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Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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1

Sillitoe, Richard H., Georgi Magaranov, Veselin Mladenov, and Robert A. Creaser. "ROSEN, BULGARIA: A NEWLY RECOGNIZED IRON OXIDE-COPPER-GOLD DISTRICT." Economic Geology 115, no. 3 (May 1, 2020): 481–88. http://dx.doi.org/10.5382/econgeo.4731.

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Abstract The Rosen copper veins in southeastern Bulgaria are recognized for the first time as an iron oxide-copper-gold (IOCG) district. The veins are located in the East Srednogorie segment of the Carpathian-Balkan calc-alkaline volcano-plutonic arc and were formed during an end-stage interval of extreme slab rollback and intra-arc rifting, which gave rise farther east to seafloor spreading in the Western Black Sea basin. The resulting submarine volcano-sedimentary rift basin is dominated by intermediate to mafic shoshonitic to ultrapotassic volcanism and subsidiary gabbro to syenite intrusion. The E- to NE-striking veins define a NW-striking alignment along the western contact of the syenite-dominated Rosen pluton, inferred to be part of a large ring dike. More than 40 veins, the most important formerly mined to depths as great as 1,000 m, contain an early, pegmatoidal, calcic-potassic assemblage followed by predominant magnetite (including the mushketovite variety), chlorite, and carbonates but also quartz, chalcopyrite, pyrite, and numerous other metallic minerals, which combine to give an unusual Fe-Cu-Au-Mo-Co-Ni-U-light rare earth element (LREE)-W-Bi-Zn-Pb geochemical signature. The close correlation between Fe, Cu, U, and LREEs is evident even in the flotation tailings. Vein molybdenite was dated during this study at 80.6 ± 0.4 Ma, which is similar to a U-Pb zircon age for monzosyenite from the Rosen pluton. The mineralogic and compositional features of the Rosen district are comparable to those of well-known IOCG deposits worldwide and geometrically similar to the vertically extensive IOCG veins in the Coastal Cordillera province of northern Chile. The subsidiary granitophile signature that accompanies the characteristic siderophile IOCG suite was also recognized recently at the giant Olympic Dam deposit in South Australia and elsewhere. Although no exposed intrusion is definitively implicated in the genesis of the Rosen veins, coexisting gabbro and syenite fluid sources may be hypothesized at depth in or beneath the coeval ring dike.
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2

Brotodewo, Adrienne, Caroline Tiddy, Diana Zivak, Adrian Fabris, David Giles, Shaun Light, and Ben Forster. "Recognising Mineral Deposits from Cover; A Case Study Using Zircon Chemistry in the Gawler Craton, South Australia." Minerals 11, no. 9 (August 25, 2021): 916. http://dx.doi.org/10.3390/min11090916.

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Detrital zircon grains preserved within clasts and the matrix of a basal diamictite sequence directly overlying the Carrapateena IOCG deposit in the Gawler Craton, South Australia are shown here to preserve U–Pb ages and geochemical signatures that can be related to underlying mineralisation. The zircon geochemical signature is characterised by elevated heavy rare-earth element fractionation values (GdN/YbN ≥ 0.15) and high Eu ratios (Eu/Eu* ≥ 0.6). This geochemical signature has previously been recognised within zircon derived from within the Carrapateena orebody and can be used to distinguish zircon associated with IOCG mineralisation from background zircon preserved within stratigraphically equivalent regionally unaltered and altered samples. The results demonstrate that zircon chemistry is preserved through processes of weathering, erosion, transport, and incorporation into cover sequence materials and, therefore, may be dispersed within the cover sequence, effectively increasing the geochemical footprint of the IOCG mineralisation. The zircon geochemical criteria have potential to be applied to whole-rock geochemical data for the cover sequence diamictite in the Carrapateena area; however, this requires understanding of the presence of minerals that may influence the HREE fractionation (GdN/YbN) and/or Eu/Eu* results (e.g., xenotime, feldspar).
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3

Courtney-Davies, Liam, Cristiana L. Ciobanu, Simon R. Tapster, Nigel J. Cook, Kathy Ehrig, James L. Crowley, Max R. Verdugo-Ihl, Benjamin P. Wade, and Daniel J. Condon. "OPENING THE MAGMATIC-HYDROTHERMAL WINDOW: HIGH-PRECISION U-Pb GEOCHRONOLOGY OF THE MESOPROTEROZOIC OLYMPIC DAM Cu-U-Au-Ag DEPOSIT, SOUTH AUSTRALIA." Economic Geology 115, no. 8 (August 27, 2020): 1855–70. http://dx.doi.org/10.5382/econgeo.4772.

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Abstract Establishing timescales for iron oxide copper-gold (IOCG) deposit formation and the temporal relationships between ores and the magmatic rocks from which hydrothermal, metal-rich fluids are sourced is often dependent on low-precision data, particularly for deposits that formed during the Proterozoic. Unlike accessory minerals routinely used to track hydrothermal mineralization, iron oxides are dominant components of IOCG systems and are therefore pivotal to understanding deposit evolution. The presence of ubiquitous, magmatic-hydrothermal U-(Pb)-W-Sn-Mo–bearing zoned hematite resolves a range of geochronological issues concerning formation of the ~1.6 Ga Olympic Dam IOCG deposit, South Australia, at up to ~0.05% precision (207Pb/206Pb weighted mean; 2σ) using isotope dilution-thermal ionization mass spectrometry (ID-TIMS). Coupled with chemical abrasion-ID-TIMS zircon dates from host granite and volcanic rocks within and enclosing the ore-body, a confident magmatic-hydrothermal chronology is defined. The youngest zircon date from the granite intrusion hosting Olympic Dam indicates magmatism was occurring up until 1593.28 ± 0.26 Ma. The orebody was principally formed during a major mineralizing event following granite uplift and during cupola collapse, whereby the hematite with the oldest age is recorded in the outer shell of the deposit at 1591.27 ± 0.89 Ma, ~2 m.y. later than the youngest documented magmatic zircon. Hematite dates captured throughout major lithologies, different ore zones, and the ~2-km vertical extent of the deposit support ~2 m.y. of hydrothermal activity. New age constraints on the spatial-temporal evolution of the formation of Olympic Dam are considered with respect to a mantle to crustal continuum model. Cyclical tapping of magma reservoirs to maintain crystal mushes for extended time periods and incremental building of batholiths on the million-year scale prior to main mineralization pulses can explain the ~2-m.y. temporal window temporal window inferred from the data. Despite the challenge of reconciling such an extended window with contemporary models for porphyry deposits (≤1 m.y.), formation of Proterozoic ore deposits has been addressed at high-precision and supports the case that giant IOCG deposits may form over millions of years.
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4

Courtney-Davies, Ciobanu, Verdugo-Ihl, Slattery, Cook, Dmitrijeva, Keyser, et al. "Zircon at the Nanoscale Records Metasomatic Processes Leading to Large Magmatic–Hydrothermal Ore Systems." Minerals 9, no. 6 (June 16, 2019): 364. http://dx.doi.org/10.3390/min9060364.

