The geological framework and origin of the iron-copper-cobalt-gold-rare earth element (IOCG-REE) deposits in southeast Missouri are not well defined. In most areas, the geology surrounding the deposits is uncertain, owing to limited outcrops of the host Precambrian igneous rocks (St. Francois Mountains terrane) and a widespread cover, as much as about 450 meters thick, of Cambrian sedimentary rocks. As a result, the geometry, age, and petrology of buried plutons and subvolcanic intrusions in the St. Francois terrane--and potentially undiscovered metal deposits--are unknown, except where data are available from drill cores.
The geologic and geophysical components will address a regional area that includes known concealed deposits at Pea Ridge, Bourbon, Camel's Hump, Boss Bixby, and Kratz Spring. Depths to these deposits vary from 325 to 415 meters below the topographic surface.
The St. Francois Mountains terrane likely has the highest potential for undiscovered large rare earth element deposits in the conterminous United States. This terrane is geologically analogous to iron-copper-gold-rare earth element-uranium deposit and similar (but smaller) deposits that have been discovered there in recent years. All of these deposits in the Gawler Craton (south Australia) occur within granite and rhyolite, beneath hundreds of meters of flat-lying sedimentary rock, and each was discovered by airborne geophysics (Skirrow et al., 2002). Geological and geophysical techniques used successfully in the Gawler Craton, by the Australian Geological Survey Organisation and the Geological Survey of South Australia, will be evaluated by this project, and where relevant, applied to the St. Francois Mountains terrane.
The impact of this project will be significant in greatly improved understanding of iron-copper-cobalt-gold-rare earth element deposits in southeast Missouri. Data generated by the project will significantly advance the potential for new discoveries in the study area, including likely applications to other buried Mesoproterozoic terranes in the Midcontinent region.
Identifying new targets for exploration could result in the discovery of new deposits, which if delineated by drilling and determined to be commercially economic to mine,
Dempsey, W. J., and Meuschke, J. L., 1951a, Total intensity aeromagnetic map of Berryman quadrangle, Missouri: U.S. Geological Survey Geophysical Investigations Map GP-77, scale 1:31,680.
Dempsey, W. J., and Meuschke, J. L., 1951b, Total intensity aeromagnetic map of Sullivan quadrangle and part of Union quadrangle, Missouri: U.S. Geological Survey Geophysical Investigations Map GP-78, scale 1:31,680.
Kisvarsanyi, E.B., 1981, Geology of the Precambrian St. Francois terrane, southeastern Missouri: Missouri Department of Natural Resources Report of Investigations 64, 58 p.
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, southeast Missouri---Implications for Olympic Dam-type deposits: Geological Society of America Abstracts with Programs, v. 21, no. 6, p. A132.
Skirrow, R.G., Bastrakov, E., Raymond, O.L., Davidson, G., and Heithersay, P., 2002, The geological framework, distribution and controls of Fe-Oxide Copper-Gold mineralisation in the Gawler Craton, South Australia -Part II: Alteration and mineralisation, in Porter, T.M., ed., Hydrothermal iron oxide copper-gold & related deposits: A global perspective: Adelaide, PGC Publishing, v. 2, p 33-47.
Contact: Anne McCafferty, email@example.com
Since the vast majority of the St. Francois Mountain terrane is concealed beneath Paleozoic rocks and Quaternary deposits, delineation of buried structures, rock types, and IOA and IOCG ore systems must rely on potential field (aeromagnetic and gravity) geophysical data. Characterization of the host rocks, ore minerals, and ore-formation mineral assemblages are key to understanding the chemistry of ore forming systems.
We plan to use modern geophysical data processing techniques, spectral imaging, and petrophysical characterization to refine our understanding of the St. Francois Mountain terrane. Our initial efforts were to compile and interpret existing magnetic and ground gravity data, and we determined the existing magnetic and gravity data available were insufficient to distinguish important features at deposit scale. We acquired new magnetic, gravity gradiometry, and radiometric data (2014: magnetic and gravity gradiometry; 2015: magnetic and gamma ray) and used modern geophysical data processing techniques, which provided new insights into our understanding of the geology of the Precambrian basement. We also are examining and spectrally imaging our archive of several hundered, hand, core, and rock samples with CoreScan's new technique. Results will provide a unique library of compositional parameters and mineral maps related to an iron-oxide mineralized terrane in the U.S. Any newly acquired data from exposed parts of the St. Francois Mountains will aid in mapping surface variations in surface element chemistry and surface and subsurface magnetic signatures related to iron-oxide related alteration types. Models using recently developed in-house 3-D software of shallow deposits will be calculated to define the deposits' geometry and depth extent.
