The first finding of corundum in exsolution structures of oxides in gabbroic rocks from the Polar Urals

Куликова, К. В.; Варламов, Д. А.

doi:10.1134/s1028334x06020206

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…Butcher and Merkle [29] proposed that corundum in titanomagnetite from the Upper Zone of the Bushveld Complex has exsolved directly from the solid solution at temperatures above 800 • C in response to a surplus of Al at the grain margins. Kulikova and Varlamov [100] came to a similar conclusion for the origin of corundum at the boundaries between ilmenite and its magnetite host in gabbroic rocks from the Malyko-Kharampe Complex (Polar Urals). In the LDC, the vast majority of corundum occurs in HCM intergrowths with magnetite and zinciferous hercynite (Figure 7), as opposed to single exsolutions.…”

Section: Formation Of Corundum Via the Oxidation Of Hercynitementioning

confidence: 61%

An Integrated Model for Ilmenite, Al-Spinel, and Corundum Exsolutions in Titanomagnetite from Oxide-Rich Layers of the Lac Doré Complex (Québec, Canada)

et al. 2018

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The titanomagnetite of the Lac Doré Complex, an Archean layered intrusion that is located in the Abitibi greenstone belt in Québec (Canada), contains a wide variety of exsolution textures, which are the remnants of a complex cooling history. In the present study, we reconstitute the decomposition stages of the original solid solution in order to explain the formation of ilmenite, Al-spinel (hercynite and gahnite), and corundum exsolutions in magnetite. This was conducted through a detailed mineralogical and textural examination and in situ determination of mineral chemistry. Our investigation reveals two discrete types of ilmenite exsolutions, which are ascribed, respectively, to the oxidation of ulvöspinel at temperatures above and below the magnetite-ulvöspinel solvus. Exsolutions of Al-spinel result from either a decrease in the solubility of the (FeZn)Al2O4 components upon cooling, or local excesses of Al and Zn due to the removal of ulvöspinel during the early oxidation. The origin of corundum is ascribed to the oxidation of pre-existing hercynite exsolutions. The trace element composition of the titanomagnetite indicates stratigraphic reversals in Cr, Mg, Co, Ti, and Si and important changes in redox conditions. We interpret this as a direct consequence of a major event of magma chamber replenishment, which strongly influenced the distribution of exsolutions.

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Section: Formation Of Corundum Via the Oxidation Of Hercynitementioning

confidence: 61%

An Integrated Model for Ilmenite, Al-Spinel, and Corundum Exsolutions in Titanomagnetite from Oxide-Rich Layers of the Lac Doré Complex (Québec, Canada)

et al. 2018

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“…Corundum and hematite are rarely associated in terrestrial rocks, but sometimes occur in Al-rich metamorphic rocks after bauxites and laterites (Feenstra et al , 2005 and references therein). Exsolution of hematite in gem-quality corundum of metamorphic or magmatic origin and reverse exsolution structure (corundum in hematite or another Fe-oxide minerals) are also rare phenomena (Feenstra et al , 2005 and references therein; Kulikova and Varlamov, 2006; Izokh et al , 2010). Fe-rich corundum, hibonite, dorrite-like minerals, Mn-Al-rich hematite and magnesioferrite have been found as a spongy aggregate in vugs from one of the ‘metacarbonate nuts’ of a burnt dump of the Kalinin coal mine, Donets coal basin, southeast Ukraine (Sharygin, 2010).…”

Section: Introductionmentioning

confidence: 99%

A hibonite-spinel-corundum-hematite assemblage in plagioclase-clinopyroxene pyrometamorphic rocks, Hatrurim Basin, Israel: mineral chemistry, genesis and formation temperatures

Sharygin

2018

MinMag

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The intergrowths of Fe-rich corundum + Al-rich hematite + spinel + hibonite have been found as an assemblage in a plagioclase-clinopyroxene rock (paralava, former hornfels) at the Hatrurim Basin, Hatrurim combustion metamorphic Formation. Most spinels show oriented exsolution structures and vary from (Mg0.75${\rm Fe}_{{\rm 0}{\rm. 25}}^{2 +} $)(Al1.80${\rm Fe}_{{\rm 0}{\rm. 20}}^{3 +} $)O4 (with exsolutions) to (Mg0.77${\rm Fe}_{{\rm 0}{\rm. 23}}^{2 +} $)(Al1.95${\rm Fe}_{{\rm 0}{\rm. 05}}^{3 +} $)O4 (homogeneous) indicating a tendency towards magnesioferrite and magnetite, and enrichment in NiO (up to 1.9 wt.%) and ZnO (up to 1.4 wt.%). Hibonite is Ti rich (TiO2 > 8 wt.%) and close to CaAl9Fe3+(Mg,Fe2+)TiO19. Corundum varies in Fe2O3 (4.2–11.8 wt.%). Hematite is also inhomogeneous and contains oriented exsolution structures of corundum. It shows variable concentrations of TiO2 (0.7–5.6 wt.%), Al2O3 (0.7–8.6 wt.%), Cr2O3 (0.2–1.5 wt.%), V2O3 (0.1–1.0 wt.%) and MgO (0.3–2.0 wt.%). Crystallization of this specific assemblage is assumed to be at 1000–1200°C using evaluations for the corundum hematite pair with reference to published experimental data. The active role of superheated oxidised volatiles is suggested during both crystallisation of this corundum-bearing association and host-rock transformation (melting event for hornfels → paralava).

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The first finding of corundum in exsolution structures of oxides in gabbroic rocks from the Polar Urals

Cited by 2 publications

References 2 publications

An Integrated Model for Ilmenite, Al-Spinel, and Corundum Exsolutions in Titanomagnetite from Oxide-Rich Layers of the Lac Doré Complex (Québec, Canada)

An Integrated Model for Ilmenite, Al-Spinel, and Corundum Exsolutions in Titanomagnetite from Oxide-Rich Layers of the Lac Doré Complex (Québec, Canada)

A hibonite-spinel-corundum-hematite assemblage in plagioclase-clinopyroxene pyrometamorphic rocks, Hatrurim Basin, Israel: mineral chemistry, genesis and formation temperatures

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