富钴结壳（M38D-14）的矿物学、地球化学及其对古海洋环境的响应

发布时间：2018-06-18 12:01

本文选题：富钴结壳 + 矿物　；参考：《中国地质大学(北京)》2014年硕士论文

【摘要】：富钴结壳富含锰、钴、铂、铜、镍、稀土元素,对富钴结壳进行研究,具有极高的经济意义。把源于西太平洋海山区麦哲伦海山的一块富钴结壳样品(M38D-14)作为本文研究对象,运用了电子探针、X射线单晶衍射技术、透射电子显微镜、X射线荧光扫描仪、稳定同位素质谱仪等测试手段,对其进行了微观构造、矿物学、地球化学、物质来源、年代学以及成因的研究。富钴结壳M38D-14壳层至新,依次发育斑块状构造、柱状构造和不规则波状纹层构造,其中新壳层有大量的陆源碎屑矿物,判断在其生长过程中,经历了底流活动强度逐渐减弱,沉积碎屑由少变多,氧化环境由强变弱的环境。通过富钻结壳(M38D-14)矿物成分的x射线单晶衍射分析,将其矿物组成可分为三个相：锰矿物相主要是钡镁锰矿和水钠锰矿；无定型铁的氢氧化物相有针铁矿；碎屑组分相有方解石、石英、沸石、利蛇纹石、蒙脱石。根据透射电子显微镜分析,富钴结壳(M38D-14)可见纳米级的纤维状、片状的钡镁锰矿和卷曲叶片状的水钠锰矿。其中,钡镁锰矿的X射线衍射图像为多晶环,化学成分以含Mn、Fe为主,少量的K、Ca、Ti、Co、Si、Al,这是在自然条件下铝硅酸盐矿物经常与锰矿物共生的结果；其一维晶格像中可见(111)、(010)晶格条纹平直且规则分布,说明其结构单元层中的[MnO6]八面体没有发生畸变且理想规则生长,但其(102)晶格条纹弯曲,说明阳离子类质同像替代引起的[Mn06]八面体体积的变化而形成弯曲的单元层。另外,其水钠锰矿可见(200)晶面出现刃型位错,这可能是应力作用引起的。利用电子探针对富钴结壳(M38D-14)的元素地球化学分析,结果表明：样品以Mn、Fe为主,其波状纹层构造的壳层含Si、Al为主,但Mn、Fe含量极低；其微量元素具有K、 P、Ti亏损,Ba、Th、Ce高度富集的特征。通过对其主、微量元素的相关性和聚类分析,其所含元素分为三组,水成组有Mn、Hf、Ba、Mo、S、Ca、Co、Ti、Nb、K、Y、Sr、 Zr、V、Fe,陆源组有Si、Al,生源组有Ni、Cu、P、Zn。根据Co地层学法、Co/(Fe+Mn)和Co/(Ni+Cu)变化曲线与太平洋底栖有孔虫δ18O曲线对比法分析,可知富钴结壳(M38D-14)形成始于晚渐新世(29.29Ma),经历了3个地质事件,即德雷克水道张开(26Ma)、南极大陆东南极冰盖发育(14Ma)和北半球冰盖形成(2Ma)；其成矿时海水的氧化程度显著增大。将富钴结壳(M38D-14)的Al/(Fe+Mn)值作为风尘记录的指标,发现在22Ma±、8Ma、3Ma时,样品生长经历了东北信风增强、亚洲季风增强和东亚冬夏季风加强3个气候事件,季风加强且内陆输送到太平洋的粉尘增多,这与样品中由老到新的沉积碎屑由少变多是一致的。根据Fe-Mn-[(Cu+Ni)×10]、Fe-Mn-[(Cu+Co+Ni)×10]图解和Mn/Fe值,判断富钴结壳(M38D-14)为水成成因。
[Abstract]:Cobalt-rich crusts are rich in manganese, cobalt, platinum, copper, nickel and rare earth elements. A sample of cobalt-rich crusts (M38D-14) from the Magellan seamounts in the western Pacific seamounts was used in this paper. The electron probe X-ray single crystal diffraction technique and the transmission electron microscope (TEM) X-ray fluorescence scanner were used. The microstructures, mineralogy, geochemistry, material source, chronology and genesis were studied by means of stable isotope mass spectrometer. The crust of cobalt-rich crusts M38D-14 developed in turn into plaques, columnar structures and irregular wavy laminae. Among them, the new crust contains a large number of continental clastic minerals. It is judged that the activity intensity of the underflow gradually weakened during the growth process of M38D-14 crust. Detritus from less to more, oxidation environment from strong to weak environment. By means of X-ray single crystal diffraction analysis of the mineral composition of M38D-14), the mineral composition can be divided into three phases: barium magnesium manganese and sodium manganite; amorphous hydroxides with goethite; clastic components with calcite. Quartz, zeolite, serpentine, montmorillonite. According to the analysis of transmission electron microscope, the cobalt-rich crusts (M38D-14) can be seen in nanoscale fibrous, flake barium manganese and curly vane manganite. Among them, the X-ray diffraction pattern of barium magnesium manganese ore is polycrystalline ring. The chemical composition of barium magnesium manganese ore is mainly Mn-containing Fe and a small amount of K _ (+) CaTiTiCoSi-Si-Al, which is the result of aluminosilicate minerals often symbiosis with manganese ore under natural conditions. In the one-dimensional lattice image, the lattice stripes are flat and regular, indicating that the [MnO6] octahedron in the structural unit layer has no distortion and ideal regular growth, but its lattice stripe is curved. It is shown that the change of volume of [Mn06] octahedron caused by the substitution of cationic isomorphism forms a curved unit layer. In addition, the borderlike dislocation on the crystal surface of sodium manganese ore is probably caused by stress action. The elemental geochemical analysis of cobalt-rich crusts M38D-14) by electron probe shows that the samples are mainly Mn-Fe, and the corrugated crust consists mainly of Si-Al, but the content of Mn-Fe is very low, and the trace elements of M38D-14) have the characteristics of high enrichment of K, PNT-depleted Ba-Ba-ThCe. Through the correlation and cluster analysis of main and trace elements, the elements are divided into three groups. In the hydrogenic group, there are MnHfHfPZN, NbPZN, NiCuPZnZn, NiCuPZnZn, Si-Aland NiCuPZnZN in the Luyuan formation and NiCuPZn1, respectively. Based on the comparative analysis of Co / P Fe mn) and Co / Ni Cu curves with 未 18O curves of benthic foraminifera in the Pacific Ocean, it can be concluded that the formation of cobalt-rich crusts M38D-14) began in the late Oligocene and experienced three geological events. In other words, the Drake waterway is open to 26 Ma, the Antarctic East Antarctic ice sheet is 14 Maa) and the Northern Hemisphere ice sheet is formed, and the oxidation degree of sea water increases significantly during mineralization. Taking the Al / P Fe mn) value of cobalt-rich crusts M38D-14 as the index of wind and dust record, it is found that the growth of samples experienced three climatic events: northeast trade wind enhancement, Asian monsoon enhancement and East Asian winter and summer monsoon enhancement at 22 卤8 Ma ~ 3 Ma. The monsoon intensifies and more dust is transported inland to the Pacific Ocean, which is consistent with the change from old to new detritus in the sample from less to more. Based on the diagram of Fe-Mn- [Cu Ni] 脳 10] Fe-Mn- [Cu Co Nix 脳 10] and the value of mn / Fe, it is found that M38D-14) is the cause of hydration.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P744;P736

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