Our results will be used in other project activities to help refine the regional geologic framework, to relate the regional geophysical characteristics to new geochronological data of subsurface plutons, volcanic unites, and mineralized rock, and related the detailed mineralogy to the petrophysics (susceptibility and density) and regional geochemistry across the study area.
The Missouri iron-oxide deposits are members of the iron-oxide-copper-cobalt-gold rare earth element (IOCG-REE) deposit type, which have proven to be an important type for associated rare earth element (REE) mineral resources critical for modern industrial applications. Understanding the framework and ore genesis of the Missouri deposits hinges on understanding the buried Precambrian basement geology. The study area is predominantly concealed beneath a thick sequence Paleozoic rocks, Quaternary deposits, and dense vegetation. Recent work by the USGS, in conjunction with the Missouri Department of Natural Resources Division of Geology and Land Survey, laid the groundwork for understanding the regional geologic framework and ore genesis of the deposits. Integration of recently acquired data and interpretations is required to define the regional geologic and tectonic setting.
Our objective is to develop an updated geologic framework for the iron-oxide-apatite (IOA) and (IOCG) ore deposits by producting a regional scale integrated geophysical/geologic regional map and a modern geologic map of the Ironton, MO area. The Ironton area includes most of the outcropping ore deposits in the St. Francois Mountains, is relatively well exposed, and contains the complex volcanic geology and caldera structures that controlled the emplacement of the IOA and IOCG mineralizing systems. The new regional digital compilation will incorporate recent geologic mapping, geochronology, drill core data, and results of the latest USGS geophysical surveys.
Another goal is to provide a continental-scale framework for metallogeny and genesis of A-type 1.4 Ga granites along the southern margin of Laurentia. IOCG deposits in southeast Missouri are temporally and spatially associated with ~1.4 Ga igneous rocks; similar rocks exposed throughout southern Laurentia could host similar deposits.
Our objective is to determine the ages of formation of the deposits in the St. Francois Mountains terrane. Our initial work focused on the age and origin of Pea Ridge deposit rare earth element mineralization. New age data from this regional study of plutonic rocks will provide a temporal framework for derivation of improved tectonic and petrologic models for the Eastern Granite-Rhyolite province and the iron deposits. The results are critical for interpreting the results of potential field geophysics studies and isotope tracer studies. Important dating targets include:
We will utilize both U-Pb zircon sensitive high-resolution ion microprobe (SHRIMP) dating and laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) U-Pb analysis of magnetite deposits.
Contact: Robert Ayuso, firstname.lastname@example.org
Our task is focused on obtaining modern radiogenic isotope data (Nd-Sr-Pb) and trace element geochemistry to provide definitive information on source, age, and tectonic setting of magmas associated with rare earth element mineralization in southeast Missouri. The new geochemical information will help to evaluate the regional distribution and origin of rare earth element mineralized occurrences and their host rocks in order to distinguish between sources and settings associated with fertile or barren igneous rocks. The radiogenic isotope data will constrain the types of geochemical processes controlling the evolution of rare earth element mineralizing systems during magma transfer through the crust and the origin of hydrothermal fluids. New results will help to identify economically important targets that resemble the large Fe-rare earth element Pea Ridge deposit. These radiogenic isotope data are critical to understanding the relationship between basement terranes and the complexly mineralized units. T
Our initial efforts were focused on the Pea Ridge iron-oxide-apatite (IOA) deposit. Our current phase of research using radiogenic isotopes will be to broaden the effort from the Pea Ridge IOA deposit to include major igneous units from across the St. Francois Mountains terrane with the goal of fully understanding the tectonic setting as well as why the terrane hosts IOA and IOCG deposits and other 1.4 Ga igneous terranes across Laurentia appear to be barren. Is the IOA/IOCG ore formation in Missouri a singular event and if so, what is unique about the crustal architecture that led to mineral deposit formation?
