【摘要】 <正> 遍布于各大洋底的铁锰结核是锰、铜、镍、钴等多种金属的重要资源,其储量规模和经济价值早已为广大海洋科学工作者所熟知,而关于铁锰结核的成因问题,尽管也做了很多工作,但认识却不一致,存在着许多不同的观点。更多还原

【Abstract】 Trace and RE element geochemistry and genesis have been studied with respect to a few f erromanganese nodules from the sediments of the Pacific, Atlantic and Indian ocean.1.Geochemical characteristics of major and trace elementsThe essential composition is Mn and Fe in nodules with 17.88-28.64% of H20. Besides 6-Mn02 and FesOs, there are hydrous Mn and Fe oxides such as Mn(OH)4, Fe(OH)3, MnO2.nH2O and Fe2O3.nH2O in the nodules.Fe and Mn are presented in higher valences such as Fe3+ and Mn4+. The Fe2+ was not found by chemical analysis and EPR in ferromanganese nodules, but Mn2+ was. These nodules contain by weight 1-2 percent of the oxides of nickel (Ni), copper (Cu) and cobalt (Co). The Ba/Sr ratio of the nodules is usually over 2. It is considered that foraminiferas can not be material source of the nodules, because foraminiferas with calcite structure contain usually proper Sr but almost no Ba.2.REE dataThe REE contents in nodules are usually greater then 1000 ppm, with Ce/Y ranging from 3.29 to 3.96. The REE distribution pattern for nodules demonstrates that there is no remarkable anomaly for Ce, with ACe - 0.20- +0.48, and AEu<0, and a distinct negative slope.3.GenesisIn order to study the geneses of the nodules, an experiment on the seawater-basaltic glass interaction at 250C and 500 bars has been conducted. It is considered that basalts widely distributed over the ocean floor are perhaps the main source of Mn, Fe, Co, Ni and Cu in the nodules.4.Conclusion(1)Mn, Fe, Cu, Co, Ni and REE have an important significance in Fe-Mn nodules. Mn and Fe mainly occur in high valant cation, i.e. Mn in Mn4+, a small part of Mn2+ and Mn3+, but no Fe2+ in the nodules.(2)The Mn/Fe ratio in the nodules is of indicative character, as the Mn/Fe ratio increase, the contents of Cu and Ni increase, but and Ti decrease.(3)The higher ratio of Ba/Sr in the nodules suggests that their sources do not derive from the carbonaceous bioclast through solution at high pressure below CaC03 compensation depth.(4)The chondrite-normalized REE distribution pattern of the Fe-Mn nodules appear to be a characteristics of LREE enrichment, ACe values may be positive or nega- tive. Eu values are all negative near zero, which suggests that REE source is in close relationship with oceanic crust or upper mantle, but Ce/Y ratio with 2.29-3.96 in the nodules are approximate to those of the continental crust materials. The facts mentioned above suggest that the EEE in the nodules are perhaps of polygenesis. (5) Fe and Mn in the nodules are derived principally from volcanic materials, including sea-floor basalts, and the suitable pH for the formation of Pe-Mn nodules is about 6.5 to 8.5, Eh is about 0.45 to 0.65 V, based on the geochemical experiments and thermndvnamical calculation.更多还原