AN =i)2,7,T Tr: ) In us iihdcn r'-7'. Tf.j.7:1 V A. c; hiDi;I 01 t:i e API) CT7PAL p79VTr,T7,11-77 pp (" A ND Ilrit777 AST2Uf7.17117.-/ OMNTI7S_ _ MGON Abstract approved: Dr. Cyrus W. Field The Fden Valley-Saddle Peaks arealies within the northei:n boundary of the. Ylamath Fountains largely in southeastern Coos County, The rocks of about 12 miles southeast of Powers,southwestern Oregon. the area range in age froll LateJurassic to early Tertiary(j.addie Eocene), but only the Tiesozoic rocks we-tiestudied in detail0 The I esozoic rocks ,:eredefamed by an intense period. of normi and thrust faulting that ,,Jasterminated by large dIsplacem:ent faulting (herein called. the Cnnirope Fault) sootimc batweenpost-r.ly ann 005en t7in..e. The Cane Hope Fault and the Power,-- Agness Fault may be cf the same age. Cope-sr sulfide mineralization at to have the Bolivar (.7opper 1.1inc nearthe center of the area also appears The been e=aaced during thisperiod cf folding and thrustfaultAng, chaloocita associated ore min-red:- consistof chalco',DyTite, bornite, and ,,Thich hese :;r:)er Yd.th Quartz, barite, andaluaite gangue .linerals, all of The 3ogue emplac.:ed in volcanic host rooksof hee aom Ceil-,ation. Fo=nianh08Leen hydroth,?rJ:iily alteredlargely to chlorite and clv nine-s to wineals in 'LOu The ,1.=cent of m.i.nralizat,ion e have been structually controlled,largely by the Roguiddla thrust, rocks of the Bolivar fault contact. .7oth the mineralisation and host Mine are cloely similar tothose of the ATheda illne southeast(.0: the area near Calice, whichimOies a genetic rlationshlo. The Ker)ozoic rocks consist ofthe Rogue, Dothan, Hiddle9 and The Days Creek Formations, the lattertwo comprising the Tyrtle Grous. three contacts among these fourformations are southeast-dipcin7, thrust faults (herein called the Hogue-Dothan,Rogue-Riddle, and Riddle-Days have been the most Creek thrusts). The Rogue-Dothan thrust appears to intense of the three, because it has awide zone of associated cataclasis and recrystallization evident as a.well-developed foliation near the thrust. An ultramafic intrusion(serpentinite) occupies the Rogue-Dothan thrust east of Mt. Bolivar, Thin section study revealed a zone of netasoaticalteration in the volcanic rocks of the Rogue Formation near the ultramafic intrusion. Tn this 7one, calclumAJearing minerals and quartz have comIpletelyreplaced tha original mineral of the Rogue andesitic basalts. Neither of the two remaining thrusts(Rogue-Riddle and Riddle- Days Creek) has an associated zoneof cataclasis and recrystallization of Oregon or an ultramaficintrusion. This contradicts the Geologic Yap West of the 121st Meridian, compiledby F. G. Wells and d. L. Peak and publisbed in l961 which shows anultramafic intrusion along the contact bet'ween volcanic rocks of theDothan Formation (more recentlyincluded This contact is the utIR Lao Rogue Fol.mation) andthe Riddle Formation. sa.e asthe Rogue-Rid:re thrust. Peaks The Geology and Tanera. coits of -S,don Va'lley-Saddle and Vicin:.ty, Southeastern Coos an Cory Conni-AeF, G,-or,on by William Carl Utteroack A TH75IS submitted to Oregon State Univeroity in partial fulfilirent of the requireolents for the deuee of Master of Science June 1973 A2PROVM: Redacted for Privacy Profesor in cha...,:v of major Redacted for Privacy Head of D.71partment of Geology Redacted for Privacy Dean of of Graduate School Date thesis is presented Typed by William Ssrl Utterback L!.3LE OF COL:NT.F.; Pa INTRODUCTION 1 Location, Size, and ':ccesa 1 Topographic Relief, Rock 1:',onsure, andDrainage 4 Climate and Vegetation 5 Purpose and .2,:ethod of Investigation 5 Previous Work 6 8 ROCK UNITS Introduction 6 General Statement 8 The Rogue-Galice-Dothan Controversy 8 Rogue Formation 12 Distribution and Field Description 12 Lithology and Petrography 14 Origin and Depositional Environment 15 Age and Regional Correlation 16 Dothan Formation 16 Distribution and Field Description 16 Lithology and Petrography 18 Origin and Depositional Environment 18 Age and Regional Correlation 19 Serpentinite 20 Distribution and Field Description 20 Lithology and Petrography 21 Origin and Conditions of Intrusion 22 Age and Regional Correlation 23 Riddle Formation 24 Distribution and Field Description 24 Lithology and Petrography 28 Origin and Depositional Environment 29 Age and Regional Correlation 30 Days Creek Foration 30 Distribution and Field Description 30 Lithology and Petrography 32 Origin and Depositional Environment 33 Age and Regional Correlation 33 Tertiary Rocks 34 36 SIRUCTJRAL GEOLOGY Tectonic Setting Folding 39 Rogue and Dothan Formations 39 Nyrtie GrouP 39 Tertiary Warping 41 41 Faulting Thrust Faults 41 aç 45 Norfial Faults 43 Ji.A) ae4onal GEDomorpholo::: 48 Local Geo:norphology 43 ECONOMIC GEOLOGY .50 Location 50 History and Mine Development 50 Geology 53 Sulfide and Gangue Minerals 54 63 Alteration 65 Structural Controls 67 Hypotheses of Origin 71 GEOLOGIC SUMMARY BI3LI03RPHY 77 LIST OF PLA Plate Page from the . View looking southwest across Eden Valley NleaN4- sec. 3, T. 32 S., R. 10 W. Eden Valley crosses the picture from the right foreground to theleft center. Table Rock forms the skyline in theright background. 