Giant Kiruna-type deposits form by efficient flotation of magmatic magnetite suspensions

Knipping, Jaayke L.; Bilenker, Laura; Simon, Adam C.; Reich, Martín; Barra, Fernando; Deditius, Artur P.; Lundstrom, Craig C.; Bindeman, Ilya N.; Muñizaga, Rodrigo

doi:10.1130/g36650.1

Cited by 184 publications

(96 citation statements)

References 31 publications

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“…As in the other example above (Figure 4), this reinforces the hypothesis that the earliest hydrothermal Fe-oxide formed at Olympic Dam is not necessarily magnetite, but hematite. This contradicts generic schemes of IOCG alteration invoking a so-called IOA-stage or "magnetiteapatite" assemblage, which is contended as typifying "early mineralisation" [48] at Olympic Dam, or indeed in IOCG and related "IOA" systems elsewhere (e.g., [49]). In Figure 5, we show HAADF STEM images and element maps of REE-fluorocarbonates from a locality adjacent to the Olympic Dam deposit.…”

Section: Haadf Stem Imaging and Stem-eds Mappingmentioning

confidence: 92%

Advances and Opportunities in Ore Mineralogy

et al. 2017

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Abstract:The study of ore minerals is rapidly transforming due to an explosion of new microand nano-analytical technologies. These advanced microbeam techniques can expose the physical and chemical character of ore minerals at ever-better spatial resolution and analytical precision. The insights that can be obtained from ten of today's most important, or emerging, techniques and methodologies are reviewed: laser-ablation inductively-coupled plasma mass spectrometry; focussed ion beam-scanning electron microscopy; high-angle annular dark field scanning transmission electron microscopy; electron back-scatter diffraction; synchrotron X-ray fluorescence mapping; automated mineral analysis (Quantitative Evaluation of Mineralogy via Scanning Electron Microscopy and Mineral Liberation Analysis); nanoscale secondary ion mass spectrometry; atom probe tomography; radioisotope geochronology using ore minerals; and, non-traditional stable isotopes. Many of these technical advances cut across conceptual boundaries between mineralogy and geochemistry and require an in-depth knowledge of the material that is being analysed. These technological advances are accompanied by changing approaches to ore mineralogy: the increased focus on trace element distributions; the challenges offered by nanoscale characterisation; and the recognition of the critical petrogenetic information in gangue minerals, and, thus the need to for a holistic approach to the characterization of mineral assemblages. Using original examples, with an emphasis on iron oxide-copper-gold deposits, we show how increased analytical capabilities, particularly imaging and chemical mapping at the nanoscale, offer the potential to resolve outstanding questions in ore mineralogy. Broad regional or deposit-scale genetic models can be validated or refuted by careful analysis at the smallest scales of observation. As the volume of information at different scales of observation expands, the level of complexity that is revealed will increase, in turn generating additional research questions. Topics that are likely to be a focus of breakthrough research over the coming decades include, understanding atomic-scale distributions of metals and the role of nanoparticles, as well how minerals adapt, at the lattice-scale, to changing physicochemical conditions. Most importantly, the complementary use of advanced microbeam techniques allows for information of different types and levels of quantification on the same materials to be correlated.

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Section: Haadf Stem Imaging and Stem-eds Mappingmentioning

confidence: 92%

Advances and Opportunities in Ore Mineralogy

et al. 2017

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“…Various studies of IOA deposits have proposed different petrogenetic models including magmatic (e.g., [58,66]), magmatic-hydrothermal [67], hydrothermal (-metasomatic) (e.g., [68][69][70]), and sedimentary exhalative (e.g., [71,72]). For the Bafq district, some researchers have referred to a magmatic model [17,28,73,74], whereas Torab and Lehmann (2007) [35], Jami (2005) [21], and Daliran (2010) [19] considered high-T hydrothermal fluids as being responsible for generation of some Bafq IOA deposits.…”

Section: Nature Of Fluidsmentioning

confidence: 99%

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

et al. 2018

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Abstract:The Chadormalu magnetite-apatite deposit in Bafq metallogenic province, Central Iran, is hosted in the late Precambrian-lower Cambrian volcano-sedimentary rocks with sodic, calcic, and potassic alterations characteristic of iron oxide copper-gold (IOCG) and iron oxide-apatite (IOA) ore systems. Apatite occurs as scattered irregular veinlets and disseminated grains, respectively, within and in the marginal parts of the main ore-body, as well as apatite-magnetite veins in altered wall rocks. Textural evidence (SEM-BSE images) of these apatites shows primary bright, and secondary dark areas with inclusions of monazite/xenotime. The primary, monazite-free fluorapatite contains higher concentrations of Na, Si, S, and light rare earth elements (LREE). The apatite was altered by hydrothermal events that led to leaching of Na, Si, and REE + Y, and development of the dark apatite. The bright apatite yielded two U-Pb age populations, an older dominant age of 490 ± 21 Ma, similar to other iron deposits in the Bafq district and associated intrusions, and a younger age of 246 ± 17 Ma. The dark apatite yielded a U-Pb age of 437 ± 12 Ma. Our data suggest that hydrothermal magmatic fluids contributed to formation of the primary fluorapatite, and sodic and calcic alterations. The primary apatite reequilibrated with basinal brines in at least two regional extensions and basin developments in Silurian and Triassic in Central Iran.

