Spinel phases associated with metamorphosed volcanic-type iron-nickel sulfide ores from Western Australia

Groves, David; Barrett, F. M.; Binns, R. A.; McQueen, Ken

doi:10.2113/gsecongeo.72.7.1224

Cited by 61 publications

(27 citation statements)

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“…Aphyric and spinifex-textured komatiites from throughout the komatiite sequence at Kambalda, Western Australia are significantly depleted in Ni and Co relative to unmineralized komatiite sequences and to compositions predicted by theoretical sulfide-free fractional crystallization models (Lesher et al 1981); 2. Chromites in mineralized komatiite sequences in Western Australia are systematically enriched in Zn compared to those from unmineralized sequences (Groves et al 1977.…”

Section: Geochemical Constraintsmentioning

confidence: 97%

Controls on the Formation of Komatiite-Associated Nickel-Copper Sulfide Deposits

Lesher

Groves

1986

Special Publication No. 4 of the Society for Geology Applied to Mineral Deposits

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Nickel-copper sulfide deposits associated with rocks of komatiitic affinity may be divided into two associations on the basis of host rock composition and ore distribution: (1) stratiform, massive-matrix-disseminated sulfides hosted by cumulate komatiite lava flows (lava conduits), or strata-bound, coarse disseminated sulfides hosted by cumulate komatiite bodies near volcanic vents, and (2) strata-bound, finely disseminated sulfides and more restricted massive sulfides hosted by subvolcanic komatiitic dunites (high-level magma chambers). These deposits represent a continuum in environments of emplacement from distal volcanic through proximal and central volcanic to subvolcanic.Field relationships and geochemical data suggest that the sulfides in these deposits are magmatic in origin. Previous models for their formation involve derivation of sulfides directly from the mantle or from low-level magma chambers, but there are several field, physical, and thermodynamic constraints which suggest that this may not be feasible: (1) the spatial concentration of mineralization within certain parts of otherwise virtually barren host units suggests that the latter were not uniformly saturated in sulfide at the time of emplacement; (2) there are physical problems in transporting dense sulfides in low viscosity komatiite magmas, although dispersed sulfide droplets may be supported during rapid ascent; and (3) high temperature komatiitic melts generated by high-degree partial melting, or sequential melting, of mantle source rocks are unlikely to be sulfide-saturated in the source region or to remain sulfide-saturated during adiabatic ascent. These deposits are, however, commonly associated with specific country rocks, particularly sulfidic sediments, and the distribution of the ores appears to be related to the distribution of these rocks. It is most likely that the sulfide ores exsolved from the komatiitic magmas in situ, in response to assimilation of the country rocks during emplacement. The distribution and texture of the mineralization was probably influenced by (1) the mode of emplacement (volcanic vs subvolcanic) and amount of assimilation; (2) the relative volume of magma (lava conduit vs magma chamber) and its capacity to dissolve sulfur; and (3) the timing of sulfide separation and opportunity for segregation. A fundamental aspect of this model is the coincidence of cumulate komatiitic host units (representing dynamic lava conduits and magma chambers) and siliceous, sulfidic, or ferric iron oxide-rich sediments, the former representing a source of heat for assimilation and of ore metals, and the latter a source of sulfur or of components to induce sulfide separation. Mineralized greenstones appear to have formed in deeper water under conditions of greater extension than unmineralized greenstones; rifting environments represent the most favorable tectonic environment for voluminous komatiite eruption/irruption and for accumulation of sulfidic sediments. Variations in the degree of extension along or within the r...

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Section: Geochemical Constraintsmentioning

confidence: 97%

Controls on the Formation of Komatiite-Associated Nickel-Copper Sulfide Deposits

Lesher

Groves

1986

Special Publication No. 4 of the Society for Geology Applied to Mineral Deposits

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“…Note that Bou Azzer serpentine is markedly lower, by several times, in Mn, Co, Ni and Zn than olivine. Each number indicates the sample number listed in Table 3. 8 % of the annual world production from the Co metal; Leblanc and Billaud, 1982 and references therein) in spatial association with the serpentinites support the conclusion: Zn and Mn rich spinels are indicators of Co Ni Zn Cu sulfide mineralization or mineralizing environments associated with serpentinites and serpentinized ultramafics (e.g., Groves et al, 1977;Wylie et al, 1987).…”

Section: The Enrichment Mechanism Of Mn ± Zn ± Co In Chromian Spinelmentioning

confidence: 81%

“…The magmatic origin of Mn, Zn and Co enrichment in the Bou Azzer chromian spinel seems improbable, although the magmatic (primary) enrichment had been postulated for some spinels, such as La Perouse layered gabbro Mn rich spinel (Czamanske et al, 1976) and West Australian Zn rich ferritchromite (Groves et al, 1977(Groves et al, , 1983. Serpentinization can redistribute Fe of the primary silicates (Ramdohr, 1967;MacFarlane and Mossman, 1981), Ni (Bliss and MacLean, 1975) and Lehmann (1983) extended this idea to Mn.…”

