hills. Interbedded with the dune sand near B. Deen, Catherine R. McMasters, Bruce W. Rogers, Omak is fine volcanic ash that probably Jeanette Smith, and Atwater and Rinehart. Rinehart came from Mt. Mazama according to major- drafted plate 4 and Katharine Klock typed the text. element analyses and correlations of A. M. USGS mappers of 1980-1983 gratefully acknowledge Sarna-Wojcicki and C. E. Meyer (unpub. brief but stimulating visits by professors of geology data, 1982; age between 6000 and 7000 14C from several schools in the Northwest: Bill years according to Lemke and others, 1975, Bonn!chsen, Robert W. Jones, and Rolland R. Reid of p. 19-22). Lit ho logically similar ash is the University of Idaho; Peter R. Hooper, Richard L. also interbedded with non-glacial alluvium: Thiessen, and A. John Watkinson of Washington State about 1 mi east of the mouth of Wanacut University; and Donald W. Hyndman of the University of Creek, and in a gravel pit 2.5 mi southwest Montana. of St. Mary's Mission (Omak Lake This report was reviewed in its entirety by Diane Quadrangle); in a bank of Manila Creek H. Carl son and Ray E. Wells, and an early version of 2.5 mi west-northwest of its mouth, and in plate 4 was reviewed by Kenneth F. Fox, Jr. banks of Sclome Creek at Sclome Meadow Additional reviews of parts of the report were (Keller quadrangle); and in at least two supplied by John D. Erickson, John W. Goodge, Vlcki L. places on the north shore of Franklin D. Hansen, R. Wade Holder, Falma J. Moye, Stephen H. Roosevelt Lake 0.5-5.0 mi east of Grand Singer, and William C. Utterback. Coulee Dam. Additionally, an ash suspected to be Mazama is interbedded with landslide deposits at the mouth of Falls Creek divided into: (Wilmont Creek quadrangle). Host landslide deposits on the reservation involve glacio- Tsu Upper unit--Dark-colored rocks, mostly lava lacustrine deposits of the Columbia and flows, with quartz phenocrysts scarce or Sanpoil River valleys, and most of these absent, and hornblende and (or) augite at landslide deposits have formed since least as abundant as biotite. Pyroclastic construction of Grand Coulee Dam (Jones and rocks shown by pattern of ovals, epiclastic others, 1961) rocks by coarse stipple, autoclastic breccia by solid triangles Tb COLUMBIA RIVER BASALT GROUP (Miocene)--Dark- 2 gray aphyric basalt forming extensive Tsl Lower unit Light-colored ±hornblende-quartz- flows. Partly covered by drift and locally biotlte-plagioclase rocks, largely interbedded with sedimentary rocks south pyroclastic and epiclastic. Underlies but west of Omak Lake; partly covered by loess nowhere overlies typical dark, quartz-poor, and perhaps also by Miocene(?) alluvial-fan hornblende-rich Sanpoil Volcanics. Except deposits beside Hellgate Canyon (Wilbur for local presence of hornblende, resembles quadrangle) the O'Brien Creek Formation, which widely underlies Sanpoil Volcanics in northeastern YOUNGER PLUTONIC ROCKS AND RELATED Washington (Pearson and Obradovich, HYPABYSSAL AND VOLCANIC ROCKS 1977). Probably correlates with the Sanpoil Volcanics that apparently rest on This igneous complex, mostly recognized by Pardee the crystalline floor of the southern end (1918), comprises granitoid rocks, some near the of the Republic graben (Nespelem Republic and Keller grabens, others farther west in quadrangle) the Okanogan gneiss dome; hypabyssal intrusive rocks, widely distributed but also concentrated as dike To O'BRIEN CREEK FORMATION (Eocene) Light-colored swarms flanking the grabens; lava flows and tuff, 4 epliclastic and pyroclastic rocks, mostly found primarily in the grabens; and minor brecciated crystal tuff of rhyodacite and quartz rocks. Some of the hornblende-bearing flows, dikes, latite. Exposed at margins of Keller and plutons in the complex are probably comagmatic graben, where up to 900 m thick (between (Pardee, 1918, p. 39). Most of the hornblende-free Bridge and Louie Creeks), and exposed less granitoid rocks that we place in the complex either abundantly at margins of Republic graben. cross-cut the hornblende-bearing plutons or display Includes rhyodacite lava flow and contacts that allow approximate contemporaneity with hypabyssal intrusive equivalents near Brush these plutons. K/Ar ages from the complex cluster Creek in Keller graben. Clasts and near 50 m.y.; probably these ages closely approximate phenocrysts dominantly plagioclase, quartz, ages of primary cooling because there is little age and biotite; hornblende absent. Age about discordance between biotite-hornblende pairs from the 54 m.y. according to a single K/Ar date complex and because no Intrusive rock in the map area from the Pend Oreille River area 45 mi east is known to be much younger than 50 m.y. of the reservation (Pearson and Obradovich, 1977, p. 13) Extrusive rocks Hypabyssal intrusive rocks Ts SANPOIL VOLCANICS (Eocene) Phyric lava flows, 3 subordinate pyroclastic and epiclastic INTRUSIVE RHYOLITE NEAR WEST FORK (Eocene) rocks, and minor hypabyssal intrusive 5 Forms light-colored dikes and plugs rocks; mostly dacite and rhyodacite. intruding upper unit of Sanpoil Volcanics Abundant in Republic and Keller grabens; in eastern pert of Republic graben (Seven also present near mouths of Monaghan and teenmile Mountain quadrangle). Sole Nez Perce Creeks (Wilmont Creek and Hunters phenocryst is fine-grained biotite, set in quadrangles) at north end of a NNE-trending a glassy groundmass or in a devitrified volcanic belt about 50 km long (Pearson and groundmass of quartz and feldspar. These Obradovich, 1977, p. 19), and opposite are the only hornblende-free rocks known to mouth of Spokane River (Lincoln intrude Sanpoil Volcanics in the map quadrangle), where previously unrecog area. Probably youngest hypabyssal nized. Dominant phenocrysts plagio-clase intrusions in the map area, and possibly plus two or three mafic minerals, one of comagmatic with the granite of Deadhorse these biotite and the other(s) hornblende Creek and