Stability of Fe5O6 and its relation to other Fe-Mg-oxides at high pressures and temperatures

Woodland, Alan B.; Uenver‐Thiele, Laura; Ballaran, Tiziana Boffa; Miyajima, Nobuyoshi; Rosbach, Kevin; Ishii, Takayuki

doi:10.2138/am-2022-8370

Cited by 4 publications

(5 citation statements)

References 32 publications

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“…Nevertheless, twinning on the {311} planes in magnetite can also result from the retrograde reaction of other iron oxide phases such as Fe 5 O 6 (Woodland et al 2023). On the other hand, the {100} and {113} lamellae in our recovered defect magnetite, which we interpret to have formed from a hp-O 4 phase at P and T (see above), can also help to distinguish one precursor candidate from another.…”

Section: Discussionmentioning

confidence: 70%

“…Analysis of diffraction patterns (Online Materials Fig. (Lavina and Meng 2015;Woodland et al 2015Woodland et al , 2023 were identified in the powder XRD pattern. Its presence might be also attributed to a small degree of reduction during the experiment.…”

Section: Experimental Run Productsmentioning

confidence: 99%

“…3c), which is consistent with the orientation of {113} twins. The twinning along {113} usually reflects a back reaction from a galena-like archetype structure belonging to the lillianite homologies series (Makovicky 1977) and as such may result from the backreaction of a hp-phase like Fe 4 O 5 or Fe 5 O 6 (Schollenbruch et al 2011;Woodland et al 2012Woodland et al , 2023Myhill et al 2016). Since the lamellae within the magnetite of sample Z1953o are not only on the {113} plane but also on the {100} plane and Fe 3 (Fe,Al) 4 O 9 is quenchable without any retrograde microtextures, we interpreted this defect magnetite (dmt) phase to be indicative of a previous high-P orthorhombic O 4 -polymorph (e.g., Haavik et al 2000).…”

Section: Appearance Of a Hp-polymorphmentioning

confidence: 99%

“…Previous experimental studies on the phase relations of spinel-structured oxides have demonstrated that their stability is often restricted to pressures corresponding to the upper mantle (e.g. Schollenbruch et al 2011;Woodland et al 2012;Uenver-Thiele et al 2017a, 2017bIshii et al 2014Ishii et al , 2015. At certain high-pressure (high-P) and high-temperature (high-T) conditions the spinel-structured phase can i) break down into its constituent oxides (e.g.…”

Section: Introductionmentioning

confidence: 99%

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High P-T phase relations of Al-bearing magnetite: Post-spinel phases as indicators for P-T conditions of formation of natural samples

Uenver-Thiele,

Woodland,

Miyajima

et al. 2024

American Mineralogist

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The phase relations of Al-bearing magnetite were investigated between 6–22 GPa and 1000–1550 °C using a multi-anvil apparatus. This study demonstrates that the spinel-structured phase persists up to ~9–10 GPa at 1100–1400 °C irrespective of the amount of hercynite (FeAl2O4) component present (20, 40, or 60 mol%). At ~10 GPa, the assemblage Fe2(Al,Fe)2O5 + (Al,Fe)2O3 forms and remains stable up to 16–20 GPa and 1200–1550 °C. Fe2(Al,Fe)2O5 adopts the CaFe3O5-type structure with the Cmcm space group. At 18–22 GPa and T >1300 °C the assemblage Fe3(Fe,Al)4O9 + (Al,Fe)2O3 becomes stable. Fe3(Fe,Al)4O9 is isostructural with Fe7O9, having the monoclinic structure of the C2/m space group. At T <1300 °C, Fe3(Fe,Al)4O9 + (Al,Fe)2O3 gives way to the assemblage of a hp-Fe(Fe,Al)2O4 + (Al,Fe)2O3. This hp-Fe(Fe,Al)2O4 phase is unquenchable; a defect-bearing spinel-structured phase was recovered instead, and it contained numerous lamellae parallel to {100} or {113} planes and notably less Al than the initial starting composition. While low-pressure spinel can have a complete solid solution between Fe3+-Al, the post-spinel phases have only very limited Al solubility, with a maximum of ~0.1 cpfu Al in hp-Fe(Fe,Al)2O4, ~0.3 cpfu in Fe2(Fe,Al)2O5, and ~0.4 cpfu in Fe3(Fe,Al)4O9, respectively. As a result, the phase relations of Fe(Fe0.8Al0.2)2O4 can also be applied to bulk compositions richer in Al with the only difference being that larger amounts of an (Al,Fe)2O3 phase are present. Coexisting rhombohedral-structured phases demonstrate that the binary miscibility gap established at low pressure between hematite and corundum is still valid up to 20 GPa. Since iron oxides (e.g., magnetite) with variable Al contents are found in extraterrestrial rocks or as inclusions in diamond, constraints on their high-P-T-fO2 stability might help unravel their formation conditions.

