USGS Research on Mineral Resources-1989 

Program and Abstracts 

Fifth Annual V.E. McKelvey Forum on 

Mineral and Energy Resources 

U.S. GEOLOGICAL SURVEY CIRCULAR 1035 
A view of the main ore zone at the Carlin mine, Nevada. 

Popovich Hill is on the left and is underlain by carbonaceous 

rocks of the Silurian Roberts Mountains Formation. The discovery of this disseminated gold deposit in the 1960's inspired 

much of the subsequent gold exploration in the Western United 

States. 
USGS Research on Mineral Resources-1989 

Program and Abstracts 

Edited by Katharine S. Schindler 

Fifth Annual V.E. McKelvey Forum on 

Mineral and Energy Resources 

U.S. GEOLOGICAL SURVEY CIRC~LAR 1035 
DEPARTMENT OF THE INTERIOR 

DONALD PAUL HODEL, Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director 

Organizing Committee for the 1989 McKelvey Forum: 

Wayne C. Shanks Ill , Chairman 

Nora Foley Ayuso 

Michael P. Foose 

Jules D. Friedman 

Martin B. Goldhaber 

Larry P. Gough 

Ri chard F. Hardyman 

David A. John 

Rama K. Kotra 

Walden P. Pratt 

Katharine S. Schindler 

Willis H. White 

Robert A. Zierenberg 

UNITED STATES GOVERNMENT PRINTING OFFICE 1988 

Free on application to 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 

V.E. McKelvey Forum on Mineral and Energy Resources 

(5th : 1989 : Reno, Nev.) 

USGS research on mineral resou rces-1989. 

(U.S. Geological Survey circular ; 1035) 

Bibliography: p. 

Supt. oi Docs. no.: I 19.4/2: 1035 

1. Mines and mineral resources-United States-Ccngresses. I. Schindler, 

Katharine S. II. Title. Ill. Series. 

TN23 .V2 1988 553' .0973 88-600419 

Any use of tradenames or trademarks in this publi cation is for descriptive purposes only 

and does not constitute e ndorsement by the U.S. Geologica l Survey. 
A society's wealth depends on the use it makes of 

raw materials, energy, and especially ingenuity. 

- V.E. McKelvey 

Ill 

FOREWORD 

The V.E. McKelvey Forum is named for Vincent E. McKelvey in recognition of his 

lifelong contributions in mineral and energy resources as a research scientist, as Chief 

Geologist of the U.S. Geological Survey (USGS), and as Director of the USGS. The 

Forum is an annual event, and its purpose is to encourage direct communication between 

USGS scientists and earth scientists in the private sector, academia, and other government 

agencies. The first four V.E. McKelvey Forums have been well attended and clearly have 

been successful in fostering better communication. 

Traditionally, the subject of the Forum has alternated between mineral and energy 

resources. This year the focus is again on minerals and has as its general theme 

collaborative research between the USGS and co-workers from industry, academia, and 

other State and Federal Government agencies. I am extremely pleased to report that the 

abstracts in this volume attest to a healthy interaction with our counterparts in the rest of 

the earth science community. We hope that this Forum will foster additional collaborative 

studies. 

As a result of responses we have received during past Forums, our programs are 

taking some new directions. Current mineral-resource programs in the USGS include 

basic research on ore-deposit systems, studies of strategic and critical minerals, and the 

evaluation of the mineral resources of specific regions. These programs support diverse 

work such as the development of geochemical and geophysical exploration techniques, 

the detailed geologic study of specific mineral deposits, evaluation of unconventional 

environments for strategic commodities, and the assessment of resources of public lands. 

The papers for the 1989 Forum cover these topics as well as many other areas and 

demonstrate the wide range of topics that characterize USGS research. However, because 

of the location of the Forum in Reno, Nev., there is a special emphasis on gold and other 

precious-metal deposits in the Western United States. The diverse topics covered in this 

Forum include airborne geophysical studies of concealed mineral deposits in Nevada and 

elsewhere, evaluation of the regional geological factors controlling the occurrence of 

disseminated gold deposits, mineral-resource assessments of the midcontinent area, 

presentations of new digital techniques for geologic mapping and the handling of mineral 

information, studies of offshore deposits of titanium and of ferromanganese and 

polymetallic sulfides, and specific deposit studies of Red Dog, Alaska; Paradise Peak, 

Jerritt Canyon, Battle Mountain, and the Comstock Lode, Nev.; Mesquite, Calif.; 

Gilman, Colo.; and Bayan Obo. China. 

I am pleased with the success of previous Forums, and I look forward to a 

productive and enlightening meeting in 1989. We welcome the opportunity to discuss 

USGS research with our colleagues and to hear suggestions that will help us serve the 

mineral resource needs of the Nation. 

Dallas L. Peck 

Director 

v 
VI 

An Introduction to the Mineral Resources Programs of the 

U.S. Geological Survey 

Over the last decade, there has been a dramatic increase in public concern over 

issues related to the availability of minerals, the use of public lands, and the environment. 

To a large extent, these concerns have directly affected the nature of mineral-related 

investigations. These investigations, which have been carried out by geoscientists in 

academia, government, and industry, are essential to making informed decisions on land 

use, mineral exploration, and mineral development. As in 1985 and 1987, this year's 

Forum will highlight the results of recent and ongoing mineral-related research within the 

U.S. Geological Survey (USGS). The USGS has three national programs in mineralrelated studies. 

The Development of Assessment Techniques Program (OAT) is oriented principally 

toward basic and applied research on the origin and the geologic, geochemical, and 

geophysical expression of mineral-deposit systems. The program's goal is to develop 

concepts and techniques to improve the capability of identifying and evaluating mineral 

resources. To this end, the program supports a broad spectrum of multidisciplinary field 

and laboratory research directed toward understanding how mineral deposits form. OAT 

also supports research to develop new technologies that can be used to locate mineral 

deposits and to develop new methods to make areal mineral-resource assessments. In 

addition to specifically supporting research on the geologic characteristics of ore deposits, 

geochemical exploration techniques, geophysical exploration techniques, deposit and 

district studies, and laboratory research, the program also has developed three multidisciplinary research efforts that focus on (1) disseminated gold deposits, (2) the role of 

organics in ore deposits, and (3) the formation of polymetallic sulfide deposits. 

The Strategic and Critical Minerals Program (SCM) provides a continuing 

assessment of the Nation's strategic mineral endowment. This information is essential for 

formulating a national mineral policy and for identifying secure foreign sources of 

strategic and critical minerals. Major activities within this program include (1) studies of 

geologic characteristics of major mineral commodities, (2) the development and maintenance of mineral data files that are used for research on the characteristics of mineral 

deposits and in the development of statistical techniques for mineral resource assessments, 

(3) the geologic study of domestic environments that may host deposits of strategic and 

critical minerals, (4) basic research on mineral-deposit genesis and metallogeny and other 

geologic studies that pertain to resource information analysis, and (5) support for 

international programs of mineral deposit data exchange and cooperative resource studies. 

Recently, a major new initiative has been approved for this program for work directed 

toward evaluating the mineral resources in covered areas of Alaska. 

The National Mineral Resources Assessment Program (NAMRAP) provides the 

areal mineral resource information necessary for identifying, assessing, and facilitating 

the long-term mineral supply of the Nation. This program is most directly responsible for 

assessing the mineral resources of the Nation's public and other lands. These assessments, 

and supporting geologic, geochemical, and geophysical studies, provide extensive 

mineral resource information to the public, industry, academic communities, and all those 

who are concerned with national mineral policy and land use decisions. These mineralresource studies include (1) large-scale studies (greater than 1:250,000) that recently have 

primarily involved mineral surveys of areas managed by the Bureau of Land Management, (2) studies of 1 o x 2° quadrangles (1 :250,000) or similar sized areas, which involve 

multidisciplinary studies by geologists, geochemists, geophysicists, and mineral economists, (3) studies at scales of 1:250,000 to 1:1,000,000 that use published literature but 

involve little fieldwork, and (4) statewide and multistate syntheses of mineral resources. 

These three programs support each other. They range from work that involves basic 

and fundamental mineral-deposit research (OAT) to studies that are more focused on 

specific commodities, geologic environments, and data acquisition (SCM) to very specific 

work directed toward the assessment of resources of specific tracts of land. The result is 

an integrated approach to national mineral-resource problems. 
PROGRAM 

TUESDAY, 24 JANUARY 

7:00 to 10:00 PM POSTER SESSION 

WEDNESDAY, 25 JANUARY 

8:30 AM Welcome and opening remarks 

8:40 AM An introduction to the research programs of the U.S. 

Geological Survey-by Michael P. Foose 

9:00 AM Overview and preview of U.S. Geological Survey ore 

deposit research: Fifth Annual V.E. McKelvey 

Forum-by Lorraine H. Filipek 

9:30 AM 

10:00 AM 

10:30 AM 

11:00 AM 

12:00 

1:00 PM 

1:30 PM 

2:00 PM 

2:30 PM 

3:00 PM 

3:30 PM 

3:35 PM 

4:00 PM 

4:30 PM 

5:00 PM 

Methodology for analysis of concealed mineral resources in 

Nevada: A progress report-by Dennis P. Cox, Steve 

Ludington, Maureen G. Sherlock, Donald A. Singer, 

Byron R. Berger, Richard J. Blakely, John C. Dohrenwend, Donald F. Huber, Robert C. Jachens, Edwin H. 

McKee, Christopher M. Menges, Barry C. Moring, and 

Joe Tingley 

Analysis of concealed mineral resources in Nevada: Constraints from gravity and magnetic studies-by Robert C. 

Jachens, Richard J. Blakely, and Barry C. Moring 

COFFEE AND POSTER BREAK 

KEYNOTE LECTURE: Modem geoscience in the quest for 

gold: An Australian perspective-by Richard W. Henley 

LUNCH 

The Getchell trend airborne geophysical demonstration 

project, north-central Nevada-by D.B. Hoover, V.J.S. 

Grauch, M.D. Krohn, V.F. Labson, and J.A. Pitkin 

Geology and origin of the Jerritt Canyon sediment-hosted 

disseminated gold deposits, Nevada-by A.H. Hofstra, 

G.P. Landis, R.O. Rye, D.J. Birak, A.R. Dahl, W.E. 

Daly, and M.B. Jones 

Volcanic-tectonic setting and geology of the Paradise Peak 

gold-silver-mercury deposit, Nye County, Nevada-by 

David A. John, Robert E. Thomason, Charles W. Clark, 

and Edwin H. McKee 

Structural control on epithermal gold veins and breccias in 

the Mesquite district, southeastern California-by G.F. 

Willis, R.M. Tosdal, and S.L. Manske 

COFFEE AND POSTER BREAK 

INTRODUCTION (5 MINUTES): Evolution of the five 

Midcontinent CUSMAPs and the Midcontinent SCM 

project-by Walden P. Pratt 

Late Cambrian lithofacies and their control on the Mississippi Valley-type mineralizing system in the Ozark 

region-by James R. Palmer and Timothy S. Hayes 

Tectonic and stratigraphic control of subsurface geochemical 

patterns in the Ozark region-by R.L. Erickson, Barbara 

Chazin, M.S. Erickson, E.L. Mosier, and Helen Whitney 

A conodont color alteration anomaly in central IndianaPossibility of Mississippi Valley-type hydrothermal 

activity-by A.G. Harris, C.B. Rexroad, R.T. Lierman, 

and R.A. Askin 

Proterozoic anorogenic granite-rhyolite terranes in the midcontinental United States-Possible hosts for Cu-, Au-, 

Ag-, U-, and REB-bearing iron-oxide deposits similar to 

the Olympic Dam orebody-by P.K. Sims, K.J. Schulz, 

and Eva B. Kisvarsanyi 

7:00 PM DIRECTOR'S LECTURE: New perspectives on the interrelationship of tectonics and ore-forming processes in the 

Great Basin: Implications for exploration-by Byron R. 

Berger 

8:00 to 10:00 PM POSTER SESSION 

THURSDAY, 26 JANUARY 

8:30 AM Evaluation of Advanced Visible and Infrared Imaging Spectrometer and other remotely sensed data for mineral 

exploration in semiarid terrains-by G.B. Bailey and J.L. 

9:00 AM 

9:30 AM 

10:00 AM 

10:30 AM 

11:00 AM 

11:30 AM 

1_2:00 

2:00 PM 

2:30 PM 

3:00 PM 

3:30 PM 

4:00 PM 

4:30 PM 

5:00 PM 

Dwyer 

Interpreting concealed range-front faults in Nevada from 

gravity and digital fault data and the significance for gold 

exploration-by V .J. S. Grauch and Don L. Sawatzky 

Mosaic faulting as a guide to mineral exploration in the 

Richfield 1° X 2° quadrangle, western Utah-by Thomas 

A. Steven 

Volcanism, extensional tectonics, and epithermal mineralization in the northern Basin and Range province, California, Nevada, Oregon, and Idaho-by James J. Rytuba 

COFFEE AND POSTER BREAK 

Genetic model for the carbonate-hosted Pb-Zn-Cu-Ag-Au 

manto-chimney deposits of the Gilman, Colorado district, 

based on fluid inclusion, stable isotope, geologic, and 

fission-track time-temperature studies-by D.W. Beaty, 

C.G. Cunningham, C.W. Naeser, and G.P. Landis 

A deposit model for gold-bearing skams-by Jane M. 

Hammarstrom, Greta J. Orris, James D. Bliss, and Ted 

G. Theodore 

McKELVEY FORUM LUNCHEON 

LUNCHEON ADDRESS: Gold-rich massive sulfides on the 

modem sea floor and their ancient analogs-by Steven D. 

Scott 

Active deposition of sediment-hosted massive sulfide in 

Escanaba trough, Gorda Ridge-by Robert A. Zierenberg, J.M. Edmond, J.F. Grassle, A.C. Campbell, S.L. 

Ross, and W.C. Shanks III 

Potential for epigenetic gold and sedex-type Pb-Zn-Ag-Ba 

deposits in the Taconic Allochthons, eastern New York 

and western Vermont-by John F. Slack and Kenneth C. 

Watts, Jr. 

COFFEE AND POSTER BREAK 

Early-middle Proterozoic unconformities: Unconventional 

sources for platinum group and precious metals-by 

Richard I. Grauch 

Oxygen isotope map of the fossil hydrothermal system in the 

Comstock Lode mining district, Nevada-by Robert E. 

Criss, Duane E. Champion, and Mary F. Horan 

Multiple sources for gold in the Juneau gold belt, Alaskaby Rainer J. Newberry and David A. Brew 

Metallogenesis of lode mineral deposits of "mainland" 

Alaska-by Warren J. Nokleberg, Thomas K. Bundtzen, 

Donald J. Grybeck, and Thomas E. Smith 

VII 
LIST OF POSTERS 

I. GENERAL TOPICS and GEOLOGICAL 

INFORMATION SYSTEMS 

1. Minerals Information Office-by Susan M. Marcus, Raymond 

E. Arndt, Paul G. Schruben, Carl Carlson, and Jane Jenness 

2. Geologic-map information and where to find it-by H. Kit 

Fuller 

3. The Development of Assessment Techniques Program (OAT) of 

the U.S. Geological Survey-by Michael P. Foose 

4. The Strategic and Critical Minerals Program (SCM) of the U.S. 

Geological Survey-by William C. Bagby 

5. A review of the proposed standard for digital cartographic databy Robin G. Fe geas', Hedy J. Rossmeissl, and Robert D. Rugg 

6. Multidisciplinary considerations in a digital geologic map-Applications and afterthoughts-by S.H. Moll, J.L. Dwyer, 

C.A. Wallace, J.E. Elliott, C.M. Trautwein, and J.E. Harrison 

7. A simplified digital geologic map of Nevada for regional gold 

resource assessment-by S.P. Marsh, E. Sandoval, and J.L. 

Plesha 

8. Three-dimensional characterization of regional structures using 

an advanced geographic information system-by D.B. Stewart, B.E. Wright, J.D. Unger, J.D. Phillips, and L.H. Liberty 

9. Mineral resource assessment of the Butte 1° x 2° quadrangle 

using geographic information system technology- by J .E. 

Elliott, C.M. Trautwein, J.L. Dwyer, and S.H. Moll 

II. MINERAL RESOURCE ASSESSMENTS 

VIII 

10. Mineral resource assessment of the White Mountains National 

Recreation Area, east-central Alaska-by Florence R. 

Weber, Thomas D. Light, Richard B. McCammon, and C. 

Dean Rinehart 

11. Geology and mineral resources of the Port Moller region, 

western Alaska Peninsula, Aleutian Arc-by Frederic H. 

Wilson, Willis H. White, and Robert L. Detterman 

12. Mineral resource assessment, Bendeleben and Solomon quadrangles, western Alaska-by Bruce M. Gamble 

13. Regional geochemical studies of the Ajo and Lukeville 1° x 2° 

quadrangles, Arizona-by Harlan Barton and Paul K. 

Theobald 

14. Delta CUSMAP Project: Mineral assessment in the Tintic-Deep 

Creek mineral belt of the eastern Great Basin, Utah-by 

Douglas B. Stoeser, Carol N. Gerlitz, Constance J. Nutt, 

Holly J. Stein, John Hand, Michael A. Shubat, and Judith L. 

Hannah 

15. Geoelectric studies in the Delta, Utah, quadrangle-by D.L. 

Campbell and V. F. Labson 

16. The Tooele 1 o x 2° quadrangle, western Utah: An example of a 

CUSMAP preassessment study-by Holly J. Stein, Viki 

Bankey, C.G. Cunningham, David R. Zimbelman, Michael 

A. Shubat, David W. Brickey, D.L. Campbell, and M.H. 

Podwysocki 

17. Precious-metal deposits in the Hailey and western Idaho Falls 1 o 

x 2° quadrangles, Idaho-by Ronald G. Worl, Earl H. 

Bennett, Palma J. Moye, and P.K. Link 

18. Gravity and magnetic anomaly patterns in mineral resource 

exploration, Hailey CUSMAP, Idaho-by M. Dean 

Kleinkopf 

19. Geological studies of the International Falls and Roseau 1 o x 2° 

CUSMAP quadrangles, northern Minnesota-by W.C. Day, 

T.L. Klein, D.L. Southwick, and K.J. Schulz 

20. Regional geophysical studies for the International Falls and 

Roseau CUSMAP projects-by Robert J. Horton, Val W. 

Chandler, Robert E. Bracken, and James E. Case 

Ill. INVESTIGATIONS OF MINERALIZING 

PROCESSES AND MINERALIZING SYSTEMS 

A. Western U.S. 

21. Geological and geophysical analysis of the subsurface 

geometry of basins in the central and western Great 

Basin: Implications for the analysis of concealed 

mineral resources in Nevada-by John C. Dohrenwend, Robert C. Jachens, Richard J. Blakely, Barry 

C. Moring, and Christopher M. Menges 

22. Tertiary tectonic evolution of the central Walker Lane, 

western Nevada-by Richard P. Keller, John S. 

Oldow, Richard F. Hardyman, and John W. Geissman 

23. Study of the stratigraphy of the gold-bearing Preble 

Formation near the type locality, north-central Nevada-Some benefits to exploration- by Dawn J. 

Madden-McGuire 

24. Characterization of carbon in sediment-hosted disseminated gold mineralization at Jerritt Canyon, Nevadaby Joel Leventhal and A.H. Hofstra 

25. Geology and geochemistry in the vicinity of the Adelaide 

Crown mine, Humboldt County, Nevada-by Theresa 

M. Cookro and Ted G. Theodore 

26. Bismuth minerals associated with placer gold, Battle 

Mountain mining district, Nevada-by Ted G. Theodore, Gerald K. Czamanske, Terry E.C. Keith, and 

Robert L. Oscarson 

27. 40 Ar/39 Ar studies of fluid inclusions in vein quartz from 

Battle Mountain, Nevada-by Brent D. Turrin, Edwin 

H. McKee, Ted G. Theodore, and James E. Conrad 

28. Multiple ages of disseminated gold mineralization associated with volcanic cycles in southwestern Utah and 

adjacent Nevada-by W.R. Miller and J.B. McHugh 

29. Reconstruction of primary features and isotopic evidence 

for multiple sulfur sources at the Red Dog zinclead-silver deposit, Noatak district, Alaska-by Jeanine M. Schmidt and Robert A. Zierenberg 

30. Sulfur isotope characteristics of bedded and vein barite 

deposits, north-central Nevada-by StephenS. Howe 

31. Volcanogenic massive sulfide deposits in pre-Tertiary 

island arc and ocean basin environments in Nevadaby Maureen G. Sherlock 

32. Composition and geologic setting of stratiform manganese deposits in the southern Basin and Range province-by Randolph A. Koski, Robin M. Bouse, James 

R. Hein, and Marilyn L. DeRosa 

33. Industrial rock and mineral resources of Arizona: A 

survey of resource problems and opportunities by the 

producers and users of resource information- by 

Edwin W. Tooker and Larry D. Fellows 

34. Preliminary map showing the location of productive lode 

and placer gold deposits and significant gold prospects 

in Montana-by David Frishman, J.E. Elliott, E.E. 

Foord, R.C. Pearson, and W.H. Raymond 

35. As, Bi, Hg, S, Sb, and Te geochemistry of the J-M reef: 

Constraints on the origin of platinum group elementenriched sulfides in layered intrusions-by M.L. Zientek, T.L. Fries, and R.W. Vian 
36. Chemical modeling of ore and gangue deposition in the 

Creede, Colorado, epithermal system-by Geoffrey S. 

Plumlee 

B. Midcontinent 

37. Contrasting sulfur sources for lower versus upper midcontinent Mississippi Valley-type ores-Implications for ore 

genesis- by Martin Goldhaber 

38. Manganese potential of the Cretaceous rocks flanking the 

Sioux Ridge, Minnesota and South Dakota-by Dale R. 

Setterholm and Richard H. Hammond 

39. Tectonic and magmatic development of the Midcontinent 

rift: A synthesis of new seismic, chemical, and isotopic 

data-by W.F. Cannon, S.W. Nicholson, and Alan Green 

40. Metallogeny of the Midcontinent rift in the Lake Superior 

region-by S.W. Nicholson, K.J. Schulz, and W.F. 

Cannon 

41. Geochemistry of igneous rocks of the Penokean orogen: 

Implications for metallogeny and tectonic setting-by K.J. 

Schulz and P.K. Sims 

C. Eastern U.S. 

42. Caraway-Back Creek volcanic center, central slate belt, 

North Carolina: Newly recognized thermal source for 

precious- and base-metal mineralization- by Robert P. 

Koeppen and Terry L. Klein 

43. Stratabound copper and zinc mineralization in Triassic 

lacustrine beds of the Culpeper basin, Virginia-by Gilpin 

R. Robinson, Jr. and Joseph P. Smoot 

44. Fluid inclusion and mineralogic studies of a palladiumplatinum anomaly zone in the Reeser's Summit diabase, 

Pennsylvania: Evidence for hydrothermal transport-by 

Harvey E. Belkin 

45. Anomalous palladium-platinum occurrences in Mesozoic 

quartz-normative tholeiitic suites in the Eastern United 

States-by David Gottfried, A.J. Froelich, P.J. Aruscavage, and Norma Rait 

46. Rare-earth resource potential: Monazite distribution in the 

Fall Zone Coastal Plain sediments of western South 

Carolina-by James P. Owens and Andrew E. Grosz 

D. Marine Studies 

-1-7. Hydrothermal and hydrogenetic ferromanganese oxide mineralization of active volcanic arcs-by James R. Hein, 

Marjorie S. Schulz, and Jung-Keuk Kang 

48. Chemical analysis of ocean floor manganese crusts-by 

Herbert Kirschenbaum, F.T. Manheim, P.J. Aruscavage, 

and C.M. Lane-Bostwick 

49. Silt-size rutile in Quaternary sediment of the Gulf of 

Maine-A large, unconventional Ti02 resource-by Page 

C. Valentine and Judith A. Commeau 

E. International Studies 

50. Characteristics and geochemistry of gold deposits in northem Sonora, Mexico-by Miles L. Silberman and David A. 

Giles 

51. New tin deposits in the Amazon basin, Brazil-by C.H. Thorman, L.J. Drew, and M. Drucker 

52. Geology, geochemistry, and age of the Gejiu batholith and 

associated polymetallic deposits, southern China-by 

Lawrence W. Snee and Wang Zhifen 

53. The H8 dolomite host rock of the Bayan Obo iron-niobiumrare-earth-element ore deposit of Inner Mongolia, ChinaOrigin, episodic mineralization, and implications-by 

E.C.T. Chao, J.A. Minkin, J.M. Back, P.M. Okita, 

Edwin H. McKee, R.M. TosdaL M. Tatsumoto, Wang 

Junwen, C.A. Edwards, Ren Yingzhen, and Sun Weijun 

54. Geologic setting of iron-niobium-rare-earths orebodies at 

Bayan Obo, Inner Mongolia, China, and a proposed 

regional model-by L.J. Drew, Meng Qingrun, and Sun 

Weijun 

55. Petrography, chemistry, age, and origin of the rare-earth iron 

deposit at Bayan Obo, China, and implications of Proterozoic iron ores in Earth evolution-by J.A. Philpotts, M. 

Tatsumoto, K. Wang, and P-F. Fan 

IV. GEOCHEMICAL INVESTIGATIONS 

56. Seasonal vanatwns in concentrations of helium and carbon 

dioxide in soil gases at the Roosevelt Hot Springs known 

geothermal resource area, Utah-by Margaret E. Hinkle 

57. Flow injection analysis applications in mineral resource exploration and environmental chemistry-by Delmont M. Hopkins 

58. Mineral resource and geochemical exploration potential of coal 

that has anomalous metal concentrations-by Robert B. 

Finkelman and Robert D. Brown, Jr. 

59. Geochemistry of soils in the Carson River valley, Nevada-by 

Ronald R. Tidball 

60. Evaluation of multiple geochemical sample media at the Betze 

gold deposit. Eureka County. Nevada-by J.H. McCarthy, 

Jr., J.A. Erdman, T.G. Lovering, and K.H. Bettles 

V. GEOPHYSICAL INVESTIGATIONS 

61. Aeromagnetic and gravity studies of a buried porphyry copper 

deposit near Casa Grande, Arizona-by Viki Bankey and 

Douglas P. Klein 

62. Spectral reflectance changes in vegetation associated with 

anomalous concentrations of metallic elements-A potential 

tool for mineral exploration-by Barbara A. Eiswerth. 

Nancy M. Milton, and David A. Mouat 

63. The applications of airborne radar for mineral and energy 

resources exploration-by John E. Jones, Allan N. Kover, 

and Bruce F. Molnia 

64. Airborne imaging spectrometer data as an aid to mineral 

mapping, Cuprite, Nevada-by M.H. Podwysocki and O.D. 

Jones 

65. Application of developing technology in airborne geophysics. 

Effie-Coon Lake Complex, Minnesota-by Bruce D. Smith. 

V.F. Labson, Robert E. Bracken. Robert J. Bisdorf, Viki 

Bankey, Robert P. Kucks, Robert J. Horton, Michael G. 

Medberry, Jay A. Sampson. and J.L. Plesha 

66. Plans for integrated airborne geophysical study of the Geophysics Environmental and Minerals demonstration area, 

south-central Colorado- by Kenneth Watson, D.H. Knepper. R.N. Clark, J.A. Pitkin, V.F. Labson, D.L. Campbell, 

L.C. Rowan, F.A. Kruse. K. Lee, and E. Livo 

IX 

Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 

USGS Research on Mineral Resources-1989 Program and Abstracts 

Edited by Katharine S. Schindler 

Evaluation of Advanced Visible and Infrared 

Imaging Spectrometer and Other Remotely 

Sensed Data for Mineral Exploration in 

Semiarid Terrains 

G.B. Bailey and j.L. Dwyer 

The principal role of remotely sensed data in mineral 

exploration is as a source of lithologic and structural 

information from which geologic interpretations important 

to the discovery of new mineral deposits can be made. The 

utility of remote sensing as an exploration tool has advanced 

dramatically since the launch of Landsat 1 in 1972, due in 

large measure to improvements in sensor technology, data 

processing capabilities, and data analysis and interpretation 

methodologies. Most significant have been advancements 

in the capability to discriminate lithologies and to determine 

and map rock compositions. especially in areas of good 

exposure. These advancements have resulted both from 

improvements in spectral characteristics and in spatial 

resolution of recent sensor systems. 

The Airborne Visible and Infrared Imaging Spectrometer (A VIRIS) is the most spectrally advanced land 

remote sensing system yet developed and is the prototype 

for a spaceborne sensor that will be launched in the 

mid-1990's. A VIRIS records reflected solar radiation 

between 0.4 and 2.5 ~m in 220 spectral bands that are 

approximately 9.5 nm wide. The sensor is currently flown 

on board an ER-2 aircraft at an altitude of 20 km and 

acquires data over an 11-km swath at 20-m spatial resolution. The technical characteristics of A VIRIS are particularly significant to geologists working in semiarid terrains 

where rocks are typically well exposed. A VIRIS data from 

these terrains may provide geologists with improved capabilities to discriminate between different lithologies. detect 

rock alteration, and identify constituent mineralogies of 

rocks and alteration from remotely sensed data. 

A VIRIS data were acquired over a test site in the 

Drum Mountains in west-central Utah where good exposures of many diverse rock and alteration types provide an 

environment well suited for geological evaluation of 

AVIRIS and other remotely sensed data. Rocks exposed in 

the field area include a thick sequence of west-dipping 

Cambrian and Precambrian carbonate and clastic rocks, a 

variety of mafic to silicic Tertiary volcanic rocks, two 

distinct intrusive stocks, and associated contact metamorphic rocks. The volcanic rocks have been hydrothermally 

altered in places, and some carbonate rocks adjacent to the 

volcanics have been bleached and recrystallized. One of the 

stocks is mineralized and exhibits intense hydrothermal 

alteration. 

Digital A VIRIS data were analyzed and interpreted in 

conjunction with field spectral data, and various data 

products were created that display the types and amount of 

compositional information present in A VIRIS data. These 

results were compared with results of related studies that 

evaluated other remotely sensed data collected over the 

Drum Mountains test site. These data sets included Landsat 

multispectral scanner (MSS) and thematic mapper (TM) 

data, Systeme Probatoire d'Observation de la Terre (SPOT) 

10-m panchromatic stereo data, and Thermal Infrared Multispectral Scanner (TIMS) data. 

This paper presents the significant results and current 

status of these ongoing geologic remote sensing studies by 

describing and illustrating both the breadth of geologic 

information and the unique compositional information routinely available from each sensor system tested. Incremental 

improvements in geologic information content correspond 

to advancements in sensor systems and are illustrated by 

using data products that include mergers of enhanced TM 

data and 10-m SPOT data in stereo format. 

Aeromagnetic and Gravity Studies of a Buried 

Porphyry Copper Deposit near CasaGrande, 

Arizona 

Viki Bankey and Douglas P. Klein 

The Casa Grande deposit (also known as the Santa 

Cruz deposit) is a buried porphyry copper deposit 7 mi 

west of the city of Casa Grande, Ariz. The prospect has 

been drilled in detail and ore was discovered between 1 ,000 

USGS Research on Mineral Resources-1989 Program and Abstracts 
and 2,000 ft below the surface in host rock consisting of 

Laramide porphyry intruded into Precambrian Oracle Granite. Diabase and other mafic dikes intrude the host rock. 

The deposit is similar to the Sacaton porphyry copper 

deposit located 6 mi northeast; both deposits are buried 

beneath alluvial cover and contain a host rock that consists 

equally of Precambrian granite and Laramide intrusive 

rock, unlike most porphyry copper deposits (Cummings, 

1982). Sacaton and CasaGrande may have been parts of a 

single hydrothermal system that was later separated by 

faulting. The CasaGrande deposit lies along the extension 

of a structural lineament called the Jemez zone that trends 

northeast from Sacaton to Globe, Ariz. 

Companies developing the deposit have proposed 

leaching the buried ore in place. The U.S. Geological 

Survey (USGS) and the U.S. Bureau of Mines are studying 

the geology and hydrology of the area to evaluate the 

environmental impact of the leaching technique and to 

prepare an ore deposit model. In support of the study, the 

USGS has recently flown two aeromagnetic surveys over 

the Casa Grande deposit: one flown 600 ft above terrain at 

1

h-mi spacing and the other flown 300 ft above terrain at 

1

/4-mi spacing. These data were modeled to determine the 

configuration of the basement and overlying basin. The 

Bouguer gravity anomaly data of the area were used to 

constrain the magnetic modeling. 

The aeromagnetic map flown 300 ft above terrain 

shows a magnetic low about 2 mi in diameter surrounding 

the deposit and a 20-nanoTesla (nT) high centered over the 

deposit. A 15-nT high, also inside the relative magnetic 

low, occurs 1 mi northeast of the deposit. These anomalies 

are partially obscured by a steep, 120-nT/mi, eastnortheast-trending gradient on the flanks of a 300-nT high, 

21/2-mi north of the deposit. The source of this northeasttrending, high-amplitude positive anomaly is hidden below 

alluvium. Our first task was to adequately remove this 

regional magnetic gradient to enhance the local anomalies. 

Several methods were compared, including (1) removing a 

two-dimensional surface calculated from the gridded aeromagnetic data by using orthogonal polynomials (USGS 

program SURFIT); (2) removing higher level aeromagnetic 

fields (such as the 600-ft field or upward continued fields) 

from the 300-ft magnetic field; and (3) removing a 120-

nT/mi southeast-dipping gradient. Mathematical enhancement of the residual and the total fields was performed; 

enhancement consisted of calculating the horizontal gradient to create a boundary map that has density contrasts 

outlined. These functions bring out features existing in the 

aeromagnetic data that are not readily apparent. 

The Bouguer gravity anomaly map was similarly 

analyzed to remove a regional gradient. The residual gravity 

anomaly map shows a 2-milligal high centered over the 

deposit. 

Interpretation of aeromagnetic data began by incorporating other information, such as geologic mapping from 

drill holes and gravity mapping. Magnetic profiles were 

selected from flight lines crossing the deposit and were 

modeled by using the USGS program SAKI (Webring, 

1985). 

REFERENCES 

Cummings, R. B., 1982, Geology of the Sacaton porphyry copper 

deposit, in Titley, S.R., ed., Advances in geology of the 

porphyry copper deposits: Tucson, University of Arizona 

Press, p. 507-521. 

Webring, Michael, 1985, SAKI: A Fortran program for generalized linear inversion of gravity and magnetic profiles: U.S. 

Geological Survey Open-File Report 85-122, 108 p. 

Regional Geochemical Studies of the AJO and 

Lukeville 1 o x 2° Quadrangles, Arizona 

Harlan Barton and Paul K. Theobald 

Regional geochemical studies were conducted during 

1979 and 1980 in mountain areas of the U.S. portions of the 

Ajo and Lukeville 1 o x 2° quadrangles, Arizona, except in 

the Papago Indian Reservation. Stream sediments were 

sampled at 971 localities within the 6,500-mi 2 study area. 

Sufficient heavy-mineral-concentrate sample for analysis 

was obtained from 952 of these localities. Sample sites were 

located on first- or second-order stream channels from 

drainage basins of less than 0.5 mi 2

; and generally these 

sites were located where dry stream channels emerged from 

the narrow linear mountain ranges. The sampling density in 

the mountain ranges was one sample locality per 1.2 mi 2

. 

Stream sediments were analyzed for 31 elements by optical 

emission spectroscopy in field laboratories. 

Maps are presented showing locations of anomalous 

concentrations of (1) ore and ore-related elements-Sb, Bi. 

Cu. Pb, Mo, Ag, W, and Zn; (2) elements common to 

gangue minerals-Ba, Mn, and Sr; and (3) Sr depletion 

associated with hydrothermal alteration. Sixteen areas having anomalous element concentrations are identified, and 

their geological and geochemical characteristics are 

described. 

The Mohawk Mountains anomaly is a cluster of 

sample localities having anomalous concentrations of lead, 

molybdenum, bismuth, and tungsten in heavy-mineral concentrates. One locality has anomalous molybdenum in a 

stream sediment. 

An elongate cluster of sample localities in the Agua 

Dulce Mountains has anomalous concentrations of bismuth 

and tungsten. Some also have low-level lead and molybdenum in heavy-mineral concentrates. The western part of the 

anomaly, underlain by Precambrian rocks, is bismuth rich, 

whereas the eastern part is molybdenum rich. In addition to 

2 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
these elements, the area is rich in thorium, niobium, and 

other rare-earth elements, all characteristic of a granitophile 

assemblage. 

Sample localities from the low hills to the north of La 

A bra Plain have anomalous concentrations of molybdenum, 

tungsten, and, less frequently, lead. The anomaly is best 

reflected by molybdenum in stream sediment where extensive overlap from the Sonoyta Mountains anomaly is 

subdued. 

The tight cluster of sample localities in the Booth 

Hills has anomalous concentrations of Bi , W, Pb, Mo, Th, 

Nb, and , in some localities, Sn. The anomaly is in an area 

of gneiss and granite of uncertain age and may reflect a late 

magmatic concentration of metals. 

The copper anomaly in the vicinity of Growler Pass is 

reflected in normalized data for both sample media. The 

area also has anomalous concentrations of Pb, Mo, Bi, W, 

Cu, Sb, and Sn, but Sr is found in abnormally low amounts. 

The assemblage of elements suggests erosion into the 

middle or upper levels of a hydrothermal system. 

Heavy-mineral concentrates throughout the Sauceda 

Mountains are anomalously rich in manganese. Two localities have anomalous antimony , and localities at the northwest end of the mountains are anomalous for barium and 

strontium. The area has the largest tin anomaly in the 

quadrangle . 

The Sonoyta Mountains anomaly is strongly reflected 

in the distribution of antimony and silver, includes one of 

the few sites that has anomalous zinc, and has abnormally 

low strontium, which suggests widespread depletion during 

hydrothermal alteration. 

The intense copper anomaly at Ajo is a direct reflection of the deposit at the New Cornelia mine. It is a zoned 

anomaly, and molybdenum is confined to the center of a 

larger lead anomaly that overlaps with copper. Anomalous 

concentrations of bismuth and tungsten occur locally. The 

anomaly is of interest primarily for comparative purposes. It 

provides a measure of the composition size and intensity of 

anomalous values in the vicinity of the known deposit at the 

New Cornelia mine. 

A number of localities in the western part of the 

Maricopa Mountains have anomalous concentrations of W, 

Bi , Pb, Mn , andY. The anomaly is closely associated with 

the outcrop area of Precambrian granite and most likely 

reflects a hydrothermal event superimposed upon the granite. 

Sample localities anomalous for copper are in the 

vicinity of Mohawk Pass. Secondary copper minerals in 

these samples are derived from vein-type deposits in the 

Mohawk mining district; these deposits also contain anomalous concentrations of tungsten, molybdenum, bismuth, 

and lead. 

The Painted Rock Mountains anomaly is a cluster of 

sample localities having anomalous lead and molybdenum 

in stream sediment and lead in heavy-mineral concentrate. 

Left to right: Richard Henley (Australia), Charles Cunningham (USGS), Alan Wallace (USGS), and Andre Panteleyev 

(Canada) prepare to go underground to visit a newly 

discovered, rich vein of silver at Cerro Rico, Potosi, 

Bolivia. 

The area is also rich in manganese, barium, and strontium, 

and, at one locality, copper. Veins containing barite and a 

variety of lead and molybdenum minerals have been mined 

in the Painted Rock district. 

The copper anomaly in the Ajo Range is represented 

by normalized anomalous sites. The prominent northwest 

trend of this anomaly is well displayed in the distribution of 

anomalously high concentrations of lead , molybdenum, 

silver, and tin and anomalously low concentrations of 

strontium, a common feature of hydrothermally altered 

zones. The general nature of the anomaly suggests remobilization of metals from older rocks beneath exposed volcanic rocks along a major northwest-trending structural zone. 

The copper anomaly in the Batamote Mountains is 

second only to the Ajo anomaly in intensity and has a larger 

areal extent. The Batamote anomaly is isolated from the Ajo 

anomaly by an unsampled alluvial plain. Hence, it might 

appear to reflect a northern extremity of the Ajo anomaly. 

Although isolated anomalous concentrations for volatile 

elements and base metals have been observed in the general 

area , the anomaly is best characterized by copper. The 

Batamote Mountains are a broad, dissected shield volcano 

of late Tertiary age resting on latites of similar age. Both of 

these lithologies are younger than the mineralization at Ajo; 

hence, the Batamote anomaly cannot be directly related to 

the deposit at Ajo. 

Scattered localities in the Cabeza Prieta and adjacent 

Tule Mountains are rich either in zinc or silver. Several 

other localities are weakly anomalous for either molybdenum or the assemblage of tungsten , molybdenum, and lead. 

Barium and strontium enrichment are probably related to a 

granite intrusion rather than to the hydrothermal mineral 

occurrences suggested by the other elements. 

USGS Research on Mineral Resources-1989 Program and Abstracts 3 
A single anomalous copper value in stream sediments 

and several normalized anomalous copper values in both the 

stream sediments and heavy-mineral concentrates were 

found in the Copper Mountains. Two of these heavymineral concentrates were also weakly anomalous for lead . 

In samples from the low hills along State Highway 84 

in the northeast comer of the Ajo quadrangle , heavymineral concentrates are manganese rich, and stream sediments are strontium poor. The area is anomalous for Pb, Bi, 

Th, La, Y, and , locally, W. The thorium, lanthanum, and 

yttrium association suggests a relation to the Precambrian 

granites exposed in the area , whereas the other elements 

suggest late magmatic or hydrothermal concentration of 

selected elements. 

Genetic Model for the Carbonate-Hosted PbZn-Cu-Ag-Au Manto-Chimney Deposits of the 

Gilman, Colorado District, Based on Fluid 

Inclusion, Stable Isotope, Geologic, and FissionTrack Time-Temperature Studies 

D.W. Beaty, C.G. Cunningham, C.W. Naeser, and G.P. 

Landis 

Multidisciplinary studies have resulted in the development of a comprehensive genetic model for the carbonatehosted Pb-Zn-Cu-Ag-Au manto-chimney deposits of the 

Gilman, Colo. district. These deposits, located in the 

Colorado mineral belt, are some of the best examples of this 

type of deposit in the world . The model has direct application for both resource assessment and exploration. 

The composite evidence shows that both the mantos 

and chimneys of the main sulfide ore deposits formed 

during the mid-Tertiary from a high-temperature, igneousrelated, hydrothermal source. There may have been a 

poorly preserved silver-lead-zinc precursor event. The mineralizing event that formed the main orebodies has been 

dated by fission tracks at 34.5±2.6 Ma on late-stage 

hydrothermal apatite from the chimneys. A large, districtwide, paleothermal anomaly of the same age surrounds and 

is centered on the orebodies. Sulfur isotope data show a 

homogeneous sulfur source for the main orebodies. Bulk 

o34S= + 1.6 and indicates an igneous provenance. Lead 

isotopic ratios in the ore are indistinguishable from those of 

Tertiary igneous rocks throughout western Colorado. The 

components of the manto and chimney orebodies were 

transported by a hydrothermal fluid having o 180= +4 to +8 

and oD=- 55 to -75 per mil; this hydrothermal fluid is 

inferred to be magmatic water. The fluid had a mean 

salinity of about 5 weight percent equivalent NaCl and a 

range of 1.5 to 9.4. Fluid inclusion and sulfur isotope 

fractionation data indicate that sulfide deposition in the 

chimney deposits took place at temperatures of about 390 to 

410 °C. Lower temperatures were determined for the No. 1 

Fracture Zone? 

100 200 

METERS • . Concealed , • 

. ·.·.Stock 

Figure 1. Paleohydrology of the carbonate-hosted PbZn-Cu-Ag-Au manto-chimney deposits at Gilman, Colo. 

[Beaty and others abstract] 

Manto (300-375 °C), for veins in the Sawatch Quartzite 

(230-370 °C), for late-stage apatite in vugs within the 

chimneys (309 °C), and for veins cutting Precambrian rock 

beneath the chimneys (174-306 °C, and a mean of240 °C). 

Fluid movement during the ore-forming event is delimited 

by the distribution of fluid-inclusion temperatures, partial 

fission-track resetting , ore mineral assemblages, alteration 

mineral assemblages, and oxygen isotope exchange patterns 

in the orebodies and surrounding country rocks. Fluids 

moved updip within the Sawatch Quartzite from a source 

located to the northeast of the present deposits, then 

upsection through the chimneys to the Leadville Dolomite 

(an important aquifer), and then updip through the mantos 

where they ponded against the Pando Porphyry (fig. 1). 

Several small, paragenetically early, partially preserved 

silver-lead-zinc deposits at Gilman and Red Cliff are of 

uncertain origin. 

Fluid Inclusion and Mineralogic Studies of a 

Palladium-Platinum Anomaly Zone in the 

Reeser's Summit Diabase, Pennsylvania: 

Evidence for Hydrothermal Transport 

Harvey E. Belkin 

The York Haven diabase sheet, of Early Jurassic age, 

crops out near the northern margin of the Gettysburg basin 

across the Susquehanna River south of Harrisburg, Pa. 

Gottfried and Froelich (1988), in a comprehensive study of 

mafic rocks in the Eastern United States Mesozoic basins, 

have defined a palladium and platinum anomaly associated 

with a ferrogabbro zone at Reeser's Summit, Pa. (Gottfried 

and others, this volume). The Reeser's Summit exposure 

consists of a 500-m section that has chilled margins characteristic of a high-titanium ( 1.1 weight percent) quartz4 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
A microscopic view of fission tracks in apatite crystals. These tracks, formed mostly by the spontaneous fission of 238U, 

can be used to determine the age and extent of a paleothermal anomaly. [Beaty and others abstract] 

normative tholeiitic magma of the York Haven type (Gottfried and Froelich , 1988). The chilled margins contain 

typical platinum group element (PGE) abundances (Pd= 10 

ppb , Pt= 10 ppb), whereas the greatest anomaly in the 

90-m-thick ferrogabbro zone (Fe010,a1 up to 18 weight 

percent) contains Pd= 165 ppb and Pt=21 ppb. Associated 

with this zone are anomalously high contents of gold (up to 

54 ppb), tellurium (up to 20 ppb), and chlorine (up to 0.44 

weight percent) (Gottfried and others, 1988). 

A detailed petrographic , microprobe, SEM, and fluid 

inclusion study has been conducted to define the enrichment 

and transport processes that have operated in this system. A 

model is suggested whereby an original ferrogabbro has 

been hydrothermally altered by late-stage aqueous chlorinesulfide-arsenic solutions, especially enriched in iron, that 

have deposited PGE elements associated with copper sulfides. 

The initial diabase contained a relatively simple 

mineralogy of plagioclase, clinopyroxene, and opaques. 

The plagioclase composition (cores) ranges from An80 to 

An85 at the exposure margins to An55 to An60 in the 

ferrogabbro. The clinopyroxene composition (cores) ranges 

from En60Fs 15Wo25 at the exposure margins to 

En34Fs41 Wo25 in the ferrogabbro. Both plagioclase and 

clinopyroxene are zoned; the plagioclase rims range to 

An20, and the clinopyroxene rims range to En27Fs49-

Wo24. The alteration is predominately characterized by 

destruction of the clinopyroxene with concomitant crystallization of iron-rich amphibole and chlorite. The amphiboles are halogen rich (up to 2.00 weight percent chlorine). 

Brown hornblende tends to occur as single crystals, whereas 

green ferroactinolite is usually an alteration product of 

clinopyroxene. The plagioclase is relatively unaltered. 

Myrmekitic-pegmatitic intergrowths of quartz, K-feldspar, 

albite , and halogen-rich apatite are common and increase in 

abundance to a maximum in the anomalous ferrogabbro 

zone. 

Chalcopyrite is the most abundant sulfide and is 

always associated with chlorine-rich amphibole, quartz , or 

ilmenite. The texture suggests that chalcopyrite was a very 

late phase . No primary magmatic sulfides have been recognized . Bornite, galena, and sphalerite typically occur 

with chalcopyrite. Intimately associated with the chalcopyrite, adjacent to chlorine-rich amphibole or quartz, are very 

small grains of Pd+Co+Ni±Fe±S arsenides. Microprobe 

and energy dispersive SEM analysis suggests that the 

chalcopyrite contains dissolved platinum and gold. 