with aplite dikes (not shown on and(or) augite; phenocrysts of quartz map) cutting the Intrusive suite of Cody typically scarce. Groundmass mostly stony, Lake. K/Ar age about 50 m.y. (table 1) locally glassy. Age: 48-50 million years according to K/Ar dates on two lava flows Th HYPABYSSAL INTRUSIVE SUITE OF CODY LAKE in reservation (table 1); greater than 49- 6 (Eocene) Porphyritic rocks of intermediate 50 million years according to K/Ar dates on and acidic composition forming dikes and three Intrusions into Sanpoil Volcanics in other small or narrow intrusions. Most reservation (table 1); and 51-52 million voluminous as swarms of narrow intrusions years according to K/Ar ages on biotite and flanking Republic and Keller grabens and hornblende from 5 lava flows in Sanpoil extending south of these grabens. Shading Volcanics elsewhere in northeastern denotes areas where the ratio of hypabyssal Washington (Pearson and Obradovich, 1977, porphyry to country rock appears to exceed p. 23, 40). In most of Republic graben 1:10, and label "Th" denotes areas where (Bald Knob and Nespelem quadrangles), shown country rock appears to be entirely as a single unit, coarsely stippled in absent. Individual dikes shown (by paired Nespelem quadrangle where abundantly tuffa lines) only where strike known. Groundmass ce ous. In Keller graben (Keller of porphyry typically holocrystalline at quadrangle), and in an eastern pert of centers of large dikes but cryptocrys- Republic graben (Seventeenmile Mountain talline at chilled margins of dikes. Most quadrangle, east of dotted meridian), of the intrusions abound in equant white phenocrysts of plagioclase along with a few of Stepstone Creek; some are known to percent phenocrysts of biotite; some also Intrude the main phase of the granite of contain phenocrysts of quartz. Dark- Moses Mountain and(or) to be cut by dikes colored, hornblende-bearing, quartz-poor or of the Stepstone Creek. Also included in quartz-free Intrusions cut across light- unit is a narrow body of diorite that cuts colored, hornblande-frea, quartz-bearing the Moses Mountain north of Looney Creek intrusions and also cut both the O'Brien (Bald Knob quadrangle) Creek Formation and Sanpoll Volcanics. Hornblende-free intrusions, in contrast, Tgd GRANODIORITE OF JOE MOSES CREEK (Eocene) Fine- cut the O'Brien Creek but not the Sanpoll 10 to medium-grained inequigranular despite a great abundance of hornblende- hornblende-biotite granodiorite forming a free porphyry in dike swans flanking the stock that cuts the porphyritic granite of eastern sides of the Republic and Keller Keller Butte (near Sherman fault, Nespelem grabens. These age relationships, together quadrangle) and forming several nearby pods with petrologlc similarities between cutting the diorite of Devils Elbow. Also intrusive and extrusive sequences, suggest present, but not shown on map, as small that hornblende-free porphyry is an asses among hypabyssal-porphyry dikes east intrusive equivalent of the O'Brien Creek of Keller graben between John Tom Creek and Formation, and that much of the hornblende- Columbia River (Keller and Wllbur bearing porphyry is an Intrusive equivalent quadrangles). Cut by hornblende-bearing of the Sanpoil Volcanics. All hypabyssal dikes of the hypabyssal intrusive suite of porphyry contains hornblende where known to Cody Lake. Distinguished from diorite of cut the porphytitle granodiorite of Mission Devils Elbow by low color index (typically Creek, the diorite of Devil's Elbow, the less than 5) and presence of fine-grained grano-dlorite of Joe Moses Creek, the groundmass granite of west of Armstrong Mountain, and the plutonic complex of Johnny George Tqm QUARTZ MONZONITE OF SEVENTEENMILE MOUNTAIN Mountain. All porphyry known to cut Reed 11 (Eocene) Inequigranular, medium-grained, Creek quartz diorite gneiss lacks hornblende-biotite quartz monzonite hornblende and contains phenocrysts of intruded into diorite of Devils Elbow near quartz. Excepting these occurrences, and Seventeemile Mountain. Also shown as excepting porphyry cutting Sanpoil border to the granite of Deadhorse Creek in Volcanics, rock units shown as cut by stocks intruding the granite of Daisy hypabyssal porphyry are cut by both Trail. Commonly pink to brown hornblende-free and hornblende-bearing varieties, commonly but not always in the Tgs HORNBLENDE-BEARING GRANITOID ROCKS OF SWIMPTKIN same area. Age of hornblende-bearing 12 CREEK (Eocene) Medium-grained equigranular porphyry about 47-50 m.y. Judging from K/Ar hornblende-blotite-quartz monzodiorite to dates on three dikes in Republic graben granodiorite (CI 10-25) forming a large (table 1) pluton that extends southward from the northern border of the map about 14 mi east Plutonic rocks of the Okanogan River. Accessory sphene is generally present. Inclusions of Tvg VARIED GRANITE NEAR STEPSTONE CREEK (Eocene) hornblende gabbro, diorite, and para- 7 Massive, fine- to medium-grained gneissic country rocks are common, the leucocratic (CI-5) granite that shows latter composing numerous roof pendants marked textural variations at outcrop that are widely distributed across the scale. Forms mapped and unmapped bodies, west-central part of the pluton. along and near Stepstone Creek between Metamorphic grade in the inclusions and Moses Mountain and Little Moses Mountain, roof pendants is as high as the sillimanite that cut the main phase of the granite of zone of the amphibolite facies; some of the Moses Mountain and also cut local mapped inclusions resemble mylonitic rocks of the and unmapped bodies of the diorite of Okanogan gneiss dome (Fox and others, 1976, Little Moses Mountain. Also includes, for p. 1221). Grain size is locally very convenience, a plug of fine-grained biotite coarse in some of the inclusions and roof- granite that crosses Stepstone Creek 3 mi pendant rocks, and the pluton itself shows northwest of Gold Lake a wide variety of coarse and unusual textures and compositions near