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119. 3 :1857-G Gold in Placer Deposits U.S. GEOLOGICAL SURVEY BULLETIN 1857-G 9 0 - 1 8 1 p GEORGIA TECH LIBRARY MAR 2 31990 DOCUME.NIS DEPOSH-ORY COLLECTiON 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. Prices of reports released to the open files are given in the listing "U.S. Geological Survey Open-File Reports," updated month­ ly, which is for sale in microfiche from the U.S. Geological Survey, Books and Open-File Reports Section, Federal Center, Box 25425, Denver, CO 80225. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. Order U.S. Geological Survey publications by mail or over the counter from the offices given below. BY MAIL OVER THE COUNTER Books Books Professional Papers, Bulletins, Water-Supply Papers, Techniques of Water-Resources Investigations, Circulars, publications of general in­ Books of the U.S. Geological Survey are available over the terest (such as leaflets, pamphlets, booklets), single copies of Earthquakes counter at the following Geological Survey Public Inquiries Offices, all & Volcanoes, Preliminary Determination of Epicenters, and some mis­ of which are authorized agents of the Superintendent of Documents: cellaneous reports, including some of the foregoing series that have gone out of print at the Superintendent of Documents, are obtainable by mail from • WASHINGTON, D.C.--Main Interior Bldg., 2600 corridor, 18th and C Sts., NW. U.S. Geological Survey, Books and Open-File Reports • DENVER, Colorado--Federal Bldg., Rm. 169, 1961 Stout St. Federal Center, Box 25425 • LOS ANGELES, California--Federal Bldg., Rm. 7638, 300 N. Denver, CO 80225 Los Angeles St. • MENLO PARK, California--Bldg. 3 (Stop 533), Rm. 3128, Subscriptions to periodicals (Earthquakes & Volcanoes and 345 Middlefield Rd. Preliminary Determination of Epicenters) can be obtained ONLY from • RESTON, Virginia--503 National Center, Rm. 1C402, 12201 the Sunrise Valley Dr. • SALT LAKE CITY, Utah--Federal Bldg., Rm. 8105, 125 Superintendent of Documents South State St. Government Printing Office • SAN FRANCISCO, California--Customhouse, Rm. 504, 555 Washington, D.C. 20402 Battery St. • SPOKANE, Washington--U.S. Courthouse, Rm. 678, West (Check or money order must be payable to Superintendent of Docu­ 920 Riverside Ave.. ments.) • ANCHORAGE, Alaska--Rm. 101, 4230 University Dr. • ANCHORAGE, Alaska--Federal Bldg, Rm. 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 G Gold in Placer Deposits Gold Placers By WARREN YEEND and DANIEL R. SHAWE Gold Deposits in the Virginia City-Alder Gulch District, Montana By DANIEL R. SHAWE and KENNETH L. WI ER U.S. GEOLOGICAL SURVEY BULLETIN 1857 GEOLOGY AND RESOURCES OF GOLD IN THE UNITED STATES DANIEL R. SHAWE and ROGER P. ASHLEY, Scientific Editors L.M.H. CARTER, Technical Editor 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: 1989 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 Gold in placer deposits. p. cm. —(Geology and resources of gold in the United States ; ch. G) (U.S. Geological Survey bulletin ; 1857-G) Includes bibliographical references. Contents: Gold placers / by Warren Yeend and Daniel R. Shawe — Gold deposits in the Virginia City-Alder Gulch District, Montana / by Daniel R. Shawe and Kenneth L. Wier. Supt. of Docs. no.: I 19.3:1857-G 1. Gold mines and mining—United States. 2. Placer deposits—United States. I. Yeend, Warren E., 1936- . II. Shawe, Daniel R., 1925- . III. Wier, Kenneth L. (Kenneth Leland), 1914- . IV. Series. V. Series: U.S. Geological Survey bulletin ; 1857-G. QE75.B9 no. 1857-G [TN423.A5] 557.3 s—dc20 [553.4'1'0973] 89-600287 CIP CONTENTS Gold placers AbstractGG1 IntroductionGG1 ProductionGG2 Descriptions of major placer-gold regions and districtsGG5 California modern and fossil placersGG5 Alaska modern placersGG7 Helena—Last Chance district, MontanaGG9 Virginia City—Alder Gulch district, MontanaGG9 Boise Basin district, IdahoGGll References cited Gll Gold deposits in the Virginia City-Alder Gulch district, Montana AbstractGG14 IntroductionGG14 Geology G15 Gold depositsGG15 Age of the depositsGG15 Placer goldGG15 Lode goldGG17 Genesis of the gold oresGG17 References cited G19 FIGURES G1. Map of California showing principal placer-gold mining areasGG5 G2. Sketch of a typical gold-diving operationGG6 G3. Map