USGS Research on Mineral Resources-1989 Program and Abstracts 5 
Figure 1. Primary fluid inclusion in quartz from Reeser's 

Summit, Pa. , sample PYRS84-9, containing a bubble, a 

cubic daughter crystal (chloride), and concentrated brine. 

[Belkin abstract] 

Primary fluid inclusions (fig. 1) in quartz commonly 

contain daughter crystals of an iron-rich chloride (SEM) and 

are coeval with primary gas inclusions. Secondary inclusions are abundant, especially in the quartz and plagioclase. 

Microthermometry yields homogenization temperatures (no 

P correction) for the primary inclusions that range from 500 

to 600 °C and from 300 to 400 oc for the secondary 

inclusions. The melting and volume relations of the cubic , 

isotropic daughter crystals suggest a salinity of 2:40 weight 

percent NaCl equivalent. The quartz-sulfide texture suggests that primary fluid inclusions and sulfides formed 

during the same process. 

The evidence suggests that a hydrothermal system 

developed, probably commencing during late magmatic 

crystallization, and that the system introduced halogen-rich , 

sulfide-arsenic aqueous solutions. The Reeser's Summit 

anomalous PGE zone is the result of deposition by these 

hydrothermal solutions. 

REFERENCES 

Gottfried , David, and Froelich, A.J. , 1988, Variations of palladium and platinum contents and ratios in selected Early 

Mesozoic tholeiitic rock associations in the Eastern United 

States: U.S. Geological Survey Bulletin 1776, p. 332- 341. 

Gottfried , David, Aruscavage , P.J. , and Rail , Norma , 1988 , 

Fractionation of palladium and platinum in a Mesozoic 

diabase sheet, Gettysburg basin, PA: V.M. Goldschmidt 

Conference , Program and Abstracts, p. 44. 

Geoelectric Studies in the Delta, Utah, 

Quadrangle 

D.L. Campbell and V.F. Labson 

Magnetotelluric (MT), audiofrequency magnetotelluric (AMT), and direct current vertical electric soundings 

(YES) were used during the past three field seasons of 1986 

to 1988 to help with the mineral assessment of the Delta, 

Utah , I o x 2° CUSMAP (Conterminous United States 

Mineral Assessment Program) quadrangle. MT and AMT 

soundings were made to study the geoelectric character of 

Desert Mountain, Keg Mountain, Drum Mountains, Thomas 

Range , Notch Peak , Fish Springs Range, and Baker Hot 

Springs Butte. YES were used to map the thickness of 

sediments in the Tule Valley and northern Fish Springs Flat. 

Most Cenozoic sedimentary rocks and porous tuffs in 

the quadrangle have low resistivities (2-40 ohm-m), Paleozoic sedimentary rocks and most Tertiary volcanic rocks 

have intermediate resistivities (20- 200 ohm-m) , and Tertiary and Jurassic intrusive rocks have high resistivities 

(100-5,000 ohm-m). The geoelectric profiles show that 

Desert and Keg Mountains have central high resistivity 

plugs that extend to depths of at least 10 km. These plugs 

probably are composed of Oligocene intrusive rocks that 

crop out at the surface. Their great depth suggests that the 

post-Miocene extension along the 2.5-km-deep Sevier 

Desert detachment fault, seen in nearby seismic profiles, 

did not take place below those mountains; their intrusive 

cores may have acted as rivets to hold upper and lower 

plates together. 

MT soundings at Notch Peak show that about I km of 

high resistivity material, probably Notch Peak granite, 

overlies at least 5 km of 40 ohm-m material, presumably 

Paleozoic country rocks. The Jurassic Notch Peak granite is 

either a laccolith or was truncated at depth by Cretaceous or 

Tertiary movement on Sevier Desert detachment fault(s) . 

The MT results also suggest that very conductive , possibly 

mineralized, zones border the Notch Peak granite to the 

northeast and east. Magnetic data indicate another intrusive 

body at greater depth, offset about 2 to 5 km to the south of 

the outcrop area of the Notch Peak granite . 

Other MT and AMT work in the quadrangle (1) has 

clearly characterized the boundary of the Thomas caldera 

along a profile crossing the western boundary , (2) is 

consistent with geologic evidence that another caldera may 

extend from the eastern edge of Desert Mountains to a point 

east of Cherry Creek, and (3) implies that the Baker Hot 

Springs basalts are not present in any substantial thickness 

below the adjacent surficial sediments just east of their 

outcrop area. The MT and AMT work also shows up to 5 

km of possible Cenozoic sedimentary rocks in the preBonneville basin north of the Keg-Desert Mountain axis but 

only about 3 km of such materials in the area just south of 

that axis. 

Geoelectric , borehole , and seismic data were used to 

constrain estimates of thickness of sedimentary fill in 

valleys at more than 100 sites in the quadrangle. These 

thicknesses were then used to calibrate estimated depth to 

basement throughout the quadrangle by using gravity data . 

The results show that several valleys contain broad buried 

6 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
pediments that have relatively thin sedimentary veneer. The 

locations and extents of such pediments are significant for 

mineral assessment purposes because of the possibility of 

covered shallow mineral deposits. 

Tectonic and Magmatic Development of the 

Midcontinent Rift: A Synthesis of New Seismic, 

Chemical, and Isotopic Data 

W.F. Cannon, S.W. Nicholson, and Alan Green 

The Midcontinent rift, the host for major resources of 

copper, nickel , and other metals, formed during a period of 

crustal extension about 1.1 Ga. The structure extends 2,000 

km from Kansas, through the Lake Superior region and into 

southern Michigan. The rocks within the rift, the 

Keweenawan Supergroup, are exposed only around Lake 

Superior where we have concentrated our study. We present 

a refined model of rift evolution that can be used to place 

known mineral deposits into a geologic framework and 

establish a geologic basis for predictive metallogeny. 

Development of the rift occurred in three stages: 

(I) From about 1.108 to 1.094 Ga, the Archean and lower 

Proterozoic crust was extended and greatly attenuated 

to one-fourth or less of its original thickness of about 

40 km. Copious volumes of flood basalt and smaller 

amounts of andesite and rhyolite were erupted into 

the developing rift depression. Earliest rift deposits 

accumulated in a broad (about 200 km wide) depression formed mostly by sagging during initial stages of 

crustal attenuation. Magmatism was widespread to 

form both "plateaus" of flood basalt and diabase 

dikes, some of which extend more than 100 km 

beyond the rift. Upon further extension, a central 

graben developed over highly attenuated crust that 

locally may have totally separated. Enormous volumes of basalt, up to 20 km thick, were erupted in the 

graben; the earlier formed flanks remained as topographic highs. Composition of basalts reflects the 

condition of the crust through which they were 

erupted and varies both with position in the rift 

system and with time. Basalts outside the central 

graben have evolved compositions and strong enrichment of incompatible trace elements. Neodymium 

isotope compositions reflect some crustal contamination . This magma formed from a relatively homogeneous and widespread mantle source and was erupted 

through a still thick crust lacking well-developed 

magma conduits. As the crust thinned and central 

magma conduits developed, basalt compositions 

evolved toward more primitive values, and neodyFlanking basin Central graben (structural horst) Flanking basin 

Post·rift Sediments 

Basalt: later/earlier 

Diabase dikes: later/earlier 

Underplated and related crustal mafic Intrusions 

Archean and Lower Proterozoic rocks 

Figure 1. Schematic cross section of the Midcontinent rift in the Lake Superior region based on geologic data 

and seismic reflection and refraction data. Approximate width of section is 300 km. Early basalts fed by 

widespread dikes form a broad apron gradually thickening toward the center of the rift. Later basalts are confined 

mostly to a central graben and were probably fed by much more centralized dikes tapping a magma reservoir near 

the base of the crust. Postrift sediments are in a broad basin formed mostly by thermal collapse of the crust 

during cooling. The central graben was converted to a central horst by reactivation of the graben-bounding 

normal faults into high-angle reverse faults. [Cannon and others abstract] 

USGS Research on Mineral Resources- 1989 Program and Abstracts 7 
Figure 1. View of a block of rare-earth-rich ore from the Bayan Obo deposit of Inner Mongolia, China. Blebs of hematite 

(h) are surrounded and metasomastically replaced by lamellae (m) of an assemblage of very fine-grained monazite, 

aege rine , and bastnaesite . The field relation shown here indicates that the episode of hematite mineralization preceded 

that of the rare-earth mine ralization . [Chao and others abstract] 

mium isotopes showed little or no crustal contamination. Major intrusive bodies, such as the Duluth 

Complex, were emplaced during this extensional 

phase. 

(2) At about 1.094 Ga , extension and basaltic volcanism 

ended. Thermal collapse of the crust formed a broad 

basin in which flu vial and minor lacustrine deposits 

accumulated to thicknesses of about 10 km. Igneous 

activity was restricted to formation of a few andesitic 

stratovolcanoes at about 1.086 Ga. 

(3) The central graben of the rift was uplifted, in places 5 

km or more. Most uplift was accommodated along 

the original graben-bounding normal faults that were 

transposed into high-angle reverse faults. 

The combined effect of these three phases leads to the 

geometry shown in figure 1, where a central horst, originally the central graben, contains huge volumes of basalt 

and overlying sediments. Flanking basins contain thinner 

basalt sequences dominated by the older part of the basalt 

section and a riftward thickening wedge of sediments. 

The H8 Dolomite Host Rock of the Bayan Obo 

Iron-Niobium-Rare-Earth-Element Ore Deposit of 

Inner Mongolia, China-Origin, Episodic Mineralization, and Implications 

E.C.T. Chao, j.A. Minkin, j.M. Back, P.M. Okita, Edwin 

H. McKee, R.M. Tosdal, M. Tats umoto, Wang junwen, 

C.A. Edwards, Ren Yingzhen , and Sun Weijun 

The giant Bayan Obo ore deposit of Inner Mongolia 

occurs geologically in the H8 dolomite of the middle 

Proterozoic Bayan Obo group. Recent fie ld and laboratory 

in vestigations show that the H8 dolomite marble is not an 

igneous carbonatite but a metamorphic rock of sedimentary 

origin. Stratigraphically, the H8 dolomite is conformable 

with the H9 black shale-slate above and with the H7 

interbedded mica schist, slate , and marble below. It exhibits 

sedimentary features and structures such as quartzite interbeds and crossbedding and contains detrital quartz and rare 

oncolite algal fossils (microstromatolites) . The H8 consists 

8 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
1 em 

Figure 2. Hand sample of a banded iron-rare-earth ore sample from the Bayan Obo deposit of Inner Mongolia, China. 

Ptygmatic microfolds in banded hematite (h), fluorite (f), and monazite (m) clearly indicate that this ore was formed prior 

to the regional metamorphism that probably occurred in Hercynian time. [Chao and others abstract] 

of a fine-grained and a coarse-grained crystalline dolomite, 

both of similar ferroan mineral composition. Oxygen and 

carbon isotope data also indicate that the H8 dolomite is of 

sedimentary origin. modified by regional metamorphism. 

The Pb-Pb and Sm-Nd model ages for early monazites in the H8 dolomite range from 1.4 to 1.8 Ga. Textural 

evidence shows that such monazites within the H8 dolomite 

are not detrital but hydrothermal in origin. Preliminary 

Th:Pb ages suggest that two episodes of monazite mineralization may be represented in the disseminated monazitebearing dolomite ores (in excess of 2 weight percent 

rare-earth-element (REE) oxide). The first episode may 

have occurred as early as 840 Ma (late Proterozoic), 

followed by a later episode at about 695 Ma. Thus the 

Bayan Obo ore deposit is not syngenetic but epigenetic in 

origin. 

The two early episodes of monazite mineralization 

were followed by disseminated and banded magnetite mineralization, then hematite mineralization. The iron oxide 

mineralization was then followed by deposition of 

monazite-bastnaesite ores. These high-grade REE and ironREE ores are extremely fine grained (mostly less than 50 

fl.m), with the exception of magnetite (average grain size of 

about 100 f!.m). These ores are finely laminated, are 

discontinuously banded, and exhibit widespread metasomatic replacement textures (fig. I). Later REE mineralization produced coarser grained monazite, bastnaesite, 

aeschynite (a REE niobate), huangheite (a barium-REE 

fluorocarbonate), and associated aegerine. This coarser 

grained episode of REE mineralization is dated by Th:Pb 

and Sm:Nd isochron methods to be about 430 Ma, or 

Caledoni an in age; this age implies that the principal 

episodes of Bayan Obo mineralization are pre-Caledonian. 

The principal banded iron-REE ores of Bayan Obo 

were then regionally metamorphosed and microfolded (fig . 

2) at about 300 Ma (based on potassium-argon age of biotite 

in biotite schist) , probably succeeded by the intrusion of 

Hercynian biotite granite (potassium-argon age, 265 Ma), 

which is widespread in the mine region. Unmetamorphosed 

late-stage mineralization involving iron oxides and REE's 

followed. This mineralization was associated with sulfides 

(pyrite, pyrrhotite, sphalerite, galena), K-feldspars, silica, 

microcline pegmatites, and numerous crosscutting calcite 

veins. 

So far, textural and mineralogical studies indicate that 

episodes of REE and iron mineralization are both of 

hydrothermal origin but are unrelated. Based on the results 

to date , it appears that two types of Bayan Obo ores exist 

USGS Research on Mineral Resources-1989 Program and Abstracts 9 
and thus further exploration in adjacent regions for the 

occurrence of ores containing REE' s only, independent of the 

iron oxide, should be considered. 

Geology and Geochemistry in the Vicinity of the 

Adelaide Crown Mine, Humboldt County, 

Nevada 

Theresa M. Cookro and Ted G. Theodore 

The Adelaide mining district, located about 16 km 

south of the town of Golconda, Nev., produced Au, Ag, 

Cu, Pb, and Zn. The sampled area is in the western part of 

the district where the Gold Run Creek placer mine is 

currently in operation, and stripping of a new gold deposit 

just north of the Adelaide Crown mine has just been started 

by Getchell Resources and Icarus Exploration Co. in a joint 

venture. Evidence of (sinter, tufa, and pods of black earthy 

oxides) ancient hot springs occurs along the mineralized 

north-trending fault system. Altered rock near the sinter and 

tufa occurrences has a porcelainlike appearance and oxide 

coatings of iron manganese. Cinnabar, orpiment, and realgar occur in the crusts with the oxides. The black oxides are 

extremely rich in manganese and carry anomalous concentrations of silver and arsenic. The tufa is also anomalous in 

manganese, silver, and arsenic. Silicified veins of calcite 

and barite also are common. Altered dikes of intermediate 

composition cut the host rock. Finally, a trace element 

assemblage of As, Sb, Hg, Tl, Au, and Ag is common in 

these rocks, as in many other sediment-hosted epithermal 

precious-metal deposits in north-central Nevada. Gold, 

hosted in the Cambrian Preble Formation, occurs in quartz 

veins, in quartz-filled vugs, associated with manganeseand iron-rich oxides, and on fracture surfaces of the rock. 

Gold occurs in spot anomalies, whereas silver apparently is 

more consistently anomalous across wide areas. 

Several open cuts and clusters of underground workings, active in the late 1930's and early 1940's, along a 

prominent, steeply dipping, gold-silver-bearing, northstriking system of faults constitute the historic Adelaide 

Crown mine. Both deposits are apparently epithermal, and 

much of the ore is in jasperoid. To the west of this 

precious-metal-bearing fault system is a prominent thrust 

fault, speculated to correlate with the Roberts Mountains 

thrust. This thrust brings the allochthonous Valmy Formation, of Ordovician age, in contact with parautochthonous 

transitional assemblage limestone and phyllite of the Preble 

Formation. The thrust does not appear to be mineralized. 

Thus, these deposits exhibit characteristics of both sedimenthosted and hot-springs types of precious-metal deposits as 

currently defined. 

Elsewhere in the district, the Preble Formation is 

strongly silicified and argillized along major strands of 

faults. Thin (average less than 8 em in thickness), discontinuous stockwork quartz veins are prominent; the veins are 

discontinuous mainly because of several stages of postmineral movement along the faults. Some quartz coatings and 

veins are gray to bluish-gray in color. Red jasper and gray, 

red, and blackjasperoid are common. Both the quartz veins 

and jasperoid are anomalous in silver, arsenic, and manganese. 

Finally, some mafic dikes cut the epithermal gold 

mineralization and are associated with anomalous chromium, nickel, cadmium, and cobalt concentrations. A 

nearby Cu-Pd-Zn-W skarn, the Adelaide mine, contains 

anomalous concentrations of gold within the massive sulfide rock and in phyllite around the margins of the skarn. 

The deposits in the district may represent an extension of 

the gold-enriched Getchell trend that occurs about 40 km to 

the north. 

Methodology for Analysis of Concealed Mineral 

Resources in Nevada: A Progress Report 

Dennis P. Cox, Steve Ludington, Maureen G. Sherlock, 

Donald A. Singer, Byron R. Berger, Richard J. Blakely, 

John C. Dohrenwend, Donald F. Huber, Robert C. 

Jachens, Edwin H. McKee, Christopher M. Menges, 

Barry C. Moring, and Joe Tingley 

Maps (1: 1,000,000 scale) showing areas in Nevada 

permissive for undiscovered mineral deposits by type and 

an estimate of the number of undiscovered deposits are 

being compiled by a team of U.S. Geological Survey and 

Nevada Bureau of Mines and Geology geologists, geophysicists, and geochemists. Results will be shared with the 

U.S. Bureau of Mines for an economic analysis. Permissive 

areas on these maps are defined as containing geologic 

environments in which one or more mineral deposit models 

may occur and include those areas in which possible host 

rocks are concealed but are present within 1 km of the 

surface. The resource delineation maps will be included in 

a folio showing data used in their preparation. The folio will 

include ( 1) maps and tables classifying approximately 500 

deposits by deposit model, (2) grade and tonnage models 

appropriate to Nevada, (3) maps of regional geology and 

geochronology of igneous rocks, and (4) maps of gravity 

and magnetic data and their interpretation. These data will 

be used to prepare derivative maps that show ( 1) areas 

covered by up to 1 km of Cenozoic rock and sediments, (2) 

shallow magnetic sources, (3) neotectonic analysis, (4) 

subsurface basin geometry, and (5) the subsurface distribution of Mesozoic and Tertiary intrusions, Tertiary volcanic 

rocks, and certain pre-Tertiary sequences of sedimentary 

and volcanic rocks. The last-named maps show the total 

area of the State in which rocks permissive for certain 

stratabound deposit types (Cyprus, kuroko, and Besshi 

massive sulfide; sedimentary exhalative zinc-lead-silver; 

bedded barite; Appalachian zinc; and Kipushi copperlead-zinc) are present within the upper 1 km of the crust. 

Considered permissive for epigenetic igneous-related 

10 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Landsat Thematic Mapper image of Lake Tahoe, Nev. Remote sensing data are being used to map hydrothermal ly altered 

rocks and to do a regional structural analys is in the Reno, Nev., 1° x 2° CUSMAP quadrangle. 

deposits are volumes of rock , I km thick, containing 

permeable and (or) reactive rocks within l 0 km of a 

plutonic body or within 5 km of a subvolcanic intrusion or 

caldera margin . 

Oxygen Isotope Map of the Fossil Hydrothermal 

System in the Comstock lode Mining District, 

Nevada 

Robert E. Criss , Duane E. Champion, and Mary F. Horan 

Oxygen isotope measurements on 200 samples of 

volcanic rocks from outcrops, drill cores, and mine workings in the Virginia City area, Nevada, provide unequivocal 

evidence that the regional propylitization and local argillization and silicification near veins were produced by 

interactions with low 180 fluids derived from meteoric 

waters. A contour map (fig. l) of o 180 values from outcrops 

reveals that fluid -rock exchange produced an equant, 75-

km2, low 180 zone centered on Mount Davidson that 

includes the Comstock, Silver City, and Occidental Lodes; 

a smaller, spatially distinct low 180 zone occurs in the 

Flowery mining district to the east. Subsequent dip-slip 

movement on the Comstock fault displaced the 18

0 anomaly and allowed preservation of a tongue of downdropped , 

higher 18

0 rocks in the hanging-wall near Virginia City. 

USGS Research on Mineral Resources-1989 Program and Abstracts 11 
Lode mining in the Comstock mine, Virginia City, Nevada, 1868. T.H. Sullivan took this first photograph in a mine 

by igniting magnesium wire to obtain sufficient light. 

12 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Figure 1. Contour map of 8180 values (dots) from i termediate composition volcanic rocks of the Coms ock 

Lode mining district. Contour interval is 3 per mil. [ riss 

and others abstract] 

Analyses of subsurface samples (not shown in fi . 1) 

collected 100 years ago by G. Becker and others, 

curated by the Smithsonian Institution and the U.S. eological Survey, allow a 6-km long traverse into the ~ ssil 

hydrothermal system along the level of the famous utro 

Tunnel, approximately 500 m below the present sur ace. 

Unaltered rocks (8180= +6 to +8) extend westward rom 

the tunnel mouth for about 2 km. A narrow transitional one 

of steep 180 gradient, extending from 2 to 3 km fro the 

tunnel mouth, marks the perimeter of the hydrothe mal 

system and directly underlies the Flowery Range. Fin lly, 

intensely altered rocks (8180= -4 to +0) extend west ard 

to the tunnel terminus near the Comstock fault to 6 km· this 

last zone includes both the Comstock and Occidental L des. 

Alteration within this part of the hydrothermal syste is 

truly pervasive, such that the 8180 values exhibit ittle 

dependence on either rock type or evident proximit to 

structures. In this vertical section, low 180 rocks und rlie 

higher 180 outcrops of the downdropped hanging-wall. his 

relation demonstrates the existence of a steep vertical 180 

gradient, which is also indicated by analyses of rocks 

the Combination Shaft. 

The uniform character of the zone of intense 

ation and its smooth transition to unaltered rock at dist nee 

indicates that the Comstock hydrothermal system was a 

coherent geographic entity. However, as in the epithe al 

mining districts of Bohemia, Oreg., and Yankee ork, 

Idaho, no single intrusion at Comstock has sufficient ass 

(by a factor of 1 0-lOOX, judging from the outcrop siz ) to 

have produced the 75-km2 low 180 zone. Although uch 

larger hypabyssal intrusions may exist in the sh llow 

subsurface in all of these districts, it is much more rkely 

that these low 180 zones represent the roots of stratov leanoes. Remnants of these volcanoes are present as the ate 

Peak Formation, as demonstrated by similar ages of lode 

mineralization and time of eruption of the typically unaltered volcanics (Vikre and others, in press). Fluid convection, driven by successive pulses of magma through a locus 

of volcanic centers, could account for the broad and 

uniform field of intensely altered rocks. 

REFERENCE 

Vikre, P.G., McKee, E.H., and Silberman, M.L., in press, 

Chronology of Miocene hydrothermal and igneous events 

in the western Virginia Range, Washoe, Storey, and Lyon 

Counties, Nevada: Economic Geology. 

Geological Studies of the International Falls and 

Roseau 1 o x 2° CUSMAP Quadrangles, Northern 

Minnesota 

W.C. Day, T.L. Klein, D.L. Southwick, and K.J. Schulz 

Mapping, geochemical, geophysical, and drill core 

studies in the International Falls and Roseau 1 o x 2° 

quadrangles of northern Minnesota have provided new 

insights into the geologic evolution and the mineral resource 

potential of the Late Archean terrane. Basement exposure is 

good in the eastern part of the International Falls quadrangle. Where westward-thickening Quaternary glacial deposits obscure bedrock in the Roseau quadrangle, drill core 

studies and aeromagnetic and gravity data were used to 

establish the regional geologic framework. 

The study area straddles the Minnesota-Ontario border and lies within the southern part of the Superior 

province of the Canadian Shield. The Superior province is 

composed of several northeast-trending subprovinces of 

alternating granite-greenstone and metasedimentary-gneiss 

lithotectonic terranes. The study area includes three of these 

major lithotectonic terranes: the Wabigoon in the north, 

the Quetico in the central part, and the Wawa-Shebandowan 

in the south. 

The Wabigoon subprovince is a granite-greenstone 

terrane composed of low- to moderate-grade regionally 

metamorphosed volcanic and coeval plutonic rocks and 

volcaniclastic, epiclastic, and chemical sedimentary rocks. 

The supracrustal rocks were complexly deformed and 

intruded by large volumes of syn- to posttectonic granitoids. 

In the eastern part of the Wabigoon subprovince in the 

International Falls quadrangle, volcanism was bimodal. The 

mafic suite consists of low- and high-Ti02 tholeiitic metabasalts, metagabbro, and minor calc-alkaline basaltic 

metaandesite, and the felsic suite includes both low-Al20 3 

tholeiitic metadacite and metarhyolite, and high-Al20 3 

calc-alkaline metarhyolite and comagmatic tonalite. To the 

west in the Roseau quadrangle, andesitic volcanism is more 

prevalent; tholeiitic metabasalt and metaandesite are comUSGS Research on Mineral Resources-1989 Program and Abstracts 13 
monly interlayered with calc-alkaline metaandesite, metadacite, and metarhyolite. Stratiform massive sulfide occurrences, some having enrichments up to 5 percent combined 

base metals (zinc>copper>lead), are spatially associated 

with bimodal volcanic rocks. Copper-nickel sulfide mineralization occurs in the basal parts of some synvolcanic 

tholeiitic metagabbro sills. In addition, epigenetic gold 

deposits occur mostly in dilation zones associated with 

major shear zones caused by regional wrench tectonics. 

These shear zones form, in part, subprovince boundaries. 

The Quetico subprovince is a medium-grade, regionally metamorphosed metasedimentary rock and gneiss terrane. The northern part of the terrane is composed of a belt 

of graywacke that grades southward into rocks of the 

Vermilion granitic complex. The Vermilion complex is a 

granite-migmatite terrane consisting of supracrustal rocks 

that have been intruded by batholithic tonalite, monzodiorite, and granite bodies of the Lac La Croix Granite. No 

mineral deposits are known to occur in rocks of the Quetico 

subprovince in Minnesota. However, an area containing 

anomalous gold values in basal glacial till overlying these 

rocks has recently been identified by the Minnesota Department of Natural Resources; the source for this anomaly 

remains unknown. 

Rocks of the Wawa-Shebandowan subprovince, a 

low-grade granite-greenstone terrane composed of mafic 

metavolcanic and interlayered metasedimentary rocks, are 

poorly exposed in the southern part of the study area. No 

mineral deposits or occurrences are known in these rocks 

within the study area, but iron deposits and minor gold and 

base-metal massive sulfide occurrences are found in rocks 

to the south and southeast. 

Geological and Geophysical Analysis of the 

Subsurface Geometry of Basins in the Central 

and Western Great Basin: Implications for the 

Analysis of Concealed Mineral Resources in 

Nevada 

john C. Dohrenwend, Robert C. jachens, Richard j. 

Blakely, Barry C. Moring, and Christopher M. Menges 

A combination of geological, geomorphic, geophysical, and well-log data has been analyzed to estimate the 

approximate subsurface geometry of fault-bounded basins 

in the western Great Basin. Compilations and analyses 

include ( 1) regional geomorphic and surficial geological 

analyses including photogeologic mapping of young faults, 

pediments, and areas of thin alluvial cover; (2) digital 

analysis of a statewide, gridded compilation of gravity data 

to estimate approximate depths to dense, generally preTertiary and (or) crystalline basement within basin areas; 

(3) interpretive analyses of statewide compilations of both 

gridded and profiled aeromagnetic data to delineate bodies 

of shallowly buried magnetic rock; and ( 4) map compilation 

of selected oil and gas, geothermal, and water-well data. 

These data and derivative interpretations were combined 

and compiled on 1:250,000-scale maps for a 4° X 4° area of 

central and western Nevada. Additional work, in progress, 

will extend this compilation to a 6° x 7° area that includes 

the entire State of Nevada. 

Preliminary analysis of this multidisciplinary data 

indicates that significant variations in basin depth, areal 

extent, subsurface shape, and basin fill stratigraphy are 

likely related to variations in the timing, intensity, and style 

of neotectonic activity across the region. The Great Basin is 

composed of an irregular mosaic of neotectonic domains; 

each domain is characterized by a unique history of neotectonic activity and style. The distribution and density of 

young faults and pediments vary significantly and often 

abruptly from one domain to the next, and changes in these 

variables can be used in combination with major neotectonic structures to define domain boundaries. Subsurface 

basin geometry also appears to vary significantly among 

these neotectonic domains. Basins within the several 

domains of the northern and central Walker Lane are 

generally small and shallow. In contrast, basins farther to 

the northeast within the central Great Basin are typically 

large, continuous, elongate, and deep. Moreover, basin 

geometry and stratigraphy may also change significantly 

within individual domains; basin size, depth, continuity, 

and the thickness of post-Miocene basin fill are commonly 

less adjacent to domain boundaries and within the transverse accommodation zones that transect the central Great 

Basin. These relations provide useful geometric and stratigraphic insights for mineral resource assessment of covered 

areas in the Basin and Range province of western North 

America. 

Geologic Setting of Iron-Niobium-Rare-Earth 

Orebodies at Bayan Obo, Inner Mongolia, 

China, and a Proposed Regional Model 

L.j. Drew, Meng Qingrun, and Sun Weijun 

The Bayan Obo iron-niobium-rare-earth orebodies are 

situated on the northern edge of the Sino-Korean Plate. This 

edge is a rifted margin resulting from an intracontinental rift 

that took place 1.7 to 1.85 Ga. Available data suggest that 

this rifted margin remained passive, with the exception of 

the emplacement of granite plutons during the Caledonian 

cycle (Early Cambrian through the Silurian), until collision 

with the Siberian Plate during Hercynian time (296-245 

Ma). During this collision, large volumes of granite were 

generated. The older sedimentary and magmatic rocks 

occur today as roof pendants or are surrounded largely by 

these granites. Satellite image data reveal a pattern of 

thrusting and folding in the Bayan Obo region that is 

14 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
(SPOT DATA © CNES 1988) 

Geo logic map of Bayan Obo area, Inner Mongo li a, Ch ina. 

Q, all uvium; Hg, Hercynian granites; Vc, Carboniferous 

subaqueous vo lcanics; Zs, Sinian conglomerates and carbonates; Bg, Bayan Obo group sediments; Wt, Wu Tai 

migmatites. [Drew and others abstract] 

interpreted to be consistent with the behavior of passive 

margin stratigraphy during continental collision. Strong 

magnetic and gravity anomalies and moderate radioactive 

anomalies are characteristic of the deposit. 

The principal orebodies are hydrothermal replacements of carbonate rocks that were deposited before the 

Hercynian thrusting and folding . These carbonate rocks 

occur in the Bayan Obo group , a package of middle 

Proterozoic sedimentary rocks (1 .35-1 .65 Ga) consisting of 

arkosic and quartzose clastic rocks, shale, and limestone 

(Jishun and others, 1987). This sedimentary section rests 

unconformably on the Wutai group, which is a collection of 

gneiss and migmatite dated at 2.2 Ga . Widespread mineralization also occurs in veins and breccia filling in the 

associated clastic rocks and older gneiss and migmatite . The 

ore minerals include iron oxides, niobates, monazite , and 

bastnaesite. Gangue minerals include fluorite, K- and Nafeldspar, carbonates, amphiboles, pyroxenes, biotite , apatite, and barite. The orebodies are very large and have ore 

reserves estimated at 1.5 billion tons of iron and 37 million 

tons of rare-earth oxides. This rare-earth reserve estimate 

probably understates the resources in the deposits by a 

factor of two or three. Quantitative estimates of the niobium 

ore reserves are not available, but these resources are 

considered to be very large. 

Widespread sadie and potassic alteration is characteristic of the hanging-wall and footwall rocks, respectively. 

These altered rocks cover an area of at least 18 by 2 km in 

the vicinity of the orebodies. A zone of intense sadie 

alteration occurs in the footwall clastic rocks and in the 

older gneiss and migmatite directly below the main orebody. This footwall alteration is characterized by albite and 

sadie amphiboles. Both minor K-feldspar and sadie 

pyroxenes also occur. In contrast, widespread potassic 

alteration in the hanging-wall shale is characterized by 

K-feldspar and biotite. 

Brecciation and veining of shales in the hanging-wall 

shales are also characteristic features associated with rareearth-element mineralization. Most of the breccia fragments 

are altered to microcrystalline K-feldspar. The breccia 

matrix is composed of a variety of mineral phases: Kfeldspar, biotite, fluorite , albite , iron oxides, calcite, barite, 

monazite, apatite , bastnaesite, niobates, pyrochlore, pyrite , 

and iron carbonate. A common paragenesis in the veins, 

from earliest to latest, is feldspar (K-feldspar and minor 

albite )-biotite-fluorite-iron oxides. 

We interpret the Bayan Obo orebodies to be products 

of widespread hydrothermal alteration associated with the 

Proterozoic rifting event. The orebodies and associated 

altered rocks were subsequently metamorphosed and 

uplifted during the Hercynian collision. An occurrence 

model that can be used in other regions of the world should 

satisfy at least the following three genetic criteria: (I) a 

mechanism for tapping mantle and deep crustal magmas 

that provide heat for development of a hydrothermal system; (2) a stratigraphic section of sedimentary rocks that 

contains both host rocks (carbonate rocks) and sealing rocks 

(fine-grained siliciclastic rocks); and (3) a mechanism for 

uplifting the orebodies. At Bayan Obo , these three components were satisfied by intracontinental rifting of a 

carbonate-shale sequence of rocks on Precambrian basement followed by continental collision. Other geologic 

phenomena can satisfy these criteria, thereby forming 

similar orebodies. 

REFERENCE 

Jishun , Ren, Chunfa, Jiang, Zhengkun, Zhang , and Deyu, Qin , 

1987 , Geotectonic evolution of China: New York , 

Springer-Verlag, 203 p. 

Spectral Reflectance Changes in Vegetation 

Associated with Anomalous Concentrations of 

Metallic Elements-A Potential Tool for Mineral 

Exploration 

Barbara A. Eiswerth , Nancy M. Milton, and David A. 

Mouat 

Certain metals, when present in anomalously high 

concentrations in the substrate, have been shown to cause 

significant and detectable changes in the spectral reflectance 

characteristics of plants. We are documenting these changes 

and developing techniques to determine the identity and 

concentration of elements that cause changes in spectral 

USGS Research on Mineral Resources- 1989 Program and Abstracts 15 
U.S. Geological Survey scientist measuring spectral reflectance of a hydrothermally altered rock sample using the 

visible and near-infrared field spectrometer. The measurements are correlated with Landsat Thematic Mapper data 

to map hydrothermally altered rocks in Nevada. [Eiswerth 

and others abstract] 

signatures of vegetation . Understanding the link between 

substrate mineral content and vegetation reflectance is 

especially important for mineral assessment studies in 

heavily vegetated and inaccessible areas. The use of 

remotely sensed data provides a regional view that is rapid 

and cost effective while allowing the assessment of the 

biogeochemical environment. 

Controlled greenhouse experiments have provided 

quantitative data on the effect of anomalous concentrations 

of Ni, Cu , Zn, Co, and As in spectral reflectance of hosta 

and soybean plants. Spectral reflectance of leaves was 

measured from 0.40 f.Lm to 0.80 f.Lm at weekly intervals on 

a laboratory spectrophotometer. Spectral changes observed 

included (l) a shift in the long wavelength edge of the 

chlorophyll absorption band (known as the red edge shift) 

centered at 0.68 f.Lm to shorter wavelengths and (2) higher 

reflectance in the 0.55- to 0.65-f.Lm region compared with 

reflectance of control plants. The inflection point of the red 

edge, as defined by the first derivative spectrum, shifted 

signifi cantly to shorter wavelengths in plants dosed with 

nickel, cobalt, zinc, and arsenic. Results were ambiguous 

for copper-dosed plants. 

Spectral reflectance measurements of native vegetation collected by using field spectrometers and highresolution airborne spectrometers corroborated the greenhouse results. Field spectral measurements of sagebrush 

were analyzed from Owens Valley, Calif. Spectral changes 

in the vegetation reflectance patterns were used to distinguish areas of hydrothermally altered limestones from 

unaltered limestones. In another sagebrush study, spectral 

measurements were made in southern and south-central 

Idaho where gold mineralization is associated with high 

arsenic levels and other metals in the substrate. In the Idaho 

cobalt belt, anomalous spectral reflectance was detected in 

conifers growing in soils having anomalous levels of cobalt 

and copper. 

High-resolution airborne data were collected over 

deciduous forests in North Carolina and mixed hardwoodconiferous forests in the Vermont copper belt to delineate 

mineralized zones. In Randolph County, N.C., spectral 

anomalies in the canopy, which represent the red edge shift, 

correlated with soils containing anomalously high amounts 

of copper, molybdenum, and tin. This area of the Carolina 

slate belt is of interest because it has zones of intense 

hydrothermal alteration classified as a porphyry gold system. In Cuttingsville and Pike Hill, Vt., airborne spectraradiometer data were used to map spectral anomalies 

correlating with areas of hydrothermal alteration and mineralization . An airborne prototype for a spaceborne platform is being tested . By using this technology, the methods 

described can be applied to a variety of geographical 

regions and geologic problems. 

Mineral Resource Assessment of the Butte 

1 ° x 2° Quadrangle Using Geographic 

Information System Technology 

j.E. Elliott, C.M. Trautwein, j.L. Dwyer, and S.H. Moll 

The mineral resource potential of the Butte 1 o x 2° 

quadrangle has been assessed under the auspices of the U.S. 

Geological Survey's CUSMAP (Conterminous United 

States Mineral Assessment Program) project. By using 

geographic information system (GIS) technology , the following deposit types were assessed: vein and replacement 

base- and precious-metal, porphyry-stockwork copper and 

molybdenum, skarn gold-silver-copper-tungsten , stockworkdisseminated gold-silver, and placer gold deposits. The 

steps followed in this method of assessment were (I) data 

acquisition, (2) data compilation and entry into the GIS, and 

(3) mineral resource assessment. The GIS used for the 

assessment consists of three main subsystems (vector, 

raster, and tabular) for processing diverse types of geographically referenced data. The mineral resource assessment procedure involved (I) developing descriptive mineral 

deposit models and recognition criteria for each of these 

models, (2) using GIS techniques to develop images that are 

based on recognition criteria for each descriptive model, 

and (3) using GIS technology to combine these images into 

a final image or map. 

New data were acquired through geologic mapping, 

geochemical and geophysical surveys, remote sensing and 

geochronologic studies, and examination of mines and 

prospects. The acquired data were combined with previously published and unpublished data and compiled either 

as tables or as maps at a scale of 1:250,000. Maps, 

including a generalized geologic map, a map of mining 

16 Fifth Annual V.E. McKelvey forum on Mineral and Energy Resources 
district and area boundaries, an interpretive geophysical 

map, a map showing limonitic alteration, and a map 

showing domains of linear features, were digitized by using 

the vector subsystem. After editing, these maps were 

converted to a raster format for entry into the raster 

subsystem. Analytical data from geochemical surveys were 

entered into the tabular subsystem. By using a minimumcurvature surface-generation algorithm, the analytical data 

were combined with sample locations to produce a raster 

map for each required element. Other data entered and 

converted to raster files included the digital elevation 

model, as gridded data, and previously digitized linear 

feature data. 

The final resource assessment maps show areas of 

low, moderate, high, and, for some deposit types, very high 

resource potential for each type of deposit. These maps 

indicate that much of the Butte quadrangle is favorable for 

the occurrence of one or more of the assessed deposit types. 

Although most of the areas of high or very high potential are 

within or adjacent to known mining districts, some areas of 

high and very high potential occur in parts of the quadrangle 

that have few or no known mines and prospects. These 

areas are geologically favorable for mineral exploration. 

Tectonic and Stratigraphic Control of Subsurface 

Geochemical Patterns in the Ozark Region 

R.L. Erickson, Barbara Chazin, M.S. Erickson, E.L. 

Mosier, and Helen Whitney 

Subsurface geochemical studies in four contiguous 1 o 

x 2° quadrangles in parts of Missouri, Arkansas, and 

Kansas and along a north-south transect of drill holes in 

western Illinois reveal surprisingly consistent regional patterns of distribution and abundance of metals that have 

important implications for the genesis of Mississippi 

Valley-type (MVT) deposits. Throughout this broad area, 

insoluble residues of "barren" carbonate rocks of Cambrian 

age commonly are lead rich and contain an extensive suite 

of other metals (Zn, Cu, Ni, Co, Mo, Ag, As). This 

lead-rich metal suite is characteristic of Cambrian-hosted 

ore deposits in the Southeast Missouri lead district. Insoluble residues of carbonate strata of Ordovician, Mississippian, and Pennsylvanian age tend to be zinc rich, and 

anomalous concentrations of other metals (Cu, Ni, Co, Mo, 

Ag, As) are rare. 

The widespread occurrence of ore-related metals in 

insoluble residues of Paleozoic carbonate rocks attests to the 

passage of metal-bearing fluids through vast areas of the 

Ozark region. Leach and Rowan (1986) give compelling 

evidence that MVT deposits in the Ozark region formed 

from a single hydrologic system related to fluid migration 

northward out of the Arkoma basin in response to Ouachita 

tectonism. Our geochemical data generally support this 

model, but recently acquired data from drill holes along the 

western margin of the Mississippi embayment and the 

Illinois basin suggest that fluids migrating from the Illinois 

basin and (or) the New Madrid rift zone may have played a 

significant role in the genesis of the Southeast Missouri lead 

district. All of our data, however, suggest that Cambrian 

strata were the major regional aquifers in the Ozark region 

for transport of an extensive suite of metals, regardless of 

which sedimentary basin is favored as a metal-brine source. 

Further, the geochemical data suggest an explanation for the 

differences in ore composition (that is, lead rich versus zinc 

rich) between vertically stacked host rocks and between 

MVT mineral districts in the Ozark region. If Cambrian 

strata were the major regional aquifers for fluids, then 

mineral districts hosted by post-Cambrian rocks could have 

formed where geologic structures intersected and tapped the 

Cambrian aquifers. Fluids released up these structures 

would selectively deposit metal sulfides according to their 

relative solubility in the presence of reduced sulfur 

(Ag<Cu<Pb<Co<Ni<Zn). Zinc, the most mobile metal 

in the suite, should travel farther and should become 

enriched upward relative to the other metals as the fluid is 

selectively depleted in the less mobile metals. This process 

could result in formation of structurally controlled, zincrich districts in post-Cambrian carbonate strata 

(Mississippian-hosted Tri-State and Ordovician-hosted 

Northern Arkansas zinc districts). Fluids remaining in the 

Cambrian aquifers would maintain their characteristic leadrich metal suite and continue to migrate through Cambrian 

strata in search of a depository for their metal burden. The 

Cambrian-hosted Southeast Missouri lead district with its 

extensive suite of metals may be such a depository. The 

implications of the subsurface geochemical patterns are that 

Cambrian aquifers provided the plumbing system for all 

Ozark MVT districts and that the Illinois basin, the New 

Madrid rift zone, and the Arkoma basin may have served as 

metal-brine sources in the Ozark region. 

REFERENCE 

Leach, D.L., and Rowan, E.L., 1986, Genetic link between 

Ouachita foldbelt tectonism and the Mississippi Valley-type 

lead-zinc deposits of the Ozarks: Geology, v. 14, n. 11, p. 

931-935. 

A Review of the Proposed Standard for Digital 

Cartographic Data 

Robin G. Fegeas, Hedy j. Rossmeissl, and Robert D. 

Rugg 

The proposed Standard for Digital Cartographic Data, 

published in the January 1988 issue of "The American 

Cartographer," is the result of 6 years of effort by committees of the American Congress on Surveying and Mapping 

and the Federal Government. Intended to help eliminate 

USGS Research on Mineral Resources-1989 Program and Abstracts 17 
duplication of effort and to promote cooperation in digital 

mapping activities, the proposed standard specifies certain 

elements of content and a common format for the exchange 

of spatial data. 

Thorough testing of the proposed standard was completed first by those agencies most active in its development 

and then by a cross section of government, university, and 

private sector organizations. The testers volunteered 

considerable resources to perform one of four types of 

tests: ( 1) detailed conceptual mapping of the tester's data 

to and from the standard, (2) decoding of one or more of the 

sample test data sets into the tester's system, (3) encoding 

of the tester's data into the standard, and (4) actual transfer 

of data from one tester's system to another tester's system 

by using the standard. 

As a result of the testing, modifications were made to 

the proposed standard to clarify and to refine its content. 

Software was developed to verify successful transfer of data 

to the common exchange format. The proposed standard 

was submitted to the United States National Bureau of 

Standards for consideration as a national Federal Information Processing Standard. 

Mineral Resource and Geochemical Exploration 

Potential of Coal that has Anomalous Metal 

Concentrations 

Robert B. Finkelman and Robert D. Brown, Jr. 

The potential for using coal and coal wastes as 

mineral resources has intrigued the coal and mineral industries for many years. However, to date there has not been 

any significant use of these sources. Is there any justification for continued interest? We believe that the potential 

exists for mineral recovery from coal and coal wastes, 

provided that we apply our knowledge properly. We envision three aspects to this concept: ( 1) byproduct recovery 

from coal and coal wastes, (2) coal as a byproduct of a 

mineral extraction process, and (3) coal as a geochemical 

indicator of mineralization. 

1. Byproduct recovery from coal and coal wastes. -In the United States, more than 900 million short tons 

of coal are produced annually and yield about 100 million 

short tons of waste products. Using national means for ash 

yield and trace element concentrations, calculations indicate 

that coal and coal ash could provide at least half of the U.S. 

annual consumption of As, Be, Bi, Co, Ga, Ge, Hf, Nb, 

Se, Sr, Te, Tl, Y, the rare-earth elements, and significant 

contributions of many other elements. Detailed studies have 

been conducted on the extraction of Al, Cd, Ga, Ge, Fe, 

Mo, Ti, U, Zn, and other elements. Extraction of these 

elements has not been economic except for sporadic local 

production of uranium. 

The reasons for this bleak track record include ( 1) 

widely dispersed sources of coal and coal wastes (only one 

U.S. mine produced more than 13 million tons of coal in 

1986, and few powerplants burn more than 5 million tons of 

coal annually), (2) significant production of low-ash and 

low-sulfur coals that have considerably lower trace element 

concentrations than the national average, (3) no viable 

extraction procedure, and (4) depressed markets. We 

believe recovery of selected elements of strategic importance is possible. Among the more attractive possibilities 

are Bi (coal mean 1.61 ppm versus 0.01 ppm in shale), Se 

(2. 78 versus 0.6), Sb (1.17 versus 1.5), Cd (0.55 versus 

0.3), Ag (0.09 versus 0.07), Tl (3.5 versus 0.4), Te (O.X 

versus 0. 0 1), and In (0. X versus 0 .1). These elements 

generally have chalcophile tendencies and therefore were 

concentrated in coal by the same mechanisms, are highly 

concentrated in coal with respect to crustal abundances, are 

moderately to highly volatile and therefore may be collected 

from flue gas, form readily soluble compounds that could 

be extracted by a single chemical process, and are environmentally deleterious, therefore, extraction from coal or coal 

wastes would reduce pollution. 

2. Coal as a byproduct of a mineral extraction 

process.-Some coals are extraordinarily enriched in certain trace elements. A coal in Alabama contains almost 

2,200 ppm arsenic (12,500 ppm arsenic in the ash); a coal 

in Texas contains 300 to 600 ppm silver in the ash; the ash 

of an Illinois coal contains almost 2,000 ppm cadmium; 

coals containing almost 8,000 ppm germanium in the ash 

are known from several locations; lignites in Mississippi 

average over 10 ppm selenium; coals that have several 

thousand ppm uranium have been found in several western 

States. These and other examples of exceptional concentrations of elements in coal are on file in the U.S. Geological 

Survey's National Coal Resources Data System (NCRDS). 

Generally, coals containing these high element concentrations are not mined because of environmental and 

coal quality (high ash yield or high sulfur content) concerns. 

However, mining these coals for their mineral resources and 

using the cleaned coal as a byproduct to generate heat may 

make some of these deposits economically viable. An 

example of this symbiotic relation can be seen in the mining 

of clays and associated lignites in Texas and California. 

