Fingerprints of metamorphism in chromite: New insights from minor and trace elements

Colás, Vanessa; Gonzáléz-Jiménez, José María; Griffin, William L.; Fanlo, Isabel; Gervilla, Fernando; O’Reilly, Suzanne Y.; Pearson, Norman J.; Kerestedjian, Thomas; Proenza, Joaquín A.

doi:10.1016/j.chemgeo.2014.10.001

Cited by 102 publications

(115 citation statements)

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“…The blocking temperatures of divalent ions are also lower than those of trivalent ions [23], and therefore, the increased frequency and prolonged exchange of divalent ions between the core and rim of Cr-spinel can destroy the already formed zonation texture. It is suggested that the re-equilibration of spinel with adjacent silicate restricts the application of spinel to investigate igneous processes [15,23,100,101]. Thus, the trivalent ions may be relatively appropriate, especially for olivine-hosted spinel (Figure 6a), to trace the original composition of spinel (Figure 7a,b).…”

Section: Inducement Of Elemental Exchangementioning

confidence: 99%

“…The most common zoning texture in Cr-spinels is characterized by Al-and Mg-rich cores and Cr-and Fe-rich rims, referred to as "normal zonation" [7][8][9]. The normally zoned Cr-spinels have been reported in ophiolites [10], layered mafic-ultramafic complexes [11], komatiites [12], mantle xenoliths [13,14], and metamorphosed ultramafic massifs [15]. Their formation is generally ascribed to high temperature hydrothermal alteration [16] or metamorphism [15,17], evidenced by the presence of secondary phases such as chlorite and antigorite surrounding the Cr-spinel or relict magnetite [15,18,19].…”

Section: Introductionmentioning

confidence: 99%

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Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton

Bai

Xiao

et al. 2018

Minerals

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Abstract:We conducted petrological and mineral chemistry investigations of Cr-spinel in ultramafic rocks of the Yanmenguan mafic-ultramafic complex in the North China Craton. The Cr-spinel grains occur as inclusions in enstatite, tschermakite, phlogopite, and olivine, or as interstitial grains among the aforementioned silicate minerals, and show concentric or asymmetrical textures. Back-scattered electron and elemental images and compositional profiles of the spinel grains indicate the presence of Cr-and Fe-rich cores and Al-and Mg-rich rims. The host silicate minerals display a decrease in Al and Mg contents accompanied by an increase in Cr and Fe away from the spinel. These textures and compositional variations suggest that subsolidus elemental exchange more likely gave rise to the compositional zonation, resulting in the transfer of Al and Mg from the silicate minerals to the spinel. The Mn, Ni, and Ti contents in spinel and the major elements of olivine-hosted spinel are relatively stable during subsolidus elemental diffusion and thus are more reliable tracers of primary high-temperature processes. The temperature estimates reveal that the subsolidus diffusion might have occurred at 600-720 • C, which could be linked to the regional metamorphic event.

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Section: Inducement Of Elemental Exchangementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton

Bai

Xiao

et al. 2018

Minerals

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“…In most cases the oriented Mg-silicates lamellae appear to preferentially develop at the boundaries not in the interior of the Cr-spinel grains, which is against their formation due to diffusion of components from the Cr-spinel lattice. In fact, petrographic evidence suggests that the zoning observed in Cr-spinel is not a primary feature; but a replacement texture obtained as a result of reaction that proceeded from the outside to the inside of the affected Cr-spinel grains [14,[16][17][18]20]. A strong relationship exists between zoning in Cr-spinel and the degree of chloritization-tremolitization of the Ayios Stefanos chromitites.…”

Section: The Polyphase Cooling History Of the Chromititesmentioning

confidence: 94%

Genesis and Multi-Episodic Alteration of Zircon-Bearing Chromitites from the Ayios Stefanos Mine, Othris Massif, Greece: Assessment of an Unconventional Hypothesis on the Origin of Zircon in Ophiolitic Chromitites

et al. 2016

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Several small chromium (Cr) ore bodies are hosted within a unit of tectonically thinned dunite in the retired Ayios Stefanos mine of the western Othris ophiolite complex in Greece. Chromium ores consist of tectonically imprinted bodies of semi-massive to massive, podiform and lenticular chromitites composed of chromian spinel [Cr-spinel] and mid-ocean ridge basalts (MORBs). Several Cr-spinel crystals in these ores exhibit imperfect zones made up of spinel hosting oriented lamellae of Mg-silicates (mostly chlorite) locally overgrown by porous domains along grain boundaries and fractures. From the Cr-spinel core to the lamellae-rich rim Cr#, Mg# and Fe 3+ # generally increase (0.68-0.87, 0.78-0.88 and 0.55-0.80, respectively), whereas from the core or the spinel zones with oriented lamellae to the porous domains Mg# and Fe 3+ # generally decrease (0.45-0.74 and ≤0.51, correspondingly). The lamellae-rich rims formed at oxidizing conditions, whereas the porous rims resulted from a later reducing event. Several tiny (≤30 µm), subhedral to anhedral and elongated Zr-bearing silicate mineral grains were discovered mainly along open and healed fractures cutting Cr-spinel. Most of the Zr-bearing silicate minerals (30 out of 35 grains) were found in a chromitite boulder vastly intruded by a complex network of gabbroic dykes. The dominant Zr-bearing silicate phase is by far zircon displaying a homogeneous internal texture in cathodoluminescence (CL) images. Raman spectroscopy data indicate that zircons have experienced structural damage due to self-irradiation. Their trace-element contents suggest derivation from a plagioclase-bearing, low-SiO 2 intermediate to mafic source. Combined micro-textural and minerochemical data repeat the possibility of zircon derivation from limited volumes of high-T fluids emanating from the gabbroic intrusions. Once zircon is precipitated in cracks, it may be altered to Ca-rich Zr-bearing silicate phases (i.e., armstrongite, calciocatapleiite). Almost all zircons in these samples show evidence of gains in solvent compounds (CaO, Al 2 O 3 and FeO) possibly due to re-equilibration with late deuteric fluids.

