Fe-Ti oxide micro-inclusions in clinopyroxene of oceanic gabbro: Phase content, orientation relations and petrogenetic implication

Ageeva, Olga; Habler, Gerlinde; Pertsev, A. N.; Abart, Rainer

doi:10.1016/j.lithos.2017.08.007

Cited by 12 publications

(11 citation statements)

References 38 publications

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“…At temperatures below ~ 600 °C, Ti-rich magnetite tends to exsolve ulvospinel. Magnetite-ulvospinel assemblages obtained from exsolution of Ti-rich magnetite have been described from oceanic gabbro before (Feinberg et al 2004;Ageeva et al 2017), but are not typical in the sample under study. Ulvospinel is stable only at low oxygen fugacity and tends to be oxidized otherwise.…”

Section: Implication Of Magnetite-ilmenite Intergrowthmentioning

confidence: 90%

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: Implication Of Magnetite-ilmenite Intergrowthmentioning

confidence: 90%

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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“…1c, d). The genesis of the ilmenite and ulvospinel lamellae has been discussed by Wenk et al (2011), Tan et al (2016), and Ageeva et al (2016Ageeva et al ( , 2017 and is not further addressed in this communication.…”

Section: Sample Petrographymentioning

confidence: 92%

“…The Fe-Ti oxides are present as large interstitial grains of magnetite and as micron-and sub-micron-sized inclusions in plagioclase and pyroxene. Detailed descriptions of the mineralogy and petrography of the gabbros with complex petrogenetic history (Samples L32-101-1, L2612-41, L2612-47) can be found in Pertsev et al (2015), Aranovich et al (2015) and Ageeva et al (2017).…”

Section: Sample Petrographymentioning

confidence: 99%

“…Oriented micro-inclusions of Fe-Ti oxide minerals such as magnetite, ulvospinel, hematite, and ilmenite hosted in rockforming silicate minerals are frequently observed in igneous and metamorphic rocks (Poldervaart and Gilkey 1954;Divljan 1960;Neumann and Christie 1962;Armbrustmacher and Banks 1974;Sobolev 1990;Usui et al 2006;Wenk et al, 2011;Biedermann, et al 2016;Ageeva et al 2016Ageeva et al , 2017.…”

Section: Introductionmentioning

confidence: 99%

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Crystallographic and shape orientations of magnetite micro-inclusions in plagioclase

Ageeva

Bian

Habler

et al. 2020

Contrib Mineral Petrol

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Plagioclase hosted, oriented magnetite micro-inclusions are a frequently observed phenomenon in magmatic and metamorphic rocks. Understanding the orientation relationships between these inclusions and the plagioclase host is highly relevant for interpreting paleomagnetic measurements. The systematics of the shape and crystallographic orientation relationships between needle- and lath-shaped magnetite micro-inclusions and their plagioclase host from oceanic gabbro were investigated using optical microscopy including universal stage measurements, scanning electron microscopy, and crystal orientation analysis by electron backscatter diffraction. The magnetite inclusions show preferred shape orientations following six well-defined directions and with specific crystallographic orientation relationships to the plagioclase host. These relationships are rationalized based on angular and dimensional similarities between the crystal structures of magnetite and plagioclase, which favor the parallel alignment of oxygen layers with similar lattice spacing in both phases. The parallel alignment of oxygen layers in plagioclase and magnetite can be traced back to the oriented nucleation of magnetite, which occurs by the accommodation of FeO6 octahedra in six-membered rings of SiO4 and AlO4 tetrahedra of the plagioclase structure. The orientation systematics of the magnetite micro-inclusions is related to four orientation variants for placing the FeO6 octahedra into the plagioclase structure.

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“…Furthermore, magnetite has a wide stability field, crystallizing in magmas in which the oxidation conditions extend below the FMQ buffer. For example, magnetite is common in oceanic gabbro and plagiogranite on the ocean floor (e.g., Ageeva et al, 2017), resulting in magnetic stripes on the ocean floor parallel to ridges, which was the evidence for the theory of ocean floor spreading in 1960s (i.e. Vine, 1966).…”

Section: Identification Of Igneous Rocks Potentially Associated With mentioning

confidence: 99%

Porphyry Copper Potential in Japan Based on Magmatic Oxidation State

Hattori

2018

Resource Geology

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The formation of large porphyry Cu deposits requires shallow intrusion of felsic stocks that are injected into the focused sites of the mineralization. The parental magmas for these igneous rocks are oxidized, with a fO2 above FMQ + 2 (2 logarithmic units above fO2 of fayalite‐magnetite‐quartz buffer), which enables the magmas to transport large amounts of S and metals. The Japanese islands contain continental and island‐arc magmatic belts of various ages, from Mesozoic to recent, that were formed in response to westward subduction of oceanic plates. Mesozoic–Paleocene magmatism formed arcs on the eastern margin of Eurasia before the opening of the Sea of Japan. The back‐arc rifting that formed the Sea of Japan separated these igneous rocks from Eurasia, with their relics exposed as volcano–plutonic belts in Japan. Among these, the San‐in belt is the only representative of an upper crustal section that includes magnetite‐bearing granitic rocks. The opening of the Sea of Japan was accompanied by the asthenospheric mantle upwelling and eruption of oceanic magma. This was followed by extensive Miocene submarine volcanic activity that formed the Green Tuff belt. The current configuration of the Japanese islands was established in Pliocene. Young arcs, such as the Kuril, Izu‐Bonin, and Ryukyu arcs, are largely composed of mafic magmas, with accompanying asthenospheric upwelling in back‐arc extension. As the asthenospheric mantle and associated magmas have a reduced fO2, below FMQ (fayalite‐magnetite‐quartz buffer), continual upwelling of asthenospheric mantle creates limited areas of potential porphyry Cu mineralization in Japanese islands. Possible prospective areas include young stratovolcanoes in Honshu and Kyushu islands. Fertile rocks that may be associated with porphyry Cu mineralization can be identified by evaluating their magmatic oxidation conditions through mineralogical and mineral chemistry studies.

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Fe-Ti oxide micro-inclusions in clinopyroxene of oceanic gabbro: Phase content, orientation relations and petrogenetic implication

Cited by 12 publications

References 38 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

Crystallographic and shape orientations of magnetite micro-inclusions in plagioclase

Porphyry Copper Potential in Japan Based on Magmatic Oxidation State

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