Trace Element Signature of Pyrite From the Los Colorados Iron Oxide-Apatite (Ioa) Deposit, Chile: A Missing Link Between Andean Ioa and Iron Oxide Copper-Gold Systems?

Reich, Martín; Simon, Adam C.; Deditius, Artur P.; Barra, Fernando; Chryssoulis, Stephen L.; Lagas, Gonzalo; Tardani, Daniele; Knipping, Jaayke L.; Bilenker, Laura; Sánchez-Alfaro, Pablo; Roberts, Malcolm P.; Muñizaga, Rodrigo

doi:10.2113/econgeo.111.3.743

Cited by 133 publications

(38 citation statements)

References 55 publications

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“…EPMA and SIMS analyses reveal that pyrite contains as much as 3.9 wt % Co and 1.5 wt % Ni, with a Co/Ni ratio >1 for almost all individual grains >1, and Co/Ni > 2 for many grains (Fig. 16; Reich et al, 2016). The elevated Co/Ni ratios of pyrite imply precipitation of pyrite from an ore fluid evolved from an intermediate to mafic magma (Taylor et al, 1969).…”

Section: Pyrite Chemistrymentioning

confidence: 98%

“…The concentrations of all of the aforementioned trace elements are relatively constant within single pyrite grains, and are similar among all magnetite samples from the Western dike and the mineralized diorite. For detailed tables with EPMA and SIMS data, see Reich et al (2016).…”

Section: Pyrite Chemistrymentioning

confidence: 99%

“…Topography of the mine is used as background for the mapped ore distribution. Modified fromReich et al (2016).…”

mentioning

confidence: 99%

“…Data sources: Bajwah et al(1987),Rieger et al (2010),Rusk et al (2010),Deol et al (2012),Piña et al (2013),Reich et al (2013), andSoltani Dehnavi et al (2015). FromReich et al (2016).…”

mentioning

confidence: 99%

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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: Pyrite Chemistrymentioning

confidence: 98%

Section: Pyrite Chemistrymentioning

confidence: 99%

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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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“…Pyrite is an ubiquitous phase in mineral deposits, and in IOA deposits pyrite is the most common sulfide mineral, frequently with subordinate amounts of chalcopyrite. Pyrite has the capacity to incorporate important and variable concentrations of metals and metalloids of economic relevance such as Au, Ag, Cu, Pb, Co, Ni, Zn, As, Sb, Te, Tl, Bi, among others (e.g., Cook and Chryssoulis, 1990;Huston et al, 1995;Reich et al, 2005;Large et al, 2009;Deditius et al, 2014;Reich et al, 2016), in both solid solution and/or nanoparticulate phases. The El Romeral pyrite contains <1.0 wt.% of Co and Ni ( Table 3).…”

Section: Hydrothermal Sulfide Stagementioning

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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Rb–Sr geochronology and geochemistry of pyrite from the Shihu gold deposit, central North China Craton: Implication for the timing and genesis of gold mineralization

Zeng

et al. 2019

Geological Journal

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The Shihu quartz vein‐type gold deposit in the central North China Craton occurs within Neoarchean TTG (tonalite‐trondhjemite‐granodiorite) gneisses and shows spatial relationship with quartz diorite porphyry. The occurrence of the ore body is controlled by the N‐S fracture. Primary mineral assemblage of the ore body is composed of quartz, calcite, and base‐metal sulphides, including pyrite, galena, sphalerite, chalcopyrite, and pyrrhotite. Eight pyrite samples from veins of the main mineralization stage yield an isochron age of 129 ± 3 Ma (MSWD = 1.6), coinciding with the major Early Cretaceous magmatic event, and associated lithospheric thinning recognized in the NCC. The (87Sr/86Sr)i values of the pyrite (0.7102 ± 0.0006) are lower than the continental crust mean value (0.719) and higher than that of the mantle initial ratio (0.707), suggesting mixed crust–mantle source for the metallogenic components. Three types of hydrothermal pyrite from the early to major ore‐forming stages were identified in the quartz vein, including Py(I) as disseminated euhedral grains, Py (II) as dense bulks, and Py (III) as intergrowth with base‐metal sulphides. Electron microprobe analysis of the pyrite grains indicates a trend from S‐deficient to S‐enriched and from Fe‐enriched to Fe‐deficient stages, suggesting an increase in sulphur fugacity and reducing conditions. The arsenic in pyrite shows decrease against increasing Au during Stages II and III, implying that As is not the only trigger of gold precipitation, but electrochemical‐geochemical barrier played a major role in the formation of the ore. The Co and Ni concentrations, as well as Co/Ni ratios in pyrite, are relatively high, which provide an additional clue to the link with the regional magmatic event. Combined with the textural features, we propose a wider potential for gold exploration in this region, linking the mineralization with a major transitional tectonic regime.

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Trace Element Signature of Pyrite From the Los Colorados Iron Oxide-Apatite (Ioa) Deposit, Chile: A Missing Link Between Andean Ioa and Iron Oxide Copper-Gold Systems?

Cited by 133 publications

References 55 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

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

Rb–Sr geochronology and geochemistry of pyrite from the Shihu gold deposit, central North China Craton: Implication for the timing and genesis of gold mineralization

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