The Eureka Mining District Nevada
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The Eureka Mining District Nevada By THOMAS B. NOLAN GEOLOGICAL SURVEY PROFESSIONAL PAPER 406 Prepared in cooperation with the Ne~ada State Bureau of Mines UNITED· STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1962 •. UNITED STATES DEPARTMENT OF THE INTERIOR STEW ART L. UDALL, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director [Library catalog card follows page 78] For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS Page Page Abstract __________________________________________ _ 1 Geologic structure-Continued Introduction ______________________________________ _ 2 Hoosac fault _______________________ -------- 24 Geography ____________________________________ _ 2 Spring Valley fault zone ____________________ _ 25 History _______________________________________ _ 2 Carbon Ridge-Spring Ridge block _________ ------- 26 Fieldwork and acknowledgments _________________ _ 3 Conical Hill anticline _______________________ _ 26 Rock formations ___________________________________ _ 4 Structural features in the Newark Canyon Cambrian system ______________________________ _ 5 formation _______________________________ _ 26 Prospect Mountain quartzite ________________ _ 5 Hornblende andesite intrusive body __________ _ 26 Pioche shale _______________________________ _ 6 Mahogany Hills block _________________________ -- 27 Eldorado dolomite _________________________ _ 6 Fish Creek Mountains block ____________________ _ 27 Geddes limestone ___________· _______________ _ 7 Age of the structural features __________________ - _ 27 Secret Canyon shale ___________________ ·_____ _ 7 Paleozoic _________________________________ _ 27 Ham burg dolomite _________________________ _ 8 Pre-Newark Canyon-Mesozoic _____________ _ 28 Dunderberg shale __________________________ _ 8 Late Cretaceous ___________________________ _ 28 Windfall formation _________________________ _ 9 Pleistocene and Recent ____ ~ _____________ :.._-- 29 Ordovician system _____________________________ _ 9 Ore deposits ________________________________ ----- --:.. 29 Pogonip group _____________________________ _ 9 Geographic distribution of the ore bodies ___ -.- ____ _ 29 Eureka quartzite ___________________________ _ 10 Form of the ore bodies ________________________ -- 30 Hanson Creek formation ____________________ _ 10 Irregular replacement deposits _______________ _ 30 Silurian and Devonian systems __________________ _ 10 Bedded replacement deposits _______________ -- 36 Devils Gate limestone ___ ..: __________________ _ 10 . Fault-zone replacement deposits _________ .. ___ _ 37 Carboniferous systems __________ ..: _______________ _ 11 Disseminated deposits _________ :_ ____________ _ 39 Chainman shale ___________________________ _ ·11 Contact-metasomatic deposits _______________ _ 39 Diamond Peak formation ___________________ _ 11 Mineralogy ___________________________________ _ 41 Permian system _______________________________ _ 11 Base-metal deposits ________________________ _ 41 Carbon Ridge formation ____________________ _ 11 Windfall gold ore __________________________ _ 44 Cretaceous system _____________________________ _ 12 Contact-metasomatic ores __________________ _ 46 Newark Canyon formation __________________ _ 12 Tenor of the ores ________________ - ----- _- ------- 46 Igneous rocks of Cretaceous age _________________ _ 13 Origin of the ores ______________________________ _ 48 Quartz diorite _____________________________ _ 13 Source of the metals _______________________ _ 48 Quartz porphyry ___________________________ _ 14 Relation of the ore bodies to faults ___________ _ 49 Igneous rocks of Cenozoic age ___________________ _ 14 Relation of the ore bodies to the enclosing Hornblende andesite and related rocks ________ _ 14 rocks ___________________________________ _ 51 Rhyolite _______________________________ ---- 15 Oxidation of the ores _______________________ _ 52 Rhyolite· tuff ______________________________ _ 16 Mines and mining ______________ ~ __________________ _ 53 Andesite and basalt ________________________ _ 17 Production ____________________________________ _ 56 Sedimentary rocks of Quaternary ·age _____________ _ 17 ~line drainage _________________________________ _ 57 Alluvium ______________________________ ---- 17 Notes on the mines ____________________________ _ 61 Geologic structure _________________________________ _ 18 Adams. Hill area ___________________________ _ 63 Prospect Ridge block ___________________________ _ 19 Ruby Hill area ____________________________ _ 65 Diamond tunnel thrust zone ________________ _ 19 Prospect Ridge group ______________________ _ 67 Ruby Hill thrust zone ______________________ _ 19 Dunderberg-Windfall belt ___________________ _ 70 Dugout tunnel thrust zone __________________ _ 20 Lower New York Canyon group _____________ _ 71 Silver Connor transverse fault_ ______________ _ 21. Other properties ___ .