Contact: Craig Johnson, email@example.com
We address basic ore genesis questions at the regional scale using stable isotope methods, using both published and new data on regional patterns in oxygen, hydrogen, and sulfur isotopes. We will tie in stable isotope data to the iron oxide-copper-cobalt-gold rare earth element deposits of the region to help constrain the origin of metals and fluids.
Contact: Albert Hofstra, firstname.lastname@example.org
In order to advance genetic and exploration models of iron oxide-apatite (IOA) and iron oxide-copper-cobalt-gold (IOCG) deposits that may host rare earth elements, additional knowledge is needed of the physical conditions (pressure-temperature), source(s) of ore fluid components, and processes that produce the minerals and mass transfer observed in these deposits. Our work initially focused on the Pea Ridge IOA rare earth element deposit in southeast Missouri. To facilitate comparisons, the next step is to collect similar data sets on other deposits in southeast Missouri. Resulting data, interpretations, and chemical models will be used to identify the key factors that produced each deposit type and help characterize the nature of the hydrothermal fluids and processes responsible for ore formation in the Missouri metallogenic province. This information will be used in the development of a USGS IOA-IOCG deposit model.
Contact: Matthew Granitto, email@example.com
Several data streams will be developed as an outgrowth of this project's research. This task will develop a project database containing archived and new geophysical, petrophysical, and geochemical data sets derived from all phases of the project. The compilation of project-generated data on a single user-friendly platform will facilitate the sharing of data, modeling, interpretation, and publication. The main datasets developed from this project will be released to the public.
Our objectives are to bring together all of the research done on the southeast Missouri IOA and IOCG deposits into one concise occurrence model relevant to Missouri and southern Laurentia. We will also update the USGS grade and tonnage models for IOA deposits and develop a robust data set and grade tonnage model for IOCG deposits worldwide. An integrated global USGS IOA/IOCG ore deposit model will be developed that pulls together the research done in Missouri with research from ore deposits around the world into a concise description of the deposit type and grade and tonnage information to help in future mineral resource assessments.
In our previous phase of this project, we focused on the Pea Ridge iron oxide-apatite deposit and its rare earth element resources. While many activities continue on with an emphasis of expanding efforts to a regional scale, some activities were intended to provide the needed data to determine current project efforts.
Contact: John Slack, firstname.lastname@example.org
The task's major goals were to characterize the inorganic geochemical composition of ores and altered wall rocks in the mineral deposits, and document the basic mineral textures and paragenesis. Methods used included standard observations including hand lens, binocular microscope, and polarizing microscope (both transmitted and reflected light). Findings provided critical information on the nature of the ores and wall rocks of the mineral deposits, and provided the foundation for future laboratory studies of the project.
Contact: Harvey Belkin, email@example.com
Knowledge of the mineralogy and mineral chemistry of various mineral phases in the iron-oxide-copper-cobalt-gold-rare earths deposits of southeast Missouri is incomplete. Without a detailed characterization, certain paragenetic and petrogenetic aspects of this deposit will remain uncertain. We worked to characterize the mineralogy and mineral chemistry of samples from the iron-copper-cobalt-gold-rare earths deposits of southeast Missouri. Electron microprobe wavelength-dispersive spectroscopy and scanning electron microscope (SEM) petrography and energy-dispersive spectroscopy were used to characterize, identify, and determine the composition of the constituent phases.
Contact: Gilpin Robinson, Jr., firstname.lastname@example.org
The consensus among many workers is that the iron-copper-cobalt-gold-rare earths deposits of southeast Missouri belong to the iron oxide-copper-gold (IOCG) family of mineral deposits (e.g., Kisvarsanyi and Kisvarsanyi, 1989; Seeger, 2000). However, the ages of these deposits, relative contributions of magmatic and meteoric fluids during mineralization, and sources of the contained metals, remain uncertain. We studied modeling of fluid-rock reactions in ore zones and altered wall rocks which is hoped to provide a mineralizing system aspect to the deposit studies.
