U.S. DEPARTMENT OF THE INTERIOR U. S. GEOLOGICAL SURVEY Evaluation of selected metallic and nonmetallic mineral resources, West Mojave Management Area, southern California by U.S. Geological Survey1 December 1992 U.S. GEOLOGICAL SURVEY OPEN-FILE REPORT 92-595 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, products or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. J Menlo Park, California 94025 CONTENTS Page Executive summary................................................................................................................ 1 Summary................................................................................................................................ 2 Introduction............................................................................................................................ 9 Procedures for delineating permissive terranes ...................................................................... 11 Procedures for quantitative estimates of undiscovered mineral resources ............................. 18 Mineral resources of the West Mojave Management Area .................................................... 25 Epithermal precious-metal system ................................................................................... 25 Gold-rich types........................................................................................................... 25 Quartz-alunite gold.............................................................................................. 27 Quartz-adularia.................................................................................................... 30 Silver- and barite-rich types ...................................................................................... 37 Base- and precious-metal deposits ............................................................................ 38 Other epithermal precious metal systems with no delineated permissive terranes ... 39 Polymetallic systems....................................................................................................... 40 Polymetallic replacement deposits ............................................................................ 41 Polymetallic veins..................................................................................................... 41 Tungsten veins.......................................................................................................... 45 Tungsten veins-Atolia type ....................................................................................... 49 Tungsten and base-metal skarns ..................................................................................... 50 Tungsten skarns........................................................................................................ 50 Base-metal skarns..................................................................................................... 51 Iron skarn........................................................................................................................ 55 Porphyry copper............................................................................................................. 59 Jurassic porphyry copper deposits ........................................................................... 60 Tertiary porphyry copper deposits ........................................................................... 66 Porphyry gold deposits ............................................................................................ 66 Evaporite and saline deposits ........................................................................................ 68 Borate deposits........................................................................................................ 68 Salines...................................................................................................................... 73 Zeolite and hectoritic clays ............................................................................................ 74 Estimate of total endowment.......................................................................................... 75 Nature of distributions .............................................................................................. 76 Alternative presentations.......................................................................................... 76 Meaning of estimates ................................................................................................ 77 References............................................................................................................................. 81 TABLES 1 A. Ore deposit model and grade and tonnage models applicable to the West Mojave Management Area.................................................................................................. 5 IB. Ore deposits in the West Mojave Management Area for which a permissive terrane was delineated but for which descriptive, grade, and tonnage models are not available 6 1C. Mineral deposits and other resources in the West Mojave Management Area for which permissive terranes were not delineated................................................................. 6 2. Probabilistic estimates of the minimum numbers of undiscovered mineral deposits in the West Mojave Management Area ............................................................................ 7 3. Mean and median estimated metal endowment for selected metallic and nonmetallic mineral deposits..................................................................................................... 8 4. Mean and median estimated metal endowment for all metallic and nonmetallic deposit types evaluated in the West Mojave Management Area....................................... 9 11 FIGURES 1. Location map of the West Mojave Management Area, southern California ............ 4 2A Geochemical sample location map for rocks in the West Mojave Management Area, southern California............................................................................................... 16 2A Geochemical sample location map for stream sediment and heavy-mineral concentrate samples in the West Mojave Management Area, southern California................. 17 3. Graph showing probabilistic estimates for the amount of gold in individual deposit types, and in all deposit types ......................................................................................... 22 4. Permissive terrane for epithermal precious metal systems in the West Mojave Management Area..................................................................................................................... 26 5A. Graph showing probabilistic estimates for the amount of gold, silver, and copper in quartz- alunite gold deposits in terrane II........................................................................ 31 5B. Graph showing probabilistic estimates for the amount of gold, silver, and copper in quartz- alunite gold deposits in terranes I and III............................................................ 32 6. Graph showing probabilistic estimates for the amount of gold, silver, copper, lead, and zinc in Sado-type deposits in terrane I................................................................ 35 7. Graph showing probabilistic estimates for the amount of gold and silver in hot spring-type deposits................................................................................................................ 36 8. Permissive terranes for Jurassic and Cretaceous polymetallic vein districts and Jurassic porphyry copper deposits in the West Mojave Management Area..................... 43 9. Graph showing probabilistic estimates for the amount of gold, silver, copper, lead, and zinc in polymetallic vein systems of Jurassic age ............................................... 46 10. Graph showing probabilistic estimates for the amount of gold, silver, copper, lead, and zinc in polymetallic vein systems of Cretaceous age ........................................... 47 11. Graph showing probabilistic estimates for the amount of tungsten in vein and skarn deposits................................................................................................................ 48 12. Permissive terrane for iron, base metal, and tungsten skam deposits in the West Mojave Management Area............................................................................................... 52 13. Graph showing probabilistic estimates for the amount of copper, gold, and silver in copper skarn deposits...................................................................................................... 53 14. Graph showing probabilistic estimates for the amount of zinc, lead, copper, gold, and silver in zinc-lead skarn deposits ........................................................................ 54 15. Graph showing probabilistic estimates for the amount of iron in iron skarn deposits 58 16A. Graph showing probabilistic estimates for the amount of copper, molybdenum, gold, and silver in porphyry copper deposits of Jurassic age in the Ord Mountains area... 64 in 16B. Graph showing probabilistic estimates for the amount of copper, molybdenum, gold, and silver in porphyry copper deposits of Jurassic age in the Pinto Mountains area.. 65 17. Graph showing probabilistic estimates for the amount of