Uranium Distribution and Geology in the Fish Lake Surficial Uranium Deposit, Esmeralda County, Nevada U.S. GEOLOGICAL SURVEY BULLETIN 1910 AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the cur­ rent-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Sur­ vey publications released prior to the current year are listed in the most recent annual "Price and Availability List" Publications that are listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual"Price and Availability List" are no longer available. 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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, Mlssourl--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. Uranium Distribution and Geology in the Fish Lake Surficial Uranium Deposit, Esmeralda County, Nevada By DAVID L. MACKE, R. RANDALL SCHUMANN, and JAMES K. OTTON Uranium-enriched lacustrine and marsh sediments in the Fish Lake Valley U.S. GEOLOGICAL SURVEY BULLETIN 1910 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: 1990 For sale by the Books and Open-File Reports Section U.S. Geological Survey Federal Center Box 25425 Denver, CO 80225 Ubrary of Congress Cataloging-in-Publication Data Macke, David L. Uranium distribution and geology in the Fish Lake surficial uranium deposit, Esmeralda County, Nevada : uranium-enriched lacustrine and marsh sediments in the Fish Lake Valley I by David L. Macke, R. Randall Schumann, and James K. Otton. p. cm.-(U.S. Geological Survey bulletin; 1910) Includes bibliographical references. Supt. of Docs. no.: I 19.3:1910 1. Uranium ores-Nevada-Fish Lake Watershed. 2. Geology-Nevada-Fish Lake Watershed. 3. Lake sediments­ Nevada-Fish Lake Watershed. I. Schumann, R. Randall. II. Otton, James K. Ill. Title. IV. Series. QE75.B9 no. 1910 [QE370.2.U7) 557.3 s-dc20 [553.4'932'0979335] 89-600369 CIP CONTENTS Abstract 1 Introduction 1 Physiography and climate .2 Regional geology .2 Ground water and springs 3 The Fish Lake surficial uranium deposit 5 Stratigraphy and uranium distribution of the marsh 7 Reconnaissance sampling 11 Results of study 11 Fish Lake marsh 11 Reconnaissance samples 1.2 Summary and conclusions 13 References 13 Appendixes 15 FIGURES 1. Location map of Fish Lake Valley .2 2. Generalized geologic map of the Fish Lake Valley showing water- and sediment-sample localities 4 3. Map of the Fish Lake area showing auger-hole localities and lines of cross sections 5 4. Diagrams showing chemical analyses of spring-water samples from Fish Lake Valley and surrounding mountain ranges 6 5. Cross sections showing stratigraphy and uranium concentrations of the Fish Lake area 8 6. Histograms and scatterplots of uranium content and loss-on-ignition values for samples from the Fish Lake marsh 10 TABLE 1. Summary of results of reconnaissance sampling 11 Contents Ill Uranium Distribution and Geology in the Fish Lake Surficial Uranium Deposit, Esmeralda County, Nevada By David L. Macke, R. Randall Schumann, and James K. Otten Abstract and tropical settings (Otton, 1984a). Uranium-fixation Fish Lake Valley, in southern Nevada and California, mechanisms vary according to the geological setting. The contains about 675 acres of uranium-enriched lacustrine and initial fixation of uranium in wetland surficial uranium marsh sediments in an arid alluvial-fan environment. A deposits is probably by adsorption of U(VI) from ground change in the trend of the Silver Peak Range, which forms or surface water onto organic matter. Organic-rich sedi­ the valley's eastern margin, and bedrock spurs that divert ments are so efficient in trapping uranium that surficial clastic sediments away from the marsh have allowed a large uranium deposits (defined as having uranium concen­ deposit of lacustrine and marsh sediment to accumulate. Section lines across the deposit were sampled at 0.3-m trations greater than 100 ppm; Otton, 1984a) can form intervals to a maximum depth of 6.5 m. All samples were from water containing as little as 5-10 ppb uranium dried and analyzed for uranium and organic matter content. (Otton, 1984a). Modern surficial uranium deposits Uranium concentrations in the sediments ranged from 6 to typically contain very low concentrations of uranium 800 ppm and averaged 64.3 ppm (253 samples). Uranium daughter products. Radiometrically equivalent uranium values correlate with organic content of the samples. The marsh is fed by ground water and surface runoff values (uranium calculated from the radioactivity of its derived from the Silver Peak Range. Tertiary volcanic rocks of decay products) are commonly only 5 to 10 percent of the Silver Peak Range supply uranium to the base of the chemical uranium (R. R. Culbert, written commun., deposit in upwelling ground water. The uranium is con­ 1982). The relative paucity of uranium decay products centrated in organic-rich layers in the marsh sediments. limits the amount of high-energy gamma rays produced Water migrating laterally through the marsh sediments at the by these deposits and, therefore, their detection by edge of the permanent pond in the southern part of the area may also contribute uranium to the sediments. conventional radiometric techniques (Otton, 1984b; Cul­ Reconnaissance sampling in the surrounding valley bert and Leighton, 1981). and mountain areas showed minor enrichment of uranium Surficial uranium deposits pose an environmental (as much as 150 ppm) in wetland areas and localized hazard because the uranium can be remobilized in accumulations of organic-rich sediments. unconsolidated sediments. Ingested from drinking water, uranium is chemically toxic to the kidneys and may also have a finite radiation toxicity (Cothern and others, INTRODUCTION 1983). Many surficial deposits may exist, and more information on the geologic setting and geochemistry of Surficial uranium deposits have been broadly surficial uranium deposits is needed to assess their defined as "uraniferous sediments or soils, commonly of potential impact on public health. Tertiary to Holocene age, that have not been subjected to The surficial uranium deposit in Fish Lake Valley deep burial and may or may not have been cemented to (fig. 1) was first identified in 1982 during reconnaissance some degree" (Toens and Hambleton-Jones, 1984, p. 9). sampling of the Great Basin area (R.R. Culbert, written Surficial uranium deposits occur in wetland, arid-land, commun., 1982). Culbert reported values exceeding 1,500 ppm (analysis by low-energy gamma-ray spec­ trometry). The Fish Lake uranium deposit is significant because it is an organic-rich surficial uranium deposit of Manuscript approved for publication, September 26, 1989. the type normally associated with humid climates (Otton, Introduction 1984a) and is in a geologic and climatic setting where The surface drainages from the northwestern part of the silcrete, calcrete, or pedogenic uranium aCcumulations valley skirt the Volcanic Hills and terminate in the playa are expected to occur (Toens and Hambleton-Jones, lake in the northeastern part.