A Preliminary Study Of The Pacific Deep-sea Sediments REE Geochemistry And Resource Potential

In the present study, the chemical compositions of REY (including rare earth elements andyttrium) were studied based on the one-hundred and ninety deep-sea surface sediment samplescollected from the Pacific Ocean. The results showed that the distributions of REY in thesesediment samples presented a significant spatial variation, where the REY were mainly enrichedin samples from Clarion-Clipperton (CC) area in the Eastern Pacific Ocean and in a few samplesfrom Central Pacific and Southeast Pacific Ocean. The low contents of REY in the continentalmargin of the Pacific were widespread observed. The REY were mainly enriched in the types ofzeolite clay and pelagic clay. The contents of REY in zeolite clay were between169.23×10-6and1632.91×10-6,while mean value was701.84×10-6. The contents of REY in pelagic clay werebetween48.58×10-6and1301.31×10-6, while mean value was441.65×10-6. The enrichments ofREY were positively correlated with P2O5, MnO, Ni, Cu, Zn, Ba, while negatively correlated withSiO2, TiO2, V, Cr, Ca and Sr. There were remarkable Ce negative anomalies combined with thelight rare earth element (LREE) depletion in most sediment samples. The patterns of the REY insediments were similar with that in the surface seawater in the North Pacific Ocean but showingsignificant difference with the patterns of the terrigenous materials.There were remarkable nagetive Ce anomalies(δCe＜0.9) in the sediments in which thecontents of REY enriched.The enrichments of REY in the sediments were closely related to δCeand the water depth. The distributions of the sediments with positive Ce anomalies (δCe＞1.1)were mainly in the high-latitude regions with water depth between4767and5750meters, whichmaybe related with the distribution of the terrigenous materials. The sediments with no Ceanomalies (0.9≤δCe≤1.1) were mainly in the mid and high latitudes regions where the waterdepth were between4284and5920meters, whereas those with negative Ce anomalies weremainly in the low-latitude regions, may be likely to the productivity of surface water and the typesof the sediments. The depletion of Ce were closely related to the contents of MnO, P2O5and Co.According to the classification criteria of ionic adsorption deposits of REY resources in theSouth China, The surface sediments in the study area could be divided into four types，namelynon-enriched type, weak enrichment type, enriched type and extremely enriched type. Theenriched and extremely enriched type sediments would be defined as the reserves with resource potential, the REY of which were mainly included in zeolite clay and pelagic clay and a fewsiliceous sediments with the water-depth between4000and5600m. The associated contents of Co,P2O5and MnO in these two types were above33.70×10-6, above0.12%and below20%,respectively.The minority of the surface sediments maybe have REY resource potential according to theclassification criteria. The resources of LREE in sediments around eighteen LREE-enriched wereestimated about3025tons considering the thickness (20cm) and the surrounding radius (1km).Most of the surface sediment samples were enriched with HREY (heavy rare earth elements), withthe potential resource of2207tons for the enriched type and5748tons for the extremely enrichedtypes in the sediments around the sites, respectively. The potential resources of REY aroundthirty-four REY-enriched sediments was about7458tons; while the resources potential around thesix REY-extremely-enriched types of sediments was about2426tons.