metamorphic Tg GRANITE OF DEADHORSE CREEK (Eocene) Biotite rocks. Little is exposed of the pluton's 8 granite forming stocks scattered near southeastern lobe, which underlies the eastern margin of Republic graben. Fine topographic basin of Moses Meadow, but grained, equigranular, and light gray to contacts observed there dip gently outward light brown where Intruded into the quartz or are horizontal. The rocks in the south monzonite of Seventeemile Mountain and eastern lobe also appear to be somewhat into the granite of Daisy Trail; but medium more homogeneous and slightly finer grained, and commonly seriate and pink grained. Throughout most of the pluton the where Intruded into the diorite of Devils rocks are massive but both flow foliation Elbow. K/Ar biotite age (table 1) about and mylonitic fabric of the Okanogan gneiss 50 m.y. May be plutonic equivalent of the dome are locally present in the westernmost intrusive rhyolite near West Fork parts. Near the southwestern contact with the Clark Creek phase of the granite of Tdl DIORITE OF LITTLE MOSES MOUNTAIN (Eocene) Moses Mountain, the latter clearly cuts the 9 Massive, fine- to medium-grained hornblende Swimptkin Creek, but along Mackey Ridge, diorite exposed primarily in mapped and bordering Moses Meadow on the northeast, unmapped bodies along the valley of excellent exposures of the contact with the Stepstone Creek between Moses Mountain and main phase of the granite of Moses Mountain Little Moses Mountain. These bodies are in show age relations that are equivocal. the same general area as the varied granite K-Ar dates on biotite and hornblende are about 49 m.y. except for a hornblende age pluton and which is cut In Coyote Canyon by of 45 m.y. that Is probably erroneous granite dikes petrographically indistin (table 1) guishable from the Armstrong Mountain. Cut by dikes of biotite-hornblende hypabyssal GRANITE OF MOSES MOUNTAIN (Eocene) Large porphyry similar to rocks that are composite pluton of (muscovite)-blotite components of the nearby intrusive complex granite that lies northwest of Nespelem and north of Grant Lake. K-Ar biotlte age extends to the northern boundary of the about 52 m.y. (table 1) reservation. Merges Into the unit, undivided granitic rocks near Gold Creek, Tdd DIORITE OF DEVILS ELBOW (Eocene)--Medium- along the cannon boundary of the Dlsautel 17 grained, mostly equigranular (auglte)- and Bald Knob quadrangles, from Steps tone biotite-hornblende plutonic rocks ranging Creek to North Star Creek. This Is the from diorlte to tonalite, granodiorite, and result of an attempt In 1980-1983 to granite. CI mostly 10-20 but locally up to distinguish Individual plutons within 50. Typically contains accessory sphene. granitic terrane referred to as "Colvllle Forms Devils Elbow pluton, between Republic batholith" by earlier workers. Much of and Keller grabens; Ball Creek pluton, east that terrane In the Bald Knob quadrangle of Republic graben near Seventeenmile was not examined by USGS mappers In 1980- Mountain; Friedlander pluton, east of 1983 Keller graben beside Brody Creek fault; mall intrusions north of Klondyke Creek in Tgm Main phase Coarse (3 mm av), leucocratlc (CI Seventeenmile Mountain quadrangle; and 13 5), In places serlately porphyrltlc with 1- small intrusions cutting the plutonic 2 cm subhedral K-f elds par phenocrysts. complex of Johnny George Mountain along the Quartz Is dark gray. Generally massive, shores of Franklin D. Roosevelt Lake in the the rocks are locally deformed by weak to Lincoln quadrangle. Near Devils Elbow and moderate mylonitic fabric with llneatlon south of Brush Creek, appears to grade into parallel to that of the Okanogan gneiss hornblende-bearing parts of the hypabyssal- dome. Biotite Is the only dark mineral, intrusive complex of Cody Lake. Cut by excluding sparse, dispersed aggregates of granodiorite of Joe Moses Creek, granite of magnetite. Muscovite is not uncommon but Deadhorse Creek, a few hornblende-bearing is sparse; some Is secondary but some may dikes of hypabyssal porphyry, and aplite be primary containing miarolitic cavities. Yields K/Ar ages between 44 and 51 m.y. (table Tgmc Clark Creek phase Distinguishable from main 1). For convenience, also includes a small 14 phase only by finer average grain size (2 (2 ml2 ) body of dlorite along the south mm) of the Clark Creek. Contacts with main western margin of the Republic graben about phase typically gradatlonal over 0.01-0.2 2 mi southwest of Gold Lake, although that mi; zone of gradation even broader south rock may be older than others included east of Moses Mountain and in the Lost here, Inasmuch as it is intruded by Creek area. Massive except locally and in adjacent granitoid rocks (Staatz, 1964, p. westernmost parts where the rocks show weak 23) mylonitic fabric that becomes increasingly well developed westward. Thin dikes of Brecelated rocks probable Clark Creek phase cut and include rocks of the Swlmpkin Creek pluton near the Tic INTRUSIVE COMPLEX NORTH OF GRANT LAKE eastern pert of their mutual contact. K-Ar 18 (Eocene) >Crop8 out as a small ellipical biotlte age about 49 m.y. (table 1) body about 6 mi west of Nespelem. Consists mainly of hornblende-bearing and Tgmw Uhitelaw Creek phase Varied in both texture hornblende-free hypabyssal porphyry 15 and composition probably owing to contam resembling the hypabyssal intrusive suite ination by metamorphic rocks that are of Cody Lake; medium-grained (2 mm av) moderately abundant but are generally too biotite-hornblende diorite, and medium- small to map. Ubiquitously associated with grained (1-2 mm) biotite granite. Some of abundant pegmatite as dikes and masses of the granite resembles the granite west of irregular shape, and with alaskite whose Armstrong Mountain. The diorite and textures range from aplitlc to pegmatitic, perhaps also the granite locally contain and which is commonly host to swarms of partly digested pieces of hornblende- tiny pink to red garnet