Geologic Field Notes and Geochemical Analyses of 

Outcrop and Drill Core from Mesoproterozoic Rocks and 

Iron-Oxide Deposits and Prospects of Southeast Missouri

By Warren C. Day and Matthew Granitto

Open-File Report 2014–1053

U.S. Department of the Interior

U.S. Geological Survey
ii

U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2014

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Suggested citation:

Day, W.C., and Granitto, Matthew, 2014, Geologic field notes and geochemical analyses of outcrop and drill core

from Mesoproterozoic rocks and iron-oxide deposits and prospects of southeast Missouri: U.S. Geological 

Survey Open-File Report 2014–1053, 7 p., http://dx.doi.org/10.3133/ofr20141053.

ISSN 2331-1258 (online)

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Although this information product, for the most part, is in the public domain, it also may contain copyrighted 

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iii

Contents

Abstract ......................................................................................................................................................................... 1

Introduction.................................................................................................................................................................... 1

Geochemical Analyses .................................................................................................................................................. 2

Analytical Techniques ................................................................................................................................................ 2

Quality Assurance/Quality Control ............................................................................................................................. 3

National Geochemical Database Dataset .................................................................................................................. 3

Summary of Geochemistry and Lithology Dataset ..................................................................................................... 4

Geologic Field Notes ..................................................................................................................................................... 5

References Cited........................................................................................................................................................... 6

Tables

1. Analytical methods used for geochemical analyses................................................................................................... 2

2. Chemical species and their lower limits of determination (LLD).............................................................................. link

3. National Geochemical Database dataset................................................................................................................ link

4. Chemical parameters.............................................................................................................................................. link

5. Summary geochemistry and lithology dataset ........................................................................................................ link

6. Field notes for Pea Ridge Iron Mine ....................................................................................................................... link

7. Field notes for surface outcrops.............................................................................................................................. link
iv

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd) 
Geologic Field Notes and Geochemical Analyses of 

Outcrop and Drill Core from Mesoproterozoic Rocks and 

Iron-Oxide Deposits and Prospects of Southeast Missouri

By Warren C. Day and Matthew Granitto

Abstract

The U.S. Geological Survey, in cooperation with the Missouri Department of Natural

Resources/Missouri Geological Survey, undertook a study from 1988 to 1994 on the iron-oxide deposits 

and their host Mesoproterozoic igneous rocks in southeastern Missouri. The project resulted in an 

improvement of our understanding of the geologic setting, mode of formation, and the composition of 

many of the known deposits and prospects and the associated rocks of the St. Francois terrane in 

Missouri. The goal for this earlier work was to allow the comparison of Missouri iron-oxide deposits in 

context with other iron oxide-copper ± uranium (IOCG) types of mineral deposits observed globally.

The raw geochemical analyses were released originally through the USGS National Geochemical 

Database (NGDB, http://mrdata.usgs.gov). The data presented herein offers all of the field notes, 

locations, rock descriptions, and geochemical analyses in a coherent package to facilitate new research 

efforts in IOCG deposit types. The data are provided in both Microsoft Excel (Version Office 2010) 

spreadsheet format (*.xlsx) and MS-DOS text formats (*.txt) for ease of use by numerous computer 

programs.

Introduction

This report presents the field data and geochemical analyses that supported U.S. Geological 

Survey (USGS) research carried out from 1988 to 1994 on the iron-oxide (± rare earth element ± copper 

± gold ± uranium) deposits and prospects, and their host Precambrian granite-rhyolite rocks in 

southeastern Missouri. The effort was part of a five-year USGS project effort, funded by the Mineral 

Resources Program, to understand the origin and mineral resource potential of iron-oxide deposits that 

have similarities to other iron-oxide, copper, gold (IOCG) deposits worldwide. A general discussion of 

the IOCG mineral deposit type can be found in Hitzman (2000), Williams and others (2005), Groves 

and others (2010), and Richards and Mumin (2013) and references therein.

