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E-146,701 C St. Maps For maps, address mail orders to U.S. Geological Survey, Map Distribution Maps Federal Center, Box 25286 Maps may be purchased over the counter at the U.S. Geologi­ Denver, CO 80225 cal Survey offices where books are sold (all addresses in above list) and at the following Geological Survey offices: Residents of Alaska may order maps from ROLLA, Missouri-1400 Independence Rd. Alaska Distribution Section, U.S. Geological Survey, DENVER, Colorado-Map Distribution, Bldg. 810, Federal New Federal Building - Box 12 Center 101 Twelfth Ave., Fairbanks, AK 99701 FAIRBANKS, Alaska-New Federal Bldg., 101 Twelfth Ave. Chapter B Mineral Resources of the Gibraltar Mountain and Planet Peak Wilderness Study Areas, La Paz County, Arizona By ROBERT G. EPPINGER, JOCELYN A. PETERSON, H. RICHARD BLANK, JR., K. ERIC LIVO, DANIEL H. KNEPPER, JR., and JAMES A. PITKIN U.S. Geological Survey JON E. SPENCER, STEPHEN J. REYNOLDS, and MICHAEL J.GRUBENSKY Arizona Geological Survey TERRY J. KREIDLER and DAVID C. SCOTT U.S. Bureau of Mines U.S. GEOLOGICAL SURVEY BULLETIN 1704 MINERAL RESOURCES OF WILDERNESS STUDY AREAS: HAVASU REGION, ARIZONA U.S. DEPARTMENT OF THE INTERIOR MANUEL LUJAN, JR., Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1990 For sale by the Books and Open-File Reports Section U.S. Geological Survey Federal Center, Box 25425 Denver, CO 80225 Library of Congress Cataloging-in-Publication Data Mineral resources of the Gibraltar Mountain and Planet Peak wilderness study areas, La Paz County, Arizona / by Robert G. Eppinger ... [et al.]. p. cm. (Mineral resources of wilderness study areas Havasu region, Arizona : ch. B) (U.S. Geological Survey bulletin : 1704-B) Includes bibliographical references. Supt. of Docs, no.: I 19.3: 1704-B 1. Mines and mineral resources Arizona Gibraltar Mountain Wilderness. 2. Mines and mineral resources Arizona Planet Peak Wilderness. 3. Gibraltar Mountain Wilderness (Ariz.) 4. Planet Peak Wilderness (Ariz.) I. Eppinger, R.G. II. Series. III. Series: U.S. Geological Survey bulletin ; 1704-B QE75.B9 no. 1704-B 557.3 s dc20 90-13943 [TN24.A6] [553' .0979172] CIP STUDIES RELATED TO WILDERNESS Bureau of Land Management Wilderness Study Areas The Federal Land Policy and Management Act (Public Law 94-579, October 21,1976) requires the U.S. Geological Survey and the U.S. Bureau of Mines to conduct mineral surveys on certain areas to determine the mineral values, if any, that may be present. Results must be made available to the public and be submitted to the President and the Congress. This report presents the results of a mineral survey of parts of the Gibraltar Mountain (AZ-050-012) and Planet Peak (AZ-050-013) Wilderness Study Areas, La Paz County, Arizona. CONTENTS Summary Bl Abstract Bl Character and setting B1 Identified resources and mineral resource potential of the Gibraltar Mountain Wilderness S tudy Area B3 Identified resources and mineral resource potential of the Planet Peak Wilderness Study Area B3 Introduction B3 Character and setting B3 Previous investigations B6 Present study B6 Acknowledgments B6 Appraisal of identified resources of the Gibraltar Mountain Wilderness Study Area B6 Methods of investigation B6 Mining districts and history B6 Appraisal of sites examined B7 Mammon mine area B7 Gray Eagle mine area B7 Giers Mountain area B7 Miscellaneous prospects B8 Sand and gravel B8 Conclusions B8 Appraisal of identified resources of the Planet Peak Wilderness Study Area B8 Methods of investigation B8 Mining history B8 Appraisal of sites examined B8 Pride mine area B8 Planet Peak claim area B9 Squaw Peak area B10 Sand and gravel BIO Energy resources BIO Comparison of study area to Copperstone mine B10 Conclusions BIO Assessment of mineral resource potential B11 Geology fill Regional setting B11 Local geology B12 Lower-plate rocks B12 Upper-plate rocks B12 Postdetachment rocks B13 Geochemistry B13 Introduction B13 Methods B13 Results B14 Interpretation B18 Geophysics B19 Aeromagnetic and gravity data B19 Landsat thematic mapper images and interpretation B20 Background B20 Interpretive methods B21 Contents Assessment of mineral resource potential Continued Geophysics Continued Landsat thematic mapper images and interpretation Continued Possible areas of hydrothermally altered rocks B22 Aerial gamma-ray spectrometry B22 General discussion of mineral and energy resources B24 Deposits near detachment faults B24 Energy resources B25 Mineral and energy resources of the Gibraltar Mountain Wilderness Study Area B25 Mineral and energy resources of the Planet Peak Wilderness Study Area B26 References cited B26 Appendixes B29 Definition of levels of mineral resource potential and certainty of assessment B30 Resource/reserve classification B31 Geologic time chart B32 FIGURES 1. Index map showing location of Gibraltar Mountain and Planet Peak Wilderness Study Areas, Arizona B2 2. Map showing mineral resource potential and generalized geology of Gibraltar Mountain Wilderness Study Area, Arizona B4 3. Map showing mineral resource potential and generalized geology of Planet Peak Wilderness Study Area, Arizona B5 4. Map showing stream drainages having geochemical anomalies in and near Gibraltar Mountain Wilderness Study Area, Arizona B16 5. Map showing stream drainages having geochemical anomalies in and near Planet Peak Wilderness Study Area, Arizona BIT 6. Residual total-intensity aeromagnetic map of region including Gibraltar Mountain and Planet Peak Wilderness S tudy Areas, California and Arizona B20 7. Complete-Bouguer gravity anomaly map of region including Gibraltar Mountain and Planet Peak Wilderness Study Areas, California and Arizona B21 8. Map showing distribution of potentially hydrothermally altered rocks in Gibraltar Mountain Wilderness Study Area, Arizona; based on remote-sensing interpretation B23 9. Map showing distribution of potentially hydrothermally altered rocks in Planet Peak Wilderness Study Area, Arizona; based on remote-sensing interpretation B24 TABLES 1. Summary of production data for mining districts in and near the Planet Peak Wilderness Study Area, Arizona B9 2. Comparison of geochemical data from the Planet Peak Wilderness Study Area and the Copperstone mine, Arizona B11 3. Summary statistics for anomalous elements from stream sediments and heavy-mineral concentrates in and