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The petrography and geochemistry of zircon offers an exciting opportunity to better understand the genesis of, as well as identify pathfinders for, large magmatic–hydrothermal ore systems. Electron probe microanalysis, laser ablation inductively coupled plasma mass spectrometry, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging, and energy-dispersive X-ray spectrometry STEM mapping/spot analysis were combined to characterize Proterozoic granitic zircon in the eastern Gawler Craton, South Australia. Granites from the ~1.85 Ga Donington Suite and ~1.6 Ga Hiltaba Suite were selected from locations that are either mineralized or not, with the same style of iron-oxide copper gold (IOCG) mineralization. Although Donington Suite granites are host to mineralization in several prospects, only Hiltaba Suite granites are considered “fertile” in that their emplacement at ~1.6 Ga is associated with generation of one of the best metal-endowed IOCG provinces on Earth. Crystal oscillatory zoning with respect to non-formula elements, notably Fe and Cl, are textural and chemical features preserved in zircon, with no evidence for U or Pb accumulation relating to amorphization effects. Bands with Fe and Ca show mottling with respect to chloro–hydroxy–zircon nanoprecipitates. Lattice defects occur along fractures crosscutting such nanoprecipitates indicating fluid infiltration post-mottling. Lattice stretching and screw dislocations leading to expansion of the zircon structure are the only nanoscale structures attributable to self-induced irradiation damage. These features increase in abundance in zircons from granites hosting IOCG mineralization, including from the world-class Olympic Dam Cu–U–Au–Ag deposit. The nano- to micron-scale features documented reflect interaction between magmatic zircon and corrosive Fe–Cl-bearing fluids in an initial metasomatic event that follows magmatic crystallization and immediately precedes deposition of IOCG mineralization. Quantification of α-decay damage that could relate zircon alteration to the first percolation point in zircon gives ~100 Ma, a time interval that cannot be reconciled with the 2–4 Ma period between magmatic crystallization and onset of hydrothermal fluid flow. Crystal oscillatory zoning and nanoprecipitate mottling in zircon intensify with proximity to mineralization and represent a potential pathfinder to locate fertile granites associated with Cu–Au mineralization.
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5

Xing, Yanlu, Yuan Mei, Barbara Etschmann, Weihua Liu, and Joël Brugger. "Uranium Transport in F-Cl-Bearing Fluids and Hydrothermal Upgrading of U-Cu Ores in IOCG Deposits." Geofluids 2018 (August 28, 2018): 1–22. http://dx.doi.org/10.1155/2018/6835346.

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Uranium mineralization is commonly accompanied by enrichment of fluorite and other F-bearing minerals, leading to the hypothesis that fluoride may play a key role in the hydrothermal transport of U. In this paper, we review the thermodynamics of U(IV) and U(VI) complexing in chloride- and fluoride-bearing hydrothermal fluids and perform mineral solubility and reactive transport calculations to assess equilibrium controls on the association of F and U. Calculations of uraninite and U3O8(s) solubility in acidic F-rich (Cl : F = 100 [ppm-based]) hydrothermal fluids at 25–450°C, 600 bar, show that U(IV)-F complexes (reducing conditions) and uranyl-F complexes (oxidizing conditions) predominate at low temperature (T<~200°C), while above ~250°C, chloride complexes predominate in acidic solutions. In the case of uraninite, solubility is predicted to decrease dramatically as U(IV)Cl22+ becomes the predominant U species at T>260°C. In contrast, the solubility of U3O8(s) increases with increasing temperatures. We evaluated the potential of low-temperature fluids to upgrade U and F concentrations in magnetite-chalcopyrite ores. In our model, an oxidized (hematite-rich) granite is the primary source of F and has elevated U concentration. Hydrothermal fluids (15 wt.% NaCl equiv.) equilibrated with this granite at 200°C react with low-grade magnetite-chalcopyrite ores. The results show that extensive alteration by these oxidized fluids is an effective mechanism for forming ore-grade Cu-U mineralization, which is accompanied by the coenrichment of fluorite. Fluorite concentrations are continuously upgraded at the magnetite-hematite transformation boundary and in the hematite ores with increasing fluid : rock (F/R) ratio. Overall, the model indicates that the coenrichment of F and U in IOCG ores reflects mainly the source of the ore-forming fluids, rather than an active role of F in controlling the metal endowment of these deposits. Our calculations also show that the common geochemical features of hematite-dominated IOCG deposits can be related to a two-phase process, whereby a magnetite-hematite-rich orebody (formed via a number of processes/tectonic settings) is enriched in Cu ± U and F during a second stage (low temperature, oxidized) of hydrothermal circulation.
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6

Reid, Anthony. "The Olympic Cu-Au Province, Gawler Craton: A Review of the Lithospheric Architecture, Geodynamic Setting, Alteration Systems, Cover Successions and Prospectivity." Minerals 9, no. 6 (June 20, 2019): 371. http://dx.doi.org/10.3390/min9060371.

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The Olympic Cu-Au Province is a metallogenic province in South Australia that contains one of the world’s most significant Cu-Au-U resources in the Olympic Dam deposit. The Olympic Cu-Au Province also hosts a range of other iron oxide-copper-gold (IOCG) deposits including Prominent Hill and Carrapateena. This paper reviews the geology of the Olympic Cu-Au Province by investigating the lithospheric architecture, geodynamic setting and alteration systematics. In addition, since the province is almost entirely buried by post-mineral cover, the sedimentary cover sequences are also reviewed. The Olympic Cu-Au Province formed during the early Mesoproterozoic, ca. 1.6 Ga and is co-located with a fundamental lithospheric boundary in the eastern Gawler Craton. This metallogenic event was driven in part by melting of a fertile, metasomatized sub-continental lithospheric mantle during a major regional tectonothermal event. Fluid evolution and multiple fluid mixing resulted in alteration assemblages that range from albite, magnetite and other higher temperature minerals to lower temperature assemblages such as hematite, sericite and chlorite. IOCG mineralisation is associated with both high and low temperature assemblages, however, hematite-rich IOCGs are the most economically significant. Burial by Mesoproterzoic and Neoproterozoic-Cambrian sedimentary successions preserved the Olympic Cu-Au Province from erosion, while also providing a challenge for mineral exploration in the region. Mineral potential modelling identifies regions within the Olympic Cu-Au Province and adjacent Curnamona Province that have high prospects for future IOCG discoveries. Exploration success will rely on improvements in existing potential field and geochemical data, and be bolstered by new 3D magnetotelluric surveys. However, drilling remains the final method for discovery of new mineral resources.
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7

Rodriguez-Mustafa, Maria A., Adam C. Simon, Laura D. Bilenker, Ilya Bindeman, Ryan Mathur, and Edson L. B. Machado. "The Mina Justa Iron Oxide Copper-Gold (IOCG) Deposit, Peru: Constraints on Metal and Ore Fluid Sources." Economic Geology 117, no. 3 (May 1, 2022): 645–66. http://dx.doi.org/10.5382/econgeo.4875.

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Abstract Iron oxide copper-gold (IOCG) deposits are major sources of Cu, contain abundant Fe oxides, and may contain Au, Ag, Co, rare earth elements (REEs), U, and other metals as economically important byproducts in some deposits. They form by hydrothermal processes, but the source of the metals and ore fluid(s) is still debated. We investigated the geochemistry of magnetite from the hydrothermal unit and manto orebodies at the Mina Justa IOCG deposit in Peru to assess the source of the iron oxides and their relationship with the economic Cu mineralization. We identified three types of magnetite: magnetite with inclusions (type I) is only found in the manto, is the richest in trace elements, and crystallized between 459° and 707°C; type Dark (D) has no visible inclusions and formed at around 543°C; and type Bright (B) has no inclusions, has the highest Fe content, and formed at around 443°C. Temperatures were estimated using the Mg content in magnetite. Magnetite samples from Mina Justa yielded an average δ56Fe ± 2σ value of 0.28 ± 0.05‰ (n = 9), an average δ18O ± 2σ value of 2.19 ± 0.45‰ (n = 9), and Δ’17O values that range between –0.075 and –0.047‰. Sulfide separates yielded δ65Cu values that range from –0.32 to –0.09‰. The trace element compositions and textures of magnetite, along with temperature estimations for magnetite crystallization, are consistent with the manto magnetite belonging to an iron oxide-apatite (IOA) style mineralization that was overprinted by a younger, structurally controlled IOCG event that formed the hydrothermal unit orebody. Altogether, the stable isotopic data fingerprint a magmatic-hydrothermal source for the ore fluids carrying the Fe and Cu at Mina Justa and preclude significant input from meteoric water and basinal brines.
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8

CHU, Geng, and Xiaoyong YANG. "Geochemical Constraints on the Anqing Ore-cluster Field in Anhui: An IOCG (-U) Mineralization System." Acta Geologica Sinica - English Edition 88, s2 (December 2014): 348–49. http://dx.doi.org/10.1111/1755-6724.12372_1.

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9

Schlegel, Tobias U., Renee Birchall, Tina D. Shelton, and James R. Austin. "MAPPING THE MINERAL ZONATION AT THE ERNEST HENRY IRON OXIDE COPPER-GOLD DEPOSIT: VECTORING TO Cu-Au MINERALIZATION USING MODAL MINERALOGY." Economic Geology 117, no. 2 (March 1, 2022): 485–94. http://dx.doi.org/10.5382/econgeo.4915.