crystals. Contacts bearing hypabyssal porphyry; additionally with the Clark Creek phase are gradational the diorite contains sparse granitic over tens of meters, but are typically inclusions referable to the Coyote Creek abrupt with the porphyritic granite of pluton. All rock types are commonly cut by Coyote Creek, which at one locality, Is cut a network of closely spaced faults of by a thin dike of the Uhitelaw Creek. diverse orientations. Most or all of the North and east of Strawberry Mountain (Bald faults post-date emplacement of the unit. Knob quadrangle), lacks metamorphic xenoliths and consists partly of bfs BRECCIA WEST OF FORT SPOKANE (Eocene) Weakly fine-grained biotite-muscovlte granite 19 consolidated tectonic breccia composed of granitic and volcanic rocks in generally Tga GRANITE WEST OF ARMSTRONG MOUNTAIN (Eocene) heterogeneous distribution, but with local 16 Biotlte granite and granodiorite, medium- suggestion of subtle gently east-dipping grained (2mm av), equigranular, layers showing crude alternating abundance homogeneous, and leucrocratic (CI 5), of granitic and volcanic fragments. contains sparse but widespread sphene and a Limited to a narrow zone of discontinuous trace of hornblende; forms a small pluton exposures 4 mi long along the western shore about 8 ml northwest of Nespelem. Probably of Roosevelt Lake (Lincoln quadrangle). younger than the porphyritic granite of Fragment size ranges from less than a Coyote Creek which encloses the entire millimeter to about a meter. Varied degree of clayey alteration commonly obscures with Tonasket Gneiss. Penetrative identity of parent rock. Volcanic mylonitlc foliation and lineation common, llthologles are similar to those exposed, though locally Inconspicuous in equi- undeformed, in nearby outcrops of Sanpoll granular rock. Cut by numerous thin (0.5 Volcanics and hypabyssal equivalents. Most m) dikes of pegmatite, aplite, and identlfyable granitic fragments from the granite. In some places contains xenollths southernmost exposure are strongly of probable Mission Creek; in others, lineated, resembling similar rocks to the gradational into the Mission Creek over as west in the plutonlc complex of Johnny much as 50 m. The northeasternmost part George Moutaln. Age range shown on consists mainly of biotite and biotlte- correlation chart is that Inferred for the hornblende tonalite whose correlation with brecclatlon French Valley Is uncertain (shown as "gfv?") CHARACTERISTICALLY MYLONITIC ROCKS OF THE GNEISS DOMES 23 PARAGNEISS AND ORTHOGNEISS OF HALL CREEK Mostly well-llneated slllimanite-grade tg TONASKET GNEISS High-grade gneiss and schist rocks in the northeastern part of the 20 that form the southernmost part of a large reservation, bounded primarily by the body, west of the Okanogan River, that granite of Daisy Trail to the south and extends about 30 mi north of Omak (Fox and west and by chlorite-grade rocks of the others, 1976). Includes hornblende-blotlte Covada Group on the east. Contact with the gneiss, blotlte-gnelss, K-feldspar augen Daisy Trail is broadly gradational through gneiss, sillimanite-garnet-muscovite- granitic gneiss; contact with the Covada is biotlte schist, blotlte quartzite, a narrow gradational change in metamorphic amphibollte, pyroxene calc-sllicate gneiss, grade, both with and without associated and garnet-bearing alasklte gneiss. Fine zones of sheared or brecclated rock, that grained mafic rocks show pronounced mineral dips gently eastward. Divided into: lineation and schlstoclty. Penetrative mylonitlc foliation and lineation dominate hgg Granitic gneiss Biotite gneiss with or the Internal structure of the rocks in the without muscovite, more homogeneous and western part of the unit. These probably older than granitic gneiss in the structures, which Intensify westward, are northeastern part of the Daisy Trail sparse east of the scalloped line, and appear to postdate a high-grade hog Orthogneiss of Onion Creek Biotite gneiss dynamothermal metamorphism of the rock restricted to a small band between Onion (Snook, 1965; Goodge, 1983). Intruded by and Barnaby Creeks. Protolith possibly the porphyritlc granodiorite of Mission Creek granodiorite of Barnaby Creek or the and by granodiorite of French Valley, granite and granodiorite near Meteor probably before mylonitlzatlon hmg Mafic gneiss Contains biotite and gpg GNEISSIC PORPHYRITIC GRANODIORITE OF MISSION hornblende; locally includes marble. 21 CREEK Extensive plutonlc body lying east Adjoins orthognelss of Onion Creek of Omak and north of Omak Lake. Light- to medium-gray, homogeneous, foliated, hms Metasedimentary gneiss Biotite schist and coarsely porphyritic rock of which 1-5 quartzite, locally interlayered with percent is composed of gray to pink (muscovlte)-blotite granitic gneiss. K-feldspar megacrysts (2-8 cm), the Divided into: remainder composed of an equlgranular, medium-grained (0.5-5 mm) matrix of quartz, hq Quartzite Unlayered to thickly layered plagloclase, blotlte, and minor K-feldspar, sphene, and iron oxides (CI-5-7). Contains hqs Quartzite and schist numerous thin (<0.5 m) dikes of aplite pegmatite and granite and tabular, rounded, hi Interlayered quartzite, schist, and dark inclusions of amphibolite and biotite granitic gneiss schist ( 10 contain hornblende, lighter rocks (CI 3-10) Moses Mountain, along this segment of the generally do not. Most rocks contain boundary, were not examined by UGSG mappers sphene. Unit commonly includes layers, in 1980-1983 lenses, and irregular Basses of fine grained (0.1-0.5 mm) dark (CI 20-40) NON-MYLONITIC METAMORPHOSED ROCKS SEDIMENTARY AND dioritic rock, some of which may represent MAFIC IGNEOUS metamorphosed relicts of a protolith but others of which (southwest of Goose Lake, Eugeoclinal rocks are widely distributed in the map in SE/4 sec. 29, T. 31 M., E. 29 E.) area but extensive only east of the Sanpoil River and originated as dikes. Dikes of aplite and along the western side of the