Iron and Oxygen Isotope Signatures of the Pea Ridge and Pilot Knob Magnetite-Apatite Deposits, Southeast Missouri, USA

Childress, Tristan; Simon, Adam C.; Day, Warren C.; Lundstrom, Craig C.; Bindeman, Ilya N.

doi:10.2113/econgeo.111.8.2033

Cited by 57 publications

(35 citation statements)

References 47 publications

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“…King et al, 2008) that affected the Missouri deposits (and others) can eliminate the original igneous magnetite trace element signature. The conclusions reached by Hofstra et al (2016) are consistent with those reached by Childress et al (2016) who interpreted Fe and O stable isotope data for the Pea Ridge and Pilot Knob deposits in Missouri to indicate a magmatic source for the ore fluid in each deposit.…”

Section: Evidence From Other Systems For An Igneous And/or Magmatic-hsupporting

confidence: 82%

“…Also plotted inFigure 17are δ 56 Fe values for magnetite from the Mantoverde IOCG deposit, all of which plot within the range of δ 56 Fe consistent with magnetite crystallized from silicate melt or magmatic-hydrothermal fluid. The δ 18 O values for Pea Ridge and Pilot Knob that are elevated relative to purely orthomagmatic magnetite are explained byChildress et al (2016) to reflect crystallization of magnetite from a silicate melt. SeeBilenker et al (2016) for detailed data for samples from Chile and Sweden,Childress et al (2016) for data for PeaRidge and Pilot Knob, and Childress et al (writ.…”

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confidence: 92%

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Kiruna-Type Iron Oxide-Apatite (IOA) and Iron Oxide Copper-Gold (IOCG) Deposits Form by a Combination of Igneous and Magmatic-Hydrothermal Processes: Evidence from the Chilean Iron Belt

Simon¹,

Knipping²,

Reich³

et al. 2018

Metals, Minerals, and Society

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Iron oxide copper-gold (IOCG) and Kiruna-type iron oxide-apatite (IOA) deposits are commonly spatially and temporally associated with one another, and with coeval magmatism. Here, we use trace element concentrations in magnetite and pyrite, Fe and O stable isotope abundances of magnetite and hematite, H isotopes of magnetite and actinolite, and Re-Os systematics of magnetite from the Los Colorados Kiruna-type IOA deposit in the Chilean iron belt to develop a new genetic model that explains IOCG and IOA deposits as a continuum produced by a combination of igneous and magmatic-hydrothermal processes. The concentrations of [Al + Mn] and [Ti + V] are highest in magnetite cores and decrease systematically from core to rim, consistent with growth of magnetite cores from a silicate melt, and rims from a cooling magmatic-hydrothermal fluid. Almost all bulk δ 18 O values in magnetite are within the range of 0 to 5‰, and bulk δ 56 Fe for magnetite are within the range 0 to 0.8‰ of Fe isotopes, both of which indicate a magmatic source for O and Fe. The values of δ 18 O and δD for actinolite, which is paragenetically equivalent to magnetite, are, respectively, 6.46 ± 0.56 and -59.3 ± 1.7‰, indicative of a mantle source. Pyrite grains consistently yield Co/Ni ratios that exceed unity, and imply precipitation of pyrite from an ore fluid evolved from an intermediate to mafic magma. The calculated initial 187 Os/ 188 Os ratio (Osi) for magnetite from Los Colorados is 1.2, overlapping Osi values for Chilean porphyry-Cu deposits, and consistent with an origin from juvenile magma. Together, the data are consistent with a geologic model wherein (1) magnetite microlites crystallize as a near-liquidus phase from an intermediate to mafic silicate melt;(2) magnetite microlites serve as nucleation sites for fluid bubbles and promote volatile saturation of the melt;(3) the volatile phase coalesces and encapsulates magnetite microlites to form a magnetite-fluid suspension; (4) the suspension scavenges Fe, Cu, Au, S, Cl, P, and rare earth elements (REE) from the melt; (5) the suspension ascends from the host magma during regional extension; (6) as the suspension ascends, originally igneous magnetite microlites grow larger by sourcing Fe from the cooling magmatic-hydrothermal fluid; (7) in deep-seated crustal faults, magnetite crystals are deposited to form a Kiruna-type IOA deposit due to decompression of the magnetite-fluid suspension; and (8) the further ascending fluid transports Fe, Cu, Au, and S to shallower levels or lateral distal zones of the system where hematite, magnetite, and sulfides precipitate to form IOCG deposits. The model explains the globally observed temporal and spatial relationship between magmatism and IOA and IOCG deposits, and provides a valuable conceptual framework to define exploration strategies.

