太平洋富稀土深海沉积物中稀土元素赋存载体研究  

The host of REE + Y elements in deep-sea sediments from the Pacific Ocean

作　　者：王汾连[1,2,3] 何高文[1] 孙晓明[3] 杨阳[2] 赵太平[2] 

机构地区：[1]国土资源部海底矿产资源重点实验室广州海洋地质调查局,广州510075 [2]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广州510640 [3]中山大学海洋科学学院,广州510006

出　　处：《岩石学报》2016年第7期2057-2068,共12页Acta Petrologica Sinica

基　　金：中国科学院矿物学与成矿学重点实验室研究合作基金(KLMM20150201);中国地质调查局专项项目(DD20160204);国土资源部公益性行业科研专项项目(201511036)联合资助

摘　　要：太平洋深海沉积物中富含稀土(含Y,简称REY),尤其是(含)沸石粘土,其主要由粘土组分、沸石、鱼牙骨、微结核及生物残渣等组成,目前对于该类稀土矿床中REY的赋存载体存在争议。本文在中、西太平洋选取两个富REY的沸石粘土样品利用地球化学和矿物学对稀土赋存状态进行定量研究。矿物微区成分表明,鱼牙骨主要成分为磷灰石,含有最高的REY含量,为2497×10^(- 6)~18623×10^(- 6),微结核和沸石颗粒含有较低的REY含量,分别为246×10^(- 6)~333×10^(- 6)和29.36×10^(- 6)~256×10^(- 6)。通过三种矿物相在沉积物63~250μm粒级组分中各自所占质量比例,计算得出磷灰石对REY的贡献率可达90%以上,说明此粒级中磷灰石为主要REY赋存载体,然而相对全岩总的REY含量,该粒级中磷灰石的贡献仍较小。通过对全岩和粉砂级组分(小于63μm)主微量地球化学分析和XRD矿物相分析表明,2个样品中REY主要存在于粉砂级组分中,其中的磷灰石对全岩REY的贡献最高均可达70%左右。另外通过对粘土组分(<2μm)研究发现2个样品粘土组分的REY含量相似,分别为530×10^(- 6)和631×10^(- 6),粘土组分对全岩沉积物的REY贡献意义不大,对整个沉积物REY而言其贡献率仅为2%~5%左右。因此认为磷灰石为整个沸石粘土中REY主要赋存载体。The deep-sea sediments,especially the zeolite clays,are rich in rare earth elements and yttrium（ REY,REE ＋ Y） in the Pacific Ocean. The main components of the sediments include clay,zeolite,fish debris,micronodules and biological residues.However,the carriers of REY are under debate. We have conducted mineralogical investigations,and in-situ major and trace elemental analyses of constituent minerals of the REY-rich zeolite clay from the western and central areas in the Pacific Ocean in order to clarify the host-phase of REY in the mud. The EPMA and LA-ICP-MS data show that the fish debris are mainly composed of apatite with the highest REY contents of 2497 × 10（- 6） 18623 × 10（- 6）,whereas the micronodules and zeolite have lower REY contents of 246 × 10（- 6）333 × 10（- 6）and 29. 36 × 10（- 6） 256 × 10（- 6）. We calculate that the apatites occupy above 90% of the total REY budget in the 63 250μm fraction. However,the total REY value of apatites in the 63 250μm fraction is still insignificant compared with the bulk sediment. The geochemical analyses of whole-rock and silt fraction（ 〈 63μm） and X-ray diffraction analysis show that REY mainly concentrates in the silt fraction and 70% of the whole REY budget concentartes in apatites in both samples. Furthermore,REY contents of the clay fraction（ 〈2μm） in the two samples are 530 × 10（- 6）and 631 × 10（- 6）respectively and make up 2% 5% of the total REY. Therefore,we conclude that the main REY host phase in the zeolite clay is apatite in the western and central Pacific Ocean.

关 键 词：稀土元素 赋存载体 沸石粘土 太平洋 

分 类 号：P595[天文地球—地球化学]