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Abstract Iron oxide copper-gold (IOCG) deposits form in spatial and genetic relation to hydrothermal iron oxide-alkali-calcic-hydrolytic alteration and thus show a mappable zonation of mineral assemblages toward the orebody. The mineral zonation of a breccia matrix-hosted orebody is efficiently mapped by regularly spaced samples analyzed by the scanning electron microscopy-integrated mineral analyzer technique. The method results in quantitative estimates of the mineralogy and allows the reliable recognition of characteristic alteration as well as mineralization-related mineral assemblages from detailed mineral maps. The Ernest Henry deposit is located in the Cloncurry district of Queensland and is one of Australia’s significant IOCG deposits. It is known for its association of K-feldspar altered clasts with iron oxides and chalcopyrite in the breccia matrix. Our mineral mapping approach shows that the hydrothermal alteration resulted in a characteristic zonation of minerals radiating outward from the pipe-shaped orebody. The mineral zonation is the result of a sequence of sodic alteration followed by potassic alteration, brecciation, and, finally, by hydrolytic (acid) alteration. The hydrolytic alteration primarily affected the breccia matrix and was related to economic mineralization. Alteration halos of individual minerals such as pyrite and apatite extend dozens to hundreds of meters beyond the limits of the orebody into the host rocks. Likewise, the Fe-Mg ratio in hydrothermal chlorites changes systematically with respect to their distance from the orebody. Geochemical data obtained from portable X-ray fluorescence (p-XRF) and petrophysical data acquired from a magnetic susceptibility meter and a gamma-ray spectrometer support the mineralogical data and help to accurately identify mineral halos in rocks surrounding the ore zone. Specifically, the combination of mineralogical data with multielement data such as P, Mn, As, P, and U obtained from p-XRF and positive U anomalies from radiometric measurements has potential to direct an exploration program toward higher Cu-Au grades.
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10

Ciobanu, Cristiana L., Max R. Verdugo-Ihl, Ashley Slattery, Nigel J. Cook, Kathy Ehrig, Liam Courtney-Davies, and Benjamin P. Wade. "Silician Magnetite: Si–Fe-Nanoprecipitates and Other Mineral Inclusions in Magnetite from the Olympic Dam Deposit, South Australia." Minerals 9, no. 5 (May 20, 2019): 311. http://dx.doi.org/10.3390/min9050311.

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A comprehensive nanoscale study on magnetite from samples from the outer, weakly mineralized shell at Olympic Dam, South Australia, has been undertaken using atom-scale resolution High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF STEM) imaging and STEM energy-dispersive X-ray spectrometry mapping and spot analysis, supported by STEM simulations. Silician magnetite within these samples is characterized and the significance of nanoscale inclusions in hydrothermal and magmatic magnetite addressed. Silician magnetite, here containing Si–Fe-nanoprecipitates and a diverse range of nanomineral inclusions [(ferro)actinolite, diopside and epidote but also U-, W-(Mo), Y-As- and As-S-nanoparticles] appears typical for these samples. We observe both silician magnetite nanoprecipitates with spinel-type structures and a γ-Fe1.5SiO4 phase with maghemite structure. These are distinct from one another and occur as bleb-like and nm-wide strips along d111 in magnetite, respectively. Overprinting of silician magnetite during transition from K-feldspar to sericite is also expressed as abundant lattice-scale defects (twinning, faults) associated with the transformation of nanoprecipitates with spinel structure into maghemite via Fe-vacancy ordering. Such mineral associations are characteristic of early, alkali-calcic alteration in the iron-oxide copper gold (IOCG) system at Olympic Dam. Magmatic magnetite from granite hosting the deposit is quite distinct from silician magnetite and features nanomineral associations of hercynite-ulvöspinel-ilmenite. Silician magnetite has petrogenetic value in defining stages of ore deposit evolution at Olympic Dam and for IOCG systems elsewhere. The new data also add new perspectives into the definition of silician magnetite and its occurrence in ore deposits.
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Hunt, Julie A., Tim Baker, James Cleverley, Garry J. Davidson, Anthony E. Fallick, and Derek J. Thorkelson. "Fluid inclusion and stable isotope constraints on the origin of Wernecke Breccia and associated iron oxide – copper – gold mineralization, Yukon." Canadian Journal of Earth Sciences 48, no. 10 (October 2011): 1425–45. http://dx.doi.org/10.1139/e11-044.

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Iron oxide – Cu ± Au ± U ± Co (IOCG) mineralization is associated with numerous Proterozoic breccia bodies, collectively known as Wernecke Breccia, in Yukon Territory, Canada. Multiphase breccia zones occur in areas underlain by Paleoproterozoic Wernecke Supergroup metasedimentary rocks and are associated with widespread sodic, potassic, and carbonate alteration assemblages. Fluid inclusion data indicate syn-breccia fluids were hot (185–350 °C) saline (24–42 wt.% NaCl equivalent) NaCl–CaCl2–H2O brines. Estimates of fluid pressure vary from 0.4 to 2.4 kbar (1 kbar = 100 MPa). Carbon and oxygen isotopic compositions of breccia-related carbonates range from ~–11‰ to +1.5‰ (Pee Dee belemnite (PDB)) and –2‰ to 20‰ (Vienna standard mean ocean water (V-SMOW); δ18Owater ~–8‰ to +15‰), respectively. δ13C and δ18O values for host Wernecke Supergroup limestone/dolostone vary from ~–2‰ to 1.6‰ and 12‰ to 25‰, respectively. Sulfur isotopic compositions of hydrothermal sulfides and sulfate vary from ~–12‰ to +13‰ and +8‰ to +17‰ (Cañon Diablo Troilite (CDT)), respectively. Syn-breccia biotite, muscovite, and actinolite have δD and δ18O values of ~–141‰ to –18‰ and +7‰ to +12‰ (V-SMOW; δ18Owater ~7‰ to 11‰), respectively. The Wernecke Breccias and the associated IOCG mineralization appear to have formed from largely nonmagmatic fluids — based on isotopic, fluid inclusion, and geological data. The emerging hypothesis is that periodic overpressuring of dominantly formational/metamorphic water led to repeated brecciation and mineral precipitation. The weight of overlying sedimentary rocks led to elevated fluid temperatures and pressures; fluid flow may have been driven by tectonics and (or) gravity with metals scavenged from host strata.
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Courtney-Davies, Liam, Cristiana Ciobanu, Simon Tapster, Daniel Condon, Allen Kennedy, Nigel Cook, Kathy Ehrig, Benjamin Wade, and Marcus Richardson. "Steps to developing iron-oxide U-Pb geochronology for robust temporal insights into IOCG and BIF mineralisation." Applied Earth Science 126, no. 2 (April 3, 2017): 51–52. http://dx.doi.org/10.1080/03717453.2017.1306241.

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13

Macmillan, Edeltraud, Nigel J. Cook, Kathy Ehrig, Cristiana L. Ciobanu, and Allan Pring. "Uraninite from the Olympic Dam IOCG-U-Ag deposit: Linking textural and compositional variation to temporal evolution." American Mineralogist 101, no. 6 (June 2016): 1295–320. http://dx.doi.org/10.2138/am-2016-5411.

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14

Macmillan, Edeltraud, Nigel J. Cook, Kathy Ehrig, and Allan Pring. "Chemical and textural interpretation of late-stage coffinite and brannerite from the Olympic Dam IOCG-Ag-U deposit." Mineralogical Magazine 81, no. 6 (December 2017): 1323–66. http://dx.doi.org/10.1180/minmag.2017.081.006.

