太平洋多金属结核中铂族元素特征及其资源启示

Characteristics of platinum group elements in submarine polymetallic nodules and their resource implications

为研究大洋多金属结核中铂族元素(PGEs)的含量及其地球化学特征,对我国大洋第40航次在西北太平洋所获得的23个多金属结核进行PGEs分析测试。结果表明,研究区多金属结核中PGEs总量(∑PGE)为189×10^(-9)~338×10^(-9),平均值为258×10^(-9)。球粒陨石标准化PGEs配分模式呈现明显的Pt正异常及从Os到Pt逐渐富集、从Pt到Pd逐渐亏损的特征。与其他类型岩石矿物对比发现,多金属结核中∑PGE低于铜镍硫化物,而略高于铬铁矿,铜镍硫化物和铬铁矿等岩石矿物均有各自独特的PGEs配分曲线,表明其对PGEs的富集机制与多金属结核有所不同。PGEs元素间特征对比结果显示,多金属结核具有最大的Pt/Pt^(*)值,Pt为明显"优势"元素,同时多金属结核中具最小的Pd/Pd^(*)值,与其他类型岩石矿物相比,其Pd尚不算"劣势"元素。综合已有研究,粗略估算得到太平洋多金属结核中∑PGE达8.9×10^(4)t,Pt达7.4×10^(4)t,同时根据原生矿Pt的边界品位及本研究结果,推断多金属结核中的PGEs尤其是Pt元素将具有十分重要的潜在经济价值。

To study the content and geochemical characteristics of platinum group elements(PGEs)in oceanic polymetallic nodules,we analyse the PGEs concentration of 23 polymetallic nodules obtained during the DY-40 th Cruise in the Northwest Pacific Ocean.The results shows the total PGEs(∑PGE)content of polymetallic nodules in study area is from 189×10^(-9)to 338×10^(-9)with an average of 258×10^(-9),the chondrite-normalized PGEs patterns of samples display positive Pt anomalies,with gradual enrichment from Os to Pt and depletion from Pt to Pd.Compared with other types of rocks and minerals,it is found that the content of∑PGE in polymetallic nodules is lower than that of copper-nickel sulfide,but slightly higher than that of chromite.These rocks and minerals like copper-nickel sulfide and chromite have unique PGE partition curves,indicating that their enrichment mechanism of PGEs are different from polymetallic nodules.The comparative characteristics of PGEs indicate that the Pt/Pt^(*)value of polymetallic nodules is the largest,and the Pt is obviously the"dominant"element.At the same time,polymetallic nodules have the minimum Pd/Pd^(*)value,but its Pd is not an"inferior"element compared with other types of rocks and minerals.Based on the previous studies on the coverage and abundance of submarine polymetallic nodules,the∑PGE and Pt resource of pacific polymetallic nodules are roughly calculated to be 8.9×10^(4)t and 7.4×10^(4)t respectively.Meanwhile,according to the boundary grade of Pt in primary mines and the average content of Pt in nodules in this study,it is shown that the PGEs,especially Pt in polymetallic nodules have very important potential economic value.