Section: Origin and Source Of Mn ± Zn ± Co Enrichment In Chromian Spinelmentioning

confidence: 99%

“…CoO and, ZnO and MnO contents in excess of 0.1 (mostly < 0.05) and 0.5 wt%, respectively, are rather unusual for chromian spinels in ultramafic rocks (e.g., Paraskevopoulos and Economou, 1981;Groves et al, 1983;Barnes, 2000;Ahmed et al, 2001). A variety of origins have been proposed for the Co ± Zn ± Mn enrichment in chromian spinels; secondary (e.g., Bevan and Mallinson, 1980;Economou, 1980, 1981;Wylie et al, 1987;Michailidis, 1990;Abzalov, 1998;Barnes, 2000;Shcheka et al, 2001;Economou, 2003) and/or primary (e.g., Czamanske et al, 1976;Groves et al, 1977Groves et al, , 1983Malakhov, 1983). Comprehensive models for Co , Zn and Mn rich chromian spinel have not been constructed yet.…”

Section: Introductionmentioning

confidence: 99%

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Genesis of peculiarly zoned Co, Zn and Mn-rich chromian spinel in serpentinite of Bou-Azzer ophiolite, Anti-Atlas, Morocco

Gahlan

Arai

2007

Journal of Mineralogical and Petrological Sciences

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The peculiar Co, Zn and Mn rich chromian spinels are hosted by magnetite veins, serpentinites and chromitites of the mantle section of the Proterozoic Bou Azzer ophiolite, Morocco. The spinel is complexly zoned either optically or chemically, and exhibits anomalously high MnO, ZnO and CoO contents (up to 22, 7.5 and 2 wt%, respectively). It has four distinct optical zones particularly in the magnetite veins and less typically in serpentinites. The highest level of these elements, probably divalent, is recorded within the ferritchromite zone and/or within the core zone if the ferritchromite zone is absent. These elements as well as Fe exhibit enrichment along grain boundaries and fractures of the altered spinels. Fe, Mn, Zn and Co were most probably supplied from olivine upon severe serpentinization during and after obduction of the ophiolite.The enrichment of the Bou Azzer chromian spinel in Mn, Zn and Co was governed mainly by the fluid/ mineral (spinel) ratio and partition coefficient between spinel and the relevant fluid among many factors. The Co , Zn and Mn rich chromian spinels can be used as an exploration guide for Co Ni Zn Cu sulfide mineralization associated with serpentinized peridotites.

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“…Ferrochromites from Western Australia (Groves et al, 1977(Groves et al, , 1983 inherited their high Zn content from the magmatic stage. In Outokumpu, Finland (Weiser, 1967), Helgeland area, Norway (Moore, 1977), the Mashaba chromite mine, Zimbabwe (Bevan and Mallinson, 1980) and the Sykesville district, USA (Wylie etal., 1987) metasomatism has taken place and was responsible for the high Zn content of the chromites.…”

Section: Introductionmentioning

confidence: 99%

Compositional zoning in Zn-chromites from the Cordillera Frontal Range, Argentina

1993

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Serpentinised ultramafic bodies containing zoned chromite grains occur in the Cordillera Frontal Range, western Argentina. Chromites show Zn-rich Al-chromite cores (4.04 wt.% ZnO) surrounded by ferritchromite rims (1.3 wt.% ZnO) and outer Cr-magnetite rims. In intensely altered chromites which are spatially related to sulphide mineralisation, the primary chromite cores have been replaced by Zn-rich ferritchromit (7 wt.% ZnO) and they are rimmed by Cr-magnetite. In the Al-chromites the is always surrounded by a Cr-magnetite rim and it was formed as a reaction product owing to the irreversible dissolution of primary chromite cores. The dissolution of these cores provided the essential components for ferritchromit growth. Zn was introduced into the chromite cores and ferritchromit rims during the formation of the latter.Step-scan profiles have shown that the Zn content in the cores increases from the centre to their outer border, where they show the highest Zn values. It is suggested that Zn was introduced by the fluid phase involved in the alteration process that affected the cores and lead to the formation of the zoned chromite grains. This alteration process was also responsible for the changes in [Cr/(Cr + AI)] and [Mg/(Mg + Fe)] ratios.

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Spinel phases associated with metamorphosed volcanic-type iron-nickel sulfide ores from Western Australia

Cited by 61 publications

References 0 publications

Controls on the Formation of Komatiite-Associated Nickel-Copper Sulfide Deposits

Controls on the Formation of Komatiite-Associated Nickel-Copper Sulfide Deposits

Genesis of peculiarly zoned Co, Zn and Mn-rich chromian spinel in serpentinite of Bou-Azzer ophiolite, Anti-Atlas, Morocco

Compositional zoning in Zn-chromites from the Cordillera Frontal Range, Argentina

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