The USGS effort entailed detailed geologic mapping at the Pea Ridge iron oxide-apatite deposit

(Seeger and others, 2001), which has notable rare earth element (REE) ± gold-bearing breccia pipes.

Currently, the Pea Ridge mine is flooded with no access to the underground workings, so the data 

presented herein, as well as the geologic mapping of Seeger and others (2001), preserve our 

understanding of this important deposit. This report also includes numerous field observations and 

geochemical analyses from other iron-oxide ± copper ± gold deposits and prospects throughout the St. 

Francois terrane (Boss-Bixby, Camels Hump, Kratz Spring, Bourbon, Iron Mountain, Shepherd 

Mountain, Cedar Hill, upper and lower Pilot Knob, Ketcherside Gap, and Cuthbertson Mountain) as 
2

well as the Silver Mines silver-lead-tungsten deposit, all hosted in the Mesoproterozoic St. Francois 

terrane of southeastern Missouri.

The field work presented in this report occurred over one- and two-week-long field sessions 

during 1988–1993 by W.C. Day and G.B. Sidder (USGS and formerly of the USGS, respectively).

Numerous observations were made in conjunction with Dr. Cheryl M. Seeger of the Missouri 

Department of Natural Resources Missouri Geological Survey (MDNR/MGS) and Mark A. Marikos, 

Laurence M. Nuelle, and Charles Roberts, all formerly with the MDNR/MGS. These observations 

underpin many of the observations and conclusions presented in numerous papers and maps from the 

project, including Cordell and others (1993), Day and others (1989, 1991, 1992, 1993, and 2001), 

Nuelle and others (1989a,b, 1991a,b,c, 1992), Seeger and others (2001), and Sidder and others (1991, 

1993a,b), Sidder and Day (1993). The geochemical data, compiled by Matthew Granitto, from the 

USGS National Geochemical Survey Database (NGDB, 

http://mrdata.usgs.gov/geochemistry/ngdbrock.html) provided the context for the analytical methods 

and levels of detection important for understanding the origin and limitations of the geochemical data.

The data are provided in both Microsoft Excel (Version Office 2010) spreadsheet format (*.xlsx) and 

MS-DOS text formats (*.txt).

Geochemical Analyses

The chemical, geologic, and geospatial data are presented as two sets of tables that include 

distinct geochemical data. Tables 1 through 5 contain the exhaustive data for 318 rock samples shown in 

the USGS NGDB as well as the parameters critical for describing the geochemical data. Tables 6 and 7 

provide summarized and interpreted geologic observations and location information for the same 

samples.

Analytical Techniques

Nineteen different analytical methods were employed by the laboratories of the former Branch 

of Geochemistry of the USGS from 1989 to 1994 to produce the geochemical data presented in this 

report. Table 1 provides a complete list of these methods and descriptive information for each.

Table 1. Analytical methods used for geochemical analyses.

Abbreviation Analytical Method Description Digestion Method

AA_CV Mercury by cold-vapor atomic absorption spectrometry (AAS) after multi-acid 

digestion and solution. HNO3-Na2Cr2O7

AA_GF_HBr Gold and tellurium by graphite furnace atomic absorption spectrometry (AAS)

after HBr-Br2 digestion and selective organic extraction with Aliquat 336-MIBK. HBr-Br2

AES_AZ_P

Silver, arsenic, gold, bismuth, cadmium, copper, molybdenum, lead, antimony 

and zinc by inductively coupled plasma-atomic emission spectrometry (ICPAES) after partial digestion with HCl-H2O2.HCl-H2O2

AES_HF Major and minor elements by inductively coupled plasma-atomic emission 

spectrometry (ICP-AES) after digestion with HF-HCl-HNO3-HClO4. HF-HCl-HNO3-HClO4

CP Whole rock total and iron trioxide by computation. None

DN Uranium and thorium by delayed neutron activation counting. None
3

Table 1. Analytical methods used for geochemical analyses.—Continued

Abbreviation Analytical Method Description Digestion Method

EDX Minor elements by energy-dispersive X-ray fluorescence (XRF) spectrometry. None

