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, Hisham A.; Arai, Shoji; Ahmed, Ahmed H.; Ishida, Yoshito; Abdel-Aziz, Yaser M.; Rahimi, Abdellatif

doi:10.1016/j.jafrearsci.2006.06.003

Cited by 49 publications

(21 citation statements)

References 57 publications

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“…The high Co content reported by Gahlan and Arai (2007) in the core of an altered chromian spinel grain included in a magnetite vein (1.8 wt.% CoO) is not easily explicable with the proposed interpretation. However, the proximity of their study area to numerous cobalt arsenide deposits belonging to the Aït-Ahmane district and the occurrence of these veins, filling open space of cracks in serpentinite (Gahlan et al, 2006) allow interpreting the provenance of Co from remobilization of the nearby Co-Ni arsenide ores. Nonetheless, new studies are needed to better understand the relative chronology of magnetite veins with respect to the mineralizing processes.…”

Section: The Role Of Serpentinization/metamorphismmentioning

confidence: 99%

“…To tackle this issue we investigated the compositional variations of chromian spinel scattered in ophiolite-related serpentinites hosting or spatially associated with Co-Ni arsenide and Cu-rich sulphide ores in the Bou Azzer mining district (Morocco). Previous studies revealed unusually high, but heterogeneous, Mn, Zn and Co contents in chromian spinels hosted in both barren and mineralized serpentinite bodies (Ahmed et al, 2005(Ahmed et al, , 2009Gahlan et al, 2006;Gahlan and Arai, 2007;El Ghorfi et al, 2008). Ahmed et al (2005) reported up to 4.9 wt.% MnO (ZnO and CoO were not analysed), in chromian spinel grains from barren serpentinized harzburgites of the mantle section of the Bou-Azzer ophiolite, but lower contents of Mn in those from wehrlite (up to 1.09 wt.%), chromitite (up to 0.99 wt.%) and dunite (up to 0.93 wt.%).…”

Section: Introductionmentioning

confidence: 99%

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Zn-, Mn- and Co-rich chromian spinels from the Bou-Azzer mining district (Morocco): Constraints on their relationship with the mineralizing process

Fanlo

Gervilla

Colás

et al. 2015

Ore Geology Reviews

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Section: The Role Of Serpentinization/metamorphismmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Zn-, Mn- and Co-rich chromian spinels from the Bou-Azzer mining district (Morocco): Constraints on their relationship with the mineralizing process

Fanlo

Gervilla

Colás

et al. 2015

Ore Geology Reviews

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“…At this stage, the magnetite possibly acts as a reservoir of Zn (cf., Gahlan and Arai, 2007). The magnetite veins in serpentinite, described by Gahlan et al (2006), show large concentrations of such Fe. At some higher temperatures, the magnetite component is added to the pre -existing chromian spinel; this addition is frequently accompanied by the release of an Mg -Al spinel component, which leads to the formation of chlorite, and this whole process results in the formation of ferritchromite (approximately Fe 2+ CrFe 3+ O 4 ) (cf., Wylie et al, 1987;Arai et al, 2006).…”

Section: Discussionmentioning

confidence: 97%

“…Gahlan and Arai (2007) observed the enrichment of Zn together with Fe, Mn, Co, and Ni in primary chromites in strongly serpentinized peridotites from the Proterozoic ophiolite of Bou Azzer, Morocco. This enrichment is particularly prominent in the chromites found in the magnetite veins in serpentinite (Gahlan et al, 2006). Zn -rich chromites are common in regionally metamorphosed ultramafic rocks (e.g., Thayer et al, 1964;Challis et al, 1995).…”