3. Coal as a geochemical indicator of mineralization.-The concept of biogeochemical prospecting for mineral resources has been successfully applied to a number of 

elements, and coal can be used in the same way. Some of 

the high elemental concentrations noted in the previous 

section may not be economically recoverable, but they may 

be indicative of nearby mineralization. Many of the 13,000 

coal analyses in the NCRDS are from sedimentary basins 

that have virtually no other chemical analyses. These 

NCRDS data offer a unique opportunity to assess the 

mineral resource potential of these basins. An example of 

how this concept can be applied is the diamonds that have 

18 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Figure 1. Scanning electron micrograph of a diamond 

crystal extracted from coal. Scale bar= 10 micrometers. 

[Finkelman and Brown abstract] 

been found recently in a Wyoming coal in an area that has 

no known diamond-bearing source rocks (fig. 1). A careful 

reconnaissance study in the vicinity of the coal deposit may 

lead to the diamond source. 

In conclusion, although byproduct recovery from coal 

and coal ash has not been successful in the past, new 

analytical data justify our continued interest in this concept. 

Preliminary Map Showing the location of 

Productive Lode and Placer Gold Deposits and 

Significant Gold Prospects in Montana 

David Frishman, ].E. Elliott, E.E. Foord , R.C. Pearson, 

and W.H. Raymond 

"Gold is where you find it," and one of the best places 

to find it is where someone else has found it before. The 

Montana gold map and accompanying data base provide a 

comprehensive inventory of placer and lode mines in 

Montana that produced and (or) contain as plausible 

resources more than 500 troy ounces of gold. Mine and 

prospect locations are shown by different sized, shaped, and 

colored spots. Spot size denotes one of four size classes 

(500-5 ,000 OZ ., 5,000-50 ,000 OZ. , 50,000-500,000 OZ. , 

and > 500 ,000 oz. production+reserves). Spot shape is 

coded for deposit type (placer, vein-replacement, disseminated , brecci a pipe , stratabound, skarn, and other), and spot 

color is keyed to the age of mineralization (rarely well 

known). The map, at a scale of 1:500,000, shows the 

locations of more than 450 mines and prospects; areas 

having a high density of mines are shown in more detail at 

a larger scale . An accompanying pamphlet lists the name of 

each mine, synonymous names, mining district, location 

(latitude and longitude), commodities produced, host rock 

lithology and age, lithology and age of associated igneous 

rocks (if any), and selected references. In addition to the 

published map and pamphlet, the data will be made available as a U.S. Geological Survey (USGS) Open-File Report 

in the form of a 51/4 in DOS-formatted diskette containing 

the data in both ASCII and dBase III formats. Although the 

map will be published at l :500,000 scale , location information for mines and prospects has been compiled from the 

most accurate maps available, usually USGS l :24 ,000-

scale topographic quadrangles. Therefore , latitude and longitude for most mines listed in the data base should be 

accurate when plotted at scales as large as 1:24,000. 

Geologic-Map Information and Where to Find It 

H. Kit Ful ler 

Geologic maps can be somewhat difficult to obtain. 

To help alleviate this problem, the U.S. Geological Survey 

(USGS) and many State geoscience agencies produce geologic map indexes. 

USGS Geologic Map Indexes (GMI's) are published 

State-by-State compilations that include index maps (sorted 

by scale), a bibliography, and an explanation. To use a 

GMI, identify an area of interest on the index maps (fig. l) 

and use the numbers of the geologic maps to find complete 

reference data in the bibliography . The geologic map 

indexes produced by State agencies vary in format and 

content, and many of them include information not found in 

USGS GMI's. 

In addition to these information sources, a USGS data 

base (GEOINDEX) having the bibliographic data from the 

GMI's is now available. GEOINDEX and two other USGS 

data bases-USGS Library and the Earth Science Data 

Directory, were recently released on a CD-ROM disk. In 

this format, the data can be kept more up-to-date than 

GMI's. 

Other sources of geologic-map information include 

State publication lists, USGS publication catalogs, library 

map catalogs, and commercially available lists of USGS 

maps. These sources usually include references other than 

geologic maps, and searching them can be more time 

consuming than searching only the geologic-map literature. 

However, well-prepared indexes or other methods of organizing the geologic-map information make some of these 

products excellent reference sources. 

USGS Research on Mineral Resources-1989 Program and Abstracts 19 
Figure 1. Index map from the 1988 Geologic Map Index (GMI) of Idaho showing general purpose 

and topical geologic maps at scales between 1:24,000 and 1 :63,360 (inclusive). Patterns indicate 

map coverage, not type of map. Some references incl ude more than one map (for example, no. 

309); some boundaries represent more than one reference (for example, nos. 51 - 52). The GMI of 

Idaho includes four other index maps to show maps at other scales. Each index map shows State 

and County boundaries and latitude/longitude grid. [Fuller abstract] 
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GEOINDEX, the bibliographic database of geologic maps, is updated through December 1988. 
Classic tundra tussocks in southwestern Alaska. 

Mineral Resource Assessment, Bendeleben and 

Solomon Quadrangles, Western Alaska 

Bruce M. Gamble 

A multidisciplinary mineral resource assessment of 

the Bendeleben and Solomon quadrangles, western Alaska, 

has identified 13 permissible mineral deposit types. These 

include deposit types that are currently known to exist and 

those that are speculative based on available data . Thirtyfive tracts (shown on three poster session maps) are favorable for the following mineral deposit types: 

• Map l : Tin vein, greisen, skarn, and replacement; 

iron-(copper), tungsten , and lead-zinc skarn; polymetallic 

replacement and vein; and molybdenum stockwork. 

• Map 2: Volcanogenic massive sulfide and sedimenthosted exhalative zinc-lead . 

• Map 3: Low-sulfide gold-quartz veins. 

Gold placers account for the majority of metallic 

mineral production from these quadrangles; approximately 

2 million ounces of gold were produced between 1898 and 

1985 . From 1903 to 1907, about 27,000 ounces of gold 

were obtained from low-sulfide gold-quartz veins at the Big 

Hurrah mine . Small amounts of silver-rich galena ore were 

mined from the Omilak mine (polymetallic replacement?) 

and the Independence mine (polymetallic vein). 

Deposit types that occur in the quadrangles but have 

not produced ore are sedimentary exhalative zinc-lead, 

iron-(copper) skarn, molybdenum stockwork, and polymetallic tin veins. 

Concealed tin deposits are possible around the 

Oonatut Granite Complex-the easternmost of the tin granites on the Seward Peninsula. A small, prominent aeromagnetic high above a buried portion of the granite may be 

related to a concealed tin skarn or a tin replacement deposit. 

Aeromagnetic data also indicate the potential for additional 

iron-(copper) skarn mineralization . Concealed polymetallic 

vein , replacement, and lead-zinc skarn deposits may be 

present near several plutons. Molybdenum stockwork mineralization associated with the Windy Creek pluton could 

represent the outer portions of an ore deposit. 

The Hannum-Harrys Creek deposit is the only example of a sedimentary exhalative zinc-lead deposit in these 

two quadrangles; however, several similar occurrences are 

in the Nome quadrangle to the west, and there is potential 

for additional deposits of this type in the Bendeleben and 

Solomon quadrangles. Volcanogenic massive sulfide 

deposits have not been found in this area; however, favor22 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
able host rocks and anomalous stream sediment geochemistry indicate that there is some potential for Besshi-type 

deposits. 

Low-sulfide gold-quartz veins may represent the best 

hope for future mineral production in these quadrangles. 

Most of the veins, with the exception of those at the Big 

Hurrah mine, are too narrow (mostly <10 em) and discontinuous to have warranted much interest in the past. 

However, higher gold prices and other factors have contributed to increased exploration in the area. Most of the 

low-sulfide gold-quartz veins examined on the Seward 

Peninsula occur in a mixed unit of interlayered quartzgraphite schist, pure and impure marbles, and lesser pelitic 

and chlorite-albite schist. Some occur in a unit composed of 

chlorite-albite and mafic volcanic schists that overlies the 

mixed unit. 

Contrasting Sulfur Sources for lower Versus 

Upper Midcontinent Mississippi Valley-Type 

Ores-Implications for Ore Genesis 

Martin Goldhaber 

Basic genetic concepts for Mississippi Valley-type 

(MVT) lead-zinc deposits cannot be considered complete 

until the mechanism(s) and the site(s) of sulfide generation 

are known. To address these issues, data from regional 

sulfur isotope studies (more than 300 analyses) to assess 

sulfur sources have been combined with petrographic observations to constrain relative timing of sulfide emplacement. 

These data have defined "footprints" of aqueous sulfide 

migration in the form of trace epigenetic sulfide minerals 

along likely ore fluid flow paths. 

Regional studies of the lower midcontinent (LMC) 

comprising Upper Cambrian through Mississippian carbonates in Missouri, Arkansas, and Illinois show widespread 

development of sulfides (dominantly FeS2) that were precipitated epigenetically during hydrothermal fluid flow 

associated with the regional mineralizing event(s). There is 

a marked stratigraphic trend in 834S of these sulfides. The 

broadest range and heaviest 834S values ( -10 to +40 per 

miL mean +8) are found in the oldest part of the section, 

specifically the Upper Cambrian Bonneterre Formation. 

Progressively lighter epigenetic sulfides occur upsection. 

For example, Mississippian-hosted FeS2 has a mean 834S of 

-9 per mil. 

These stratigraphic trends in 834S from unmineralized 

rocks closely parallel isotope values from major ore districts. Published studies of LMC ores of the Southeast 

Missouri lead belts, hosted by the Bonneterre Formation, 

show a broad range of 834S values (-2 to +30 per mil), 

whereas the Mississippian-hosted Tri-State district of southwest Missouri and adjoining States has a much narrower 

range of isotopic compositions (from 1 to -9 per mil) 

centered around -5 per mil. 

This parallelism is best explained by a widespread 

migration of H2S-bearing hydrothermal brines that have 

at least two distinct sulfur sources. Isotopically heavy 

H2S deeper in the section arose from thermochemical so;-

reduction of Cambrian and Ordovician evaporates whose 

834S is known to be 25 to 30 per mil. Evaporates of this age 

occur in association with mature petroleum source beds in 

the southern Illinois basin to the east of the lead belts, and 

fluids from this area are therefore a potential sulfur source 

for the ores. A separate H2S source, having 834S of about 

-5 per mil, is present as organosulfur in Pennsylvanian 

coals and hydrocarbons and would have been released 

during regional thermal maturation. 

Fluid mixing of two low pH, H2S- and metal-bearing 

brines having distinct 834S values gave rise to the lead belt 

mineralization. This mechanism explains the wide range in 

834S of these ores and is also consistent with constraints 

from lead-isotope data, ore textures, and ore mineralogy. In 

contrast, Tri-State ores formed from a single isotopically 

homogeneous sulfur source. Although fluids bearing sulfide 

of this isotopic composition were regionally widespread, 

the present data do not define whether or not precipitation 

was produced by fluid mixing. 

Upper midcontinent mineralization in Illinois and 

Wisconsin is characterized by a constant 834S of 13 per mil 

for ore-forming H2S. Data from several cores peripheral to 

orebodies demonstrate that residual organic sulfur in the 

Gutenberg Member of the Decorah Formation contains 

organic sulfur that is also near 13 per mil. This similarity 

suggests that sulfur was partially released during mineralization and provided a local trap for migrating metalbearing brines. 

In summary, the examination of geochemical and 

geologic information reveals that MVT deposits form from 

both local and distant sulfur sources and by more than one 

mechanism of precipitation. 

Anomalous Palladium-Platinum Occurrences in 

Mesozoic Quartz-Normative Tholeiitic Suites in 

the Eastern United States 

David Gottfried, A.j. Froelich, P.j. Aruscavage, and 

Norma Rait 

Several Mesozoic diabase-granophyre sheets in the 

Eastern United States were assessed, through the analysis of 

250 samples, for their potential as sources or hosts of 

platinum group metals. Systematic distribution, abundance 

patterns, and ratios of palladium and platinum through 

differentiated sheets between upper and lower chilled margins have greatly improved our understanding of palladiumplatinum behavior during the differentiation of typical 

high-titanium, quartz-normative (HTQ) tholeiitic magmas 

(Gottfried and Froelich, 1988). Palladium and platinum 

USGS Research on Mineral Resources -1989 Program and Abstracts 23 
wv 

L_ 

e Pd 

1-PALISADES. NJ 

2- REESERS SUMMIT. PA 

3- BELMONT. VA 

sc 0 50 100 MILES I I I I I 

0 50 100 KILOMETERS 

Figure 1. Index map of the Eastern United States showing the location of early 

Mesozoic basins (dotted areas) and anomalous palladium occurrences in late-stage 

ferrogabbroic differentiates of high-titanium, quartz-normative diabase sheets. [Gottfried and others abstract] 

contents of chilled margins of HTQ suites average about 10 

ppb each. During differentiation, platinum is enriched 

relative to palladium in cumulate layers, whereas in the 

more evolved later differentiates, palladium is enriched 

relative to platinum. 

Anomalous abundances of palladium+platinum, 

more than 200 ppb, occur in ferrogabbro and ferrodiorite 

and represent an order of magnitude enrichment over other 

rocks of similar composition in the Mesozoic basins. 

Palladium anomalies have thus far been noted in similar 

rocks from three widely separated differentiated HTQ 

sheets: (1) Palisades sill in New Jersey, (2) Reeser's 

Summit in the York Haven sheet, Pennsylvania, and (3) 

Belmont sheet, Virginia (fig. 1). The highly evolved 

portion of the York Haven sheet at Reeser's Summit, 

typical of the other anomalous palladium occurrences, is 

well exposed and is being studied in considerable detail. 

The distribution of MgO, Pd, and Pt and Pd:Pt from the 

24 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
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Figure 2. Distribution of MgO, Pd, and Pt and Pd:Pt in ferrogabbro differentiate of high-titanium, quartz-normative York 

Haven diabase sheet, Reeser's Summit, Pa. (Analysts, Norma Rait and Hezekiah Smith, U.S. Geological Survey.) 

[Gottfried and others abstract] 

chilled margin across this section are shown in figure 2. The 

anomaly zone in the ferrogabbro, near the upper part of this 

sheet, is accompanied by relatively high contents of copper 

(to 360 ppm), gold (to 54 ppb), and tellurium (to 26 ppb) 

and has high iron (to 18 percent), titanium (to 3.5 percent), 

and chlorine (to 0.44 percent). 

The occurrence of high contents of palladium and 

copper in the late stage differentiates indicates that silicate 

fractionation proceeded without early precipitation of an 

immiscible sulfide phase. This absence of early precipitation is not unexpected inasmuch as the sulfur content of 

HTQ margins is generally quite low, 100 to 200 ppm 

(Gottfried and others, in press). Petrologic and geochemical 

data, however, indicate that the marked enrichments of Fe, 

Ti, Cl, Te, Au, Pd, and, to a lesser extent, Pt in the 

ferrogabbro zone cannot be accounted for solely by tholeiitic differentiation. It appears more likely that late magmatic 

or postmagmatic fluids, predominately chlorine rich, have 

played an important role in their transport and enrichment 

(Belkin, this volume). 

The comprehensive geologic, petrologic, and 

geochemical data obtained in our ongoing studies provide a 

framework within which must fit any genetic models or 

processes proposed to account for high concentrations of 

precious metals in the HTQ tholeiites. Furthermore, integration of field geologic observations and geochemical and 

petrographic data provides a means of delineating areas 

favorable for prospecting for either subtle or concealed 

palladium-platinum mineralization in differentiated HTQ 

tholeiitic diabase sheets. 

REFERENCES 

Gottfried, David, and Froelich. A.J .. 1988, Variations of palladium and platinum contents and ratios in selected early 

Mesozoic tholeiitic rock associations in the Eastern United 

States: U.S. Geological Survey Bulletin 1776, p. 332-341. 

Gottfried, David. Froelich, A.J .. Rait, Norma, and Aruscavage, 

P.J., in press, Fractionation of palladium and platinum in a 

Mesozoic diabase sheet, Gettysburg basin, Pennsylvania: 

Journal of Geochemical Exploration. 

USGS Research on Mineral Resources-1989 Program and Abstracts 25 
Early-Middle Proterozoic Unconformities: 

Unconventional Sources for Platinum Group and 

Precious Metals 

Richard I. Grauch 

Important amounts of platinum group elements 

(PGE), gold, and nickel are contained in some of the 

world's largest high-grade, unconformity-related uranium 

deposits. Most of these deposits are hosted by rocks on 

either side of the early-middle Proterozoic unconformity in 

the Pine Creek geosyncline (Australia) and in the Athabasca 

basin (Canada). The Coronation Hill deposit (South Alligator River area, Australia) contains a minimum of 8 X 105 

tonnes (t) of ore, at a grade of 5 g/t gold. The average 

grades for platinum and palladium are 0.62 g/t and 1.33 g/t, 

respectively, for gold-bearing samples (> 1 g/t gold) (Needham, 1987). The Kasner Group (1987), working in the 

vicinity of the Nicholson uranium deposit (Beaverlodge 

area, Canada), reported gold between 58.63 and 361.37 g/t, 

platinum between 6.51 and 12.0 g/t, and palladium values 

of 14.06 g/t for three intercepts ranging between 0.9 and 1.6 

min length. A 54.9-m-long trench averages 97.72 g/t gold. 

In addition, gold has been produced from the tailings at the 

Cluff Lake uranium deposit (Canada), and the minimum 

gold reserves at the Jabiluka uranium-gold deposit (Australia) are 8, 100 kg (palladium is present, but reserves have 

not been calculated). The significant amounts of PGE and 

gold in these deposits, all related to early-middle Proterozoic unconformities preserved in Precambrian cratons, suggest that there is potential for unconventional resources of 

PGE and gold in this geologic environment. 

The genesis of these unconformity-related deposits 

has been a topic of intense debate, and genetic hypotheses 

range from supergene to hypogene (magmatichydrothermal) to diagenetic. These varied hypotheses inadequately address the problems presented by the presence of 

a suite of metals not normally found in the same deposit. 

However, the following hypothesis addresses those problems. 

Initially, a basement of metamorphosed, metal-rich 

sediments and volcanics is formed. Next and most important, an extensive and deeply weathered surface is developed on the basement. Ideally, the surface is developed in 

response to several different climatic conditions in much the 

same way that the present surface of the Yilgarn block of 

western Australia has developed. This complex process of 

forming a continental unconformity results in the concentration of seemingly incompatible elements in the same, in 

a gross sense, stratigraphic unit-the soil profile and 

underlying altered rocks. On the Yilgarn block, gold was 

concentrated in laterites (the Boddington and Mount Gibson 

deposits), uranium in calcretes (the Yeelirrie deposit), 

nickel in laterites, and platinum-palladium in laterites. Not 

only are some elements concentrated by this natural heapleaching process, but many can be fractionated. Uranium 

can be separated from its daughter lead and from thorium, 

platinum can be partially separated from palladium, and 

gold can be separated from silver. The next and equally 

critical step is the preservation of most of the soil horizon at 

the base of a large sedimentary basin. During basin evolution, deeply circulating brines, which had ready access to a 

diversity of metals within the paleosol, carried some of 

those metals in solution and reconcentrated them in new 

chemicostructural traps. This, also, is a lengthy and complex process that results in the spatial, not necessarily 

temporal, superposition of different fluids and thus different 

metal concentrations. 

This conceptual model helps to explain the diversity 

of metals found in unconformity-related deposits and supports the proposition that significant new PGE and preciousmetal resources exist in the unconformity environment. 

REFERENCES 

Needham, R. S., 1987, A review of mineralisation in the South 

Alligator Conservation Zone: Bureau of Mineral 

Resources, Australia, Record 1987/52, 24 p. 

Kasner Group, 1987, Working together to develop Canada's 

natural resources: CIM Bulletin, March, p. 17 [advertisement]. 

Interpreting Concealed Range-Front Faults in 

Nevada from Gravity and Digital Fault Data and 

the Significance for Gold Exploration 

V.j.S. Grauch and Don L. Sawatzky 

Locating concealed exploration targets is becoming 

increasingly important now that exposed deposits are being 

exhausted. Discovery of the bonanza Sleeper deposit in 

north-central Nevada, which is spatially associated with a 

partially concealed range-front fault system, is one reason 

new exploration efforts have been directed toward this kind 

of target. Under the auspices of the Bureau of Indian 

Affairs, the U.S. Geological Survey is conducting a 

regional gold resource assessment project involving the 

interpretation of concealed range-front faults. 

Concealed range-front faults were interpreted for this 

study by digitally comparing a derivative product of 

regional gravity anomaly data to digitized mapped faults. 

The derivative gravity product was created by applying a 

mathematical technique to regional gravity data from 

Nevada. The technique, based on the properties of the 

horizontal gravity gradient, estimates the locations of density boundaries, which are steeply dipping boundaries 

between rocks having contrasting densities, such as at 

geologic contacts or faults. In Nevada, the boundaries 

exhibiting the greatest density contrast correspond to exten26 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
sional range-front faults, where high-density, indurated 

rocks in the ranges abut low-density basin fill. 

Digital comparison of the calculated density boundaries to digital fault data shows that many density boundaries correspond to at least some portion of mapped rangefront faults (allowing for discrepancies owing to limitations 

in the data sets). For example, such correspondences occur 

along the western side of the Egan Range next to White 

River Valley and along the eastern side of the Stillwater 

Range next to Dixie Valley. Other density boundaries 

confirm large portions of faults that can be inferred only 

geologically, such as along the east sides of the Kawich and 

Hot Creek Ranges next to Hot Creek Valley and along the 

east side of the Toiyabe Range next to Big Smoky Valley. 

Still other density boundaries track along a range front but 

then extend beyond the range into the adjoining basin , such 

as along the west side of the Red Hills, extending into the 

Kobeh Valley and along the northwest side of the East 

Range , extending northward into the valley west of Winnemucca. Some density boundaries parallel mapped rangefront faults but are significantly offset from the faults and 

are covered entirely by alluvium. These boundaries probably indicate the edge of the pediment under cover, whereas 

the range-front fault represents only a minor step in a fault 

set stepping down toward the basin. Examples are density 

boundaries located in Huntington Valley, Diamond Valley, 

Railroad Valley , and White River Valley. 

Th is method of interpreting faults from calculated 

density boundaries could be an important exploration tool at 

both regional and local scales. At regional scales, the 

interpreted range-front faults represent major faults having 

large density contrasts and considerable depth extent. These 

faults may have been part of a deep plumbing system 

genetically related to mineralization. Minor faults at local 

scales, important in locally controlling ore deposition, 

could be interpreted in the same fash ion if gravity data were 

collected in more detail. 

A Deposit Model for Gold-Bearing Skarns 

jane M. Hammarstrom, Greta j. Orris, james D. Bliss, 

and Ted G. Theodore 

Data for more than 300 skarn deposits (of which 65 

percent report gold in trace amounts to 25 g/t) suggest that 

gold-bearing skarns can be separated into two subtypes that 

do not differ geologically, but do differ statistically , in 

gold, silver, and base-metal grade distributions. Deposits 

that have an average gold grade of 1 g/t or more and that 

exhibit distinctive skarn mineralogy can be subdivided into 

(I) skarns in which gold is the primary commodity (median 

grade 7. 7 g/t gold , 1.3 g/t silver) and (2) skarns in which 

gold has been recovered as a byproduct but assumes the role 

of primary commodity given sufficient grade due to current 

metal prices (median grade 3.0 g/t gold, 18 g/t silver). By 

using these criteria, many byproduct gold skarn deposits 

may be included in existing deposit models for copper, iron, 

and lead-zinc skarns. 

Gold-bearing skarns typically form in Mesozoic and 

Cenozoic orogenic belts and island-arc settings; the skarns 

are spatially and genetically related to 1-type felsic to 

intermediate intrusive rocks. Common features of these 

deposits include (1) gradational changes to other deposit 

types within very large mineralized systems and (2) localized gold enrichment withi n or peripheral to iron or basemetal skarn. Host rocks usually include a premetamorphic 

calcareous component, but gold-bearing skarns also are 

known in conglomerate, shale, and tuff; granitoid 

endoskarn is economically significant in some deposits. 

Me inert ( 1987) cites a clastic or volcaniclastic component in 

the host rock as characteristic of gold skarns. Gold-bearing 

skarns generally occur in calcic exoskarn associated with 

intense retrograde alteration. In north-central Nevada, the 

Fortitude and McCoy deposits formed near granodiorite 

stocks, whereas gold-bearing skarns in British Columbia, 

such as those at Hedley and Tillicum Mountains, are 

associated with diorites and gabbros. 

A generalized paragenetic sequence for gold-bearing 

skarns involves early formation of hornfels, K-feldspar and 

quartz veining, prograde skarn crystallization of diopsidehedenbergite that is subsequently replaced by grossularEuhedral gold crystals from the Roraima placer, Braz il. 

Recent evid ence suggests that crystals such as these may 

actually grow in place, aided by organic transport of gold 

and deposition nucleated by bacteria. 

USGS Research on Mineral Resources-1989 Program and Abstracts 27 
andradite garnet in some deposits, and retrograde alteration 

of the anhydrous minerals to form a hydrous mineral suite 

characterized by chlorite, epidote, amphibole, quartz, calcite, and (or) nontronite commonly accompanied by sulfides and iron-oxide minerals. Gold is generally deposited 

during retrograde stages with, or subsequent to, sulfide 

deposition from relatively low temperature ( <300 °C) 

saline fluids; some deposits include significant concentrations of gold in late quartz. Retrograde assemblages and 

high-grade ores are particularly concentrated along structures favorable for fluid migration, such as faults and 

contacts between contrasting lithologies. Opaque minerals 

reported for gold-bearing skams include native gold, electrum, pyrite, chalcopyrite, pyrrhotite, arsenopyrite, 

sphalerite, galena, bismuth minerals, magnetite or hematite, and tellurides. Gamet and pyroxene compositions, 

retrograde and ore assemblage mineralogy, and igneous 

rock types associated with gold-bearing skams apparently 

cannot always be distinguished from those associated with 

copper or iron skams. Myers and Meinert (1988) note that 

the mineralogy and high grade of the Fortitude deposit are 

atypical of other base-metal skarns. Gold occurs in relatively oxidized skams characterized by andradite-diopsidechalcopyrite assemblages and in relatively reduced skams 

characterized by hedenbergite-pyrrhotite. Ore guides 

include ( 1) all rocks favorable for development of skarn in 

districts known for other types of precious-metal deposits, 

(2) reported gold in base-metal and iron skarn, and (3) gold 

placers in regions of well-developed skarn. Anomalous 

bismuth, tellurium, arsenic, and selenium values are useful 

geochemical signatures for some gold-bearing skarns. 

REFERENCES 

Meinert, L.D., 1987, Gold in skarn deposits-A preliminary 

overview: Proceedings of the 7th Quadrennial IAGOD 

Symposium, E. Schweizerbart'sche Verlagsbuchhandlung, 

Stuttgart. 

Myers, G.L., and Meinert, L.D., 1988, Zonation of the Copper 

Canyon-Fortitude gold skarn system: Geological Society 

of America Abstracts with Programs, v. 20, no. 7, p. A93. 

A Conodont Color Alteration Anomaly in Central 

Indiana-Possibility of Mississippi Valley-Type 

Hydrothermal Activity 

A.G. Harris, C.B. Rexroad, R.T. Lierman, and R.A. Askin 

Anomalously high conodont color alteration indices 

(CAl) of 2 through 4 and 6 and 7 occur sporadically in 

lower Carboniferous rocks in part of Putnam County, Ind. 

A range of CAl values has been found within a sample, a 

stratigraphic section, and the area. These rocks have 

regional CAl values of 1 to 1.5. Based on 62 localities in a 

700-km2 area, the CAl anomaly forms a north-trending, 

elongate area about 28 km long and 9 km wide. Precise 

limits of the anomaly could not be determined because these 

rocks are concealed beneath thick glacial deposits to the 

north and northeast and younger, nonmarine Paleozoic 

rocks to the west. Rocks exposed in the anomalous area 

range from the Borden Group to the Ste. Genevieve 

Limestone (Mississippian) and the Mansfield Formation 

(Lower and Middle Pennsylvanian), which unconformably 

overlies the Mississippian rocks. 

Palynomorphs were concentrated from some of the 

samples that produced conodonts having anomalously high 

CAl values or samples that were stratigraphically close to 

them. Individual samples contain palynomorphs having a 

relatively broad range of thermal alteration indices (TAl); 

most specimens have low TAl values (2.5-2.7; =CAl of 

1-1.5); less common specimens have even lower values; 

and rare specimens have higher to considerably higher 

values. These variations may be caused by differential 

carbonization and (or) oxidation. In this geologic setting, 

the darkest palynomorphs are probably not recycled. Some 

of the lighter spores show evidence of corrosion. The 

event(s) that produced conodonts having anomalously high 

CAl values and oxidized conodonts (CAl 6 and 7) also may 

have oxidized some of the palynomorphs and caused 

bleaching and abnormally low T AI values. Relative proximity of hydrothermal fluids causing competing carbonization and oxidation processes, as well as physical and 

chemical differences between palynomorphs and conodonts, probably affected rates of alteration and may help to 

explain inconsistencies between CAl and TAl values in 

these samples. 

The CAl values and their irregular distribution areally, locally, and even within a sample, together with the 

textural alteration of some of the conodonts, suggest a 

hydrothermal event involving fluids having some temperatures of at least 200 °C. There appears to be no correlation 

between petrographic and conodont data; the lack of correlation indicates that hydrothermal flow patterns were not 

related to petrographic factors but, more likely, were related 

to fluid channelways or some local chemical environments. 

A few exposures of marine Pennsylvanian shales of the 

Mansfield Formation occur within the area of the anomaly. 

Conodonts from these rocks have a CAl of 1; this value 

could indicate either that the thermal event preceded deposition of the Mansfield or that the alteration was hydrothermal and did not affect the impermeable shale. We prefer the 

latter hypothesis because most hydrothermal events in the 

eastern midcontinent region are of Late Pennsylvanian or 

younger age. There are no magnetic anomalies corresponding to the CAl anomaly, but the CAl anomaly overlaps an 

area of above-average geothermal gradient and overlies a 

prominent subsidiary topographic basement high offset 

from the main gradient that trends from the Illinois basin to 

a culmination at the Cincinnati arch. No local source for 

heated fluids has been identified, but this is characteristic of 

28 Fifth Annual V .E. McKelvey Forum on Mineral and Energy Resources 
Mississippi Valley-type (MVT) hydrothermal systems 

where fluids are presumed to be far traveled and to have 

moved updip during basin evolution. Consequently, this 

area and its downdip equivalent are possible sites for the 

localization of MVT ores. 

Hydrothermal and Hydrogenetic Ferromanganese Oxide Mineralization of Active Volcanic 

Arcs 

James R. Hein, Marjorie S. Schulz, and Jung-Keuk Kang 

Ferromanganese oxide deposits form in four tectonic 

environments in the Pacific: island arcs, spreading axes, 

midplate volcanic edifices, and abyssal plains. Three types 

of iron-manganese deposits occur in island arcs: (1) crusts, 

(2) manganiferous sandstone, and (3) stratabound and, in 

places, stratiform manganese. (1) Iron-manganese crusts 

that precipitate from seawater on rock substrates in island 

arcs are partly hydrogenetic and partly low-temperature 

hydrothermal in origin. Compositionally these crusts are 

intermediate between crusts formed at midplate edifices and 

those of spreading axes. Based on rare-earth-element (REE) 

and minor element compositions, the hydrothermal contribution to these crusts ranges from 60 to 90 percent. (2) 

Low-temperature hydrothermal iron-manganese oxide 

cements volcaniclastic sandstone. In the Northern Mariana 

Islands arc, these deposits are low grade (average 1 7 

percent manganese) but large tonnage. Iron averages 6. 8 

percent and copper averages 0.04 percent. These deposits 

form by impregnation of porous volcaniclastic deposits by 

low-temperature hydrothermal fluids. (3) Hydrothermal 

manganese oxides form stratabound layers and lenses that 

average 40 percent manganese for the Northern Mariana 

ridge deposits and 43 percent manganese in the Tonga 

Ridge-Lau Basin area. These are high-grade, low- to 

medium-tonnage manganese deposits. In addition to manganese, molybdenum, barium, and zinc are strongly 

enriched in these deposits; molybdenum averages 0.1 percent. Stratabound manganese deposits formed at higher 

temperatures than the manganiferous-sandstone deposits 

and resulted, in part, from leaching of the volcanic arc 

rocks. These various types of iron-manganese deposits can 

be distinguished by their mineralogy, iron-manganese 

ratios, trace metals, and REE patterns (table 1). For 

example, Fe:Mn is invariably greater than 1.0 for crusts, 

0.1 to 1.0 for manganiferous sandstone, and less than 0.1 

for stratabound deposits. 

Hydrothermal mineralization of the deposits sampled 

on the Northern Mariana volcanic arc occurred during the 

past 700,000 years, based on incorporated microfossils. 

The deposits formed during late-stage volcanic processes on 

the active arc, probably during submarine flank fissure 

eruptions. On the Tonga Ridge, most of the manganese 

mineralization is Quaternary in age. 

REFERENCES 

Hein, J.R., Fleishman, C.L., Morgenson, L.A., Bloomer, S.H., 

and Stem, R.J., 1987, Submarine ferromanganese deposits 

from the Mariana and Volcano volcanic arcs, West 

Pacific: U.S. Geological Survey Open-File Report 87-281, 

67 p. 

Hein, J.R., Gein, L.M., and Morrison, M.S., 1988, Submarine 

ferromanganese mineralization in active volcanic arc systems: Proceedings of PACON 88-Pacific Congress on 

Table 1. Average chemical composition for selected elements of iron-manganese deposits of active volcanic arcs, 

midplate volcanic edifices, and manganese nodules. All data are in weight percent, except Pt, which is in ppm. n is 

number of analyses for various elements. All samples are from water depths less than 2,500 m except for the abyssal 

nodules. -, no data. [Hein and others abstract] 

Area n Mn Fe Co Ni Cu Pb Ti Mo Si p Pt Fe/Mn 

N. Mariana arc crusts 1 12-23 12 16 0.14 0.13 0.04 0.09 0.65 0.02 9.6 0.38 0.08 1.53 

N. Mariana Mn-sandstone 1 9-18 17 6.8 .02 .03 .04 .01 .32 .02 13.8 .09 .02 .51 

N. Mariana stratiform Mn 1 8-11 40 1.5 .01 .02 .01 .003 .07 .06 3.1 .04 .01 .05 

Tonga Ri,dfe-Lau Basin 2-13 15 20 .28 .21 .06 .13 .87 .03 4.2 .44 .12 1.34 

crusts-· 

Tonga Ridge-Lau Basin 2-12 43 1.5 <.01 .005 .01 .005 .06 .11 2.1 .03 .005 .04 

stratiform Mn2 

Tonumea Island Tonga2 1-4 71 5.6 .03 .002 .02 .01 .02 .02 .08 

Pacific hydrogenetic crusts4 36-319 22 15 .63 .44 .08 .16 .98 .04 5.1 .48 .262 .81 

Clarion-Clipperton ferro- 43-409 29 6.6 .23 1.22 .99 .048 .61 .05 7.8 .23 .2 

manganese nodules5 

1

Hein, Fleishman, and others, 1987. 2

Hein and others, 1988. 3

Koski and others, 1985. 4

Hein, Morgenson, and others, 1987. 5

McKelvey and others, 1979. 

USGS Research on Mineral Resources-1989 Program and Abstracts 29 
Marine Science and Technology. Honolulu. Hawaii, May 

16-20, 1988. p. MRM3/83-MRM3/88. 

Hein, J.R., Morgenson. L.A., Clague, D.A., and Koski, R.A .. 

1987. Cobalt-rich ferromanganese crusts from the Exclusive Economic Zone of the United States and nodules from 

the oceanic Pacific, in Scholl, D.W .. Grantz. A., and 

Vedder, J .. eds., Geology and resource potential of the 

continental margin of western North America and adjacent 

ocean basins: Houston, Texas, Circum-Pacific Council for 

Energy and Mineral Resources, Earth Science Series, v. 6, 

p. 753-771. 

Koski, R.A .. Hein, J.R .. Bouse, R.M., and Sliney, R.E., 1985, 

Composition and origin of ferromanganese crusts from 

Tonga platform. southwest Pacific. in Scholl, D.W., and 

Vallier, T.L., eds., Geology and offshore resources of 

Pacific island arcs-Tonga region: Houston, Texas, CircumPacific Council for Energy and Mineral Resources, Earth 

Science Series, v. 2. p. 179-186. 

McKelvey, V.E .. Wright, N.A., and Rowland, R.W., 1979. 

Manganese nodule resources in the northeastern equatorial 

Pacific. in Bischoff. J.L.. and Piper. D.Z., eds., Marine 

geology and oceanography of the Pacific manganese nodule 

province: New York, Plenum, p. 747-762. 

Seasonal Variations in Concentrations of 

Helium and Carbon Dioxide in Soil Cases at 

the Roosevelt Hot Springs Known Geothermal 

Resource Area, Utah 

Margaret E. Hinkle 

Although soil gases are frequently collected for 

geochemical exploration, variations in concentrations of the 

gases measured and the causes of the variations are not 

thoroughly understood. To increase understanding of these 

variations and their causes, concentrations of He, C02 , 0 2 , 

and N 2 were measured in soil gases collected regularly for 

several months from sites at the Roosevelt Hot Springs 

Known Geothermal Resource Area (KGRA), Utah. Soil 

temperature, air temperature, percent relative humidity, 

barometric pressure, and amounts of rain and snowfall also 

were measured to determine the effect of meteorological 

parameters on concentrations of the measured gases. Sample collection and meteorological measurements were made 

by employees of the Chevron Resources Company Geothermal Division, which operates the powerplant at the KGRA. 

The Roosevelt Hot Springs KGRA is located about 20 

km northeast of the town of Milford, in Beaver County, 

southwestern Utah. The producing part of the geothermal 

field is bounded on the west by a wide north-south-trending 

fault zone called the Opal Mound fault and on the east by 

the foothills of the Mineral Mountains. Previous studies 

showed anomalous concentrations of He and C02 over the 

producing field. 

Four sites were selected for soil gas collection. Site A 

was located directly over the producing geothermal field, 

and sites B, C, and D were located peripheral to the field. 

Soil gases were collected from hollow probes at 0. 75-m 

depth in the ground; the probes were left in place throughout 

the study. 

Data from the study indicate that considerable seasonal variation exists in concentrations of C02 and He in 

soil gases. Concentrations of C02 and He varied throughout 

the year at all the sites. The meteorological parameters that 

most affected the soil gas concentrations were soil and air 

temperatures. Moisture from rain and snow probably 

affected soil gas concentrations in an erratic manner. 

However, small variations in meteorological parameters did 

not appear to affect measurements of anomalous concentrations in samples collected within a time period of a few 

days. 

At sites B, C, and D, soil and air temperatures 

correlated positively with concentrations of C02 and 

inversely with concentrations of He. Concentrations of C02 

at these sites averaged about 10 times the concentration of 

C02 in the air during the winter but about 25 times this 

concentration in the air during the summer. Concentrations 

of He at these sites were slightly above the concentration of 

He in the air during the winter and slightly below this 

concentration in the air during the summer. There was no 

correlation between concentrations of He and C02 ; this lack 

of correlation suggests that most of the He and C02 came 

from atmospheric air. Concentrations of 0 2 and N 2 in the 

soil gases were about the same as 0 2 and N2 concentrations 

in the air. This similarity suggests that the soil gas samples 

at these sites were composed mostly of atmospheric air. 

However, concentrations of C02 at site A over the 

geothermal field were 50 to 100 times greater throughout 

the year than at the peripheral sites. Concentrations of He at 

this site were 2 to 4 times greater throughout the year than 

at the other sites. In contrast to sites B, C, and D, 

concentrations of C02 and He at site A were higher during 

the winter and lower during the summer. In addition, 

concentrations of C02 and He were closely correlated, and 

this correlation suggests that C02 and He were related to the 

geothermal activity. Concentrations of 0 2 and N 2 at this site 

were about 60 to 70 percent of these concentrations at the 

other sites and indicate that samples from site A had a much 

lower component of atmospheric air than the other samples. 

Geology and Origin of the Jerritt Canyon 

Sediment-Hosted Disseminated Cold Deposits, 

Nevada 

A.H. Hofstra, G.P. Landis, R.O. Rye, D.j. Birak, A.R. 

Dahl, W.E. Daly, and M.B. jones 

The Jerritt Canyon district is located in the Independence Mountains, 80 km northwest of Elko, Nev. The 

district contains eight ore deposits distributed across a 16-

30 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
by 16-km area. The Enfield Bell mine has produced about 

1.5 million ounces of gold from 3 of these deposits and has 

additional proven reserves of 2.8 million ounces. Ore grade 

averages 0.142 oz/ton. The deposits are disseminated, 

epigenetic, stratabound bodies that are hosted in miogeoclinal carbonaceous limestones, carbonaceous calcareous 

siltstones, and cherts of the Upper Ordovician to Lower 

Silurian Hanson Creek and Lower Silurian to Lower Devonian Roberts Mountains Formations. These rocks are 

exposed locally in windows through overlying eugeoclinal, 

siliceous sedimentary and volcanic rocks of the Ordovician 

Snow Canyon Formation. 

The district has a long and complex structural history 

consisting of at least six episodes of deformation. (1) Early 

Paleozoic tectonism produced local disconformities 

between the Roberts Mountains and Hanson Creek Formation s. (2) Early Mississippian east-west compression 

(Antler orogeny) thrust the older Snow Canyon Formation 

over the younger Roberts Mountains and Hanson Creek 

Formations along the Roberts Mountains thrust. Exposures 

of the thrust in the mine show a wide zone of anastomosing 

fault strands, tectonic foliation , and rotated blocks. These 

features are typical of large regional thrusts. (3) North-south 

compression (Sonoran orogeny?) produced east-westtrending,south-verging folds, south-directed thrusting, and 

related northeast- and northwest-trending fractures. (4) 

East-west compression (Laramide? Sevier? orogeny) produced north-south- to northwest-trending, largewavelength, open folds and east-west- and northeasttrending faults and fractures. (5) West-southwest-eastnortheast extensional tectonism ( ~ 35-10 my) produced 

northwest-trending high-angle faults. (6) West-northwesteast-southeast- to east-west-directed extension produced 

basin-and-range-style block faulting (~I 0 my-Present) and 

north-northeast-trending , high-angle , normal faults that further dissect the range. The orebodies are most often 

localized along east-west- and northeast-trending highangle fault and along low-angle faults but also occur in the 

limbs of east-west-trending folds, along northwest-trending 

high-angle faults, and at intersections of these features. 

Although intrusive rocks are uncommon in the district, three types have been recognized. (I) A small diorite 

stock (30 by 150 m) that was dry and unreactive with the 

surrounding carbonate host rocks occurs in the southern part 

of the district. It is within 150 m of gold mineralization, and 

yet it is unaltered. (2) Several small ( <6 m wide) porphyritic andesite dikes that commonly have northwest orientations are sparsely distributed across most of the district and 

may be contemporaneous with the 17 to 14 my old 

northwest-trending Northern Nevada rift. These dikes are 

propylitically altered to chlorite, smectite, calcite, and 

pyrite. and some of these dikes are mineralized. (3) Porphyritic mafic dikes that were probably emplaced during 

basin-and-range magmatism (<I 0 my?) occupy northnortheast-trending fractures, are unmineralized, propylitiThe white mineral is stibiconite Sb+3

Sb/ 50 6(0H) a common alteration product of stibnite. The sample is from the 

Enfield Bell mine in the jerritt Canyon district in northern 

Nevada. [Hofstra and othe rs abstract] 

cally altered, and crosscut mineralization. The absolute 

ages of these rocks are currently under investigation. 

Detailed mineralogic, petrographic , geochemical, 

fluid inclusion, and stable isotope studies of jasperoid show 

that gold deposition was a result of the mixing of two 

meteoric fluids having contrasting water-rock exchange 

histories. The ore fluid underwent extensive exchange with 

wallrocks at low water-rock ratios and elevated temperatures to produce an 180 -enriched, moderately acid, ClC02-H2S-rich brine . This fluid scavenged gold from rocks 

along fluid flowpaths and transported it as a bisulfide 

complex. The other fluid was an oxidizing, very low 

salinity , near-neutral pH fluid that exchanged very little 

with wallrocks. Jasperoid produced during the mixing of 

these two fluids shows a direct correlation between 180 and 

log gold concentration . Most of the gold precipitated at the 

onset of mixing when small increases in f02 destroyed the 

bisulfide ligand. Fluid inclusion data indicate that gold 

deposition took place at depths greater than 1 km, and 

possibly as deep as 5 km , at temperatures of 200 to 250 °C. 

The geologic relations suggest that mineralization 

took place after deformation that produced east-west-, 

northeast-, and northwest-trending high-angle faults and 

before or during basin-and-range magmatism and block 

faulting . At present there is no evidence to indicate that 

mineralization is related to a localized intrusive heat source. 

Our current hypothesis is that mineralization is related to 

extension that allowed meteoric water to circulate along 

open faults to great depths where it was heated, due to high 

regional heat flow, underwent extensive exchange with 

wallrocks, and scavenged gold. In the upwelling part of the 

system, the ore fluid was focused along open fracture 

systems, especially east-west- and northeast-trending faults. 

Gold deposition occurred at sites where the ore fluid 

USGS Research on Mineral Resources-1989 Program and Abstracts 31 
encountered oxidizing unexchanged meteoric waters 

descending along permeable pathways below the Roberts 

Mountains thrust. The Snow Canyon Formation is rarely 

mineralized, except within a few feet of mineralizing 

structures, and apparently acted as a hydrologic barrier to 

upwelling ore-forming fluids. The deposits in the Jerritt 

Canyon district share many features with other sedimenthosted disseminated gold deposits in Nevada, and the results 

of this work may have important implications for the origin 

and age of many of these deposits. 

The Getchell Trend Airborne Geophysical 

Demonstration Project, North-Central Nevada 

D.B. Hoover, V.j.S. Grauch, M.D. Krohn, V.F. Labson, 

and j.A. Pitkin 

Today, the search for minerals is increasingly focused 

on methods for exploration in covered areas. Airborne 

geophysical methods look below the cover or identify subtle 

features within the cover and provide important data early in 

an exploration or assessment program. The U.S. Geological 

Survey (USGS), as part of its Development of Assessment 

Techniques program, is conducting an airborne geophysical 

demonstration along the Getchell trend in Humboldt 

County, Nev., to illustrate the advantages of a multidisciplinary approach to exploration and assessment. The primary objective of the program is to evaluate the use of 

multiple airborne methods for exploration through cover. A 

secondary objective is to determine the geophysical signatures of ore deposits in the study area. 

The Getchell trend was chosen for study because of 

the presence of five known Carlin-type gold deposits 

(Preble, Pinson, Getchell, Chimney Creek, and Rabbit 

Creek), inactive barite and tungsten deposits, and potential 

for molybdenum and additional gold mineralization. A 

unique opportunity is provided by the Rabbit Creek deposit, 

which is covered and over which the airborne and some 

ground studies will be completed prior to the start of 

mining. This airborne demonstration program is being 

conducted with close cooperation between industry and 

government in both the planning and execution of the study. 

The principal area to be flown is a 450-km2 strip on 

the eastern flank of the Osgood Mountains and adjacent 

pediment that includes all the known gold deposits. In this 

strip, thermal infrared and near-infrared to visible multispectral scanner remote sensing data will be acquired under 

contract. Low-level helicopter surveys will provide gammaray spectrometry, and combined very low frequency electromagnetic (EM), magnetic, and deep-looking multifrequency EM data, also under contract. The USGS will 

conduct tests of two experimental low-frequency EM techniques by using its own airborne systems. These experimental EM techniques are expected to increase exploration 

depths in comparison with commercially available systems. 

Nominal flight line spacing for the low-level surveys is 0.4 

km (1/4 mi). 