Republic graben. Pardee pegmatite locally abundant. Gneissosity (1918) assigned most of the rocks to the Covada and tabular inclusions in southern part Group. We retain this name in most areas east of the generally strike within 30° of north. Sanpoil River but apply other names farther west Mylonitic foliation north of Kartar Creek wherever correlation with the type Covada is doubtful. partly cross-cuts and partly reorients this fabric and becomes increasingly common pTsc SALMON CREEK SCHIST AND GNEISS OF MENZER (1983) progressively northwestward from that 51 (pre-Tertlary) Extensively exposed south locality; the mylonitic rocks are labelled east of Okanogan, generally along the "pcbm" . Locally, the Boot Mountain projected strike of similar rocks to the contains sparse large (5 cm) K-feldspar northwest, the Salmon Creek comprises megacrysts along contact with the high-grade, compositionally layered, mostly porphyritic granodiorite of Mission Creek metasedimentary rocks, and subordinate and roughly tabular aggregates of many such metavolcanic gneiss and schist. Rock types megacrysts near contact with the include hornblende-biotite gneiss, feldspar porphyritic granite of Coyote Creek. Near augen gneiss, biotite gneiss, sillimanite- Omsk Lake, brecciated parts of unit are muscovite-biotite schist, biotite- riddled with chlorite-lined fractures and quartzofeldspathic schist, amphibollte, conspicuously colored by pink feldspar and quartzite, biotite quartzite, marble, bluish-gray quartz. Near mouth of Barrison garnet-pyroxene calc-silicate gneiss, Creek, the Boot Mountain consists primarily coarse hornblendite. A well-developed of light-colored fine- to coarse-grained metamorphic foliation, commonly with biotite granite that is riddled with mineral lineation, parallels compositional closely spaced (0.2-5 cm) fractures lined layers. Mesoscopic tight to isoclinal, with a purplish oxide. Near the southeast similar folds are present locally, corner of sec. 8, T. 31 N., R. 29 E., this especially in the schistose rocks. Axial shattered granite grades into a maroon planes parallel metamorphic foliation and cataclasite that does not crop out on the layering; fold axes parallel mineral facing ridge, northwest of Harrison lineations. Assemblage is regionally Creek. That part of the complex labelled metamorphosed to sillimanite zone of pcbe is distinct from rest of the Boot amphibolite fades. Mobilized granitic Mountain only by its lack of mlgmatitle material is present locally, especially in character, except along the contact with westernmost body where the Salmon Creek is the Salmon Creek schist and gneiss, and in part, migmatite. Rock labelled "d" is further, by being generally equigranular dunite, which forms a small metamorphosed and somewhat more homogeneous than the rest mass in center of elongate body of the of the Boot Mountain. K-Ar ages from Salmon Creek a mile southwest of Omak Lake pcbe: biotite, 49 m.y.; hornblende 72 m.y. (table 1) sdh SCHIST NEAR DEERHORN CREEK Dark-colored (CI 52 15-20) hornblende-orthoclase-biotite- csm PLUTONIC AND HETAMORPHIC COMPLEX OF SQUAW quartz-plagioclase schist separating 49 MOUNTAIN Crops out as a northeast greenstone from light-colored biotite ward-trending body west of Nespelem. granite and aplo-pegmatite near the West Greenstone and metadiorite; schist and Fork of the Sanpoil River (Bald Knob gneiss composed of pelitic and subordinate quadrangle). Banded with veins of psammitic and calc-silicate rocks; and pegmatite. Called quartz diorite by Staatz equigranular, medium-grained, sphene-poor (1964, p. 29-30), who interpreted it as a granitoids that resemble parts of the deformed batholithic margin. plutonic complex of Boot Mountain. Largely Alternatively, a paragneiss riddled with hypabyssal-porphyry dikes. Linear contact (Multnomah fault) with pTm METASEDIMENTARY ROCKS BETWEEN OMAK LAKE AND Coyote Creek pluton probably represents the 53 SOUTH SEVENTEENMILE MOUNTAIN (pre- western margin of the southerly extension Tertlary) Low- to high-grade rocks forming of the Republic graben a belt averaging 3 mi in width on west side of Republic graben, and small isolated ugg UNDIVIDED GRANITIC ROCKS NEAR GOLD CREEK bodies elsewhere in central part of 50 Biotite granite and granodiorite centered reservation. The belt along the Republic about 15 ml north of Nespelem. Probably graben contains graywacke, phylllte, black dominated by rocks of Moses Mountain and shale, quartzite, quartz-mica schist, and Coyote Creek plutons. Merges into the minor limestone. The isolated bodies granite of Moses Mountain along the common elsewhere are mostly fine- to coarse boundary of the Disautel and Bald Knob grained pelitic and psammitic granofels, quadrangles, from Stepstone Creek to North schist, and gneiss, locally accompanied by Star Creek. This is the result of an calcareous and meta-volcanic rocks. Ortho- attempt in 1980-1983 to distinguish quartzite is a noteworthy constituent individual plutons within granitic terrane southeast of Moses Mountain and is referred to as "Colville batholith" by associated at one locality with sharpstone earlier workers. Rocks in the Bald Knob conglomerate, a rock type common in meta quadrangle contiguous with the granite of sedimentary assemblages of the Permian 11 Anarchist Group several tens of miles sequence unknown. Age Pennsylvanian(?) northwest of the locality. Other rock* in according to David White (Bancroft, 1914, the unit, particularly those east of the p. 14-15), who described plant fossils in Republic graben and K-feldspar-rlch limestone near Silver Leaf mine (Inchelium grayvacke west of that graben, may belong quadrangle); but more probably Early to the nearby Covada Group, whose age is Ordovician according to Snook and others Ordovician, at least in part (Snook and (1981) who cite conodonts and other animal others, 1981) fossils indentified by John Repetski and Peter Ward from localities just off the pig GREENSTONE OF ROARING