ES_SQ Major and minor elements by semi-quantitative emission spectrography. None

FA_MS Platinum group elements by inductively coupled plasma-mass spectrometry

(ICP-MS) after NiS fire assay chemical separation. NiS fire assay

GV Density, moisture and weight by gravimetry; loss on ignition (LOI) by weight 

loss after heating at 900 °C. None

ISE_Fuse Fluoride by ion specific electrode after fusion digestion. LiBO2 fusion

ISE_HF Chloride by ion specific electrode after multi-acid digestion with HF. KMnO4-H2SO4-HF

MS_ST_REE Rare earth elements by inductively coupled plasma-mass spectrometry (ICP-MS)

after Na2O2 sinter digestion. Na2O2 sinter

NA_LC Major and minor elements by long count instrumental neutron activation analysis

(INAA). None

NA_SC Major and minor elements by short count instrumental neutron activation 

analysis (INAA). None

TT_Flux Total water and bound water by Karl Fischer coulometric titration with flux after 

combustion. None

TT_HCl Carbon dioxide (acid soluble carbon) by coulometric titration after HClO4

digestion and extraction. HClO4

TT_HF Ferrous oxide by colorimetric or potentiometric titration after HF-H2SO4

digestion. HF-H2SO4

WDX_Fuse Major and minor elements by wavelength-dispersive X-ray fluorescence 

spectrometry (XRF) after LiBO2 fusion digestion. LiBO2-Li2B4O7 fusion

A list of chemical species and their lower limits of determination (LLD) for these analytical 

methods are in table 2, and documentation of these methods can be found in Arbogast (1996;

http://pubs.usgs.gov/of/1996/0525/report.pdf).

Quality Assurance/Quality Control

The USGS laboratories reporting these analyses use a variety of constituent standards (for 

example, USGS geochemical reference rock standard STM–1, nepheline syenite) and blanks for their 

internal quality assurance/quality control procedures (Arbogast, 1990; Taggart, 2002). Data for these 

reference samples are not included in the geochemical data tables, but a description of commonly used 

reference materials is available from the USGS (http://minerals.cr.usgs.gov/geo_chem_stand/).

National Geochemical Database Dataset

The NGDB dataset in table 3 contains 318 records (or rows), one for each rock sample analyzed, 

and has 20 fields (or columns) describing sample sites and the sample material collected at each site.

Each sample has a unique laboratory identification number (LAB_ID) as well as a unique field number 

(FIELD_ID) provided by the sample collector. Date of sample submission is stored in the 
4

DATE_SUBMITTED field. LATITUDE and LONGITUDE contain the geographic coordinates; precision 

is set at 0.0005 degree or less depending on the level of confidence. For instance, field measurements 

taken with a handheld global positioning system (GPS) or from field locations plotted on USGS 

topographic maps have a higher level of positional certainty than those drill hole or mine/prospect 

locations gathered from old records with locations estimated by quarter section (given at two significant 

figures). The locational information is based on the North American Datum of 1927 (NAD 27) and the 

Clarke 1866 ellipsoid. PRIMARY_CLASS defines the sample material; SECONDARY_CLASS and 

SPECIFIC_NAME provide more detail about the sample medium. Other fields contain information 

regarding sample source, geologic age, stratigraphic and lithologic unit, mineralization, alteration, and 

igneous structure.

