Variation of Iron Species in Plagioclase Crystals by X‐ray Absorption Fine Structure Analysis

Nakada, Ryoichi; Sato, Masahiko; Ushioda, Masashi; Tamura, Yujiro; Yamamoto, Shinji

doi:10.1029/2018gc008131

Cited by 10 publications

(11 citation statements)

References 48 publications

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“…Finally, the enhancement of Fe uptake with increasing fO 2 reflects the Fe 3+ /FeO T ratio in the melt coupled with the preferential substitution of Fe 3+ for Al 3+ on the T site (Lundgaard and Tegner 2004). Plagioclase from gabbroic rocks usually contains both ferric and ferrous iron, and the Fe 3+ /FeO T ratio is typically in the range of 0.4-0.7 (Nakada et al 2019).…”

Section: Mass Balance Considerations For Precipitation From the Plagioclase Hostmentioning

confidence: 99%

Formation pathways of oriented magnetite micro-inclusions in plagioclase from oceanic gabbro

Bian

Ageeva

Rečnik

et al. 2021

Contrib Mineral Petrol

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Plagioclase hosted needle- and lath-shaped magnetite micro-inclusions from oceanic gabbro dredged at the mid-Atlantic ridge at 13° 01–02′ N, 44° 52′ W were investigated to constrain their formation pathway. Their genesis is discussed in the light of petrography, mineral chemistry, and new data from transmission electron microscopy (TEM). The magnetite micro-inclusions show systematic crystallographic and shape orientation relationships with the plagioclase host. Direct TEM observation and selected area electron diffraction (SAED) confirm that the systematic orientation relations are due to the alignment of important oxygen layers between the magnetite micro-inclusions and the plagioclase host, a hypothesis made earlier based on electron backscatter diffraction data. Precipitation from Fe-bearing plagioclase, which became supersaturated with respect to magnetite due to interaction with a reducing fluid, is inferred to be the most likely formation pathway. This process probably occurred without the supply of Fe from an external source but required the out-diffusion of oxygen from the plagioclase to facilitate partial reduction of the ferric iron originally contained in the plagioclase. The magnetite micro-inclusions contain oriented lamellae of ilmenite, the abundance, shape and size of which indicate high-temperature exsolution from Ti-rich magnetite constraining the precipitation of the magnetite micro-inclusions to temperatures in excess of ~ 600 °C. This is above the Curie temperature of magnetite, and the magnetic signature of the magnetite-bearing plagioclase grains must, therefore, be considered as the thermoremanent magnetization.

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Section: Mass Balance Considerations For Precipitation From the Plagioclase Hostmentioning

confidence: 99%

Formation pathways of oriented magnetite micro-inclusions in plagioclase from oceanic gabbro

Bian

Ageeva

Rečnik

et al. 2021

Contrib Mineral Petrol

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“…Although chemical shifts in different oxidation states of Fe were successfully observed by present SX-SAS method, more fine separated structures of energy states than Fig. 6 have been reported by EELS and XAFS experiments [ 16 , 19 ]. As the energy resolution of this method depends on the resolution of SXES, a further development of SXES spectrometer is necessary.…”

Section: Resultsmentioning

confidence: 91%

Analytical technique for self-absorption structure of iron L-emission spectra obtained by soft X-ray emission spectrometer

et al. 2022

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The method deriving the L self-absorption spectrum from Lα,β emission spectra obtained at different accelerating voltages has been optimized for analyzing the chemical state of Fe in solid materials. Fe Lα,β emission spectra obtained are fitted using Pseudo-Voigt functions and normalized by the integrated intensity of each Fe Ll line, which is not affected by L2,3 absorption edge. The self-absorption spectrum is calculated by dividing the normalized intensity profile collected at low accelerating voltage by that collected at a higher accelerating voltage. The obtained profile is referred to as soft X-ray self-absorption structure (SX-SAS). This method is applied to six Fe-based materials (Fe metal, FeO, Fe3O4, Fe2O3, FeS and FeS2) to observe different chemical states of Fe in those materials. By comparing the self-absorption spectra of iron oxides one can observe the L3 absorption peak structure shows a shift to the higher energy side as ferric (3+) Fe increases with respect to ferrous (+2) Fe. The intensity profiles of self-absorption spectra of metallic Fe and FeS2 shows shoulder structures between the L3 and L2 absorption peaks, which were not observed in spectra of Fe oxides. These results indicate that the SX-SAS technique is useful to examine X-ray absorption structure as a means to understand the chemical states of transition metal elements. Mini abstract: The method deriving the L self-absorption spectrum from L-emission spectra obtained using EPMA-SXES technique has been optimized for analyzing the chemical state of Fe in solid materials, and named as soft X-ray self-absorption structure (SX-SAS). This technique is useful to examine chemical states of transition metal elements as XAFS experiment.

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“…8b, which follows that of the Al content across the lamellae. This may result from the fact that Fe 2+/3+ can be incorporated in the tetrahedral position re- placing Al 3+ (Makada et al, 2019). The Na and K content is increased in the Ca-poor lamellae (Fig.…”

Section: Lamellae and Local Domainsmentioning

confidence: 97%

The hierarchical internal structure of labradorite

Götz

Kleebe²,

Kolb³

2022

Eur. J. Mineral.

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Abstract. The different structural features of labradorite and its incommensurate atomic structure have long been in the eye of science. In this transmission electron microscopy (TEM) study, all of the structural properties of labradorite could be investigated on a single crystal with an anorthite–albite–orthoclase composition of An53.4Ab41.5Or5.1. The various properties of labradorite could thus be visualized and connected to form a hierarchical structure. Both albite and pericline twins occur in the labradorite. The size of alternating Ca-rich and Ca-poor lamellae could be measured and linked to the composition and the color of labradorescence. Furthermore, a modulation vector of 0.0580(15)a* + 0.0453(33)b* − 0.1888(28)c* with a period of 3.23 nm was determined. The results indicate an eα labradorite structure, which was achieved by forming Ca-rich and Ca-poor lamellae. The average structure and subsequently the incommensurate crystal structure were solved with a three-dimensional electron diffraction (3DED) data set acquired with automated diffraction tomography (ADT) from a single lamella. The results are in good agreement with the structure solved by X-ray diffraction and demonstrate that 3DED–ADT is suitable for solving even incommensurate structures.

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Variation of Iron Species in Plagioclase Crystals by X‐ray Absorption Fine Structure Analysis

Cited by 10 publications

References 48 publications

Formation pathways of oriented magnetite micro-inclusions in plagioclase from oceanic gabbro

Formation pathways of oriented magnetite micro-inclusions in plagioclase from oceanic gabbro

Analytical technique for self-absorption structure of iron L-emission spectra obtained by soft X-ray emission spectrometer

The hierarchical internal structure of labradorite

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