【作者】 张振国；

【导师】 方念乔；

【作者基本信息】 中国地质大学（北京） ， 海洋地质， 2007， 博士

【摘要】 本研究以产出于南海北部陆缘西沙海台的多金属结核为主要对象,以太平洋、印度洋等海域的样品为参照,对南海结核进行了矿物学、地球化学及成矿环境等方面深入、系统的探讨。在研究中应用了矿相显微镜、高倍电子显微镜、电子探针、X射线粉晶衍射(XRD)、等离子质谱仪(ICP-MS)和等离子光谱仪(ICP-AES)等观察仪器及测试分析设备;利用了钙质超微生物地层学的定年方法。研究内容包括结核的形态、矿物的组成、元素分布及含量、元素间的相关关系、多元图解和配分模式;结核的生长年代、生长速率及结核的赋存环境和成矿意义。主要取得了以下成果:1.完成南海北缘西沙海台大型多金属结核基本特征的鉴定,确定南海结核与太平洋、印度洋等大洋结核,波罗的海、南海东北部陆坡等边缘海结核,地球化学特征存在明显差异,是一种边缘海环境条件下赋存的新型多金属结核。2.根据南海多金属结核元素和矿物组成特征,确定南海结核样品为水成成因,并据此讨论了区域构造-沉积因素对结核形成和生长过程的控制作用。3.根据南海结核化学元素的相关关系:Mn与Mg、Cu、Ni、Al、Ca呈较强的正相关;Fe与Co、Zn、Ti、Pb、Sr、∑REE呈较强的正相关;Mn+Fe与Mg+Al+Si为强负相关;Cu+Ni+Co与Fe+Mn较强负相关。认为Fe、REE等元素主要来源于陆源碎屑沉积物,Mn、Cu、Ni等来自深层海水;结核壳层金属含量的变化,与沉积环境的变化密切相关,陆源物质供应量的增加对Mn、Cu、Ni、Ca等元素的富集产生明显的稀释作用。4.首次利用钙质超微化石地层学方法,将结核的初始生长年代限定在1.7Ma左右,据此推断结核的生长速率高达15.38mm/Ma。这一远远高于常速的快速生长的结核类型,可能是边缘海特定环境下物源供应条件充分的结核生长发育的特例。5.综合探讨了南海多金属结核形成过程的构造地理环境特征及对其产生强烈制约相应的重大地质事件。认为独特的地理位置和海底地貌、充足的矿物供应、良好的古海洋条件是结核生长、发育的前提;其生长环境受青藏高原的隆升、末次冰期等重大地质事件的制约;其成长发育过程记录了大量古海洋、古气候、古环境的信息,对探讨南海区域环境的演化,乃至全球性环境演变都具有重要意义。更多还原

【Abstract】 The polymetallic nodules collected from the northern continental margin of the South China Sea are used in this study. Samples of diferent nodules which are from the Pacific and the Indian Ocean are discussed in details with mineralogical and element geochemical method. This study showed great value on the theoretics and the appliance.The study used various observations and analytical techniques such as electron microprobe analysis, X- ray difraction ( XRD). Elemental content data of polymetallic nodules are obtained by ICP- AES and ICP-MS techniques. The chronology is mostly based on the calcareous nannofossils from the sample. The studies are including of elemental composition, content and distribution, the ratio among different elements, elemental assemblage, triangular diagram analysis and REE distribution pattern. The minerogenetic environment of the polymetallic nodules are discussed in this article. The following results have already been achieved:1. According to internal structure features, the microstructure can be classified into 12 different types in the polymetallic nodules. The XRD, ICP-AES and ICP-MS data show different characteristics from different areas. Sample of the South China Sea is rich in Fe, Si, and∑REE, and is poor in Mn, Cu, Co, Ni and Mn/Fe. Elements correlation of w(Mn)-w(Fe)-the w(Cu+Ni)×10 suggest that the origin of the sample may be of hydrogenic.2. The chemical compositions of polymetallic nodules which are collected from the South China Sea, northeastern Pacific Basin, northwestern Pacific Seamount and central Indian Ocean Basin are studied in this article. The sample of the South China Sea has many particular characteristics on main elements, trace elements and rareearth elements (REE), and is easily different from the oceanic nodules and the nodules which are obtained from the Baltic and the Okinawa Trough. The sample has lower rates on Cu, Co, Ni, and Mn/Fe (0.73). The REE expresses very special characteristics of the sample. It has higher content than oceanic nodules (1.8). The heavy REE (HREE) depleted relative to the light REE (LREE) very obviously (19.54), because the HREE have formed more stable complexes in seawater than LREE. The distinct enrichment ofδCe and unusual negative ofδEu indicates strong oxidize oceanic environment of the study areas.3. According to the correlated coefficient analysis, there are positive relations among Mn, Mg, Cu, Ni, Al and Ca, also Fe, Co, Zn, Ti, Pb, Sr and∑REE. There are negative relations between Mn+Fe and Mg+Al+Si contents, Cu+Ni+Co and Fe+Mn contents. The content ration of Fe increases from the inner crust to the outer one, with that of Cu and Ni decreasing in different ways. It shows that the growth of the nodules was affected by the environmental fluctuations and changing supply of the terrigenous sediments and Mn, Cu, Ni, and Ca. The nodules are typically hydrogenetic in marginal sea environment.4. According to the chronology correlation of calcareous nannofossils, the growing age of the polymetaic nodule has been identified. The geological age is limited to 1.7Ma, and the growth rate is about 15.38 mm/Ma. The nodule may represents a new type which grows fast in high deposition velocity environment.5. Based on the detailed study of the geochenistry and growth rate, the minerogenetic environment is discussed in this paper. The nodule can grow fast because the north of the South China Sea has better conditions on forming mechanism and environments, such as special geography position, ample mineral supply and good paleoceanic conditions. In addition, its growth process can record a lot of palaeoceangraphic, palaeoclimatological and palaeoenvironmental information. This study will achieve in explaining regional environmental changes even global environmental evolution.更多还原