Co-occurrence of compositionally variable chromitites in the Sabzevar ophiolite, NE Iran

Eslami, Alireza; Grieco, G.; Bussolesi, Micol; Ichiyama, Yuji; Lenaz, Davide; Skogby, Henrik; Kutyrev, Anton V.; Cavallo, Alessandro; Khedr, Mohamed Zaki

doi:10.1016/j.lithos.2023.107133

Cited by 1 publication

(5 citation statements)

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“…The data and ranges of chromite from the low-Ti tholeiitic lavas/melts of the Kamchatkan ophiolite (Far East) and Manihiki Plateau (SW Pacific) are from Portnyagin et al [52] and Golowin et al [53], respectively. Data of chromite in chromitites [17,41] and ultramafic rocks [40] from Sartohay ophiolitic mélange, and in chromitites from Luobusa [49], Oman [48], Iran [10], and Egypt [24] are shown for comparison. Abbreviation: BON = boninite, IAT = island-arc tholeiite, MORB = mid-ocean ridge basalt, OIB = ocean island basalt.…”

Section: Silicate Mineral Inclusions In Chromitementioning

confidence: 99%

“…Primary silicate mineral inclusions are frequently encountered in chromite, with documented occurrences reported in podiform chromitites from Oman [56]; Sabzevar in Iran [10]; Eastern Desert of Egypt [24]; and Luobusa [57], Zedang [58], and Zunhua [16] in China. Various hypotheses on the origin of silicate mineral inclusions embedded in chromite have been proposed based on the differences in inclusion sizes, morphologies, distribution, and coexistence relationships.…”

Section: The Genesis Of Silicate Inclusionsmentioning

confidence: 99%

“…Chromite can be used to constrain the nature of parental melts formed in different tectonic environments [10,23]. The Al 2 O 3 and TiO 2 concentrations in chromite are directly correlated with the composition of the parental melt, as Al and Ti experience very little change during subsolidus re-equilibration between chromite and inclusions due to their low diffusivity [51,76].…”

Section: Constraints For Parental Melts Of Chromititementioning

confidence: 99%

“…The mechanism for the origin of podiform chromitites remains debatable, with various models proposed, including fractional crystallization [1], partial melting [2], fluid-related models [3], deep mantle mineralization models related with UHP (ultra-high pressure) minerals [4][5][6], and rheomorphic model associated with the localization of plastic flow in the dunite [7][8][9]. The most prevalent petrogenetic model is melt-peridotite interaction and subsequent melt mixing and/or mingling [10][11][12]. Arai and Miura [13] noted that mixing melts with different silica components is an essential process to precipitate chromite during the early stage of magmatic crystallization.…”

Section: Introductionmentioning

confidence: 99%

“…The chemical composition of chromite serves as a valuable tool for elucidating the characteristics of the parental melt in which the chromite crystallized [10,23]. The trapped micromelt inclusions are also valid petrogenetic indicators for the parental melt of chromitites and peridotites because host chromite is resistant to modification during post-magmatic processes [24].…”

Section: Introductionmentioning

confidence: 99%

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Genesis of the Sartohay Podiform Chromitite Based on Microinclusions in Chromite

Wen,

Zhu

2024

Minerals

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Here, we present a petrographic and microanalytical study of microinclusions in chromite from podiform chromitites hosted by the Sartohay ophiolitic mélange in west Junggar, northwestern China, to investigate the parental magma evolution and chromitite genesis. These silicate inclusions comprise olivine, enstatite, diopside, amphibole, and Na-phlogopite. Their morphological characteristics suggest that most inclusions crystallized directly from the captured melt, with a few anhydrous inclusions (olivines and pyroxenes) as solid silicates trapped during the chromite crystallization. Equilibrium pressure–temperature conditions of coexisting enstatite–diopside inclusions are 8.0–21.6 kbar, and 874–1048 °C. The high Na2O and TiO2 contents of hydrous minerals indicate that the parental magma of chromitites was hydrous and enriched in Mg, Na, Ca, and Ti. The calculated Al2O3 content and FeO/MgO ratio of the parental melts in equilibrium with chromite showed MORB affinity. However, the TiO2 values of parental melts, TiO2 contents of chromite, and estimated fO2 values for chromitites (1.3–2.0 log units above the FMQ buffer) evoked parental MORB-like tholeiitic melts. The composition of olivine inclusion was determined, and it was revealed that the primary melts of the Sartohay podiform chromitites had MgO contents of ~22.7 wt %. This aligns with the observed high magnesian signature in mineral inclusions (Fo = 96–98 in olivine, Mg# = 0.91–0.97 in diopside, and Mg# = 0.92–0.97 in enstatite). We propose that Sartohay podiform chromitites initially formed through the mixing/mingling of primary hydrous Mg-rich melt and the evolved MORB-like melt derived from the melt–peridotite reaction in the upper mantle. In this process, the continuous crystallization of chromite captured micro-silicate mineral inclusions, finally leading to the formation of the Sartohay podiform chromitites.

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