Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

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PGE Distribution in Chromite Placers from Andaman Ophiolite and its Boninitic Parentage


Affiliations
1 Geological Survey of India, Opn: WB-SK-AN, ER, Geological Survey of India, 5th floor, North Building, Bhubignan Bhawan, DK-6 Block, Salt Lake, Kolkata - 700 091, India
2 Geology Department, Indian School of Mines, Dhanbad, India
     

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Chromite placers occurring in Rutland coast of Andaman and Nicobar Islands, India, show PGE incidence. Serpentinised dunite containing thin stringers/lenses of chromite occurring adjacent to placer was possibly the source rock of the chromite placers. Chemical analysis of these chromite placers show PGE elements incidence in the range: Ru <10-56 ppb, Ir <10-12 ppb, Rh <10-14 ppb, Pd <10-136 ppb, Pt <10-28 ppb. Normalization of these PGE values against CI-chondrite indicates enrichment of Ir and Ru and depletion of Rh and Pt, a typical character of ophiolitic chromite. Except few Pd values, the PGE values depict highly fractionated PGE distribution pattern. High Nig-olivine (Fo92-90)and highly fractionated PGE pattern may suggest derivation of the source rock from boninitic melt. Ru-Ir-Os bearing sulphides or alloys were crystallised at early magmatic stage, Pt, Pd were remobilized during hydrothermal activity and concentrated in serpentine.

Keywords

Chromite Placers, PGE Incidence, S-Undersaturation, Boninite, Rultand, Andamans.
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  • PGE Distribution in Chromite Placers from Andaman Ophiolite and its Boninitic Parentage

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Authors

Tapan Pal
Geological Survey of India, Opn: WB-SK-AN, ER, Geological Survey of India, 5th floor, North Building, Bhubignan Bhawan, DK-6 Block, Salt Lake, Kolkata - 700 091, India
Partha Pratim Chakraborty
Geology Department, Indian School of Mines, Dhanbad, India
R. N. Ghosh
Geological Survey of India, Opn: WB-SK-AN, ER, Geological Survey of India, 5th floor, North Building, Bhubignan Bhawan, DK-6 Block, Salt Lake, Kolkata - 700 091, India

Abstract


Chromite placers occurring in Rutland coast of Andaman and Nicobar Islands, India, show PGE incidence. Serpentinised dunite containing thin stringers/lenses of chromite occurring adjacent to placer was possibly the source rock of the chromite placers. Chemical analysis of these chromite placers show PGE elements incidence in the range: Ru <10-56 ppb, Ir <10-12 ppb, Rh <10-14 ppb, Pd <10-136 ppb, Pt <10-28 ppb. Normalization of these PGE values against CI-chondrite indicates enrichment of Ir and Ru and depletion of Rh and Pt, a typical character of ophiolitic chromite. Except few Pd values, the PGE values depict highly fractionated PGE distribution pattern. High Nig-olivine (Fo92-90)and highly fractionated PGE pattern may suggest derivation of the source rock from boninitic melt. Ru-Ir-Os bearing sulphides or alloys were crystallised at early magmatic stage, Pt, Pd were remobilized during hydrothermal activity and concentrated in serpentine.

Keywords


Chromite Placers, PGE Incidence, S-Undersaturation, Boninite, Rultand, Andamans.