Section: Altered or Metamorphosed Ultramafic Rocksmentioning

confidence: 99%

Zincian chromite inclusions in diamonds: Possibility of deep recycling origin

Arai

Ishimaru

2011

Journal of Mineralogical and Petrological Sciences

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It was reported by Meyer and Boyd (1972) that zincian chromite, having 2 wt% to 3 wt% ZnO and high (>0.9) Cr# (= Cr/(Cr + Al) atomic ratio), appears as inclusions in diamonds obtained from kimberlite. Zincian chromite is characterized by a low (<0.03) Mg# [= Mg/(Mg + ferrous Fe + Zn + Mn + Ni + Co) atomic ratio] and an appreciable amount of MnO (0.4 -0.5 wt%). The chemistry of zincian chromite is very different from commonly found chromite inclusions (magnesiochromite) in diamonds, which contain low amounts of ZnO (<0.1 wt%) and MnO (<0.1 wt%). Zincian and manganoan chromites are also commonly found in meteorites and in altered/ metamorphosed peridotites and related rocks. The chromites found in meteorites mostly have an intermediate Mg# (0.2 -0.5) and a high Cr# (mostly >0.8); moreover, the major -element chemistry of these chromites is similar to that of the magnesiochromite inclusions in diamonds. Spinels obtained from altered rocks show a chemical range that comprises the zincian chromite inclusions found in diamonds. The origin of these inclusions possibly lies in deep recycling. They were initially formed at the Earth's surface in altered/metamorphosed peridotites; they then sank deep down into the mantle and were entrained to the surface again by kimberlite magmatism.

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“…It is well known that the solid intrusive mantle peridotites of Precambrian age have been intensely altered. For example, peridotites of the mantle section of Proterozoic ophiolites have been severely altered; their olivines and pyroxenes have been completely altered to serpentines or carbonates (Quick 1990; Gahlan et al. 2006).…”

Section: Discussionmentioning

confidence: 99%

Petrology of the Yugu peridotites in the Gyeonggi Massif, South Korea: Implications for its origin and hydration process

et al. 2008

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Peridotites exposed in the Yugu area in the Gyeonggi Massif, South Korea, near the boundary with the Okcheon Belt, exhibit mylonitic to strongly porphyroclastic textures, and are mostly spinel lherzolites. Subordinate dunites, harzburgites, and websterites are associated with the lherzolites. Amphiboles, often zoned from hornblende in the core to tremolite in the rim, are found only as neoblasts. Porphyroclasts have recorded equilibrium temperatures of about 1000°C, whereas neoblasts denote lower temperatures, about 800°C. Olivines are Fo 90-91 in lherzolites and Fo 91 in a dunite and a harzburgite. The Cr# (= Cr/(Cr + Al) atomic ratio) of spinels varies together with the Fo of olivines, being from 0.1 to 0.3 in lherzolites and around 0.5 in the dunite and harzburgite. The Na 2 O content of clinopyroxene porphyroclasts is relatively low, around 0.3 to 0.5 wt% in the most fertile lherzolite. The Yugu peridotites are similar in porphyroclast mineral chemistry not to continental spinel peridotites but to sub-arc or abyssal peridotites. Textural and mineralogical characteristics indicate the successive cooling with hydration from the upper mantle to crustal conditions for the Yugu peridotites. Almost all clinopyroxenes and amphiboles show the same U-shaped rare earth element (REE) patterns although the level is up to ten times higher for the latter. The hydration was associated with enrichment in light REE, resulting from either a slab-derived fluid or a fluid circulating in the crust. The mantle-wedge or abyssal peridotites were emplaced into the continental crust as the Yugu peridotite body during collision of continents to form a high-pressure metamorphic belt in the Gyeonggi Massif. The peridotites from the Gyeonggi Massif exhibit lower-pressure equilibration than peridotites, with or without garnets, from the Dabie-Sulu Collision Belt, China, which is possibly a westward extension of the Gyeonggi Massif.

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

Cited by 49 publications

References 57 publications

Zn-, Mn- and Co-rich chromian spinels from the Bou-Azzer mining district (Morocco): Constraints on their relationship with the mineralizing process

Zn-, Mn- and Co-rich chromian spinels from the Bou-Azzer mining district (Morocco): Constraints on their relationship with the mineralizing process

Zincian chromite inclusions in diamonds: Possibility of deep recycling origin

Petrology of the Yugu peridotites in the Gyeonggi Massif, South Korea: Implications for its origin and hydration process

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