Geology of the Thomas Range Fluorspar District Juab County, Utah GEOLOGICAL SURVEY BULLETIN 1069 This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission Geology of the Thomas Range Fluorspar District Juab County, Utah By M. H. STAATZ and F. W. OSTERWALD GEOLOGICAL SURVEY BULLETIN 1069 This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Commission UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON j 1959 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director The U. S. Geological Survey Library has cataloged this publication as follows: Staatz, Mortimer Hay, 1918- Geology of the Thomas Range fluorspar district, Juab County, Utah, by M. H. Staatz and F. W. Osterwald. Wash­ ington, U. S. Govt. Print. Off., 1959. v, 97 p. maps (part fold., part col.) diagrs., tables. 24 cm. (CU. S.j Geological Survey. Bulletin 1069) "This report concerns work done on behalf of the U. S. Atomic Energy Commission and is published with the permission of the Com­ mission." Bibliography: p. 91-93. 1. Geology Utah Juab Co. 2. Fluorspar. i. Osterwald, Frank W., joint author. 11. Title: Thomas Range fluorspar district, Juab Co., Utah. (Series) OE75.B9 no. 1069 557.9244 GS 59-153 Copy 2. QE170. J8S8 For sale by the Superintendent of Documents, U. S. Government Printing OfiBce Washington 25, D. C. CONTENTS (Page Abstract.. __.____________________ .._________-_..._._.. 1 Introduction. ___________________________.-__--____.-_- ._. 2 Scope of report________________.__-__--_----_--_--_-_-__---__ 2 Location and surface features______-_-__--_---__-_-----_-------- 2 History and production___________________________-_-__________ 5 Previous work__________________________________ _________ 6 Fieldwork and acknowledgments________-____-___-_-__-___--_-_. 7 Geology _. __ - 8 Sedimentary rocks._______-_______-_---___---__-------_-_----_- 9 Rocks of Ordovician age____..______-___-_--__-_____ 9 Garden City formation.._______________________________ 9* Swan Peak formation._________________________________ 13 Shale member___________---__----_-_---_--_-_-____ 14 Quartzite member____________._-___.___.__________ 16 Fish Haven dolomite________-_-_____--_--_____-______ 17 Rocks of Ordovician or Silurian age____________--____________ 21 Floride dolomite______.___ _______________________ 21 Rocks of Silurian age_____.____ _________________________ 22 Bell Hill dolomite...._______.____..---__ r _____ 23 Harrisite dolomite-__--_____---_-----_.________________ 25 Lost Sheep dolomite.________--__---______-----___-____ 26 Thursday dolomite-_--_-_-_---_-----_-_-_-----________ 28 Rocks of Devonian age____-___-___-_-_-_-__-----__.______ 29 Sevy dolomite_______________________________________ 29 Simonson and Guilmette formations, undivided..__________ 31 Rocks of Quaternary age.--_________-_.-_____._--_-___-____ 32 Lake Bonneville beds..--.-.....-.----.____.--__.______ 32 Volcanic rocks________________________________________________ 34 Classification__ _________________________________________ 34 Petrography ______________________________________________ 35 Enstatite-augite latite________________________________ 35 Hypersthene latite_--___-__________--___-__---_________ 36 Silicic igneous rocks__--_________-_--____-_---__________ 36 Intrusive breccia______________________________________ 37 Pyroclastic rocks_______._______-_____-________________ 38 Petrology_____ __ _______ __ _______. 40 Chemical composition.of rhyolites_--_-________._________ 40 Petrogenesis___-_______________--_--_____-__-_________ 41 Structure.--__-__-_-__-____--_--_-__--_--_------__---__-__________ 42 Folding. __________________;__________________ 42 Faulting________________-__-__-___-_-__.-__--_-______ 43 Thrusts, _______________.-_______-.________________ 43 Northeast-trending normal and reverse faults_________________ 43 Northwest-trending faults.____-______-_--_-----__-__.______ 44 North-trending faults._____________________________________ 44 East-trending faults_____________________________________ 44 Age of faulting_____________.-__-_____---_._____________ 45 Mechanics of faulting___________________.__________________ 45 m IV CONTENTS Page Ore deposits.__-__________________________________!_______________ 46 Types of deposits____________________________________________ 46 Pipelike bodies.___________________________________________ 46 Veins.__ _____________________________________________ 47 Disseminated deposits_-'_--___-____-______--____-____.____ 47 Structural control _____________________________________________ 48 Character of ore___--_-_-___--_-_-_______________________l_____ 49 Uranium mineralization ________________________________________ 52 Origin__ ____________________________________________________ 59 Descriptions of individual deposits___-___-________--_-___.