Formed Causes of Positive Ce Anomaly in Bauxite Deposits in Southern Songshan-Jishan Region,Henan Province
The characteristics of rare earth elements in bauxite ore-hosted strata in Songshan-Jishan region of Henan Province are the reflection of the enrichment and distribution of REE in paleo-weathered crust,but there are two characteristics that are different from present weathered crust.Firstly,the 8Cc in the bauxite reaches 1.77,and 1.07～1.16 for other rocks.There is no negative anomaly.Secondly,the ∑ REE in the ore-hosted strata is 398.43×10-6～440.32×10-6,there is no obvi-ous enrichment layer.Comparison of the geochemical behavior characteristics of rare earth elements in the weathering process,it is believed that the content of pyrite in the paleo-weathered crust original rocks determines the pH change in the weathered crust,the upper part of the weathered crust formed by aluminosilicate rocks containing high pyrite is in a strong acidic environ-ment,the Ce4+complex compound is easily hydrolyzed to form a hydroxide.The downward migration and deposition of Ce hy-droxide resulted in the loss of Ce in upper part of the weathered crust,so the absence of negative Ce anomaly in the ore-hosted strata reflects that the weathered crust had been denuded partly before mineralization.In bauxite ore-hosted strata,the average value of V/Cr is 1.55 and Co/Ni is 0.31,which shows that the seawater has an oxidizing environment during the deposition process,and REE in the suspended particles in the seawater can be further separated,which also has a certain effect in the formation of the positive Ce anomaly in bauxite ore-hosted strata.REE in the ore-hosted strata didn't change significantly after mineralization.
Songshan-Jishan regionpaleo-weathered crustbauxiterare earth elementspositive Ce anomaly
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