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Sources of Rare Earths and Prospects for a Viable REE Deposit in River Sediments of Kerala, Southwest India


Affiliations
1 Vignan’s Foundation for Science, Technology and Research, Deemed to be Vignan’s University, Vadlamudi, Guntur 522 213, India
2 National Centre for Earth Science Studies, Akkulam, Thiruvananthapuram 695 011, India
3 CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, India

Studies on rare earth elements (REEs) of river sediments from Kerala, India indicate that the average total REE (ΣREE) of clay and silt-sized fractions is much higher than in Post-Archaean average Australian Shale (PAAS). Peak high ΣREE for the clay fraction is found in the rivers of central Kerala and, for the silt fraction, it is in south and central Kerala. ΣREE shows a moderate to strong correlation with Mn and P and, no correlation with Al, Fe and Ti in both size fractions. ΣREE also shows no correlation with heavy metals in the clay fraction but a strong correlation in silt fraction. PAAS-normalized REE shows MREE-enrichment in almost all the samples. Further, LREE-enriched and HREE-depleted REE patterns are characteristic of sediments from south and central Kerala, and HREE-enriched or flat REE patterns are characteristic of sediments from north Kerala. Weak positive or weak negative Ce anomalies are characteristic of the sediments. The Eu anomaly is negative in a few silt fractions from south Kerala and positive in all other sediments. Sm/Nd ratios are high in the clay fraction and decrease with increasing ΣREE for the sediments of central Kerala. REE enrichment and REE patterns are related to the felsic component and heavy mineral content in the sediments of south Kerala, adsorbed REE associated with the weathering products of laterites in the sediments of central Kerala, and the dominance of mafic component in the sediments of north Kerala. The river sediments of central Kerala may serve as a viable REE deposit because of their high REE content, inexpensive mining, easy recovery and extraction of REE. Only 21 out of 41 rivers of Kerala were analysed in this study. Detailed exploration in other rivers may expand and confirm the potential REE deposits and their economic viabi­lity. This REE deposit is different from the placer sand deposits on the beaches of south Kerala.

Keywords

Clay and silt fractions, Kerala, laterite, rare earth elements, river sediments
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  • Sources of Rare Earths and Prospects for a Viable REE Deposit in River Sediments of Kerala, Southwest India

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Authors

Shaik Sai Babu
Vignan’s Foundation for Science, Technology and Research, Deemed to be Vignan’s University, Vadlamudi, Guntur 522 213, India
A. Prajith
National Centre for Earth Science Studies, Akkulam, Thiruvananthapuram 695 011, India
V. Purnachandra Rao
Vignan’s Foundation for Science, Technology and Research, Deemed to be Vignan’s University, Vadlamudi, Guntur 522 213, India
M. Ram Mohan
CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, India
R. V. Ramana
Vignan’s Foundation for Science, Technology and Research, Deemed to be Vignan’s University, Vadlamudi, Guntur 522 213, India
N. Satyasree
Vignan’s Foundation for Science, Technology and Research, Deemed to be Vignan’s University, Vadlamudi, Guntur 522 213, India

Abstract


Studies on rare earth elements (REEs) of river sediments from Kerala, India indicate that the average total REE (ΣREE) of clay and silt-sized fractions is much higher than in Post-Archaean average Australian Shale (PAAS). Peak high ΣREE for the clay fraction is found in the rivers of central Kerala and, for the silt fraction, it is in south and central Kerala. ΣREE shows a moderate to strong correlation with Mn and P and, no correlation with Al, Fe and Ti in both size fractions. ΣREE also shows no correlation with heavy metals in the clay fraction but a strong correlation in silt fraction. PAAS-normalized REE shows MREE-enrichment in almost all the samples. Further, LREE-enriched and HREE-depleted REE patterns are characteristic of sediments from south and central Kerala, and HREE-enriched or flat REE patterns are characteristic of sediments from north Kerala. Weak positive or weak negative Ce anomalies are characteristic of the sediments. The Eu anomaly is negative in a few silt fractions from south Kerala and positive in all other sediments. Sm/Nd ratios are high in the clay fraction and decrease with increasing ΣREE for the sediments of central Kerala. REE enrichment and REE patterns are related to the felsic component and heavy mineral content in the sediments of south Kerala, adsorbed REE associated with the weathering products of laterites in the sediments of central Kerala, and the dominance of mafic component in the sediments of north Kerala. The river sediments of central Kerala may serve as a viable REE deposit because of their high REE content, inexpensive mining, easy recovery and extraction of REE. Only 21 out of 41 rivers of Kerala were analysed in this study. Detailed exploration in other rivers may expand and confirm the potential REE deposits and their economic viabi­lity. This REE deposit is different from the placer sand deposits on the beaches of south Kerala.

Keywords


Clay and silt fractions, Kerala, laterite, rare earth elements, river sediments



DOI: https://doi.org/10.18520/cs%2Fv126%2Fi3%2F345-359