Airborne data will be acquired during September and 

October 1988, and the preliminary results will be presented 

at the McKelvey Forum. By using these integrated geophysical surveys, we expect to be able to map some lithologies 

and structures important for control of ore deposition from 

outcrop into covered areas. An additional important aspect 

of this research is acquiring better understanding of the 

formation of geochemical haloes within cover rocks and the 

detection of these haloes by shallow penetrating airborne 

methods. Research on the haloes is being closely coordinated with ground geologic, geochemical, and geophysical 

studies in the area. 

Flow Injection Analysis Applications in Mineral 

Resource Exploration and Environmental 

Chemistry 

Delmont M. Hopkins 

Flow injection analysis (PIA) can be extremely useful 

for geochemical and environmental analyses. PIA, coupled 

with a wide assortment of atomic spectroscopic, potentiometric, amperometric, and spectrophotometric detectors, is 

useful for trace-metal analyses. Other favorable qualities of 

PIA include minimal reagent consumption, minimum sample handling, excellent reproducibility (percent relative 

standard deviation (RSD) ::s 1.0-::::A.O), online pretreatments such as dilutions, standard additions, chemical reactions, preconcentration-separation, and a high sample 

throughput. Sample volumes typically range from 10 to 500 

J.LL, and, because samples, once injected, are completely 

contained in the system manifold, contamination is 

avoided. The sample zone disperses in an unsegmented 

carrier stream, and, because the dispersion response curve 

reflects a continuum of concentrations, any point (a transient signal) on the peak is valid to construct the calibration 

curve, provided that readout is taken from the corresponding section. PIA gradient techniques can also be exploited 

in reaction rate determinations, the study of chemical 

reactions, and other timely applications to environmental 

and mineral resource studies (Ruzicka, 1983). 

In our research, a method using PIA and flame atomic 

absorption spectroscopy (FAAS) was developed for the 

determination of gold in geologic materials. An organic 

solvent, methyl isobutyl ketone (MIBK), was the carrier 

stream and also the analyte extractant. A single rotary 

injection valve was placed between the carrier reservoir and 

spectrometer, which provided the carrier flow by aspiration. 

Samples and reference standards weighing 10 gm each were 

digested by using hydrobromic acid and bromine and then 

extracted with 2 mL MIBK. Approximately 1 mL of analyte 

32 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
extractant was typically recovered from each 2-mL treatment; however, the gold was equivalently dissolved in the 

separated phase and that dispersed in the aqueous layer. 

Three 250-J.LL injections were permitted-a distinct advantage compared with the usual continuous introduction of 2 

to 3 mL per sample. A detection limit of 5 ppb and an 

injection rate of 60 to 100 samples per hour were obtained. 

The precision determined at 50 ppb was 2 percent RSD, and 

the mean values (N = 6) determined for six geochemical 

exploration reference standards compared well with 

reported values. 

We plan to develop a rapid method for iron (II) and 

iron (Ill) speciation in rocks using FIA techniques and 

FAAS detection. The nature of the depositional environment (oxidizing or reducing) and possible routes of subsequent geochemical processes can be inferred from iron 

species in rocks. 

REFERENCE 

R~zicka, Jaromir, 1983, Analytical Chemistry, v. 55, n. 11, p. 

1040A. 

Regional Geophysical Studies for the International Falls and Roseau CUSMAP Projects 

Robert J. Horton, Val W. Chandler, Robert E. Bracken, 

and james E. Case 

Regional aeromagnetic and gravity data have been 

compiled for the International Falls and Roseau 1 o x 2° 

quadrangles by the U.S. Geological Survey (USGS) in 

cooperation with the Minnesota Geological Survey (MGS) 

and the Geological Survey of Canada (GSC). This compilation was done as part of the Conterminous United States 

Mineral Assessment Program (CUSMAP) for these two 

quadrangles located along the United States-Canadian border. Bedrock in the area is largely buried by Quaternary 

glacial deposits. Therefore, maps of the bedrock geology 

are based primarily on interpretation of regional aeromagnetic and gravity data supplemented by mapping of sparse 

outcrops and lithologic logging of a limited number of drill 

holes. Maps of gravity and magnetic anomalies are presented here along with various maps illustrating computerprocess-enhanced maps produced to aid geologic interpretation of the study area. 

Preparation of aeromagnetic maps includes compiling 

existing data from MGS and GSC that supplements new 

data collected by the USGS. The new airborne survey was 

flown with a line spacing of 1/4 mi at an elevation of 200 ft 

and using a high-precision proton sensor. A variety of 

navigation systems, including radar transponder, LORAN, 

and photo recovery, was used in the USGS project to 

overcome problems in flight line location over largely 

featureless terrain. The new USGS data were incorporated 

with the other aeromagnetic data to produce an IGRFcorrected total magnetic field map of quadrangles. 

Complete Bouguer anomaly gravity maps also were 

prepared as part of the CUSMAP study by using new data 

collected for the project, combined with a U.S. Department 

of Defense gravity data base. The new data were collected 

in cooperation with the Minnesota Department of Natural 

Resources-Division of Minerals and in cooperation with 

ongoing gravity surveys being done by the MGS. Detailed 

profiles were made by the USGS to better define important 

geologic features interpreted from preliminary gravity 

anomaly maps. The total data set was then processed to 

produce terrain-corrected Bouguer anomaly maps of the two 

quadrangles. 

The compiled aeromagnetic data were processed to 

compensate for inclination and declination of induced 

magnetic fields that offset boundaries of causative sources 

from magnetic highs. The reduction-to-the-pole program 

shifts the magnetic highs associated with dipolar magnetic 

lows to be more coincident with the source. Judicial use of 

this enhanced map with the original magnetic map facilitates geological interpretation of the geophysical data. 

Gravity and magnetic data were further processed to 

produce color-shaded relief (CSR), horizontal-derivative, 

and edge-enhanced maps. The CSR and horizontalderivative maps emphasize subtle linear features and level 

changes in anomaly intensity. For example, the CSR map of 

the reduced aeromagnetic data dramatically emphasizes 

linear anomalies due to northwest-striking diabase dikes. 

Edge-enhanced magnetic and gravity maps emphasize possible boundaries between geologic units that have contrasting densities and (or) susceptibilities. 

Interpretation of detailed profiles of ground gravity 

and magnetic surveys through computer modeling of possible bedrock contacts suggests size, shape, attitude, and 

physical properties of causative bodies. Geophysical interpretation of these maps can be integrated with interpretation 

of geologic data to yield an effective mineral resource 

assessment of the study area. 

Sulfur Isotope Characteristics of Bedded and 

Vein Barite Deposits, North-Central Nevada 

Stephen S. Howe 

Nearly all of the bedded barite deposits in northcentral Nevada are contained within lower Paleozoic eugeosynclinal rocks of the siliceous (western) assemblage that 

constitutes the upper plate of the Roberts Mountains thrust 

(the Roberts Mountains allochthon), emplaced during the 

Late Devonian-Early Mississippian Antler orogeny. In conUSGS Research on Mineral Resources-1989 Program and Abstracts 33 
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Shaded relief aeromagnetic map of the International Falls 1° by 2° sheet. 

This map is a compilation of U.S. Geological Survey, Minnesota Geological Survey, and Geological Survey of Canada aeromagnetic data. 

Lighter areas indicate magnetic field highs, and darker areas indicate 

magnetic lows. The apparent relief is produced by computer-generated 

northeast illumination. The irregular white line through the center of 

the image is the International boundary between Minnesota and 

Ontario. Prominent structural features within the map include the 

Quetico and Rainy Lake-Seine River faults, which strike east and eastnortheast across the northern third of the map. In the southern portion 

of the image, a northwest-trending dike swarm cuts a folded migmatite 

terrain . Map is approximately 100 by 150 km. [Horton and others 

abstract] 
trast, vein barite deposits in north-central Nevada occur (1) 

in pre-Antler rocks of the transitional and miogeosynclinal 

carbonate (eastern) assemblages that constitute the lower 

plate of the Roberts Mountains thrust, (2) in pre-Antler 

rocks of the siliceous assemblage, and (3) in post-Antler 

rocks deposited west of, within, and east of the Antler 

orogenic belt. 

Of the eight bedded barite samples analyzed to date, 

one is from a middle to late Ashgillian horizon in the 

Ordovician Valmy Formation, and seven are from early 

Famennian horizons in the Devonian Slaven Chert. The 

Ordovician deposit has a 834S value of +29.6 per mil, 

which, considering the fractionation between sulfate minerals and seawater sulfate of+ 1.6 per mil, matches exactly 

the 834S value of +28±2 per mil for Late Ordovician 

seawater sulfate (Claypool and others, 1980). The 834S 

values of the Devonian deposits are tightly clustered in two 

groups averaging +22.4 and +27.4 per mil, which, again 

considering the fractionation between sulfate minerals and 

seawater sulfate, are both nearly identical to the 834S value 

of +23±3 per mil for Late Devonian seawater sulfate. 

Although the isotopically lighter deposits are only 4 km 

northwest of the heavier deposits, the barite horizon is 

stratigraphically higher. This slight depletion in 34S with 

stratigraphic height was also observed in bedded barite from 

the Slaven Chert in south-central Nevada by Rye and others 

( 1978) and may be a result of the marine environment 

becoming increasingly oxic and open to seawater sulfate 

with the onset of the Antler orogeny, as Goodfellow and 

Jonas son (1984) have shown for the Famennian in the 

Selwyn basin of western Canada. 

The 834S values of 45 samples of vein barite range 

from +9.0 to +45.5 per mil; 85 percent of the values are 

between +20 and +35 per mil. Although the barite in most 

of the veins is slightly heavier isotopically than the barite in 

the bedded deposits, the sulfur in the veins could have been, 

with a few notable exceptions, derived from locally associated bedded barite or other crustal sources, and ultimately, therefore, from seawater sulfate. The exceptions 

are barite samples from three veins in the Valmy Formation 

from the Battle Mountain-Eureka trend and from two veins 

in the Dry Hills south of Beowawe. The three veins in the 

Valmy Formation are located near the Marigold gold mine, 

the Betty O'Neal silver-lead-gold-copper mine, and the 

Kattenhorn gold-antimony mine and contain barite that has 

834S values of +9.0, + 12.6, and + 10.8 per mil, respectively. The barite from the Marigold mine area is in 

jasperoid localized in a north-trending fault zone thought to 

be the feeder of the Marigold hydrothermal system; the 

sample has anomalously high gold, arsenic, and antimony 

and a gold-silver ratio greater than 11. In the Dry Hills, one 

vein at the northeast end near Scotts Gulch cuts Jurassic 

volcanic rocks and contains barite having a 834S value of 

+ 17.3 per mil. The vein at the southwest end is in the 

Pennsylvanian-Permian Brock Canyon Formation 5 km 

from the sulfur(±mercury±antimony) deposits at Hot 

Springs Point and contains barite having a 834S value of 

+ 10.5 per mil. These five barite samples depleted in 34S 

may contain sulfur derived, in part, from magmatic sources. 

Excluding these isotopically light samples, the 834S values 

of the vein barite samples appear to be independent of host 

rock age and lithology and of the types of other mineral 

deposits spatially and (or) temporally associated with the 

barite veins. In contrast, however, vein barite samples from 

the Battle Mountain-Eureka trend average more than 5 per 

mil lower than those from the Carlin trend, consistent not 

only with the more frequent occurrence of felsic intrusive 

rocks near the Battle Mountain-Eureka trend veins but also 

with the larger size of the intrusions. 

REFERENCES 

Claypool, G.E., Holser, W.T., Kaplan, I.R., Sakai, Hitoshi, and 

Zak, Israel, 1980, The age curves of sulfur and oxygen 

isotopes in marine sulfate and their mutual interpretation: 

Chemical Geology, v. 28, p. 199-260. 

Goodfellow, W.D., and Jonasson, I.R., 1984, Ocean stagnation 

and ventilation defined by 834S secular trends in pyrite and 

barite, Selwyn Basin, Yukon: Geology, v. 12, no. 10, p. 

583-586. 

Rye, R.O., Shawe, D.R., and Poole, F.G., 1978, Stable isotope 

studies of bedded barite at East Northumberland Canyon in 

Toquima Range, central Nevada: U.S. Geological Survey 

Journal of Research, v. 6, p. 221-229. 

Analysis of Concealed Mineral Resources in 

Nevada: Constraints from Gravity and Magnetic 

Studies 

Robert C. Jachens, Richard J. Blakely, and Barry C. 

Moring 

Regional gravity and magnetic studies of Nevada are 

being used to infer subsurface structure and lithology, 

primarily in areas beneath Cenozoic cover, as part of an 

analysis of concealed mineral resources of the entire State. 

Major goals of the geophysical studies are ( 1) to define the 

thickness of Cenozoic cover, (2) to constrain permissible 

lithologic identity of buried pre-Cenozoic basement, (3) to 

map the location and extent of concealed plutons, (4) to 

delineate known and identify unknown calderas, (5) to 

define areas of shallowly buried Tertiary volcanic rocks, 

and (6) to delineate areas (both exposed and concealed) of 

possible hydrothermal alteration. Primary statewide data 

sources for these studies are a digital isostatic residual 

gravity map based on approximately 71 ,000 point observations, a digital map of the magnetic field compiled from 38 

separate surveys and analytically continued to 300 m above 

terrain, detailed but widely spaced aeromagnetic profiles 

USGS Research on Mineral Resources-1989 Program and Abstracts 35 
Photo mosaic of the State of Nevada compiled from 

Landsat Multispectral scanner imagery by aerial photographers of Nevada. Scale 1:3,576,774 from original scale 

1:1,000,000. 

36 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
collected at 120m above the ground surface, a compilation 

of drill-hole data, a simplified digital geologic map, and 

digital topography. 

Combined analysis of these data sets will result in 

statewide maps showing approximate depth to dense (generally pre-Cenozoic) basement and the distribution of concealed but near-surface magnetic sources (generally Tertiary and Quaternary volcanic rocks). Other derivative 

products will include a ''basement" gravity map from which 

the effects of Cenozoic rock and unconsolidated sediments 

have been removed, maps showing subsurface density and 

magnetization boundaries, and a map showing the distribution of nonmagnetic Cenozoic volcanic rocks. 

These continuing investigations have yielded results 

important to the analysis of concealed mineral resources. 

Depth-to-dense-basement calculations indicate that, 

although more than 75 percent of northern Nevada is 

covered by young deposits, the deposits are thicker than 1 

km in only about 20 percent of the area. Likewise, magnetic 

data indicate that most basins in northern Nevada have 

volcanic and (or) granitic sources at shallow depth ( < 1 

km), especially along basin perimeters. The ''basement" 

gravity map reveals extensive areas of low gravity that 

probably reflect concealed felsic plutonic rocks and also 

shows evidence of major pre-Cenozoic crustal boundaries, 

one of which is spatially correlated with the Battle 

Mountain-Eureka trend of mineral deposits. Preliminary 

results also indicate a region in northern Nevada where 

many exposed volcanic and granitic rocks are relatively 

nonmagnetic. This region, coincident with the Battle Mountain heat-flow anomaly, may, in part, represent an area of 

subtle hydrothermal alteration. 

Volcanic-Tectonic Setting and Geology of the 

Paradise Peak Gold-Silver-Mercury Deposit, 

Nye County, Nevada 

David A. john, Robert E. Thomason, Charles W. Clark, 

and Edwin H. McKee 

The Paradise Peak deposit is a large hot-spring type 

gold-silver-mercury deposit discovered in 1983 in the low 

hills of the southwestern Paradise Range near Gabbs, Nev. 

It contained preproduction reserves estimated at 12 million 

tons averaging 0.097 oz gold and 3.53 oz silver per ton and 

greater than 50 ppm mercury. The deposit occurs in 

Oligocene and early Miocene volcanic rocks that have been 

divided into three sequences: an older sequence of 26 to 24 

Ma intermediate lavas, a middle sequence of 24 to 22 Ma 

silicic ash-flow tuffs, and a younger sequence of 20 to 15 

Ma intermediate lavas. Most of the orebody occurs in 

rhyolite tuffs in the lower part of the middle tuff sequence. 

Potassium-argon ages of hypogene alunite suggest that the 

orebody formed about 19 to 18 Ma, several million years 

after formation of the host rocks. 

The deposit is temporally and spatially associated 

with the younger intermediate lavas and occurs near the 

eastern edge of an early Miocene lava field that covers 

approximately 1,000 km2

• In the Paradise Range, these 

younger lavas are calc-alkaline or calcic (Peacock index 

approximately 61). They range in composition from 55 to 

70 percent Si02 , although most are andesites and dacites 

that have 60 to 65 percent Si02 • Compared to the older 

intermediate lavas, these younger lavas are higher in Ca and 

Sr and lower in Mg, K, P, and Rb. They generally have 

higher Sr:Rb (11-39) and K:Rb (328-581) and lower initial 87 Sr/86Sr (0. 7046--0. 7051) than the older lavas 

(Sr:Rb=5-18, K:Rb=248-355, initial 87Sr/86Sr=0.7050-

0. 7055). The genetic relation of the deposit to these 

younger lavas is unclear, because intrusive bodies are not 

present near the mine and have not been encountered in drill 

holes. 

The Paradise Peak deposit formed during a period of 

early Miocene (approximately 22 to 18 Ma) crustal extension. This early, pre-basin-and-range extension was 

widespread in west-central Nevada, extending from the 

Yerington district on the west to the San Antonio Mountains 

on the east and from the southern Stillwater Range on the 

north to the Goldfield district on the south. Early extension 

is indicated by major angular unconformities in early 

Miocene rocks (commonly >50°), rotated high-angle normal faults, and changes in the orientations and abundance of 

high-angle faults. Initiation of early extension broadly 

coincided with a regional change in the style of volcanism 

from dominantly silicic ash-flow tuffs, erupted between 

approximately 30 to 22 Ma, to eruption of intermediate 

lavas. Voluminous early Miocene (20-15 Ma) intermediate 

lavas are restricted to areas that underwent early extension. 

Other major precious-metal deposits that formed during or 

shortly following this extensional event include the 

Tonopah, Goldfield, Santa Fe, and, perhaps, Rawhide 

deposits. Early Miocene age precious-metal mineralization 

appears limited to areas of throughgoing high-angle faulting 

and is generally absent in areas of low-angle faulting and 

areas of steep stratal tilts. 

The age of early extension in the southwestern part of 

the Paradise Range is bracketed between 20 and 16 Ma. 

Although low-angle normal faults and steeply dipping early 

Miocene rocks are present less than 5 km northeast of the 

Paradise Peak mine, only high-angle faults and gently 

dipping rocks are present near the mine. High-angle faults 

that cut early quartz-pyrite alteration, control mercury 

mineralization, and are cut by mineralized hydrothermal 

breccias indicate that high-angle faulting occurred synchronous with ore formation. 

Preliminary studies of the deposit suggest that goldsilver mineralization occurred in at least three stages. 

Low-grade gold values (:::::::0.06 oz gold per ton) are associated with early silicification. This alteration consists of 

pervasive quartz+pyrite±opal and is mostly stratiform 

USGS Research on Mineral Resources-1989 Program and Abstracts 37 
within gently dipping tuffs. Early silicification is overlain 

and partially replaced by alunitic alteration (alunite+quartz 

±opal ±kaolinite±jarosite) that occurs in a 20- to 40-

m-thick blanketlike acid-leach zone developed primarily in 

intermediate lavas. Most high-grade ore (0.4-1.0 oz gold 

per ton) occurs in hydrothermal breccias that crosscut early 

quartz-pyrite and alunitic alteration. These breccias contain 

subrounded to angular clasts of silicified, locally leached 

tuff and alunitized intermediate lava in a matrix of darkgray to black quartz, barite, and local sulfide minerals. 

Breccias vary from matrix to clast supported and commonly 

show evidence of multiple stages of brecciation. A third 

stage of gold mineralization consists of coarser grained 

gold-filling vugs and coating fractures. Most mercury 

mineralization postdates gold mineralization and occurs as 

cinnabar coating fractures and filling vugs in breccias and 

silicified tuffs. 

The Applications of Airborne Radar for Mineral 

and Energy Resources Exploration 

john E. Jones, Allan N. Kover, and Bruce F. Molnia 

Since 1980, the U.S. Geological Survey (USGS) has 

been collecting side-looking airborne radar (SLAR) data in 

support of research for mineral and energy resources exploration and other earth-science applications. Radar systems 

provide an unsurpassed source of terrain information 

because of their ability to produce images without regard to 

cloud cover or light conditions. Radars provide their own 

source of illumination; as a consequence, the radar beam 

can be directed to provide optimum look direction and range 

of depression angles to enhance structural features for 

particular applications. Because SLAR' s transmit directed 

illumination at an oblique angle, usually between 10° and 

30°, subtle features such as faults, fracture zones, and salt 

domes often can be identified more easily on radar images 

than on conventional aerial or space photographs. The 

return signal from the radar beam is affected by variations in 

surface roughness, slope, topographic expression, moisture, and the dielectric effects of the materials irradiated. 

These characteristics have enabled interpreters to differentiate lithology, vegetation, soil, and rock types in some 

localities. Tonal anomalies on the radar images have been 

useful in identifying peat deposits in Maine and locating 

uraniferous breccia pipes in Arizona. 

The USGS has compiled 195 radar mosaics of 1 o x 2° 

quadrangles at 1:250,000 scale. These mosaics have been 

used, in conjunction with geologic mapping, for structural 

studies in areas of mineral or energy resource potential from 

the Appalachians to the Western Overthrust Belt. Many 

quadrangles in the area have been studied under the USGS 

CUSMAP (Conterminous United States Mineral Assessment Program), AMRAP (Alaska Mineral Resource 

Assessment Program), and State cooperative programs. 

The USGS has acquired radar image data of more 

than 30 percent of the conterminous United States and 

Alaska, and all of Puerto Rico and the American Virgin 

Islands. Mosaics, image strips, and indexes can be ordered 

from the USGS EROS Data Center, Sioux Falls, SD 57198. 

Computer compatible tapes are available for data collected 

since 1985. 

Tertiary Tectonic Evolution of the Central 

Walker Lane, Western Nevada 

Richard P. Keller, JohnS. Oldow, Richard F. Hardyman, 

and John W. Geissman 

The Walker Lane of western Nevada is an important 

northwest-trending boundary region that stretches from Las 

Vegas, Nev., to Honey Lake, Calif. Within this region, the 

structural grain has a north-northwest orientation in contrast 

to the typical north-northeast-trending basin-and-range 

structural grain of elongate fault-bounded mountains to the 

east. 

The central part of the Walker Lane is characterized 

by an en echelon series of linear, throughgoing and rangebounding, northwest-trending faults. Within this region, 

30- to 3.5-Ma Tertiary volcanic and interlayered sedimentary rocks unconformably overlie a basement composed of 

Mesozoic plutons and deformed pre-Tertiary rocks. Tertiary 

rock attitudes vary from flat lying to nearly vertical; dips are 

especially steep in rocks adjacent to large-scale fault zones. 

A model for the tectonic evolution of the central 

Walker Lane is based on (1) a compilation of detailed 

geologic maps, keyed to a framework that incorporates 

radiometric age data, tilt domains, and sequence stratigraphy within the 30- to 3.5-Ma Tertiary section; (2) structural 

fabric data from the pre-Tertiary basement; and (3) paleomagnetic data from pre-Tertiary plutonic bodies within the 

region. On the basis of these data sets, three structural 

domains are recognized. 

Domain I.- Are ally restricted regions in which both 

the pre-Tertiary basement and the unconformably overlying 

Tertiary section are strongly tilted. This domain includes 

the Yerington and Hall districts. 

Domain II. -A broad region bordering the central 

Walker Lane on both the east and west, in which the 

pre-Tertiary and Tertiary sections are essentially until ted by 

Tertiary-age deformation and where dips of the Tertiary 

section generally do not exceed 25°. 

Domain III. -A 70-km-wide, northwest-southeasttrending zone of linear, subparallel, strike-slip faults. The 

zone covers more than 6,000 km2 between Yerington and 

Tonopah, Nev. This part of the Walker Lane is characterized by a strongly tilted Tertiary section (attitudes ranging 

from 25° to nearly vertical) that is structurally detached 

from an untilted pre-Tertiary basement. 

38 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
NO 

TILT-ROTATIO 

[d ._1 Tertiary 

IWL~ A pre-Tertiary/pluton 

TILT-ROTATION 

ftiffffffffftfl Tertiary 

Tertiary+ basement 

~ pre-Tertiary/pluton 

Walker 

Lane 

Regional domains (1, II, Ill) of tilt of Tertiary and pre-Tertiary rocks in the central Walker Lane, west-central Nevada. 

[Keller and others abstract] 

The stratigraphic-structural relations in the Tertiary 

section and the structural fabric data in the pre-Tertiary 

basement, combined with age, paleomagnetic, crosscutting 

fault and fault-controlled dike orientation data, provide 

constraints for an interpretation of the tectonic evolution of 

the central Walker Lane. The model requires a clockwise 

rotation of the least principle stress direction from northnortheast to south-southwest to northwest-southeast from 

approximately 30 Ma to the present. Between 30 and 19 

Ma, the central Walker Lane experienced north-northeast to 

south-southwest extension that resulted in east-westtrending half-grabens (well preserved in structural domain 

II) and left-lateral strike-slip on northwest-trending highangle faults and kinematically related detachment faulting 

in domain III. Between 19 and 10 Ma, extension was 

oriented east-west and dominant normal faulting and rotation occurred about north-south-trending faults in domain I; 

strike-slip occurred on preexisting east-west faults (evidence preserved in domain II); and dikes were emplaced 

along northwest-southeast-trending high-angle faults in 

domain III, with some rotation of earlier low-angle detachment faults. From about 10 Ma to present, the central 

Walker Lane has experienced northwest -southeast -oriented 

extension resulting in predominant right-lateral slip on 

northwest -southeast -trending high-angle faults. 

Chemical Analysis of Ocean Floor Manganese 

Crusts 

Herbert Kirschenbaum, F.T. Manheim, P.j. Aruscavage, 

and C.M. Lane-Bostwick 

In recent years, interest in the chemical composition 

of ferromanganese crusts from the ocean floor has 

increased, in part, because these crusts are potential sources 

of metals such as cobalt, manganese, and nickel. We are 

conducting a worldwide survey of the occurrence and 

composition of these crusts. The crusts show geographic 

variations in composition. The concentration of the elements in the ferromanganese-oxide phase, especially Co, 

Ni, Cu, Zn, Ce, Pb, As, Pt, and Cd, reflects the timeUSGS Research on Mineral Resources-1989 Program and Abstracts 39 
integrated chemical concentrations in ocean bottom waters 

and therefore is of considerable geochemical interest. In 

support of the survey of manganese crusts, we are analyzing 

large numbers of such crusts and have attempted to optimize 

analytical techniques. Various procedures for decomposing 

these crusts were tested, but the best results were obtained 

by using three separate methods for different groups of 

elements. (1) Because of the volatility of silicon tetrafluoride, open-system hydrofluoric acid dissolution results in 

loss of silicon. Therefore, a fusion of the sample with 

lithium metaborate-tetraborate mixture, similar to that used 

for the routine determination of rock-forming major elements in silicates, is used for silicon and sodium decomposition. However, because of the large blanks and high 

dilutions required to lower the salt content from the fusion, 

an acid decomposition was most useful for analyzing the 

trace and minor elements. (2) The decomposition for 

arsenic presented a special problem in that its fluoride is 

also volatile, and special precautions must be taken to avoid 

loss when using a hydrofluoric digestion. However, we 

found that greater than 95 percent of total arsenic was 

leached by using hydrochloric acid from a test set of 

nodules when compared with a total decomposition of the 

sample by using hydrofluoric acid in a teflon-lined bomb, 

thus making for simpler sample processing. (3) High 

contents of manganese and iron in the crusts cause severe 

spectral interference in fixed-slit inductively coupled 

plasma-atomic emission spectrometric analysis for arsenic, 

cadmium, and chromium. However, these elements are 

adequately determined by graphite furnace atomic absorption. 

Gravity and Magnetic Anomaly Patterns in 

Mineral Resource Exploration, Hailey 

CUSMAP, Idaho 

M. Dean Kleinkopf 

Mines and prospects of precious metals are widely 

scattered in the area of the Hailey CUSMAP (Conterminous 

United States Mineral Assessment Program) project. Many 

of the deposits are associated with granitic intrusions and 

fault zones of the trans-Challis fault system. The Hailey 

gold belt is of particular interest. The study area also covers 

the western part of the Idaho Falls 1 o x 2° sheet. 

Interpretation of aeromagnetic and gravity anomaly 

data is an integral part of the study. The anomaly data are 

applied in conjunction with geologic investigations to map 

buried intrusive complexes, delineate major fault and shear 

zones, and identify localities that might be hydrothermally 

altered or mineralized. The aeromagnetic anomaly data are 

applicable for direct detection of mineralized features, and 

the gravity anomaly data define structural settings and 

distinguish low density Tertiary granitic intrusions from 

Cretaceous granitic intrusions of the Idaho batholith. 

Three crustal provinces can be distinguished by their 

contrasting aeromagnetic and gravity signatures and provide 

a framework for the mineral resource evaluation. (1) In the 

northwest, Cretaceous granitic terranes of the Idaho batholith are weakly magnetic and have slowly varying, highly 

negative Bouguer anomaly values. (2) In the northeast, 

heterogeneous terranes of thrust- and block-faulted Paleozoic sedimentary rocks, Precambrian metamorphic rocks of 

the Pioneer Mountains core complex, Tertiary granitic 

rocks, and deposits of Eocene Challis and Miocene volcanic 

rocks produce a variety of weak to strong magnetic anomalies. This assemblage gives an overall negative mass effect 

on the gravity field similar to that of the Idaho batholith. (3) 

In the south, the Snake River Plain province, composed 

predominantly of Cenozoic basalt, is much more magnetic 

and is denser than the terranes to the north. Boundaries 

between the three provinces are irregular. Granitic blocks 

probably locally underlie basalt near the northern margin of 

the Snake River Plain. 

The highest magnetic values correlate spatially with 

high elevation Tertiary epizonal granitic intrusions. Examples include the Sawtooth batholith, north of Atlanta; the 

stock at Steel Mountain, just north of Rocky Bar; and the 

major intrusion, just east of Twin Springs. These plutons lie 

along the northwest side of a prominent northeast-trending 

steep magnetic gradient zone that suggests a buried shear 

zone perhaps related to northeast structures of the transChallis fault system. Regional faults, such as the Deer Park, 

Montezuma, and Sawtooth faults and correlative magnetic 

trends, systematically change strike from south to southeast, north of the postulated shear zone to southeast on the 

south side of this steep gradient zone. Along the magnetic 

gradient zone, the gravity map exhibits low amplitude 

anomalies and subtle changes of gradient. 

The Hailey gold belt is a zone of variably mineralized 

ground and precious-metal localities that extends from the 

White Knob and Pioneer Mountains for some 150 km 

southwest across the southeastern part of the Idaho batholith. The magnetic and gravity anomaly data superimposed 

on the generalized geology illustrate the geophysical signatures of the various structural and lithologic units within the 

batholith and suggest projections of these features in the 

subsurface. Magnetic and gravity derivative maps enhance 

definition and interpretation of the anomalies. 

Caraway-Back Creek Volcanic Center, Central 

Slate Belt, North Carolina: Newly Recognized 

Thermal Source for Precious- and Base-Metal 

Mineralization 

Robert P. Koeppen and Terry L. Klein 

The Carolina slate belt (CSB), a probable volcanic 

arc remnant of late Precambrian to Cambrian age that 

40 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
extends 600 km from Virginia to Georgia, consists of 

weakly metamorphosed volcanic, sedimentary, and intrusive rocks. A variety of mineral deposits occur in the slate 

belt, including those that contain precious and (or) base 

metals. Models for these deposits have generally favored a 

volcanogenic origin; however, because either constraining 

geologic details or adequate model analogs were not available, such models typically have been speculative about the 

mechanism of formation. Our studies suggest a connection 

between a rhyolitic volcanic-intrusive complex and associated epithermal gold deposits that occur along the boundary 

between the Eocambrian-Cambrian Uwharrie and Tillery 

Formations near Asheboro, N.C. Although our studies are 

not completed, the available field, geochemical, and petrological data warrant a preliminary summary of the relationship between the volcanic and intrusive rocks at Back Creek 

and Caraway Mountains (CBCV) and spatially associated 

gold deposits. 

The CBCV eruptives occur in the lowest part of the 

Tillery Formation, where they were deposited on and 

crosscut the dominantly rhyolitic Uwharrie Formation. 

They form domes, pyroclastics, and derivative epiclastics, 

consisting dominantly of quartz-plagioclase phyric- and 

plagioclase phyric- (quartz-free) rhyolite; these are interbedded with regionally extensive argillites and are cut by 

gabbroic intrusives. The eastern half of the volcanic complex is inscribed by a microgranophyre ring dike; near the 

western end of this dike, the volcanic rocks are cut by a 

granophyric subvolcanic stock that is several kilometers in 

diameter. The stock and dike appear to be contemporaneous. 

Four gold deposits (Hoover Hill, Scarlett, Sawyer, 

and New Sawyer) and several alteration zones, each characterized by quartz or zoned quartz-K-feldspar veins and 

(or) sulfide disseminations in strongly silicified or chloritesericite-altered host rocks, surround the ring dike structure 

at a distance of 1 to 5 km. These polymetallic (Zn, Cu, Pb, 

Ag, Mo) gold deposits are relatively base metal rich 

(0.5->2 percent base metals), have silver-gold ratios of 0.5 

to 200, and probably formed at relatively deep levels (>0.5 

km?) within fossil hot springs systems related to the CBCV. 

The solutions responsible for the deposits, based on alteration assemblages and stable isotope data (oxygen, sulfur), 

and by analogy with other deep-level polymetallic vein 

systems, were probably near-neutral pH, chlorine-bearing 

fluids that have a large component of meteoric water and an 

igneous sulfur source. These characteristics are shared with 

many precious-metal deposits in the Western United States, 

such as those at Creede, Silverton, Comstock Lode, 

Tonopah, and Bodie. 

Anomalous Cu, Zn, Ag, and Au occur at locations 

adjacent to and within the CBCV and reflect both known 

deposits and areas having no previous production. An area 

of relatively high total-count airborne radiometric values 

also effectively outlines the felsic volcanic center. 

Identification of the CBCV and its possible role in the 

formation of epithermal gold mineralization bears significantly upon future exploration strategies in the CSB. In the 

past, exploration in the slate belt has commonly used an 

exhalative model in which the gold was believed to be 

roughly stratabound. Recognition of probable epigenetic 

synvolcanic mineralization surrounding a mappable volcanic center requires development of an alternative exploration strategy, in which the integration of geologic, 

geochemical, isotopic, and geophysical studies may prove 

successful. 

Composition and Geologic Setting of Stratiform 

Manganese Deposits in the Southern Basin and 

Range Province, Arizona and Nevada 

Randolph A. Koski, Robin M. Bouse, James R. Hein, and 

Marilyn L. DeRosa 

The largest accumulations of manganese in the western Cordillera of the United States are stratiform manganeseoxide deposits in Miocene sedimentary and volcanic rocks 

of the southern Basin and Range province, Nevada and 

Arizona. The host rocks are lacustrine-alluvial sequences 

that were deposited in structural basins during Neogene 

crustal extension. 

Gently dipping manganese-bearing strata on the west 

flank of the Artillery Mountains in west-central Arizona 

include fanglomerate, sandstone, siltstone, felsic tuff, and 

limestone. The manganese mineralization is distributed 

within sedimentary facies that range from alluvial fan 

deposits near the basin margin to thinly laminated finegrained clastic deposits and limestone in the basin interior. 

The manganese oxides hollandite, coronadite, and cryptomelane constitute deposits gradational from massive beds to 

thin interstitial films around sediment grains. Samples of 

stratiform manganese oxide contain high amounts of lead 

(to 14 weight percent), barium (5.0 weight percent), arsenic 

(0.5 weight percent), and uranium (40 ppm). 

At the Three Kids mine west of Lake Mead in 

southern Nevada, the stratiform manganese horizon occurs 

in a section of tuffaceous siltstone, sandstone, conglomerate, and tuff that is capped by gypsum. Potassium-argon 

ages of biotites from interbedded tuff units indicate that the 

manganese-bearing beds were deposited at approximately 

13.8 Ma. In the same district, the Virgin River manganese 

deposit on the north shore of Lake Mead consists of 

alternating manganiferous and ferruginous sandstone beds 

in a sequence of gypsum, gypsum-bearing sandstone and 

siltstone, green tuff, and lava flows of andesite and basalt 

compositions. The manganese mineralization in the Three 

Kids and Virgin River deposits consists of transported clasts 

of colloform manganese oxide (todorokite and coronadite), 

manganese-oxide cement (pyrolusite), and manganeseUSGS Research on Mineral Resources-1989 Program and Abstracts 41 
oxide cavity infillings (cryptomelane and coronadite). Bulk 

chemical analyses of manganese-rich samples show that the 

Three Kids deposit contains greater amounts of barium, 

strontium, and lead relative to the Virgin River deposit that 

contains more iron, copper, and arsenic. 

The occurrence, composition, and textural characteristics of the stratiform manganese deposits suggest that 

manganese was deposited from oxidized, low-temperature 

fluids in contact with unconsolidated clastic sediment on 

and below the floor of stratified saline lakes. The initial 87 Sr/86Sr (0. 71005-0. 71666) of evaporite and limestone 

interbedded with the manganese deposits are consistent with 

a lacustrine depositional environment. Lead isotope ratios 

for manganese samples from the Artillery Mountains and 

the Three Kids deposits are more radiogenic than their 

enclosing sedimentary and volcanic rocks and indicate that 

a source for manganese and other metals from Proterozoic 

and Mesozoic rocks is deeper in the crust. In contrast, the 

similarity of lead isotope ratios of the Virgin River deposits 

and their Tertiary host rocks implies a source of metals 

within upper levels of the crust. 

Study of the manganese deposits combined with 

ongoing regional framework investigations suggests that 

extensional tectonics, detachment faulting, volcanism, and 

manganese mineralization were synchronous during the 

Miocene in the southern Basin and Range province. We 

propose that the proximity of detachment surfaces to heat 

sources, such as the magma chambers of active volcanoes, 

resulted in thermal regimes suitable for the development of 

large hydrothermal convection cells. Normal faults bounding extensional basins in the upper plate above detachment 

faults may have been pathways for recharge of saline basin 

waters and discharge of metal-enriched hydrothermal fluids. 

Characterization of Carbon in Sediment-Hosted 

Disseminated Gold Mineralization at Jerritt 

Canyon, Nevada 

joel Leventhal and A.H. Hofstra 

An integrated multidisciplinary study of gold mineralization at Jerritt Canyon, Nev., is in progress. Gray, 

dark-gray, and black sediments in the Marlboro Canyon and 

North Generator orebodies indicate that these rocks are not 

oxidized with respect to carbon. Both ore and non-ore host 

rocks can be dark colored, and noncarbonate carbon content 

is not related to gold content. These rocks contain a few 

tenths to a few percent noncarbonate carbon. The term 

noncarbonate is used to distinguish carbon not bound to 

hydrogen from organic carbon in which carbon is bound to 

hydrogen. Normally rocks that have these levels of carbon 

are gray, but at Jerritt Canyon the rocks are darker because 

they have experienced higher temperatures at which organic 

matter catagenesis occurs. Contrary to published reports, 

the rocks do not contain significant amounts of humic acids, 

extractable hydrocarbons (bitumen), or carbonaceous material. 

Cryptocrystalline graphite, which occurs as angular 

fragments, vein fillings, and spherical blebs of carbon, can 

be recognized by reflected and transmitted light microscopy. J asperoid paragenesis indicates that these mineralogies are all premineralization. 

In addition to elemental analysis (carbon, hydrogen, 

and nitrogen content; Rock-eval) and X-ray diffraction, 

laser Raman spectroscopy has been used to study the 

carbon. Laser Raman spectra can distinguish between 

highly developed graphite crystals(> 1 micron in diameter) 

that exhibit a sharp peak near 1600 em - 1 and less welldeveloped crystals ( < 1 micron in diameter) that exhibit a 

broadened peak near 1600 em- 1 and another broad peak 

near 1350 em - 1

. The broadness, shape, and relative heights 

of these peaks are related to the size of the graphite crystal 

domain. The spectra from Jerritt c·anyon samples in jasperoid, carbonate, and shale are distinctively similar; they all 

indicate poorly ordered graphite crystals less than 0.03 

microns (cryptocrystalline). 

These measurements ( 1) confirm the maturity of the 

carbon as initially indicated by elemental analysis, Rockeva!, and X-ray diffraction, (2) further elucidate the nature 

of the carbon, and (3) based on paragenesis indicate that the 

carbon was matured early in the geologic history of these 

rocks prior to gold mineralization. 

Study of the Stratigraphy of the Gold-Bearing 

Preble Formation Near the Type Locality, NorthCentral Nevada-Some Benefits to Exploration 

Dawn j. Madden-McGuire 

Outcrops of the Lower Cambrian to Lower Ordovician Preble Formation of north-central Nevada extend from 

the northwestern flank of the Osgood Mountains southward 

into the Sonoma Range. The formation is the host rock for 

gold deposits in the Preble and Getchell mines in the 

Osgood Mountains, Humboldt County, Nev. The type 

locality of the Preble Formation is in the southern Osgood 

Mountains in Emigrant Canyon, at the site of the old Preble 

railroad station. Near the type locality, the age of the Preble 

Formation ranges from late Early Cambrian to Early Ordovician. The latter age is based on the identification of a recent 

collection of Early Ordovician graptolites from a Preble 

locality. In the type area, the Preble Formation is weakly 

metamorphosed, and the strata are tightly folded, plunge 

southward, and are structurally overturned to the west; 

strata dip eastward 40° to 75°. 

Some basic questions have remained unanswered 

during previous regional mapping in the Preble Formation. 

42 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
To answer some of these questions, mapping and sampling 

were done near the type locality at more detailed scales. The 

present study indicates that the stratigraphic succession 

consists of sedimentary quartzite, bedded barite, interbedded phyllite, and at least five subunits of limestone rather 

than only one limestone subunit repeated many times by 

folding. The thickness of the mapped strata is estimated 

crudely at 650 m, on the basis of the dip of strata and the 

distribution of outcrops of mapped units. The total thickness 

of the Preble Formation, variously estimated at 3,660 m and 

1 ,000 m in previous regional studies, is still unknown. 

Omission and offset of known subunits indicate the location 

of mappable faults. North-south-trending basin-and-rangeparallel faults and northeast-trending Humboldt structural 

zone-parallel faults occur in the mapped area. The Emigrant 

Canyon trend, which is parallel to faults and lineaments of 

the regional Humboldt structural zone, may be controlled 

by a fracture rather than by a fault because individual 

marker beds are not appreciably offset across Emigrant 

Canyon. 

Locally exposed subunits in the type area of the 

Preble Formation, from oldest to youngest, are (1) clastic 

fossiliferous limestone consisting of lenses of gray to brown 

bioclastic packstone and grainstone, (2) siliciclastic channel 

deposits consisting of fine-grained, micaceous, sedimentary 

quartzite, (3) bedded barite, (4) clastic limestone and local(?) 

conglomerate, (5) oolitic limestone (a marker bed), and (6) 

clastic, pale-orange, fossiliferous limestone (a marker bed). 

Subunits 1 and 4 have yielded fossils identified in a 

previous study as Early and Middle Cambrian, respectively 

(Rees and Rowell, 1980). The oolith locally is an ooid 

packstone consisting of silt-size ooids and interstitial micrite, an association suggesting deposition as a turbidite. 

The study of the stratigraphy and sedimentology of 

the Preble Formation should help identify favorable host 

rocks, lithologic subunits within the formation, structures, 

and patterns of alteration that may be associated with gold 

mineralization. The recognition of marker beds should help 

delineate faults and shear zones that are important to 

recognize in gold exploration in the Preble Formation; 

zones of broken and sheared rocks are thought to have 

formed the fluid pathways that focused and directed the 

silicifying and mineralizing fluids (Bagby and Berger, 

1985). 

REFERENCES 

Bagby, W.C., and Berger, B.R., 1985, Geologic characteristics 

of sediment-hosted, disseminated precious-metal deposits 

in the western United States, in Berger, B.R., and Bethke, 

P.M., eds., Geology and geochemistry of epithermal systems: Society of Economic Geologists Reviews in Economic Geology, v. 2, p. 169-202. 

Rees, M.N., and Rowell, A.J., 1980, Preble Formation, a 

Cambrian outer continental shelf deposit in Nevada: 

Brigham Young University Geology Studies, v. 27, pt. 1, 

p. 1-8. 

Minerals Information Office 

Susan M. Marcus, Raymond E. Arndt, Paul G. Schruben, 

Carl Carlson, and Jane Jenness 

The Minerals Information Office is a new, cooperative endeavor of the U.S. Geological Survey (USGS) and 

the U.S. Bureau of Mines (USBM) that is designed as a 

"one-stop shopping place" for mineral resource inquiries. 

The office is located in Room 264 7 of the Department of the 

Interior Building, 18th and C Streets N.W., Washington, 

D.C. The office provides information and access to USGS 

and USBM data bases, commodity specialists, and publications for the benefit of the public, industry, and Federal 

and State officials. The office also seeks to improve the 

exchange of information among the Federal agencies and 

other minerals-information generators and users. Under 

Secretary of the Department of the Interior, Earl Gjelde, 

and Assistant Secretary for Water and Science, James 

Ziglar, joined USGS Director Dallas L. Peck and USBM 

Director T S Ary in cutting a platinum ribbon at the opening 

ceremony on June 21, 1988. The event also inaugurated the 

new USGS Earth Science Information Center (formerly the 

Public Information Office). The Earth Science Information 

Center, adjacent to the Minerals Information Office, provides public distribution of USGS publications and maps. 

A dedicated computer system in the office can provide clients and users with responses to their questions 

while they wait. The USGS Resource-Oriented Computer 

System permits retrieval of graphic and tabular data on 

mineral deposits and occurrences throughout the world by 

using the Mineral Resource Data System (MRDS). The data 

base, which currently includes 70,000 MRDS records, also 

includes political and administrative boundaries, geology 

for selected areas, and a guide to selected USGS minerals 

research. These data may be searched in ways designed to 

meet each user's specific needs. Paper copies of graphic 

displays and tabular and textual information are prepared 

and distributed. 

The Minerals Information Office also serves as a 

collector of data useful to USGS scientists. Data are 

compiled, and digital files are acquired to enhance the 

breadth and depth of information available to the government researchers. Sources of data include Federal and State 

Government agencies and private industry. 

Mineral commodities are featured in a series of 

activities sponsored by the Minerals Information Office. 

Platinum and gold were the featured commodities during 

fiscal year 1988. Exhibits showed regions of the United 

USGS Research on Mineral Resources-1989 Program and Abstracts 43 
States thought to have potential for undiscovered traditional 

and nontraditional platinum resources. Gold-related activities included a series of well-received public lectures in the 

Interior Museum and distribution of fact sheets and brochures about gold. Samples of platinum ore from the 

Stillwater mine in Montana and gold ore from the Homestake mine in South Dakota were given away. 

The office has replied to both general and technical 

inquiries and is a favorite stop of visitors to the Interior 

Building. Additional Minerals Information Offices are 

being established in conjunction with USGS field centers in 

Tucson, Ariz., Reno, Nev., and Spokane, Wash. , to serve 

the needs of information users and USGS researchers in 

those regions. The western Minerals Information Offices 

will become operational during 1989. 

A Simplified Digital Geologic Map of Nevada for 

Regional Gold Resource Assessment 

S.P. Marsh , E. Sandoval, and ].L. Plesha 

A 1:500,000-scale geologic map of Nevada has been 

digitized by the U.S. Geological Survey (USGS) as part of 

a regional gold resource assessment program funded by the 

Bureau of Indian Affairs. The resource assessment involves 

interpretation and comparison of many different digital data 

sets. The digital geologic data base has been prepared for 

input into a computer geographic information system (GIS), 

used to facilitate interpretation. The objective of this presentation is to discuss construction of a simplified digital 

geologic map for use in GIS analysis of potential gold 

resources of Nevada. 

The original geologic map consists of more than 104 

distinct geologic units. These units have been simplified 

into 15 lithologic units on the basis of several different 

geologic models of basin-and-range gold-bearing systems. 

