Mineral Resources of the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California U.S. GEOLOGICAL SURVEY BULLETIN 1711-A Chapter A Mineral Resources of the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California By DAVID B. SMITH, BYRON R. BERGER, RICHARD M. TOSDAL, DAVID R. SHERROD, GARY L. RAINES, ANDREW GRISCOM, and MARYANN G. HELFERTY U.S. Geological Survey CLAYTON M. RUMSEY and AREL B. McMAHAN U.S. Bureau of Mines U.S. GEOLOGICAL SURVEY BULLETIN 1711 MINERAL RESOURCES OF WILDERNESS STUDY AREAS: SOUTHERN CALIFORNIA AND CALIFORNIA DESERT CONSERVATION AREA DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1987 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 Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California. U.S. Geological Survey Bulletin 1711-A Bibliography Supt. of Docs. No.: I19.3:1711-A 1. Mines and mineral resources California Indian Pass Wilderness. 2. Mines and mineral resources California Picacho Peak Wilderness. 3. Indian Pass Wilderness (Calif.) 4. Picacho Peak Wilderness (Calif.) I. Smith, David B. (David Burl), 1948- . II. Series: Geological Survey Bulletin 1711-A. QE75.B9 No. 1711-A 557.3 s 86-607943 [TN24.C2] [553'.09794'99] 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 part of the Indian Pass (CDCA-355) Wilderness Study Area and part of the Picacho Peak (CDCA-355A) Wilderness Study Area, Imperial County, California. CONTENTS Summary Al Abstract 1 Character and setting 1 Identified resources 1 Mineral resource potential 3 Introduction 3 Acknowledgments 3 Appraisal of identified resources and known mineralized areas 5 Mining history 5 Mines, prospects, and mineralized outcrops 5 Mineralized zone along the Chocolate Mountains thrust fault 6 Conclusions 6 Assessment of potential for undiscovered resources 6 Geologic setting 6 Geochemistry 7 Summary of results 7 Remote sensing 9 Geophysical studies 10 Mineral resource potential of the Indian Pass Wilderness Study Area 10 Gneiss-hosted disseminated gold 10 Epithermal gold and silver 12 Skarn tungsten 12 Vein copper 12 Volcanogenic massive sulfide and gold 12 Mineral resource potential of the Picacho Peak Wilderness Study Area 12 Gneiss-hosted disseminated gold 13 Vein copper 13 Volcanogenic massive sulfide and gold 13 References cited 13 Appendix 1. Definition of levels of mineral resource potential and certainty of assessment and geologic time scale 20 PLATE In pocket 1. Mineral resource potential map of the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California FIGURES 1. Index map showing location of Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California A2 2. Map showing mineral resource potential and generalized geology of the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California 4 3. Map showing distribution of selected elements in nonmagnetic heavy-mineral concentrates derived from stream sediments collected in the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California 8 4. Map showing anomalous limonitic areas in the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California 11 TABLES 1. Mines, prospects, and mineralized outcrops in and adjacent to the Indian Pass and Picacho Peak Wilderness Study Areas A15 2. Summary of analyses for 12 elements in 89 samples of nonmagnetic heavy-mineral concentrates 18 3. Analyses of selected rock samples 19 MINERAL RESOURCES OF WILDERNESS STUDY AREAS: SOUTHERN CALIFORNIA AND CALIFORNIA DESERT CONSERVATION AREA Mineral Resources of the Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California By David B. Smith, Byron R. Berger, Richard M. Tosdal, David R. Sherrod, Gary L. Raines, Andrew Griscom, and Maryann G. Helferty U.S. Geological Survey Clayton M. Rumsey and Arel B. McMahan U.S. Bureau of Mines SUMMARY (fig. 1). The relief is about 1,800 ft with rugged hills, steep-walled arroyos, and broad sandy washes. Abstract The study areas are underlain by rocks ranging in age from Proterozoic(?) and Mesozoic to Quaternary At the request of the Bureau of Land (see appendix 1 for geologic time chart). The Management, the U.S. Geological Survey and U.S. structurally lowest rocks in the study areas are Bureau of Mines studied the Indian Pass (CDCA-355) Proterozoic(?) and Mesozoic gneiss and Jurassic(?) Wilderness Study Area and the Picacho Peak (CDCA- supracrustal and granitic rocks that have been 355 A) Wilderness Study Area in eastern Imperial superposed over the late Mesozoic Orocopia Schist County, Calif. Mineral surveys were conducted on along the Late Cretaceous Chocolate Mountains 33,640 acres of the Indian Pass Wilderness Study Area thrust. Weakly to moderately metamorphosed and 5,450 acres of the Picacho Peak Wilderness Study Jurassic(?) supracrustal