3 2. A typical south slope exposure of volcanicrocks of the Rogue Formation in the SF..--NW sec. 22, T. 32 S., R. 10 W. 3 3. A typical veined and sheared outcropof the Rogue Formation exposed in a small quarry near theRogue- Riddle thrust in the NW.1-114- sec.16, T. 32 S., R. 10 W. 13 4. A southeast-dipping sandstone and siltstone sequence of the upper member of the Riddle Formationexposed in a road cut near the Riddle-Days Creekthrust in the NW::-NW sec. 16, T. 32 S., R. 10 W. 26 5. View looking north from a ridge crestin the SE.4-SW,; sec. 9, T. 32 S., R. 10 W. The ridge extends from the left foreground to the right background,formed on the southeast-diPpinglimb of a Riddle Formation fold. The ridge is capped by a resistantunit of conglomerate. West-dpping Tertiary strata form the skylined ridge in the left background. 40 6. The recent surface excavation above theold underground workings at the Bolivar CopperMine in the S4N4 sec. 10, T. 32 S., R. 10 W. 7. A high-grade, bornite-chalcocitevein about four inches wide, exposed in the surfaceexcavation shown in Plate 6. 55 bornite-chalcocite vein shown 8. A close-up view of the in Plate 7. Note the network of closelyspaced fractures filled by malachite that cutsthe high- grade copper sulfide vein. 56 LIST OF FIGURES Pag Figure 2 1. Index map of thesis area locationin southwestern Oregon. Page Figure 2. Tactic setting of sputhwestern Oreonand adjacent oceanic crust, Note the discordance between theMesozoic to early Cenozoic arcuate structuralpattern (dashed line:;) and the superimoosed, late CenozoicCascade volcanic arc and faulting (heavylines). This map was modified from the tectonic map of Dott(1971, p. 8). 37 LIST OF TABLES Page Table 1. Stratigraphic section of the EdenValley-Saddle Peaks area. 11 2. Summary of geologic events of theEden Valley-Saddle Peaks area. 75 THE CEOLOGY AND MINEP.AL DEPOSITS OF EDEN VALLEY-SADDLE PEAKS AND VICINITY, SOUTHEASTE?.N CODS AND NOTIEEASTEHN ODUNTIES, OHECIDN INT2,0DUCTION Location, Size, and Accessibility The area of study shown in Figure 1 is located along the northern boundary of the Klamath Mountain geomorphic province(Diller, 1902) in southwestern Oregon. The area is composed of 35 sections, principally in T. 32 S., R. 10 W., that are centrally located in the south one-third of the U. S. Geological Survey Bone Mountainquadrangle (15 Minute Series, Topograohic). Prominent local geographic features include Eden Valley, Saddle Peaks, and Mt. Eolivar. Improved all-weather roads provide access tothe area except during brief periods of heavy snowfall in the wintermonths. The main all-weather road crosses the center of the area from eastto west, joining a paved highway near Powers, 30 miles tothe west, and joining U. S, Highway Interstate 5 at bothGlendale and Wolf Creek, 45 miles to the east. Local access to most of the area is providedto a limited extent by a few all-weather logging roads. These give way to temporary logging roads and jeep trails that arenot maintained. As a result, nearly one-half of the area can be reachedonly on foot. Access is hindered further by dense vegetation throughoutmost of the area, and extremely rugged topography in theeast and southeast parts of the area. 2 Roseburg Coquille Bandon Days Creek S. Umpqua Cape US Highway Interstate 5 Blanco pa A I medo Grants Pass Gold Beach Brookings \--\\ OREGON From Official Highway Map of Oregon, 1971 CAL I FORNIA 0 5 10 15 Through Highways Scaler in Miles Multilane 2 Lane Paved macracmcm All Weather Unimproved in southwestern Oregon. Figure 1. Index map of thesis area location 3 Plate 1. View looking southwest across Eden Valley from the104Tok sec. 3, T. 32 S., R. 10 W. Eden Valley crosses the picture from the right foreground to the left center.Table Rock forms the skyline in the right background. Plate 2. A typical south slope exposure of volcanic rocksof the Rogue Formation in the SF W% sec. 22, T. 32 S., R. 10 W. 4 Topographic Relief, Rock Exposure, and Drainage Within the belt of volcanic rocks that bends acrossthe area from southwest to northeast, the terrain isextremely rugged and sometimes impassable. Maximum relief developed on these volcanic rocks is 3,500 feet. Sedimentary rocks underlie nearly all of the remaining area of study. Terrain developed on the sedimentary rocksis less rugged than that developed on the volcanicrocks. However, dense vegetation on the sedimentary rocks hinderstravel nearly as much as the rugged volcanic rock terrain. Maximum relief of the sedimentary rock terrain is 1,000 feet in the northwestand 2,800 feet in the southeast.