CREEK (pre-Tertiary) reservation, about 4 mi east-northeast of 54 Fine-grained rock, locally with pillow the mouth of Little Jim Creek (Inchelium structures, located west of the Republic Oc quadrangle). Shown undivided (Oc) in a graben near the north edge of the Bap small strip north of Barnaby Creek area. Chiefly hornblende and plagio- (Inchelium quadrangle); elsewhere divided clase. Protolith probably extrusive into: andesite according to Staatz (1964, p. 17) Ocp Pelitic and psammitic rocks Greywacke, pTsp SERPENTINITE NEAR PARMENTER CREEK (pre- locally conglomeratic; Impure quartzite; 55 Tertiary) Serpentinite snd talc-magnesite slate; and minor pods of limestone and rock forming small bodies near bounding greenstone. Locally upgraded to hornfels, faults of the Republic graben. The largest phyllite, or quartz-mica schist. Beds as body is located 8.5 mi north of Nespelem; thick as 4 m, some of them graded from other smaller bodies lie nearby and also granule conglomerate at base to argillite about 10 ml to the southeast. The bodies at top. Stipple in Twin Lakes quadrangle north of Nespelem cut pre-Tertiary denotes blue quartzite. Phyllite commonly quartzite, and two of them are cut by dikes spotted with chlorite; schist near the of the hypabyssal-intrusive suite of Cody porphyritic granodiorite of Manila Creek Lake; otherwise the age of emplacement of contains andalusite in some places and the serpentinite is unconstrained (Staatz, sillimanlte in a few others 1964, p. 31) Occ Carbonate and argillaceous rocks Limestone pTum ULTRAMAFIC AND MAFIC ROCKS NEAR BRIDGE CREEK and dolomite, mostly impure and locally 56 (pre-Tertiary)~Talc-carbonate rock, upgraded to marble, that are commonly greenstone, and minor serpentinite and interlayered with slate, phyllite, and meta-tuff(?) northeast of the Keller greywacke. Large body in Keller quadrangle graben; also forms a small fault-bounded near Ninemile Creek owes much of its sliver 5 mi east of graben. Northeast of east-west extent to crosscutting swarms of the graben, owes much of its east-west apio-pegmatite dikes (in area patterned extent to cross-cutting dikes of the with X's) and hypabyssal-porphyry dikes. hypabyssal intrusive suite of Cody Lake. The northeastern part of this body appears Much of the greenstone may have originated to grade, through interlayered limestone as diabase and gabbro because it commonly and phyllitic slate, into the adjoining preserves laths of plagioclase and a pelitic and psammitic rocks. The north subophitic texture. Possibly the Bridge western part of the body was either Creek represents oceanic crust and mantle deposited on or faulted against the on which edjacent parts of the Covada Group ultramafic and mafic rocks of Bridge accumulated; alternatively, the Bridge Creek. An elongate, fault-bounded body Creek and the Covada were brought together between Wilmont and Nez Perce Creeks tectonically from widely separated areas consists largely of greywacke and lesser greenstone pTmi MAFIC INTRUSIVE ROCKS NEAR TWIN LAKES (pre- 57 Tertiary) Metamorphosed mafic rocks some Ocg Greenstone Metamorphosed subaqueous basalt of which are known to be intrusive into the flows containing many calcite-filled Covada Group. The unit comprises meta- amygdules, few pillow structures, and gabbro, which forms a small body between interbeds of argillite, limestone, basaltic the North and South Forks of Hall Creek, sandstone, and pyroclastic rocks. Widely 9 mi north-northeast of Twin Lakes; and but sparsely distributed among pelitic and greenstone, which forms a dike between psammitic parts of the Covada north of Nez Nlnemile and Wilmont Creeks, 14 mi south of Perce Creek Twin Lakes. Additional mafic rocks known or believed to intrude the Covada Group form small bodies (not shown on map) in the Wilbur quadrangle, 1 mi south-southeast of the mouth of Dick Creek and also in section 35, T. 29 N., R. 33 E. COVADA GROUP (Ordovician) Low- to medium-grade 58 metasedimentary and minor meta-volcanic rocks abundantly exposed between the lower Sanpoil River valley and the northeastern corner of the reservation. As mapped by Pardee (1918), the Covada embraces nearly all metasedimentary rocks in the reser vation east of Omak Lake; but following Fox and Rinehart (1974), we restrict the term to rocks whose coarse-clastic facies locally contain granitic detritus, partic ularly K-feldspar. Internal stratigraphic 12 Table I. Potaaalua-argon age* froa volcanic and Intrusive rock* of to* Colvlll* Indian Reservation, compiled by Robert J> Fleck (Nuaber In parentheses following naaa of sap unit refer* to numbering eyetea In correlation and description of tap unite] Radiogenic 40Ar Field Collector 15-mlnut* Latitude Longitude Mineral do'10 (percent lAg. Remark* Nuaber Quadrangle North Weet (percent) mo l/i ) oJ0tot.l (m.y.) SANPOIL VOLCANICS, OFFER UNIT (3) FM8480-1 F. J. Moye Seventeenalle 48*25.61' 118*43.47' Blotlte 2n.a. n.a. n.a. 48.5*0.3 Lava flow probably near Mountain top of Sanpoll aectlon In thle part of Republic greben 78KF28L-3 K. F. Fox, Jr. Keller 48*13.99' 118*40.17' Blotlte 8.13 5.97 82.8 50.3*0.4 Vltrophyrlc lava flow underlain by about 150 a of a*h-flow tuff INTRUSIVE RHYOLITE NEAR WEST FORK (5) FM9480-1 F. J. Moye Seventeenalle 48*28.03' 118*42.47' Blotlte 8.58 6.20 92.8 49.5*0.3 Unit Intrudee part of Mount e In upper unit of Sanpoll Volcanic* KYPABYSSAL-INTRUSIVE SUITE OP CODY LAKE (6) FMB2681-2 F. J. Moye Sevente*nalle 48*15.95' 118*41.07' Blotlte n.a. n.e. n.a. 46.7*0.4 Dike probably coaagaatlc Mountain Hornblende n.e. n.e. n.a. 38.010.4 with the adjacent dlorlte of Devil* Elbow. Agee purloua? FM91780-3 do . do. 48*27.68' 118*38.63' Hornblende 0.966 0.696 70.4 49.410.3 Dike Intrude* part of upper unit of Sanpoil Volcanic* FM82980-10 do do. 48*27.23' 118*38.04' Blotlte 7.02 5.16 64.6 50.3*0.3 do. GRANITE OP DEADHORSE CREEK (8) FM91780-2 F. J. Moye Seventeenalle 48*16.43' 118*41.65' Blotlte 9.38 6.79 82.9 49.6*0.3 Unit Intrude* dlorlte