Characteristics Of Rare Earth Elements And Yttrium(REY) And Tellurium Enrichment In REY-Rich Deep Sea Sediments From The Central Indian Ocean Basin(CIBO)

REY-rich deep-sea sediments widely found in the Pacific and Indian oceans are rich in rare earth elements,especially middle and heavy rare earth elements,which is a potential mineral resource.Recent studies have found that REY-rich sediments from the central Indian Ocean basin（CIOB）are also enriched in tellurium（Te）,which may be a potentially important Te reservoir.However,due to the extremely small particle size of deep-sea sediments,the host minerals,material sources and genetic mechanism of rare earth elements and Tellurium in REY-rich deep-sea sediments are still unclear,which limits the comprehensive utilization of REY-rich deep-sea sediment resources.Considering this,in this study,three sediment cores（GC04,and GC11 from CIOB;GC03 from Eastern Indian Ocean basin）were sampled for mineral identification,elements（major,trace,and rare earth elements）measurements in the bulk sediment and Te and REY content in individual minerals.Based on the mineralogical characteristics,geochemical characteristics of major and trace elements,elements content in individual minerals,principal component analysis and cluster analysis of sediments,the host minerals of REY and Te,the allocation of REY and Te in different minerals and material sources were studied.The results are as follows:（1）REY are enriched in the sediments from CIOB,and the content of REY range from 336.87×10^-6 to 724.69×10^-6,with an average of 574.78×10^-6,which is similar to that of sediments from GC02,Wharton basin and Pacific Ocean.The core sediments of GC04 and GC11 are enriched in REY,and the distribution pattern of REY and the upper mineral composition are typical REY-rich sediments.The enrichment of Te in REY-rich deep-sea sediments from CIOB was found for the first time,with an average content of 0.61×10^-6,range from 0.27×10^-6 to 0.84×10^-6,the average enrichment coefficient is 610 compared with that of the upper crust.While GC03 core with no enrichment of rare earth element(ΣREY range from150.02×10^-6 to 197.55×10^-6,the average value is 150.02×10^-6),Te content is below detection limit.The results show that the enrichment of Te in sediments is closely related the content of REY in sediment.（2）The ranking of the minerals based on the average REY content is apatite(7111.86×10^-6)>titanite(4016.11×10^-6)>zircon(2613.65×10^-6)>osumilite-（Fe）(1150.75×10^-6)>osumilite-（Mg）(1048.17×10^-6)>rutile(742.57×10^-6).The quantitative calculation based on the proportion of minerals in sediments and the REY content of individual minerals show that apatite,osumilite aggregates,clinoptilolite-K and unclassified material contribute most of REY in the core sediments.REY in the sediments is enriched in terrigenous clastic minerals such as titanite,zircon and rutile,as well as marine authigenic substances such as apatite and weathered volcanic rocks imported from terrigenous metapelitic rock such as osumilite-（Fe）and osumilite-（Mg）.It shows that the REY in sediments had diverse sources.（3）The ranking of the minerals based on the average Te content is clinoptilolite-K(2.41×10^-6)>osumilite-（Fe）(1.65×10^-6)>orthoclase(1.13×10^-6)>dolomite(1.04×10^-6)>calcite(1.01×10^-6)>osumilite-（Mg）(1.00×10^-6).Te in the sediments is enriched in clinoptilolite-K produced by hydrolysis of volcanic glass,weathered volcanic rocks imported from terrigenous metapelitic rock such as osumilite-（Fe）and osumilite-（Mg）,marine authigenic materials such as dolomite and calcite.The quantitative calculation based on the proportion of minerals in sediments and the Te content of individual minerals show that osumilite aggregates,clinoptilolite-K and unclassified materials contribute most of Te in the core sediments,suggesting Te may be mainly derived from the weathered materials of terrestrial metapelitic rock and the hydrolysates of submarine volcanic glass.（4）Although Te and REY are enriched in different minerals,and the allocation of Te and REY of different minerals are different,Te and REY in sediments are closely and positively correlated,and Te is enriched in REY-rich sediments,indicating that they may have a certain symbiotic relationship.Meanwhile,there is a good correlation between Te and ore-forming elements such as Fe,Co,Ni,Mn and Pb.The enrichment of Te in osumilite aggregates formed by ultrahigh temperature metamorphism and clinoptilolite-K formed by Hydrolysates of submarine volcanic glass indicates that Te has a deep source.