GJ0-010(81) National Uranium Resource Evaluation MONTROSE QUADRANGLE COLORADO Field Engineering Corporation Grand Junction Operations Grand Junction, CO 81502 Issue Date June 1981 PREPARED FOR THE U.S. DEPARTMENT OF ENERGY Grand Junction Office, Colorado This report is a result of work performed by Bendix Field Engineering Corporation, Operating Contractor for the U.S. Department of Energy, as part of the National Uranium Resource Evaluation. NURE is a program of the U.S. Department of Energy's Grand Junction, Colorado, Office to acquire and compile geologic and other information with which to assess the magnitude and distribution of uranium resources and to determine areas favorable for the occurrence of uranium in the United States. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. For sale by Bendix Field Engineering Corporation Technical Library, P.O. Box 1569 Grand Junction, Colorado 81502 Price $1 0.00 GJQ-010(81) NATIONAL URANIUM RESOURCE EVALUATION MONTROSE QUADRANGLE COLORADO Craig S. Goodknight and John R. Ludlam BENDIX FIELD ENGINEERING CORPORATION Grand Junction Operations Grand Junction, Colorado 81502 June 1981 PREPARED FOR THE U.S. DEPARTMENT OF ENERGY GRAND JUNCTION OFFICE UNDER CONTRACT NO. DE-AC13-76GJ01664 CONTENTS Abstract • 1 Introduction • 3 Purpose and scope • 3 Acknowledgments • 3 Procedures. 3 Surface studies. • 4 Subsurface studies • 5 Geologic setting. 5 Environments favorable for uranium deposits. 10 Summary • 10 Magmatic-hydrothermal uranium deposits. 11 Area A. Marshall Pass uranium district. 13 Area B. Area east and northeast of Gunnison • 17 Subarea 1--Italian Mountain • 18 Subarea 2--Jacks Cabin. 19 Subarea 3--Broncho Mountain • 20 Subarea 4--Whitepine. 21 Subarea 5--Monarch-Garfield • 22 Remainder of Area B • 23 Area C. Cochetopa uranium district. 23 Area D. Northeast part of the Bonanza mining district • 27 Area E. Area north of the Blowout near Ouray. 29 Sandstone-type uranium deposits •• 30 Non-channel-controlled peneconcordant uranium deposits • 30 iii CONTENTS (Continued) Area F Kerber Creek area. 31 Area G. Marshall Pass area * • • 34 35 uranium 36 General uranium deposits J) 39 Hydroauthigenic uranium deposits (Area K) 41 Uranium deposits of uncertain genesis (AreaL). 44 Environments unfavorable for uranium deposits. 47 47 Sedimentary environments. 47 Sandstone environments • 47 Roll-type deposits. 47 gt Peneconcordant deposits • 51 Limestone environments • 52 Marine black shale environments. 53 , coal, and nonmarine carbonaceous shale environments • 55 Plutonic igneous environments • 55 Orthomagmatic environment •• 57 Precambrian intrusive rocks 57 rocks. • 58 rocks • 63 environment • 65 environment. 68 of the Gunnison River area 68 iv CONTENTS (Continued) Fault systems in the Ouray and Ridgway areaso • • • • • • • 69 Fault systems related to the Rio Grande rift zone • • • • • 0 0 • • 0 0 • 0 0 • 0 70 Other fault systems in the quadrangle 0 • • 0 0 0 • • • 70 Radioactive springs along the North Fork of the Gunnison River • • • • • • • 71 Volcanogenic environments • • • • • • • • • • • • • • • • • • • • • • 72 Metamorphic environments. • • • • • • • • • • • • • • • • • • • • • • 73 Unevaluated environments •• • • 0 • • 0 0 • 0 0 • • • • 0 • • • • 0 • • • 74 Subsurface environments 0 • • • • 0 • • • • • • • • • • • 0 • • 0 • • 74 Volcanic environments • • 0 • 0 0 • • • • • 0 • • 0 • • • • 0 0 • • • 76 Recommendations to improve evaluation. • • • • • • • • • • • • • • • • • • 77 Followup of anomalies from hydrogeochemical and stream-sediment and aerial radiometric reconnaissance surveys • • 0 • 77 Radon and radium surveys. • • • • • • • • • • • • • • • • • • • • • • 78 Drilling. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 79 Detailed geologic mapping • • • • • • • • • • • • • • • • • • • • • • 79 Selected bibliography. • • • • • • • • • • • • • • • • • • • • • • • • • • 80 Appendix A. Tables of uranium occurrences (microfiche) Appendix B. Tables of locations and chemical analyses of samples (microfiche) Appendix c. Uranium-occurrence reports (microfiche) Appendix D. Petrographic reports (microfiche) v ILLUSTRATIONS F 6 2 features in area 0 0 0 $ G 0 0 0 8 3. Schematic sectional of a rhyolite porphyry its and chemical relations, and its relation to rocks • • • • • • • . 45 Table 1. Selected results of analyses of rock samples from Harding Sandstone in favorable Areas F, G, and H • • • • • 32 2. Selected results of analyses of rock samples from te bodies related to the Lake . • . • . • . • . • . • . 