Characterisation of chromites, chromite hosted inclusions of silicates and metal alloys in chromitites from the Indo-Myanmar ophiolite belt of Northeastern India

Bidyananda Maibam, Stephen Foley, Ambre Luguet, Dorrit E. Jacob, Toijam Bapin Singh, Dwijesh Ray, Dipak Kumar Panda, Ruth Keppler

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Chromite is commonly used to decipher the petrogenesis and geodynamic setting of ultramafic rocks. Podiform chromitites associated with the mantle sequence of the Indo-Myanmar ophiolite belt are studied here to characterise the major and trace element concentrations of the chromites. The molar ratios Cr# (100×Cr/(Cr+Al)) and Mg# (100×Mg/(Mg+Fe2+)) range from 67 to 82 and 66 to 71, respectively, in the chromites. Calculated equilibrium conditions for chromite crystallisation are 19-25kbar pressure, 1080-1240°C temperature and oxygen fugacity ranging between 0.30 and 0.58 log units above the FMQ buffer, showing that the samples formed in an upper mantle environment. Minor and trace element concentrations in the chromites (Ga 23-33ppm, Ni 1203-1843ppm, V 585-780ppm, Sc 2-5ppm) are comparable to other podiform chromitites hosted in the mantle sections of ophiolite complexes. Using chrome spinel compositions, the parental magma for the chromitite is identified as boninite. Tectonic discrimination diagrams using the primary composition of chromites indicate a supra-subduction zone setting for the Manipur ophiolite chromitites. The chromites host inclusions of silicates, base metal sulphides and base metal alloys. The diversity of these inclusions reflects the important role played by hydrothermal fluids. Inclusions (base metal sulphide and alloys) of linear trails with enriched Cr2O3 (63wt.%, Cr# ∼80) in the chromite grains (Cr2O3, Cr# 70) indicate mobility of this component in chromites.

LanguageEnglish
Pages260-273
Number of pages14
JournalOre Geology Reviews
Volume90
DOIs
Publication statusPublished - Nov 2017

Fingerprint

Silicates
Chromite
chromite
ophiolite
silicate
Metals
metal
base metal
Trace Elements
Sulfides
sulfide
trace element
chrome spinel
boninite
Geodynamics
mantle
chromitite
Tectonics
ultramafic rock
fugacity

Keywords

  • Chromite
  • Ophiolite
  • Trace element
  • Hydrothermal fluid
  • Supra subduction zone
  • parental melt

Cite this

Maibam, Bidyananda ; Foley, Stephen ; Luguet, Ambre ; Jacob, Dorrit E. ; Singh, Toijam Bapin ; Ray, Dwijesh ; Panda, Dipak Kumar ; Keppler, Ruth. / Characterisation of chromites, chromite hosted inclusions of silicates and metal alloys in chromitites from the Indo-Myanmar ophiolite belt of Northeastern India. In: Ore Geology Reviews. 2017 ; Vol. 90. pp. 260-273.
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abstract = "Chromite is commonly used to decipher the petrogenesis and geodynamic setting of ultramafic rocks. Podiform chromitites associated with the mantle sequence of the Indo-Myanmar ophiolite belt are studied here to characterise the major and trace element concentrations of the chromites. The molar ratios Cr# (100×Cr/(Cr+Al)) and Mg# (100×Mg/(Mg+Fe2+)) range from 67 to 82 and 66 to 71, respectively, in the chromites. Calculated equilibrium conditions for chromite crystallisation are 19-25kbar pressure, 1080-1240°C temperature and oxygen fugacity ranging between 0.30 and 0.58 log units above the FMQ buffer, showing that the samples formed in an upper mantle environment. Minor and trace element concentrations in the chromites (Ga 23-33ppm, Ni 1203-1843ppm, V 585-780ppm, Sc 2-5ppm) are comparable to other podiform chromitites hosted in the mantle sections of ophiolite complexes. Using chrome spinel compositions, the parental magma for the chromitite is identified as boninite. Tectonic discrimination diagrams using the primary composition of chromites indicate a supra-subduction zone setting for the Manipur ophiolite chromitites. The chromites host inclusions of silicates, base metal sulphides and base metal alloys. The diversity of these inclusions reflects the important role played by hydrothermal fluids. Inclusions (base metal sulphide and alloys) of linear trails with enriched Cr2O3 (63wt.{\%}, Cr# ∼80) in the chromite grains (Cr2O3, Cr# 70) indicate mobility of this component in chromites.",
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author = "Bidyananda Maibam and Stephen Foley and Ambre Luguet and Jacob, {Dorrit E.} and Singh, {Toijam Bapin} and Dwijesh Ray and Panda, {Dipak Kumar} and Ruth Keppler",
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Characterisation of chromites, chromite hosted inclusions of silicates and metal alloys in chromitites from the Indo-Myanmar ophiolite belt of Northeastern India. / Maibam, Bidyananda; Foley, Stephen; Luguet, Ambre; Jacob, Dorrit E.; Singh, Toijam Bapin; Ray, Dwijesh; Panda, Dipak Kumar; Keppler, Ruth.

In: Ore Geology Reviews, Vol. 90, 11.2017, p. 260-273.

Research output: Contribution to journalArticleResearchpeer-review

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AU - Maibam, Bidyananda

AU - Foley, Stephen

AU - Luguet, Ambre

AU - Jacob, Dorrit E.

AU - Singh, Toijam Bapin

AU - Ray, Dwijesh

AU - Panda, Dipak Kumar

AU - Keppler, Ruth

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