Kisvarsanyi, G., and Kisvarsanyi, E.B., 1989, Precambrian geology and ore deposits of the southeast Missouri iron metallogenic province: Society of Economic Geologists, Field Trip Guidebook Series, v. 4, p. 1-40.
Seeger, C.M., 2000, Southeast Missouri iron metallogenic province: Characteristics and chemistry, in Porter, T.M., ed., Hydrothermal iron oxide copper-gold and related deposits: A global perspective: Adelaide, PGC Publishing, v. 1, p. 237-248.
Economic Geology December 2016 - Special Issue on Southeast Missouri, USA (Vol. 111, No. 8)
The following USGS authored/co-authored papers are listed in the order of the issue's Table of Contents.
Slack, J.F., Corriveau, L., and Hitzman, M.W., 2016, Preface: A Special Issue Devoted to Proterozoic Iron Oxide-Apatite (±REE) and Iron Oxide Copper-Gold and Affiliated Deposits of Southeast Missouri, USA, and the Great Bear Magmatic Zone, Northwest Territories, Canada: Economic Geology, 111(8), p. 1803–1814, doi:10.2113/econgeo.111.8.1803.
Day, W.C., Slack, J.F., Ayuso, R.A., and Seeger, C.M., 2016, Regional Geologic and Petrologic Framework for Iron Oxide ± Apatite ± Rare Earth Element and Iron Oxide Copper-Gold Deposits of the Mesoproterozoic St. Francois Mountains Terrane, Southeast Missouri, USA: Economic Geology, 111(8), p. 1825–1858, doi:10.2113/econgeo.111.8.1825.
McCafferty, A.E., Phillips, J.D., and Driscoll, R.L., 2016, Magnetic and Gravity Gradiometry Framework for Mesoproterozoic Iron Oxide-Apatite and Iron Oxide-Copper-Gold Deposits, Southeast Missouri: Economic Geology, 111(8), p. 1859–1882, doi:10.2113/econgeo.111.8.1859.
Aleinikoff, J.N., Selby, D., Slack, J.F., Day, W.C., Piller, R.M., Cosca, M.A., Seeger, C.M., Fanning, C.M., and Samson, I.M., 2016, U-Pb, Re-Os, and Ar/Ar Geochronology of Rare Earth Element (REE)-Rich Breccia Pipes and Associated Host Rocks from the Mesoproterozoic Pea Ridge Fe-REE-Au Deposit, St. Francois Mountains, Missouri: Economic Geology, 111(8), p. 1883–1914, doi:10.2113/econgeo.111.8.1883.
Neymark, L.A., Holm-Denoma, C.S., Pietruszka, A.J., Aleinikoff, J.N, Fanning, C.M., Pillers, R.M., and Moscati, R.J., 2016, High Spatial Resolution U-Pb Geochronology and Pb Isotope Geochemistry of Magnetite-Apatite Ore from the Pea Ridge Iron Oxide-Apatite Deposit, St. Francois Mountains, Southeast Missouri, USA: Economic Geology, 111(8), p. 1915–1933, doi:10.2113/econgeo.111.8.1915.
Ayuso, R.A., Slack, J.F., Day, W.C., and McCafferty, A.E., 2016, Geochemistry, Nd-Pb Isotopes, and Pb-Pb Ages of the Mesoproterozoic Pea Ridge Iron Oxide-Apatite–Rare Earth Element Deposit, Southeast Missouri: Economic Geology, 111(8), p. 1935–1962, doi:10.2113/econgeo.111.8.1935.
Harlov, D.E., Meighan, C.J., Kerr, I.D., and Samson, I.M., 2016, Mineralogy, Chemistry, and Fluid-Aided Evolution of the Pea Ridge Fe Oxide-(Y + REE) Deposit, Southeast Missouri, USA: Economic Geology, 111(8), p. 1963–1984, doi:10.2113/econgeo.111.8.1963.
Hofstra, A.H., Meighan, C.J., Song, X., Samson, I., Marsh, E.E., Lowers, H.A., Emsbo, P. and Hunt, A.G., 2016, Mineral Thermometry and Fluid Inclusion Studies of the Pea Ridge Iron Oxide-Apatite–Rare Earth Element Deposit, Mesoproterozoic St. Francois Mountains Terrane, Southeast Missouri, USA: Economic Geology, 111(8), p. 1985–2016, doi:10.2113/econgeo.111.8.1985.
