Chemical variations of mineral inclusions in Neoproterozoic high-Cr chromitites from Egypt: Evidence of fluids during chromitite genesis

Khedr, Mohamed Zaki; Arai, Shoji

doi:10.1016/j.lithos.2015.11.029

Cited by 52 publications

(40 citation statements)

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“…Mineral inclusions in chromian spinel possibly provide important information about magmatic origin of spinels, because the primary silicate minerals outside spinel were easily altered during serpentinization and metamorphism (Ahmed & Arai, ; Arai & Matsukage, ; Khedr & Arai, ). Inclusions in chromian spinel in the Western Khoy chromitites are olivine, diopside, and PGE‐bearing sulfide, whereas those from the Eastern Khoy chromitites are mainly Na‐bearing diopside, pargasite, and rutile.…”

Section: Discussionmentioning

confidence: 99%

“…The formation of podiform chromitite deposits has been discussed for decades (e.g. Arai, ; Arai & Miura, ; Arai & Yurimoto, ; Khedr & Arai, ; Zhou et al, ). The most accepted hypothesis for the formation of podiform chromitites is the mantle‐melt interaction and subsequent magma mixing (Arai, ; Arai & Yurimoto, ; Zhou et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…It is widely accepted that the high‐Cr chromitites were in equilibrium with boninitic or Mg‐rich andesitic melts, while high‐Al chromitites are interpreted as having crystallized from MORB or back‐arc basin basaltic melts (e.g. Arai, ; Khedr & Arai, ; Miura et al, ; Moghadam et al, ; Zhou & Robinson, ; Zhou et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Finally, the Western Khoy chromitites are possibly formed at several stages during arc growth: the moderately high‐Cr# chromitites (Barajouk and Hessar) were generated by reaction between the IAT melts (a first stage melt) and depleted harzburgites; these tholeiitic melts with low H 2 O content are abundant in a subduction initiation (a nascent arc) during extension in a forearc region (Dilek & Thy, ; Khedr & Arai, ; Moghadam et al, , ; Whattam & Stern, ). But high‐Cr# chromitites (Chuchak A and C) from the Western Khoy ophiolite have been crystallized from boninitic melts (a second stage melt) in a supra‐subduction zone environment (a mature arc stage) (Figure ).…”

Section: Discussionmentioning

confidence: 99%

“…The mantle sections of many ophiolitic belts are highly charged with podiform chromitites, despite ophiolite ages, from Neoproterozoic to Mesozoic ages (e.g. Arai, ; Arai, Kadoshima, & Morishita, ; Arai & Miura, ; González‐Jiménez et al, , ; Khedr & Arai, ; Pearce, Barker, Edwards, Parkinson, & Leat, ). Since chromian spinels (or chromites) are often among the first phases to crystallize from a magma, they have the potential to offer an important insight into the petrogenesis of primitive magmas.…”

Section: Introductionmentioning

confidence: 99%

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Mineral chemistry and petrogenesis of chromitites from theKhoy ophiolite complex,NorthwesternIran:Implications for aggregation of two ophiolites

et al. 2017

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The Khoy ophiolitic complex in Northwestern Iran is a part of the Tethyan ophiolite belt, and is divided into two sections: the Eastern ophiolite in Qeshlaq and Kalavanes (Jurassic–Cretaceous) and the Western ophiolite in Barajouk, Chuchak and Hessar (Late Cretaceous). Our chromitites can be clearly classified into two groups: high‐Al chromitites (Cr# = 0.38–0.44) from the Eastern ophiolite, and high‐Cr chromitites (Cr# = 0.54–0.72) from the Western ophiolite. The chromian spinels in high‐Al chromitite include primary mineral inclusions mainly as Na‐bearing diopside and pargasite with subordinate rutile and their formation was probably related to reaction between a MORB (mid‐ocean‐ridge basalt)‐like melt with depleted harzburgite, possibly in a back‐arc setting. Their host harzburgites contain clinopyroxene with higher contents of Al2O3, Na2O, Cr2O3, and TiO2 relative to Western harzburgites and are possibly residue after moderate partial melting (~15 %) whereas the Western harzburgite is residue after high partial melting (~25 %). The chromian spinel in the Western Khoy chromitites contains inclusions such as clinopyroxene, olivine and platinum group mineral‐bearing sulfides. These Western chromitites were possibly formed at two stages during arc growth and are divided into the moderately high‐Cr# chromitites (Barajouk and Hessar) and the high‐Cr# chromitites (Chuchak A and C). The former crystallized from island‐arc‐tholeiite (IAT) melts during reaction with the host depleted harzburgites, whereas the latter crystallized from boninitic melts (second stage melt) during reaction with highly depleted harzburgite in a supra‐subduction‐zone environment. Based on the mineral chemistry of chromian spinels, pyroxenes, and mineral inclusions, the chromitites and the host peridotites from the Eastern and Western Khoy ophiolites were formed in a back‐arc basin and arc‐related setting, respectively. The Khoy ophiolitic complex is a tectonic aggregate of the two different ophiolites formed in two different tectonic settings at different ages.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mineral chemistry and petrogenesis of chromitites from theKhoy ophiolite complex,NorthwesternIran:Implications for aggregation of two ophiolites