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Section: Evidence From Other Systems For An Igneous And/or Magmatic-hsupporting

confidence: 82%

mentioning

confidence: 92%

Kiruna-Type Iron Oxide-Apatite (IOA) and Iron Oxide Copper-Gold (IOCG) Deposits Form by a Combination of Igneous and Magmatic-Hydrothermal Processes: Evidence from the Chilean Iron Belt

Simon¹,

Knipping²,

Reich³

et al. 2018

Metals, Minerals, and Society

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“…Apatite remains highly stable across a wide range of temperature and pressure and is highly resistant to weathering processes. In geological studies, the various compositions of trace elements (eg, REEs, Sr, Fe, Mn, and halogens) and oxygen isotopes of apatite can be effectively integrated to trace the source and evolution of hydrothermal (including ore‐forming) fluids, igneous petrogenesis, and thermal‐chronological evolution . Apatite is also a key constituent in bones, teeth, and fish scales, analysing which in the fossil record can shed light on a variety of paleo‐environmental parameters .…”

Section: Introductionmentioning

confidence: 99%

“…In geological studies, the various compositions of trace elements (eg, REEs, Sr, Fe, Mn, and halogens) and oxygen isotopes of apatite can be effectively integrated to trace the source and evolution of hydrothermal (including ore-forming) fluids, igneous petrogenesis, and thermal-chronological evolution. [18][19][20][21] Apatite is also a key constituent in bones, teeth, and fish scales, analysing which in the fossil record can shed light on a variety of paleo-environmental parameters. 22,23 For instance, oxygen isotopic compositions in biogenic apatites have been widely used as a proxy for reconstructing seawater temperatures and major glaciation events…”

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confidence: 99%

Oxygen isotope homogeneity assessment for apatite U‐Th‐Pb geochronology reference materials

Yang

Xia

et al. 2019

Surface & Interface Analysis

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Secondary ion mass spectrometry (SIMS) measurement of oxygen isotopes in apatite has been employed more and more in petrogenetic, metallogenic, and climate change studies. Well‐characterised reference materials are needed due to the matrix effect, but they are yet to be well established. In this study, we conducted in‐situ oxygen isotopic and chemical analyses on six commonly used apatite reference materials (ie, Emerald, Kovdor, McClure, Mud Tank, Otter Lake, and Slyudyanka) and two in‐house apatite references (Qinghu and GEMS 203) to assess their oxygen isotope homogeneity and applicability for microbeam analyses. Our results show that all these apatite references are in general chemically homogeneous. In terms of oxygen isotopes, GEMS 203 (δ18O = 9.85 ± 0.40‰ [2SD], corrected by Durango 3), Kovdor (δ18O = 6.55 ± 0.38‰, 2SD), and McClure (δ18O = 5.94 ± 0.42‰, 2SD) are fairly homogeneous, whereas Emerald (δ18O = 10.37 ± 0.45‰, 2SD), Mud Tank (δ18O = 6.35 ± 0.46‰, 2SD), Otter Lake (δ18O = 9.71 ± 0.47‰, 2SD), Qinghu (δ18O = 5.44 ± 0.49‰, 2SD), and Slyudyanka (δ18O = 17.49 ± 0.43‰, 2SD) are less homogenous. This indicates that the former group represents better reference materials for in‐situ oxygen isotopic analyses, whilst the latter group can be used as secondary reference material for analytical quality control.

