Magnetic Properties of Ferritchromite and Cr‐Magnetite and Monitoring of Cr‐Spinels Alteration in Ultramafic and Mafic Rocks

Hodel, Florent; Macouin, Mélina; Trindade, R. I.; Araújo, Jefferson F.D.F.; Respaud, Marc; Meunier, J. D.; Cassayre, Laurent; Rousse, Sonia; Drigo, L.; Schorne-Pinto, Juliano

doi:10.1029/2020gc009227

Cited by 11 publications

(8 citation statements)

References 63 publications

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“…The same holds true for Fe-Ti spinels and spinels with all three elements, though the magnetic properties of latter have not been thoroughly studied. We note that some of the Cr-magnetite grains in Hodel et al (2017) and Hodel et al (2020) are indeed ferromagnetic at room temperature and are therefore relevant.…”

Section: Relevant Terrestrial Iron Oxidesmentioning

confidence: 80%

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Likely Ferromagnetic Minerals Identified by the Perseverance Rover and Implications for Future Paleomagnetic Analyses of Returned Martian Samples

Mansbach,

Kizovski

et al. 2024

Preprint

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Although Mars today does not have a core dynamo, magnetizations in the Martian crust and meteorites suggest a magnetic field was present prior to 3.7 billion years (Ga) ago. However, the lack of ancient, oriented Martian bedrock samples available on Earth has prevented accurate estimates of the dynamo’s intensity, lifetime, and direction. Constraining the nature and lifetime of the dynamo are vital to understanding the evolution of the Martian interior and the potential habitability of the planet. The Perseverance rover, which is exploring Jezero crater, is providing an unprecedented opportunity to address this gap by acquiring absolutely oriented bedrock samples with estimated ages from ~2.3 to > 4.1 Ga. As a first step in establishing whether these samples could contain records of Martian paleomagnetism, it is important to determine their ferromagnetic mineralogy, the grain sizes of the phases, and the form of any natural remanent magnetization. Here, we synthesize data from various Perseverance instruments to achieve those goals and discuss the implications for future laboratory paleomagnetic analyses. Using the rover’s instrument payload, we find that cored samples likely contain iron oxides enriched in Cr and Ti. The relative proportions of Fe, Ti, and Cr indicate that the phases may be titanomagnetite or Fe-Ti-Cr spinels that are ferromagnetic at room temperature, but we cannot rule out the presence of non-ferromagnetic ulvöspinel, ilmenite, and chromite due to signal mixing. Importantly, the inferred abundance of iron oxides in the samples suggests that even <1 mm-sized samples will be easily measurable by present-day magnetometers.

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Section: Relevant Terrestrial Iron Oxidesmentioning

confidence: 80%

“…Fe-Cr spinels can be ferromagnetic at room temperature depending on the amount of Cr substitution in the spinel structure (Hodel et al, 2020), and is discussed further in the next section.…”

Section: Relevant Terrestrial Iron Oxidesmentioning

confidence: 99%

Likely Ferromagnetic Minerals Identified by the Perseverance Rover and Implications for Future Paleomagnetic Analyses of Returned Martian Samples

Mansbach,

Kizovski

et al. 2024

Preprint

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“…In the literature on the zoned chromites described above, there is no mention of textures consistent with porous-chromite oxidation (Gervilla et al, 2019;Hodel et al, 2020). The volcanic rocks sampled by the studies cited above were observed to be fresh with little to no evidence of alteration, which is not consistent with a weathering environment capable of significantly modifying chromite compositions in either hydrothermal (Hodel et al, 2020) or metamorphic (Gervilla et al, 2019) regimes. Instead, since the chromite FeO and Al 2 O 3 concentrations are observed to increase from core to rim (which is a geochemical signature of magmatic oxidation in our model, i.e.…”

Section: Assessing Chromite-melt Equilibrium Based On Model Equilibrium Trivalent Cation Proportionsmentioning

confidence: 96%

Petrogenetic implications of chromite-seeded boninite crystallization experiments: Providing a basis for chromite-melt diffusion chronometry in an oxybarometric context

Coulthard

Zellmer

Tomiya

et al. 2021

Geochimica et Cosmochimica Acta

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This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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“…The plot of the trivalent cations Al 3+ , Cr 3+ , and Fe 3+ differentiates among the Cr-Fe-spinels (Fig. 5b), and the criteria proposed by Barnes and Roeder (2001) and Hodel et al (2020) were adopted to define the compositional fields of magnetite sensu stricto (Cr 2 O 3 0-6 wt%), Cr-magnetite (Cr 2 O 3 6-13 wt%) and ferritchromite (Cr 2 O 3 > 13 wt%).…”

Section: Oxide Chemistry By Electron Microprobe (Epma)mentioning

confidence: 99%

Magnetite geochemistry as a proxy for metallogenic processes: A study on sulfide-mineralized mafic–ultramafic intrusions peripheral to the Kunene Complex in Angola and Namibia

Milani,

Oosthuizen,

Owen-Smith

et al. 2024

Miner Deposita

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Trace element concentrations in magnetite are dictated by the petrogenetic environment and by the physico-chemical conditions during magmatic, hydrothermal, or sedimentary processes. This makes magnetite chemistry a useful tool in the exploration of ore-forming processes. We describe magnetite compositions from Ni-Cu-(PGE)-sulfide mineralized rocks from seven mafic–ultramafic intrusions peripheral to the Mesoproterozoic AMCG (anorthosite-mangerite-charnockite-granite) suite of the Kunene Complex of Angola and Namibia to investigate metallogenic processes through the geochemical characterization of Fe-oxides, which were analyzed in-situ via Electron Probe Microanalysis (EPMA), and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). We identified magmatic magnetite, segregated from both a silicate liquid and an immiscible sulfide liquid. Elements like Cr, Co and V suggest that the sulfide-related magnetite segregated from a relatively primitive Fe-rich monosulfide solid solution (MSS). Secondary Cr-rich magnetite appears in intrusions with abundant chromite or Cr-spinel. Two types of hydrothermal magnetite were identified, related to the pervasive replacement of sulfides and a late-stage, low-T fluid circulation event. Magnetite replacing sulfides is associated with serpentinized ultramafic rocks and is preferentially observed in the intrusions with the highest base and precious metal tenors. The high concentration of Ni, Co, Cu, Pd, As and Sb in these grains is corroborated by the identification of micron-size PGE mineral inclusions. We infer that serpentinization during hydrothermal fluid circulation was accompanied by desulphurization of sulfides with metal remobilization and reconcentration to generate magnetite carrying Pd microinclusions. We suggest that the highly serpentinized ultramafic rocks in the Kunene Complex region may become a possible target for economic Ni-Cu-(PGE) mineralization.

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Magnetic Properties of Ferritchromite and Cr‐Magnetite and Monitoring of Cr‐Spinels Alteration in Ultramafic and Mafic Rocks

Cited by 11 publications

References 63 publications

Likely Ferromagnetic Minerals Identified by the Perseverance Rover and Implications for Future Paleomagnetic Analyses of Returned Martian Samples

Likely Ferromagnetic Minerals Identified by the Perseverance Rover and Implications for Future Paleomagnetic Analyses of Returned Martian Samples

Petrogenetic implications of chromite-seeded boninite crystallization experiments: Providing a basis for chromite-melt diffusion chronometry in an oxybarometric context

Magnetite geochemistry as a proxy for metallogenic processes: A study on sulfide-mineralized mafic–ultramafic intrusions peripheral to the Kunene Complex in Angola and Namibia

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