富钴结壳中贵金属元素的特征

Characteristics of Noble Metal Elements in Cobalt-rich Crusts

对太平洋CL、CM海山调查时获取9个富钴结壳样品,采用化学处理及ICP-MS法进行分析。对贵金属元素含量分布特征、富集因子、标准化模式以及来源进行探讨和研究。结果表明:海山结壳中贵金属元素Ag、Au、Ru、Rh、Pd、Pt等的平均含量分别为:1.05×10-6、2.3×10-6、15.6×10-9、22.3×10-9、2.39×10-9和432×10-9。与结核、洋壳及陆地矿石的Pd/(Pt+Pd)、Pt/(Pt+Pd)和Pd/Pt等贵金属元素的比值相比,大洋富钴结壳的Pd/(Pt+Pd)比值最低,为0.006;其次是结核,为0.06;洋壳为0.08;陆地矿石的Pd/(Pt+Pd)比值较大,为0.35～0.65。结壳的Pt/(Pt+Pd)比值最高,为0.99;其次是结核,为0.95;洋壳为0.93;陆地矿石的Pt/(Pt+Pd)比值相对较低,为0.33～0.65。统计分析显示了不同区域、不同环境中贵金属元素的特征参数变化,并且说明富钴结壳中富铂、金、钌、铑,而贫钯。贵金属元素标准化显示,海山富钴结壳均存在着Pt、Au正异常和Pd的负异常,其中Au异常幅度与结核的Au异常一致。

Nine cobalt-rich crusts sampled from CL and CM seamounts have been analyzed for noble metals such as Ag, Au, Ru, Rh, Pd, Pt, and so on by using ICP-MS after chemical process. This paper also discussed the noble metals composition distribution, their enrichment indices, normalization modes, and their sources. The results indicate that the average contents of Ag, Au, Ru, Rh, Pd and Pt in cobalt-rich crusts are 1.05 × 10^ -6, 2. 3 × 10^-6, 15.6 × 10^-9, 22. 3 × 10^ -9, 2. 39 × 10^-9 and 432 × 10^-9, respectively. Enrichment indices such as Pd/（ Pt ＋ Pd）, Pt/（ Pt ＋ Pd） and Pd/Pt ratios in cobalt-rich crusts show distinctive features compared with that of ferromanganese nodules, ocean crusts and terrestrial ores. The average Pd/（ Pt ＋ Pd） ratio in cobalt-rich crusts is 0. 006 which is the lowest value, followed by 0. 06 in nodules, and 0. 08 in ocean crust. But the Pd/（ Pt ＋ Pd） ratio in terrestrial ores is relatively high, and varies between 0.35 and 0. 65. The Pt/（ Pt ＋ Pd） ratio in cobalt-rich crusts is the highest value, up to 0.99, followed by 0. 95 of nodules, and 0. 93 of ocean crust. However, the Pt/（ Pt ＋ Pd） ratio in terrestrial ores is relatively low, and varies between 0.33 and 0. 65. It shows the variations of characteristic values of noble metal elements in different areas and environments from the statistical analysis. Moreover, the enrichment of Pt, Au, Ru, Rh, and lack of Pd in cobalt-rich crusts is the typical features of noble metals in cobalt-rich crusts. The chondrite-normalized patterns of noble metal elements reveal that there exist positive Pt and Au anomalies, and negative Pd anomaly in cobalt-rich crusts of seamounts, among which anomaly extent of Au is in accordant with that of nodules.