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AbstractThe Olympic Dam iron-oxide copper-gold-silver-uranium deposit, South Australia, contains three dominant U minerals: uraninite; coffinite; and brannerite. Microanalytical and petrographic observations provide evidence for an interpretation in which brannerite and coffinite essentially represent the products of U mineralizing events after initial deposit formation at 1.6 Ga. Marked compositional and textural differences between the various types of brannerite and coffinite highlight the role of multiple stages of U dissolution and reprecipitation.On the basis of petrography (size, habit, textures and mineral associations) and compositional variation, brannerites are divided into four distinct groups (brannerite-A, -B, -C and -D), and coffinite into three groups (coffinite-A, -B and -C). Brannerite-A ranges in composition from what is effectively uraniferous rutile to stoichiometric brannerite, and has elevated (Mg +Mn + Na + K) and (Fe + Al) compared to other brannerite types. It displays the most diverse range of morphologies, including complex irregular-shaped aggregates, replacement bands, and discrete elongate seams. The internal structure of brannerite-A consists of randomly-oriented hair-like needles and blades. Brannerite-B (>5 μm in size) is generally prismatic and typically associated with baryte and REY minerals (REE+Y= REY). Brannerite-C and -D are both associated with Cu-(Fe)-sulfides and are typically composed of irregular masses and blebs (10–50 μm in size) with a more uniform or massive internal structure. Brannerite-D is distinct from -C and always contains inclusions of galena. Brannerite-B to -D all contain elevated ΣREY, with brannerite-B and -C having elevated As, and brannerite-D having elevated Nb.All coffinite is typically globular (each globule is 2–10 μm in size) to collomorphic in appearance. Coffinite-A ranges from discrete globules to collomorphic bands completely encompassing quartz. Coffinite-B is always found with uraninite, and includes collomorph coffinite enveloped by massive uraninite, as well as aureoles of coffinite on the margins of uraninite crystals. Coffinite-C is associated with brannerite and REY minerals. The majority of coffinite is heterogeneous.Brannerite and coffinite have probably precipitated as part of a late-stage hydrothermal U-event, which might have involved the dissolution and/or reprecipitation of earlier precipitated uraninite, or could represent the products of a later U mineralizing event. Evidence which supports formation of late-stage coffinite and brannerite includes: (1) low-Pb contents of both minerals; (2) coffinite is commonly found on the edges of uraninite, implying later deposition; and (3) coffinite is often found on the edge of brannerite aggregates, suggestive of brannerite precipitation occurred before coffinite. Moreover, there are many features (e.g. banding, scalloped edges, alteration rinds, variable compositions etc.) indicative of hydrothermal alteration processes.
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Logan, Leslie, Joel B. H. Andersson, Martin J. Whitehouse, Olof Martinsson, and Tobias E. Bauer. "Energy Drive for the Kiruna Mining District Mineral System(s): Insights from U-Pb Zircon Geochronology." Minerals 12, no. 7 (July 11, 2022): 875. http://dx.doi.org/10.3390/min12070875.

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The Kiruna mining district, Sweden, known for the type locality of Kiruna-type iron oxide–apatite (IOA) deposits, also hosts several Cu-mineralized deposits including iron oxide–copper–gold (IOCG), exhalative stratiform Cu-(Fe-Zn), and structurally controlled to stratabound Cu ± Au. However the relationship between the IOA and Cu-systems has not been contextualized within the regional tectonic evolution. A broader mineral systems approach is taken to assess the timing of energy drive(s) within a regional tectonic framework by conducting U-Pb zircon geochronology on intrusions from areas where Cu-mineralization is spatially proximal. Results unanimously yield U-Pb ages from the early Svecokarelian orogeny (ca. 1923–1867 Ma including age uncertainties), except one sample from the Archean basement (2698 ± 3 Ma), indicating that a distinct thermal drive from magmatic activity was prominent for the early orogenic phase. A weighted average 207Pb/206Pb age of 1877 ± 10 Ma of an iron-oxide-enriched gabbroic pluton overlaps in age with the Kiirunavaara IOA deposit and is suggested as a candidate for contributing mafic signatures to the IOA ore. The results leave the role of a late energy drive (and subsequent late Cu-mineralization and/or remobilization) ambiguous, despite evidence showing a late regional magmatic-style hydrothermal alteration is present in the district.
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Verdugo-Ihl, Max R., Cristiana L. Ciobanu, Nigel J. Cook, Kathy J. Ehrig, Liam Courtney-Davies, and Sarah Gilbert. "Textures and U-W-Sn-Mo signatures in hematite from the Olympic Dam Cu-U-Au-Ag deposit, South Australia: Defining the archetype for IOCG deposits." Ore Geology Reviews 91 (December 2017): 173–95. http://dx.doi.org/10.1016/j.oregeorev.2017.10.007.

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17

Kontonikas-Charos, Alkis, Cristiana L. Ciobanu, Nigel J. Cook, Kathy Ehrig, Roniza Ismail, Sasha Krneta, and Animesh Basak. "Feldspar mineralogy and rare-earth element (re)mobilization in iron-oxide copper gold systems from South Australia: a nanoscale study." Mineralogical Magazine 82, S1 (February 28, 2018): S173—S197. http://dx.doi.org/10.1180/minmag.2017.081.040.

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ABSTRACTNanoscale characterization (TEM on FIB-SEM-prepared foils) was undertaken on feldspars undergoing transformation from early post-magmatic (deuteric) to hydrothermal stages in granites hosting the Olympic Dam Cu-U-Au-Ag deposit, and from the Cu-Au skarn at Hillside within the same iron-oxide copper-gold (IOCG) province, South Australia. These include complex perthitic textures, anomalously Ba-, Fe-, or REE-rich compositions, and REE-flourocarbonate + molybdenite assemblages which pseudomorph pre-existing feldspars. Epitaxial orientations between cryptoperthite (magmatic), patch perthite (dueteric) and replacive albite (hydrothermal) within vein perthite support interface-mediated reactions between pre-existing alkali-feldspars and pervading fluid, irrespective of micro-scale crystal morphology. Such observations are consistent with a coupled dissolution-reprecipitation reaction mechanism, which assists in grain-scale element remobilization via the generation of transient interconnected microporosity. Micro-scale aggregates of hydrothermal hyalophane (Ba-rich K-feldspar), crystallizing within previously albitized areas of andesine, reveal a complex assemblage of calc-silicate, As-bearing fluorapatite and Fe oxides along reaction boundaries in the enclosing albite-sericite assemblage typical of deuteric alteration. Such inclusions are good REE repositories and their presence supports REE remobilization at the grain-scale during early hydrothermal alteration. Iron-metasomatism is recognized by nanoscale maghemite inclusions within ‘red-stained’ orthoclase, as well as by hematite in REE-fluorocarbonates, which reflect broader-scale zonation patterns typical for IOCG systems. Potassium-feldspar from the contact between alkali-granite and skarn at Hillside is characterized by 100–1000 ppm REE, attributable to pervasive nanoscale inclusions of calc-silicates, concentrated along microfractures, or pore-attached. Feldspar replacement by REE-fluorcarbonates at Olympic Dam and nanoscale calc-silicate inclusions in feldspar at Hillside are both strong evidence for the role of feldspars in concentrating REE during intense metasomatism. Differences in mineralogical expression are due to the availability of associated elements. Lattice-scale intergrowths of assemblages indicative of Fe-metasomatism, REE-enrichment and sulfide deposition at Olympic Dam are evidence for a spatial and temporal relationship between these processes.
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Xing, Yanlu, Barbara Etschmann, Weihua Liu, Yuan Mei, Yuri Shvarov, Denis Testemale, Andrew Tomkins, and Joël Brugger. "The role of fluorine in hydrothermal mobilization and transportation of Fe, U and REE and the formation of IOCG deposits." Chemical Geology 504 (January 2019): 158–76. http://dx.doi.org/10.1016/j.chemgeo.2018.11.008.

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Su, Zhi-Kun, Xin-Fu Zhao, Xiao-Chun Li, Mei-Fu Zhou, Allen K. Kennedy, Jian-Wei Zi, Carl Spandler, and Yue-Heng Yang. "UNRAVELING MINERALIZATION AND MULTISTAGE HYDROTHERMAL OVERPRINTING HISTORIES BY INTEGRATED IN SITU U-Pb AND Sm-Nd ISOTOPES IN A PALEOPROTEROZOIC BRECCIA-HOSTED IOCG DEPOSIT, SW CHINA." Economic Geology 116, no. 7 (November 1, 2021): 1687–710. http://dx.doi.org/10.5382/econgeo.4840.

