High resolution X–ray computed tomography and scanning electron microscopy studies of multiphase solid inclusions in Oman podiform chromitite: implications for post–entrapment modification

Yao, Yuan; Takazawa, Eiichi; Chatterjee, Sayantani; Richard, Antonin; Morlot, Christophe; Créon, Laura; AL–BUSAIDI, Salim; Michibayashi, Katsuyoshi

doi:10.2465/jmps.191008

Cited by 6 publications

(4 citation statements)

References 43 publications

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“…The similar nature of the silicate minerals (mostly amphibole, orthopyroxene and mica) included within newly formed chromite supports the involvement of a hydrated and silica‐rich component (Borisova et al, 2012; Rospabé et al, 2017, 2020; Rospabé, Ceuleneer, et al, 2019; Yao et al, 2020). Old chromite grains in some ophiolites are diamond‐bearing and were produced at depths greater than 400 km, and the mineral inclusions in such chromites may have more complex histories (e.g., Arai, 2010; Arai, 2013; Lian & Yang, 2019; Miura et al, 2012; Robinson et al, 2004; Yamamoto et al, 2009; Yang et al, 2007).…”

Section: The Boundary Between the Oceanic Crust And The Mantle In The...mentioning

confidence: 84%

The nature of the Moho beneath fast‐spreading centers: Evidence from the Pacific plate and Oman ophiolite

et al. 2022

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It is common knowledge that the Moho is the boundary between the crust and the Earth's mantle. Here we show along several seismic profiles through the Pacific Plate that a correlation exists between the strength of Moho reflections, crustal thickness, and water depth. Where the Moho can be detected clearly, the overlying oceanic crust is systematically thicker and the water depths are shallower. We suggest that two end‐members of oceanic crust exist in fast spreading environments: one thick, underlain by a clear Moho; the other thinner, without a Moho; with all intermediate situations. In the Oman ophiolite, the best‐preserved on‐land analogue of fossil oceanic lithosphere created by fast‐spreading, the boundary between the mantle peridotites and the lower crustal gabbros mainly consists of a dunitic transition zone (DTZ) ranging from a few meters to a few hundred meters in thickness. A sudden influx of seawater down to the base of the crust at the mid‐ocean ridge (MOR) results in the hydrous (re‐)melting of mantle peridotites, producing a dunitic residue at the crust–mantle boundary that represents the most reflective Moho. At the same time, the hydrous melting, in addition to the normal decompression melting, beneath the MOR, increases the thickness of the oceanic crust by enhancing magma production. In the absence of hydrous melting, the DTZ is thin or absent at the crust–mantle boundary, and instead the uppermost mantle harzburgite is intruded by gabbros, and/or the overlying crustal gabbro is intruded by numerous wehrlite bodies, which will be seismically gradational.

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Section: The Boundary Between the Oceanic Crust And The Mantle In The...mentioning

confidence: 84%

The nature of the Moho beneath fast‐spreading centers: Evidence from the Pacific plate and Oman ophiolite

et al. 2022

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“…10ac). The less heterogeneous compositions of the amphibole inclusions are probably due to their relatively simple genesis or less modification in enclosed environments since formation (e.g., Borisova et al, 2012;Yao et al, 2020;Su et al, 2021b).…”

Section: Amphibolementioning

confidence: 99%

“…Mantle sequences in both types of ophiolite exhibit similar lithologies, mainly consisting of spinel-facies peridotites, including harzburgite, lherzolite and dunite in decreasing abundance (Aldanmaz et al, 2009;Caran et al, 2010). Despite more than a century of study, the petrogenesis and significance of mantle peridotites in ophiolites remain highly debated, particularly due to the discovery of ultra-high pressure (UHP) and super-reduced (SuR) mineral phases in many ophiolites worldwide (e.g., Robinson et al, 2004Robinson et al, , 2015Yang et al, 2007Yang et al, , 2014Xiong et al, 2015Xiong et al, , 2022aYao et al, 2020;Dobrzhinetskaya et al, 2022;Rui et al, 2022). A brief summary of the debates on the origin of 'mantle' peridotites in ophiolites is presented below.…”

Section: Introductionmentioning

confidence: 99%

Mantle peridotites of ophiolites rarely preserve reliable records of paleo-oceanic lithospheric mantle