43 3. List of gamma-ray from USGS coal test drill holes in the of the Grand Mesa coal field within the Montrose Quadrangle. 56 4. Selected results of analyses of representative rock samples from intrusive igneous rocks in the Montrose Quadrangle. • • • • • • • • • • • • • • • • • • 60 5. Some radioactive minerals identified in selected pegmatites in the Montrose Quadrangle using X-ray diffraction and SEM/EDS analyses. • • • • • • • • • • • • • • • 67 6. Selected results of of representative rock ash-flow tuffs in the Montrose . • . 73 7. List of gamma-ray logs from oil and gas test wells in the Montrose Quadrangle. • . • . • . • . 75 Plate la. Areas favorable for uranium s lb. Index to maps of areas favorable for uranium lc. for uranium in the Marshall Pass uranium district ld. Area B: favorable for magmatic-hydrothermal uranium deposits east and northeast of Gunnison vi ILLUSTRATIONS (Continued) Plate lf. Area D: favorable for magmatic-hydrothermal uranium deposits in the northeast part of the Ronanza district lg. Area E: favorable for magmatic-hydrothermal uranium deposits north of the Blowout near Ouray lh. Area F: favorable for uranium deposits in the Harding Sandstone in the Kerber Creek area 1 1.. Area H: favorable for uranium deposits in the Harding Sandstone in the Garfield area lj. Area K: favorable for uranium deposits in late-stage rhyolite bodies related to the Lake City caldera lk. Areas G, I, J, and L favorable for uranium deposits 2. Uranium occurrences 3. Interpretation of aerial radiometric data 4. Interpretation of data from hydrogeochemical and stream-sediment reconnaissance 5. Location map of geochemical samples 6. Drainage 7. Lithologic columns with descriptions of sedimentary, igneous, and metamorphic rocks in the Montrose Quadrangle 8. Location map of gamma-ray logs from oil and gas test wells 9. Geologic-map index 10. Generalized land status 11. Culture Miscellaneous Field Studies Map MF-761: Preliminary Geologic Map of the Montrose 1° x 2° Quadrangle, Southwestern Colorado, compiled by Tweto and others, 1976. Available from Branch of Distribution, U.S. Geological Survey Box 25281, Federal Center, Denver, CO 80225 vii ABSTRACT The Montrose Quadrangle in west-central Colorado was evaluated to iden­ tify and delineate areas favorable for the occurrence of uranium deposits according to National Uranium Resource Evaluation program criteria. General surface reconnaissance and geochemical sampling were conducted in all geologic environments in the quadrangle. Preliminary data from aerial radiometric and hydrogeochemical and stream-sediment reconnaissance were analyzed and brief followup studies were performed. Twelve favorable areas were delineated i.n the quadrangle. Five favorable areas contain environments for magmatic­ hydrothermal uranium deposits along fault zones in the Colorado mineral belt. Five areas in parts of the Harding and Entrada Sandstones and Wasatch and Ohio Creek Formations are favorable environments for sandstone-type uranium depos­ its. The area of late-stage rhyolite bodies related to the Lake City caldera is a favorable environment for hydroauthigenic uranium deposits. One small area is favorable for uranium deposits of uncertain genesis. All near-surface Phanerozoic sedimentary rocks are unfavorable for uranium deposits, except parts of four formations. All near-surface plutonic igneous rocks are unfa­ vorable for uranium deposits, except five areas of vein-type deposits along Tertiary fault zones. All near-surface volcanic rocks, except one area of rhyolite bodies and several unevalua ted areas, are unfavorable for uranium. All near-surface Precambrian metamorphic rocks are unfavorable for uranium de­ posits. Parts of two wilderness areas, two primitive areas, and most of the subsurface environment are unevaluated. 1 INTRODUCTION PURPOSE AND SCOPE The Montrose Quadrangle of the National Topographic Map Series (NTMS), scale 1:250,000, in west-central Colorado was evaluated for geologic environ­ ments favorable for uranium deposits. Geologic environments within the quad­ rangle were categorized as favorable, unfavorable, or unevaluated based on the similarity of their characteristics to the recognition criteria (Mickle and Mathews, eds., 1978) prepared for the National Uranium Resource Evaluation (NURE) program.