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Abstract Precambrian iron oxide copper-gold (IOCG) deposits are generally encountered with multistage hydrothermal overprints and hence have complex isotopic records. Precise dating of ore-forming and overprinting events and assessment of time-resolved metal sources are fundamental for understanding ore genesis. Here, we quantify the evolution history by integrating in situ U-Pb dating of texturally constrained allanite and Sm-Nd isotope data of ores and major rare earth element (REE) minerals in the breccia-hosted Lanniping Fe-Cu deposit in Kangdian region, southwestern China. The economically mineralized breccia in Lanniping Fe-Cu deposit is characterized by pervasive and texturally destructive replacement of polymictic clasts, including host metasedimentary packages, the intruded dolerite, and pre-ore halokinetic breccia. Ore minerals in cements are mainly composed of magnetite, chalcopyrite, bornite, and variable amounts of REE-rich minerals (e.g., apatite and allanite/epidote). Two types of allanite were identified in ores. Type I prismatic allanite texturally intergrown with magnetite has a SHRIMP U-Pb age of 1728 ± 20 Ma (1σ), which matches a zircon U-Pb age of 1713 ± 14 Ma (2σ) for the dolerite clasts and provides the direct age constraint on the Fe-Cu mineralization event. Type II anhedral allanite shows complex zoning and is spatially associated with, but texturally later than, magnetite, apatite, and chalcopyrite. This type of allanite yields significantly younger SHRIMP dates of 1015 ± 33 (1σ) and 800 ± 16 Ma (1σ) for cores and rims, respectively, which correspond to discrete regional magmatic events and hence record hydrothermal overprint/remobilization events of ore minerals in the deposit. Integrated Sm-Nd isotope compositions of type I allanite, apatite, and whole ores generally align along the reference Sm-Nd isochron of 1728 Ma, further confirming the primary ore formation at ~1.7 Ga. Corresponding εNd(1728 Ma) values ranging from –2.8 to 0.3 are significantly higher than those of the host metasedimentary rocks (–9.5 to –6.2) but comparable to those of contemporaneous igneous intrusions (–0.3 to 5.3) in the region, demonstrating that REE components of the primary ores were dominantly sourced from rocks of mantle-derived affinity. Both cores and rims of the younger type II allanite grains have Nd isotope compositions consistent with the unique time-evolved line of the ~1.7 Ga ores, implying that REEs incorporated into type II allanite were ultimately sourced from the primary ores in this deposit. The combined texture, chemical, U-Pb, and Sm-Nd isotope data thus demonstrate that REE remobilization was localized during post-ore hydrothermal overprint with negligible external inputs of REEs to the primary ores in the Lanniping deposit. In this contribution, we not only date primary ore formation but also recognize several younger allanite generations that record internal metal redistributions in response to post-ore tectonothermal events. Our study highlights the potential of ore-associated REE minerals such as allanite for resolving the age of multiple stages of hydrothermal events in complex ore deposits by ion probe, provided that careful examination of textural and paragenetic relationship of ores is conducted. Our finding of these younger allanite generations also exemplifies the significance of evaluation on time-resolved metal input for better characterizing the evolution history of the IOCG deposits.
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deMelo, Gustavo H. C., Lena V. S. Monteiro, Roberto P. Xavier, Carolina P. N. Moreto, Erika S. B. Santiago, S. Andrew Dufrane, Benevides Aires, and Antonio F. F. Santos. "Temporal evolution of the giant Salobo IOCG deposit, Carajás Province (Brazil): constraints from paragenesis of hydrothermal alteration and U-Pb geochronology." Mineralium Deposita 52, no. 5 (November 11, 2016): 709–32. http://dx.doi.org/10.1007/s00126-016-0693-5.

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21

Escolme, Angela, David R. Cooke, Julie Hunt, Ron F. Berry, Roland Maas, and Robert A. Creaser. "The Productora Cu-Au-Mo Deposit, Chile: A Mesozoic Magmatic-Hydrothermal Breccia Complex with Both Porphyry and Iron Oxide Cu-Au Affinities." Economic Geology 115, no. 3 (May 1, 2020): 543–80. http://dx.doi.org/10.5382/econgeo.4718.

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Abstract The Productora Cu-Au-Mo deposit is hosted by a Cretaceous hydrothermal breccia complex in the Coastal Cordillera of northern Chile. The current resource, which includes the neighboring Alice Cu-Mo porphyry deposit, is estimated at 236.6 Mt grading 0.48% Cu, 0.10 g/t Au, and 135 ppm Mo. Local wall rocks consist of a thick sequence of broadly coeval rhyolite to rhyodacite lapilli tuffs (128.7 ± 1.3 Ma; U-Pbzircon) and two major intrusions: the Cachiyuyito tonalite and Ruta Cinco granodiorite batholith (92.0 ± 1.0 Ma; U-Pbzircon). Previous studies at Productora concluded the deposit had strong affinities with the iron oxide copper-gold (IOCG) clan and likened the deposit to Candelaria. Based on new information, we document the deposit geology in detail and propose a new genetic model and alternative classification as a magmatic-hydrothermal breccia complex with closer affinities to porphyry systems. Hydrothermal and tectonic breccias, veins, and alteration assemblages at Productora define five paragenetic stages: stage 1 quartz-pyrite–cemented breccias associated with muscovite alteration, stage 2 chaotic matrix-supported tectonic-hydrothermal breccia with kaolinite-muscovite-pyrite alteration, stage 3 tourmaline-pyrite-chalcopyrite ± magnetite ± biotite-cemented breccias and associated K-feldspar ± albite alteration, stage 4 chalcopyrite ± pyrite ± muscovite, illite, epidote, and chlorite veins, and stage 5 calcite veins. The Productora hydrothermal system crosscuts earlier-formed sodic-calcic alteration and magnetite-apatite mineralization associated with the Cachiyuyito stock. Main-stage mineralization at Productora was associated with formation of the stage 3 hydrothermal breccia. Chalcopyrite is the dominant hypogene Cu mineral and occurs predominantly as breccia cement and synbreccia veins with pyrite. The Alice Cu-Mo porphyry deposit is characterized by disseminated chalcopyrite and quartz-pyrite-chalcopyrite ± molybdenite vein stockworks hosted by a granodiorite porphyry stock. Alice is spatially associated with the Silica Ridge lithocap, which is characterized by massive, fine-grained, quartz-altered rock above domains of alunite, pyrophyllite, and dickite. Rhenium-Os dating of molybdenite indicates that main-stage mineralization at Productora occurred at 130.1 ± 0.6 Ma, and at 124.1 ± 0.6 Ma in the Alice porphyry. Chalcopyrite and pyrite from Productora have δ34Ssulfide values from –8.5 to +2.2‰, consistent with a magmatic sulfur source and fluids evolving under oxidizing conditions. No significant input from evaporite- or seawater-sourced fluids was detected. Stage 3 tourmalines have average initial Sr of 0.70397, consistent with an igneous-derived Sr source. The Productora magmatic-hydrothermal breccia complex formed as a result of explosive volatile fluid release from a hydrous intrusive complex. Metal-bearing fluids were of magmatic affinity and evolved under oxidizing conditions. Despite sharing many similarities with the Andean IOCG clan (strong structural control, regional sodic-calcic alteration, locally anomalous U), fluid evolution at the Productora Cu-Au-Mo deposit is more consistent with that of a porphyry-related magmatic hydrothermal breccia (sulfur-rich, acid alteration assemblages and relatively low magnetite contents, &lt;5 vol %). The Productora camp is an excellent example of the close spatial association of Mesozoic magnetite-apatite, porphyry, and magmatic-hydrothermal breccia mineralization styles, a relationship seen throughout the Coastal Cordillera of northern Chile.
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Marschik, Robert, and Frank Söllner. "Early Cretaceous U–Pb zircon ages for the Copiapó plutonic complex and implications for the IOCG mineralization at Candelaria, Atacama Region, Chile." Mineralium Deposita 41, no. 8 (October 20, 2006): 785–801. http://dx.doi.org/10.1007/s00126-006-0099-x.

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23

Bacelar Hühn, Sérgio Roberto, Adalene Moreira Silva, Carla Braitenberg, Camille Rossignol, and Janaina Avila. "40Ar-39Ar age of the copper mineralization at riacho do pontal IOCG district and detrital zircon U–Pb ages of paragneiss host rocks." Journal of South American Earth Sciences 121 (January 2023): 104161. http://dx.doi.org/10.1016/j.jsames.2022.104161.