of Mountain Devil* Elbow HORNBLENDE-BEARING GRANITOID ROCKS OF SWIMPTKIN CREEK (12) 0-419 K. F. Fox. Jr. Dleautel 48*25.65* 119*09.15' Blotlte 8.89 6.39 77.7 49.2*1.5 Reported by Fox, Rlnehert, Hornblende 0.864 0.623 57.9 49.4*1.5 Engele, *nd Stern (1976, p. 1220) SS-340 S. H. Singer Dleautel 48*24.80' 119*10.58' Blotlte 8.60 6.21 53 49.5*1.2 Hornblende 1.00 0.66 38 45.3*1.1 Contaminated? GRANITE OF MOSES MOUNTAIN, CLARK CREEK PHASE (1*) SS-341 S. H. Singer Dlaautel 48*24.20' 119*10.84' Blotite 8.73 6.29 56 49.4*1.2 Unit Intrudee dlorlte of Swlaptkin Creek GRANITE WEST OP ARMSTRONG MOUNTAIN (16) SS-351 S. H. Singer Dlaautel 48*15.40' 119*08.37' Blot It* 8.15 6.26 44 52.511.3 Unit probably Intrudea granite of Coyote Creek DIORITE OF DEVILS ELBOW (17) RUB-54453 R. W. Holder Seventeenmlle 48*28.61' 118*32.37' Blotlte 8.93 5.91 57 45.2*1.1 Hall Creek pluton Mountain Hornblende 0.678 0.471 28 47.7*1.2 H-51C C. D. Rlnehart Neapelea 48*09.99' 118*46.08' Blotlte 8.62 6.24 55 49.6*1.2 Devila Elbow pluton FM91780-1 F. J. Moye Seventeenmll* 48*16.28' 118*42.50' Blotlt* 8.29 6.04 78.0 49.9*0.3 do. Mountain CNEISSIC PORPHYRITIC CRANODIORITE OF MISSION CREEK (21) 0-425 K. F. Fox, Jr. Oaek Lake 48*23.45' 119*26.52' Blotlte 9.45 6.50 82.9 47.2*1.4 Reported by Fox, Rlnahart, Engele, and Stern (1976, p. 1220) PORPHYRITIC GRANITE OP COYOTE CREEK (25) O-424B K. F. Fox, Jr. Dlaautal 48*16.85' 119*08.42' Blotlte 9.02 6.63 77.8 50.4*1.5 Reported by Fox, Rlnehart, Engele, and Stern (1976, p. 1220) BA-82-54B B. F. Atwater Alaaeda Flat 48*01.16' 119*08.11' Blotite 8.96 6.69 68 51.1*1.3 13 PORPHYRITIC GRANITE OF KELLER BUTTE (27) 165677 W. C. Utterback Grand Coulee 47*59.67' 118*50.30' Blotlte n.a. a.a. n.a. 61.312.3 Blotlte weathered and t. Bed ley Da» ALTERED GRANITE OF MEADOW CREEK (28) ULLER a.a. Keliar 48*03.58' 118*41.53' K-feldepar 11.46 10.33 89.6 51.211.8 Reported by Anutrong, Harakal, and Holllater (1982) QUARTZ PORPHYRY OF MOUNT TOLMAN (29) A.-56471 W. C. Utterback Keliar 48*03.39' 118*42.20' Serlclte n.a. a.a. n.a. 55.712.0 From AMAX core DH-6. aad C. Dvkeaan State coordinate*: M392.653; W2,521,050 A.-56470 do. do. 48*03.24' 118*42.14' Muscovite n.a. n.a. n.a. 57.712.1 From AMAX core DH-24. State coordinate*: N391.787; W2,521.050 GRANITE OF SUAWILLA BASIN (30) A65679 W. C. Utterback Netpelen 48*0a.47' 118*48.43' Blotlte a.a. 58.812.2 Unit probably Intruded ad R. Bed ley by porphyrltlc granlta of teller Butte GRANITE OF DAISY TRAIL (32) MUME985C R. V. Holder Seventeeoalle 48*15.00' 118*31.57' Blotlte 9.03 6.57 73.3 49.910.3 Hoawgeneou*. Mountain grained PORPHYRITIC CRANODIORITE SOUTHWEST OF OMAK LAKE (39) BOL-39 V. L. Hansen 0»ak Lake 48*17.63' 119*26.39' Blotlte 9.53 7.44 75 53.411.3 GRANITE AND CRANODIORITE NEAR METEOR (41) B-51B K. F. Fox, Jr. Tvlo Lakaa 48*15.32' 118*22.52' Blotlte 8.40 6.68 92.8 54.510.4 REED CREEK QUARTZ DIORITE GNEISS OF KENZER (1983) (44) to 1-276 T. I. HanMn OMk Lake 48*16.68'T 119*26.91'T Blotlte 9.22 7.77 80 57.411.4 Hornblende 1.35 1.50 57 75.211.9 CRANODIORITE NEAR ROGERS BAR (45) I-52B K. P. Fox, Jr. Wllmoot Creak 48*03.51' 118*17.54' Hornblende 0.998 1.04 16.6 71.112.0 PLUTONIC COMPLEX OP BOOT MOUNTAIN, EQUIGRANULAR PHASE (48) o 1-2 7 7 T. L. Hanaen Oaak Lake 48*19.57' 119*29.30' Blotlte 9.42 6.71 52 48.911.2 Hornblende 1.32 1.39 59 72.111.8 lDceay coaataat* for K: 40K/K - l/167xlO~* aol/aol; laafcda B - 4.962xlO'10 yr'1 ; laabda epellon plu* laaibda ep.llon prl»e - 0.581xlO~10 yr'1 ; date* of res and other* (1976) recalculated with theee conatanta by eana of Dalryiple 1 * (1979) conversion teble. a.a., aot available; do., ditto. 14 REFERENCES Lemke, R. W., Mudge, M. R., Wilcox, R. E., and Powers, H. A., 1975, Geologic setting of the Glacier Peak Armstrong, R. L., Harakal, J. E., and Hollister, V. and Mazama ash-bed markers in west-central F., 1982, Eocene mineralization at Mount Tolman Montana: U.S. Geological Survey Bulletin 1395-H, (Keller), Washington, and Silver Dyke, Montana: 31 p. Isochron/West, no. 33, p. 9. Mehringer, P. J., Jr., Sheppard, J. C., and Foit, F. Atwater, B. F., 1983, Guidebook for 1983 Friends of F., 1984, The age of Glacier Peak tephra in the Pleistocene field trip to the Sanpoil River west-central Montana: Quaternary Research, valley, northeastern Washington: U.S. Geological v. 21, p. 36-41. Survey Opan-Flle Report 83-456, 19 p. Menzer, F. J., Jr., 1983, Metamorphism and plutonlsm Bancroft, Rowland, 1914, The ore deposits of north in the central part of the Okanogan Range, eastern Washington: U.S. Geological Survey Washington: Geological Society of American Bulletin 550, 215 p. Bulletin, v. 94, p. 471-498. Becraft, G. E., 1966, Geologic map of the Wilmont Mlnard, J. P., 198_, Geologic map of Quaternary Creek quadrangle, Ferry and Stevens Counties, deposits of the Pothole 7.5-minute quadrangle, Washington: U.S. Geological Survey Geologic Okanogan County, Washington: U.S. Geological Quadrangle Map GQ-538, scale 1:62,500. Survey Miscellaneous Field Studies Map MF-1680, Broch, M. J., 1979, Igneous and metamorphic patology, cale 1:24,000. [in press] structure, and mineral deposits of the Mineral Newcomb, R. C., 1937, Geology of a portion of the Ridge area (Moses Mining District), Colvllle Okanogan Highlands, Washington: Ohio, Cincinnati Indian Reservation, Washington: Pullman, University, M.S. thesis. Washington, Washington State University, M.S. Orazulike, D. M., 1982, Igneous petrology and thesis, 204 p., scale 1:12,000. petrochemical variation in the Coyote Creek Campbell, A. B., and Raup, 0. B., 1964, Preliminary pluton, Colville Batholith, and its relation to geologic map of the Hunters quadrangle, Stevens mineralization at Squaw Mountain, Colville Indian and Ferry Counties, Washington: U.S. Geological Reservation, Washington: Pullman, Washington, Survey Miscellaneous Field Studies Map MF-276, Washington State University, Ph. D. thesis, 275 scale 1:48,000. p., scale 1:24,000. Cheney, E. S., 1980, Kettle dome and related Pardee, J. T., 