____-_____ 62 Bell Hill..._____________________________________________ 62 Blowout________-_-__-_-_-_--------_-----_--------_-----__ 70 BlueQueenNo. 1.........._...._____ ..._..... __--_----_- 72 Fluorine Queen______________________________________________ 72 Fluorine Queen No. 4_-____-___-_____-_--_-_-----_____--__-_-_- 76 Harrisite _______-_______________-__-_________-_------_-_--_-__ 76 Hilltop No. !________________________.___-._____ 80 Lost Sheep___________________________________________________ 81 Main pipe.____________-______.________-_-_---______--__ 82 South pipe______________________________________________ 83 Lost Soul No. !________________________-___---_-_-_---_._-_- 84 Lucky Louie._________________________________________________ 84 Oversight__ _________________________________________________ 85 Unnamed adit____________-__-__.__________-____-_----_-_-_- 88 Deposits in tuff.______________________________________________ 89 Deposit 1____________________________________--___-__ 90 Deposit 2_________ _ _______________________ 90 Rainbow No. 2______________________________________ 90 Literature cited.__________________________________________________ 91 Index._________________________________________________________ 95 ILLUSTRATIONS Page [Plates 1-4 and 9-12 are in pocket] PLAT* 1. Geologic map of fluorspar district. 2. Structure sections of fluorspar district. 3. Geologic map of south end, Spors Mountain. 4. Geologic map of Eagle Rock Ridge. 5. A, Fish Haven dolomite, along canyon; B, Bell Hill dolo- mite__ _ _______.__;.___.__________________Face§ 10 6. Horn corals from bed near base of Bell Hill dolomite_ .Face* 11 7. A, Harrisite dolomite, with Halysites; B, Tuff, 168-foot level, Bell Hill___________________________Faces 26 8. A, Fault pattern north of Dell; B, Fault traces southwest of Blowout...____._.___________________-_._____Faces 27 9. Map of the Bell Hill ore body. 10. Geologic sections of Bell Hill property. 11. Map and sections of Blowout property. 12. Map and section, east pit, Fluorine Queen property. CONTENTS V Page FIGURE 1. Index map, Thomas Range------------------------------- 3 2. Generalized stratigraphic sections of the Fish Haven, Floride, Bell Hill, Harrisite, Lost Sheep, and Thursday dolomites.__ 19 3. Depth and uranium-content relations in Bell Hill mine______- 57 4. Underground maps of Bell Hill mine__-_-_-____-_____---__- 64 5. Block diagram showing the shape of the large pipe on the Bell Hill property._____________________________- 67 6. Underground maps of Blue Queen no. 1 and Lost Soul no. 1 mines._______________________________________________ 73 7. Map of Fluorine Queen no. 4._______.___-----_---________ 77 8. Diagrammatic section of fluorspar bodies, Harrisite property__ 78 9. Maps of Lost Sheep property.__-____.____________________ 82 10. Block diagram of Lucky Louie pipe-____________________.-- 86 11. Map of adit southeast of Thursday prospect________________ 89 TABLES Page TABLE 1. Distribution of the total production of 75,312 short tons of fluorspar mined in the Thomas Range district, 1944-52___ . 5 2. Stratigraphic section of the Garden City formation.__________ 10 3. Lime and magnesia content of limestone and dolomite from Spors Mountain._______________________________________ 12 4. Stratigraphic section of upper part of shale member of the Swan Peak formation._______________________________________ 15 5. Stratigraphic section of the Se vy dolomite ___________________ 31 6. Stratigraphic section of the Simonson and Guilmette forma­ tions, undivided._______________________________________ 33 7. Chemical composition in weight percent of Thomas Range rocks. 40 8. Analyses of samples from the Thomas Range fluorspar district. 54 GEOLOGY "OF THE THOMAS RANGE FLUORSPAR DISTRICT, JUAB COUNTY, UTAH By M. H. STAATZ and F. W. OSTERWALD ABSTRACT The Thomas Range fluorspar district is an area of about 34 square miles surrounding Spors Mountain in central .Tuab County, 46 miles northwest of Delta, Utah. From its discovery in 1943 to the end of 1952, 12 properties in this district yielded a total of 75,312 short tons of fluorspar. Almost all the fluorspar deposits have an abnormally high uranium content. All but 1 of the 7 fluorspar veins and pipes that contained over 0.050 percent uranium are on the southern end of Spors Mountain. The exposed rocks range in age from Early Ordovician to Pleistocene. The greater part of Spors Mountain is made up of a thick sequence of apparently conformable Paleozoic rocks, which are chiefly carbonates. The Garden City formation, of Ordovician age which is chiefly