et al. 2017

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Spinel chemistry and geochemistry of serpentinite of North Delhi fold belt, Rajasthan: Constraining the petrogenesis and geodynamics of northwestern Indian shield

et al. 2020

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The western margin of the north Delhi fold belt, Rajasthan is mostly covered by the thick alluvium-sand cover of the Thar Desert. However, a study on a cluster of scattered and deformed serpentinite bodies exposed in the small opencast quarries are presented here. Though alteration and absence of primary phases possess constraints over petrogenesis, but, the accessory, anhedral spinel chemistry aids in the genetic reconstruction. The unaltered core part of the spinel that is, the Al-chromite (avg. 45.2 wt% Cr 2 O 3 ), followed by ferrit chromite (avg. 32.3 wt% Cr 2 O 3 ) inner rim and magnetite towards the outer rim is the character of spinels present in the host, where the chemistry of the core part is used exclusively. This core part of spinel preserves the primary mantle signature and attests the forearc peridotite character and a similar subduction-related trait is followed by the whole-rock major oxide proxies.Cumulative petrological, whole-rock geochemistry, and mineral chemical signature unequivocally advocate towards a harzburgitic protolith, an arc peridotitic character, and presence of ancient forearc environment. The present communication is the first to describe the detailed characterization of serpentinite bodies with a possible linkage towards the presence of ancient oceanic slices in the north Delhi fold belt, Rajasthan, NW India.

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Platinum‐group mineral and silicate inclusions in the low‐Al chromitites of the Manipur ophiolite, northeast India: Implications on Cr‐PGE mineralization in nascent subduction zone settings

Singh

Bidyananda

Kapsiotis³

2022

Geological Journal

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Low‐Al chromitites from the Manipur ophiolite contain a wide range of mineral inclusions, including hydrous and anhydrous silicates, sulphides, and platinum group minerals (PGM). The common inclusions are primary silicates, such as clinopyroxene, orthopyroxene and secondary silicate inclusions, such as chlorite, serpentine, and garnet. These inclusions are small (<30 μm in PGM, <100 μm in silicates) and randomly distributed throughout their host chromite grains. The shape and texture indicate some inclusions (clinopyroxene, orthopyroxene, PGMs) trapped during the magmatic stage and most inclusions (chlorite, serpentine, and uvarovite) trapped during recrystallization of chromite. Clinopyroxene was discrete inside the chromite, with Cr2O3 content ranging from 0.62 to 1.77 wt.%, and Al2O3 varying between 0.96 to 1.63 wt.%. Orthopyroxene is enstatite (En93Wo2Fs4), Cr2O3 varies from 0.58 to 1.8 wt.% and the minor amount of CaO (0.41–0.81 wt.%), and Al2O3 (0.58–0.83 wt.%). Uvarovite is present in two forms: discrete crystal inclusions (anhydrous) in chromites and fractures (hydrous) as fillings. The chlorite occurs as lath shaped, and patchy phase is Cr‐rich variety ‐ kammererite (clinochlore) and penninite with variable Cr2O3 (0.22–7.25 wt.%) and FeO (2.5–3.9 wt.%). The PGM in the studied chromite are laurite (Ru, Os, Ir)S2. The parental melts of chromitites had low TiO2 (0.16–0.48 wt.%) and Al2O3 (10.18–14.58 wt.%) contents, and primary mineral inclusions, suggesting an arc‐like geochemical affinity, and the estimated melt composition is comparable with that of boninitic magma.

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Chemical variations of mineral inclusions in Neoproterozoic high-Cr chromitites from Egypt: Evidence of fluids during chromitite genesis

Cited by 52 publications

References 69 publications

Mineral chemistry and petrogenesis of chromitites from theKhoy ophiolite complex,NorthwesternIran:Implications for aggregation of two ophiolites

Mineral chemistry and petrogenesis of chromitites from theKhoy ophiolite complex,NorthwesternIran:Implications for aggregation of two ophiolites

Spinel chemistry and geochemistry of serpentinite of North Delhi fold belt, Rajasthan: Constraining the petrogenesis and geodynamics of northwestern Indian shield

Platinum‐group mineral and silicate inclusions in the low‐Al chromitites of the Manipur ophiolite, northeast India: Implications on Cr‐PGE mineralization in nascent subduction zone settings

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