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“…(1) and (2) In hydrous and oxidized andesitic magmas, fluid bubbles exclusively attach to early crystallized magnetite microlites (first liquidus phase), and then the bubble-magnetite pairs rise due to buoyancy force (Figs. 10a, 10b) (Knipping et al, 2015).…”

Section: Magmatic-hydrothermal Evolution Of the Iron-rich Agglomeratesmentioning

confidence: 99%

“…An integrated magmatic-hydrothermal model has been proposed recently to interpret the coexistence of iron-rich melt and widespread hydrothermal alteration in typical Kiruna-type iron deposits (Zhou et al, 2013;Li Yanhe et al, 2014;Knipping et al, 2015;Tornos et al, 2016). Knipping et al, (2015) proposed a magmatichydrothermal model of efficient flotation of magmatic magnetite suspension which involves concentration of magnetite by the preferred wetting of magnetite followed by buoyant segregation of the early-formed magmatic magnetite-bubble pairs. Tornos et al (2016) considered that crystallization of iron-rich melts was accompanied by the exsolution of large amounts of vapor and a small volume of a hydrosaline melt which resulted in alkalicalcic alteration of the host andesite and steam-heated alteration zone at the top of the El Laco system.…”

Section: Magmatic-hydrothermal Evolution Of the Iron-rich Agglomeratesmentioning

confidence: 99%

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Occurrence of the Iron–rich Melt in the Heijianshan Iron Deposit, Eastern Tianshan, NW China: Insights into the Origin of Volcanic Rock–hosted Iron Deposits

Ding

et al. 2018

Acta Geologica Sinica (Eng)

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Long‐standing controversy persists over the presence and role of iron–rich melts in the formation of volcanic rock‐hosted iron deposits. Conjugate iron–rich and silica–rich melt inclusions observed in thin‐sections are considered as direct evidence for the presence of iron‐rich melt, yet unequivocal outcrop‐scale evidence of iron‐rich melts are still lacking in volcanic rock‐hosted iron deposits. Submarine volcanic rock‐hosted iron deposits, which are mainly distributed in the western and eastern Tianshan Mountains in Xinjiang, are important resources of iron ores in China, but it remains unclear whether iron‐rich melts have played a role in the mineralization of such iron ores. In this study, we observed abundant iron‐rich agglomerates in the brecciated andesite lava of the Heijianshan submarine volcanic rock–hosted iron deposit, Eastern Tianshan, China. The iron‐rich agglomerates occur as irregular and angular masses filling fractures of the host brecciated andesite lava. They show concentric potassic alteration with silicification or epidotization rims, indicative of their formation after the wall rocks. The iron‐rich agglomerates have porphyritic and hyalopilitic textures, and locally display chilled margins in the contact zone with the host rocks. These features cannot be explained by hydrothermal replacement of wall rocks (brecciated andesite lava) which is free of vesicle and amygdale, rather they indicate direct crystallization of the iron‐rich agglomerates from iron‐rich melts. We propose that the iron‐rich agglomerates were formed by open‐space filling of volatile‐rich iron‐rich melt in fractures of the brecciated andesite lava. The iron‐rich agglomerates are compositionally similar to the wall‐rock brecciated andesite lava, but have much larger variation. Based on mineral assemblages, the iron‐rich agglomerates are subdivided into five types, i.e., albite‐magnetite type, albite‐K‐feldspar‐magnetite type, K‐feldspar–magnetite type, epidote‐magnetite type and quartz‐magnetite type, representing that products formed at different stages during the evolution of a magmatic‐hydrothermal system. The albite‐magnetite type represents the earliest crystallization product from a residual iron‐rich melt; the albite‐K‐feldspar‐magnetite and K‐feldspar‐magnetite types show features of magmatic‐hydrothermal transition, whereas the epidote‐magnetite and quartz‐magnetite types represent products of hydrothermal alteration. The occurrence of iron‐rich agglomerates provides macroscopic evidence for the presence of iron‐rich melts in the mineralization of the Heijianshan iron deposit. It also indicates that iron mineralization of submarine volcanic rock‐hosted iron deposits is genetically related to hydrothermal fluids derived from iron‐rich melts.

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Giant Kiruna-type deposits form by efficient flotation of magmatic magnetite suspensions

Cited by 184 publications

References 31 publications

Advances and Opportunities in Ore Mineralogy

Advances and Opportunities in Ore Mineralogy

Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

Occurrence of the Iron–rich Melt in the Heijianshan Iron Deposit, Eastern Tianshan, NW China: Insights into the Origin of Volcanic Rock–hosted Iron Deposits

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