The chemical data of the NGDB dataset are contained in 194 fields or parameters. The parameter 

name (column header) is an abbreviation, which is a concatenation of species determined (expressed 

units of measurement) and analytical method used. For example, the parameter “Sb_ppm_AES_AZ_P” 

represents the concentration of antimony, expressed in parts per million, as detected by inductively 

coupled plasma-atomic emission spectroscopy after partial digestion with H2O2-HCl leach and diisobutyl ketone (DIBK) extract. Table 4 contains the descriptions of these parameters. Measurements 

are numeric values of concentration, and negative values represent the lower limit of determination for 

the method (for example, “less than” values, such as <2), and values ending with 0.11111 denote the 

upper limit of determination for the method (for example, “greater than” values, such as >100 are 

expressed as 100.11111). 

Summary of Geochemistry and Lithology Dataset

The summary dataset for lithology and “best value” for geochemical data are given in table 5, 

which contains 318 records (or rows), one for each rock sample analyzed, and has four fields (or 

columns) describing the rock type and suite, and the ore deposit name and zone at each sample site. 

Each sample has a unique field number (FIELD_ID) provided by the sample collector, a unique 

laboratory number (LAB_ID) assigned to each submitted sample by the analytical laboratory that 

received the sample. Columns LATITUDE and LONGITUDE contain the geographic coordinates;

precision is set at 0.0005 degree, based on the North American Datum of 1927 (NAD 27) and the Clarke 

1866 ellipsoid. Field ROCK_DESC provides a brief description of the rock sampled as well as the mine 

or prospect from which the sample was taken (if appropriate). Each sample is classified into broad rock 

suites (ROCK_SUITE) similar to those described by Kisvarsayni (1981), the ore deposit or prospect and 

principal commodity of the deposit from which the sample was taken if appropriate 

(ORE_DEPOSIT_NAME), and the zone within the ore deposit or prospect sampled or if the sample was 

from the host rock (ORE_DEPOSIT_ZONE).

The chemical data of the summary dataset (table 5) is “best value” data that were populated 

element by element with chemical determinations and corresponding analytical method data from the 

NGDB by the use of Microsoft Access select and update queries. This process is detailed in Granitto 

and others (2013). Even when evaluating the same element, different analytical techniques will have 

results of varying data quality in terms of precision and accuracy, which can affect how the data can be 

used. Many factors including—(1) the weight of sample analyzed, (2) method of decomposition of the 

sample during the preparation for analysis, (3) sensitivity and accuracy of the instrument used in each 

method, (4) upper and lower limits of detection for a given element by a given method, (5) the age of 

the method and stage of its development when a specific analysis was performed, and (6) the exact 

analytical laboratory and equipment used—will affect the data quality and must be considered when 

determining which data to use for a given element.
5

Creation of the summary “best value” dataset (table 4) followed a rubric or decision tree that 

considered all these factors in ranking the analytical methods employed in this study to determine 

methods most useful to mineral resource evaluation. Though an analytical method may determine 

multiple species concentrations, each species in the summary table was ranked individually to consider 

the many factors mentioned above. Table 5 contains the ranking for each species measured.

Geologic Field Notes

The geologic field notes presented in tables 6 and 7 are keyed to unique location identifiers

(FIELD_ID). Table 6 provides the observations made by W.C. Day while developing the underground 

geologic map for the Pea Ridge mine (Seeger and others, 2001). The geochemical data in tables 3 and 5, 

coupled with geologic observations presented in table 6 and those unpublished by the other authors, 

formed the basis of the map units used in Seeger and others (2001). In table 5, the mine level (given in 

feet below the original ground surface) and the drift from which the observation was made is listed in 

column MINE_LEVEL_DRIFT. Column ROCK_TYPE lists the rock type encountered whereas column 

ROCK_DESC provides a more detailed description of the rock type present. Table 7 provides the 

sample location and geologic observations from surface outcrops, mine, and prospect waste dumps. The 

data field labels are identical for those used in tables 5 and 6.
6

References Cited

Arbogast, B.F., 1990, Quality assurance manual for the Branch of Geochemistry, U.S. Geological 

Survey: U.S. Geological Survey Open-File Report 90–668, 184 p., accessed September 17, 2013, at

http://pubs.usgs.gov/of/1990/0668/report.pdf.