Johnson, C.A., Day, W.C., and Rye, R.O., 2016, Oxygen, Hydrogen, Sulfur, and Carbon Isotopes in the Pea Ridge Magnetite-Apatite Deposit, Southeast Missouri, and Sulfur Isotope Comparisons to Other Iron Deposits in the Region: Economic Geology, 111(8), p. 2017–2032, doi:10.2113/econgeo.111.8.2017.
Childress, T.M., Simon, A.C., Day, W.C., Lundstrom, C.C., and Bindeman, I.N., 2016, Iron and Oxygen Isotope Signatures of the Pea Ridge and Pilot Knob Magnetite-Apatite Deposits, Southeast Missouri, USA: Economic Geology, 111(8), p. 2033–2044, doi:10.2113/econgeo.111.8.2033.
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://pubs.usgs.gov/of/2014/1053/.
Day, W.C., Granitto, Matthew, Slack, J.F., and Ayuso, R.A., 2016, Geochemical Database for Iron Oxide-Copper-Cobalt-Gold-Rare Earth Element Deposits of Southeast Missouri: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F7P26W67.
McCafferty, A.E., 2016, Airborne magnetic and radiometric survey, Ironton, Missouri area: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F7B56GT8.
McCafferty, A.E., 2016, Helicopter magnetic and gravity gradiometry survey over the Pea Ridge iron mine and surrounding area, southeast Missouri, 2014: U.S. Geological Survey data release, http://dx.doi.org/10.5066/F78P5XM4.
Aleinikoff, J., Neymark, L., Selby, D., Day, W., Slack, J., Holm-Denoma, C., Pillers, R., Seeger, C., and Samson, I., 2015, U-Pb and Re-Os geochronology of REE-rich breccia pipes and magnetite ore from the Mesoproterozoic Pea Ridge Fe-REE-Au deposit, St. Francois Mountains, Missouri, USA: Society for Economic Geologists 2015 Conference, Hobart, Australia, 27-30 September 2015. View Aleinikoff SEG abstract. [PDF file, 36 KB]
Aleinikoff, J.N., Selby, D., Day, W.C., Slack, J.F., Pillers, R.M., Seeger, C., and Samson, I.M., 2013, U-Pb and Re-Os geochronology of REE-rich breccia pipes from the Mesoproterozoic Pea Ridge Fe-REE-Au deposit, St. Francois Mountains, Missouri: Geological Society of America Abstracts with Programs, v. 45, p. 499. View Aleinikoff abstract.
Day, W.C., Aleinikoff, J., Seeger, C.M., and Slack, J.F., 2015, Regional geologic setting of the Mesoproterozoic iron oxide ore systems of southeast Missouri, USA: Society for Economic Geologists 2015 Conference, Hobart, Australia, 27-30 September 2015. View Day SEG abstract. [PDF file, 19 KB]
Hofstra, A.H., Meighan, C.J., and Emsbo, P., 2013, Microthermometric and ion ratio analyses of fluid inclusions from the Pea Ridge iron oxide-apatite (IOA) and Boss-Bixby iron oxide copper-gold (IOCG) deposits support a magmatic-hydrothermal origin: Geological Society of America Abstracts with Programs, v. 45, p. 499. View Hofstra 2013 GSA abstract.
Ives, B.T., Metzger, A., Mickus, K.L., and McCafferty, A.E., 2013, Regional gravity survey to aid in determining the REE potential of the Pea Ridge mine and the surrounding area, southeast Missouri: Geological Society of America Abstracts with Programs, v. 45, p. 276. View Ives 2013 GSA abstract.
Ives, B.T., Mickus, K.L., and McCafferty, A.E., 2014, Regional gravity survey investigating poorly studied areas of the northwest St. Francois terrane, southeast Missouri: Geological Society of America Abstracts with Programs, v. 46, no. 1, p. 6. View Ives 2014 GSA abstract.