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Gelcich, Sergio, Donald W. Davis, and Edward T. C. Spooner. "Testing the apatite-magnetite geochronometer: U-Pb and 40Ar/39Ar geochronology of plutonic rocks, massive magnetite-apatite tabular bodies, and IOCG mineralization in Northern Chile." Geochimica et Cosmochimica Acta 69, no. 13 (July 2005): 3367–84. http://dx.doi.org/10.1016/j.gca.2004.12.020.

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25

Soloviev, Serguei G., Sergey G. Kryazhev, Vadim S. Kamenetsky, Vasily N. Shapovalenko, Svetlana S. Dvurechenskaya, Alexei V. Okulov, and Konstantin I. Voskresensky. "The Ulandryk and related iron oxide-Cu-REE(-Au-U) prospects in the Russian Altai: A large emerging IOCG-type system in a Phanerozoic continental setting." Ore Geology Reviews 146 (July 2022): 104961. http://dx.doi.org/10.1016/j.oregeorev.2022.104961.

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26

Park, Adrian F., Robert L. Treat, Sandra M. Barr, Chris E. White, Brent V. Miller, Peter H. Reynolds, and Michael A. Hamilton. "Structural setting and age of the Partridge Island block, southern New Brunswick, Canada: a link to the Cobequid Highlands of northern mainland Nova Scotia." Canadian Journal of Earth Sciences 51, no. 1 (January 2014): 1–24. http://dx.doi.org/10.1139/cjes-2013-0120.

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The Partridge Island block is a newly identified tectonic element in the Saint John area of southern New Brunswick, located south of and in faulted contact with Proterozoic and Cambrian rocks of the Ganderian Brookville and Avalonian Caledonia terranes. It includes the Lorneville Group and Tiner Point complex. The Lorneville Group consists of interbedded volcanic and sedimentary rocks, subdivided into the Taylors Island Formation west of Saint John Harbour and West Beach Formation east of Saint John Harbour. A sample from thin rhyolite layers interbedded with basaltic flows of the Taylors Island Formation at Sheldon Point yielded a Late Devonian – Early Carboniferous U–Pb (zircon) age of 358.9 +6/–5 Ma. Petrological similarities indicate that all of the basaltic rocks of the Taylors Island and West Beach formations are of similar age and formed in a continental within-plate tectonic setting. West of Saint John Harbour, basaltic and sedimentary rocks of the Taylors Island Formation are increasingly deformed and mylonitic to the south, and in part tectonically interlayered with mylonitic granitoid rocks and minor metasedimentary rocks of the Tiner Point complex. Based on magnetic signatures, the deformed rocks of the Tiner Point complex can be traced through Partridge Island to the eastern side of Saint John Harbour, where together with the West Beach Formation, they occupy a thrust sheet above a redbed sequence of the mid-Carboniferous Balls Lake Formation. The Tiner Point complex includes leucotonalite and aegirine-bearing alkali-feldspar granite with A-type chemical affinity and Early Carboniferous U–Pb (zircon) ages of 353.6 ± 5.7 and 346.4 ± 0.7 Ma, respectively. Based on similarities in age, petrological characteristics, alteration, iron oxide – copper – gold (IOCG)-type mineralization, and deformation style, the Partridge Island block is correlated with Late Devonian – Early Carboniferous volcanic–sedimentary–plutonic rocks of the Cobequid Highlands in northern mainland Nova Scotia. Deformation was likely a result of dextral transpression along the Cobequid–Chedabucto fault zone during juxtaposition of the Meguma terrane.
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McClenaghan, M. Beth, Wendy A. Spirito, Stephen J. A. Day, Martin W. McCurdy, Rick J. McNeil, and Stephen W. Adcock. "Overview of surficial geochemistry and indicator mineral surveys and case studies from the Geological Survey of Canada's GEM Program." Geochemistry: Exploration, Environment, Analysis 22, no. 1 (December 2, 2021): geochem2021–070. http://dx.doi.org/10.1144/geochem2021-070.

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The Geological Survey of Canada carried out reconnaissance-scale to deposit-scale geochemical and indicator-mineral surveys and case studies across northern Canada between 2008 and 2020 as part of its Geo-mapping for Energy and Minerals (GEM) program. In these studies, surficial geochemistry was used to determine the concentrations of up to 65 elements in various sample media including lake sediment, lake water, stream sediment, stream water, or till samples across approximately 1 000 000 km2 of northern Canada. As part of these surficial geochemistry surveys, indicator mineral methods were also used in regional-scale and deposit-scale stream sediment and till surveys. Through this program, areas with anomalous concentrations of elements and/or indicator minerals that are indicative of bedrock mineralization were identified, new mineral exploration models and protocols were developed, a new generation of geoscientists was trained, and geoscience knowledge was transferred to northern communities. Regional- and deposit-scale studies demonstrated how transport data (till geochemistry, indicator mineral abundance) and ice-flow indicator data can be used together to identify and understand complex ice flow and glacial transport. Detailed studies at the Izok Lake Zn–Cu–Pb–Ag VMS, Nunavut, the Pine Point carbonate-hosted Pb–Zn in the Northwest Territories, the Strange Lake REE deposit in Quebec and Labrador as well as U–Cu–Fe–F and Cu–Ag–Au–Au IOCG deposits in the Great Bear magmatic zone, Northwest Territories demonstrate new suites of indicator minerals that can now be used in future reconnaissance- and regional-scale stream sediment and till surveys across Canada.
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28

Clark, T., A. Gobeil, and J. David. "Iron oxide - copper - gold-type and related deposits in the Manitou Lake area, eastern Grenville Province, Quebec: variations in setting, composition, and style." Canadian Journal of Earth Sciences 42, no. 10 (October 1, 2005): 1829–47. http://dx.doi.org/10.1139/e05-048.

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The Manitou Lake area (Kwyjibo and Lac Marmont sectors), located in Quebec's eastern Grenville Province, contains magnetite-rich deposits with variable morphological, mineralogical, and chemical characteristics. Most Kwyjibo sector deposits are rich in Cu, rare-earth elements (REE), Y, P, F, and Ag and are anomalous in Th, U, Mo, W, Zr, and Au, and Lac Marmont sector deposits are commonly poor in these elements. Deposits occur in or are closely associated with 1175–1168 Ma leucogranite. They contain combinations of magnetite, clinopyroxene, blue–green hornblende, titanite, apatite, fluorite, quartz, biotite, andradite, epidote, albite, hematite, sulfides (chalcopyrite, pyrite, pyrrhotite, molybdenite, sphalerite), ilmenite, allanite, and other REE-bearing minerals. Veins and breccias are common. Most of the magnetite mineralization was preceded by potassic metasomatism (microcline) and was followed by most of the sulfides and radioactive minerals. Nearby sulfide-dominant deposits may be related. The deposits were formed by metasomatic replacement and fracture filling from hydrothermal fluids of variable composition, which were probably channeled in major, active faults. Oxygen-isotope data from magnetite-rich rocks suggest that fluids were predominantly magmatic and (or) metamorphic and that, locally, mixing with cooler meteoric water may have facilitated precipitation of sulfides and rare-metal minerals. Titanites in mineralized rock have been dated at 972 ± 5 Ma, but most magnetite may be older. Mineralization was syn- to post-tectonic and occurred in an orogenic to orogenic-collapse setting. The Cu–REE–Y-rich deposits are similar to iron oxide – copper – gold (IOCG) Olympic Dam type deposits, and copper- and rare-metals-poor occurrences resemble magnetite ± apatite Kiruna-type deposits.
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Billström, K., P. Evins, O. Martinsson, H. Jeon, and P. Weihed. "Conflicting zircon vs. titanite U-Pb age systematics and the deposition of the host volcanic sequence to Kiruna-type and IOCG deposits in northern Sweden, Fennoscandian shield." Precambrian Research 321 (February 2019): 123–33. http://dx.doi.org/10.1016/j.precamres.2018.12.003.