1918, Geology and mineral deposits of structures of northeastern .Washington, in the Colville Indian Reservation, Washington: Crittenden, M. D., Jr., Coney, P. J., and Davis, U.S. Geological Survey Bulletin 677, 186 p. G. H., eds., Cordilleran metamorphic core Pearson, R. C., and Obradovich, J. D., 1977, Eocene complexes: Geological Society of America Memoir rocks in northeast Washington radiometrlc ages 153, p. 463-483. and correlation: U.S. Geological Survey Bulletin Cochran, D. S., and War low, J. C., 1980, Engineering 1433, 41 p. and environmental geology, Mt. Tolman project, Snook, J. R., 1965, Metamorphic and structural history Ferry County, Washington: Unpubl. report, Amax of "Colvllle bathollth" gneisses, north-central Exploration, Inc., and the Colvllle Confederated Washington: Geological Society of America Tribes, Nespelem, Washington, 89 p., scale Bulletin, v. 76, p. 759-776. 1:6,000. Snook, J. R., Lucas, H. E., and Abrams, M. J., 1981, A Coney, P. J., 1980, Cordilleran metamorphic core cross section of a Nevada-style thrust in complexes: An overview, in Crittenden, M. D., northeast Washington: Washington Department of Jr., Coney, P. J., and Davis, G. H., eds., Natural Resources Report of Investigations 25, Cordilleran Metamorphic Core Complexes: 9 p. Geological Society of America Memoir 153, Staatz, M. H., 1964, Geology of the Bald Knob p. 7-31. quadrangle, Ferry and Okanogan Counties, Dalrymple, G. B., 1979, Critical tables for conversion Washington: U.S. Geological Survey Bulletin of K-Ar ages from old to new constants: Geology, 1161-F, 79 p., scale 1:62,500. v. 7, p. 558-560. Streckeisen, A. L., 1973, Plutonic rocks classi Flint, R. F., 1935, Glacial features of the southern fication and nomenclature recommended by the IUGS Okanogan region: Geological Society of America Subcommlssion of the systematica of Igneous Bulletin, v. 46, no. 2, p. 169-194. rocks: Geotlmes, v. 18, no. 10, p. 26-30. Fox, K. F., Jr., and Rlnehart, C. D., 1974, Comparison White, R. 0., 1981, Geology of the Schminski of Anarchist and Covada Groups of north-central molybdenum deposit (Colville Indian Reservation), Washington: U.S. Geological Survey Professional Ferry County, Washington: Pullman, Washington, Paper 900, p. 50-51. Washington State University, M.S. thesis, 103 p. Fox, K. F., Jr., Rlnehart, C. D., and Engels, J. C., 1977, Plutonlsm and orogeny in north-central Washington timing and regional context: U.S. Geological Survey Professional Paper 989, 27 p. Fox, K. F., Jr., Rinehart, C. D., Engels, J. C., and Stern, T. W., 1976, Age of emplacement of the Okanogan gneiss dome, north-central Washington: Geological Society of America Bulletin, v. 87, p. 1217-1224. Fritz, L. G., 1978, Petrography of the crystalline rocks south of Okanogan, Washington: Cheney, Washington, Eastern Washington University, M.S. thesis, 37 p., scale 1:62,500. Goodge, J. W., 1983, Reorientation of folds by progressive mylonitization, Okanogan dome, north- central Washington: Geological Society of America Abstracts with Programs, v. 15, p. 323. Jones, F. 0., Embody, D. R., and Peterson, W. L., 1961, Landslides along the Columbia River valley, northeastern Washington: U.S. Geological Survey Professional Paper 367, 96 p. CONVENTIONAL SYMBOLS CONTACT Location approximate. Length of dashes has no geologic "-"---.^ ^.^ significance. Precision implied by use of dashed line may vary between quadrangles ,. '""* Concealed v \\u»'/"////nl Gradational _--^._ ^./- Interf ingering FAULT Dashed where approximate, dotted where concealed, queried where doubtful D 60 u T High angle, showing sense of displacement and dip Low angle. Barbs point in direction of dip. In Twin Lakes quadrangle, symbol represents narrowly gradational contact f%! between low- and high-grade rocks along which the rocks are sheared or brecciated only locally. In Omak Lake and Lincoln quadrangles, stippled dashed line with barbs denotes inferred extension of breccia zone bordering gneiss dome. Stippled-dashed line without barbs denotes inferred extension of breccia zone whose dip is unknown AXIS OF LARGE FOLD Dashed where location approximate, dotted where concealed, queried where doubtful Anticline, showing plunge Syncline AXIS OF SMALL FOLD Trend and plunge of inclined axis 16 STRIKE AND DIP OF BEDDING Dot on symbol where top of bed known from sedimentary structures ^>- Upright ^ Vertical £--' Overturned 7f STRIKE AND DIP OF FOLIATION \^ Inclined "^ . Vertical j> 1 f 1 Horizontal. Shown with wavy tails where foliation approximately horizontal STRIKE AND DIP OF CLEAVAGE STRIKE AND DIP OF JOINT Inclined Vertical TREND AND PLUNGE OF LINEATION Inclined Horizontal SHEARED ROCK «/>,«*#* ** BRECCIATED ROCK Protolith shown where known. Not shown in units that are characteristically brecciated (the intrusive complex of Grant Lake and the breccia west of Fort Spokane) g) LOCALITY OF SAMPLE FOR POTASSIUM-ARGON AGE DETERMINATION (see //OL-37 table 1) 17 EXAMPLES OF COMBINED SYMBOLS Foliation and lineation Foliation and axis of small fold Foliation and bedding parallel Small fault, showing dip of plane and trend of lineation on the plane 18 ADDITIONAL SYMBOLS, USED MOSTLY FOR ONE OR A FEW UNITS Unit Symbol Meaning Number Letter 1 INFERRED MARGIN OF CORDILLERAN ICESHEET Terminal. Bar and ball toward ice Recessional. Marked by end moraine Tsu PYROCLASTIC ROCK EPICLASTIC ROCK AUTOCLASTIC BRECCIA TRACE OF INDIVIDUAL LAVA FLOW Shown only in Republic graben /IN PLUG OR LARGE DIKE (sole means of representing unit) Th DIKE SWARM Ratio of hypabyssal porphyry to country rock generally exceeds 1:10 (see fig. 3 for an example) STRIKE AND DIP OF INDIVIDUAL DIKE Inclined Vertical Dip unknown 20-22 tg, gpg, APPROXIMATE EASTERN LIMIT OF PENETRATIVELY gfv MYLONITIC ROCK IN THE OKANOGAN GNEISS DOME 24 DIORITE RELATIVELY HOMOGENEOUS GRANITE PORPHYRITIC COARSE-GRAINED GRANITE 19 32 gdt SMALL METAMORPHIC INCLUSION 51 pTsc DUNITE 58 Ocp BLUE QUARTZITE Occ ABUNDANT APLO-PEGMATITE DIKES 20