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“…Both of these deposit types are economically important as sources of commodities such as Fe, Cu, Au, U, and REE (Barton, 2014), making them a topic of scientific interest. These deposits are found in several metallogenic provinces around the world and formed throughout geologic time, from the Archean (e.g., Carajás Province, Brazil;de Melo et al, 2017) to early Proterozoic (e.g., Kiruna district, Sweden; Jonsson et al, 2013;Westhues et al, 2017), middle Proterozoic (e.g., Pea Ridge and Pilot Knob, USA; Day et al, 2016;Childress et al, 2016) to the Pliocene (e.g., El…”

Section: Introductionmentioning

confidence: 99%

New contributions to the understanding of Kiruna-type iron oxide-apatite deposits revealed by magnetite ore and gangue mineral geochemistry at the El Romeral deposit, Chile

Rojas

Barra

Deditius

et al. 2018

Ore Geology Reviews

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2018)New contributions to the understanding of Kiruna-type iron oxide-apatite deposits revealed by magnetite ore and gangue mineral geochemistry at the El Romeral deposit, Chile. Ore Geology Reviews New contributions to the understanding of Kiruna-type iron oxide-apatite deposits revealed by magnetite ore and gangue mineral geochemistry at the El Romeral deposit, Chile, Ore Geology Reviews (2018), doi: https://doi. ABSTRACTIron oxide-apatite (IOA) or Kiruna-type deposits are an important source of iron and other elements including REE, U, Ag, and Co. The genesis of these deposits remains controversial, with models that range from a purely magmatic origin to others that involve variable degrees of hydrothermal fluid involvement. To elucidate the formation processes of this deposit type, we focused on the Chilean Iron Belt of Cretaceous age and performed geochemical analyses on samples from El Romeral, one of the largest IOA deposits in northern Chile. We present a comprehensive field emission electron microprobe analysis (FE-EMPA) dataset of magnetite, apatite, actinolite, pyroxene, biotite, pyrite, and chalcopyrite, obtained from representative drill core samples. Two different types of magnetite grains constitute the massive magnetite bodies: an early inclusion-rich magnetite (Type I); and a pristine, inclusion-poor magnetite (Type II) that usually appears as an overgrowth around Type I magnetite. High V (~2500-2800 ppm) and Ti concentrations (~80-3000 ppm), and the presence of high-temperature silicate mineral inclusions (e.g., pargasite, ~800-1020°C) determined by micro-Raman analysis indicate a magmatic origin for Type I magnetite. On the other hand, high V (2300-2700 ppm) and lower Ti (50-400 ppm) concentrations of pristine, inclusion-poor Type-II magnetite indicate a shift from magmatic to hydrothermal conditions for this mineralization event. Furthermore, the composition of primary actinolite (Ca-and Mg-rich cores) within Type-II magnetite, the presence of F-rich apatite and high Co:Ni ratios (>1-10) of late stage pyrite mineralization are consistent with a high temperature (up to 840°C) genesis for the deposit. At shallow depths of the deposit, the presence of pyrite with low Co:Ni ratios (<0.5) and OH-rich apatite which contains higher Cl concentrations relative to F record a dominance of lower temperature hydrothermal conditions (<600ºC) and a lesser magmatic contribution. This vertical zonation, which correlates with the sub-vertical shape of the massive iron ore bodies, is concordant with a transition from magmatic to hydrothermal domains described in several IOA deposits along the Chilean Iron Belt, and supports a magmatic-hydrothermal model for the formation of the El Romeral. The close spatial and temporal association of the deposit with the Romeral Fault System suggests that a pressure drop related to changes in the tectonic stress had a significant impact on Fe solubility, triggering ore precipitation. radiometric 40 Ar/ 39 Ar ages of ca. 128 Ma (Rojas, 2017).Brecciated rocks with magnetite clast...

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Iron and Oxygen Isotope Signatures of the Pea Ridge and Pilot Knob Magnetite-Apatite Deposits, Southeast Missouri, USA

Cited by 57 publications

References 47 publications

Kiruna-Type Iron Oxide-Apatite (IOA) and Iron Oxide Copper-Gold (IOCG) Deposits Form by a Combination of Igneous and Magmatic-Hydrothermal Processes: Evidence from the Chilean Iron Belt

Kiruna-Type Iron Oxide-Apatite (IOA) and Iron Oxide Copper-Gold (IOCG) Deposits Form by a Combination of Igneous and Magmatic-Hydrothermal Processes: Evidence from the Chilean Iron Belt

Oxygen isotope homogeneity assessment for apatite U‐Th‐Pb geochronology reference materials

New contributions to the understanding of Kiruna-type iron oxide-apatite deposits revealed by magnetite ore and gangue mineral geochemistry at the El Romeral deposit, Chile

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