____ ·____________________ _ 71 Jackson-Lawton-Bowman normal-fault system __ 22 References cited ___________________________________ _ 72 Ruby Hill normal fault _____________________ _ 23 Index_~------------------------------------------- 75 ILLUSTRATIONS [Plates are in map volume] PLATE 1. Geolqgic map of the Eureka mining district, Nevada. 2. Geologic sections of the Eureka mining district, Nevada. 3. Geologic structure map of the Eureka mining district, Nevada. UI IV CONTENTS PLATE 4. Horizontal projection of stopes in Ruby Hill mines. 5. Patented claims within the part ofT. 19 N., R. 53 E., included in plate 1, and certain of the unpatented claims in the northern and western parts of the Eureka mining district. 6. Mine workings in the Adams Hill area for which maps are available. 7. Mine workings in the Ruby Hill area for which maps are available (in three sheets). 8. Location of drill holes intersecting sulfide ore in relation to the Fad and Locan shafts. 9. Mine workings in the Prospect Ridge area for which maps _are available. 10. Mine workings in the vicinity of the new ore shoots in the No. 1 shaft area, Diamond mine, Consolidated Eureka Mining Co. 11. Mine workings in the Dunderberg-Windfall belt for which maps are available. Page FIGURE 1. Geologic map of the Dead broke tunnel, illustrating the occurrence of mineralized pods_____________________ 32 2. Section in a plane N. 53° E. through the Eureka Croesus mine, showingthe pipelike habit of the ore shoots______ 33 3. Vertical section through the Lawton shaft, showing ore bodies in the Eldorado dolomite______________________ 34 4. Map of a part of the Diamond tunnel and 120-foot levels________________________________________________ 35 5. Longitudinal projection in a plane N. 10° E. of ore bodies associated with open caves, Diamond mine__________ 36 6. Section looking north, Holly mine, showing localization of stoped areas at intersection of favorable limestone beds and steeply dipping fractures__________________________________________________________________ 37 l 7. Map of the Wabash tunnel, showing stopes of fault-zone replacement bodies in Eldorado dolomite_____________ 38 8. Vertical north-south section of Windfall mine with approximate projection of main stopes_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 40 9. Map of the Rogers tunneL__________________________________________________________________________ 41 10. Polished surface of sulfide ore from the 1006- 1 W stope above the 1,050-foot level, T. L. shaft________________ 44 11. Thin section of oxidized ore from 1002-1 W stope above 1,050-foot level, T. L. shaft________________________ 45 12. Cerussite crystals in quartz matrix. Thin section of oxidized ore from 901-2 E stope above 950-foot level, T. L. shaft ______________________________ -------------------------------------------------------------- 45 13. Fine-grained mimetite in quartz: Thin section of oxidized ore from 809-14 E stope above 850-foot level, T. L. shaft-------------------------------------------------------------------------------------~------ 46 14: Rate of pumping from the T. L. shaft (Aug. 16, 1954-June 30, 1957) and changes in level of ground water in diamond-drill holes 104 (Feb. 14, 1955-June 30, 1957) and 106 (Feb. 14, 1955-June 30, 1957)_______________ 62 15. Map of Lower Dugout tunnels _________________________________________________________ ~~____________ 72 TABLES Page TABLE 1. Geologic formations present in the Eureka Mining district_______________________________________________ 4 2. Available data on annual production of the Eureka Mining district, 1866-1959_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 58 THE EUREKA MINING DISTRICT, NEVADA By THOl\fAS B. NOLAN ABSTRACT to be responsible for an uplift of the ridge of approximately 2,000 feet. The Eureka Mining district lies south and west of the town The small scale, minor irregularities, and lack of continuity of Eureka, county seat of Eureka County, 'in central Nevada. of most of the pre-Basin-Range fault structures suggest that Ore was discovered in the district in 1864, and the peak pro these features developed near the surface, and under a very duction was reached in the 20 years from 1870 to 1890. Since light confining load. They contrast markedly with the major that time production has varied considerably from year to Roberts Mountain thrust zone, which is exposed just west of year, reflecting periods of renewed or expanded programs of the district and which is believed to have a minimum dis exploration and development. placement of 50 miles. The Eureka structural features are The rock