Additional guidance in combining geologic units was taken 

from preliminary interpretations of airborne magnetic , radiometric, and satellite data. For example, all Paleozoic 

carbonate rocks deposited in foreland basins (seven geologic units) have been grouped together. The simplified 

geologic units were digitized by using a USGS Open-File 

computer program, GSMAP (versions 4.0 and 5.0). This 

program and file format are compatible with IBM desk top 

or equivalent computers that use the MS-DOS operating 

system. 

The digital geologic map was prepared in several 

steps. The 1 :500 ,000-scale geologic map in stable-base 

form was divided into 18 sections. Hand-colored coding of 

the 15 simplified units facilitated digitization using 

GSMAP. The complete digital data set, transferred to a 

VAX 11/750, was edited and assembled into 1° x 2° 

quadrangles by using a commercial GIS computer program 

A pano ramic view of the Gold Quarry open pit, Carlin trend , Nevada . 

44 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
(ARC/INFO). Each file was then converted back into 

GSMAP format and returned to the IBM PC to format files 

for public distribution. The completed data set requires just 

over eight megabytes of uncompressed storage. 

GIS programs can be used for analysis of these and 

other digital data , including gravity, compiled airborne 

magnetic , and topography, available for the State of 

Nevada. Data interpretation has begun by using the GRASS 

program developed for GIS applications by the Army Corps 

of Engineers. This public domain program offers analytical 

methods particularly suited to analysis of these data. 

Grauch and Sawatzky (this volume) have used the 

correlations between digital structural features and digitally 

enhanced aeromagnetics to interpret tectonic features associated with gold mineralization. Correlation of carbonate 

units from the simplified digital geologic map with potassium lows interpreted from the airborne radiometric data 

indicates areas of favorable host rocks for certain types of 

gold-bearing systems. Generally, digital geologic data used 

with other digital data will provide further insight into the 

significance of correlated features associated with known 

gold deposits for inference of undiscovered resources. 

Evaluation of Multiple Geochemical Sample 

Media at the Betze Gold Deposit, Eureka 

County, Nevada 

j.H. McCarthy, Jr., j.A. Erdman, T.G. Lovering, and K.H. 

Bettles 

The Betze gold deposit, discovered by the Barrick 

Goldstrike Mines, Inc ., in 1986, is located along the Carlin 

trend in Eureka County, Nev. The northwest-trending 

orebody is up to 1 ,000 ft wide (northeast-southwest) and 

4,000 ft long (northwest-southeast). The mineralization is 

hosted in carbonate rocks of the Devonian Popovich Formation and is overlain by 800 to 1, 100 ft of mostly 

unmineralized siltstone and argillite. 

Five sample media were collected along one or more 

of three traverses that crossed over the deposit. The sample 

media were (I) rock outcrop, (2) soil, (3) vegetation 

(sagebrush), (4) pebbles (for coating analysis), and (5) soil 

gases. The east-west traverses were separated by about 500 

ft; sample intervals were 200 ft. 

Altered and mineralized bedrock samples were collected from five localities over the deposit, five localities 

USGS Research on Mineral Resources-1989 Program and Abstracts 45 
Barrick Goldstrike Mines, Inc.'s Post open pit. Oxidized ore is above a major zone of sulfide ore, Carlin trend, 

Nevada. 

west of the deposit, and seven localities east of the deposit. 

All were analyzed quantitatively for Au , Ag, As, Cd, Hg, 

Sb, and Zn by using atomic absorption methods; also 

semiquantitatively for 25 other elements by using emission 

spectroscopy. The highest values for gold (3.0 ppm), 

arsenic (5,000 ppm), and cadmium (7.9 ppm) were found 

in samples from an outcrop over the eastern part of the 

deposit. Cadmium is the only element that correlates 

significantly with gold (correlation coefficient=O. 76). High 

values for mercury (1.2 ppm), antimony (32 ppm), and 

copper (500 ppm) were also found in rocks over the deposit, 

but the highest values for mercury ( 1.8 ppm) and antimony 

(450 ppm) were 800 ft east of the deposit, and the highest 

values for zinc (3,000 ppm) were found 1,500 ft west of it. 

The rock samples that were highest in many trace elements, 

including gold, were silicified, brecciated, and contained 

fine-grained pyrite. 

On one traverse, the gold in soil was highest (0.0 12 

ppm) over the deposit, and on another traverse , it was 

highest (0.0 18 ppm), 1,500 ft east of the deposit. 

In sagebrush, the highest gold values were found east 

and west of the deposit. However, the highest values for 

arsenic (2,973 ppm), antimony (146 ppm), and galli um 

(156 ppm) were found in sagebrush samples over the 

deposit. 

Limonitic coatings from pebbles collected on the 

surface over and near the Betze deposit were analyzed by 

the oxalic acid leach method and were found to contain up 

to 42 ppb gold. Less gold was found in corresponding soil 

samples. Wherever bedrock samples contain measurable 

gold, adjacent pebble coatings contain several times background concentrations (2 ppb) of gold. Pebble coatings over 

and near the deposit consistently contain more Fe, Mn, Be, 

Co, Ni, Pb, V, and Ga and show a greater range in Ag, Ba, 

Cr, Cu, La, Mo, Sb, Sn, W, Y, Zn, and P than do either 

bedrock or soil samples. These coatings also show systematic variations in many elements; Mn , Co , Ni , and Zn are 

highest over the ore zone; Cr, La , Mo, Sb, and Y are 

highest 500 to 1,000 ft east of the ore zone; and W, Sn, and 

V are highest at the easternmost locality, 1,200 ft from the 

ore zone. 

Soil air was sampled at a depth of 2 ft , and the gases 

were analyzed at the site by using a truck-mounted mass 

spectrometer. Positive gas anomalies were found over the 

deposit on two of the traverses for ions having mass/charge 

46 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
12 (C+ ), 15 (CH3+ ), 26 (C2H2+ ), and 29 (C2H5 + ), and 

17 (NH3) and these anomalies may be related to organic 

matter associated with gold. Carbon dioxide, which is 

commonly enriched over sulfide deposits, was low and did 

not correlate with the deposit. Organic gas species show 

some promise as geochemical guides to concealed, 

sediment-hosted gold deposits. 

Geochemical anomalies in rocks and pebble coatings 

occur directly above the deposit. Anomalies in the other 

media (gas, soil, sagebrush) showed a halo or offset relation 

to the deposit. 

Multiple Ages of Disseminated Gold 

Mineralization Associated with Volcanic Cycles 

in Southwestern Utah and Adjacent Nevada 

W.R. Miller and j.B. McHugh 

Recent studies in the Richfield 1 o x 2° quadrangle, 

Utah, and adjacent areas in Utah and Nevada indicate five 

possible episodes and three types of disseminated gold 

mineralization. These episodes range in age from at least 27 

Ma, and possibly 39 Ma, to probably less than 5 Ma, and 

each is associated with a local volcanic cycle. The volcanic 

terrains of southwestern Utah and adjacent Nevada have 

been studied by Best and associates at Brigham Young 

University and by Steven and associates at the U.S. 

Geological Survey in connection with a Conterminous 

United States Mineral Assessment Program (CUSMAP) 

study of the Richfield quadrangle. Recent reexamination of 

geochemical data from the Richfield CUSMAP study and 

collection of additional samples from geochemically anomalous areas, altered areas, and mines have resulted in the 

recognition of multiple episodes of disseminated gold mineralization that took place in this part of the Basin and 

Range and High Plateaus physiographic provinces. 

The oldest deposits appear to have formed 39 to 35 

Ma. The age of mineralization is speculative and is based on 

proximity to dated volcanic rocks and gold deposits to the 

north and to nearby volcanic rocks of about 35 Ma. Further 

work to date this occurrence is in progress. These deposits 

are characterized by disseminated gold, hosted within 

carbonate rocks. High-angle normal faults acted as conduits 

for the hydrothermal fluids, and mineralization took place 

within favorable beds adjacent to the faults. The carbonate 

rocks are commonly silicified to jasperoid, which locally 

forms bodies that can be traced for several hundred meters 

along strike. Gold values up to 0.1 oz/ton are present at the 

surface. 

A somewhat younger period of gold mineralization 

took place at the Atlanta mine, Nevada, in association with 

the collapse of the Indian Peak caldera. Mineralization 

deposited gold in the topographic wall of the caldera and 

adjacent limestone beds. The age of mineralization can be 

bracketed by altered and unaltered tuff units at 28 to 27 Ma 

that occurred at the end of the caldera cycle. Other deposits 

of this age may occur along the margins of the Indian Peak 

and White Rock calderas, especially where carbonate rocks 

are present. 

The third period of mineralization deposited gold 

adjacent to and within fissures hosted by rhyolite lava flows 

of the 23 to 18 Ma Blawn Formation. Stateline mining 

district is an example of this age of mineralization, and 

other potential areas occur throughout the western part of 

the Richfield quadrangle from the Shauntie Hills to the 

Nevada border. 

Another episode of gold mineralization is represented 

by iron-oxide veins cutting the 13 to 12 Ma Steamboat 

Mountain Formation; these veins contain gold values up to 

400 ppb. These late Miocene rocks are considered to have 

potential for disseminated gold deposits similar to those 

hosted by Blawn Formation rhyolites. 

The youngest known gold mineralization took place 

in the southeastern part of the Richfield quadrangle where a 

zone several hundred meters wide and several kilometers 

long contains local quartz stockwork and a series of parallel 

quartz veins up to a meter wide. Open-space cavities lined 

by coxcomb quartz and sulfide minerals are present. Limited sampling has disclosed gold values up to 1 ppm at the 

surface. These veins and associated altered rocks appear to 

be associated with the 5 Ma Phonolite Hill rhyolite. 

Multidisciplinary Considerations in a Digital 

Geologic Map-Applications and Afterthoughts 

S.H. Moll, j.L. Dwyer, C.A. Wallace, j.E. Elliott, C.M. 

Trautwein, and J.E. Harrison 

The U.S. Geological Survey (USGS) has been digitizing geologic maps for use in a variety of geologic, 

hydrologic, and related resource investigations for more 

than 20 years. In the 1970's, capabilities to digitally capture 

information presented on a geologic map were limited both 

functionally and logistically. Consequently, early applications were directed at discipline-specific research and technique development activities. In the 1980's, computerbased geographic information system (GIS) technology has 

evolved to meet many of the USGS's increasing spatial data 

processing requirements. Capabilities to efficiently capture, 

edit, analyze, manipulate, arid display various elements of a 

geologic map offer new opportunities for application to the 

USGS's multidisciplinary investigations. To fully realize 

the data processing efficiencies offered by a modem GIS 

environment, immediate and foreseeable multidisciplinary 

requirements of the digital geologic map must be taken into 

account during its preparation. Experiences in the preparation and application of digital geologic maps during recent 

multidisciplinary GIS-based CUSMAP (Conterminous 

United States Mineral Assessment Program) and related 

investigations have resulted in the recognition of two 

USGS Research on Mineral Resources-1989 Program and Abstracts 47 
fundamental rules for digitizing a geologic map: (1) never 

generalize explicit detail and (2) always include implicit 

detail. 

Features on a geologic map should be encoded for 

explicit retrieval. Although generalization of geologic units 

simplifies immediate digitizing tasks, this practice precludes utilization of any information removed from the 

detailed map. For example , aggregating Paleozoic sediments negates efforts to correlate lithofacies with geochemistry. Subdivision of features prior to digitizing also may be 

necessary; Quaternary and Tertiary units may be coded 

secondarily with the identity of underlying units to facilitate 

removal of the younger units within the GIS. In either case, 

detail may be added later, but retrofitting is far more costly, 

inaccurate, and complicated. 

Coding practices that account for implied attributes 

improve data management and, hence, analytical tasks. 

Implicit detail is usually contained in ordinal attributes such 

as the stratigraphic order of geologic units. For example, for 

the assessment of vein-type mineral deposits, the relative 

ages of plutonic bodies are important in establishing the 

temporal and spatial relations of potential mineralization 

events. Nominal attributes such as rock type can also imply 

order, such as degree of geochemical reactivity. 

Criteria for coding must be developed prior to digitizing to fac ilitate the logical extraction of pertinent data. 

Guidelines for scale , accuracy, and spatial resolution also 

must be established at the onset of a project. Informal 

standards have evolved that permit consistency of attribute 

handling and continuity between projects. However, more 

widely accepted and rigorous standards need to be established to permit the exchange of digital geologic map data 

among different users. 

Multiple Sources for Gold in the Juneau Gold 

Belt, Alaska 

Rainer j . Newberry and David A. Brew 

Vein gold deposits of the Juneau gold belt vary in 

host rock, mineralogy, metamorphic setting, metal ratios, 

and source of the gold. Geological, geochemical, and 

isotopic studies indicate there are at least two major sources 

of the gold: remobilized from preexisting low-grade gold 

deposits and exotic , or introduced. In remobilized deposits 

there are two subsources: remobilized plutonic-hosted 

deposits and remobilized volcanogenic deposits. 

Remobilized plutonic-hosted gold deposits are north 

of Berners Bay (for example, Kensington, Jualin) and on 

eastern Douglas Island (Treadwell group). Major-element 

analyses of the least-altered rocks and trace-element analyses of altered rocks indicate that the host plutonic rocks 

have distinctive alkalic chemistry and range from monzodiorite to monzonite and quartz monzonite. The altered and 

least-altered host rocks and the deposits are probably of 

Late Cretaceous age, and all have experienced Late CretaThe reality of the rain forest in southeastern Alaska. (Note 

the notorious Devil's Clu b plant at left center.) 

ceous, lowest grade greenschist facies metamorphism. Orebodies are massive quartz-ferroan dolomite-pyrite "mainstage" veins and breccias that have moderately wide ( < 100 

m) carbonate alteration envelopes; gold-bearing "pre-mainstage" quartz-K-feldspar-pyrite-magnetite± biotite-chloritechalcopyrite-molybdenite veinlets and veins occur in deeper 

exposures of both systems. The main-stage gold-quartzcarbonate veins are characterized mineralogically by: (1) 

relatively high oxidation and sulfidization state assemblages, such as hematite-rutile-bornite-pyrite; (2) the presence of telluride minerals; (3) high Au:Ag (2: 1-20: 1); (4) 

high Cu and Mo content; and (5) low As, Sb, Pb, and Zn 

abundances. Sulfur isotope ratios vary from + 1.2 to - 3.8 

per mil , compatible with a plutonic-hydrothermal sulfur 

source. Lead isotope ratios are compatible with a Mesozoic, 

subduction-derived lead source. 

Remobilized volcanogenic deposits are represented 

by the Alaska Treasure mine on southeastern Douglas 

Island and the Fremming-Valentine deposits north of Bern48 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
KEWEENAWAN LITHOSTRATIGRAPHY 

1••···············• 1 

111111111111111 

t-' ''"''-l 1.-'/-,/~ 

CLASTIC SEDIMENTS 

VOLCANIC ROCKS 

GABBROIC INTRUSIONS 

"~-.... ..... """' White P•ne mine 

Copper, silver sulfides 

........ 

WISCONSIN 

ONTARIO 

LAKE SUPERIOR 

Tribag 

..., MINERAL OCCURRENCES 

0 50 100 150 KILOMETERS 

Figure 1. Locations of the major known mineral occurrences associated with the Midcontinent rift in the Lake Superior 

region. [Nicholson and others abstract] 

ers Bay . Host rocks are Lower Cretaceous bimodal(?) 

volcanics of the Gravina overlap assemblage that have been 

overprinted by Late Cretaceous lower greenschist facies 

metamorphism. The gold veins are postmetamorphic 

quartz-ferroan dolomite-albite-pyrite-galena veins that have 

very narrow ( < 1 m) alteration envelopes. They occur near 

massive and semi-massive volcanogenic pyritesphalerite-chalcopyrite-galena deposits in quartz-dolomite 

gangue. The veins have gold abundances about three times 

higher than the nearby deposits and are characterized by: (I) 

low Au:Ag (1 :2-1 :20); (2) low Te, Mo, As, and Sb content; 

and (3) high Pb, Zn, and Cu abundances. Vein sulfur 

isotope ratios are similar to massive sulfide ratios: both vary 

from +2 to +4.3 per mil and are similar to ratios for 

Mesozoic volcanogenic massive sulfide deposits. Lead 

isotopic ratios are compatible with a Mesozoic , subductionderived lead source. 

"Exotic" gold deposits are veins and vein swarms for 

which there is no evidence of a preexisting gold concentration in the country rocks. The Alaska-Juneau (A-J) group, 

east of Juneau, is the largest deposit of this type , and the 

Eagle River and Sumdum deposits are smaller. All are 

hosted by metamorphic rocks of late Paleozoic to early 

Mesozoic age and postdate Late Cretaceous-earliest Tertiary metamorphism. The A-J vein swarm is enclosed in a 

2:0.5-km-wide biotite-chlorite-ankerite alteration envelope. 

All of these deposits have (1 ) variably high As, Sb, Bi, W, 

Pb, and Zn; (2) low Mo, Cu, and Te; (3) highly variable 

Au:Ag (10:1 -1 :100); and (4) low oxidation and low sulfidization state mineral assemblages, such as pyrrhotitearsenopyrite. Sulfur isotope ratios for these deposits are 

very light, -12 to - 18 per mil , suggesting a sedimentary 

sulfur source. Lead isotope ratios are very radiogenic, 

indicating lead derivation from a sedimentary source and an 

appreciable residence time. 

Metallogeny of the Midcontinent Rift in the Lake 

Superior Region 

S.W. Nicho lso n, K.j. Sch ulz, and W.F. Cannon 

The tectonic model presented by Cannon and others 

(this volume) for the evolution of the Midcontinent rift 

provides a new geologic framework within which to constrain the settings of known rift-related mineral deposits. 

This study reports the initial results of a long-term program 

to evaluate the mineral resource potential of the Midcontinent rift system and to establish a basis for predictive 

metallogeny . 

The Midcontinent rift in the Lake Superior region 

comprises several segments separated by accommodation 

USGS Research on Mineral Resources-1989 Program and Abstracts 49 
zones or transform faults. The segments consist of asymmetric central grabens that contain up to 20 km of basalt 

overlain by up to 10 km of sediments. The central grabens 

are flanked by shallow basins that contain exposures of up 

to 5 km of the oldest volcanic units of the system and minor 

sediments. The original structural relations within the rift 

segments have been somewhat modified by postrift compression. 

Rift-related rocks are exposed only in the Lake 

Superior region, and, in this area, the rift contains several 

large mineral deposits. Perhaps the best known are the 

world-class native copper (and silver) deposits of the 

Keweenaw Peninsula, Mich., which are restricted to the 

central graben (fig. 1). These deposits occur as stratabound 

deposits within amygdaloidal basalt flow tops and interflow 

conglomerates and within fissures. Although inactive 

today, these deposits yielded nearly 51/z million short tons of 

native copper from about 1845 to 1968. 

Other rift-related deposits appear to be localized 

within the original flanking basins of the rift. Native silver 

deposits and associated base-metal sulfides occur in fissures 

cutting Early Proterozoic black slates in a shallow flanking 

basin in the Thunder Bay area, Ontario (fig. 1), where 

mining from 1869 to 1922 produced more than 21/z million 

troy ounces of silver. Also, stratiform copper sulfides 

(mostly chalcocite) and lesser native copper and silver are 

still actively mined at the White Pine mine, Michigan (fig. 

1), where ore production has yielded nearly 1 million short 

tons of copper. This deposit resides in a lacustrine black 

shale deposited in a restricted basin on the south side of the 

rift. 

Several large mafic intrusions are exposed along the 

margins of some flanking basins; the Duluth complex, 

Minnesota, and the Mellen complex, Wisconsin, are two 

examples. Large subeconomic deposits of copper-nickel 

sulfides are located near the base of the Duluth complex 

(fig. 1); estimates indicate resources of about 4.4 billion 

tons of 0.66-percent copper and 0.17-percent nickel. These 

intrusions are also known to contain titanium and vanadium 

deposits and are being investigated for platinum-group 

minerals. 

In addition, the Tribag breccia pipes of the Batchawana area, Ontario, are located just outside the present 

extent of the rift (fig. 1). These pipes, containing coppermolybdenum mineralization, produced 32.2 million pounds 

of copper from 1967 to 1974 and appear to be related to 

nearby rift-related felsic intrusions. 

Metallogenesis of Lode Mineral Deposits of 

"Mainland" Alaska 

Warren j. Nokleberg, Thomas K. Bundtzen, Donald j. 

Grybeck, and Thomas E. Smith 

For "mainland" Alaska, west of 141 oW. longitude, 

regional metallogenetic patterns are delineated by classification of metalliferous lode mineral deposits, according to 

recently developed mineral deposit models and bedrock 

geologic and tectonic setting. In each region, the origin and 

modification of many of these lode mineral deposits can be 

related to specific sedimentary, magmatic, metamorphic, 

and (or) deformational events. 

Major belts of middle Paleozoic sedimentary exhalative zinc-lead-silver, bedded barite, and kuroko volcanogenic massive sulfide deposits occur in the Brooks Range 

and in the Alaska Range. In the northwestern Brooks Range 

is a belt of Mississippian and Pennsylvanian sedimentary 

exhalative zinc-lead-silver and bedded barite deposits that 

probably formed during late Paleozoic rifting. Belts of 

Devonian and Mississippian kuroko volcanogenic massive 

sulfide and associated Kipushi copper-lead-zinc (carbonatehosted copper) deposits occur in the southern Brooks Range 

and in the eastern Alaska Range and probably formed 

during middle Paleozoic continental margin volcanism. A 

major belt of Devonian and Mississippian graniticmagmatism-related deposits occurs in the southern and 

eastern Brooks Range. These deposits consist of suites of 

polymetallic vein, Sb-Au vein, porphyry Cu and Mo, and 

Cu-Pb-Zn and Sn skarn deposits. 

Major belts of Jurassic, Cretaceous, and early Tertiary granitic-magmatism-related deposits occur throughout 

the State. On the Seward Peninsula is an extensive suite of 

tin vein, skarn, and greisen; polymetallic vein; porphyry 

molybdenum; and felsic plutonic uranium deposits. In 

southwestern and west-central Alaska are suites of Sb-Au 

vein, polymetallic and epithermal vein, porphyry Mo and 

Cu, Cu and Fe skarn, and felsic plutonic U deposits. In 

east-central Alaska are suites of polymetallic vein, Sb-Au 

vein, porphyry Cu-Mo, felsic plutonic U, and Sn greisen 

and vein deposits. On the Aleutian Islands and the southwestern Alaska Peninsula are extensive suites of early 

Tertiary epithermal, polymetallic vein, and porphyry 

copper-molybdenum deposits. Farther northeast in the 

Aleutian-Alaskan Range batholith, the Alaska Range, and 

the Wrangell Mountains are belts of Jurassic, Cretaceous, 

and (or) early Tertiary Cu-Zn-Au-Ag and Fe skarn, polymetallic and Sb-Au vein, Sn greisen and vein, and porphyry 

Cu-Au and Cu-Mo deposits. These granitic-magmatismrelated deposits are related mainly to a succession of 

Jurassic through early Tertiary subductions. 

A suite of moderate-size podiform chromite deposits 

that has local platinum group element occurrences and 

serpentinite-hosted asbestos deposits occurs around the 

margins of the Yukon-Koyukuk basin in west- and eastcentral Alaska. These deposits are hosted in thin discontinuous thrust sheets of late Paleozoic and early Mesozoic 

ophiolites that were probably thrust onto continental margin 

rocks in the Jurassic and (or) Cretaceous. A lesser suite of 

podiform chromite and related· platinum group element 

occurrences in ultramafic rocks is exposed along the Border 

50 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Ranges fault system in southern Alaska. These deposits 

probably formed at the base of an island arc. 

Major belts of gold and copper-silver quartz vein 

deposits occur in low-grade, regionally metamorphosed 

sedimentary and volcanic rocks in several regions and are 

related to metamorphism that accompanied accretion or 

subduction. These metamorphic deposits occur on the 

Seward Peninsula and in the southern Brooks Range in 

Jurassic and (or) Cretaceous rocks; in east-central Alaska, 

the Alaska Range, and the Wrangell Mountains in midCretaceous rocks; and in southern Alaska in early Tertiary 

rocks. Extensive basaltic copper deposits, which, in part, 

may be related to mid-Cretaceous regional metamorphism, 

occur in the Kennecott district in eastern southern Alaska. 

An extensive suite of Besshi and Cyprus massive 

sulfide deposits occurs in the Prince William Sound region 

in coastal southern Alaska. These deposits are related 

mostly to mafic rocks interbedded with Upper Cretaceous 

and lower Tertiary flysch and probably formed during late 

Mesozoic and early Cenozoic sea-floor spreading. 

Rare-Earth Resource Potential: Monazite 

Distribution in the Fall Zone Coastal Plain 

Sediments of Western South Carolina 

James P. Owens and Andrew E. Grosz 

Aeroradiometric (RAD) maps were made for most of 

the Atlantic Coastal Plain through a cooperative between 

the Regional Coastal Plain Commission and the U.S. 

Geological Survey. One of the RAD map areas in western 

South Carolina was geologically mapped (Owens, 1988). 

The geologic map was then overlain on the RAD map to 

look for relations between the anomalies and the mapped 

formations (Owens and others, in press). In general, the 

most intense RAD anomalies were clustered in the Fall 

Zone. The number and intensity of anomalies decreased 

rapidly east of the Fall Zone and were uniformly very low 

near the coast. 

The most intense anomalies in the Fall Zone occurred 

in all the formations ranging in age from Cretaceous to 

Pleistocene. It appears that minerals causing the RAD 

anomalies were deposited in a zone where the higher(?) 

stream gradient of the Piedmont streams changed to the 

lower(?) stream gradient of the Coastal Plain streams. 

The most intense and least intense RAD anomalies 

were checked by using a ground-based gamma-ray spectrometer to precisely define the radioelements (uranium, 

thorium, potassium) responsible for the anomaly. The 

anomalous sediments were then sampled, some to several 

feet below the surface. The samples were analyzed mineralogically to determine the abundance of radioactive mineral species (monazite, zircon) for each anomaly. In all, the 

most intense RAD anomalies were associated with sediments that had significant concentrations of monazite. 

Conversely, th6 lowest anomalies have little or no monazite. 

In general, in spite of the high intensity of some of the 

anomalies, the concentrations of heavy minerals are typically low (less than 1 percent by weight of the samples 

taken). Within these heavy-mineral assemblages, however, 

monazite percentages were as much as 16 percent. Studies 

of the vertical distribution of the heavy minerals within 

thick (> 100 ft) Cretaceous (and younger) sections in the 

vicinity of the Fall Zone may, therefore, lead to the 

definition of potential rare-earth resources such as those 

formerly mined at the Horse Creek deposit near the South 

Carolina-Georgia border. 

REFERENCES 

Owens, J.P., 1988, Geology of Cape Fear Arch area: U.S. 

Geological Survey Miscellaneous Investigations Map 

I-1948-A, scale 1:250,000. 

Owens, J.P., Grosz, A.E., and Fisher, J.C., in press, Aeroradiometric map and geologic interpretation of part of Florence 

and Georgetown 1 o x 1 o quadrangles, South Carolina: U.S. 

Geological Survey Miscellaneous Investigations Map 

I-1948-B, scale 1:250,000. 

Late Cambrian Lithofacies and Their Control on 

the Mississippi Valley-Type Mineralizing System 

in the Ozark Region 

James R. Palmer and Timothy 5. Hayes 

Upper Cambrian sedimentary rocks of the Ozark 

region were deposited by seas that onlapped the southeastsloping Precambrian craton in at least three major 

transgressive-regressive stages. During deposition of the 

Cambrian sediments, local lithofacies varied dramatically, 

controlled, in part, by topography. Geometrically variable 

carbonate platforms first formed around several highland 

areas on the Precambrian erosional surface. The platforms 

then prograded across shallow intrashelf basins where 

interbedded carbonates and shales had been deposited 

earlier. Transgressions superposed shaley basinal facies 

rocks over the ramp and platform facies. Lithofacies variation in the Cambrian rocks determined where subsurface 

solutions would later permeate. 

Basinal and deep ramp shaley carbonate lithofacies 

acted as aquitards to subsurface movement of solutions, 

including dolomitizing and later mineralizing solutions. The 

basinal and deep ramp lithofacies were the only facies that 

remained undolomitized over most of the region. Some 

USGS Research on Mineral Resources-1989 Program and Abstracts 51 
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EXPLANATION 

" Vertically projected boundaries at true scale of large -tonnage (>300,000 T) Pb-Zn or Zn-Pb 

orebodv, or of the outer boundaries of very closely spaced, nearly continuous orebodies 

Small-tonnage, zinc-dominated orebody or occurrence 

Small-tonnage, lead-dominated orebody or occurrence 

• Small-tonnage , barite-dominated orebody or occurrence 

Map of the Ozark reg ion showing locations of Mississippi Valleytype lead, zinc, and barite deposits relative to pinchouts of shale or 

shaley carbonate lithofacies and faults. Note ,the occurrence of 

important ores and well-mineralized districts adjacent to and upsection from shale pinchouts . Geologic features ending or changing at 

political boundaries are probably ending against quadrangles not 

( 

y -- Outline of a district including at least 3 sma ll-tonnage orebodies or occurrences 

where individual symbols would fill the outline at this scale 

Fault, or fold axis extending into a fault, exactly or approximately located; not 

shown where "projected", "inferred", or "possible" on source maps 

Pinchout of shale or of basinal and deep ramp facies shale-limestone section; 

shaded where greater than 5 feet (1.5 m) thick. Includes: 

Mn - Lower Mississippian Northview Fm. 

De - Upper Devonian Chattanooga Shale 

Cd - Upper Cambrian Davis Fm ., basinal and deep ramp facies 

Cb - Upper Cambrian Bonneterre Fm ., basinal and deep ramp facies 

yet studied. Information for this map was compiled from 24 separate source maps including 13 different CUSMAP or Midcontinent 

Strategic and Critical Minerals Program sources, 8 of which are still 

in preparation. A list of source maps is available on request from the 

authors. [Palmer and Hayes abstract] 
dolomitization of the Cambrian rocks took place during 

deep burial as indicated by dolostone distribution and by 

formerly hematitic limestones that were bleached and pyritized to form "whiterock" dolostones (Howe, 1968). Preore sulfidization and dolomitization probably precluded the 

presence of host rock sulfates during later Mississippi 

Valley-type (MVT) mineralization in the Southeast Missouri lead district. The distribution of ore deposits relative 

to windows through shales, including facies windows 

through the Cambrian basinal and deep ramp shaley rocks, 

suggests that MVT ore precipitated where brines driven by 

artesian pressure escaped confinement and migrated upsection. All major districts of the Ozark region occur at the 

margins of and upsection from windows through one or 

more of the shales. Other Ozark region MVT ores are found 

where the aquitards were structurally breached and the 

brines were allowed to climb section. 

MVT sulfide mineralization in the Ozark region is 

associated with a series of fracture- and vug-crusting or 

limestone-replacing , coarse, saddle dolomites having the 

color sequence: (I) tan , (2) white , and (3) pink (fig. 1). 

These paragenetically late dolomite crusts are interlayered 

with ore sulfides at orebodies. The dolomite crusts also 

occur at numerous places across the region (fig. 2), 

interlayered with the trace-metals-anomalous pyrite , marcasite , pyrobitumen blebs, and other organic matter reported 

by Erickson and others (this volume). At many additional 

places regionally, the hydrothermal dolomite crusts occur 

without any accompanying sulfides or organics. Abundance 

of the hydrothermal dolomite crusts is directly proportional 

to the insoluble-residue-metals results of Erickson and 

others (this volume). Very low hydrothermal dolomite 

abundance within and above the shaley aquitards grades to 

anomalous abundance across paleohighs and especially in 

halos around ores. The hydrothermal dolomite crusts allow 

distinction of the regional mineralization stages from all 

other stages of the rock history, before or after. 

Most hydrothermal-stage minerals regionwide are 

within secondary or secondarily enhanced porosity or are 

replacement bodies in nonshaley limestones. Thus, there 

were not just one or two favorable carbonate lithofacies. 

Rather, only the shaley aquitards were unfavorable - all 

other lithofacies were favorable , particularly where they 

were marginal to and upsection from a shale pinchout. 

REFERENCE 

Howe , W.B. , 1968, Planar stromatolite and burrowed carbonate 

mud facies in Cambrian strata of the St. Francois Mountain 

area: Missouri Geological Survey and Water Resources 

Report of Investigations 41 , 113 p. 

Figure 1. Pink-stage saddle dolomites (note curved 

crystal faces) sitting in a vug in jasperoidal sphalerite 

ore, atop drusy quartz, and beneath 1/4-mm chalcopyrite crystals, in a sample from Philadelphia mine, Middle Ordovician Everton Formation host rocks, Northern 

Arkansas district. All these minerals in the same 

sequence a re more familiar in mineralogy collections 

from samples from the Tri-State district, 140 miles to 

the northwest. In fact, though, all these mineral paragenetic relations, two other hydrothermal dolomite 

stages, and numerous other hydrothermal sulfide 

stages are correlatible throughout the Ozark region, 

from basal Cambrian to Early Pennsylvanian host rocks, 

from the Southeast Missouri district to west of the 

Tri-State district, and from the northern edge of the 

Arkoma Basin to central Missouri : more than 25,000 

cubic miles of rock affected by a single hydrothermal 

system. Small-scale divisions are 1 mm. [Palmer and 

Hayes abstract] 

Petrography, Chemistry, Age, and Origin of the 

Rare-Earth Iron Deposit at Bayan Obo, China, 

and Implications of Proterozoic Iron Ores in 

Earth Evolution 

].A. Philpotts, M. Tatsumoto, K. Wang, and P-F. Fan 

The world's largest known rare-earth deposit occurs 

at Bayan Obo (!at 42° N. , long 110° E.), Inner Mongolia, 

USGS Research on Mineral Resources- 1989 Program and Abstracts 53 
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A is from the West Fork mine, Viburnum trend, Southeast Missouri district, from the Cambrian Bonneterre 

Formation, lowest carbonate unit in the Paleozoic 

section. A vug in dolostone wall rock was crustified in 

the sequence: (1) tan-stage hydrothermal dolomite (T) 

coarser than wallrock but finer and darker than whitestage dolomite, (2) octahedral galena (g), (3) 1-mm 

rhombs of white-stage hydrothermal dolomite with (4) 

limpid, pink-stage hydrothermal dolomite overgrowths (W&P), and (5) scalenohedral calcite (cal). 

8 is from the Cambrian Potosi Formation in 

north-central Arkansas, 300 m upsection and 

135 miles southwest of the West Fork sample, 

from an exploration core. It shows a dolostone breccia cementation and crustification 

sequence of (1) recrystallized wallrock selvage with intercrystalline pyrite (dark rims on 

breccia clasts; early tan-stage), (2) tan-stage 

hydrothermal dolomite (T), (3) botryoidal 

sphalerite (sp) and pyrite (py), (4) white-stage 

hydrothermal dolomite (W), (5) botryoidal 

pyrite, and (6) scalenohedral calcite (cal). 

Cis from the Semple mine in Tri-State district's Picher 

Field, from Middle Mississippian Warsaw Formation 

host rocks, another 200 m upsection, and now 220 

miles west-southwest from the first sample. It shows 

a sequence of chert breccia cementation and crustification of (1) tan-stage hydrothermal dolomite (T) 

with intercrystalline dark brown clay and sphalerite 

(the "gray dolomite" of the Tri-State literature), (2) 

white-stage hydrothermal dolomite, and (3) pinkstage hydrothermal dolomite (P). 

Figure 2. Examples showing correlation of hydrothermal dolomite crustification sequences across the Ozark region (Small-scale divisions in each photograph 

are 1 mm. Paragenetic boundaries have been partly highlighted and partly left in natural shades on photographs Band C) . [Palmer and Hayes abstract] 
China, in hematite-magnetite iron ore, carbonate, and 

aegirinite, toward the top of a thick Proterozoic clastic 

sequence that has been folded, faulted, and regionally 

metamorphosed. Monazite and bastnaesite are the major 

rare-earth ore minerals; rare-earth mineralization is commonly disseminated widely within samples. Fluorite and 

niobium minerals are locally abundant. Many textures are 

metamorphic-metasomatic; some textures may be sedimentary. At least some of the rare-earth and iron deposition is 

contemporaneous. Rare-earth abundances are at percent 

levels in the ore samples and show extreme light-rare-earth 

enrichment and, typically, neither cerium nor europium 

anomalies. These rare-earth patterns do not resemble those 

of clastic or chemical sediments and, indeed, are not 

typically crustal but resemble the rare-earth patterns of 

limited partial melts derived from the mantle. Low 87Sr/86Sr 

measured for Bayan Obo carbonates also support mantle 

derivation. Sm-Nd isotopic systematics of the Bayan Obo 

ore samples do not yield a whole-rock isochron; internal 

two-point Nd "isochrons" reveal complexity in rare-earth 

mineralization and suggest both Proterozoic and Paleozoic 

crystallization. The grouping of Nd model ages suggests 

that the rare-earths may have separated from a nearchondritic mantle reservoir at about 1.4 Ga. 

Large iron-oxide deposits (other than the banded iron 

formations) considered to be of mid- to late-Proterozoic age 

include (I) the internally derived billion-ton deposits at 

Olympic Dam, Australia; Kiruna, Sweden; and the Missouri ferroan felsics; and (2) iron- and titanium-rich deposits 

associated with anorthosite-suite rocks. The largest rareearth deposit in the United States, the carbonatite at 

Mountain Pass, Calif., is of mid-Proterozoic age . Bayan 

Obo and these other deposits may share common genetic 

features. At the very least , the deposits appear to reflect 

unusual conditions in the crust and (or) involvement of 

mantle convection or major plume activity during this 

period. The lack of proportionately extensive orogenesis or 

basaltic volcanism may favor plumes. Origin of the internally derived iron ores by hydrothermal processes or by 

igneous processes involving contamination or extreme fractionation, perhaps including liquid immiscibility, appears 

feasible; each process, however, presents difficulties in 

interpretation. Volatiles other than water may have played a 

role in some cases of iron enrichment. 

Chemical Modeling of Ore and Gangue 

Deposition in the Creede, Colorado, Epithermal 

System 

Geoffrey S. Plumlee 

Strongly zoned, mineralogically complex epithermal 

deposits at Creede, Colo. (fig. 1), resulted from the 

interactions of diverse chemical processes in the hydrotherThe Commodore mine, Creede, Colo. , was one of the 

major mines in a district that has produced over $100 

million worth of silver and base metals since its discovery 

in the San Juan volcanic field in 1889. 

mal system. By using data from previous geological and 

geochemical studies (such as, Bethke, 1988), chemical 

modeling calculations help elucidate many of these processes. 

It is inferred (Bethke, 1988) that the Creede hydrothermal system was recharged by two meteoric fluids of 

strongly contrasting chemistries. Chemically and isotopically evolved meteoric waters rich in chlorine, sodium, 

carbonate, sulfate, and soluble organics entered the system 

from Creede caldera moat sediments at the south end of the 

district, and dilute meteoric waters entered the system from 

highlands in the northern district. At depth, fluid chemistries were modified through internal chemical reactions, 

reactions with wallrocks, and possible interactions with 

magmatic fluids. During high-temperature (T) stages 

(T>200 °C), most constituents of the fluids approached 

equilibrium K-feldspar-mica pH values and redoxsulfidation conditions near those defined by the assemblage 

pyrite-chlorite-hematite (PCH). Aqueous sulfate-sulfide 

USGS Research on Mineral Resources-1989 Program and Abstracts 55 
Northern Assemblage - High precious metals: 

calcite, rhodochrosite, rhodonite, quartz, adularia, 

jalpaite, pyrargyrite, electrum, acanthite, sphalerite, 

galena, pyrite, fluorite, kutnahorite, southern barite 

Colorado 

I 

OH Assemblage - High base metals: 

sphalerite, galena, chlorite, pyrite, hematite, 

chalcopyrite, tetrahedrite, quartz, adularia, 

fluorite, manganese-siderite, marcasite 

~ 

• 

Disseminated 

mineralization 

Quartz latite 

CREEDE CALDERA 

Resurgent Dome 

Bulldog Assemblage- High silver: 

barite, sphalerite, galena, native silver, acanthite, 

quartz, rhodochrosite, fluorite, sulfosalts, pyrite, 

marcasite 

intrusive 

1::::::::: <I Quartz latite 

flow 

I, •·,,, i I Creede 

Formation 

CJ Volcanic tuffs, 

flows 

Fault - stippled where 

known to be 

mineralized 

0 2km 

Figure 1. Creede, Colo., district geology and mineral zoning. Northern assemblage unpublished data from N. Foley and 

S. Caddey. Southern and Bulldog assemblages from references in Bethke (1988). [Plumlee abstract] 

and hydrocarbon-fluid reactions did not equilibrate, even at 

temperatures up to 300 °C. The southern-recharge brines 

(salinities up to 13 weight percent NaCl equivalent) picked 

up and transported from depth large quantities of chloridecomplexed metals (zinc, lead, copper, silver); the dilute 

northern-recharge fluids carried much smaller quantities of 

chloride-complexed metals but greater quantities of 

bisulfide-complexed metals (gold, arsenic , antimony). The 

southern-recharge fluids produced base-metal- and silverrich mineralization during most stages along the central and 

southern vein systems and during at least one stage in the 

northern vein systems. The dilute northern-recharge fluids 

produced precious-metal-rich stages along the northern vein 

systems. Mixing of the two fluids across the system's 

~A banded sphalerite that has a quartz-adularia core, OH 

vein, Creede, Colo. The variations in color are due 

mainl y to differences in the amount of iron . 

56 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
upwelling plume promoted metal deposition due to changes 

in salinity, pH, and temperature. 

Shallow boiling and mixing in the system's ore zones 

further modified fluid chemistries. Due to a north-to-south 

topographic gradient across the district, the hydrothermal 

fluids flowed predominantly from north to south through the 

central and southern district ore zones. Chemical reaction 

path modeling suggests that, in the hotter, deeper portions 

of ore zones in the central vein systems (OH vein, P vein, 

central Amethyst, and Bulldog Mountain; fig. 1), hydrothermal brines boiled over a restricted-temperature interval 

(D..T 5-10 °C) to deposit chlorite-hematite-quartz-base-metal 

sulfide ores. Due to the high salinities and initially high 

oxidation conditions of the hydrothermal brines (near the 

PCH buffer), more extensive boiling over a greater temperature drop (D..T 10-40 °C) would cause the brines to become 

undersaturated with sulfides and would produce a simple 

quartz-adularia-hematite-fluorite assemblage; a middle 

gangue stage along the central and southern vein systems 

that has this mineralogy probably formed in this manner. 

Lateral mixing to the south with cooler, dilute, oxidizing 

ground waters caused boiling to cease in the hydrothermal fluids. Calculations show that initial mixing could have 

produced base-metal sulfide-rich ores observed along the 

central district vein systems. With increased mixing, the 

base-metal ores would become more silver rich and have 

increasing proportions of barite, acanthite, native silver, 

and various copper sulfides; such mineralogies are observed 

along the district's southern vein systems (southern Amethyst and Bulldog Mountains). Extreme barite-rich mineralization in the district's southernmost vein systems may 

have formed through mixing of the brines with sulfate-rich 

pore fluids from Creede caldera moat sediments. In the 

district's northern vein systems, calculations indicate that 

boiling of the dilute northern-recharge fluids likely triggered deposition of carbonate-adularia-quartz-preciousmetal assemblages that have high gold to base-metal 

ratios. 

REFERENCE 

Bethke, P.M., 1988, The Creede, Colorado, ore-forming system: 

A summary model: U.S. Geological Survey Open-File 

Report 88-403, 29 p. 

Airborne Imaging Spectrometer Data as an Aid 

to Mineral Mapping, Cuprite, Nevada 

M.H. Podwysocki and 0.0. Jones 

Within the last several years, new airborne multispectral scanners that measure spectral radiance in numerous (as 

many as 224) discrete wavelength channels have become 

available. Because their spectral sampling intervals 

approach those of laboratory spectrometers, the new instruments are called airborne imaging spectrometers (AIS). AIS 

data can be used to identify diagnostic absorption bands 

associated with hydroxyl-, carbonate-, and ammoniumbearing minerals, some of which may be indicators of 

potential economic mineral deposits. In the present study, 

AIS data for the Cuprite mining district in western Nevada 

are examined to analyze data calibration procedures and to 

determine the utility of these data for distinguishing several 

types of hydrothermally altered rocks. 

Figure 1 shows 3 of the 32 channels of data from the 

GER, Inc., AIS (GERAIS), which cover a range of approximately 2.0 to 2.5 ~J.m. For comparison, the Landsat 

Thematic Mapper digital scanner has only one channel in 

this important spectral region. Spectral response curves, 

which can be related to mineral composition, can be 

determined by choosing selected ground sites within a 

GERAIS image and extracting digital number values for 

each of the 32 channels. 

Figure 2 shows spectral response curves extracted 

from the Cuprite, Nev., study area for three different 

materials. These curves closely match laboratory spectra for 

alunite, kaolinite, and buddingtonite. 

Stratabound Copper and Zinc Mineralization in 

Triassic Lacustrine Beds of the Culpeper Basin, 

Virginia 

Gilpin R. Robinson, Jr., and Joseph P. Smoot 

Anomalous concentrations of stratabound zinc, copper, and other metal sulfides occur in dark-gray to black 

lacustrine mudstones of the early Mesozoic Newark Supergroup in the Culpeper, Gettysburg, and Newark rift-basins 

of the Eastern United States. In the Culpeper Stone Company Quarry, Stevensburg, Va., a cyclic sequence of 

lacustrine beds contains four black, calcareous, silty mudstone layers enriched in base and precious metals. In fresh 

samples, mineralized mudstones have 1,000 to 7,000 ppm 

Zn, 200 to 28,000 ppm Cu, 5 to 40 ppm Ag, and as much 

as 200 ppm Mo, 1,000 ppm Pb, 17,000 ppm Mn, and 0.5 

ppm Au. Two black mudstone intervals, each containing 

two metal-rich zones ranging from 10 em to nearly 2 m 

thick, are traceable along strike 3.5 km north of the quarry 

and 3 km to the south. The cyclic lacustrine sequence 

appears to represent the repeated transgressions and regressions of a sediment-starved, closed-basin lake during prolonged periods of dessication. 

The mineralized beds consist of gray to black sandy 

mudstone or muddy siltstone that have abundant carbonateand sediment-filled tubes (root structures), some deep, 

narrow, sinuous silt-filled mudcracks, and local carbonate 

nodules. This lithology is interpreted as a vegetated, 

shallow-water shoreline to mudflat that was subaerially 

exposed at intermittent intervals. Within cement-filled root 

USGS Research on Mineral Resources-1989 Program and Abstracts 57 
Figure 2. Relative spectral response curves derived from 

the GERAIS data for Cuprite, Nev. Spectral response in 

digital numbers is plotted along the ordinate, and spectral 

wavelength is plotted along the abscissa. Note that the 

minimum reflectance of alunite (A) occurs at approximately 2.16 J-Lm, which corresponds to channel 43 of the 

spectrometer, whereas the minimum reflectance of 

kaolinite (K) occurs at approximately 2.20 J-Lm, which 

corresponds to channel 45. The minimum for buddingtonite (B) occurs at 2.12 J-Lm in channel 40. [Podwysocki and 

Jones abstract] 

tubes and silt-filled mudcracks are small disseminated 

aggregates of intergrown sphalerite, chalcopyrite, and bornite that have minor galena and pyrite and isolated patches 

of arsenopyrite, pyrite , and pyrrhotite. The sulfides partially replace diagenetic pyrite and carbonate cements that 

apparently grew around the roots during their decay. Chalcopyrite, pyrite , and minor sphalerite replace wallrock 

adjacent to thin , near-vertical , calcite-filled fractures and 

veins. These sulfides are preferentially developed where the 

veins and fractures cut the mineralized sandy mudstone 

beds. Chalcopyrite replaced coarse carbonate cements in 

silt-filled mudcrack and root tubes, apparently by reactions 

with vein fluids, within a few inches of sulfide-bearing 

veins. 