Su,

Pan,

Xiao

et al. 2023

Earth-Science Reviews

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“…Augé, 1986) are not investigated here. A secondary Cr-oxide corona surrounding a part of polymineralic inclusions was sometimes observed but is less common than in chromitites (Borisova et al, 2012;Yao et al, 2020).…”

Section: Diversity Of Silicate Inclusions In Dtz Chromitesmentioning

confidence: 99%

The Chicken and Egg Dilemma Linking Dunites and Chromitites in the Mantle–Crust Transition Zone beneath Oceanic Spreading Centres: a Case Study of Chromite-hosted Silicate Inclusions in Dunites Formed at the Top of a Mantle Diapir (Oman Ophiolite)

Rospabé

Ceuleneer

Guluche

et al. 2021

Journal of Petrology

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The mantle-crust boundary beneath oceanic spreading centres is a major chemical and thermal interface on Earth. Observations in ophiolites reveal that it is underlined by a dunitic transition zone (DTZ) that can reach a few hundred meters in thickness and hosting abundant chromitite ore bodies. The dunites have been deciphered as essentially mantle-derived in most ophiolitic massifs, i.e. reactional residues of interactions between peridotite and percolating melt(s). Although both dunite and chromitite in ophiolites have been the focus of many studies, the reasons of their systematic association remain unclear. In this study we have explored the inclusion content of the chromite grains disseminated in the dunites from the DTZ exposed in the Maqsad area of the Oman ophiolite where a former asthenospheric diapir is exposed. Similarly to chromite in chromitite ore bodies, disseminated chromite grains in dunites contain a great diversity of silicate inclusions. Based on the major and minor element composition of 1794 single silicate inclusions in chromites from 285 samples of dunite and associated rocks in the DTZ, we infer that the disseminated chromites formed by a similar “metallogenic” process to the chromitites, and that, as a whole, dunites from the DTZ actually represent the low grade endmember of a single, giant ore body. The nature of the silicate inclusions (amphibole and mica among others) enclosed in chromite grains in dunites from the Maqsad DTZ precludes their crystallization from an anhydrous primitive basaltic melt, and rather calls for a crystallization from a melt hybrid between common mafic melts and more exotic Si-, Na- and volatile-rich fluids. The hybrid parent medium of both dunites and chromitites results from the interaction between an asthenospheric diapir (the MORB source), and a colder, altered lithospheric lid and hydrothermal fluids responsible for this alteration. The excess silica in the hybrid melt is provided by the incongruent dissolution of enstatite from mantle harzburgite and/or from moderate degree of partial melting of the altered gabbroic crust. The chemical composition of the silicate inclusions is more variable when enclosed in the disseminated chromites than in the chromitites, suggesting a greater variability of melts and/or fluids fractions involved in the genesis of dunites than of chromite ores. Finally, the DTZ can be viewed as a metamorphic contact aureole between episodically rising asthenospheric diapirs and formerly accreted axial lithospheric lids. Our conclusion about the chicken and egg dilemma linking dunites and chromitites beneath oceanic spreading centres (i.e. Do the chromitites form in response to the formation of dunites or conversely?) is that the mantle dunitization itself is a potential way for the release of Cr and its re-concentration as chromite ores, and that in turn the competition between orthopyroxene (+/- plagioclase) and chromite fractionation during this fluid/melt/peridotite reactional process is responsible of the great mineralogical and chemical variability of the DTZ dunites.

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High resolution X–ray computed tomography and scanning electron microscopy studies of multiphase solid inclusions in Oman podiform chromitite: implications for post–entrapment modification

Cited by 6 publications

References 43 publications

The nature of the Moho beneath fast‐spreading centers: Evidence from the Pacific plate and Oman ophiolite

The nature of the Moho beneath fast‐spreading centers: Evidence from the Pacific plate and Oman ophiolite

Mantle peridotites of ophiolites rarely preserve reliable records of paleo-oceanic lithospheric mantle

The Chicken and Egg Dilemma Linking Dunites and Chromitites in the Mantle–Crust Transition Zone beneath Oceanic Spreading Centres: a Case Study of Chromite-hosted Silicate Inclusions in Dunites Formed at the Top of a Mantle Diapir (Oman Ophiolite)

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