Silica-bearing magnetites

Shcheka, S. A.; Romanenko, I. M.; Чубаров, В. М.; Kurentsova, N. A.

doi:10.1007/bf00398773

Cited by 22 publications

(9 citation statements)

References 4 publications

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“…Even microprobe analysis may be suspect where submicroscopic silicate inclusions might be encountered. Petrova and Tatarsky (1975) and Shcheka et al (1977) The petrologic implications of Fe2SiO 4 substitution in magnetite are difficult to assess quantitatively. The heterogeneous FezSiO 4 content of the Mickey Pass titanomagnetite phenocrysts suggests either that they equilibrated under variablefOz/T conditions, that their Si contents have been variably reset during oxidation-exsolution of ilmenite, or that Si substitution in titanomagnetite was controlled by kinetic or disequilibrium processes.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

Silicon in magnetite: High resolution microanalysis of magnetite-ilmenite intergrowths

Newberry

Peacor

Essene

et al. 1982

Contr. Mineral. and Petrol.

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Magnetite-ilmenite "oxidation-exsolution" intergrowths from an original titanomagnetite microphenocryst from an ash flow tuff unit have been studied using conventional transmission electron microscopy and analytical electron microscopy. Silicon has been found to be in solid solution in all of the magnetite studied and in some of the coexisting ilmenite. The average value in magnetite is 1.2wt.% Si, equivalent to solid solution of 9 mole % FezSiO4. Silicon is also present in very small silicate inclusions and as unusual Si-rich domains of uncertain origin in magnetite. The inclusions and domains may be irregularly distributed through the magnetite in sizes well below those resolvable with the electron microprobe. Microprobe analyses for Si in magnetite generally reflect these heterogeneities in addition to a component presumably in solid solution. The petrologic implications of the data can be assessed only when relevant thermochemical data become available and the distribution of Si in magnetite is better understood.

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Section: Interpretation and Discussionmentioning

confidence: 99%

Silicon in magnetite: High resolution microanalysis of magnetite-ilmenite intergrowths

Newberry

Peacor

Essene

et al. 1982

Contr. Mineral. and Petrol.

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“…Displacement of metal ions along the [111] direction leads to a lowering of Fd3m symmetry, for example F43m symmetry was reported in natural magnetite ( [3]; Table 1). Cation disorder Although many studies from the 1970's report "silica-bearing magnetite" (e.g., [17]), the term "silician magnetite" was attributed to Shiga [18], who refers to magnetite with >1 wt. % SiO 2 and depleted in other cations except ferrous and ferric ions in samples from the Kamaishi Cu-Fe skarn, Japan.…”

Section: Introductionmentioning

confidence: 99%

Silician Magnetite: Si–Fe-Nanoprecipitates and Other Mineral Inclusions in Magnetite from the Olympic Dam Deposit, South Australia

et al. 2019

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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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“…Silician magnetite occurs in various types of ore deposits with high-to low-temperature conditions, as summarized by Huberty et al [23] and Xu et al [25], including porphyry-type [26], skarn-type [6][7][8][16][17][18]27,28], banded iron formation (BIF) [23,25], and volcanic-related massive sulfide [29]. The highest value of SiO 2 content in magnetite (~8.9 wt %) is recognized in a porphyry-type deposit [26].…”

Section: Magnetite Ore-forming Conditionmentioning

confidence: 99%

“…The highest value of SiO 2 content in magnetite (~8.9 wt %) is recognized in a porphyry-type deposit [26]. Moreover, skarn-type deposits show a higher frequency in the appearance of silician magnetite and have considerably high SiO 2 contents, ranging from 3.2 to 6.5 wt % [6][7][8]16,17,27,28]. The two types are generally defined as intrusion-related magmatic-hydrothermal deposits involving relatively high-temperature and high-salinity fluids [30].…”

Section: Magnetite Ore-forming Conditionmentioning

confidence: 99%

Silician Magnetite from the Copiapó Nordeste Prospect of Northern Chile and Its Implication for Ore-Forming Conditions of Iron Oxide–Copper–Gold Deposits

et al. 2018

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Silica-bearing magnetite was recognized in the Copiapó Nordeste prospect as the first documented occurrence in Chilean iron oxide–copper–gold (IOCG) deposits. The SiO2-rich magnetite termed silician magnetite occurs in early calcic to potassic alteration zones as orderly oscillatory layers in polyhedral magnetite and as isolated discrete grains, displaying perceptible optical differences in color and reflectance compared to normal magnetite. Micro-X-ray fluorescence and electron microprobe analyses reveal that silician magnetite has a significant SiO2 content with small amounts of other “impure” components, such as Al2O3, CaO, MgO, TiO2, and MnO. The oscillatory-zoned magnetite is generally enriched in SiO2 (up to 7.5 wt %) compared to the discrete grains. The formation of silician magnetite is explained by the exchange reactions between 2Fe (III) and Si (IV) + Fe (II), with the subordinate reactions between Fe (III) and Al (III) and between 2Fe (II) and Ca (II) + Mg (II). Silician magnetite with high concentrations of SiO2 (3.8–8.9 wt %) was similarly noted in intrusion-related magmatic–hydrothermal deposits including porphyry- and skarn-type deposits. This characteristic suggests that a hydrothermal system of relatively high-temperature and hypersaline fluids could be a substantial factor in the formation of silician magnetite with high SiO2 contents.

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Silica-bearing magnetites

Cited by 22 publications

References 4 publications

Silicon in magnetite: High resolution microanalysis of magnetite-ilmenite intergrowths

Silicon in magnetite: High resolution microanalysis of magnetite-ilmenite intergrowths

Silician Magnetite: Si–Fe-Nanoprecipitates and Other Mineral Inclusions in Magnetite from the Olympic Dam Deposit, South Australia

Silician Magnetite from the Copiapó Nordeste Prospect of Northern Chile and Its Implication for Ore-Forming Conditions of Iron Oxide–Copper–Gold Deposits

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