| Co-rich crusts contain Mn,Co,Pt,Cu,Ni and HREEs,with high economic significance.In this paper,the microscopic structure, mineralogy,geochemistry, material source.chronology and causes of the cobalt-rich crust(M38D-14)from the mountains of the western Pacific Ocean Magellan seamounts was analysised using the electron microprobe,X-ray single crystal diffraction, transmission electron microscopy,X-ray fluorescence scanner, stable isotope mass spectrometer,From the old to the new shell, plaque structure, columnar structure and irregular wavy layer structure appears sequentially. There are a lot of terrigenous minerals in new shell,judging that the ocean environment is changed during its formation.Antarctic Bottom Water becomes weakened,the amount of sedimentary clastic becomes more and more and the oxidizing environment becomes strong to weak during its formation.Analysising the composition of cobalt-rich crusts (M38D-14)by X-ray diffraction, cobalt-rich mineral composition can be divided into three phases:manganese mineral phase, iron hydroxide amorphous phase and detrital mineral phase.Manganese mineral phase mainly includes todorokite and birnessite; amorphous iron hydroxide phase contain goethite; detrital components consists of calcite, quartz, zeolites, serpentine and montmorillonite.By transmission electron microscopy,we can find that todorokite is fibrous and lamellar and X-ray diffraction image of polycrystalline is ring.EDX analysis showed todorokite mainly contain Mn, Fe, and small amounts of K,Ca,Ti,Co.Otherwise,Al and Si are included, this is because in natural conditions, aluminum silicate minerals and manganese mineral are symbiosis.(102) plane lattice fringes appear like bending phenomenon, which is due to changing the [MnO6] volume by isomorphic substitution among octahedral cations in the crystal. One-dimensional lattice of todorokite shows that (111),(010) crystal plane of the lattice fringes are flat and regular distribution.It is the evenice [Mn06] octahedron structure in unit layer is not distorted and growth in ideal rule.TEM shows that birnessite is curly leaf-shaped. It’s (200) plane occurs edge dislocation, which may be caused by stress.By electron microprobe for cobalt-rich crusts (M38D-14) element geochemical analysis, the results indicate that the crust mainly contain Mn and Fe, K, P and Ti are loss, Ba, Th and Ce are highly enriched. Based on the cobalt-rich crusts of major elements and trace elements were correlation and cluster analysis showed that the cobalt-rich crust of the elements can be divided into three groups, the water group:Mn,Hf,Ba,Mo,S,Ca,Co,Ti,Nb,K,Y,Sr,Zr,V,Fe;terrestrial group: Si, Al;biogenic group:Ni,Cu,P,Zn.Co stratigraphy dating method is applied tostuding cobalt-rich crusts (M38D-14).The results show that the bottom of the cobalt-rich crusts age is 29.29Ma. By comparising Co/(Fe+Mn) and Co/(Ni+Cu) curves with Pacific benthic δ18O, we find that when the cobalt-rich crusts (M38D-14) mineralization,degree of oxidation of seawater significantly increased in 26Ma,14Ma, when 2Ma.Regarding Al/(Fe+Mn) as an indicator to study the cobalt-rich crusts (M38D-14) on the dust record,the result is that monsoon strengthened and the dust transport ing from inland to the Pacific increased in 22Ma,8Ma and 3Ma.Fe-Mn-[(Cu+Ni)×10], Fe-Mn-[(Cu+Co+Ni)×10] and Mn/Fe value are applied to search the causes of cobalt-rich crust (M38D-14).The results indicate that cobalt crust(M38D-14) is hydrogenous. |
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