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30

Mukherjee, Rahul, Akella Satya Venkatesh, and Fareeduddin. "Geochemical characterization of mineralized albitite from Paleoproterozoic Bhukia IOCG‐IOA deposit of Aravalli‐Delhi Fold Belt, Rajasthan, western India: Genetic linkage to the gold (±Cu ± U) mineralization." Geological Journal 55, no. 6 (November 2, 2019): 4203–25. http://dx.doi.org/10.1002/gj.3669.

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31

Schmandt, Danielle S., Nigel J. Cook, Cristiana L. Ciobanu, Kathy Ehrig, Benjamin P. Wade, Sarah Gilbert, and Vadim S. Kamenetsky. "Rare Earth Element Phosphate Minerals from the Olympic Dam Cu-U-Au-Ag Deposit, South Australia: Recognizing Temporal-Spatial Controls On Ree Mineralogy in an Evolved IOCG System." Canadian Mineralogist 57, no. 1 (January 1, 2019): 3–24. http://dx.doi.org/10.3749/canmin.1800043.

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32

Landry, Kerstin, Erin Adlakha, Andree Roy-Garand, Anna Terekhova, Jacob Hanley, Hendrik Falck, and Edith Martel. "Uranium Mineralization in the MacInnis Lake Area, Nonacho Basin, Northwest Territories: Potential Linkages to Metasomatic Iron Alkali-Calcic Systems." Minerals 12, no. 12 (December 14, 2022): 1609. http://dx.doi.org/10.3390/min12121609.

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The intracratonic Paleoproterozoic Nonacho Basin, deposited on the western margin of the Rae craton, contains historic polymetallic (i.e., U, Cu, Fe, Pb, Zn, Ag) occurrences spatially associated with its unconformable contact with underlying crystalline basement rocks and regionally occurring faults. This study presents the paragenesis, mineral chemistry and geochemistry of uranium mineralized rocks and minerals of the MacInnis Lake sub-basin of the Nonacho Basin, to evaluate the style and relative timing of uranium mineralization. Mineralization is restricted to regionally occurring deformation zones, and post-dates widely spread and pervasive albitization and more local Ba-rich K-feldspar alteration of host rocks. Uranium mineralized rocks show elevated concentration of Cu, Ag and Au relative to variably altered host rocks. Microscopic and compositionally heterogeneous altered uraninite occurs (i) as overgrowths on partially dissolved Cu-sulphides with magnetite in chlorite ± quartz, calcite veins, and (ii) with minor uranophane in hematite-sericite-chlorite ± quartz breccia and stockwork. Both uraninite types are Th poor (<0.09 wt.% ThO2) and variably rich in SO4 (up to 2.26 wt.%), suggesting a low-temperature hydrothermal origin in a relatively oxidized environment. Rare-earth element (+Y) concentrations in type-i uraninite are high, up to 9.5 wt.% Σ(REE+Y)2O3 with CeN/YN values > 1, similar to REE compositions of uraninite in metasomatic iron and alkali-calcic systems (MIAC), including low-temperature hematite-type IOCG-deposits (e.g., Olympic Dam, Gawler Craton, Australia) and albitite-hosted uranium deposits (e.g., Southern Breccia, Great Bear Magmatic Zone, Canada, and Gunnar Deposit, Beaverlodge District, Canada). Both uraninite types are variably rich in Ba (up to 3 wt.% BaO), a geochemical marker for MIAC systems, provided by the dissolution of earlier secondary Ba-rich K-feldspar. Chemical U-Th-Pb dating yields minimum ages of 1757 to 1739 ± 70 Ma for type-ii uraninite-uranophane, consistent with strike-slip movement along regional structures of the basin. We suggest that MacInnis Lake uranium occurrences formed from oxidized hydrothermal fluids along previously altered (albitized, potassically altered) regional-scale faults. Uranium minerals precipitated on earlier Fe-rich sulfides (chalcopyrite, bornite), which acted as a redox trap for mineralization, in low-temperature (~310–330 °C, based on Al-in-chlorite thermometry) breccias and stockwork zones, late in a metasomatic iron and alkali-calcic alteration system.
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Gauthier, Michel, and Francis Chartrand. "Metallogeny of the Grenville Province revisited." Canadian Journal of Earth Sciences 42, no. 10 (October 1, 2005): 1719–34. http://dx.doi.org/10.1139/e05-051.

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Four new petrogenetic and metallogenic models are proposed herein to explain the formation of important mineral deposits in the Grenville Province, providing a framework from which to reappraise Grenvillian mineral potential. Recognition of a high-pressure metamorphic belt within the Grenville Province suggests a potential for eclogite-hosted rutile deposits, an important and much-sought commodity. A recently developed Norwegian model proposes that anorthosite genesis occurred through lower crust underplating and coeval partial melting, rather than by plume magmatism. Applied to the Grenville Province, the new petrogenetic model may provide insight into the widespread occurrence of platinum group element (PGE) poor nickel showings and the distribution of chromite, Ti-rich, and low-Ti iron-oxide deposits within the Grenville and adjacent terranes. A new type of sedimentary–exhalative (SEDEX) mineralization formed by oxidized brines has been defined following the discovery of new deposits in Australia. Applied to the Grenville Province, it provides a possible explanation for two long-recognized features of marble-hosted zinc deposits: (i) the presence of meta-siderite beds occurring as distal haloes around SEDEX zinc deposits, and (ii) the mutually exclusive division of these SEDEX deposits into massive sulphide and nonsulphide groups. The discovery of the giant Olympic Dam iron-oxide copper–gold (IOCG) deposit in Australia renewed the interest in magmatic low-Ti iron-oxide deposits in the Grenville Province that have been known and mined since early colonial times. Subsequent exploration in the northeastern part of the Grenville Province revealed the presence of breccia-hosted Cu–Au–U – rare-earth element (REE)-bearing iron-oxide mineralization. This deposit and other low-Ti iron-oxide deposits in the southwestern Grenville Province have a previously undocumented close spatial and temporal association with Ti-rich iron-oxide deposits. These examples demonstrate how new petrogenetic, tectonic, and ore deposit models developed in unmetamorphosed rocks can be successfully adapted to high-grade terranes, where they stimulate mineral exploration in these challenging conditions. Furthermore, by tracking the formation of ore deposits in the lower crust, the existence of unsuspected metallogenic associations in the higher crust, such as the low-Ti and high-Ti iron-oxide association observed in the Grenville Province, may be revealed.
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Keyser, William, Cristiana L. Ciobanu, Kathy Ehrig, Marija Dmitrijeva, Benjamin P. Wade, Liam Courtney-Davies, Max Verdugo-Ihl, and Nigel J. Cook. "Skarn-style alteration in Proterozoic metasedimentary protoliths hosting IOCG mineralization: the Island Dam Prospect, South Australia." Mineralium Deposita, February 27, 2022. http://dx.doi.org/10.1007/s00126-022-01096-1.

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AbstractNew mineralogical, geochemical, and geochronological data are presented for the Island Dam prospect, Olympic Cu-Au Province, South Australia. Skarn assemblages comprising actinolite/phlogopite + K-feldspar + magnetite suggest the presence of calcareous protoliths at Island Dam and indicate high-temperature alkali-calcic alteration in the early stages of IOCG mineralization, as seen in other deposits in the region. Dating of lamellar hematite intergrown with Cu-Fe-sulfides allows the timing of the alteration-mineralization event to be constrained at 1594 ± 28 Ma, contemporaneous with the ~ 1.59 Ga IOCG mineralization event recorded across the eastern Gawler Craton. The host metasedimentary sequence can be correlated to the Wallaroo Group based on lithology and fabrics, and stratigraphically by an underlying ~ 1850 Ma Donington Suite granite and the new U–Pb ages for superimposed mineralization. Oscillatory zoned silician magnetite in skarn displays a trace element signature comparable to that observed in the outer shell of the Olympic Dam deposit and the nearby Wirrda Well prospect and is consistent with early stages of IOCG mineralization. The geochemical signatures of hematite from skarn and banded Fe-rich metasedimentary rocks share a common enrichment in W, Sn, Mo, Th, and U seen in hematite from IOCG-style mineralization across the Gawler Craton. Relative enrichment in As, Sb, Ni, and Co is, however, specific to iron-oxides from banded Fe-rich metasedimentary rocks. These features can be attributed to pre-existing iron-rich lithologies.
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Fuentes-Guzmán, Edith, Eduardo González-Partida, Antoni CamprubÍ, Geovanny Hernández-Avilés, Janet Gabites, Alexander Iriondo, Giovanni Ruggieri, and Margarita López-Martínez. "The Miocene Tatatila–Las Minas IOCG skarn deposits (Veracruz) as a result of adakitic magmatism in the Trans-Mexican Volcanic Belt." Boletín de la Sociedad Geológica Mexicana 72, no. 3 (November 28, 2020). http://dx.doi.org/10.18268/bsgm2020v72n3a110520.

