Chromites from the early Proterozoic Outokumpu-Jormua Ophiolite Belt: a comparison with chromites from Mesozoic ophiolites

Liipo, Jussi; Vuollo, Jouni; Nykänen, Vesa; Piirainen, T.; Pekkarinen, Lauri; Tuokko, I.

doi:10.1016/0024-4937(95)00002-w

Cited by 47 publications

(26 citation statements)

References 18 publications

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“…In addition, we describe in brief the host peridotite, because only limited number of studies on peridotites have been published for the Precambrian ophiolites (e.g. Quick, 1990;Bonavia et al, 1993;Liipo et al, 1995;Vuollo et al, 1995;Suita and Strieder, 1996;Ahmed et al, 2001;Gahlan, 2003;Kusky, 2004).…”

Section: Introductionmentioning

confidence: 99%

Origin of magnetite veins in serpentinite from the Late Proterozoic Bou-Azzer ophiolite, Anti-Atlas, Morocco: An implication for mobility of iron during serpentinization

Gahlan

Arai

Ahmed

et al. 2006

Journal of African Earth Sciences

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Section: Introductionmentioning

confidence: 99%

Origin of magnetite veins in serpentinite from the Late Proterozoic Bou-Azzer ophiolite, Anti-Atlas, Morocco: An implication for mobility of iron during serpentinization

Gahlan

Arai

Ahmed

et al. 2006

Journal of African Earth Sciences

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“…3, the magnetite in the Cuaba samples is low in Cr and plots in the field of 'mag rims'. The field for ferritchromite and its compositional trend was obtained from data and diagrams given by Barnes and Roeder (2001), Pinsent and Hirst (1977) and Liipo et al (1995b). Fields for greenschist, lower-amphibolite, upper-amphibolite and granulite-grade spinels were obtained from Evans and Frost (1975) and Suita and Strieder (1996), as cited by González-Jiménez et al The composition field for Cr-spinel in amphibolite-facies metamorphic rocks is based on data compiled by Barnes (2000) for Cr-spinel in metamorphosed komatiites (see text for discussion).…”

Section: Clinochlore and Magnetitementioning

confidence: 99%

“…Rim compositions plot close to the low Fe end of the ferritchromite composition field (Figs 3b and 7) which is defined by published data on ferritchromite in ultramafic rocks metamorphosed under amphibolite facies conditions reported from other localities (e.g. Evans and Frost, 1975;Pinsent and Hirst, 1977;Liipo et al, 1995b;Suita and Strieder, 1996;Barnes and Roeder, 2001). Overall, the rims of well zoned grains have lower Al, Mg, and Zn contents and are enriched in Fe, Cr, Ti, Mn, Ni and V compared to the cores (Table 1; Figs 6À8).…”

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confidence: 99%

Zoned Cr-spinel and ferritchromite alteration in forearc mantle serpentinites of the Rio San Juan Complex, Dominican Republic

Saumur

Hattori

2013

Mineral. mag.

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Ferritchromite is rarely reported in forearc mantle peridotites. This contribution describes ferritchromite alteration and zoned Cr-spinel in serpentinites from the Rio San Juan Complex in the Dominican Republic. These rocks originated from the forearc mantle and protruded along lithosphere-scale faults in the mid Eocene. # >0.5) is common in ultramafic rocks in amphibolite-grade terranes; however, the serpentinite samples described herein show little evidence of high-grade metamorphism. The lowtemperature serpentine-group mineral lizardite is dominant and high-temperature antigorite is either very rare or absent; other high-temperature minerals, such as talc, tremolite and cummingtonite, are trace constituents. The observed zoning in the Cr-spinel is thought to represent 'immature' ferritchromite, probably formed in response to a short-lived thermal event. This event appears to have been on too short a timescale to produce either proper ferritchromite or significant quantities of high-temperature minerals. It may be related to the emplacement of the nearby Rio Boba Intrusion, or the upward protrusion of the serpentinites along the lithosphere-scale Septentrional fault zone from the base of the mantle wedge through its hotter interior. We suggest that such alteration is rare in forearc serpentinites because they are not commonly heated during exhumation along the plane of subduction. This work demonstrates that Cr-spinel compositions can be modified by relatively low-grade metamorphism.