Ives, B.T., Mickus, K.L., McCafferty, A.E., Seeger, C., and Starkey, M., 2014, Analyzing the Paleozoic basement structure and lithologies of the northwest St. Francois terrane, Missouri using gravity data to investigate possible mineral deposits of economic interest: Geological Society of America Abstracts with Programs, Vol. 46, No. 6, p. 308. View Ives 2014 GSA poster abstract.
Johnson, C.A., Day, W.C., and Rye, R.O., 2013, Stable isotope geochemistry of the Pea Ridge iron oxide-rare earth element deposit, St. Francois Mountains, southeastern Missouri: Temperature of ore formation, source of hydrothermal fluid, and source of sulfur: Geological Society of America Abstracts with Programs, v. 45, p. 499. View Johnson abstract.
McCafferty, A.E., 2014, Insights into concealed iron oxide-rare earth element deposits from new airborne geophysical data, southeast Missouri: Geological Society of America Abstracts with Programs, v. 46, No. 4, p. 15. View McCafferty 2014 abstract.
McCafferty, A.E., Day, W.C., Slack, J.F., McDougal, R.R., and Driscoll, R.L., 2013, Geophysical setting of iron oxide-copper-cobalt-gold-rare earth element deposits of southeast Missouri: Geological Society of America Abstracts with Programs, Vol. 45, No. 7, p. 537. View McCafferty 2013 abstract.
McCafferty, A.E., and Phillips, J.D., 2015, Shallow to Deep Crustal Controls on Localization of Mesoproterozoic Iron Oxide Copper-Gold-Rare Earth Element Deposits in Southeast Missouri (USA): Evidence from Gravity and Magnetic Data: Society for Economic Geologists 2015 Conference, Hobart, Australia, 27-30 September 2015. View McCafferty SEG 2015 abstract. [PDF file, 119 KB]
Meighan, C.J., Hofstra, A.H., Marsh, E.e., Lowers, H.A., Koenig, A.E., and Hitzman, M.W., 2015, Zr-in-rutile and Ti-in-quartz thermometry support a metasomatic origin for the Pea Ridge iron oxide-apatite-REE deposit, southeast Missouri, USA: Society for Economic Geologists 2015 Conference, Hobart, Australia, 27-30 September 2015. View Meighan SEG abstract. [PDF file, 32 KB]
Mercer, C.N., Watts, K.E., Meighan, C.J., and Bennett, M.M., 2015, Mineral and melt inclusion constraints on the petrogenesis of regional magmas and magnetite ore from the Pea Ridge (IOA-REE) and Boss Bixby (IOCG) deposits, USA: Society for Economic Geologists 2015 Conference, Hobart, Australia, 27-30 September 2015. View Mercer SEG abstract. [PDF file, 20 KB]
Neymark, L., Aleinikoff, J., Holm-Denoma, C., Pietruszka, A., Pillers, R., and Moscati, R., 2015, High spatial resolution SHRIMP and LA-ICPMS U-Pb geochronology of Pea Ridge Fe-REE-Au deposit, USA: Goldschmidt Conference, Prague, Czech Republic, 16-21 August 2015. View Neymark Goldschmidt abstract.
Slack, J.F., Day, W.C., McCafferty, A.E., Seeger, C., and Nold, J.L., 2013, A new look at iron oxide-apatite and iron oxide-copper-gold-rare earth element deposits in the Mesoproterozoic St. Francois Mountains terrane of southeast Missouri: Geological Society of America Abstracts with Programs, v. 45, p. 498. View Slack abstract.
Slack, J.F., McCafferty, A.E., Aleinikoff, J.N., Ayuso, R.A., Belkin, H.E., Cosca, M.A., Day, W.C., Hofstra, A.H., Johnson, C.A., Meighan, C.A., Neymark, L.A., Nold, J.L., Seeger, C.M., and Selby, D., 2014, Mesoproterozoic iron oxide-apatite and iron oxide-copper-gold-rare earth element deposits of southeast Missouri, USA: Geology, geophysics, and exploration potential: Society of Economic Geologists, Conference Proceedings, 27-30 September 2014, Keystone, Colorado, USA. [PDF file, 143 KB]
Central Mineral and Environmental Resource Science Center
Crustal Geophysics and Geochemistry Science Center