The black sand placer resources consisting of ilmenite-rutile-zircon-monzite-sillimanite and garnet ± xenotime found on the coastal beaches of India have counterparts on the coastal belts of Australia, Madagascar, East Africa, and many others all forming parts of the erstwhile super-continent Gondwana. An in-depth review of the occurrences of the beach placers in Indian coast indicates that the beach black sand resources originated from the metapelitic rocks (mostly khondalites) and associated granulites of the continental margin belts affected by repeated episodes of migmatisation and emplacement of intrusives while being part of the supercontinent. Weathering of the provenance rocks, their erosion and transportation by rivers brought the heavy minerals to the coast, where they settled during Pleistocene-Holocene times. Sea waves and drift currents sorted and enriched them further, depending on the configuration of the coastline. India’s west coast deposits appear more related to those from Sri Lanka and Madagascar, whereas India’s east coast deposits have more in common with the west Australian beach placer deposits. Monazite content in the Chavara placer deposit of India’s west coast is relatively high (0.4–2.8% of the heavy minerals) and has lighter group rare earth elements (LREE) concentration of around 60 wt. %. Zircons have some elements from the heavy-group rare earth elements (HREE) spectrum. As mineralization events are associated with tectono-thermal events, unravelling the full spectrum of such events in the Peninsular region of India requires more of geochronological investigations, as has been shown in the case of Madagascar. In view of the current demand for critical minerals, research on metallurgical processing of available placer minerals for rare metals and rare earth elements needs upscaling.

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Black Sand Placer Deposits of the Indian Ocean Coasts with Particular Reference to India

  • K. Soman,
  • D. S. Suresh Babu,
  • V. Ravi Kumar,
  • B. M. Faruque

摘要

The black sand placer resources consisting of ilmenite-rutile-zircon-monzite-sillimanite and garnet ± xenotime found on the coastal beaches of India have counterparts on the coastal belts of Australia, Madagascar, East Africa, and many others all forming parts of the erstwhile super-continent Gondwana. An in-depth review of the occurrences of the beach placers in Indian coast indicates that the beach black sand resources originated from the metapelitic rocks (mostly khondalites) and associated granulites of the continental margin belts affected by repeated episodes of migmatisation and emplacement of intrusives while being part of the supercontinent. Weathering of the provenance rocks, their erosion and transportation by rivers brought the heavy minerals to the coast, where they settled during Pleistocene-Holocene times. Sea waves and drift currents sorted and enriched them further, depending on the configuration of the coastline. India’s west coast deposits appear more related to those from Sri Lanka and Madagascar, whereas India’s east coast deposits have more in common with the west Australian beach placer deposits. Monazite content in the Chavara placer deposit of India’s west coast is relatively high (0.4–2.8% of the heavy minerals) and has lighter group rare earth elements (LREE) concentration of around 60 wt. %. Zircons have some elements from the heavy-group rare earth elements (HREE) spectrum. As mineralization events are associated with tectono-thermal events, unravelling the full spectrum of such events in the Peninsular region of India requires more of geochronological investigations, as has been shown in the case of Madagascar. In view of the current demand for critical minerals, research on metallurgical processing of available placer minerals for rare metals and rare earth elements needs upscaling.