深海沉积物中的稀土矿产资源研究进展

近年发现,太平洋和印度洋的深海盆地中存在大量富含稀土的深海沉积物。主要类型为多金属软泥、沸石黏土和远洋黏土,其中的全稀土含量(∑REY,∑REE+Y)为400×10-6~2000×10-6,最高可达6600×10-6,重稀土含量(HREE)已达到或超过中国南方离子吸附型矿床的重稀土品位两倍以上,是潜在的新型稀土资源,具有重要的经济价值。目前不少学者对富稀土的深海沉积物进行了大量地球化学及部分矿物学的工作,认为多金属软泥中的稀土元素多赋存于与海底热液作用有关的铁锰氧化物和氢氧化物中,而沸石黏土和远洋黏土中稀土元素的富集则与磷酸盐的混入密切相关,其稀土元素主要存在于与磷灰石成分相当的生物鱼骨屑中。深海黏土的北美页岩标准化稀土配分模式与海水相似,表明其中的稀土元素主要来自于海水,REY富集成矿可能主要受控于磷灰石早期成岩阶段,期间稀土元素未发生分异。尽管近些年对深海沉积物中的稀土元素研究取得了不少成果,但是,对于沉积物中的稀土富集机制及影响因素等问题仍然需要更加深入的研究。作为稀土资源大国,为了争取我国在国际海底稀土资源竞争中的话语权,维护中国的稀土利益,中国应加紧开展相关的稀土资源勘查和潜力评价。

The progress in the study of REE-rich deep-sea sediments

The deep-sea sediments rich in rare earth elements discovered in recent years in the Pacific and Indian Ocean basin are a potential rare earth mineral resource. The metalliferous sediments, zeolite clay and pelagic clay are thought to be the main types of REY-rich sediments with high total REY(REE+Y) content (400×10^-6-2000×10^-6, the highest up to 6600×10^-6) and heavy rare earth content (HREE). The HREE values of the sediments are nearly twice as abundant as those in the southern Chinaion-absorption-type deposits. Previous chemical and mineral studies suggest that Fe/Mn oxide and oxyhydroxide precipitated from hydrothermal activities is the main host of the REY in the metalliferous sediments, while phosphate whose chemical composition is equivalent to apatite (such as fish debris) is the main carrier of rare earth elements in the zeolite clay and pelagic clay. The NASC-normalized REE patterns of deep-sea sediments are similar to those of seawater, indicating that the rare earth elements of the sediments were taken up from ambient seawater. REY were mainly enriched at the early diagenetic stage of apatite without differentiation. Many achievements have been made about the rare earth elements in deep-sea sediments in recent years. However, the enrichment mechanisms of rare earth elements in deep-sea sediments and influencing factors still need further study. China has been the dominant producer of REE and hosts the most known global reserves. In order to safeguard China''s right in the competition for REE in the international seabed and safeguard China''s benefit, it is very necessary and critical to search for and evaluate potential marine REE resources.