Microstructure And Geochemistry Of Co-rich Crust In The Magellan Mountains

In this dissertation,by using mineralogical microscopy,EPMA and LA-ICPMS methods,2 plate-like crusts(MCSD57 and MCSD73)collected both from the Weijia Guyot and 1 cobalt-rich nodule(M3BC1702)collected from the northern sea basin of the Caiwei Guyot have been analyzed for the study of microstructures,normal trace elements,rare earth elements,phosphorylation,material sources and genesis and so on.The main results are as follows:(1)The thickness of the plate-like crust in the Weijia Guyot is large.It has a complete and typical three-layer structure.Among them,the lower dense layer is mainly horizontal laminar structure and columnar structure arranged alternately up and down,the middle loose layer is dendritic structure and patchy structure,and the upper dense layer is palmar structure,fingerprint structure,dendritic structure and patchy structure.(2)There is a certain relation between the enrichment of Co-rich crusts' elements and the constructional layer where they are located.For example,the content of P and Ca in the dense layer at the lower part of the plate crust is high,while Mn,Co,Ni,Mg and Ti are low.The middle loose layer Al,Si and Fe were obviously higher.In addition,elements with strong correlation in the crusts indicate that they have the same provenance or enter the crusts in the same way.(3)REY is enriched in cobalt-rich crusts in the study area,and the Ce content is particularly prominent,accounting for about 60% of ?REY,and Eu is basically no abnormality.The ?REY containing Ce in the dense layer of plate-like crusts is higher than that of other shells,but after removing the Ce content,?REY is actually lower.(4)Phosphorylation has a very obvious effect on the transformation of crusts.The dense layer at the lower part of the plate crust in the study area generally underwent phosphorylation,resulting in P,Ca,Ce and other elements significantly higher than other shells.In addition,phosphorylation impoverishes Mn,Co,Ni and REY except Ce,inhibiting the growth of crusts.(5)Co-rich nodules are a transitional form characterized by both Co-rich crusts and polymetallic nodules.Compared with the plate-like crusts from seamounts,the CO content,Mn / Fe and ? rey of the Co-rich nodules from deep sea basins are similar,and even show more color of water-forming origin.However,it has four layers structure,higher impurity content,many unique hybrid structures,has never suffered from phosphorylation,and has the characteristics of hree enrichment and significant positive y anomaly of each shell,which are obviously different from plate-like crust.In this paper,the plate-like crusts and cobalt nodules studied are all hydrogenic.