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The Seaman Volcanic Center- a Rare Middle Tertiary Stratovolcano in Southern Nevada U.S. GEOLOGICAL SURVEY BULLETIN 2052

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The Seaman Volcanic Center- a Rare Middle Tertiary Stratovolcano in Southern Nevada U.S. GEOLOGICAL SURVEY BULLETIN 2052 The Seaman Volcanic Center- A Rare Middle Tertiary Stratovolcano in Southern Nevada I I I U.S. GEOLOGICAL SURVEY BULLETIN 2052 AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey 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 monthly, which is for sale in microfiche from the USGS ESIC-Open-File Report Sales, Box 25286, Building 810, Denver Federal Center, Denver, CO 80225 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, Tech­ Books of the U.S. Geological Survey are available over the niques of Water-Resources Investigations, Circulars, publications counter at the following U.S. Geological Survey offices, all of of general interest (such as leaflets, pamphlets, booklets), single which are authorized agents of the Superintendent of Documents. copies of periodicals (Earthquakes & Volcanoes, Preliminary De­ termination of Epicenters), and some miscellaneous reports, includ­ • ANCHORAGE, Alaska-4230 University Dr., Rm. 101 ing some of the foregoing series that have gone out of print at the • ANCHORAGE, Alaska--605 West 4th Ave., Rm G-84 Superintendent of Documents, are obtainable by mail from • DENVER, Colorad~Federal Bldg., Rm. 169, 1961 Stout St. USGS Map Distribution Box 25286, Building 810 • LAKEWOOD, Colorad~Federal Center, Bldg. 810 Denver Federal Center • MENLO PARK, California-Bldg. 3, Rm. 3128,345 Denver, CO 80225 Middlefield Rd. Subscriptions to periodicals (Earthquakes & Volcanoes and • RESTON, Virginia-National Center, Rm. 1C402, 12201 Preliminary Determination of Epicenters) can be obtained ONLY Sunrise Valley Dr. from • SALT LAKE CITY, Utah-Federal Bldg., Rm. 8105, 125 South State St. Superintendent of Documents U.S. Government Printing Office • SPOKANE, Washington-U.S. Courthouse, Rm. 678, West Washington, DC 20402 920 Riverside Ave. • WASHINGTON, D.C.-U.S. Department of the Interior Bldg., (Check or money order must be payable to Superintendent of Rm. 2650, 1849 C St., NW. Documents.) Maps Maps Maps may be purchased over the counter at the U.S. Geolog­ For maps, address mail order to ical Survey offices where books are sold (all addresses in above list) and at the following Geological Survey offices: USGS Map Distribution Box 25286, Building 810 Denver Federal Center • ROLLA, Missouri-1400 Independence Rd. Denver, CO 80225 • FAIRBANKS, Alaska-New Federal Building, 101 Twelfth Ave. Residents of Alaska may order maps from U.S. Geological Survey, Map Sales 101 Twelfth Ave., Box 12 Fairbanks, AK 99701 The Seaman Volcanic Center- A Rare Middle Tertiary Stratovolcano in Southern Nevada By EDWARD A. DU BRAY U.S. GEOLOGICAL SURVEY BULLETIN 2052 Geology and geochemical evolution of a rare, well-preserved middle Tertiary stratovolcano UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1993 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director For sale by USGS Map Distribution Box 25286, Building 810 Denver Federal Center Denver, CO 80225 Any use of trade, product, or finn names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government. Library of Congress Cataloging-in-Publication Data Du Bray, E. A. The Seaman volcanic center ; a rare middle Tertiary stratovolcano in southern Nevada I by Edward A. du Bray. p. em. - (U.S. Geological Survey bulletin; 2052) Includes bibliographical references. Supt. of Docs. no.: 1.19.3:B2052 1. Volcanoes-Nevada-Lincoln County. 2. Geology, Stratigraphic-Tertiary. 3. Geochemistry-Nevada-Lincoln County. I. U.S. Geological Survey. II. Title. III. Series. QE75.B9 no. 2052 [QE524] 557.3 s-dc20 93-2837 [551.2'1'0979314] CIP CONTENTS Abstract................................................................................................................................. 1 Introduction........................................................................................................................... 1 Geology of the Serunan Volcanic Center.............................................................................. 3 Petrography........................................................................................................................... 3 Geochemistry of the Seaman Volcanic Center..................................................................... 4 Whole-Rock Chemistry.............................................................................................. 4 Mineral Chemistry...................................................................................................... 10 Major Element Least-Squares Fractionation-Mixing Modeling........................................... 11 Evolution of the Seaman Volcanic Center............................................................................ 12 Summary and Conclusions................................................................................................... 17 References Cited................................................................................................................... 18 FIGURES 1. Generalized geologic map of the Seaman volcanic center, Lincoln County, Nevada................................................... 2 2. Photomicrographs showing petrographic features of components of the Seaman volcanic center ... ........................... 5 3. Alkali-silica classification diagram showing analyses of samples from the Seaman volcanic center........................... 6 4. Ternary AFM diagram showing compositions of samples from the Seaman volcanic center...................................... 7 5. Diagrrun showing the variation of rubidium and strontium abundances in samples from the Seaman volcanic center.............................................................................................................................................................................. 8 6. Chondrite-normalized diagram showing compositions of samples from the Seaman volcanic center ......................... 8 7. Chondrite-normalized extended trace element diagram showing compositions of samples from the Seaman volcanic center ... .. ...... ................ .. ............. ..... .. ..... .... .. ... .. ... ................. ... ... ............. .............................................. 9 8. Enrichment-depletion diagram showing major- and trace-element abundances of the Serunan volcanic center dike normalized to those of the lava flow unit....................................................................................................................... 14 9. Tectonic setting-trace element discriminant variation diagrams for components of the Seaman volcanic center........ 17 TABLES 1. Major-oxide and normative mineral composition for samples of the Seaman volcanic center, Lincoln County, Nevada........................................................................................................................................................................... 6 2. Trace element data for samples of the Serunan volcanic center, Lincoln County, Nevada........................................... 7 3. Instrumental neutron activation data for samples of the Seaman volcanic center, Lincoln County Nevada................. 7 4. Average major-oxide, normative, and trace-element compositions of components of the Seaman volcanic center, Lincoln County, Nevada................................................................................................................................................ 8 5. Representative mineral compositions for phenocryst phases in samples of the Seaman volcanic center, Lincoln County, Nevada.............................................................................................................................................................. 10 6. Results of major element least-squares crystal fractionation-mixing modeling for samples of the Seaman volcanic center, Lincoln County, Nevada.................................................................................................................................... 12 01 THE SEAMAN VOLCANIC CENTER-A RARE MIDDLE TERTIARY STRATOVOLCANO IN SOUTHERN NEVADA By EDWARD A. DUBRAY ABSTRACT INTRODUCTION The Seaman volcanic center is a composite, middle The Seaman volcanic center is clearly denoted as a Tertiary stratovolcano in southern Nevada; it is about 10 small, circular volcanic feature on the geologic map of km (6 mi) in diameter and has a reconstructed volume of Nevada (Stewart and Carlson, 1978). The west-central part about 20 km3 (5 mi3). The center is principally composed of the Seaman Range is dominated by the Seaman volca­ of interbedded dacite lava and pyroclastic flows whose nic center (fig. 1), a feature first noted and described by eruption built a stratovolcano that was intruded by rhyolite Tschanz and Pampeyan (1961, 1970) and believed
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