of Alaska showing principal placer-gold mining areasGG8 G4. Photograph of hydraulic mining on the North Fork of Harrison Creek, Circle quadrangle, AlaskaGG9 ContentsIIII G5. Map of Idaho and Montana showing locations of the Boise Basin, Virginia City—Alder Gulch, and Helena—Last Chance placer-gold districtsGGll G6. Map of Montana showing the location of the Virginia City—Alder Gulch districtGG14 G7. Generalized geologic map of the Virginia City—Alder Gulch districtGG16 G8. Map of the Virginia City—Alder Gulch district showing zoning of the Au:Ag ratios of gold oresGG18 TABLES G1. Gold production from major placer areas in the United States G3 G2. Major active 1980's gold placer mining areas of AlaskaGG10 IVIContents GEOLOGY AND RESOURCES OF GOLD IN THE UNITED STATES Gold in Placer Deposits Gold Placers By Warren Yeend and Daniel R. Shawe Abstract of placer gold, including about 4,000,000 ounces from the Nome district. Most of the gold was derived from raised Man most likely first obtained gold from placer beach deposits. Source of the gold probably is Tertiary- deposits, more than 6,000 years ago. Placers account for mineralized faults and joints in metamorphic rocks of late more than two-thirds of the total world gold supply, and Precambrian age. roughly half of that mined in the States of California, Alaska, The Helena-Last Chance district, Montana, produced Montana, and Idaho. nearly 1 million ounces of gold from placers that were derived Placer deposits result from weathering and release of from lode deposits in the contact zones of the Cretaceous gold from lode deposits, transportation of the gold, and Boulder batholith granitic rocks intruded into upper Pre­ concentration of the gold dominantly in stream gravels. cambrian, Paleozoic, and Mesozoic sedimentary rocks. The Unless preserved by burial, a placer subsequently may be Virginia City-Alder Gulch district, Montana, produced more eroded, and either dispersed or reconcentrated. than 2,600,000 ounces of gold, nearly all from placer California has produced more than 40 million troy deposits derived from quartz veins of uncertain age in ounces of gold from placers, both modern and fossil Archean gneisses and schists. The Boise basin district, (Tertiary). The source of the great bulk of the gold is Idaho, produced about 2,300,000 ounces of gold, mostly numerous quartz veins and mineralized zones of the Mother derived from quartz veins in quartz monzonite of the Lode and related systems in the western Sierra Nevada Cretaceous Idaho batholith. region. The gold-bearing lodes were emplaced in Carbonif­ erous and Jurassic metamorphic rocks intruded by small bodies of Jurassic and Cretaceous igneous rocks. Miner­ INTRODUCTION alization occurred probably in Late Cretaceous time. Significant amounts of placer gold also were mined along the Man has been mining placer gold for more than Salmon and Trinity Rivers in northern California. Source of 6,000 years, and it is most likely that he first obtained the the gold is lode deposits in Paleozoic and Mesozoic meta­ precious metal from placers. Placers have produced morphic rocks that were intruded by Mesozoic igneous more than two-thirds of the total world gold supply rocks. (Boyle, 1979). Alaska has produced roughly 21 million ounces of gold The term "placer," probably of Spanish derivation, from placer deposits. Most (about 13 million ounces) has is typically applied to gold deposits in the sands and come from the interior region, including 7,600,000 ounces gravels of streams. Today we define a placer as a deposit from the Fairbanks district and 1,300,000 ounces from the of sand, gravel, and other detrital or residual material Iditarod district. Lode sources are believed to be mostly containing a valuable mineral that has accumulated quartz veins in Precambrian or Paleozoic metamorphic rocks intruded by small igneous bodies near Fairbanks, and shear through weathering and mechanical concentration. The zones in Tertiary(?) quartz monzonite stocks at Iditarod. The term placer as used here applies to ancient (Tertiary) as Seward Peninsula has produced more than 6 million ounces well as to recent (Holocene) gravel deposits, and to underground deposits (drift mines) as well as to surface deposits.
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