U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY

MISCELLANEOUS FIELD STUDIES MAP MF–2353Version 1.0

SHEET 1 OF 5

Pamphlet accompanies map

GEOLOGIC MAPS AND CROSS SECTIONS OF MINE LEVELS AT THE PEA RIDGE IRON MINE, WASHINGTON COUNTY, MISSOURIBy

C.M. Seeger,1 L.M. Nuelle,2 W.C. Day,3 G.B. Sidder,4 M.A. Marikos,5 and D.C. Smith1

20011Missouri Department of Natural Resources, Division of Geology and Land Survey, P.O. Box 250, Rolla, MO 654012Doe Run Mining Company, P.O. Box 500, Viburnum, MO 655663U.S. Geological Survey, Denver, CO4Littleton, CO5University of Arizona, Department of Geosciences, Tucson, AZ 85705

Manuscript approved for publication April 10, 2001

Any use of trade names in this publication is fordescriptive purposes only and does not imply endorsement by the U.S. Geological Survey

This map was produced on request, directly fromdigital files, on an electronic plotter

For sale by U.S. Geological Survey Information ServicesBox 25286, Federal Center, Denver, CO 802251-888-ASK-USGS

A PDF for this map is available athttp://geology.cr.usgs.gov/pub/mf-maps/mf-2353

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Upper Cambrian

Middle Proterozoic

Unconformity

CORRELATION OF MAP UNITS

LIST OF MAP UNITS

Lamotte Sandstone (Upper Cambrian)

MIDDLE PROTEROZOIC UNITS

Aplite dikes

Mafic dikes

REE mineral-bearing breccia pipes

Silicified rock

Specular hematite

Hematite, undivided

Magnetite

Pseudobreccia

Magnetite-cemented pseudobreccia non-ore

Magnetite-cemented pseudobreccia ore

Hematite-cemented pseudobreccia

Iron oxide-cemented heterolithic breccia

Magnetite-cemented heterolithic breccia non-ore

Magnetite-cemented heterolithic breccia ore

Hematite-cemented heterolithic breccia

Iron oxide-cemented amphibole breccia

Magnetite-cemented amphibole breccia non-ore

Magnetite-cemented amphibole breccia ore

Hematite-cemented amphibole breccia

Magnetite-cemented breccia, undivided

Amphibole-quartz rock

Volcanic rocks

Banded rock

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Contact—Dashed where projected or inferred; jagged where extremely gradational

Fault—Showing approximate dip where known. Dashed where projected or inferred. R, reverse fault

Mine workings—Open-ended workings indicate stopes or abandoned areas

Development drill holes

Flat

Inclined up

Inclined down

Vertical—Cross sections only

Shaft location

Altered rock

Silicification and potassium feldspar alteration

Amphibole alteration

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1,825-FOOT LEVEL

SCALE 1:2,400200 2000 400 FEET100