The stratabound mineralization appears to be controlled by the immediate superposition of organic-matter-

<Ill Figure 1. A set of images depicting 3 of the 32 GERAIS 

channels that cover the 2.0- to 2.5-J-Lm spectral range 

for the Cuprite, Nev., study area. The images are 

approximately 9.8 km wide by 11.0 km long. Spatial 

resolution is approximately 20m. North is at the top of 

the images. Note the three small, dark areas (B) in 

channel 40 at 2.12 J-Lm (fig. 1A), which is the spectral 

response minimum for buddingtonite. Alunitic areas 

(A) appear darkest in channel 43 (2.16 J-Lm) (fig. 1B), 

whereas a kaolinitic area (K) appears darkest in channel 45 (2.20 J-Lm) (fig. 1C). [Podwysocki and jones 

abstract] 

58 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
rich laminated lacustrine shales of deep-water origin over 

sandy , root-disrupted, and mudcracked siltstone. This suggests that depositional porosity and preservation of reactive 

organic material were important controls on base-metal 

mineralization. Reducing conditions cannot be the only 

control on the localization of sulfide mineralization, however, because associated organic-matter-rich, deep-water 

shales are unmineralized. The metal-bearing fluids may 

have been introduced along fractures long after lithification, 

with sulfide precipitation occurring by reaction with and 

dissolution of carbonate cements. Faults may have acted as 

fluid conduits to the more permeable and reactive layers. 

The metal-rich samples in the early Mesozoic basins 

resemble unmineralized black mudstones in outcrop, and 

weathering tends to greatly reduce copper and contents, so 

that extensive deposits containing this type of mineralization may go unrecognized if not carefully sampled. 

Although the known stratabound base-metal occurrences in 

the Newark Supergroup are currently subeconomic, their 

tectonic and depositional sedimentary environment is similar to important copper, lead, and zinc deposits such as 

those at Mount Isa and McArthur River, Australia. By 

analogy, the black lacustrine mudstones of the Newark 

Supergroup may be potential hosts for extensive and economically significant base-metal sulfide deposits, particularly in areas where bulk mining techniques are feasible and 

waste rock can be marketed as construction aggregate. 

Volcanism, Extensional Tectonics, and Epithermal Mineralization in the Northern 

Basin and Range Province, California, Nevada, 

Oregon, and Idaho 

james j. Rytuba 

The northern part of the Basin and Range province, 

extending from northwestern Nevada and northeastern California into eastern Oregon and western Idaho, is composed 

primarily of regionally extensive volcanic fields related to 

extensional tectonism of middle Miocene age. An important 

feature of this part of the province is the absence of 

Precambrian continental crust, as defined by the Sr87/Sr86 of 

0.706 (fig. 1), and the lack of exposed Paleozoic and 

Mesozoic rocks. In northwestern Nevada, the boundary of 

Si li ceous sinter from the Gold Hill mine , located 4.6 mi north of Round Mountain, Nev. , on the western slope of the 

central Toquima Range. 

USGS Research on Mineral Resources- 1989 Program and Abstracts 59 
the province is marked by two large fault zones, the 

northeast-trending Black Rock Structural Boundary (BRSB) 

and the northwest-trending Orevada rift (OR) (fig. 1). 

Paleozoic and Mesozoic rocks are displaced downward 

more than 1 km along these fault zones, and fundamental 

changes in regional gravity and magnetics occur across 

these structures. 

The most voluminous and widespread volcanic event 

in the province was the eruption of Steens-type tholeiitic 

basalt at about 16 Ma. The basalts form a large shield 

volcano whose central vent, defined by a circular magnetic 

anomaly, is located near the crest of Steens Mountain , 

Oreg . Following the Steens event, widespread and voluminous eruption of peralkaline ash-flow tuffs occurred from 

16 to 15 Ma . The peralkaline volcanic centers were 

emplaced along the BRSB and the OR and extend from 

northwestern Nevada into eastern Oregon. Fifteen calderas 

related to this event have been identified (fig. I). The 

peralkaline ash-flow tuffs are often chemically zoned and 

become metaluminous in their upper parts. Postcollapse 

domes and intrusions range from peralkaline to metaluminous. 

120° 118° 

Ore metals concentrated in the peralkaline rhyolites 

include (maximum value in ppm) Ag (0.4), As (6.4), Cs 

(112), Hg (0.96), Li (213), Sb (2.2), Tl (2.5), Th (23), U 

(12), and Zn (600). The rhyolites are depleted in Au , Co, 

Cu, Cr, Pb, Ba, and Sr. Widespread epithermal uranium, 

mercury, and precious-metal-bearing systems developed 

during the waning stage of the peralkaline volcanic event 

and were localized along caldera ring faults and northwesttrending zones of extensional faulting along which rhyolite 

domes and plugs were emplaced. The DeLamar and Milestone gold-silver deposits are localized along the DeLamarDuck Valley extensional fault zone. This narrow zone of 

faulting extends 180 km from the southwestern IdahoNevada border to eastern Oregon. The deposits are closely 

related to rhyolite vent and dome complexes localized along 

this zone of extensional faulting. At the same time in 

Nevada, a similarly narrow zone of extensional faulting and 

associated rhyolite vent complexes developed and localized 

the Buckskin mercury-gold-silver deposits and the National 

gold-silver veins. These zones of extensional faulting and 

hydrothermal activity were less than 1 million years in 

duration and developed above near-surface rhyolite magma 

116 ° 114° 

0 1 00 KILOMETERS 

• Caldera, dotted where inferred 

from gravity data 

W Whitehorse 15 Ma 

P Pueblo 15.8 Ma 

M Mahogany Mtn . 15.5 Ma 

T Three Fingers 15.4 Ma 

H Hog Ranch 15.4 Ma 

McD McDermitt complex 16.1·15.6 Ma 

Central vent of shield volcano 

(S teens Mountain) 

~ Mesozoic and Paleozoic rocks 

Figure 1, Volcanic and tectonic features in the northern Basin and Range province. [Rytuba abstract] 

60 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Copperstone gold mine, La Paz County, Ariz . The photograph faces south toward the main ranges of the Dome 

Rock Mountains, which are on the skyline. The low 

foothills in the upper right-hand part of the photograph 

are called the Moon Mountains by some but referred to as 

the Dome Rock Mountains at the mine. A large detachment fault that strikes northwest-southeast daylights in 

these footh ills and dips to the northeast (for example, 

toward the lower left corner of the photograph) under the 

bodies. Hydrothermal systems commonly developed where 

these magmas vented as domes or tuff cones. Other epithermal deposits, formed at this time and localized along or 

adjacent to caldera structures, include the McDermitt and 

Cordero mercury deposits, Hog Ranch gold deposit, and 

numerous undeveloped prospects such as at Red Butte and 

Grassy Mountain, Oreg. The level of erosion in these 

volcanic and epithermal systems is slight, and so only the 

uppermost parts of the hydrothermal systems are exposed. 

Hot-spring sinter and hydrothermal explosion craters, such 

as at Red Butte, are well preserved. 

After the peralkaline volcanic event, the locus of 

volcanism moved northwest through the province with the 

emplacement of small volume domes and lavas until 10 Ma 

when major peralkaline ash-flow tuffs were erupted from 

the Harney basin caldera complex. The locus of dome 

emplacement continued to move to the northwest; most 

orebody. The ore at the mine is in the Copperstone fault 

that dips to the northeast at about 30° and is exposed in 

the pit. The pit parallels the strike of this fault. The dark 

dump between the pit and the office-plant complex is ore. 

The access road to the property can be seen at the upper 

left edge of the photograph. (Caption courtesy of Hugo 

Dummett, Arizona Geological Society. Photograph courtesy of Cyprus Minerals Company, Denver, Colo. Photographer is Mickey Prim, Manley-Prim Photography, Inc.) 

recent actiVIty was near Newberry caldera. Epithermal 

systems, such as the Quartz Mountain gold and mercury 

deposits, are closely associated with rhyolite domes 

emplaced along northwest-trending zones of extensional 

faulting. Basin-and-range-type extension responsible for 

much of the present topography began at about 8 Ma, just 

after the last voluminous ash-flow eruptions from Harney 

basin . The basins are relatively shallow and consist of 

numerous horst and graben structures. Active geothermal 

systems are localized along basin margins and horsts within 

the basins. Northwest-trending zones of extension, such as 

the Brothers fault zone and the Honey Lakes zone, cut 

across the northeast basin-and-range trend and developed 

concurrently with extension. The youngest tectonic feature 

in the province is a large east-west-trending graben (150 km 

strike length) associated with Holocene basaltic volcanism. 

USGS Research on Mineral Resources-1989 Program and Abstracts 61 
Reconstruction of Primary Features and Isotopic 

Evidence for Multiple Sulfur Sources at the Red 

Dog Zinc-lead-Silver Deposit, Noatak District, 

Alaska 

Jeanine M. Schmidt and Robert A. Zierenberg 

The giant Red Dog sediment-hosted sulfide deposit 

(77 million metric tonne, 17.1 percent zinc, 5.0 percent 

lead, 82.0 g/metric tonne silver) consists of at least three, 

and probably five thrust panels of ore, each folded during 

and after thrusting. The three most important panels are the 

Hilltop deposit and the upper and lower ore plates of the 

Main deposit. Core logging (at 1:120, on 60-m spacings) in 

the Main deposit has enabled a partial reconstruction of the 

orebody prior to its deformation in the Cretaceous Brooks 

Range fold- and thrust-belt orogeny. The first thrust 

emplaced the entire deposit, Mississippian footwall, and 

Permian to Cretaceous hanging-wall rocks over Cretaceous 

sedimentary rocks. There was a minimum of 2 km displacement, but more likely tens of kilometers displacement. A 

second thrust, having <500 m northeasterly displacement, 

stacked the upper ore plate over the lower. A 200 by <300 

m area in the upper plate having apparently upside-down 

zonation (silicified barite to mineralized barite to barren 

barite to baritic shale downward) may be the overturned 

limb of a drag fold associated with this second thrust. The 

two ore plates of the Main deposit and their bounding 

thrusts were then broadly folded beneath the third thrust, 

which emplaced footwall rocks and the Hilltop part of the 

deposit above the upper ore plate. 

Massive (70-100 percent) and semi-massive (30-70 

percent) sulfides and lower grade (0-30 percent) siliceous 

ores are texturally heterogenous and interfinger on scales of 

<40 m vertically and <300 m laterally. Unlike most 

shale-hosted deposits, pyritic massive sulfide ores are 

uncommon and small (<10X<IOO m). Vein and disseminated sulfides occur in footwall rocks wherever they are 

preserved below the Main deposit. Silicification of both 

shale and massive barite is common, and silicification 

fronts between ore and host shales are locally steep. 

Burrows of vent-specific infauna, probably worms, increase 

in frequency upward in the upper ore plate and to the 

northwest in the deposit, but discrete vent sites have not yet 

been identified. Clastic ores of fine sand to conglomerate 

are rare, spatially restricted, but locally thick ( 40 m); their 

Diamond drill in the Noatak camp near the Red Dog deposit, Alaska Brooks Range.[Schmidt and Zierenberg abstract] 

62 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Worm tubes and pellitoids in massive barite from the Red 

Dog zinc-lead-silver shale-hosted massive su lfide deposit. 

These Mississippian-age trace fossils are evidence for 

some of the oldest known hydrothermal vent specific 

fauna. [Schmidt and Zierenberg abstract] 

distribution indicates local sea floor relief during ore deposition. Mineralization at Red Dog occurred prior to lithification of Carboniferous siliceous black shale host rocks, 

but Red Dog differs from standard models of sedimentary 

exhalative deposits in that much of the mineralization 

occurred below the seawater-sediment interface. Diagenetic 

growth of minerals in unlithified sediment and progressive 

replacement of sediment and previously deposited ore 

minerals are well documented in the Main deposit. 

Massive barite locally formed an upper cap to the 

deposit and was partially replaced from below by hydrothermal sphalerite, galena, and silica. Although Red Dog is 

hosted by black, organic carbon-rich rocks indicative of 

anoxic conditions of deposition , the sulfur source for the 

massive barite has o34S values of 16 to 19 per mil , near 

those of normal mid-Carboniferous seawater sulfate. Disseminated, diagenetic barite precipitated in unlithified shale 

at the margins of the Red Dog deposit has o34S values up to 

50 per mil; these values suggest formation from residual 

pore water sulfate modified by open-system sulfate reduction. In contrast, other zinc-lead massive sulfide deposits of 

similar age in the district lack barite and have o34S values 

indicative of total reduction of seawater sulfate to sulfide. 

Sphalerite and galena in the Red Dog Main deposit 

generally have o34S values of -5 to 5 per mil. Sphalerite 

that replaces massive barite is isotopically similar to both 

massive sulfide and sphalerite in footwall veins and reflects 

a uniform o34S value of the hydrothermal fluid. Therefore, 

replacement of barite proceeded by dissolution and reprecipitation and did not involve direct reduction of barite 

sulfate to sulfide. The reduced (hydrothermal) sulfur probably formed by water-rock interaction in clastic rocks below 

the mineralized horizon and was transported to the site of 

sulfide deposition by the metal-bearing ore fluid. Pyrite is a 

minor component of the massive ore and formed from 

isotopically distinct fluids before the majority of zinc-lead 

mineralization. Paragenetically early disseminated and nodular diagenetic pyrite in the distal portions of the deposit 

formed by biogenic reduction of pore-water sulfate having 

o34S values as low as -40 per mil , but this source of 

reduced sulfur was not quantitatively important in the 

formation of the ore deposit. Pyrite enriched in o34S (8-18 

per mil) occurs in massive ore, in pyritic silicified shale, 

and in paragenetically late pyrite veins and probably formed 

by partial reduction of seawater sulfate. 

Geochemistry of Igneous Rocks of the Penokean 

Orogen: Implications for Metallogeny and 

Tectonic Setting 

K.j . Schulz and P.K. Sims 

The Penokean orogen, a major Early Proterozoic 

tectonic belt along the southern margin of the Archean 

Superior craton , consists of a northern epicratonic sedimentary and lesser volcanic assemblage overlying an Archean 

basement and a southern volcanic-plutonic assemblage, 

termed the Wisconsin magmatic terrane. These two portions 

of the Penokean orogen are separated by the east-westtrending Niagara fault zone. Recent geochemical studies of 

igneous rocks in the Penokean orogen provide important 

new constraints on the geologic and tectonic evolution of 

the orogen and help establish a basis for predictive metallogeny . 

The volcanic rocks of the northern epicratonic assemblage consist of a bimodal tholeiitic basalt and lesser 

rhyolite suite having chemical characteristics (major and 

trace elements including rare-earth elements) typical of 

within-plate, rift-related magma types. The compositional 

characteristics of the volcanic rocks, coupled with results 

from recent studies of the sedimentary rocks, support a 

rifted continental margin history for the northern portion of 

the Penokean orogen. This interpretation of the tectonic 

setting provides a new framework for modeling the depositional environment of the region's Superior-type iron 

formations and the occurrence of local carbonate-hosted 

copper deposits. 

The Wisconsin magmatic terrane consists of widespread island-arc tholeiitic and calc-alkaline sequences 

ranging in age from 1860 to 1880 Ma and an aerially more 

restricted calc-alkaline suite that formed between about 

1835 and 1845 Ma. Ophiolitic ultramafic and basaltic rocks 

are found along the Niagara fault zone that forms the 

boundary (suture zone) between the northern and southern 

portions of the Penokean orogen. Synvolcanic intrusions 

USGS Research on Mineral Resources-1989 Program and Abstracts 63 
within the terrane are dominantly calcic to calc-alkaline. 

Present data indicate that the Wisconsin magmatic terrane is 

a composite island-arc system that collided with the continental margin of the Superior province circa 1860 Ma. 

Base-metal sulfide deposits appear to be restricted to 

bimodal, calc-alkaline volcanic units that are compositionally distinct from other volcanic units within the terrane. 

These compositionally distinctive, massive sulfide-hosting 

volcanic rocks may have formed in a within-arc rift. Their 

distinctive composition enhances the use of lithogeochemistry in massive sulfide exploration within the Wisconsin 

magmatic terrane. 

Late-orogenic, postorogenic, and younger anorogenic 

(1760 Ma and 1470-1500 Ma) intrusions and lesser volcanic rocks are locally abundant within the orogen, particularly in the southern portion of the Wisconsin magmatic 

terrane, and range from alkali-calcic to alkalic in character. 

Minor molybdenum mineralization is associated with some 

intrusions while other intrusions have anomalous Sn, Ta, 

Nb, U, and Th. In particular, a recently discovered 1733-

Ma alkali-feldspar granite in the northern portion of the 

Southern Complex south of Humboldt, Mich., is compositionally similar to rare-metal-rich granites of Nigeria and 

the Arabian Shield and suggests a possible potential for 

tin-tungsten (tantalum-niobium) mineralization in upper 

Michigan. 

Manganese Potential of the Cretaceous Rocks 

Flanking the Sioux Ridge, Minnesota and South 

Dakota 

Dale R. Setterholm and Richard H. Hammond 

Cretaceous strata in southwestern Minnesota and 

eastern South Dakota have lithologic, geochemical, and 

depositional attributes similar to attributes of strata that host 

economic deposits of manganese at several localities around 

the world. Investigations are underway to determine if the 

conditions described in several depositional models 

(Cannon and Force, 1983; Frakes and Bolton, 1984; Force 

and Cannon, 1988), which have been proposed to explain 

these ores, existed inMinnesota and South Dakota, and if 

so, whether any anomalous manganese concentrations are 

present. 

The models propose that a dilute ore-forming solution 

can develop in anoxic portions of stratified seas where iron 

is removed as pyrite and where manganese concentrates to 

values up to 500 times those common in normal seawater. 

If this manganese-rich solution is transported to an oxygenated environment, such as along the margins of a depositional basin, the dissolved manganese precipitates as either 

an oxide or a carbonate mineral species. Physical processes 

nearshore may concentrate the manganese-rich material to 

yet higher grades. 

In southwestern Minnesota and in adjoining parts of 

South Dakota, Upper Cretaceous strata were deposited 

along the eastern edge of the Western Interior Seaway on a 

gently sloping surface flanked by the Sioux Ridge. The 

Sioux Ridge is a quartzite highland that, at times, formed 

either a peninsula or a group of islands. Rocks of the Dakota 

Formation, Graneros Shale, Greenhorn Limestone, Carlile 

Shale, Niobrara Formation, and Pierre Shale define a shelf 

facies that passes into nearshore facies, such as the Split 

Rock Creek Formation along the Sioux Ridge paleocoast, 

and a regionally consistent lithostratigraphic succession of 

shallow marine and coastal sediments in Minnesota. 

Although decidedly more clastic, the Minnesota rocks 

correlate well with parts of the established Upper Cretaceous shelf sequence in South Dakota. 

Two key components of the manganese depositional 

models have been observed in the study area. First, high 

manganese-low iron anomalies, although subeconomic, 

have been observed at several places in rocks deposited on 

an open shelf environment. These anomalies demonstrate 

that ore-producing solutions may have been present periodically in the seaway and that at times, the solutions flowed 

onto the eastern shelf. Second, strata reflecting cyclic 

oxic-anoxic conditions have been observed in both the 

nearshore facies and the shelf facies. The presence of these 

strata implies that anoxic flowpaths existed between anoxic 

parts of the basin, where manganese-rich solutions may 

have formed, and nearshore sites where oxic conditions 

favorable for ore formation existed. 

REFERENCES 

Cannon, W.F., and Force, E.R., 1983, Potential for high-grade 

shallow-marine manganese deposits in North America, in 

Shanks, W.C., III, ed., Unconventional mineral deposits 

(Cameron volume): American Institute of Mining, Metallurgical, and Petroleum Engineers, p. 175-189. 

Force, E.R., and Cannon, W.F., 1988, Depositional model for 

shallow-marine manganese deposits around black shale 

basins: Economic Geology, v. 83, no. 1, p. 93-117. 

Frakes, L.A., and Bolton, B.R., 1984, Origin of manganese 

giants: Sea-level changes and anoxic-oxic history: Geology, v. 12, no. 2, p. 83-86. 

Volcanogenic Massive Sulfide Deposits in 

Pre-Tertiary Island Arc and Ocean Basin 

Environments in Nevada 

Maureen G. Sherlock 

Volcanogenic massive sulfides are mineral deposit 

types that are inferred to be associated with the development 

of ancient volcanic arcs or with rift systems in a mostly 

submarine environment and that formed at or near the site of 

64 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
active volcanic and hydrothermal activity. The general type 

of massive sulfide deposit is described as a stratabound 

(stratiform), lenticular accumulation of massive pyrite that 

has copper-, zinc-, and lead-bearing sulfide ore minerals; 

sulfide content characteristically amounts to greater than 60 

percent, and chalcopyrite, sphalerite, and galena are the 

primary ore minerals. 

Nevada contains many rock types that host volcanogenic massive sulfide deposits, and a map and correlation 

chart have been constructed to delineate lithologies permissive for the occurrence of these deposits. Descriptions of 

mineral-deposit occurrences in Nevada have been examined, and those meeting the definitions of massive sulfide 

deposits are shown on the map. The permissive massive 

sulfide-bearing units are grouped into the lithotectonic 

terranes as defined by Silberling and others (1987). Rock 

types that have an inferred depositional environment known 

to host the three main types of massive sulfide deposits are 

common throughout most of northern and western Nevada, 

relatively well exposed, and locally well studied in Nevada. 

Several prospects and a few scattered occurrences of mineralization suggestive of stringer mineralization commonly 

underlying massive sulfide deposits occur. Only two volcanogenic massive sulfide type deposits have been mined in 

Nevada. 

The Rio Tinto and the Big Mike massive sulfide 

deposits occur in Paleozoic terranes, characterized by lithologies that are thought to originate as back-arc-basin or 

oceanic-basin accumulations. Small prospects in western 

Nevada interpreted to be volcanogenic massive sulfide 

deposits are in terranes that contain pre-Tertiary, predominantly Mesozoic, volcanic island-arc rocks. The Rio Tinto 

deposit (9.7 percent copper, 0.0057 oz/t gold) is classified 

as a Besshi-type massive sulfide deposit. The Big Mike 

deposit (10.5 percent copper) is classified as a Cyprus-type 

massive sulfide deposit. Small prospects (generally a few 

percent copper and ranging widely in gold grade) in the 

western terranes are classified as kuroko-type massive 

sulfide deposits. Other massive sulfide deposits may not be 

recognized as such because of the overprint of intense 

hydrothermal mineralization of Tertiary age. 

REFERENCE 

Silberling, N.J., Jones, D.L.. Blake, M.C., Jr., and Howell, 

D. G., 1987, Lithotectonic terrane map of the western 

conterminous United States: U.S. Geological Survey Miscellaneous Field Studies Map MF-1874-C, scale 

1:250,000. 

Characteristics and Geochemistry of Gold 

Deposits in Northern Sonora, Mexico 

Miles L. Silberman and David A. Giles 

Northern Sonora. Mexico, typical of the southern 

Basin and Range physiographic province, is characterized 

by elongate, northwest-trending ranges separated by wide 

alluviated valleys. Basement rocks, consisting ef Precambrian gneisses, metamorphosed andesites, and granites, are 

overlain by younger Proterozoic quartzites and limestones, 

Paleozoic carbonate rocks, and Mesozoic volcanic, clastic, 

and carbonate sedimentary rocks. Pre-Laramide Mesozoic 

plutonic and volcanic rocks and post-Laramide Tertiary 

extrusive and intrusive rocks, related to volcanic activity of 

the Sierra Madre Occidental, are widely distributed. Broad 

areas are underlain by plutonic and associated volcanic 

rocks of the Sonora-Sinaloa batholith of Cretaceous to early 

Tertiary (Laramide) age. 

Four main types of lode-gold deposits have been 

recognized in northern Sonora during reconnaissance field 

investigations (Silberman and others, 1987). Additional 

detailed field investigations will most likely refine this 

classification. 

( 1) Epithermal quartz veins and hydrothermal breccias. -

Hosted in volcanic rocks, the veins can have strike 

lengths of several hundred meters. The breccias are 

related to volcanic domes, some of which are alkalic 

in composition. The deposits are characterized by 

elevated contents of Ag and As, moderate Sb, and Cu, 

Pb, Zn, and Mo. Examples are Tajitos (veins) and 

Cerro Colorado and Magallanes (breccias related to 

domes). 

(2) Discontinuous bull quartz veins.-Thin (centimeter to 

m wide), discontinuous veins of strike length generally less than several tens of meters occur in volcanic, 

carbonate, and clastic sedimentary and metamorphic 

host rocks. They have, in addition to gold, low to 

moderate silver contents (silver-gold ratio= 1-70), 

variable but generally low arsenic ( <30 ppm), and 

variable but generally low to moderate base metals 

(copper, lead, and zinc <300 ppm). Examples are the 

area east of Altar, north of Highway 2, and parts of 

Banco de Oro. 

(3) Low-angle structurally controlled gold. -Gold mineralization occurs along or is spatially associated with 

low-angle shears and faults related to thrusting or 

detachment faulting. Gold occurs in breccias, in 

quartz veins, and in quartz vein stockworks along 

low-angle structures and high-angle splays, or in the 

hanging-wall or footwall of the structures. Host rocks 

include Precambrian gneisses and granites, Paleozoic 

and Mesozoic clastic sedimentary and volcanic rocks, 

Mesozoic granitic rocks, and Tertiary volcanic rocks. 

The structurally controlled category includes 

several deposit varieties. Distinctions can be made on 

the basis of the types of host lithologies involved, the 

physical nature of the low-angle structures, and the 

spatial relations of gold mineralization and its characteristics to the low-angle structures. 

The geochemistry of these prospects is quite 

variable. Gold is usually associated with elevated 

USGS Research on Mineral Resources-1989 Program and Abstracts 65 
contents of Ag, Pb, Zn, Cu, and, frequently, Ba and 

Mn. In general, lead content is greater than zinc or 

copper, but copper-dominated examples occur. Many 

of the prospects have elevated arsenic (> 100 ppm). 

Antimony is more variable but still can be elevated 

(>20 ppm). Boron is strongly anomalous in a few 

prospects. Gold is most frequently associated with 

high lead and arsenic. Examples are Quitovac, La 

Cienega, Lluvia de Oro, San Francisco mine at Llano, 

La Choya, part of Banco de Oro, Las Laminas, and La 

Herradura. 

(4) Carbonate sedimentary-hosted disseminated gold.-

This "Carlin-type" gold mineralization is in carbonaceous, silty, carbonate rocks and associated jasperoids and breccias. Significant gold mineralization at 

the Amelia prospect east of Magdalena de Kino is in a 

Cretaceous(?) carbonate sequence. The trace element 

suite Au, Ag, As, Sb, and Ba is similar to that found 

in similar deposits in the Western United States and 

reflects the geologic similarity of the Basin and Range 

province in Sonora with that in Nevada. 

REFERENCE 

Silberman, M.L., Giles, D.A., and Graubard-Smith, Cinda, 

1987, Characteristics of gold deposits in northern Sonora, 

Mexico: Preprint, XVII Convencion Nacional de Associacion Ingenieros de Minas, Metalurgistas Y Geologos de 

Mexico, A.C., 18 p. 

Proterozoic Anorogenic Granite-Rhyolite 

Terranes in the Midcontinental United StatesPossible Hosts for Cu-, Au-, Ag-, U-, and REEBearing Iron-Oxide Deposits Similar to the 

Olympic Dam Orebody 

P.K. Sims, K.j. Schulz, and Eva B. Kisvarsanyi 

The Olympic Dam orebody is the largest and most 

valuable of several iron-oxide-rich deposits on the Stuart 

shelf in South Australia. Its copper content ranks with that 

of Chuquicamata, and its uranium content constitutes about 

10 percent of the world's estimated uranium resources. It 

contains about 1.2x 106 kg of gold, 7X 106 kg of silver, and 

about 0.15 percent rare-earth elements (REE's). By any 

standard, it is one of the world's largest orebodies. 

It has been suggested that the Olympic Dam orebody 

is a variant of a class of iron-oxide-rich deposits that 

includes the deposits of Kirunavaara, Sweden, and southeastern Missouri. These deposits are characterized by large 

tonnages of iron ore (magnetite and (or) hematite), ubiquitous apatite, local carbonate, and anomalous abundances of 

barium, fluorine, uranium, thorium, and REE. Contents of 

metals other than iron are extremely variable. The deposits 

occur in a continental setting, have a close spatial and 

temporal association with anorogenic (A-type) granite and 

rhyolite, and at the orebody scale are enclosed in brecciated 

wall rock. Their ages cluster at about 1.4 to 1. 7 Ga. 

Because of the extensive Proterozoic anorogenic 

terranes in the midcontinental United States and the several 

known iron-oxide orebodies in southeastern Missouri, the 

1.48-Ga St. Francois terrane, in particular, and other 

terranes of both older and younger ages merit consideration 

as possible exploration targets for mineral deposits similar 

to the Olympic Dam deposit. The anorogenic terranes are 

the ( 1) 1. 83-Ga granite-rhyolite suite in central Wisconsin, 

(2) 1. 76-Ga granite-rhyolite terrane in southern Wisconsin, 

(3) 1.48-Ga St. Francois terrane in southeastern Missouri, 

and (4) 1.35- to 1.40-Ga Spavinaw terrane in southern 

Missouri, southern Kansas, and northern Oklahoma. Mesozonal anorogenic granite bodies (1.35-1.50 Ga), which are 

possible deeper seated intrusions related to the high-level 

granite and rhyolite, are widely scattered within a northeasttrending belt that traverses the midcontinent region. The 

dominant rock types in all the bodies are potassium-rich, 

alkali feldspar granite and associated ash-flow tuffs. These 

rocks contain anomalous amounts of the same lithophyllic 

minor elements present in the iron ore bodies. The anorogenic rocks have been interpreted as partial melts of older 

(1.7-1.9 Ga) calc-alkaline crustal rocks that experienced 

one or more episodes of partial melting during earlier 

orogenic activity. The an orogenic rocks are believed to 

have formed in an extensional environment and could have 

had associated evolved, oxidized iron-rich hydrothermal 

systems capable of generating metal deposits similar to that 

at Olympic Dam. 

Alteration patterns can be a guide to mineral deposits. 

In the St. Francois Mountains, propylitic alteration of the 

country rocks is apparently spatially associated with iron 

orebodies. The alteration of primary biotite and hornblende 

to hematite and magnetite could be related to hydrothermal 

activity associated with the ore-forming process. 

Potential for Epigenetic Gold and Sedextype Pb-Zn-Ag-Ba Deposits in the Taconic 

Allochthons, Eastern New York and Western 

Vermont 

john F. Slack and Kenneth C. Watts, Jr. 

Geologically based ore deposit models, supported by 

mineral occurrences and geochemical data, suggest a potential for epigenetic gold and sedimentary exhalative (sedex) 

type Pb-Zn-Ag-Ba deposits in the Taconic Allochthons of 

eastern New York and western Vermont. The Taconic 

Allochthons consist of a largely metasedimentary slope-rise 

sequence of late Proterozoic through Middle Ordovician 

66 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
age. Principal lithologies are slate and graywacke; some 

sequences contain minor intercalated carbonate, quartzite, 

and (or) chert. The slates include red, green, purple, and 

black varieties; the black slates are carbonaceous and 

commonly sulfidic. These rocks are deformed by complex 

folds and many thrust faults and are metamorphosed to the 

lower greenschist facies. Posttectonic, high-angle extensional faults of Mesozoic age occur locally, some of which 

are filled by mafic dikes. 

The best potential for stratabound Pb-Zn-Ag-Ba 

deposits exists at two stratigraphic levels in rocks of the 

Giddings Brook tectonic slice within the structurally (and 

topographically) low Taconics. Several lines of evidence 

indicate a sedex potential within the Early Cambrian 

Browns Pond Formation (=Nassau Formation). This evidence includes (1) a small stratabound lead-zinc deposit 

within the Mudd Pond Quartzite Member near White Creek, 

N.Y.; (2) widespread products of syndepositional faulting, 

including intraformational conglomerates that locally contain clasts of massive pyritic sulfide; and (3) significant 

geochemical anomalies in panned heavy-mineral concentrates of stream sediments from outcrop areas of the Browns 

Pond Formation. The second potential is assigned to the 

cherts and black slates that constitute the Middle Ordovician 

Mt. Merino Formation (also within the Giddings Brook 

slice). The Mt. Merino is a time-stratigraphic equivalent of 

the Beauceville Formation in southeastern Quebec. The 

Beauceville hosts the stratiform Champagne deposit, a 

pyrite- and pyrrhotite-rich massive sulfide body that contains significant Au, Ag, Zn, Pb, and minor Cu. The overall 

sedex potential of the Taconic Allochthons is further supported by comparison with the geology and ore deposits of 

the Selwyn basin in the Yukon-Northwest Territories, the 

Meggen-Rammelsberg region of West Germany, and the 

black shale mineral belt in central Idaho. 

Geochemical data obtained from panned concentrates 

include elevated values for Pb (to 10,000 ppm), Cu (to 

7,000 ppm), Ba (to > 10,000 ppm), Zn (to 1,000 ppm), Sn 

(to >2,000 ppm), and Mn (to 7,000 ppm) in many samples, 

and concentrations of Ag, Au, As, Be, Bi, Sb, Co, and Mo 

in some samples. Map plots of these element distributions 

show that drainages containing anomalous Ba, Zn, Sn, Ag, 

Au, As, Bi, and Sb are largely restricted to the Giddings 

Brook slice in the low Taconics, whereas elevated values 

for cobalt and arsenic are more widespread in the high 

Taconics (Dorset Mountain slice); anomalous lead and 

copper occur in both the low and high Taconics. Barite, 

celestite, and fluorapatite have been identified in the concentrates, but the mineralogic host of the tin, which is 

currently being investigated, is still uncertain. In preliminary microscope scans, cassiterite appears to be absent, and 

tin could be present in stannite or other sulfosalt minerals. 

The gold anomalies may have sources in disseminated and (or) epigenetic vein mineralization. The anomaly 

pattern for gold is scattered and erratic, which is partly a 

function of limited sampling and poor analytical precision 

and partly a reflection of the discrete distribution of bedrock 

source(s). Significantly, rocks in part coeval with those of 

the low Taconics in southeastern Quebec (Ordovician 

Magog Group) contain local concentrations of gold in black 

slates (such as at Ruisseau Castle and Rapides du Diable). 

Comparable geologic settings are found in the Jeseniky 

Mountains of the Bohemian Massif in Czechoslovakia and 

in the black shale belt of central Idaho. In the Bohemian 

Massif, significant gold is known in veinlet and stockwork 

deposits within complexly deformed black slates; these 

deposits also contain anomalous tin. In central Idaho, gold 

occurs locally in high-grade lead-silver vein deposits that 

have concentrations of Cu, Sb, As, and Sn. Favorable areas 

for the occurrence of these types of epigenetic gold deposits 

in the Taconic Allochthons are along and near Ordovician 

thrust faults and at the intersection of these thrust faults and 

high-angle Mesozoic faults. 

Application of Developing Technology in 

Airborne Geophysics, Effie-Coon Lake Complex, 

Minnesota 

Bruce D. Smith, V.F. Labson, Robert E. Bracken, Robert 

j. Bisdorf, Viki Bankey, Robert P. Kucks, Robert j. Horton, Michael G. Medberry, Jay A. Sampson, and J.L. Plesha 

A program to improve airborne geophysical data 

acquisition and interpretation has been implemented by the 

U.S. Geological Survey (USGS). The Effie-Coon Lake area 

is one of four areas chosen to test new geophysical methods 

to map geologic features favorable for buried mineral 

deposits. Airborne geophysical applications are particularly 

important because glacial and Quaternary sediments cover 

95 percent of the bedrock in the area. This presentation 

describes preliminary results from a new magnetic data 

acquisition system and from two new airborne electromagnetic (EM) systems. 

The Effie-Coon Lake study area, located in northcentral Minnesota, is a 2. 7 -Ga Precambrian terrain and 

consists of the Effie granitic intrusive complex and the 

Zeisser' s Island zoned intrusive body surrounded by 

metasediments and metavolcanics. The zoned intrusive 

body thought, from limited outcrops and shallow drilling, to 

be mainly quartz monzonite is defined mostly from aeromagnetic data. A northwest-southeast-trending 2.1-Ga 

mafic dike system, interpreted from aeromagnetic maps, 

intrudes the metamorphic sequences and intrusive complexes. Several types of mineral deposits could be present in 

the area including base-metal, gold, and platinum group 

element deposits. Advanced airborne geophysical methods 

are needed to identify subtle geologic features favorable for 

buried mineral deposits. 

USGS Research on Mineral Resources-1989 Program and Abstracts 67 
93° 45' 

4 a• o o · 

47 " 37 . 5' 

Figure 1. Aeromagnetic signatures of two intrusive complexes, north-central Minnesota. The gray-scale-shaded 

relief map shows magnetic field highs as light areas and 

lows as dark areas. Shading has been produced mathematically by simulated illumination from the northeast 

that produces shadows on the southwest side of magnetic 

New airborne magnetic field surveying instrumentation with improved resolution has been tested for geologic 

mapping applications. The instrument, a ring core flux-gate 

magnetometer, measures vertical and horizontal components of the Earth's magnetic field. Systems commonly 

used in airborne surveys measure only the total magnetic 

field. Additional high precision data from component measurements can be used to improve interpretation of the 

location and magnetization of bedrock features (fig. 1). For 

example , more detailed interpretation of highly magnetic 

iron formations and mafic bodies is important in identifying 

geologic features (host rock, alteration, and structures) that 

93° 7 .5 ' 

highs. The epipluton (A) is a gran itic complex having 

subtle magnetic expression. The Zeisser's Island zoned 

intrusive body (B) is thought to be a qua rtz monzanite. 

Map is approximately 40 by 40 km. [Smith and others 

abstract] 

could be associated with gold deposits in the Effie-Coon 

Lake area. 

The two new EM systems may be effective tools for 

regional and detailed three-dimensional mapping of electrical resistivity. In general, mapping of electrical properties 

provides complementary information to aeromagnetic and 

radiometric surveys. The two EM systems map shallow and 

deep resistivity variations. The shallow penetrating system, 

termed VLF for Very Low Frequency, measures EM fields 

generated by distant Naval communication stations at about 

25 ,000 Hz. Unlike commercial VLF instrumentation, the 

components measured by the USGS system are used to 

68 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
compute apparent resistivity maps. The deeper penetrating 

system developed by the USGS measures the effect of 

magnetic fields generated by power lines at 60, 180, and 

300Hz. 

Apparent resistivities computed from the VLF data 

average 300 to 400 ohm-m; some areas have resistivities as 

high as 1,000 to 2,000 ohm-m and as low as tens of ohm-m. 

High resistivities are a guide to locating shallow or exposed 

resistive bedrock that is helpful in geologic mapping. The 

Effie complex is characterized by high apparent resistivities 

(>400 ohm-m) that may help to define the boundaries of the 

intrusive complex not clearly defined by the gravity or 

magnetic data. Areas of low resistivities can be attributed to 

either thick glacial till or conductive shallow bedrock (for 

example, graphite in metasediments). 

The airborne EM instrument that measures magnetic 

fields generated by power lines has a depth of penetration 

approximately ten times that of the VLF system. This depth 

of penetration is deeper than many commercial active 

source systems. Thus, the system is much more sensitive to 

variations in bedrock resistivity than the VLF system. The 

measurements are processed to enhance mapping of conductive bedrock features that may be buried at depths of 

hundreds of meters. Important conductive bedrock features 

in the study area are mainly graphitic units in the metasediments. The distribution of these units is useful in understanding bedrock stratigraphy and structure. In addition, 

some conductive anomalies may indicate massive metallic 

mineralization. 

The VLF and power line EM methods are passive 

because the instrumentation does not include a transmitter; 

absence of a transmitter greatly reduces the complexity, 

weight, and cost of the systems. Successful development 

and application of methods described in this study are 

critical steps in the development of electrical methods that 

can be routinely used to complement other airborne geophysical data such as magnetic and radiometric measurements. 

Geology, Geochemistry, and Age of the Gejiu 

Batholith and Associated Polymetallic Deposits, 

Southern China 

Lawrence W. Snee and Wang Zhifen 

The 320-km2 Gejiu batholith, composed of more than 

10 mafic and felsic intrusions, is well known for its large 

granite-hosted tin deposits but also is mined for Cu, Pb, Zn, 

W, Bi, Be, F, and S. The batholith is divided into eastern 

and western parts by the postmineralization, north-trending 

Gejiu normal fault. Intrusion compositions and mineral 

deposit types are distinctly different on opposite sides of the 

fault. Plutons in the west, grouped by age from oldest to 

youngest, include (1) gabbro, diorite, and monzonite: (2) 

granodiorite, granite porphyry, and granite; and (3) syenite 

and nepheline syenite. Lead and zinc are disseminated as 

galena and sphalerite in many western plutons; tin occurs as 

disseminated cassiterite in granite porphyry. East of the 

Gejiu fault, minor exposures of a large, subsurface granite 

body crop out within Triassic sedimentary rocks. Core 

drilling indicates that these outcrops represent parts of a 

continuous, 20-km-long granite pluton of relatively uniform 

composition but variable texture. Major tin deposits are 

associated with the numerous cupolas of this pluton and 

occur in skarn, greisen, and open-space veins. 

Preliminary 40 ArP9 Ar age spectra constrain the age 

and the duration of tin mineralization and intrusive activity. 

Diorite in the west is 84.1 ±0.2 Ma. Granite emplacement 

and tin mineralization in the east took place between 

82.6±0.2 and 80.6±0.1 Ma. Nepheline syenite was 

intruded in the west at 79.9±0.5 Ma. The age spectra show 

that tin mineralization and emplacement of associated 

granites occurred over at least 2 million years and that 

temporal-spatial relations among the tin-mineralized granites are resolvable. Relative age relations and isotopic data 

indicate that emplacement of nepheline syenite and formation of associated disseminated galena and sphalerite took 

place near the end of, or subsequent to, tin mineralization. 

Thus, because lead-bearing mineral deposits, associated 

with plutons that are older than the tin-mineralized granites, 

are also found west of the Gejiu fault, formation of lead 

deposits was either a multicycle phenomenon or occurred 

over a longer time period than formation of tin deposits. 

Compositional and isotopic data are available for 

approximately 200 samples of plutonic rocks, altered and 

unaltered country rocks, and minerals from the Gejiu area. 

The majority of the granitic rocks are weakly to moderately 

peraluminous; gabbro, diorite, and syenite are metaluminous. Mafic, intermediate, and syenitic plutons east of the 

Gejiu fault are not related by simple magmatic processes to 

granites east and west of the fault. Relative to other Gejiu 

plutons, granites are variably enriched in rubidium, cesium, 

tantalum, and uranium and depleted in barium, strontium, 

and hafnium. Concentrations of Rb, Cs, Ta, U, Hf, and Th 

are uniform in nongranitic plutons, but strontium and 

barium decrease with increasing Si02 . Granites are depleted 

in light rare-earth elements (LREE) ( <200 times chondrite 

abundance) and enriched in heavy rare-earth elements 

(HREE) (>20 times chondrite abundance) relative to nongranitic rocks (LREE=200-800 and HREE=S-20 times 

chondrite abundance). Large europium anomalies are characteristic of granites. Strontium initial ratios for all Gejiu 

plutons are elevated, but the ratios for western plutons are 

less than 0. 712, whereas the ratios of eastern plutons are 

greater than 0. 716. The strontium isotopic signature and the 

major and trace element compositions of all plutons were 

probably derived from a heterogeneous, chemically 

evolved, continental source. 

USGS Research on Mineral Resources-1989 Program and Abstracts 69 
Granitic plutons associated with Gejiu tin deposits are 

compositionally distinct from nonproductive granites. Productive granites are characterized by 69 to 75 weight 

percent Si02 ; Na20/K20 of 0.59 to 0. 74; enrichment in Rb 

(300-1,000 ppm), Cs (10-70 ppm), Ta (3-17 ppm), U 

(10-60 ppm), F (1 ,000-4,000 ppm), and Sn (10-30 ppm); 

and depletion in Ba ( <300 ppm), Sr ( <300 ppm), and Hf 

( <7 ppm). Rare-earth-element (REE) patterns of productive 

granites show relative depletion in LREE (35-110 times 

chondrite abundance), large europium anomalies, and 

enrichment in HREE (20-40 times chondrite abundance). 

REE patterns for biotite from these granites are similar to 

the REE patterns of the whole rock except that biotite, 

which forms about 10 modal percent of the rock, is enriched 

10 times in total REE; thus, biotite is the principal REE 

carrier. In contrast, biotite from nonproductive plutons is 

not the primary REE carrier. The tin content of biotite from 

plutons that have less than 69 weight percent Si02 is less 

than 32 ppm. In contrast, the tin content of biotite from 

granites that have more than 69 weight percent Si02 is 

greater than 100 ppm to nearly 700 ppm. However, plutons 

that have significant tin deposits contain biotite having 

lower tin contents (that is, nearer 100 ppm). 

A possible mechanism for tin mineralization that 

would account for these chemical characteristics might 

include ( 1) a plutonic source region relatively enriched in 

tin, (2) an evolved granitic magma that concentrated tin, (3) 

episodic thermal activity that occurred over at least 2 

million years, and ( 4) either a late-stage fluid phase into 

which tin from the granitic magma was partitioned or a 

late-stage fluid phase that leached tin from biotite and 

deposited tin in the altered host rock. 

The Tooele 1° x 2° Quadrangle, Western 

Utah: An Example of a CUSMAP Preassessment Study 

Holly j. Stein, Viki Bankey, C.G. Cunningham, David R. 

Zimbelman, Michael A. Shubat, David W. Brickey, D.L. 

Campbell, and M.H. Podwysocki 

The Tooele 1 o X 2° quadrangle in western Utah lies 

along the eastern margin of the Basin and Range province 

and contains a wealth of mineral deposits, including the 

Bingham copper and Mercur gold deposits. It is located 

north of the Richfield and Delta 1 o x 2° quadrangles, which 

represent completed and in progress CUSMAP (Conterminous United States Mineral Assessment Program) quadrangles, respectively. The eastern half of the Tooele quadrangle has been the site of continuous, intensive mineral 

exploration for over a century. The western half of the 

quadrangle is covered largely by the Great Salt Lake Desert, 

and this area offers an excellent opportunity to test new 

methods for evaluating mineral potential in concealed 

geologic terranes. A preassessment of the _status of geologic, geochemical, geophysical, remote sensing, and mineral resource information for the Tooele quadrangle was 

conducted by a team of U.S. Geological Survey and Utah 

Geological and Mineral Survey geologists. As part of our 

preassessment, more than 40 persons from academia, industry, and Federal and State surveys, who are working in or 

have geologic knowledge of the Tooele quadrangle, were 

contacted. 

Results of the Tooele CUSMAP preassessment study 

include 

(1) Geologically favorable indicators for gold-bearing 

skams resembling those at Carr Fork were recognized 

throughout much of the quadrangle. 

(2) A preliminary model was developed for the occurrence of deposits of scandium, a strategic and critical 

commodity. Ore deposit models for scandium need 

further development. 

(3) Variations in previously established mineral trends 

were recognized. For example, the Oquirrh-Uinta 

mineral belt may end at Bingham or, alternatively, 

may extend through the Dugway district to Gold Hill 

at the southwest comer of the Tooele quadrangle. The 

Oquirrh Mountains may represent a mineral belt that 

extends south from the North Oquirrh mineral occurrences through the Barney's Canyon, Bingham, 

Stockton, Ophir, and Mercur deposits to the rich baseand precious-metal deposits of the North, Main, and 

East Tintic districts in the East Tintic Mountains. 

(4) Porphyry-related ore systems are exposed at generally 

high levels. Surface exposures that intersect high 

levels of economically productive porphyry systems 

are generally characterized by a lack of significant 

igneous rock outcrop and an enrichment in elements 

that concentrate at the margins and tops of large, 

ore-bearing systems. This observation suggests that 

additional porphyry-related deposit types may be 

present at shallow depths. 

