【作者】 佟景贵；

【导师】 叶大年； 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】 能源、资源和环境问题是当今地球科学的三大前缘领域,特别是古海洋环境问题,由于我国海洋地质调查起步较晚,古海洋的研究远远落后于发达国家,在古海洋研究中,最关键的问题之一是如何确定大洋沉积物的时间坐标,并将大洋沉积物的组合特征于全球变化联系起来。富钴结壳记载了晚白垩纪以来的古环境和构造活动信息,具有高密度压缩信息的优点,利用富钴结壳进行古海洋、古环境及全球变化的研究具有重要意义。文中结合超低Sr本底流程,实现了单颗有孔虫化石87Sr/86Sr比值高精度测定,对今后有孔虫Sr同位素研究与应用具有重要意义。利用所获得的有孔虫化石87Sr/86Sr比值确定了西太平洋富钴结壳碳酸盐基岩中有孔虫化石的年龄为0.91 +0.33/-0.39Ma,解决了海山富钴结壳碳酸盐基岩中有孔虫化石定年的难题。利用有孔虫化石Mg/Ca值的激光剥蚀等离子质谱测定结果,获得0.91Ma±西太平洋麦哲伦海山区海表温度为24.9+1.1/-1.0℃。在矿物学基本特征分析的基础上,对中太平洋WM1和WX海山富钴结壳中的主量元素、微量元素、稀土元素和铂族元素的含量、层间变化及其相关性进行了研究,得出:青藏高原的隆升以及亚洲季风演化可能是造成结壳中的粘土矿物和石英等碎屑矿物从下层到上层增多的重要原因;结壳的氧化性由下层到上层增高,海山的沉降可能是造成结壳生长后期环境氧化性增强的重要原因;磷酸盐化的过程对铁锰结壳吸附Co的能力起到抑制作用;结壳的磷酸盐化过程对Pt和∑REE的富集起到了重要作用。结合Co定年、10Be定年和磷酸盐Sr同位素定年等定年方法,对中太平洋富钴结壳WXD27的年代学进行了研究。上部铁锰结壳与上层白色磷酸盐化层接触部位的年龄为14.9Ma,14.9Ma以来,结壳的生长是连续的,沉积间断发生的可能性非常小。白色磷酸盐化层与其上部的富钴结壳之间存在4Ma的沉积间断;19-22.7Ma BP左右,在该区发生过大规模的磷酸盐化作用,磷酸盐化作用可能造成磷酸盐化时期和之后4Ma的铁锰结壳的沉积间断;结壳的初始生长年龄在75Ma左右;老结壳的生长速度远低于新结壳的生长速度,这可能与老结壳形成于相对还原性更强的环境有关。通过化学方法提取中太平洋富钴结壳中的粉尘,经微量Nd同位素测试得到,富钴结壳WXD27上部粉尘(0-6.9Ma)的εNd落在中国黄土范围内,中部粉尘(14.9-10.8Ma)的εNd较高。结合Al电子探针的线扫描分析及X射线粉晶衍射分析,可得出上部结壳提取物与中国黄土同源,为亚洲季风作用结果;中部结壳提取物中除亚洲季风携带粉尘贡献外还有火山灰的贡献,说明在8.8Ma BP、10Ma BP尤其是11.8Ma BP中太平洋火山活动强烈。结壳中风成粉尘沉积速率分别在8Ma BP、4-2.5Ma BP、2.5Ma BP三个阶段迅速增加,8Ma BP粉尘沉积速率的高值为青藏高原隆升的环境响应;4-2.5Ma BP的高值代表冬季风的加强(这个时期夏季风也加强),同样为青藏高原迅速隆升的响应;2.5Ma BP以来粉尘增加有利于全球变冷,导致并且不断地发展或加强。更多还原

【Abstract】 Ferromanganese crusts compress informations of palaeoenvironment and tectonization since cretaceous with high density and are significant to study palaeoceanic, palaeoenvironmental and global changes.Analysis of single-grain foraminifera from carbonate basements of ferromanganese crusts was successively conducted by a combination of low Sr procedural blank and high precision determination of 87Sr/86Sr ratio, which can be significant for the study and application of Sr isotopic composition of foraminifera. Based on the obtained value of 87Sr/86Sr ratio, the analyzed foraminifera can be dated at 0.91 +0.33/-0.39Ma, which is significant for very difficult-dating foraminifera in carbonate basements of ferromanganese crusts. The foraminifera were analysed for their Mg/Ca with LA-ICP-MS, and with the data of which, the SST of a Magellan seamount in Westpacific was produced at 24.9+1.1/-1.0℃The interelemental correlation in Co-rich crusts from the Mid-Pacific seamounts of WM1 and WX and elemental variation in different layers of the crusts were studied and the study reveals that 1) the amount of hydrosyalites and quartzes increases gradually from lower layers to upper layers,which may be related to evolution of Asian monsoons and the uplift of the Himalaya - Tibetan plateau; 2) the oxidation increase from lower layers to higher layers of crusts, which may be caused by the sink of the seamounts;3) the enrichment of P restrained the adsorption of Co for crusts; 4) phosphatization played an important role in the enrichment of Pt and∑REE in ferromanganese crusts.Dating studies on Mid-Pacific ferromanganese crust were conducted by a combination of dating techniques of Co content, Be isotope as well as Sr isotope in phosphate. The age of the bottom of upper ferromanganese part contacting the upper phosphate layer is 14.9Ma and the crust had been grown continually and without sedimental interruption 0～14.9Ma. There is 4Ma sedimental interruption between the upper ferromanganese part and the upper phosphate layer. Great phosphatizations had happened in this area between 19 and 22.7 Ma BP which might cause the sedimental interruption during the phosphatizaions and 4Ma after them. The crust began to grow 75Ma BP. The growth rate of older crust part is much lower than that of the younger crust part, which can be explained that the environment where the order crust partoccurred is more reducing than that where the younger crust part occurred.Eolian dust in Mid-Pacific was extracted by chemical processes.εNd values of upper part of crust WXD27 (0-15mm depth; 0-6.9Ma) are in the range of those of Chinese loess, however,εNd values of lower part (25-37mm depth; 10.8-14.9Ma) are lower than those of upper part. By analyses of EPM( linear scan of Al) and XRD results of the samples as well as and theirεNd values, it can deduced that the source of upper dust and that of Chinese loess are same which means the upper dust is the result of Asia monsoon input, and that the lower part dust is the result not only monsoon input but also volcano input, which means the volcano activities were intensive 8.8Ma BP, 10Ma BP and especially 11.8Ma BP. Eedimental rate of eolian dust increased drastically 8Ma BP, 4-2.5Ma BP and 2.5Ma respectively. The increase 8Ma BP is the response to the drastic uplift of the Himalaya and Tibetan plateau. The high value of dust sedimental rate 4-2.5Ma BP represents enhance of winter monsoon and also the response to the drastic uplift of the Himalaya and Tibetan plateau. The increase of dust fluxes since 2.5Ma BP reflect that dust load in atmosphere increased, which maight induce the globe went into a great glacial epoch.更多还原