| 1 | Rare earth element(REE) geochemistry of phosphorites of the Sonrai area of Paleoproterozoic Bijawar basin,Uttar Pradesh,India显示文摘The rare earth element(REE) data from the Paleoproterozoic Bijawar basin,Sonrai phosphorites were used to interpret the depositional conditions of the phosphorites.The post archean Australian shales(PAAS) normalized REE patterns of the Sonrai phosphorites were characterized by negative Ce and positive Eu anomalies.Middle rare earth elements(MREE)-enrichment was a characteristic feature.Phosphorites showing the diagenetic effects on the REE patterns were limited.The observed Eu anomaly was indicative of an anoxic(or sulphate reducing) diagenetic environment of phosphate formation.Mixing of sea water and upwelling during the Paleoproterozoic was responsible for the recording of positive Eu and negative Ce anomalies in the Sonrai phosphorites. | K.F.Khan Shamim A.Dar Saif A.Khan | 2012 | Journal of Rare Earths2012，30，5： | 3 |
| 2 | Rare earth element signatures of Paleoproterozoic Sallopat phosphorites of Aravalli Basin,India:implications for diagenetic effects and depositional environment显示文摘As a repository of REE,the Paleoproterozoic phosphorite of the Aravalli Basin in India is explored time to time.Paleoproterozoic phosphorite deposits of the Sallopat sub-basin Banswara district of the Aravalli Supergroup show moderate REE concentrations much lower than that of average marine phosphorites.Different ratios and PAAS-normalized REE distribution patterns reflect MREE enrichment over LREE and HREE in these phosphorites.MREE enrichment confirmed by(Sm/Yb)Nversus(Sm/Pr)Nrelationship and attributed to the selective uptake by cyanobacteria and mixing of riverine inputs.Y/Ho,La/Ce and Er/Nd ratios confirm that the REE in Sallopat phosphorites might have been affected by the argillaceous terrigenous and plagioclase-rich sediments probably derived from Banded Gneissic Complex.Diagenetic modeling indicates that REE were concentrated during early diagenetic processes with limited weathering influence.Moderate negative to low Ce anomaly depicts oxic to sub-oxic conditions of seawater due to oxidation of Ce^(3+)to Ce^(4+)whereas Eu^(3+)reduced to Eu^(2+)indicating positive Euanomaly and reducing conditions as well during the deposition.These anomalies may be due to the stratified restricted marine environment of upwelling and mingling of organic-rich anoxic deep water with oxic upper seawater prior to the formation of phosphorite deposits in the embayment.Enrichment of REE in Sallopat phosphorite relies on various physico-chemical conditions.These phosphorites may have been formed in restricted marine water which was influenced by extra clastic sediment input carried out by fluvial systems. | Samsuddin Khan Shamim A.Dar K.F.Khan Mohd Shuaib | 2023 | Acta Geochimica2023，42，4： | 0 |
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