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“…Chromites in massive chromitites commonly retain primary compositions in terms of major elements and can thus be used to deduce the parental melt composition and the probable tectonic setting of the chromitite deposits (e.g., Mondal et al 2006, references therein). However, metamorphosed chromites from massive chromitites within ophiolites may be altered in terms of their minor and trace elements (e.g., González-Jiménez et al 2013Colás et al 2014). The study of chromitite deposits in Archean greenstone belts helps to reveal the nature of the mantle and the tectonic processes prevalent in the Archean.…”

Section: Introductionmentioning

confidence: 98%

“…In situ trace-element analysis using laser ablation ICP-MS (LA-ICPMS) has revolutionized petrogenetic studies as one can investigate the minerals of interest without interference from the surrounding phases (e.g., Dare et al 2009Dare et al , 2011Dare et al , 2012Pagé and Barnes 2009;González-Jiménez et al 2013Pagé et al 2012;Colás et al 2014). Compared to major elements in chromites, the trace elements are more sensitive to parameters like temperature and oxygen fugacity, and they therefore show larger variations during partial melting and fractional crystallization (Dare et al 2009;González-Jiménez et al 2013.…”

Section: Introductionmentioning

confidence: 99%

Trace-element fingerprints of chromite, magnetite and sulfides from the 3.1 Ga ultramafic–mafic rocks of the Nuggihalli greenstone belt, Western Dharwar craton (India)

Mukherjee

Mondal

Gonzáléz-Jiménez

et al. 2015

Contrib Mineral Petrol

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LA-ICPMS) of unaltered chromites indicates that the parental magma of the chromitite ore-bodies was a komatiite lacking nickel-sulfide mineralization. In the Ga/Fe 3+ # versus Ti/Fe 3+ # diagram, the Byrapur chromites plot in the field of suprasubduction zone (SSZ) chromites while those from Bhaktarhalli lie in the MOR field. The above results corroborate our previous results based on majorelement characteristics of the chromites, where the calculated parental melt of the Byrapur chromites was komatiitic to komatiitic basalt, and the Bhaktarhalli chromite was derived from Archean high-Mg basalt. The major-element chromite data hinted at the possibility of a SSZ environment existing in the Archean. Altered and compositionally zoned chromite grains in our study show a decrease in Ga, V, Co, Zn, Mn and enrichments of Ni and Ti in the ferritchromit rims. Trace-element heterogeneity in the altered chromites is attributed to serpentinization. The trace-element patterns of magnetite from the massive magnetite bands in the greenstone belt are similar to those from magmatic Fe-Ti-V-rich magnetite bands in layered intrusions, and magnetites from andesitic melts, suggesting that magnetite crystallized from an evolved gabbroic melt. Enrichments of Ni, Co, Te, As and Bi in disseminated millerite and niccolite occurring within chromitites, and in disseminated bravoite within magnetites, reflect element mobility during serpentinization. Monosulfide solid solution inclusions within pyroxenes (altered to actinolite) in pyroxenite, and interstitial pyrites and chalcopyrites in magnetite, retain primary characteristics except for Fe-enrichment in chalcopyrite, probably due to sub-solidus re-equilibration with magnetite. Disseminated sulfides are depleted in platinum-group elements (PGE) due to late sulfide saturation and the PGE-depleted nature of the mantle source of the sill-like ultramafic-mafic plutonic rocks in the Nuggihalli greenstone belt. AbstractThe 3.1 Ga Nuggihalli greenstone belt in the Western Dharwar craton is comprised of chromitite-bearing sill-like ultramafic-mafic rocks that are surrounded by metavolcanic schists (compositionally komatiitic to komatiitic basalts) and a suite of tonalite-trondhjemite-granodiorite gneissic rocks. The sill-like plutonic unit consists of a succession of serpentinite (after dunite)-peridotite-pyroxenite and gabbro with bands of titaniferous magnetite ore. The chromitite ore-bodies (length ≈30-500 m; width ≈2-15 m) are hosted by the serpentinite-peridotite unit. Unaltered chromites from massive chromitites (>80 % modal chromite) of the Byrapur and Bhaktarhalli chromite mines in the greenstone belt are characterized by high Cr# (100Cr/(Cr + Al)) of 78-86 and moderate Mg# (100 Mg/ (Mg + Fe 2+ )) of 45-55. In situ trace-element analysis Communicated by Timothy L. Grove. Electronic supplementary materialThe online version of this article (

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Fingerprints of metamorphism in chromite: New insights from minor and trace elements

Cited by 102 publications

References 47 publications

Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton

Origin of Reverse Zoned Cr-Spinels from the Paleoproterozoic Yanmenguan Mafic–Ultramafic Complex in the North China Craton

Genesis and Multi-Episodic Alteration of Zircon-Bearing Chromitites from the Ayios Stefanos Mine, Othris Massif, Greece: Assessment of an Unconventional Hypothesis on the Origin of Zircon in Ophiolitic Chromitites

Trace-element fingerprints of chromite, magnetite and sulfides from the 3.1 Ga ultramafic–mafic rocks of the Nuggihalli greenstone belt, Western Dharwar craton (India)

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