(5) A structurally complex, concealed terrane beneath the 

Great Salt Lake Desert that has potential for Spor 

Mountain-type beryllium-fluorine-uranium deposits 

was recognized. Geophysical gravity and aeromagnetic data have targeted a buried, northwest-trending, 

grabenlike structure beneath the Great Salt Lake 

Desert that intersects Spor Mountain-type deposits in 

the Delta 1 o x 2° quadrangle to the south. Topaz 

rhyolites, which are associated with Spor Mountaintype mineral deposits in the Delta quadrangle, are 

present in small quantities along the margins of this 

proposed graben in the Tooele quadrangle. 

( 6) The quadrangle has high potential for nonmetallic 

mineral deposits, especially salt, brine, sand and 

gravel, and geothermal resources. 

A new CUSMAP study of the Tooele quadrangle 

would offer benefits to Federal, State, and local agencies, 

70 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
industry, and academia. Information from a new study 

would assist mineral exploration and define the mineral 

resource potential of the region. 

Mosaic Faulting as a Guide to Mineral 

Exploration in the Richfield 1 o x 2° Quadrangle, 

Western Utah 

Thomas A. Steven 

A complex network of faults in the Richfield 1 o X 2° 

quadrangle of western Utah not only divides the area into 

fault-block mountains and basins typical of the Basin and 

Range and High Plateaus provinces, but also breaks the 

larger blocks into numerous smaller structural units. Over 

most of the area, a network of north-northwest- and 

north-northeast-trending faults of late Cenozoic age and 

basin-and-range orogenic affinity creates a rhombic to linear 

fracture pattern reflected in the modem topography. Local 

areas showing distinctly different fracture patterns occur 

within the more closely restricted east-northeast-trending 

Pioche-Marysvale mineral belt that includes most of the 

igneous intrusions and virtually all of the known igneousrelated ore deposits in the quadrangle. In general, these 

fracture patterns are mosaic but exhibit numerous local 

variations. In many places these mosaic patterns can be 

dated as having formed in Miocene time; locally they are 

closely associated with mineralized or altered rocks. 

The areas of mosaic faulting correspond spatially to 

areas interpreted as being underlain by early Miocene 

igneous centers, and the mosaic faulting is interpreted to 

have formed above rising bodies of coeval magma. Small 

cylindrical intrusive bodies are believed to underlie areas 

that show crudely radial and concentric fracture patterns. 

Moderately sized, elongate intrusive bodies are reflected by 

box or ladder mosaic patterns that consist of rectilinear 

groups of longitudinal and transverse fractures. Equally 

important, no fractures exist in areas where intrusions are 

widely exposed. Some mosaic fault patterns closely reflect 

known mineralized areas, and others include areas believed 

to have good exploration potential. 

Separating mosaic fault patterns from coexisting fault 

patterns of different origins can be likened to producing 

many kinds of residual maps. Reasonably detailed geologic 

maps are essential, and a detailed knowledge of local 

geology is extremely important. Experimentation using 

both logical analysis and subjective imagination is required. 

Visual representations seem more valuable than statistical 

summaries in recognizing many fault patterns. 

Three-Dimensional Characterization of Regional 

Structures Using an Advanced Geographic Information System 

D.B. Stewart, B.E. Wright, J.D. Unger, J.D. Phillips, and 

L.H. Liberty 

Exceptionally detailed images of geologic structures 

in the upper 10 km of the Earth's crust can be obtained by 

using three-dimensional geographic information systems 

(GIS) at the U.S. Geological Survey's GIS laboratory in 

Reston, Va. The GIS is accessed through a network of 

computers to produce images that are composed of geographic, geologic, and geophysical data. These data sets are 

mostly independent, and models, such as those developed 

by using geologic and gravity data, can be tested by 

comparison with seismic reflection or refraction results. 

Models that can satisfy all the data sets are quite detailed 

and have a strong probability of being correct. 

Structures readily imaged in the upper 10 km of the 

crust include large dikes, stocks, and batholiths (with 

indications of their overall composition); folds to depths of 

4 km in pyrrhotite-bearing carbonaceous metapelite; coverbasement relations in the Connecticut Valley-Gaspe synclinorium in Quebec; the Merrimack synclinorium in central 

Maine; and major thrust and strike-slip faults in the region. 

Details of midcrustal features, such as major Taconic 

thrusts along which the former Iapetus ocean was closed 

and the Chain Lakes Massif and its cover sequence were 

emplaced upon North American crust of Grenville age, can 

be resolved to depths approaching 24 km. The boundaries 

between other tectonostratigraphic terranes in the northern 

Appalachians seem to penetrate the entire crust. The Moho 

at the base of the crust can be readily contoured on the basis 

of coincident results from seismic reflection and refraction. 

Taken together, these data sets greatly facilitate description 

and modeling of the processes that created the Appalachian 

orogen. 

Development of the models has required the assembly 

of each data set based upon consistent geographic projections and compatible formats. A digital line graph (DLG) 

attribute code was created to identify the lines and areas of 

all stratified and plutonic rocks shown on the digitized 

geologic maps of southeastern Quebec, Maine, and the Gulf 

of Maine. Each mapped sedimentary or volcanic rock type 

contains an attribute code for age, lithology, inferred 

tectonic setting, and formation (member, lentil) name. Each 

intrusive rock contains an attribute code describing the age, 

name, composition, and distinctive minerals or textures. 

Linear geologic features on the map are also assigned DLG 

codes. The digital data sets are being assembled on 

CD-ROM disks. Appropriate software also is being 

included to display selected images. Thus, users will be 

able to evaluate the basic data used for the models and can 

view certain selected models by using micro- or minicomUSGS Research on Mineral Resources-1989 Program and Abstracts 71 
puters that support CD-ROM disk drives. Users also will be 

able to change scales, edit or add new data, and create new 

models for their specific purposes. 

Delta CUSMAP Project: Mineral Assessment in 

the Tintic-Deep Creek Mineral Belt of the 

Eastern Great Basin, Utah 

Douglas B. Stoeser, Carol N. Gerlitz, Constance j. Nutt, 

Holly j. Stein, john Hand, Michael A. Shubat, and judith 

L. Hannah 

The Delta CUSMAP (Conterminous United States 

Mineral Assessment Program) project is an appraisal of the 

mineral resource potential of the Delta 1 o x 2° quadrangle 

(lat 39-40° N. and long 112-114 o W.) of western Utah. The 

project began in November 1985 and is scheduled for 

completion in November 1990. 

Most major mineral occurrences and deposits in the 

quadrangle are associated with Cenozoic magmatism concentrated in the Tintic-Deep Creek mineral belt in the 

northern part of the quadrangle. The mineral belt, explored 

for high-grade base- and precious-metal deposits since the 

late 1800's and for porphyry copper, molybdenum, and 

gold since the 1950's, contains vein and replacement 

deposits, jasperoids, and skarns that are being explored and 

developed for gold. New mining operations are underway in 

the Tintic and West Tintic districts, and one carbonatehosted disseminated gold deposit in the Drum Mountains 

was recently mined out. 

Cenozoic igneous rocks in the Delta quadrangle are 

divided into two groups: precrustal extension (41-31 Ma) 

and syncrustal extension (21 Ma-present). The older group 

consists of shoshenitic, andesitic, latitic, dacitic, and rhyolitic volcanic and related intrusive rocks. These rocks are 

related to poorly understood multiple caldera-forming 

events within the mineral belt. The younger group is 

bimodal and consists of rhyolite and basalt to basaltic 

andesite in the north-central and southeastern part of the 

quadrangle. Many of the rhyolites are peraluminous and 

contain topaz. 

Preextensional hydrothermal metallic mineral deposits are present in most mountain ranges within the mineral 

belt, including the important Main Tin tic, East and West 

Tintic, and Detroit (Drum Mountains) mining districts. 

These deposits include vein and replacement base- and 

precious-metal deposits, low-grade porphyry coppermolybdenum deposits, and contact metasomatic tungstencopper-gold deposits. These deposits formed from zoned 

hydrothermal systems related to granitoid intrusions. Subeconomic copper-molybdenum porphyry deposits may be 

present in the intrusive core, and zonation outward from the 

core includes (1) Cu±Au veins, (2) Pb±Ag replacement 

deposits, and (3) zinc and (or) manganese replacement 

deposits. Jasperoids (±Au) occur in the two outer zones. 

Synextensional mineral deposits include the 

beryllium-fluorine-uranium deposits at Spor Mountain and 

other similar but minor occurrences elsewhere in the quadrangle. The Spor Mountain deposits may be related to a 

larger hydrothermal system associated with evolved granitic 

intrusions from which other deposit types may have formed. 

Bismuth Minerals Associated with Placer Gold, 

Battle Mountain Mining District, Nevada 

Ted G. Theodore, Gerald K. Czamanske, Terry E.C. 

Keith, and Robert L. Oscarson 

Placer gold nuggets collected at Paiute Gulch, in the 

northern part of the Battle Mountain mining district, 

Nevada, include several that show gold intergrown with 

bismuth-bearing phases, including bismutite (Bi2(C03)02), 

tellurobismuthite (Bi2 Te3), and sillenite ( -y-Bi20 3). Sillenite, an unusual polymorph, which is body-centered cubic 

and has been reported elsewhere to possibly contain minor 

silicon, occurs in a wormy myrmekitic or eutectoid-type 

intergrowth with gold. Electron microprobe analyses show 

the Battle Mountain sillenite to be relatively homogeneous, 

to be free of silicon, calcium, and iron, and to contain less 

than 0.04 weight percent sulfur. The bismutite seems to 

paragenetically postdate the sillenite. 

By using an image-processing system, we determined 

the areal percentages of the component minerals in the 

eutectoid-type intergrowth. The overall range for eight 

areas examined is 34.5 to 46.3 areal percent gold. However, seven of the eight determinations fall in the narrow 

range of 42.0 to 46.3 areal percent gold; this content 

corresponds well with the gold content of maldonite 

(Au2Bi). The system gold-bismuth shows a peritectic at 373 

°C, the upper stability limit for Au2Bi (Hansen, 1958). 

Thus, the nugget texture is unlikely to have developed from 

deposition above 373 °C. This gold-sillenite intergrowth, of 

maldonite bulk composition, is considered to have resulted 

from initial crystallization of maldonite at or below 373 °C 

and perhaps even from a melt (temperatures between 373 

and 241 °C). Subsequently, the maldonite is presumed to 

have broken down to yield the eutectoid-type texture. 

Barton and Skinner (1979) noted that maldonite becomes 

unstable with respect to gold and bismuth at approximately 

113 °C. Ramdohr (1969) noted that he had never seen 

maldonite and suspected that myrmekitically intergrown 

gold and bismuth in an approximate 1 to 1 ratio represents 

decomposed maldonite. At Paiute Gulch, the bismuth 

fraction of the intergrowth has been oxidized to sillenite at 

a temperature less than 113 °C. 

Other placer gold nuggets contain abundant, euhedrally terminated quartz crystals draped with gold. At room 

temperature, fluid inclusions in the quartz are liquid rich 

and vapor rich, suggesting boiling. Homogenization tern72 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
peratures of liquid-rich fluid inclusions range from 150 to 

355 °C (mean, 265 °C). The lack of fluid inclusions 

containing daughter minerals suggests that the bulk of the 

placer gold was not genetically associated with hightemperature saline stages of nearby vein, breccia pipe, and 

skarn formation. Rather, the nuggets containing bismuth 

minerals are thought to have been derived from lower 

temperature stages in gold-bearing skarn that are known to 

contain significant late-stage bismuth minerals. 

Although a gold-bismuth association has been 

reported previously in the district at the Fortitude gold skarn 

deposit, this study further confirms a strong association 

between gold and bismuth. Antweiler and Campbell (1982), 

Orris and others (1987), and Meinert (1988) have shown 

that bismuth is a characteristic trace element in many 

gold-bearing contact metasomatic systems. There are skarns 

southeast of Paiute Gulch, proximal to the southeastern lobe 

of a 38-Ma composite tonalite. However, these skarns 

apparently are high-temperature deposits and show abundant liquid-vapor homogenization of highly saline (30 to 60 

weight percent NaCl equivalent) fluid inclusions in the 

range from 500 to 600 °C. Moreover, these skams are 

essentially free of retrograde, hydrosilicate alteration stages 

and are unmineralized. Some of the more distal skams, as at 

the Overlook group of claims, may be likely candidates for 

lode sources that contributed to the placers at Paiute Gulch. 

Indeed, some wire gold has been panned from gossans at 

this locality. Other possible sources for the placer gold may 

be the quartz stockworks that surround a breccia pipe and 

the monzogranite at a nearby promontory named Bluff. 

REFERENCES 

Antweiler, J.C., and Campbell, W.L. 1982, Gold in exploration 

geochemistry , in Levinson, A.A., ed. , Precious metals in 

the northern cordillera: Association of Exploration 

Geochemists Special Publication 10, p. 33-44. 

Barton, P.B. , Jr. , and Skinner, B.J. , 1979, Sulfide mineral 

stabilities, in Barnes, H.L. , ed., Geochemistry of hydrothermal ore deposits: New York, John Wiley , p. 278-403. 

Hansen, Max, 1958 , Constitution of binary alloys: New York, 

McGraw-Hill Book Company, Inc ., 1 ,305 p. 

Garimperiros (prospectors) operating sluice box at new major tin placer deposit C-75, Rondonia tin district, Brazil. 

[Thorman and others abstract] 

USGS Research on Mineral Resources- 1989 Program and Abstracts 73 
Meinert, L.D., 1988, Gold and silver in skarn deposits: Geological Society of Australia, Inc., Bicentennial Gold 88, 

Extended Abstracts, Poster Programme, v. 2, p. 614-616. 

Orris, G.J., Bliss, J.D., Hammarstrom, J.M., and Theodore, 

T. G., 1987, Descriptions and grades and tonnages for 

gold-bearing skarns: U.S. Geological Survey Open-File 

Report 87-273, 50 p. 

Ramdohr, Paul, 1969, The ore minerals and their intergrowths: 

Oxford, Pergamon Press, 1,174 p. 

New Tin Deposits in the Amazon Basin, Brazil 

C.H. Thorman, L.J. Drew, and M. Drucker 

Two new tin deposits, Pitinga and Serrinha, are 

having a major positive impact on Brazil's tin production. 

Pitinga, the world's largest tin mine, in the Mapuera 

district, began production in 1982 and is still in an early 

stage of development (presently only placer operations). 

Serrinha, in the well-known Rondonia district, was discovered in 1987 and is a high-grade placer mine. 

The Mapuera mineral district, north of Manaus, 

was established in 1982. A suite of Early to Middle 

Proterozoic volcanic, intrusive, and sedimentary rocks 

underlies the district. The intrusive rocks include an older 

biotite granite suite (about 1800 Ma) and a younger biotiterapakivi granite suite, including the rocks that host the 

Pitinga deposit. The Madeira granite (about 1685 Ma) is an 

alkali feldspar granite and includes a rapakivi granite, an 

extremely homogeneous biotite granite, and a metasomatic 

granite. This latter granite forms a narrow band that 

encompasses the albitized younger tin-bearing apogranite, 

which hosts the primary Pitinga deposit and is the source of 

rich alluvial deposits. Ore minerals in the apogranite 

include cassiterite, zircon, pyrochlore, columbite, tantalite, 

and xenotime. Pitinga has large reserves of tin (>500,000 

metric tons), zirconium, niobium, tantalum, and some 

rare-earth elements. 

The Rondonia tin district, in the western part of the 

Brazilian Amazon basin, includes many producing and 

abandoned tin mines. The Rondonia suite of anorogenic 

plutons, ranging in age from about 1150 to 925 Ma, 

includes rapakivi to biotite granites (most are chemically 

evolved) that were emplaced in shallow to subvolcanic 

settings as circular bodies up to 20 km across. Many of 

these granites have associated ring fracture systems. The 

granites intruded a gneissic basement (Xingu complex, 

> 1500 Ma) and formed primary deposits in greisen caps 

(Santa Barbara), veins adjacent to the plutons (Serra da 

Onca), veins in the ring fracture systems (Massangana), and 

explosively brecciated greisenized gneiss (Potosi). The 

present land surface is probably not much below the 

Precambrian land surface when the primary deposits were 

formed, because explosion breccias, ring fractures, and 

associated volcanic rocks in and near the deposits indicate 

shallow emplacement (perhaps 2-3 km deep). Rondonian 

placer deposits are high grade; they include deeply weathered primary deposits as eluvial material and grade outward 

into colluvial and alluvial material 3 to 4 km downstream. 

At Serrinha, an area of about 20 km2 is being mined 

by more than 12,000 laborers and about 8,000 to 10,000 

metric tons of tin will be produced in 1988. The setting is 

reminiscent of the 1849 California gold rush placer operations. Quartz-cassiterite veins (3 m wide) and cassiterite 

boulders weighing up to 20 kg crop out on the discovery 

hill. A breccia containing cassiterite greisen with topaz 

matrix underlies a smaller hill. The country rock appears to 

be entirely basement gneiss and schist (Xingu complex). 

The deposit at Serrinha occurs on the northern edge of a 

circular feature 18 to 20 km across and may be part of a 

large near-surface explosive vein-greisen system like that at 

Potosi. 

The potential for discovery of new tin deposits in the 

well-known Rondonia district is very high, as indicated by 

the recent discovery of Serrinha. This is extremely important because production, which began in 1965 in Rondonia, 

is rapidly declining and because most of the mines in the 

district are expected to close in 3 to 5 years. The potential 

for discovery of new deposits in the Mapuera district is less 

clear because only one deposit has been found. Several 

factors will slow tin exploration in the near future in the 

Amazon: the static demand for tin and its probable continued low price; the enormity of the Pitinga deposit, making 

competition by other companies difficult; and the difficult 

and expensive exploration logistics in the Amazon. 

Geochemistry of Soils in the Carson River Valley, Nevada 

Ronald R. Tidball 

The Carson River, a major drainage system originating on the eastern flank of the Sierra Nevada near the 

California-Nevada border, flows east to the Carson sink, a 

closed basin. The upper half of the drainage system has a 

sufficient gradient such that coarse-grained alluvial fans are 

common, and, in part, the river is entrenched through 

intervening hilly terrain. In the lower half of the valley, the 

river emerges onto the former shores of Lake Lahontan of 

Pleistocene age and finally terminates in the lowest depression of the Lahontan lake bed, the Carson sink, where the 

water either accumulates or evaporates depending on the 

climatic cycle. Fine-grained lacustrine sediments and sand 

dunes are common on the higher slopes of the lake bed, and 

clayey alkali flats are extensive on the lower parts of the 

sink. 

74 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
The Carson River valley is the site of a National 

Water Quality Assessment (NA WQA) study where the 

relation between the quality of ground water and the solid 

materials in contact with the water is under investigation by 

the U.S. Geological Survey in cooperation with the U.S. 

Fish and Wildlife Service. One phase of the study is the 

geochemical characterization of the surficial materials 

(soils) throughout the river valley to show the surface 

expression of the elements that might impact the groundwater system. 

Soil samples collected from 397 sites were analyzed 

for total amounts of about 40 elements. Because there 

appear to be two distinct sedimentation provinces, the data 

were divided into two parts: (1) the upper valley, characterized by bedload type deposits and (2) the lake bed, 

characterized by fine-grained water-suspended sediments. 

Element associations were estimated for each area by 

R-mode factor analysis. 

A five-factor model describes the upper valley. The 

factors include (1) a common association offerride elements-Ti, Fe, Co, V, Sc, Cr, Y, and others, (2) Pb and Hg, (3) 

Th and La, (4) Mo, Li, and Se, and (5) Ca, Mg, P, and Sr. 

The lake bed area is described by a six-factor model 

that has similar element associations but differs in detail. 

The factors include (1) an association of ferride elements, 

(2) Th, Ce, La, and Nd, (3) Ca, Sr, and Mg, (4) Hg and Pb, 

(5) Mo, Se, and As, and (6) Na, Li, and Mo. 

The results do not identify a mineralization factor in 

either area. A notable difference between the two areas is 

the presence of the Na-Li-Mo association in the lake bed 

that characterizes the widespread alkali flats, which are 

absent in the upper part of the valley. The Pb-Hg and Hg-Pb 

factors indicate the same association. Mercury is a wellknown environmental contaminant that originated from the 

gold processing mills, located near Carson City, and lead is 

an unexpected companion. Samples that have large factor 

scores in both the upper and lower valleys follow the Carson 

River drainage, indicating that these elements have been 

dispersed by the river system. 

The lower parts of the Carson sink area are characterized by the Na-Li-Mo and the Ca-Sr-Mg factors, indicating evaporites. The Th-La factor of the upper valley area 

probably represents a granitic source rock. The similar 

Th-Ce-La-Nd factor of the lower valley area occurs near a 

source of young basalt and andesite of Tertiary age. These 

rocks tend to have a granitic-type composition rather than 

the ferride that might be expected from such source rocks. 

The Mo-Se-As factor appears to occur in an evaporite 

setting but may also reflect sedimentary rocks in some 

places. 

The results indicate that the geochemistry of soils can 

be related to the source rocks, the depositional environment, and past mining history. The data also serve to guide 

the initiation of future process-related studies. 

Industrial Rock and Mineral Resources of 

Arizona: A Survey of Resource Problems and 

Opportunities by the Producers and Users of 

Resource Information 

Edwin W. Tooker and Larry D. Fellows 

The Arizona Geological Survey (AZGS) and the U.S. 

Geological Survey (USGS) cosponsored a workshop, 

"Industrial rock and mineral resources of Arizona: Problems, opportunities, and recommendations," in Tempe, 

Ariz., May 17-18, 1988. The objectives of the workshop 

were to assess the current status of exploration and development of these resources and to look ahead to the potential 

for expanding this resource base in the State. A group of 

participants from diverse backgrounds in Federal, State, 

and Local government, industry, Indian Nations, and academia convened for the following informal discussion 

sessions: ( 1) current and emerging problem areas for search 

and evaluation of Arizona's industrial rock and mineral 

resources, including expanding sources for data acquisition, 

effective data management, sources of analytical laboratory 

and industrial testing facilities, and land access; (2) status of 

new geotechnical research capabilities to stimulate understanding of environments of deposition and to facilitate 

exploration and discovery; and (3) specialized user resource 

data needs from the State legislature, Federal and State land 

management agencies, the Indian Nations, the mining 

industry, and municipal government agencies. A final 

session was devoted to summarizing the main conclusions 

and presenting program recommendations to the AZGS and 

USGS. In particular, recommendations were made for 

better ways to meet specific present and continuing user 

needs while maintaining an applied and basic research 

competence within increasing budget constraints. 

The workshop proceedings are being prepared for 

publication and public comment. This poster describes the 

agenda and presents some of the results of the workshop 

prior to the publication of the proceeding volume. 

40 ArP9 Ar Studies of Fluid Inclusions in Vein 

Quartz from Battle Mountain, Nevada 

Brent D. Turrin, Edwin H. McKee, Ted G. Theodore, and 

James E. Conrad 

K-Ar and 40 ArP9 Ar age determinations indicate that 

igneous activity and associated hydrothermal mineralization 

at Battle Mountain, Nev., occurred during the Late Cretaceous and in late Eocene to early Oligocene time. Studies 

were undertaken to evaluate the use of fluid inclusions for 

determining the age of hydrothermal events. 40 ArP9 Ar total 

fusion age determinations were done on fluid inclusionbearing quartz veins associated with molybdenum mineralUSGS Research on Mineral Resources-1989 Program and Abstracts 75 
ization. Ages obtained from these experiments are highly 

variable and unreproducible and range from about 300 to 

about 60 Ma. These results led to the initial conclusions that 

the fluid inclusions contained excess 40 Ar and that argon 

might migrate from fluid inclusions along microfractures. A 

series of 40 ArP9 Ar incremental heating experiments were 

performed on a second split of the quartz samples. The 

results from these experiments yield argon temperaturerelease age patterns that suggest the presence of excess 40 Ar. Calculated ages are inversely proportional to potassium content, suggesting a constant amount of excess 40 Ar 

within a relatively large population of grains. The ages 

generally do not correspond to any known igneous or 

hydrothermal event in the area (Late Cretaceous or late 

Eocene-early Oligocene). A third split of the quartz samples 

was analyzed by using a single-crystal laser fusion 40 ArP9 Ar system. Analyzing single grains (approximately 1 

mm3 or less) approaches analysis of the domain size of 

paragenetically homogeneous fluid inclusions. These analyses were used to evaluate the homogeneity of the fluid 

inclusion population. Results are widely variable. There is 

some clustering of the ages but they do not coincide with 

any known igneous or mineralizing event. Additional 

experiments to analyze the argon from fluid inclusions that 

have a simple, single-stage history are underway . For this 

- Scanning electron photomicrographs of authigenic rutile 

and anatase crystals. A: Anatase (arrows) and rutile; 

coarse red sandstone (NS 3-3), Wolfville Formation, Triassic, Minas Basin, near Medford, N. S. B:Rutile; red intertidal mud (NS 1- 7) near Blomidon Formation red beds, 

Triassic, head of St. Mary's Bay, N. S. C: Rutile ; dark red 

intertidal mud (NS 13-3) near Cumberland Group red 

purpose , late Eocene fluid inclusion-bearing vein quartz 

from the northern part of Battle Mountain is used. Variation 

in argon content in these samples that cannot be accounted 

for by radioactive decay of potassium since the late Eocene 

can only be attributed to argon loss (younger ages) or excess 

argon (older ages). 

Silt-size Rutile in Quaternary Sediment of the 

Gulf of Maine-A Large, Unconventional Ti02 

Resource 

Page C. Valentine and judith A. Commeau 

The Gulf of Maine , an embayment of the New 

England margin , is floored by shallow, glacially scoured 

basins that are partly filled with Pleistocene and Holocene 

silt and clay containing 0.7 to 0.8 weight percent Ti02 , 

chiefly in the form of rutile (and anatase). Eleven basins 

together are estimated to contain 563 X 106 metric tons (t) 

Ti02 (to a depth of 10m) in the U.S. Exclusive Economic 

Zone and 169 xI 06 t in Canada, on the basis of analyses of 

surface sediment and of a 22-m core (table 1). The United 

States annually consumes approximately 1 x 106 mt of Ti02 

(as rutile, leucoxene , ilmenite) of which 75 percent is 

- - - - beds, Carboniferous, Chignecto Bay, near Joggins, N.S. 

D: Rutile; clayey silt from sea floor at 270 m in central 

jordan basin, Gulf of Maine . E: Rutile; Cody Shale (USGS 

rock standard SCo-1), Upper Cretaceous, Natrona Co., 

Wyoming. Scale bar= 1 micron. [Valentine and Commeau 

abstract] 

76 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Table 1. Total titanium content of Gulf of Maine basins [Valentine and Commeau abstract] 

Area3 U.S. (Canada) 

Contained Ti02 , (x106 metric tons)4 

Basin Silt and clay Ti02 U.S. (Canada) 

weight percent 1 weight percent 1 avg; n2 km2 1 m5 Sm 10m 

Jordan 95 0.70 0.74; 32 3,412 (1,750) 10.4 (5.4) 75.4 (38.7) 179.5 (92.1) 

Wilkinson-Murray 95 .65 .70; 17 5,103 14.5 104.6 249.2 

Crowell 60 .70 .83; 5 (1 ,503) (2.9) (20.9) (49.9) 

Sharrer-Howell 95 .65 834 2.4 17.1 40.7 

Rodgers 95 .70 612 1.9 13.5 32.2 

Georges 30 .80 .88; 9 103 (1,447) .1 (1.6) .8 (11.5) 2.0 (26.9) 

Lindenkohl 95 .70 444 1.4 9.8 23.4 

Stellwagen 96-986 0. 74-{).836 218 .7 5.2 13.0 

Truxton 95 .70 .78; 3 238 .7 5.2 12.5 

Arnrnen 95 .70 .76; 3 119 .4 2.6 6.3 

Davis 95 .70 88 .3 1.9 4.6 

Total 32.8 (9.9) 236.1 (71.1) 563.4 (168.9) 

1 Silt+clay and Ti02 weight percent values used in calculations. Ti02 values for unsampled basins are based on data from adjacent basins. 

2 Average weight percent Ti02 inn surface samples from basin; n, number of samples. 3 Basin area boundary is 200-m isobath except for Stellwagen basin (80-m isobath) and for Georges basin (300-m isobath). 4 Based on weight percent silt+clay (and its contained Ti02) values in surface sediment that are assumed to be constant with depth (except for 

Stellwagen basin) and on bulk density values of Wilkinson basin cores and of core KN 10-1 (Stellwagen basin) that vary with depth. 5 Deposit thickness. 

6 Values vary with depth. 

imported. The inferred amount of Ti02 in the basins is 

large, and the unconsolidated deposits lie in shallow water 

(<300m) and are relatively near the coast. No attempt has 

been made to beneficiate the fine-grained ore. 

The Bay of Fundy and surrounding region of New 

Brunswick and Nova Scotia are underlain by Carboniferous 

and Triassic basins that contain extensive exposures of red 

and gray clastic sedimentary rocks. These relatively soft 

rocks are a major present and Wisconsinan source of the 

fine-grained sediment in the Gulf of Maine basins. Silt- and 

clay-size rutile crystals are present in the Carboniferous and 

Triassic rocks, in the intertidal mud of the Bay of Fundy, 

and in the Gulf of Maine water column and bottom 

sediment. We suggest that the rutile formed authigenically 

in Bay of Fundy clastic sedimentary rocks after the dissolution of titanium-rich detrital minerals (ilmenite, ilmenomagnetite). Following glacial and postglacial erosion and 

transport, the rutile was deposited in the gulf basins. 

Additional sources of fine-grained, authigenic Ti02 during 

the Quaternary probably include sedimentary rocks of 

inferred Triassic age that underlie the Gulf of Maine; 

Ordovician, Silurian, and Devonian sandstones and shales 

in northern Maine and northwestern New Brunswick that 

also may be the source of rutile found in the fine-grained 

Presumpscot Formation of southern Maine; and reworked, 

coarse glacial debris (from all the foregoing sources) that is 

present in the Gulf of Maine, in New England, and in the 

Bay of Fundy region. 

Gulf of Maine I;pUd is comparable in Ti02 content to 

typical shale. The Cody Shale (Upper Cretaceous) of 

Wyoming contains 0.60 weight percent Ti02 , as well as 

small rutile crystals that resemble those found in Gulf of 

Maine sediment, in the Presumpscot Formation, and in the 

Bay of Fundy Carboniferous and Triassic clastics. The 

sequence of processes that includes authigenesis of Ti02 in 

coarse sedimentary rocks (especially arkose and graywacke), followed by erosion, segregation, and deposition 

(and recycling from shales) provides a model for interpreting the provenance of shales and for predicting and prospecting for unconsolidated deposits of fine-grained rutile. 

Plans for Integrated Airborne Geophysical Study 

of the Geophysics Environmental and Minerals 

Demonstration Area, South-Central Colorado 

Kenneth Watson, D.H. Knepper, R.N. Clark, j.A. Pitkin, 

V.F. Labson, D.L. Campbell, L.C. Rowan, F.A. Kruse, K. 

Lee, and E. Livo 

The Cripple Creek-Cannon City region of southcentral Colorado presents a wide range of geological and 

environmental problems that can be addressed by using 

airborne geophysics. The U.S. Geological Survey has 

recently established the Geophysics Environmental and 

Minerals (GEM) demonstration test area in Colorado for 

developing and testing geophysical techniques and data 

synthesis. The area contains the historic Cripple Creek gold 

district. The Cripple Creek gold deposits occur in hydrothermally altered Tertiary rocks, a well-exposed section of 

USGS Research on Mineral Resources-1989 Program and Abstracts 77 
Paleozoic sedimentary strata, a variety of Precambrian 

igneous and metamorphic rocks, gypsum deposits, a producing oil field, major geologic structures of Precambrian 

to Neogene age, and alkalic and carbonatite rocks. Because 

of normal faulting during the evolution of the Rio Grande 

rift zone, the area may have undiscovered mineral deposits 

on downdropped blocks that are now concealed by Tertiary 

sedimentary rocks and Quaternary alluvial materials. 

Available regional digital data sets covering the 

western half of the Pueblo 1° x 2° quadrangle will be 

assembled. These data sets include aeromagnetics, gravity, 

terrain, NURE (National Uranium Resource Evaluation) 

1-mi-spaced gamma-ray spectrometry and a variety of 

satellite data, including 80-m-resolution Landsat (Multispectral Scanner), 30-m-resolution TM (Thematic Mapper), 

1-km-resolution NOAA-AVHRR (Advanced Very High 

Resolution Radiometer), and 500-m-resolution HCMM 

(Heat Capacity Mapping Mission). In addition, detailed 

geologic maps available for the area will be prepared in 

digital form and integrated into the data base, together with 

the geochemical data proposed for environmental studies of 

the historically most active mine areas. Experimental airborne imaging spectrometer (A VIRIS, GERIS) and spectral 

thermal emission (TIMS) data have also been recently 

acquired of subareas within the GEM area as part of a 

cooperative study with NASA and the Center For Study of 

Earth From Space. 

Near-term data acquisition objectives include airborne VLF (Very Low Frequency) and experimental airborne EM using powerline fields, 114-mi airborne gammaray spectrometry, multispectral-multipolarization synthetic 

aperture radar, and airborne imaging spectrometry of 

selected targets within the GEM area. We also have made 

plans to accelerate acquisition of Digital Elevation Model 

(DEM) data for several 7I/2-minute quadrangles to provide 

complete coverage of the area for data integration and 

synthesis. 

Mineral Resource Assessment of the White 

Mountains National Recreation Area, EastCentral Alaska 

Florence R. Weber, Thomas D. Light, Richard B. 

McCammon, and C. Dean Rinehart 

The U.S. Geological Survey, the Alaska Division of 

Geological and Geophysical Surveys, and the U.S. Bureau 

of Mines conducted multidisciplinary interagency investigations to evaluate the potential for undiscovered mineral 

resources in the White Mountains National Recreation Area 

(WMNRA). east-central Alaska. Research by the U.S. 

Geological Survey focused on geologic mapping, reconnaissance geochemical and geophysical surveys. and the 

synthesis of all published information on mineral deposits in 

Table 1. Estimated number of undiscovered mineral 

resource deposits in the western three-fourths of the 

WMNRA [Weber and others abstract] 

Number of Probability 

Deposit type undiscovered deposits in 

percent 

Placer gold 1 or more 50 

2 or more 25 

3 or more 5 

Polymetallic veins 1 or more 50 

Tin greisen 1 or more 10 

U/Th/REE 1 or more 10 

Lode gold 1 or more 10 

Sedimentary exhalative 1 or more 10 

lead-zinc 

Tungsten skarn 1 or more 5 

the western three-fourths of the WMNRA. The results of 

these studies are critical to land-use planning decisions by 

the U.S. Bureau of Land Management. 

The White Mountains National Recreation Area is a 

part of the Yukon-Tanana Upland. This terrane consists 

primarily of quartzitic, pelitic, and calcic metasedimentary 

rocks and lesser metamorphosed mafic and felsic igneous 

rocks that have been intruded by Mesozoic and Cenozoic 

granitic rocks and minor amounts of intermediate and mafic 

rocks. The disruptive structures in the area are major thrust 

faults and strike-slip faults that are splays of the Tintina 

fault zone. 

We have made probabilistic estimates for the number 

of undiscovered deposits that occur within the western 

three-fourths of the WMNRA (table 1). Placer gold, the 

only commodity in the area that has been produced in 

significant amounts, ranks highest in probability. It has 

been recovered from Nome Creek and its tributaries since 

the tum of the century. The cumulative production to date is 

estimated to be 29,000 oz. 

By using the estimates, we have also estimated the 

mean undiscovered mineral resource endowment in the area 

studied for Au, Ag. Pb, Sn, Th, W, Zn, rare-earth oxides, 

and high-calcium limestone. We do not expect significant 

undiscovered resources of chromium, asbestos, nickel, or 

diamonds even though occurrences of these commodities 

have been reported in or near the study area. The recent 

report on the occurrence of platinum in gold samples in the 

nearby Tolovana mining district suggests platinum may be 

a potential metallic resource. 

Structural Control on Epithermal Gold Veins and 

Breccias in the Mesquite District, Southeastern 

California 

G.F. Willis, R.M. Tosdal, and S.L. Manske 

Gold in the Mesquite district, southeastern California. occurs in fault-related epithermal breccias. veins, and 

78 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Open pit at the Mesquite mine, Ariz., goldfields. 

fractures that cut Jurassic amphibolite facies orthogneiss 

and Cretaceous pegmatite. The host gneiss and orebodies 

are restricted to a block that is bounded on the north and 

south by westerly striking faults. The northern fault has 

dextral strike-slip offset of unknown magnitude; the southem fault does not crop out, and its presence is inferred from 

gravity data. Gold mineralization in this block occurs along 

three sets of anastomosing high-angle faults and related 

fractures. Northwesterly striking faults are the dominant 

set. Westerly striking and northerly striking faults are 

subordinate; the relative importance of the subordinate fault 

sets varies among the pits. Movement on the fau lt sets is 

broadly coeval because the fault sets are mutually crosscutting. Where preserved, slickensides on the mineralized 

faults are subhorizontal (0°-15° plunge), and kinematic 

indicators suggest that at least the northwesterly and westerly striking faults are dextral strike-slip faults. No kinematic information is available on the northerly striking 

faults. 

Gold mineralization along the faults and fractures 

accompanied the deposition of quartz and carbonate minerals from boiling, dilute fluids at relatively low temperatures 

(about 225 °C). Multiple episodes of brecciation and 

fine-scale chalcedonic banding in veins requires that mineralization accompanied repetitive faulting and fracturing. 

K-Ar dates on sericite suggest a mid-Tertiary age for the 

deposits. Mid- to late Tertiary clastic rocks containing rare 

mineralized clasts unconformably overlie the orebodies. 

Younger, unmineralized, strike- and normal-slip faults, 

marked by cohesive gouge, breccia, and clay, cut the gneiss 

and overlying clastic rocks, reactivated some of the mineralized structures, and partially dismembered the orebodies. 

The geometrical relations between mineralized faults 

on all scales and the kinematics of some of the faults 

indicate that dextral simple shear controlled districtwide 

vein emplacement. The northwesterly striking mineralized 

faults are analogous to the Riedel (synthetic) shears, and the 

northerly striking faults are analogous to the conjugate 

Riedel (antithetic) shears. The mineralization process was 

cyclical and was probably linked to episodic slip on the 

major strike-slip faults. The genesis of epithermal gold 

veins at Mesquite district is thus apparently related to the 

mid-Tertiary evolution of Cenozoic strike-slip fault systems 

in the region. 

USGS Research on Mineral Resources- 1989 Program and Abstracts 79 
Geology and Mineral Resources of the Port 

Moller Region, Western Alaska Peninsula, 

Aleutian Arc 

Frederic H. Wilson, Willis H. White , and Robert L. 

Detterman 

Geologic mapping of the Port Moller, Stepovak Bay, 

and Simeonof Island quadrangles was begun under the 

auspices of the Alaska Mineral Resource Assessment Program (AMRAP) in 1983 . Two important mineral deposits 

are located in the Port Moller quadrangle; the Pyramid 

prospect is the largest copper porphyry system in the 

Aleutian Arc, and the Apollo Mine is the only gold mine to 

reach production status in the Aleutian Arc. 

Geologic studies have shown a number of differences 

between the Port Moller region and other portions of the 

Alaska Peninsula. (1) In the Port Moller region, faulting is 

more prevalent than folding in contrast to elsewhere on the 

Alaska Peninsula. (2) Mesozoic rocks typical of the Alaska 

Peninsula are allochthonous and have been thrust from the 

southeast; rocks of the Port Moller region are autochthonous 

and have minor thrusting from the northwest. (3) Products 

of late Tertiary and Quaternary volcanism are more widespread. (4) A terrane boundary juxtaposes the Alaska 

Peninsula and Chugach tectonostratigraphic terranes. 

Throughout the south-central portion of the Port Moller 

quadrangle , late Miocene volcanic rocks are widespread; 

these rocks are uncommon elsewhere on the Peninsula, 

presumably due to erosion. South of these rocks on Popof, 

Unga, and Korovin Islands are extensive exposures of 

Oligocene volcanic rocks of the Meshik magmatic arc. 

We found that the Pyramid prospect is part of a 

northeast-trending belt of three shallow plutons and has 

associated hydrothermal alteration typical of porphyry copper systems on the mainland north of Unga Island. We also 

found a number of other shallow plutons that have similar 

alteration zones in the Port Moller region; the Kawisgag 

(Ivanof) prospect is the best known. The Apollo mine , on 

southeast Unga Island, produced from an epithermal gold 

vein system localized along a northeast-trending fracture 

system. Production was 3.3 million grams of gold; the bulk 

was produced between 1894 and 1906. 

Both Popof and southeastern Unga Islands are composed dominantly of volcanic rocks of the Popof volcanic 

View looki ng east of the Stillwater mmmg companies' platinum operation, Sti llwater River Valley, Mont. Th is is 

the Nation's only operating platinum deposit. 

80 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
rocks, a local name informally used for rocks correlated 

with the Meshik Formation, and sedimentary rocks of the 

Stepovak Formation. Radiometric dating of the volcanic 

rocks yields ages of approximately 35 to 30 Ma. On the 

basis of fossil determinations, the sedimentary rocks are of 

Oligocene age. Hydrothermal alteration and mineralization 

is more common in the Popof volcanic rocks of Unga and 

Popof Islands than in the otherwise similar Meshik volcanic 

rocks on the mainland. The major difference between the 

areas may be the presence of Alaska Peninsula terrane rocks 

beneath the volcanic rocks on the mainland and possible 

Chugach terrane rocks beneath the volcanic rocks on Unga 

and Popof Islands. Magma passing through the compositionally and structurally different basement rocks in the two 

areas should yield hydrothermal fluids of different compositions, which may explain the more abundant mineralization on Unga and Popof Islands. 

On the basis of historical records, industry reports to 

the Aleut Corporation, geologic mapping, and geochemical 

sampling, 117 mines, prospects, and occurrences have been 

catalogued in the Port Moller region. Epithermal gold vein 

systems and porphyry copper-type systems dominate; however, polymetallic vein and disseminated gold occurrences 

have also been found. In addition to U.S. Geological 

Survey geologic mapping and geochemical studies, largescale industry exploration sampling and drilling programs 

and detailed USGS studies of hydrothermal systems in the 

area are helping to characterize and model mineralized areas 

in the region. 

Precious-Metal Deposits in the Hailey and 

Western Idaho Falls 1 o x 2° Quadrangles, Idaho 

Ronald G. Worl, Earl H. Bennett, Falma J. Moye, and 

P.K. Link 

Field studies in support of the multidisciplinary Hailey Conterminous United States Mineral Assessment Program project show that precious-metal deposits occur in a 

variety of geologic terranes but that most are spatially 

related to northeast-trending faults that have probable 

Eocene displacement. 

The western part of the Hailey quadrangle is underlain by the Atlanta lobe of the Cretaceous Idaho batholith. 

Mineral deposits in this terrane are mainly veins and 

replacements that are found in faults and shear zones; these 

deposits contain precious metals and associated base metals. In the northwestern part of the Hailey quadrangle, 

epithermal precious-metal deposits of the Boise basin district are aligned along the northeast-trending trans-Challis 

fault system (TCFS). 

Within the Idaho batholith southeast of the TCFS, the 

most important epithermal precious- and base-metal deposits are located along northeast-trending structures parallel to 

the TCFS. Lesser deposits are located along northwesttrending basin-and-range structures. The association of 

Eocene rhyolite intrusions with the deposits appears to be 

important in some mining districts (Boise basin, Dixie, 

Neal) but not in others (Atlanta, Rocky Bar, Vienna). 

Numerous previously unmapped Tertiary dike swarms and 

plutons intrude the Cretaceous batholith in this area. Some 

of the mineralized shear zones have potential for low-grade 

disseminated deposits that might be amenable to heapleaching. 

In the eastern part of the Hailey quadrangle and the 

western part of the Idaho Falls quadrangle, allochthonous 

Paleozoic metasedimentary rocks are overlain by Eocene 

volcanic rocks and intruded by cogenetic Eocene plutons 

and dike swarms. Location of volcanic centers and 

emplacement of intrusive bodies were controlled by 

northeast-trending extensional structures. Both volcanichosted and sediment-hosted epithermal precious-metal 

deposits occur in this area. Volcanic-hosted deposits in the 

Lava Creek, Alder Creek, and Muldoon districts are in 

Challis Volcanics associated with late-stage rhyolite activity. These deposits are related to hot spring activity at the 

intersections of northeast- and northwest-trending structures. Potential for sediment-hosted deposits is indicated by 

anomalous Au, Ag, Sb, As, and Hg in rock, sage, and 

sediment samples spatially associated with jasperoid bodies 

located at or near the intersection of these northwest- and 

northeast-trending structures. Jasperoid bodies in the Timbered Dome, Grouse, Lehman Butte, and Barlett Point 

areas are replacements of Paleozoic calcareous and carbonaceous sedimentary rocks. 

In conclusion, areas having the best potential for 

undiscovered deposits are along highly sheared zones in 

Cretaceous and Tertiary intrusive rocks, at intersections of 

northeast- and northwest-trending systems in Challis volcanic rocks, and where northeast- or northwest-trending faults 

cut Paleozoic calcareous and carbonaceous sedimentary 

rocks. The potential is highest in the vicinity of intrusive 

rhyolites. 

As, Bi, Hg, S, Sb, and Te Geochemistry of the 

J-M Reef: Constraints on the Origin of Platinum 

Group Element-Enriched Sulfides in layered 

Intrusions 

M.L. Zientek, T.L. Fries, and R.M. Vian 

The J-M Reef is an interval of disseminated sulfides 

in the Lower Banded series of the Stillwater Complex that 

is enriched in the platinum group elements (PGE). Palladium and platinum occur in solid solution in base-metal 

sulfides and as discrete PGE minerals. These PGE minerals 

include sulfides, tellurides, arsenides, antimonides, bismuthinides, and PGE alloys with Fe, Sn, Hg, and Au. 

USGS Research on Mineral Resources-1989 Program and Abstracts 81 
fi. 

~"ff~ ' \ .. -

' 

·.·.:· :,.' :r~--~ ~ . . ;} ~. , '(; l" I' • 

' .. 

Disturbed cumulate layering below J-M Reef, Stillwater Complex, Mont. Disturbance possibly is related to the influx of 

new liquid and subsequent magma mixing that may have triggered the formation of the platinum-bearing zone. 

Several subpopulations that have distinctly different compositions based on whole rock compositional data (As, Bi, 

Cu, Hg, Pd, Pt, S, Sb, Te) can be delineated for samples 

collected from and adjacent to the J-M Reef. In general, 

samples from the reef have higher Pt:Cu, Pd:Cu, Pd:Pt, 

Te:Bi, and S:(Te + Bi) than those samples collected adjacent to the reef. Vertical profiles passing upsection from 

mineralized to barren rock through the reef suggest that 

Pd:Cu and Pt:Cu may decrease systematically. Most of the 

samples that have elevated arsenic, antimony, and tin 

abundances occur in samples collected adjacent to the reef, 

not within it , or in sulfide-poor rocks collected on the 

projection of the strike of higher grade areas of the reef. 

Te:Bi and As:Sb are controlled by mineralogy of the ores; 

variations in these ratios indicate that the relative proportions of the PGE minerals also change . 

Neither magma-mixing nor fluid-migration models 

readily explain why the minor quantities of sulfide minerals 

immediately adjacent to the sulfide-enriched layers that 

form the J-M Reef have different element ratios than the 

sulfide minerals that form the reef. If all sulfides formed by 

exsolution during a magma-mixing event and the modal 

proportion of sulfide now in the rocks are simply the result 

of mechanical processes that concentrated the sulfides into 

some layers and not others, then the composition of the 

sulfide would not be different. Models that rely upon 

ascending liquids or fluids are incompatible with the presence of sulfides that are not enriched in PGE immediately 

below or interlayered with the PGE-enriched sulfide layers. 

PGE-enriched postcumulus fluids should have reacted to the 

same extent with sulfides immediately outside the reef as 

within the reef. 

