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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 K Mineral Resources of the Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona By DAVID R. SHERROD, DAVID B. SMITH, and M. DEAN KLEINKOPF U.S. Geological Survey DIANN D. GESE U.S. Bureau of Mines U.S. GEOLOGICAL SURVEY BULLETIN 1702 ' MINERAL RESOURCES OF WILDERNESS STUDY AREAS: SOUTHWESTERN AND SOUTH-CENTRAL ARIZONA 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 Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona / by David R. Sherrod... [et at.]. p. cm. (U.S. Geological Survey bulletin : 1702-K) Includes bibliographical references, (p. Supt. of Docs, no.: 119.3: 1702-K 1. Mines and mineral resources Arizona Kofa Unit 4 North Wilderness. 2. Kofa Unit 4 North Wilderness (Ariz.) I. Sherrod, David R. II. Series. QE75.B9 no. 1702-K 557.3 s dc20 90-3797 [TN24.A6] [553 1 .0979171] 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 of certain areas to determine the mineral values, if any, that may be present. Results must be made available to the public and submitted to the President and the Congress. This report presents the results of a mineral survey of the Kofa Unit 4 North Wilderness Study Area (AZ-050-033), Yuma County, Arizona. CONTENTS Summary Kl Abstract Kl Character and setting Kl Identified resources Kl Mineral and energy resource potential Kl Introduction K2 Location, physiography, and access K2 Present investigation K2 Appraisal of identified resources K2 Setting K2 Mining and leasing activity K2 Methods of investigation K2 Results K3 Assessment of mineral and energy resource potential K4 Geology K4 Geochemical studies K4 Methods of investigation K4 Summary of results K5 Geophysical studies K5 Mineral and energy resources K6 Gold, silver, lead, and zinc K6 Zeolites K6 Geothermal energy K6 Other commodities K7 References cited K7 Appendixes Definition of levels of mineral resource potential and certainty of assessment K10 Resource/reserve classification Kll Geologic time chart K12 » FIGURES 1. Index map showing location of Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona K3 2. Map showing mineral resource potential and generalized geology of Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona K4 3. Bouguer gravity anomaly map of region including Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona K5 4. Total intensity aeromagnetic anomaly map of region including Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona K6 Contents Mineral Resources of the Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona By David R. Sherrod, David B. Smith, and M. Dean Kleinkopf U.S. Geological Survey Diann D. Cese U.S. Bureau of Mines Yuma County, about 60 mi northeast of Yuma, Ariz. The SUMMARY Castle Dome Mountains are a rocky desert mountain range having relief as great as 2,000 ft. In the study area the Abstract relief is a little less than 700 ft. The mountains are under­ lain by Tertiary volcanic rocks that underwent a major The Kofa Unit 4 North Wilderness Study Area episode of extensional deformation about 22 to 20 million (AZ-050-033) is located in Yuma County, southwestern years ago (see geologic time chart in "Appendixes"). Arizona. At the request of the U.S. Bureau of Land Management, 1,380 acres of the Kofa Unit 4 North Sedimentary basins that bound the range were created Wilderness Study Area were evaluated for mineral resources during this time and subsequently filled by coalescing allu­ (known) and mineral resource potential (undiscovered). vial fans. Throughout this report, reference to the "Kofa Unit 4 North Wilderness Study Area" or to the "study area" refers only to that part of the wilderness study area for which mineral Identified Resources surveys were requested by the U.S. Bureau of Land Management. The study area has inferred subeconomic resources Inferred subeconomic resources of zeolite are scattered throughout the west half of the study area. Large amounts of of approximately 733,000 short tons (st) of 60- to 98-per­ sand and gravel in the study area have no unique qualities cent combined zeolites (mordenite and clinoptilolite). that make them more valuable than vast quantities in the Tests for this study show that these zeolites may have surrounding areas. The entire study area has low mineral commercial value as water purifiers. Zeolites have been resource potential for gold, silver, lead, and zinc, presumably mined approximately 1,500 ft west of the study area bound­ associated with minor alteration along faults. Resource ary. Sand and gravel in the study area have no unique potential for zeolite ranges from high to unknown and is qualities that make them more valuable than those that are spotty in distribution because of localized zeolitization in closer to markets in surrounding areas. altered tuff. Low resource potential for geothermal energy exists northwest of the range-bounding faults of the study area. The study area has no resource potential for oil or gas. Mineral and Energy Resource Potential Low resource potential for gold, silver, lead, and Character and Setting zinc is assigned to the entire Kofa Unit 4 North Wilderness Study Area. A high resource potential for zeolite is as­ The Kofa Unit 4 North Wilderness Study Area is in signed to three small areas adjacent to demonstrated zeolite the northwestern part of the Castle Dome Mountains of occurrences, and an unknown resource potential for zeolite is assigned to other areas underlain by silicic lava flows or Manuscript approved for publication, April 29,1990. intrusions, which may include locally zeolitized, thin, inter- Mineral Resources of the Kofa Unit 4 North Wilderness Study Area, Yuma County, Arizona K1 bedded lenses of tuffaceous rocks.