富钴结壳中矿物组成对稀土元素分布的制约  

Mineralogical control on REEs distributions in Co-rich crusts

作　　者：张平萍[1,2,3] 初凤友[1,2] 李小虎[1,2] 

机构地区：[1]国家海洋局海底科学重点实验室,浙江杭州310012 [2]国家海洋局第二海洋研究所,浙江杭州310012 [3]浙江大学海洋学院,浙江杭州310058

出　　处：《海洋学报》2015年第5期136-147,共12页

基　　金：国家海洋局青年海洋科学基金(2011321);国家海洋局第二海洋研究所专项基金(JG1101);国家自然科学基金(41276055;41178045)

摘　　要：为探讨富钴结壳中矿物组成对稀土元素分布的制约,对约翰斯顿岛富钴结壳中矿物组成及稀土元素特征进行了研究。依据主要矿物组成,富钴结壳可以分为3种类型,分别命名为A、B、C。由A到C,水羟锰矿含量逐渐降低,B类中磷灰石含量最高,C类中水钠锰矿和钙锰矿含量最高。A类结壳中富集REE3+、Ce,B类结壳中富集Ce和Y。A类富钴结壳中,REE3+、Y以专属吸附的方式富集在铁氧化物上,Ce3+氧化成Ce4+与其他REE分离,吸附在锰矿物上。B类结壳中,稀土元素主要以独立矿物的形式存在,另有部分Ce、LREE3+吸附于铁相中,部分Y存在于磷灰石中。C类结壳中,稀土元素主要赋存在锰矿物中,部分Y存在于磷灰石中。Rare earth elements （REEs） are important tracers for geochemical cycles, and are also world strategic re- sources. In this study, we investigated the mineral and REEs characteristics of Co-rich crusts from Johnston island to show that REEs distributions are constrained by their mineral compositions. On the basis of their mineral char- acteristics, the Co-rich crusts can be classified into type A, type B,and type 12. The vernadite contents decrease from type A via type B to type C; and type B shows the highest apatite contents. Birnessite and todorokite are enriched in type C crust. Type A crusts are enriched in REE^3＋ and Ce,whereas type B crusts are characterized by high con- tents of Ce and Y. In type A crust,REE^3＋ and Y that originated from seawater are specified adsorbed on the Fe- phase. Cerium is enriched in Mn-mineral via the oxidation from Ce^3＋ to Ce^4＋ and separation from other REEs. In type B crust,REEs mainly form independent minerals, part of Ce and LREE^3＋ are absorbed in the Fe-phase, and part of Y enter in apatite. In type C crust, REEs show the enrichment phenomena in Mn-minerals, and also part of Y are absorbed in apatite.

关 键 词：富钴结壳 矿物组合 稀土元素 富集机制 

分 类 号：P736.3[天文地球—海洋地质]