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“…The chrome spinel is generally low in TiO 2 (<0.28wt%) in both Sol Hamed and Abu Duhr (SED) ( Table 1). The chrome spinel in the Pan-African podiform chromitites and associated peridotites characteris-tically contains a considerable amount of MnO, up to 1.80 wt% (Table 1) whereas spinel in the Phanerozoic and other Proterozoic chromitite deposits has much lower MnO contents [e.g.<0.14 wt% in the Mesozoic Oman chromitite (Auge, 1987), <0.29 wt% in the Proterozoic Outokumpu-Jormua chromitite, Finland (Liipo et al, 1995), and <0.41 wt% in Precambrian podiform chromitites of Kenticha Hill, southern Ethiopia (Fig. 4b, c).…”

Section: Geochemical Characteristicsmentioning

confidence: 99%

The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt: Petrological and geochemical characteristics and mineralization

Saleh

2006

Chin. J. of Geochem.

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The podiform chromitites occur in a well-preserved mantle sequence consisting of lherzolite-harzburgite with abundant lenses of olivine dunite. The podiform chromitite deposits are common as small and irregularly shaped masses in the Southeastern Desert (SED) of Egypt. The podiform chromitites exhibit a wide range of compositions from high Cr to high Al varieties. The Cr of chrome spinel ranges from 0.67 to 0.88 in olivine-dunite, quite similar to that of the high-Cr chromitite, whereas it is around 0.62 in lherzolite-harzburgite. Primary hydrous mineral inclusions, amphibole and phlogopite, in chrome spinel have been reported for the first time from the Pan-African Proterozoic podiform chromitites. On the other hand, petrographic and geochemical evidence suggests that podiform chromitites in the SED of Egypt were formed as a result of crystallization of mafic melts, probably of boninitic composition, the boninitic parental magmas were probably produced by a second stage of melting above a subduction zone. Three types of chromite ores can be distinguished within the SED of Egypt: (a) sulphide-poor podiform ores; (b) brecciated ores; and (c) sulphide-rich ores. Two textural types of inclusions in chromite are distinguished: (1) primary silicate inclusions generally have high Mg-number (>96), Cr and Ni, and are dominated by pargasitic amphibole, forsterite, diopside, enstatite and Na-phlogopite. A diversity of primary and secondary platinum group minerals (PGM) is described from the chromitites, including alloys, sulphides, sulpharsenides and arsenides of Ru, Os, Ir, Rh, Ni, Cu, Fe and Co; (2) in addition to primary PGM and hydrous silicates, the fluids are of low to moderate salinity, sodium-dominated aqueous solutions with complex gas contents. Variable amounts of water, hydrogen, hydrocarbons, carbon dioxides and nitrogen have been determined in inclusion-rich samples. The chondritenormalized PGE patterns of lherzolite-harzburgite and olivine-dunite have negative Ir and Pt, and positive Pd and Au anomalies. Chromitites are homo-geneous in composition but texturally zoned on a large scale. They carry elevated IPGE, manifested in numerous, primary and secondary PGM phases.

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Chromites from the early Proterozoic Outokumpu-Jormua Ophiolite Belt: a comparison with chromites from Mesozoic ophiolites

Cited by 47 publications

References 18 publications

Origin of magnetite veins in serpentinite from the Late Proterozoic Bou-Azzer ophiolite, Anti-Atlas, Morocco: An implication for mobility of iron during serpentinization

Origin of magnetite veins in serpentinite from the Late Proterozoic Bou-Azzer ophiolite, Anti-Atlas, Morocco: An implication for mobility of iron during serpentinization

Zoned Cr-spinel and ferritchromite alteration in forearc mantle serpentinites of the Rio San Juan Complex, Dominican Republic

The chromite deposits associated with ophiolite complexes, Southeastern Desert, Egypt: Petrological and geochemical characteristics and mineralization

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