Chromian spinels in metamorphosed ultramafic rocks from Mangabal I and II complexes, Goi�s, Brazil

Cândia, Maria Ângela Fornoni; Gaspar, José Carlos

doi:10.1007/bf01163133

Cited by 32 publications

(26 citation statements)

References 15 publications

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“…Moreover the degree of metamorphic reequilibration in metamorphosed chrome-spinels depends on the ratio of P H 2 O and P total . Candia and Gaspar (1997) found that when P H 2 O ¼ P total , complete metamorphic reequilibration occurred, but when P H 2 O < P total , relict igneous cumulate textures were preserved. Proenza et al (2004) suggested that at high pressure conditions there is no resetting of the primary igneous composition of chromites.…”

Section: Discussionmentioning

confidence: 95%

Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

Ghosh

Konar

2011

Journal of Asian Earth Sciences

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Section: Discussionmentioning

confidence: 95%

Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

Ghosh

Konar

2011

Journal of Asian Earth Sciences

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“…In Cr-spinels from ultramafic complexes in Brazil that has been metamorphosed (700 -750 8C and 6 -7 kbars) under variable P H2O conditions, Candia and Gaspar (1997) found that when P H2O ¼ P tot , complete metamorphic reequilibration occurred, but when P H2O , P tot , relict igneous cumulate textures were preserved. Hence, the Fig.…”

Section: Alteration Of Chromite In Chromitites and Serpentinitesmentioning

confidence: 95%

Paleozoic serpentinite-enclosed chromitites from Tehuitzingo (Acatlán Complex, southern Mexico): a petrological and mineralogical study

Proenza

Ortega-Gutiérrez

Camprubí

et al. 2004

Journal of South American Earth Sciences

108

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“…Moreover, the textural immaturity of the ferrian chromite stresses the establishment of low P H 2 O conditions during Cr-spinel alteration (Candia and Gaspar 1997) in the context of a rather brief, retrograde metamorphic event (e.g., Saumur and Hattori 2013). In the course of this metamorphic episode minor Cr-spinel replacement by ferrian chromite took place due to clinochlore substitution for olivine.…”

Section: Origin Of Cr-spinel Alterationmentioning

confidence: 99%

Alteration of mélange-hosted chromitites from Korydallos, Pindos ophiolite complex, Greece: evidence for modification by a residual high-T post-magmatic fluid

Kapsiotis¹

2014

Acta Geologica Polonica

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ABSTRACT:Kapsiotis, A.N. 2014. Alteration of mélange-hosted chromitites from Korydallos, Pindos ophiolite complex, Greece: evidence for modification by a residual high-T post-magmatic fluid. Acta Geologica Polonica, 64 (4), 473-494. Warszawa.The peridotites from the area of Korydallos, in the Pindos ophiolitic massif, crop out as deformed slices of a rather dismembered sub-oceanic, lithospheric mantle section and are tectonically enclosed within the Avdella mélange. The most sizeable block is a chromitite-bearing serpentinite showing a mesh texture. Accessory, subhedral to euhedral Cr-spinels in the serpentinite display Cr# )] values that vary between 0.57 and 0.62, whereas the TiO 2 content may be up to 0.47 wt.%. The serpentinite fragment is characterized by low abundances of magmaphile elements (Al 2 O 3 : 0.66 wt.%, CaO: 0.12 wt.%, Na 2 O: 0.08 wt.%, TiO 2 : 0.007 wt.%, Sc: 4 ppm) and enrichment in compatible elements (Cr: 2780 ppm and Ni: 2110 ppm). Overall data are in accordance with derivation of the serpentinite exotic block from a dunite that was formed in the mantle region underneath a back-arc basin before tectonic incorporation in the Korydallos mélange.Two compositionally different chromitite pods are recognized in the studied serpentinite fragment, a Cr-rich chromitite and a high-Al chromitite, which have been ascribed to crystallization from a single, progressively differentiating MORB/IAT melt. Although both pods are fully serpentinized only the Al-rich one shows signs of limited Cr-spinel replacement by an opaque spinel phase and clinochlore across grain boundaries and fractures. Modification of the ore-making Cr-spinel is uneven among the Al-rich chromitite specimens. Textural features such as olivine replacement by clinochlore and clinochlore disruption by serpentine indicate that Cr-spinel alteration is not apparently related to serpentinization. From the unaltered Cr-spinel cores to their reworked boundaries the Al 2 O 3 and MgO abundances decrease, being mainly compensated by FeO t and Cr 2 O 3 increases. Such compositional variations are suggestive of restricted ferrian chromite (and minor magnetite) substitution for Cr-spinel during a short-lived but relatively intense, low amphibolite facies metamorphic episode (temperature: 400-700 °C). The presence of tremolite and clinochlore in the interstitial groundmass of the high-Al chromitite and their absence from the Cr-rich chromitite matrix imply that after chromitite formation a small volume of a high temperature, post-magmatic fluid reacted with Cr-spinel, triggering its alteration.

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Chromian spinels in metamorphosed ultramafic rocks from Mangabal I and II complexes, Goi�s, Brazil

Cited by 32 publications

References 15 publications

Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

Chromites from meta-anorthosites, Sittampundi layered igneous complex, Tamil Nadu, southern India

Paleozoic serpentinite-enclosed chromitites from Tehuitzingo (Acatlán Complex, southern Mexico): a petrological and mineralogical study

Alteration of mélange-hosted chromitites from Korydallos, Pindos ophiolite complex, Greece: evidence for modification by a residual high-T post-magmatic fluid

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