【作者】 吴敏；

【导师】 李胜荣；

【作者基本信息】 中国地质大学（北京） ， 矿物学、岩石学、矿床学， 2007， 博士

【摘要】 粘土矿物在现代海洋环境中分布十分广泛,是海洋沉积物的重要组成部分。海洋沉积物作为一个巨大的信息库,储存着丰富的有关地球历史、环境演化的信息。粘土矿物由于其结构和物理、化学性质的特点,在形成及演变过程中携带着丰富的气候变化信息,分布广泛又容易取样,早已成为古气候研究的有效辅助研究对象之一。本次研究首先采用X射线衍射分析(XRD)方法厘定了海南岛近海沉积物中粘土矿物的种类和相对含量。357个样品的XRD分析结果显示,该研究区的粘土矿物主要由伊-蒙混层矿物、伊利石、高岭石和绿泥石等组成,其中182个表层样品中上述4种矿物的平均含量分别为34. 2%、27.3%、21.1%和17.4%。在南海沉积物中发现高含量(>1/3)的伊-蒙混层矿物存在尚属首次,为此就其成因做了专门的探讨。采用人工判别分区和Q型聚类分析分区相结合的方法,划分出了3个表层粘土矿物组合区。结合海南岛本土的地质背景和相关水动力特征,进一步探讨了粘土矿物的成因、来源和受控因素。参照前人关于伊-蒙混层矿物、伊利石和高岭石的气候标识研究结果,依据表层沉积物(0～20cm)AMS14C定年的结果,认为1500a以来海南岛及周边区域一直处于比较温湿气候环境的结论。其次对7个沉积柱(175个样品)中的粘土矿物进行了含量、分布特征及其指示意义的分析,探讨了各柱的沉积环境和物质来源,并根据沉积扰动事件推断海南岛近海区域,约在3500～6000Cal.aBP期间,水动力作用强烈,气候比较动荡。最后依据B106沉积柱AMS14C定年数据和其粘土矿物的定量结果,参照对比前人采用其它研究方法和研究对象获得的古气候环境事件结论,提出用(伊-蒙混层矿物+伊利石)/高岭石含量比值的矿物学指标来指示古气候环境事件。研究结果显示,B106柱的粘土矿物学指标指示出16725 Cal.aBP以来的7次古气候变化事件,分别是13100±45 aBP的“博林暖期升温事件”、10393±45 aBP的“新仙女木降温事件”、8000 Cal.aBP对应的“全新世最大降温事件”、4624±35 aBP的“中国南方降温事件”、3370±40 aBP的降温事件、922BC的干旱降温事件和514 AD的“南北朝降温事件”。这说明在一定条件下利用海洋沉积柱粘土矿物组合、含量的变化特点,也可以揭示千年尺度的古气候环境变化事件。更多还原

【Abstract】 Clay minerals are a widely distributing phenomenon in modern marine environment. And become the important components of the marine sediments which act as an enormous information basement storing abundance messages about the globe history and environment evolvement. Because of the structural characteristic and physic– chemical properties, during the proceeding and evolution disciplinarian, clay minerals carries along rich information about the global climate change. Meanwhile considering the widely distributing and easily sampling, clay minerals has become the one of effective auxiliary research subjects for the paleoclimate research.The investigation firstly using the X-RAY Diffraction Analysis (XRD) to fix on the variety and relative content of the clay minerals in offshore sediments around Hainan Island. The XRD analytical results from 357 samples show that, in the research area the clay minerals are composed by illite/smectite interstratified clay minerals, illite, kaolinite and chlorite. In 182 surface sediments samples, the average content of the four types is about 34.2%, 27.3%, 21.1% and 17.4%. In Sediments of the Central South China Sea, it is the first time to discovering the high-content (>1/3) of illite/smectite interstratified clay mineral. So in the investigation, the genesis of it has been discussed especially. For giving the accuracy judgment of the assemblages characteristic and the distributed tendency of the clay minerals in surface sediments, the investigation use the method that combining the two way for the subarea: the manual distinguishing and the Q-type Clustering Analysis and divide the 3 surface clay mineral association area. Combining the geology environments and hydrodynamic characteristic in Hainan Island, the article further discusses the genesis and controlled factors of clay minerals. Comparing the future research on using illite/smectite interstratified clay minerals, illite, kaolinite and chlorite as the identification of climate, according to the dating for AMS14C in surface sediments(0~20cm), this article found that in Hainan Island and its peripheral districts the climate environment has been in wet and warm since 1500a.Secondly, the investigation analyzes the contents and distribution of the claymineral in the 7 sediments core (175 samples) and the significance of them. Then discuss the material resources and depositional environment of each core. According to the disturbed events of deposit , it deduce that climate was fluctuated in the years of 3500～6000Cal.aBP in this area.At last, using the qualitative and quantitative analyzing of the clay mineral in the offshore sedimentary core B106 from Hainan Island and according to the dating for AMS14C, meanwhile comparing the future research on palaeoclimate environmental event, which using different methods and subjects, this article found that from the content ratio about (illite/smectite interstratified clay minerals+ illit)/ kaolinite ([I/S+I]/K) can also indicate the palaeoclimate environmental event. The results showed that clay mineral of the sedimentary core B106 reveal seven palaeoclimate events since 16725 Cal.aBP, such as“Bolling Warming Events”in 13100±45 aBP,“Younger Dryas Cooling Events”in 10393±45 aBP,“Early Holocene Cold Event”in 8000aBP,“South of China Cooling Events”in 4624±35 aBP, Cooling Events in 3370±40 aBP, Drought Incident Cooling Events in 922BC and“Cooling Events of Northern and Southern Dynasty”in 514AD. All of those corresponding events show that under certain conditions using the result of the analyzing about clay mineral in marine sedimentary core also can reveal the palaeoclimate environmental event around 1ka scales.更多还原