One explanation is that some of the sulfide minerals 

in the rocks outside the reef have a different origin than 

those that make up the reef. The sulfides that form the reef 

may represent "cumulus sulfides" that formed as the result 

of a magma-mixing event, achieved their high PGE contents at that time , and accumulated to form a layer. The 

rocks outside the reef may contain a large proportion of 

"postcumulus sulfides" that formed as the last dregs of 

intercumulus liquids trapped in the interstitial spaces 

between the cumulus grains reached sulfur saturation and 

exsolved a sulfide liquid or precipitated a sulfide mineral. 

The PGE contents of these sulfides would be expected to be 

82 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
less than the "cumulus sulfides" that form the reef because 

the "postcumulus sulfides" would have equilibrated with a 

much smaller volume of silicate liquid. An alternative 

explanation is that some of the sulfide droplets that formed 

as a result of the mixing event were trapped as inclusions in 

silicate minerals soon after formation. Entrapment in silicate minerals would reduce the amount of magma with 

which these sulfide droplets could equilibrate and effectively reduce their POE tenor. 

Active Deposition of Sediment-Hosted Massive 

Sulfide in the Escanaba Trough, Gorda Ridge 

Robert A. Zierenberg, J.M. Edmond, j.F. Grassle, A.C. 

Campbell, S.L. Ross, and W.C. Shanks Ill 

By using the submersible ALVIN (fig. 1), active 

hydrothermal vents have been located and sampled in the 

sediment-covered Escanaba trough along the spreading axis 

of the Gorda Ridge , offshore of northern California. The 

spreading center in the Escanaba trough is covered by up to 

500 m of hemipelagic and turbiditic sediment derived from 

the Columbia River drainage. Volcanic edifices, 1 to 3 km 

across, rise through and locally breach the sedimentary 

cover. Two volcanoes at the northern Escanaba (NESCA) 

and southern Escanaba (SESCA) sites (fig. 2) have been 

investigated by camera tows and submersible dives, and 

both have associated large areas of sediment-hosted sulfide 

mineralization. Several deposits have outcropping sulfide , 

from 3 to 15 m thick, exposed over traverses exceeding 100 

m, although none of the deposits has been fully mapped. 

The largest observed semicontinuous outcrop of massive 

sulfide is at least 500 m long and is within hundreds of 

meters of two other large, but incompletely explored, areas 

of outcropping massive sulfide. The occurrence of many 

large deposits in a limited area invites comparison to onland 

ore deposit districts. Samples recovered in sediment cores 

and exposures of massive sulfide on scarps indicate that 

some sulfide is deposited below the sediment-water interface, but the extent of subsurface sulfide is not known. 

Redistribution of sediment is common in the area and 

occurs by mass wasting from sediment scarps formed by 

tectonic and (or) volcanic uplift of sediment (fig. 3) and by 

active erosion of sediment on steep to gentle slopes. 

Erosional channels from 1 to more than 20 m deep, and up 

Figure 1. Research vessel ATLANTIS II and the deep submergence vehicle ALVIN , operated by the Woods Hole 

Oceanographic Institution , Woods Hole, Mass. [Zierenberg and others abstract] 

USGS Research on Mineral Resources- 1989 Program and Abstracts 83 
Figure 2. Map of Escanaba trough showing location of 

the volcanic done complexes. The location of the SESCA 

(S) and NESCA (N) areas and DSDP site 35 are shown. 

[Zierenberg and others abstract] 

to tens of meters wide , generally expose unlithified sediment, and occasionally massive sulfide, along the steepest 

walls. 

The known sulfide deposits are entirely hosted by 

sediment. Deposits span the evolutionary range from old 

oxidizing and eroding deposits to those still actively forming. Pyrrhotite forms the bulk of the deposits and is 

associated with minor amounts of sphalerite, barite, marcasite , isocubanite, and galena and trace amounts of chalcopyrite, arsenopyrite , loellingite (FeAs2) , tennantitetetrahedrite, and alabandite (MnS). Interaction of the 

hydrothermal fluid and sediment enriches the deposits in 

Ag , As, Bi , Pb, Sb, and Sn relative to sulfides formed 

directly on oceanic basalt. Some samples contain hydrocarbon formed by hydrothermal alteration of organic matter in 

the sediment. 

The ALVIN dives concentrated on the area of the 

NESCA site (fig. 2) around a volcanic edifice near latitude 

HYDROTHERMAL 

DEPOSITS 

Figure 3. Schematic diagram (adapted from Lonsdale 

and Lawver, 1980) showing the relation of hydrothermal 

deposits to the sediment-capped hills and a possible 

mechanism for uplift of the sediment by intrusion. 

[Zierenberg and others abstract] 

41° N., longitude 127° 29' W. and provided the first direct 

observations of active hydrothermal discharge in the Escanaba trough. The active deposits observed are mounds of 

brecciated and massive pyrrhotite-rich sulfide a few meters 

to more than 20 m high and tens of meters across, topped by 

porous chimneys leaking clear hydrothermal fluid . The 

active chimneys are predominantly anhydrite and barite. 

The maximum stable temperature measured by using the 

ALVIN temperature probe was 219 °C. The fluid pH is 

slightly lower, and the alkalinity is higher than those of 

seawater; these differences suggest that the clear fluids are 

evolved hydrothermal fluids that have deposited their dissolved metal load in the subsurface. 

Vent specific fauna were observed on several hydrothermal mounds. Thin tube worms that appear similar to 

those recovered from the Juan de Fuca Ridge are common 

and are associated with white anemones that have blood-red 

tentacles. Palm worms found near higher temperature vents 

are morphologically similar to Juan de Fuca varieties but are 

green orange rather than purple in color. Small limpets and 

snails are abundant. Weakly active hydrothermal mounds 

are covered by bacterial mats. Elongate bivalves up to 20 

em long are locally abundant in sediment-covered areas 

near hydrothermal deposits. 

REFERENCE 

Lonsdale, P. , and Lawver, L.A., 1980 , Immature plate boundary 

zones studied with a submersible in the Gulf of California, 

Geological Society of America Bulletin, v. 91 , p. 555-569. 

84 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Names, Addresses, and Telephone Numbers of Contributing Authors 

Raymond E. Arndt 

U.S. Geological Survey 

920 National Center 

Reston, VA 22092 

(703) 648-6198 

Philip J. Aruscavage 

U.S. Geological Survey 

923 National Center 

Reston, VA 22092 

(703) 648-6226 

Rosemary A. Askin 

Department of Earth Sciences 

University of California-Riverside 

Riverside, CA 92521 

(714) 777-4420 

Judy M. Back 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6459 

William C. Bagby 

U.S. Geological Survey 

913 National Center 

Reston, VA 22092 

(703) 648-4242 

G. Bryan Bailey 

U.S. Geological Survey 

EROS Data Center 

Sioux Falls, SD 57198 

(605) 594-6001 

Viki Bankey 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1348 

Harlan Barton 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-2443 

David W. Beaty 

Chevron Oil Field Research Co. 

P.O. Box 446 

La Habra. CA 90633--0446 

(213) 694-7653 

Harvey E. Belkin 

U.S. Geological Survey 

959 National Center 

Reston, VA 22092 

(703) 648-6162 

Earl H. Bennett 

Idaho Geological Survey 

Morrill Hall, Room 332 

University of Idaho 

Moscow, ID 83843 

(208) 885-7991 

Byron R. Berger 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1800 

Keith H. Bettles 

Barrick Goldstrike Mines, Inc. 

Elko, NV 89801 

(702) 738-2828 

Donald J. Birak 

Freeport McMoRan Gold Company 

Elko, NV 8980 1 

(702) 758-9221 

Robert J. Bisdorf 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1377 

Richard J. Blakely 

U.S. Geological Survey 

MS 989 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5316 

James D. Bliss 

U.S. Geological Survey 

210 East 7th Street 

Tuscon, AZ 85705 

(602) 624-8577 

Robin M. Bouse 

University of Arizona 

Department of Geosciences 

Tuscon, AZ 85721 

(602) 621-6002 

Robert E. Bracken 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1207 

David A. Brew 

U.S. Geological Survey 

MS 904 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5726 

David L. Brickey 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6354 

Robert D. Brown, Jr. 

U.S. Bureau of Mines 

2401 E Street, N.W. 

Washington, D.C. 20241 

(202) 634-4678 

Thomas K. Bundtzen 

Alaska Division of Geological 

and Geophysical Surveys 

Fairbanks, AK 99701 

(907) 474-7147 

Andrew C. Campbell 

Department of Earth, Atmospheric 

and Planetary Sciences 

Massachusetts Institute 

of Technology 

Cambridge, MA 02139 

(617) 253-5790 

David L. Campbell 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1323 

William F. Cannon 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6345 

Carl Carlson 

U.S. Geological Survey 

210 East 7th Street 

Tuscon, AZ 85705 

(602) 624-8578 

USGS Research on Mineral Resources-1989 Program and Abstracts 85 
Names, Addresses, and Telephone Numbers of Contributing Authors 

James E. Case 

U.S. Geological Survey 

MS 989 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5305 

Duane E. Champion 

U.S. Geological Survey 

MS 937 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-4671 

Val W. Chandler 

Minnesota Geological Survey 

2642 University Avenue 

St. Paul, MN 55114 

(612) 627-4801 

E.C.T. Chao 

U.S. Geological Survey 

929 National Center 

Reston, VA 22092 

(703) 648-6460 

Barbara Chazin 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1196 

Charles W. Clark 

FMC Paradise Peak Corp. 

Box 1237 

Hawthorne, NV 89415 

(702) 285-0060 

Roger N. Clark 

U.S. Geological Survey 

MS 954 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1332 

Judith A. Commeau 

U.S. Geological Survey 

Quissett Campus, Building B 

Woods Hole, MA 02543 

(508) 548-8700 

James E. Conrad 

U.S. Geological Survey 

MS 941 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5402 

Theresa M. Cookro 

U.S. Geological Survey 

MS 937 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5706 

Dennis P. Cox 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5364 

Robert E. Criss 

Department of Geology 

University of California 

Davis, CA 95616 

(916) 752-8581 

Charles G. Cunningham 

U.S. Geological Survey 

959 National Center 

Reston, VA 22092 

(703) 648-6121 

Gerald K. Czamanske 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5373 

Arthur R. Dahl 

Freeport McMoRan Gold Company 

Elko, NV 89801 

(702) 758-9221 

William E. Daly 

Freeport McMoRan Gold Company 

Elko, NV 89801 

(702) 758-9221 

Warren C. Day 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-6483 

Marilyn L. DeRosa 

U.S. Geological Survey 

MS 999 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 354-3196 

Robert L. Detterman 

U.S. Geological Survey 

345 Middlefield Road 

Menlo Park, CA 94025 

86 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 

John C. Dohrenwend 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5432 

Lawrence J. Drew 

U.S. Geological Survey 

920 National Center 

Reston, VA 22092 

(703) 648-6483 

M. Drucker 

Foreign Service Officer 

U.S. Department of State 

Washington, D.C. 20520 

John L. Dwyer 

U.S. Geological Survey 

EROS Data Center 

Sioux Falls, SD 57198 

(605) 594-6060 

John M. Edmond 

Department of Earth, Atmospheric 

and Planetary Sciences 

Massachusetts Institute 

of Technology 

Cambridge, MA 02139 

(617) 253-5790 

Cheryl A. Edwards 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6305 

Barbara A. Eiswerth 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6379 

James E. Elliott 

U.S. Geological Survey 

MS 930 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5650 

James A. Erdman 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5512 
Names, Addresses, and Telephone Numbers of Contributing Authors 

M. Suzanne Erickson 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-2497 

Ralph L. Erickson 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5527 

Pow-Foong Fan 

Geology and Geophysics 

University of Hawaii 

Honolulu, HI 96822 

(808) 948-7748 

Robin G. Fegeas 

U.S. Geological Survey 

521 National Center 

Reston, VA 22092 

(703) 648-4511 

Larry D. Fellows 

State Geologist 

Arizona Geological Survey 

845 North Park A venue 

Tuscan, AZ 85719 

(602) 621-7906 

Lorraine H. Filipek 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1800 

Robert B. Finkelman 

U.S. Geological Survey 

956 National Center 

Reston, VA 22092 

(703) 648-6412 

Eugene E. Foord 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-4755 

Michael P. Foose 

U.S. Geological Survey 

913 National Center 

Reston, VA 22092 

(703) 648-6113 

Terry L. Fries 

U.S. Geological Survey 

MS 938 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5281 

David Frishman 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1536 

A.J. Froelich 

U.S. Geological Survey 

926 National Center 

Reston, VA 22092 

(703) 648-6950 

H. Kit Fuller 

U.S. Geological Survey 

907 National Center 

Reston, VA 22092 

(703) 648-4381 

Bruce M. Gamble 

U.S. Geological Survey 

Branch of Alaska Geology 

4200 University Drive 

Anchorage, AK 99508-4667 

(907) 561-1181 

John W. Geissman 

Department of Geology 

and Geophysics 

University of New Mexico 

Albuquerque, NM 87131 

(505) 277-2644 

Carol N. Gerlitz 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5602 

David A. Giles 

Lac ana Gold Inc. 

Reno, NV 89510 

(702) 329-5609 

Martin Goldhaber 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1521 

David Gottfried 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6310 

J.F. Grassle 

Woods Hole Oceanographic 

Institution 

Woods Hole, MA 02543 

(617) 548-1400 

Richard I. Grauch 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5551 

V .J .S Grauch 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1393 

Alan Green 

Geological Survey of Canada 

1 Observatory Crescent, Bldg. 7 

Ottawa, Ontario, Canada KlA OY3 

(613) 995-5490 

Andrew E. Grosz 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6314 

Donald J. Grybeck 

U.S. Geological Survey 

Branch of Alaska Geology 

4200 University Drive 

Anchorage, AK 99508-4667 

(907) 786-7403 

Jane M. Hammarstrom 

U.S. Geological Survey 

959 National Center 

Reston, VA 22092 

(703) 648-6165 

Richard H. Hammond 

South Dakota Geological Survey 

Science Center, USD 

Vermillion, SD 57069 

(605) 677-6167 

USGS Research on Mineral Resources-1989 Program and Abstracts 87 
Names, Addresses, and Telephone Numbers of Contributing Authors 

John Hand 

Utah Geological and Mineral Survey 

606 Black Hawk Way 

Salt Lake City, UT 84108-1280 

(801) 581-6831 

Judith L. Hannah 

University of Vermont 

Burlington, VT 05405-0122 

(802) 656-0245 

Richard F. Hardyman 

U.S. Geological Survey 

Mackay School of Mines 

University of Nevada-Reno 

Reno, NV 89557-0047 

(702) 784-1766 

Anita G. Harris 

U.S. Geological Survey 

970 National Center 

Reston, VA 22092 

(703) 648-5201 

J .E. Harrison 

U.S. Geological Survey 

MS913 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1251 

Timothy S. Hayes 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-6482 

James R. Hein 

U.S. Geological Survey 

MS 999 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 354-3150 

Richard W. Henley 

Epithermax, Inc. 

#4 J uad Place 

Aranda, A.C.T. 

2614 Australia 

Margaret E. Hinkle 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1193 

Albert H. Hofstra 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5530 

Donald B. Hoover 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1326 

Delmont M. Hopkins 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1908 

Mary F. Horan 

U.S. Geological Survey 

981 National Center 

Reston, VA 22092 

(703) 648-5347 

Robert J. Horton 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1338 

StephenS. Howe 

U.S. Geological Survey 

MS 941 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5444 

Donald F. Huber 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5358 

Robert C. Jachens 

U.S. Geological Survey 

MS 989 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5300 

88 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 

Jane Jenness 

Main Interior Building-Room 2647 

18th and C Streets, N.W. 

Washington, D.C. 20240 

(202) 343-5512 

David A. John 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5424 

John E. Jones 

U.S. Geological Survey 

521 National Center 

Reston, VA 22092 

(703) 648-4138 

Michael B. Jones 

Freeport McMoRan Gold Company 

Elko, NV 89801 

(702) 758-9221 

Oliver D. Jones 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6359 

Wang Junwen 

Institute of Geochemistry, 

Academia Sinica 

Guiyang, Peoples Republic of China 

Jung-Keuk Kang 

Korea Ocean Research and 

Development Institute 

An san 

P.O. Box 29 

Seoul, 425-600 Korea 

Terry E.C. Keith 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5201 

Richard P. Keller 

Rice University 

Geology and Geophysics Laboratory 

P.O. Box 1892 

Houston, TX 77251 

(713) 527-4067 
Names, Addresses, and Telephone Numbers of Contributing Authors 

Herbert Kirschenbaum 

U.S. Geological Survey 

923 National Center 

Reston, VA 22092 

(703) 648-6243 

Eva B. Kisvarsanyi 

Missouri Department 

of Natural Resources 

P.O. Box 250 

Rolla, MO 65401 

(314) 364-1752 

Douglas P. Klein 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1313 

Terry L. Klein 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6339 

M. Dean Kleinkopf 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1412 

Daniel H. Knepper 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1386 

Robert P. Koeppen 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6340 

Randolph A. Koski 

U.S. Geological Survey 

MS 999 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 354-3208 

Allan N. Kover 

U.S. Geological Survey 

519 National Center 

Reston, VA 22092 

(703) 648-6370 

M. Dennis Krohn 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6371 

Fred A. Kruse 

CSES/CIRES 

University of Colorado 

Boulder, CO 80309-0449 

(303) 492-6880 

Robert P. Kucks 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1405 

Victor F. Labson 

U.S. Geological Survey 

MS 964 

Box 25046. Denver Federal Center 

Denver, CO 80225 

(303) 236-1312 

Gary P. Landis 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5609 

Candice M. Lane-Bostwick 

U.S. Geological Survey 

Quissett Campus, Building B 

Woods Hole, MA 02543 

(508) 548-8700 

Keenan Lee 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1375 

Joel Leventhal 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1522 

Lee H. Liberty 

U.S. Geological Survey 

922 National Center 

Reston, VA 22092 

(703) 648-6797 

R. Thomas Lierman 

Department of Geology 

Morehead State University 

UPO Box 706 

Morehead, KY 40351 

(606) 783-2166 

Thomas D. Light 

U.S. Geological Survey 

Branch of Alaska Geology 

4200 University Drive 

Anchorage, AK 99508--4667 

(907) 561-1181 

PaulK. Link 

Department of Geology 

Idaho State University 

Pocatello, ID 83209-0009 

(208) 236-3846 

Eric Livo 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1207 

Tom G. Lovering 

U.S. Geological Survey 

MS 908 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5528 

Steve Ludington 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5371 

Dawn J. Madden-McGuire 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1856 

Frank T. Manheim 

U.S. Geological Survey 

Quissett Campus, Building B 

Woods Hole, MA 02543 

(508) 548-8700 

Scott L. Manske 

Department of Geology 

Stanford University 

Stanford, CA 94305 

(415) 329-5423 

USGS Research on Mineral Resources-1989 Program and Abstracts 89 
Names, Addresses, and Telephone Numbers of Contributing Authors 

Susan M. Marcus 

U.S. Geological Survey 

913 National Center 

Reston, VA 22092 

(703) 648-6116 

Sherman P. Marsh 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5521 

Richard B. McCammon 

U.S. Geological Survey 

920 National Center 

Reston, VA 22092 

(703) 648-6150 

J. Howard McCarthy, Jr. 

U.S. Geological Survey 

Mackay School of Mines 

University of Nevada-Reno 

Reno, NV 89557--0047 

(702) 784-1765 

John B. McHugh 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1908 

Edwin H. McKee 

U.S. Geological Survey 

MS 941 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5477 

Michael G. Medberry 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1398 

Christopher M. Menges 

650 Gene A venue NW 

Albuquerque, NM 87107 

William R. Miller 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5558 

Nancy M. Milton 

U.S. Geological Survey 

Mackay School of Mines 

University of Nevada-Reno 

Reno, NV 89557--0047 

(702) 784-4313 

Jean A. Minkin 

U.S. Geological Survey 

929 National Center 

Reston, VA 22092 

(703) 648-6461 

Stanton H. Moll 

U.S. Geological Survey 

EROS Data Center 

Sioux Falls, SD 57198 

(605) 594-6056 

Bruce F. Molnia 

U.S. Geological Survey 

917 National Center 

Reston, VA 22092 

(703) 648-4120 

Barry C. Moring 

U.S. Geological Survey 

MS 941 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5360 

Elwin L. Mosier 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-2461 

David A. Mouat 

U.S. Geological Survey 

Mackay School of Mines 

University of Nevada-Reno 

Reno, NV 89557--0047 

(702) 784-4313 

Falma J. Moye 

Department of Geology 

Idaho State University 

Pocatello, ID 83209--0009 

(208) 236-3549 

Charles W. Naeser 

U.S. Geological Survey 

MS 963 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-4 720 

90 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 

Rainer J. Newberry 

Department of Geology 

University of Alaska 

Fairbanks, AK 99775--0760 

(907) 4 7 4-6895 

Suzanne W. Nicholson 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6344 

Warren J. Nokleberg 

U.S. Geological Survey 

MS 904 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5732 

Constance J. N ott 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1562 

Patrick M. Okita 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6338 

John S. Oldow 

Rice University 

Geology and Geophysics Laboratory 

P.O. Box 1892 

Houston, TX 77251 

(713) 527-4067 

Greta J. Orris 

U.S. Geological Survey 

210 East 7th Street 

Tuscon, AZ 85705 

(602) 624-8577 

Robert L. Oscarson 

U.S. Geological Survey 

MS 916 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5117 

James P. Owens 

U.S. Geological Survey 

926 National Center 

Reston, VA 22092 

(703) 648-6911 
Names, Addresses, and Telephone Numbers of Contributing Authors 

James R. Palmer 

Missouri Department of 

Natural Resources 

P.O. Box 250 

Rolla, MO 65401 

(314) 364-1752 

Robert C. Pearson 

U.S. Geological Survey 

MS 930 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5652 

Jeffrey D. Phillips 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6375 

John A. Philpotts 

U.S. Geological Survey 

923 National Center 

Reston, VA 22092 

(703) 648-6297 

James A. Pitkin 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1334 

Joseph L. Plesha 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1398 

Geoffrey S. Plumlee 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-9224 

Melvin H. Podwysocki 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6376 

Walden P. Pratt 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5598 

Meng Qingrun 

Tianjin Geological Academy of the 

Ministry of Metallurgical Industry 

42 Y ouyi Road 

Tianjin, Peoples Republic of China 

Norma Rait 

U.S. Geological Survey 

923 National Center 

Reston, VA 22092 

(703) 648-6233 

William H. Raymond 

U.S. Geological Survey 

MS 921 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5622 

Carl B. Rexroad 

Indiana Geological Survey 

611 North Walnut Grove 

Bloomington, IN 47405 

(812) 335-1350 

C. Dean Rinehart 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5422 

Gilpin R. Robinson, Jr. 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6333 

Stephanie L. Ross 

U.S. Geological Survey 

MS 999 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 354-3070 

Hedy J. Rossmeissl 

U.S. Geological Survey 

510 National Center 

Reston, VA 22092 

(703) 648--4591 

Lawrence C. Rowan 

U.S. Geological Survey 

927 National Center 

Reston, VA 22092 

(703) 648-6381 

Robert D. Rugg 

Dept. of Urban Studies and Planning 

Virginia Commonwealth University 

Richmond, VA 23284-2008 

(804) 367-1134 

Robert 0. Rye 

U.S. Geological Survey 

MS 963 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-7882 

James J. Rytuba 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5418 

Jay A. Sampson 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1350 

E. Sandoval 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1404 

Don L. Sawatzky 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1387 

Jeanine M. Schmidt 

U.S. Geological Survey 

Branch of Alaska Geology 

4200 University Drive 

Anchorage, AK 99508--4667 

(907) 561-1181 

Paul G. Schruben 

U.S. Geological Survey 

920 National Center 

Reston, VA 22092 

(703) 648-6142 

Klaus J. Schulz 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6335 

USGS Research on Mineral Resources-1989 Program and Abstracts 91 
Names, Addresses, and Telephone Numbers of Contributing Authors 

Marjorie S. Schulz 

U.S. Geological Survey 

MS 999 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 354-3151 

Steven D. Scott 

Department of Geology 

University of Toronto 

Toronto, Ontario 

M5S 1A1, Canada 

(416) 978-5424 

Dale R. Setterholm 

Minnesota Geological Survey 

2642 University Avenue 

St. Paul, MN 55114-1057 

(612) 627-4780 

Wayne C. Shanks III 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6336 

Maureen G. Sherlock 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5414 

Michael A. Shubat 

Utah Geological and Mineral Survey 

606 Black Hawk Way 

Salt Lake City, UT 84108-1280 

(801) 581-6831 

Miles L. Silberman 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5511 

PaulK. Sims 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5621 

Donald A. Singer 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5370 

John F. Slack 

U.S. Geological Survey 

954 National Center 

Reston, VA 22092 

(703) 648-6337 

Bruce D. Smith 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1399 

Thomas E. Smith 

Alaska Division of Geological 

and Geophysical Surveys 

Fairbanks, AK 99701 

(907) 474-7147 

Joseph P. Smoot 

U.S. Geological Survey 

926 National Center 

Reston, VA 22092 

(703) 648-6906 

Lawrence W. Snee 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5619 

David L. Southwick 

Minnesota Geological Survey 

2642 University Avenue 

St. Paul, MN 55114-1057 

(612) 627-4780 

Holly J. Stein 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5592 

Thomas A. Steven 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5613 

David B. Stewart 

U.S. Geological Survey 

959 National Center 

Reston, VA 22092 

(703) 648-6945 

92 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 

Douglas B. Stoeser 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-9817 

Mitsunobu Tatsumoto 

U.S. Geological Survey 

MS 963 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-7886 

Paul K. Theobald 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1853 

Ted G. Theodore 

U.S. Geological Survey 

MS 984 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5365 

Robert E. Thomason 

FMC Gold Co. 

Reno, NV 89502 

(702) 827-3777 

Charles H. Thorman 

U.S. Geological Survey 

MS 905 

Box 25046. Denver Federal Center 

Denver, CO 80225 

(303) 236-5601 

Ronald R. Tidball 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5517 

Joe Tingley 

Nevada Bureau of Mines 

and Geology 

University of Nevada 

Reno, NV 89557 

(702) 784-6691 
Names, Addresses, and Telephone Numbers of Contributing Authors 

Edwin W. Tooker 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5419 

Richard M. Tosdal 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5423 

Charles M. Trautwein 

U.S. Geological Survey 

EROS Data Center 

Sioux Falls, SD 57198 

(605) 594-6015 

Brent D. Turrin 

U.S. Geological Survey 

MS 941 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5441 

John D. Unger 

U.S. Geological Survey 

922 National Center 

Reston, VA 22092 

(703) 648-6790 

Page C. Valentine 

U.S. Geological Survey 

Quissett, Campus, Building B 

Woods Hole, MA 02543 

(508) 548-8700 

Richard W. Vian 

Stillwater Mining Company 

Star Route 2, Box 365 

Nye, MT 59061 

(406) 438-6208 

C.A. Wallace 

U.S. Geological Survey 

MS 913 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1238 

K. Wang 

Institute of Geology 

Academia Sinica 

Beijung, Peoples Republic of China 

Kenneth Watson 

U.S. Geological Survey 

MS 964 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1324 

Kenneth C. Watts, Jr. 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-8101 

Florence R. Weber 

U.S. Geological Survey 

P.O. Box 80586 

Fairbanks, AK 99708 

(907) 474-7245 

Sun Weijun 

Tianjin Geological Academy of the 

Ministry of Metallurgical Industry 

42 Y ouyi Road 

Tianjin, Peoples Republic of China 

Willis H. White 

U.S. Geological Survey 

Branch of Alaska Geology 

4200 University Drive 

Anchorage, AK 99508-4667 

(907) 786-7435 

Helen Whitney 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1190 

Gerald F. Willis 

Gold Fields Operating 

Company-Mesquite 

HCR 76 Glamis 100 

Brawley, CA 92227 

(619) 352-6541 

Frederic H. Wilson 

U.S. Geological Survey 

Branch of Alaska Geology 

4200 University Drive 

Anchorage, AK 99508-4667 

(907) 561-1181 

Ronald G. Worl 

U.S. Geological Survey 

MS 905 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-5603 

Bruce E. Wright 

U.S. Geological Survey 

521 National Center 

Reston, VA 22092 

(703) 648-4528 

Ren Yingzhen 

Tianjin Geological Academy of the 

Ministry of Metallurgical Industry 

42 Y ouyi Road 

Tianjin, Peoples Republic of China 

Wang Zhifen 

China National Nonferrous Metals 

Corporation 

Southwest Exploration Corporation 

Kunming, Yunnan, Peoples Republic of China 

Michael L. Zientek 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5445 

Robert A. Zierenberg 

U.S. Geological Survey 

MS 901 

345 Middlefield Road 

Menlo Park, CA 94025 

(415) 329-5437 

David R. Zimbelman 

U.S. Geological Survey 

MS 973 

Box 25046, Denver Federal Center 

Denver, CO 80225 

(303) 236-1863 

USGS Research on Mineral Resources-1989 Program and Abstracts 93 
ORGANIZATION OF THE U.S. GEOLOGICAL SURVEY 

Office Name Telephone City 

OFFICE OF THE DIRECTOR 

Director Dallas L. Peck (703) 648-7411 Reston 

Associate Director Doyle G. Frederick (703) 648-7412 Reston 

Assistant Director for Research Bruce R. Doe (703) 648-4450 Reston 

Assistant Director for Engineering Geology James F. Devine (703) 648-4423 Reston 

Assistant Director for Administration Jack J. Stassi (703) 648-7200 Reston 

Assistant Director for Programs Peter F. Bermel (703) 648-4430 Reston 

Assistant Director for Intergovernmental Affairs John J. Dragonetti (703) 648-4427 Reston 

Assistant Director for Information Systems James E. Biesecker (703) 648-7108 Reston 

Chief, Public Affairs Office Donovan B. Kelly (703) 648-4459 Reston 

National Mapping Division 

Chief Lowell E. Starr (703) 648-5748 Reston 

Geologic Division 

Chief Geologist Benjamin A. Morgan (703) 648-6600 Reston 

Water Resources Division 

Chief Hydrologist Philip Cohen (703) 648-5215 Reston 

ORGANIZATION OF THE GEOLOGIC DIVISION 

Office of the Chief Geologist 

Chief Geologist Benjamin A. Morgan (703) 648-6600 Reston 

Associate Chief Geologist William R. Greenwood (703) 648-6601 Reston 

Assistant Chief Geologist for Programs David P. Russ (703) 648-6640 Reston 

Assistant Chief Geologist, Eastern Region Jack H. Medlin (703) 648-6660 Reston 

Assistant Chief Geologist, Central Region Harry A. Tourtelot (303) 236-5438 Denver 

Assistant Chief Geologist, Western Region William R. Normark (415) 329-5101 Menlo Park 

Office of Mineral Resources 

Chief Glenn H. Allcott (703) 648-6100 Reston 

Chief, Branch of Alaskan Geology Donald J. Grybeck (907) 786-7403 Anchorage 

Chief, Branch of Eastern Mineral Resources Bruce R. Lipin (703) 648-6327 Reston 

Chief, Branch of Central Mineral Resources David A. Lindsey (303) 236-5568 Denver 

Chief, Branch of Western Mineral Resources Edwin H. McKee (415) 329-5477 Menlo Park 

Chief, Branch of Geochemistry Lorraine H. Filipek (303) 236-1800 Denver 

Chief, Branch of Resource Analysis William D. Menzie (703) 648-6125 Reston 

Chief, Branch of Geophysics Thomas G. Hildenbrand (303) 236-1212 Denver 

Office of Energy and Marine Geology 

Chief Gary W. Hill (703) 648-6472 Reston 

Chief, Branch of Petroleum Geology Donald L. Gautier (303) 236-5711 Denver 

Chief, Branch of Coal Geology Harold J. Gluskoter (703) 648-6401 Reston 

Chief, Branch of Sedimentary Processes Walter E. Dean, Jr. (303) 236-1644 Denver 

Chief, Branch of Pacific Marine Geology Monty A. Hampton (415) 329-3184 Menlo Park 

Chief, Branch of Atlantic Marine Geology Robert B. Halley (617) 837-4211 Woods Hole 

Office of Regional Geology 

Chief Mitchell Reynolds (703) 648-6960 Reston 

Chief, Branch of Eastern Regional Geology John F. Sutter (703) 648-6900 Reston 

Chief, Branch of Central Regional Geology Glen A. Izett (303) 236-1258 Denver 

Chief. Branch of Western Regional Geology Rowland W. Tabor (415) 329-4909 Menlo Park 

Chief, Branch of Isotope Geology Carl E. Hedge (303) 236-7880 Denver 

Chief, Branch of Astrogeology Hugh H. Kieffer (602) 765-7015 Flagstaff 

Chief. Branch of Paleontology and Stratigraphy Richard Z. Poore (703) 648-5288 Reston 

94 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Office 

Office of Earthquakes, Volcanoes, and Engineering 

Chief 

Chief, Branch of Engineering Seismology 

and Geology 

Chief, Branch of Global Seismology 

and Geomagnetism 

Chief, Branch of Seismology 

Chief, Branch of Geologic Risk Assessment 

Chief, Branch of Tectonophysics 

Chief, Branch of Igneous and Geothermal Processes 

Office of Scientific Publications 

Chief 

Chief, Branch of Eastern Technical Reports 

Chief, Branch of Central Technical Reports 

Chief, Branch of Western Technical Reports 

Chief, Library and Information Services 

Office of International Geology 

Chief 

U.S. Geological Survey 

National Center 

Reston , VA 22092 

U.S. Geolog ical Survey 

4200 Un ive rsity Drive 

Anchorage, AK 99508-4667 

Name 

Robert L. Wesson 

Thomas C. Hanks 

Robert P. Masse 

William H. Bakun 

Kaye M. Shedlock 

Wayne R. Thatcher 

Robert L. Christiansen 

John M. Aaron 

Simon M . Cargill 

Lawrence F. Rooney 

Jim B. Pinkerton 

Barbara Chappel l 

A. Thomas Overshi ne 

Addresses 

U.S . Geological Survey 

Box 25046 

Denver Federa l Center 

Denver, CO 80225 

U.S. Geological Survey 

2255 N. Gemini Drive 

Flagstaff, AZ 86001 

Telephone City 

(703) 648-6714 Reston 

(4 15) 329-5634 Menlo Park 

(303) 236-1510 Denver 

(4 15) 329-4793 Menlo Park 

(303) 236- 1585 Denver 

(4 15) 329-4810 Menlo Park 

(4 15) 329-5228 Menlo Park 

(703) 648-6077 Reston 

(703) 648-6 147 Reston 

(303) 236-5457 Denver 

(4 15) 329-5043 Menlo Park 

(703) 648-4305 Reston 

(703) 648-6047 Reston 

U.S. Geological Survey 

345 Middlefield Road 

Menlo Park, CA 94025 

U.S. Geo logical Survey 

Qui·ssett Campus 

Buil ding B 

Woods Hole, MA 02543 

Exploratory drilling in the upper part of the Stillwater Complex, Mont. 

USGS Research on Mineral Resources-1989 Program and Abstracts 95 
INDEX OF AUTHORS 

A E 

Arndt, R.E ............................................................... 43 Edmond, J.M ............................................................ 83 

Aruscavage, P.J .................................................... 23, 39 Edwards, C.A ............................................................ 8 

Askin, R.A .............................................................. 28 Eiswerth, B.A ........................................................... 15 

Elliott, J.E ..................................................... 16, 19,47 

8 Erdman, J .A ............................................................. 45 

Back, J.M ................................................................. 8 Erickson, M.S ........................................................... 17 

Bailey, G.B ............................................................... ! Erickson, R.L ........................................................... 17 

Bankey, V ....................................................... l, 67, 70 

Barton, H .................................................................. 2 F 

Beaty, D.W ............................................................... 4 Fan, P.-F ................................................................. 53 

Belkin, H.E ............................................................... 4 Fegeas, R.G ............................................................. 17 

Bennett, E.H ............................................................ 81 Fellows, L.D ............................................................ 75 

Berger, B.R ............................................................. 10 Finkelman, R.B ......................................................... 18 

Bettles, K.H ............................................................. 45 Foord, E.E ............................................................... 19 

Birak, D. J ............................................................... 30 Fries, T.L ................................................................ 81 

Bisdorf, R.J ............................................................. 67 Frishman, D ............................................................. 19 

Blakely, R.J ................................................... 10, 14, 35 

Bliss, J.D ................................................................ 27 

Froelich, A.J ............................................................ 23 

Fuller, H.K .............................................................. 19 

Bouse, R.M ............................................................. 41 

Bracken, R.E ....................................................... 33, 67 

Brew, D.A ............................................................... 48 

Brickey, D.L ............................................................ 70 

Brown, R.D., Jr. ....................................................... 18 

Bundtzen, T .K .......................................................... 50 

G 

Gamble, B.M ........................................................... 22 

Geissman, J.W .......................................................... 38 

Gerlitz, C.N ............................................................. 72 

Giles, D.A ............................................................... 65 

Goldhaber, M ........................................................... 23 

c 

Campbell, A. C .......................................................... 83 

Campbell, D.L. ................................................ 6, 70, 77 

Cannon, W.F ........................................................ 7, 49 

Carlson, C ............................................................... 43 

Case, J .E ................................................................. 33 

Champion, D.E ......................................................... 11 

Gottfried, D ............................................................. 23 

Grassle, J .F .............................................................. 83 

Grauch, R.I. ............................................................. 26 

Grauch, V.J.S ...................................................... 26, 32 

Green, A ................................................................... 7 

Grosz, A.E .............................................................. 51 

Grybeck, D.J ............................................................ 50 

Chandler, V.W .......................................................... 33 H 

Chao, E.C.T .............................................................. 8 Hammarstrom, J.M .................................................... 27 

Chazin, B ................................................................ 17 Hammond, R.H ......................................................... 64 

Clark, C.W .............................................................. 37 

Clark, R.N ............................................................... 77 

Hand, J ................................................................... 72 

Hannah, J .L ............................................................. 72 

Commeau, J.A .......................................................... 76 

Conrad, J .E .............................................................. 75 

Hardyman, R.F ......................................................... 38 

Harris, A. G .............................................................. 28 

Cookro, T.M ............................................................ 10 Harrison, J.E ............................................................ 47 

Cox, D.P ................................................................. 10 

Criss, R.E ................................................................ 11 

Hayes, T.S ............................................................... 51 

Hein, J.R ............................................................ 29, 41 

Cunningham, C.G .................................................. 4, 70 Hinkle, M.E ............................................................. 30 

Czamanske, G.K ....................................................... 72 Hofstra, A.H ....................................................... 30, 42 

0 Hoover, D.B ............................................................ 32 

Hopkins, D.M ........................................................... 32 

Dahl, A.R ................................................................ 30 Horan, M.F .............................................................. 11 

Daly, W.E ............................................................... 30 Horton, R.J ......................................................... 33, 67 

Day, W.C ................................................................ 13 Howe, S.S ............................................................... 33 

DeRosa, M.L ............................................................ 41 Huber, D.F .............................................................. 10 

Detterman, R.L ......................................................... 80 

Dohrenwend, J .C .................................................. 10, 14 

Drew, L.J ........................................................... 14, 74 Jachens, R.C .................................................. 10, 14, 35 

Drucker, M .............................................................. 74 Jenness, J ................................................................ 43 

Dwyer, J.L ...................................................... !, 16, 47 John, D.A ................................................................ 37 

96 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 
Jones, J .E ................................................................ 38 N 

Jones, M.B .............................................................. 30 Naeser, C.W .............................................................. 4 

Jones, O.D ............................................................... 57 Newberry, R.J .......................................................... 48 

Junwen, W ................................................................ 8 Nicholson, S.W ..................................................... 7, 49 

Nokleberg, W.J ......................................................... 50 

K Nutt, C.J ................................................................. 72 

Kang, J.-K ............................................................... 29 

Keith, T.E.C ............................................................ 72 0 

Keller, R.P .............................................................. 38 Okita, P.M ................................................................ 8 

Kirschenbaum, H ....................................................... 39 Oldow, J.S ............................................................... 38 

Kisvarsanyi, E.B ....................................................... 66 Orris, G.J ................................................................ 27 

Klein, D.P ................................................................. 1 Oscarson, R.L ........................................................... 72 

Klein, T.L .......................................................... 13, 40 Owens, J.P .............................................................. 51 

Kleinkopf, M.D ......................................................... 40 

Knepper, D.H ........................................................... 77 

Koeppen, R.P ........................................................... 40 

Koski, R.A .............................................................. 41 

Kover, A.N .............................................................. 38 

Krohn, M.D ............................................................. 32 

Kruse, F.A ............................................................... 77 

Kucks, R.P .............................................................. 67 

p 

Palmer, J.R .............................................................. 51 

Pearson, R.C ............................................................ 19 

Philpotts, J.A ............................................................ 53 

Phillips, J.D ............................................................. 71 

Pitkin, J.A .......................................................... 32, 77 

Plesha, J .L .......................................................... 44, 67 

L 

Labson, V.F ............................................... 6, 32, 67, 77 

Plumlee, G.S ............................................................ 55 

Podwysocki, M.H ................................................. 57, 70 

Landis, G.P .......................................................... 4, 30 

Lee, K .................................................................... 77 

Leventhal, J ............................................................. 42 

Q 

Quingrun, M ............................................................ 14 

Lane-Bostwick, C.M ................................................... 39 

Liberty, L.H ............................................................. 71 R 

Lierman, R.T ............................................................ 28 Rait, N ................................................................... 23 

Light, T.D ............................................................... 78 Raymond, W.H ......................................................... 19 

Link, P.K ................................................................ 81 Rexroad, C.B ........................................................... 28 

Livo, E ................................................................... 77 Rinehart, C.D ........................................................... 78 

Lovering, T.G ........................................................... 45 Robinson, G .R., Jr. .................................................... 57 

Ludington, S.D ......................................................... 10 Ross, S.L ................................................................ 83 

Rossmeissl, H.J ......................................................... 17 

M Rowan, L.C ............................................................. 77 

Madden-McGuire, D.J ................................................ .42 Rugg, R.D ............................................................... 17 

Manheim, F.T ........................................................... 39 Rye, R.0 ................................................................. 30 

Manske, S.L ............................................................. 78 Rytuba, J .J ............................................................... 59 

Marcus, S.M ............................................................ 43 

Marsh, S.P ............................................................... 44 s 

McCammon, R.B ....................................................... 78 Sampson, J.A ........................................................... 67 

McCarthy, J.H., Jr. .................................................... 45 Sandoval, E .............................................................. 44 

McHugh, J.B ............................................................ 47 Sawatzky, D.L .......................................................... 26 

McKee, E. H ............................................... 8, 10, 37, 75 Schmidt, J .M ............................................................ 62 

Medberry, M.G ......................................................... 67 Schruben, P.O .......................................................... 43 

Menges, C.M ...................................................... 10, 14 Schulz, K.J ............................................... 13, 49, 63, 66 

Miller, W.R ............................................................. 47 Schulz, M.S ............................................................. 29 

Milton, N.M ............................................................. 15 Setterholm, D.R ........................................................ 64 

Minkin, J.A ............................................................... 8 Shanks, W.C. III ....................................................... 83 

Moll, S.H ........................................................... 16, 47 Sherlock, M.G ..................................................... 10, 64 

Molnia, B.F ............................................................. 38 Shubat, M.A ....................................................... 70, 72 

Moring, B.C ................................................... 10, 14, 35 Silberman, M.L ......................................................... 65 

Mosier, E.L ............................................................. 17 Sims, P.K ........................................................... 63, 66 

Mouat, D.A ............................................................. 15 Singer, D.A ............................................................. 10 

Moye, F.J ................................................................ 81 Slack, J.F ................................................................ 66 

USGS Research on Mineral Resources-1989 Program and Abstracts 97 
Smith , B.D ............. .. .......... .. ....... .. .... .. .......... .. ........ 67 v 

Smith, T.E .......... , .... ........................ ... ... ... ... .. .... .. .. .. 50 Valentine , P.C ... .. ..... ............ ................. ...... ... .... .. .... 76 

Smoot, J.P . ..... ......... ........... ..... .. ...................... ........ 57 Vian , R.W . ........ .. ...... ... ....... .. .. ... .. .... ... ....... ......... .. .. 81 

Snee , L.W . ... .. .. .... ... .. ... ..... .. .......... ........ ... .. ............. 69 

Southwick, D.L. ...... .. .... ...... .. .. .... .. ...... ..... ................. 13 

Stein, H.J. ........ ................ ... ... .. ..... ......... .. .......... 70, 72 

Steven, T.A .......... ....... ... .... ... .. ..... ... ....... .... ... ...... .. .. 71 

Stewart, D.B . ... .. .. ... .. .. ... .. .. .. ... .. ... .. .... .... ... .. ...... .. .. .. . 71 

Stoeser, D.B .... .. .. ......... ... .... ........... .. ....... .... .. ..... ...... 72 

w 

Wallace , C.A ... .... .... .. .... ....... .. ........ ...... .......... ... ....... 47 

Wang , K ....... ..... ...... ..... ...... ..... .... ,. ........ .. ... ... ...... .. . 53 

Watson, K .... .. .. .. .... ...... ...... ...... .... .... .. ........... .. ........ 77 

Watts, K.C. , Jr. .... ..... ...... ..... ......... .. ............... ... .. ..... 66 

Weber, F.R ....... .... .......... .... .... .. ...... ........... .... .. ........ 78 

T Weijun , S .... ........... ... ........................................... 8, 14 

Tatsumoto, M .. ... ... .. .... .... ........ ... .. .. ... .. .... .. ............ 8, 53 

Theobald , P.K .. ... .. .... .. ............. ...... ... ........... ...... ... ..... 2 

Theodore , T.G ...... ..... ..... ........... ..... ..... ...... 10, 27 , 72, 75 

Thomason , R.E ..... .... .... .. ..... ............. .... ..... .. .... .. .... ... 37 

Thorman , C.H ...... ..... .... ..... ... .... ...... ... .. ...... .. ..... ....... 74 

Tidball, R.R .................... .... ... ... .. ... .. .. .. .... ... .... ... .... .. 74 

White , W.H .... .. ........ ..... .. .... ....... .. .. .......... ....... .. .... .. 80 

Whitney, H ....... .. .. .... .. ... ..... ... .... .. ... ...... ......... ....... .. . !? 

Willis, G.F .. ........ ... ... .......... ...... .. ... .... ....... .. .. .. ....... . 78 

Wilson, F.H ........ .. ... ........... .. ......................... .. ........ 80 

Worl , R.G . .... ...... ..... ... ...... .. .. .... ............. .. .... ..... ...... 81 

Wright, B.E ........ ...... ..... .... .... ... .. ......... .. ... .... .. ......... 71 

Tingley, J . ... ... ... ..... ..... .... ....... ..... ... ... .. ........ ...... ...... 10 y 

Tooker, E.W . ..... ... ... ... ...... ...... ... .... .... .. ......... ..... ..... . 75 

Tosdal, R.M . .......... ..... ..... ... .. .. ................... .. ........ 8, 78 

Trautwein , C.M .......... .. .. ..... .. .. .... .... .... .. .... ..... ... ... l6 , 47 

Yingzhen , R .... .. .. ... ............... .. .. ............. .... .. ..... ... .. ... 8 

z 

Turrin , B.D ......... .... ....... .......... .......... .. ......... .. ......... 75 Zhifen, W ......... ....... ..... .. .... ... .. .. .................... ... ...... 69 

Zientek, M.L. .. ..... .... .. .... ...... .. ... ...... ........... .............. 81 

u Zierenberg, R.A ..... ... .. ..... ... ...................... .. ......... 62, 83 

Unger, J.D .......... .. ... .. .. .. .. .... .... .. .. .. .... .. .. .. .. ... .... ....... ? ! Zimbelman, D.R ..... .... .. .... ................. .. ... ..... .. ..... ....... 70 

View of Mt. Tweto in Colorado, recently named after Ogden Tweto, a U.S. Geological Survey geologist. 

98 Fifth Annual V.E. McKelvey Forum on Mineral and Energy Resources 

GPO 685-041/9777