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The Cu- and Au-rich Tatatila–Las Minas IOCG skarn deposits in Veracruz (central-east Mexico) are circumscribed to the earliest stages of the Trans-Mexican Volcanic Belt (TMVB) and stand for a metallogenic province directly linked to its tectonomagmatic dynamics. This is the first well-documented case for such metallogenic province. These deposits were formed as skarns between rocks of the Mesozoic carbonate series and Miocene intermediate to acid hypabyssal rocks. New U-Pb zircon and 40Ar/39Ar ages provide evidence for four epochs of magmatic activity in the area: (1) early Permian (Artinskian), in association with the Paleozoic basement, (2) late Oligocene to early Miocene suite of pre-TMVB intrusive rocks, (3) middle to late Miocene suite of early TMVB-related intrusive rocks, and (4) Pliocene intrusive and extrusive rocks of the TMVB, possibly associated with the Los Humeros post-caldera stage. The obtained ages range between 24.60 ± 1.10 and 19.04 ± 0.69 Ma for stage 2, and between 16.34 ± 0.20 and 13.92 ± 0.22 Ma for stage 3. Stage 2 corresponds to a magmatic stage unheard of in the area, until this study. Only stage 3 rocks are associated with the IOCG skarn mineralization, with retrograde stages dated at 12.44 ± 0.09 (chromian muscovite, phyllic association) and 12.18 ± 0.21 Ma (zircon, potassic association). Therefore, the ages of stage-3 intrusive rocks are interpreted to date the formation of the prograde skarn associations (mostly ~15.4 to <14 Ma). The petrogenetic affinity of stage-2 and stage-3 rocks is about the same—the main difference has to do with higher Y and Yb contents in stage-3 rocks (although no affinity with within-plate granites was found), which is suggestive of an interaction of their parental magmas with alkaline magmas that most likely belong to the conterminous and contemporaneous Eastern Mexico Alkaline Province. Petrological indicators (elemental and isotopic) in Cenozoic rocks consistently point to intermediate to acid, metaluminous, I- and S-type rocks that were emplaced in a subduction-related continental arc, within the medium- to high-potassium calc-alkaline series, with high-silica adakitic signatures due associated to deep-sourced magmas that underwent crustal contamination to some degree. The various possible sources for the magmas with adakitic signature in this context can be narrowed down to two of them that are not mutually exclusive: adakitic derived from subducted slab melting and melting-assimilation-storage-homogenization (MASH)-derived adakites. Both sources are, in principle, capable of generating magmas that would eventually produce magmatic-hydrothermal mineralizing systems with an associated variety of ore deposit types, including IOCG. Also, both possible sources for adakites are compatible with the renewed steepening of the subducted slab after a period of flat subduction, for the earliest stage in the evolution of the TMVB.
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36

Pal, Dipak C., David Selby, and Akshay Kumar Sarangi. "Timing of shear deformation in the Singhbhum Shear Zone, India: implications for shear zone-hosted polymetallic mineralization." Geological Magazine, November 13, 2022, 1–7. http://dx.doi.org/10.1017/s0016756822001091.

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Abstract The Singhbhum Shear Zone in eastern India hosts several Fe oxide–Cu–Au (IOCG)-type polymetallic deposits, mined primarily for U, Cu and apatite, with elevated concentrations of rare earth elements, Ni, Co, Mo, Te and Au in association with low-Ti magnetite. Although the main stages of hydrothermal U, Cu and rare earth element mineralization are known to be Palaeoproterozoic in age, the age of shear deformation in the host shear zone has hitherto not been constrained. Here, we report Re–Os ages of syn-shearing massive molybdenite occurring along shear surfaces transecting the uranium ores in the Jaduguda uranium deposit. Integrating the obtained Re–Os age of c. 1.64–1.59 Ga of molybdenite, the known ages of mineralization and the known tectonothermal events in the adjoining Proterozoic Mobile Belt, we propose that the main stages of polymetallic hydrothermal mineralization pre-dated the pervasive shear deformation event in the Singhbhum Shear Zone. We further suggest that the shear zone was not the principal foci of the hydrothermal mineralization of the main stages. Instead, the shear zone was localized during the Palaeoproterozoic to Mesoproterozoic transition (c. 1.64–1.59 Ga) along pre-existing crustal-scale extensional faults which had earlier been the foci of hydrothermal alteration and mineralization in Palaeoproterozoic time (c. 1.9–1.8 Ga). Shear deformation and metamorphism have reconstituted/redistributed existing mineral/metal inventories with/without neo-mineralization.
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37

Steadman, Jeffrey A., Karsten Goemann, Jay M. Thompson, Colin M. MacRae, Ivan Belousov, and Max Hohl. "Hyperspectral cathodoluminescence, trace element, and U-Pb geochronological characterization of apatite from the Ernest Henry iron oxide copper-gold (IOCG) deposit, Cloncurry district, Queensland." Frontiers in Earth Science 10 (October 4, 2022). http://dx.doi.org/10.3389/feart.2022.926114.

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Hyperspectral cathodoluminescence (CL), geochemical, and geochronological characterization of a series of apatite-bearing samples from within and around the Ernest Henry IOCG deposit, NW Queensland, Australia, have revealed complex mineral parageneses and a spectrum of U-Pb ages that point to the effects of multiple geological processes. No two samples are identical, either in geochemistry or texture, despite their relative proximity to one another (all samples within 5 km from Ernest Henry). Hyperspectral CL maps reveal diverse internal textures and emissions ranging from near infrared (NIR) to near ultraviolet (UV) with a complex series of spectra in all samples, requiring the fitting more than 40 individual peaks (both sharp and broad) to capture the observed variability. Imaging analyses via LA-ICPMS show that apatite from the Ernest Henry district is enriched above background in a variety of trace elements, including Na, Mg, Al, Si, V, Mn, As, Sr, Y, the rare Earth elements (REEs), Pb, Th, and U. Samples outside the ore zone display chondrite-normalized REE profiles that are consistent with either a magmatic or hydrothermal origin, whereas ore zone apatite exhibits profiles that are decidedly hydrothermal in nature. Moreover, specific zones within ore zone apatite grains are very As-rich (up to 7 wt% As2O5), and the effect of such high As on the hyperspectral CL signature of these zones is a pronounced dampening of CL emission, regardless of REE concentrations. Uranium-Pb dating of the same samples (via LA-ICPMS) has yielded a diverse array of overlapping Mesoproterozoic ages ranging from 1,580 ± 34 Ma to 1,533 ± 61 Ma. These results correlate to published ages that constrain hydrothermal alteration in the Ernest Henry area, both before and during Cu-Au mineralization. Collectively, these data highlight the complexity of apatite studies at Ernest Henry, the broader Cloncurry district, and probably analogous terranes elsewhere. A combination of micro-scale methods such as those used in this study are shown to be essential for accurately deciphering geological information contained within petrogenetic indicator minerals.
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38

Acosta-Góngora, P., E. G. Potter, C. J. M. Lawley, L. Corriveau, and G. Sparkes. "Geochemical characterization of the Central Mineral Belt U ± Cu ± Mo ± V mineralization, Labrador, Canada: Application of unsupervised machine-learning for evaluation of IOCG and affiliated mineral potential." Journal of Geochemical Exploration, April 2022, 106995. http://dx.doi.org/10.1016/j.gexplo.2022.106995.

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39

"Iocg news — No. 8." Journal of Crystal Growth 100, no. 3 (March 1990): 668–74. http://dx.doi.org/10.1016/0022-0248(90)90270-u.

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