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Section: Discussionmentioning

confidence: 70%

Section: Experimental Run Productsmentioning

confidence: 99%

Section: Appearance Of a Hp-polymorphmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High P-T phase relations of Al-bearing magnetite: Post-spinel phases as indicators for P-T conditions of formation of natural samples

Uenver-Thiele,

Woodland,

Miyajima

et al. 2024

American Mineralogist

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“…Due to the small grain size of these particles (< 1 µm), we were not able to quantitatively analyze this phase. However, recent high-pressure experiments on the FeO-Fe 3 O 4 system revealed that at pressures above about 8-9 GPa two other phases, namely Fe 4 O 5 and Fe 5 O 6, exist, whereby at constant P and T, but moderately increasing ƒ O2 , wüstite (Fe 1-x O) is followed by Fe 5 O 6 and then Fe 4 O 5 and still later Fe 2 O 3 (Lavina et al 2011;Lavina and Meng 2015;Myhill et al 2016;Hikosaka et al 2019;Woodland et al 2022).…”

Section: Na-rich Shock Vein Within a Pre-existing Analcime Veinletmentioning

confidence: 99%

Newly detected shock-induced high-pressure phases formed in amphibolite clasts of the suevite breccia (Ries impact crater, Germany): Liebermannite, kokchetavite, and other ultrahigh-pressure phases

Stähle

Schwarz

et al. 2022

Contrib Mineral Petrol

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Amphibolite clasts in the suevite of the Ries impact crater contain shock-induced melt veins (SMVs) with high-pressure phases such as majoritic garnet, jadeitic clinopyroxene and others. In addition, heat conduction from hot SMVs into adjacent rock portions locally produced further high P–T melt pools. These melts were preferentially generated in rock domains, where the SMVs cross older (‘pre-Ries’) veinlets with analcime or prehnite and larger grains of sericitized plagioclase. Melting of such chemically different local bulk systems (Na-, Ca-, Ca-Na- and K-Na-rich) was facilitated by low solidus temperatures of the original secondary OH-bearing phases. From the resulting shock-induced melts, liebermannite, kokchetavite, jadeite, nonstoichiometric and albitic jadeite, grossular, vuagnatite, lawsonite + coesite, and clinozoisite crystallized during pressure release. Vuagnatite is now proven to be a genuine high-pressure phase. Its ubiquitous distance of 20–35 μm from the hot shock veins suggests a temperature sensitivity typical for an OH-bearing phase. In local Na-rich melts albitic jadeite appears instead of the assemblage jadeite + SiO2. Liebermannite, a dense polymorph of K-feldspar was identified by Raman spectroscopy. After stishovite, liebermannite constitutes the second known high-pressure phase in the Ries that contains silicon exclusively in six-fold coordination. The KAlSi3O8-polymorph kokchetavite was formed in alkali-rich melt glasses. Pressure and temperature values in the range of about 8–11 GPa and ~ 800–1100 °C were estimated from the chemical compositions of locally occurring majoritic garnets (Si = 3.21–3.32 and 3.06–3.10 apfu), respectively, and the presence of fine-grained aggregates of lawsonite and coesite. Generally, the neighboring areas of the veins are characterized by a sequence of variable high-pressure phases documenting strongly falling P–T conditions with increasing distance from the vein. These novel features enlighten the dynamic event during passage of a shock wave.

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Thermodynamics of mantle minerals – III: the role of iron

Stixrude,

Lithgow-Bertelloni

2024

Geophysical Journal International

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Summary We expand the scope of HeFESTo by encompassing the rich physics of iron in the mantle, including the existence of multiple valence and spin states. In our previous papers, we considered iron only in its most common state in the mantle: the high-spin divalent (ferrous) cation. We now add ferric iron end-members to six phases, as well as the three phases of native iron. We also add low-spin states of ferrous and ferric iron and capture the behavior of the high-spin to low-spin transition. Consideration of the multi-state nature of iron, unique among the major elements, leads to developments of our theory, including generalization of the chemical potential to account for the possibility of multiple distinguishable states of iron co-existing on a single crystallographic site, the effect of the high-spin to low-spin transition on seismic wave velocities in multi-phase systems, and computation of oxygen fugacity. Consideration of ferric iron also motivates the addition of the chromia component to several phases, so that we now consider the set of components: Ca, Na, Fe, Mg, Al, Si, O, and Cr (CNFMASO+Cr). We present the results of a new global inversion of mineral properties and compare our results to experimental observations over the entire pressure-temperature range of the mantle and over a wide range of oxygen fugacity. Applications of our method illustrate how it might be used to better understand the seismic structure, dynamics, and oxygen fugacity of the mantle.

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Stability of Fe5O6 and its relation to other Fe-Mg-oxides at high pressures and temperatures

Cited by 4 publications

References 32 publications

High P-T phase relations of Al-bearing magnetite: Post-spinel phases as indicators for P-T conditions of formation of natural samples

High P-T phase relations of Al-bearing magnetite: Post-spinel phases as indicators for P-T conditions of formation of natural samples

Newly detected shock-induced high-pressure phases formed in amphibolite clasts of the suevite breccia (Ries impact crater, Germany): Liebermannite, kokchetavite, and other ultrahigh-pressure phases

Thermodynamics of mantle minerals – III: the role of iron

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