Arbogast, B.F., ed., 1996, Analytical methods manual for the Mineral Resource Surveys Program, U.S. 

Geological Survey: U.S. Geological Survey Open-File Report 96–525, 248 p., accessed September 

17, 2013, at http://pubs.usgs.gov/of/1996/0525/report.pdf.

Cordell, Lindrith, Sidder, G.B., and Day, W.C., 1993, Aeromagnetic constraints on shape of parent 

magma source at Pea Ridge, Missouri, magnetite mine: Symposium, Olympic Dam-type Deposits in the 

Midcontinent—Research and Exploration [abs]: Geological Society of America Abstracts with 

Programs, v. 25, no. 3, p. 14.

Day, W.C., Kisvarsanyi, E.B., Nuelle, L.M., Marikos, M.A., and Seeger, C.M., 1989, New data on the 

origin of the Pea Ridge iron-apatite deposit, southeastern Missouri—Implications for Olympic Damtype deposits [abs]: Geological Society of America Abstracts with Programs, v. 21, no. 6, p. A132.

Day, W.C., Seeger, C.M., and Rye, R.O., 2001, Review of the iron oxide deposits of Missouri—

Magmatic end members of the iron oxide-Cu-Au-U-REE deposit family [abs]: Geological Society of 

America Abstracts with Programs, v. 33, no. 6, p. 4.

Day, W.C., Sidder, G.B., Rye, R.O., Nuelle, L.M., and Kisvarsanyi, E.B., 1992, The Middle Proterozoic 

rhyolite-hosted Pea Ridge iron and rare-earth-element deposit-a magmatic source for Olympic Damtype deposits in the midcontinent region of the U.S.A., in Brown, P.E., and Chappell, B.W., eds.,

Second Hutton Symposium on The Origin of Granites and Related Rocks, Transactions of the Royal 

Society of Edinburgh, Earth Sciences, v. 83, Part 2, p. 489.

Day, W.C., Sidder, G.B., and Kisvarsanyi, E.B., 1993, Petrogenetic controls on the formation of middle 

Proterozoic iron+copper+rare earth element deposits of Missouri: Symposium, Olympic Dam-type 

Deposits in the Midcontinent—Research and Exploration [abs]: Geological Society of America Meeting

Abstracts with Programs, v. 25, no. 3, p. 16.

Day, W.C., Sidder, G.B., McCafferty, A.E., Cordell, L.E., Kisvarsanyi, E.B., Rye, R.O., and Nuelle, L.M., 

1991, A multidisciplinary study on the origin of Middle Proterozoic iron-rare earth 

element±copper±gold deposits in the Midcontinent region, U.S.A.: Seventh Annual V. E. McKelvey 

Forum on Mineral and Energy Resources, U.S. Geological Survey Circular 1062, p. 16.

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Geochemical Database, Version 2.0 (AGDB2)—Including “best value” data compilations for rock, 

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deposits through earth history—Implications for origin, lithospheric setting, and distinction from other 

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Missouri: Missouri Department of Natural Resources, Division of Geology and Land Survey 

Contribution to Precambrian Geology No. 8, Report of Investigations 64.
7

Nuelle, L.M., Marikos, M.A., Seeger, C.M., and Day, W.C., 1989a, Hydrothermal aspects of amphibole 

and magnetite emplacement in the Pea Ridge Fe-REE deposit, Washington County, Missouri [abs]:

Geological Society of America Abstracts with Programs, v. 21, no. 6, p. A248.

Nuelle, L.M., Seeger, C.M., Marikos, M.A., and Day, W.C., 1989b, Mineral assemblages of the Pea Ridge 

Fe-REE deposit—Implications of an Olympic Dam-type variant in southeast Missouri [abs]: Geological 

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pipes of the Pea Ridge iron mine, Washington County, Missouri: American Institute of Mining 

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ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20141053