and granitic rocks are also Area. Field work for this report was carried out juxtaposed against the gneiss and Orocopia Schist between 1982 and 1985. along younger normal faults. At Peter Kane Mountain, Within the collective area of the two study the Orocopia Schist was intruded and thermally areas, there were 344 active mining claims in 1982. remetamorphosed by a pluton at about 21-26 million The prospects visited and sampled within and adjacent years before the present (Ma). Block faulting in to the Indian Pass Wilderness Study Area have no Oligocene time was followed by silicic volcanism, identified resources. However, a tract having high which continued into early Miocene time. Regional resource potential for gold was delineated in the extension followed soon after the cessation of southwestern part of the Indian Pass Wilderness Study volcanism. Conglomerate marks the erosion of the Area. This tract has been the site of much exploration volcanic field. Latest Tertiary(?) and Quaternary activity for gold since 1983. Other tracts located conglomerate, sandstone, and siltstone unconformably within the Indian Pass Wilderness Study Area have overlie the older rocks and structures. moderate resource potential for gold and silver, California's earliest mineral production (worked moderate potential for tungsten, and low potential for in 1779-81 by Spanish miners) was from placer gold gold, lead, zinc, and copper. deposits in the region just south of the study areas. The prospects sampled within and adjacent to the Lode gold deposits at the Picacho mine, approximately Picacho Peak Wilderness Study Area have no identified 5 mi east-southeast of the Picacho Peak Wilderness resources. Tracts having high resource potential for Study Area, and the Cargo Muchacho district, about 10 gold were delineated in the north-central part of the mi south of the study areas (fig. 1), were discovered in Picacho Peak Wilderness Study Area. Other tracts the late 19th century. within the Picacho Peak Wilderness Study Area have low potential for undiscovered gold, lead, zinc, and copper resources. Identified Resources The 37 prospects visited and sampled during this Character and Setting study contained no identified resources. However, our sampling and the recent drilling program by Gold The Indian Pass and Picacho Peak Wilderness Fields Mining Corporation provide strong evidence that Study Areas occupy the southeast end of the Chocolate gold resources exist in the Indian Pass and Picacho Mountains approximately 25 mi north-northwest of Peak Wilderness Study Areas. There has been no Yuma, Ariz., in easternmost Imperial County, Calif. mineral production from the study areas. Al 114°30' 33°15' WILDERNESS STUDY AREA (CDCA-355) PICACHO PEAK ILDERNESS STUDY AREA (CDCA-355A) Cargo Muchacho mining district CALIF) J __JARIZ. UNITED STATES MEXICO Figure 1. Index map showing location of Indian Pass and Picacho Peak Wilderness Study Areas, Imperial County, California. A2 Mineral Resource Potential copper in hydrothermal veins and for gold, lead, zinc, and copper in volcanogenic massive sulfide deposits. The Indian Pass and Picacho Peak Wilderness INTRODUCTION Study Areas each have tracts having high mineral resource potential for gold. The Indian Pass This report presents an assessment of the Wilderness Study Area also has localities with identified resources and the mineral resource potential moderate resource potential for gold and silver, of the Indian Pass (CDCA-355) and Picacho Peak moderate potential for tungsten resources, and low (CDCA-355A) Wilderness Study Areas, Imperial potential for gold, lead, zinc, and copper resources. County, Calif, (fig. 1). The Indian Pass and Picacho The Picacho Peak Wilderness Study Area has localities Peak study areas comprise approximately 33,640 acres with low potential for gold, lead, zinc, and copper and 5,450 acres, respectively. They are located in resources. easternmost Imperial County at the southeast end of The region around the study areas has the Chocolate Mountains and lie about 25 mi north- intermittently produced significant quantities of gold northwest of Yum a, Ariz. Access to the study areas since the mid-1800's and is currently being explored from Yum a is by Interstate Highway 8 west for 13 mi for additional gold resources. Within a 10-mi radius of to the Ogilby Road, north on this road for 12 mi to the the study areas, the Picacho mine is currently Indian Pass graded dirt road, then east for 7 mi to producing gold, the Mesquite deposit produced its first Indian Pass and Gavilan Wash. Access to more remote gold in early 1986, and the Cargo Muchacho district parts of the areas is by unimproved dirt roads, many of (fig.