【作者】 李震；

【导师】 雷怀彦；

【作者基本信息】 厦门大学 ， 海洋地质， 2007， 硕士

【摘要】 对海洋沉积物特征进行分析是海洋地质学的一个基本内容,也是研究近代沉积作用的核心问题之一(Morton et al,1991),它是沉积物分类的基础,既体现了沉积物物理化学性质的本质,又主导着沉积物的历史演变。有关海洋沉积物方面的研究几乎都涉及到粒度分析和矿物分析。其中,表层沉积物的粒度特征是进行物源追踪和沉积环境分析的基础,每一沉积体系都可以看作是有关沉积物环境(包括水动力条件、物源供应、生物活动等)及沉积物组成(物理和化学)等因素的复杂函数。同时,研究海洋沉积物中的碎屑矿物,可以解决有关海洋沉积物的矿物组成、分布规律及物质来源等问题,从而进一步阐明蚀源区的母岩成分以及各类矿物入海后的分异规律,在海洋环境变迁、海洋矿产资源开发、海洋环境保护、港口建设与整治、相邻沿海国大陆架的划界,以及海洋沉积学理论的发展等方面均有特殊而重要的科学意义,是海洋沉积学研究的重要内容。本文依托福建省基金项目《福建海岸风沙形成机理及危害的防治研究(D0410009)》和与台湾合作横向课题《金门海岸防护对策暨渔村海岸复育可行性研究》,就上述两个方面,选择水动力条件复杂的厦门港作为研究区域,通过激光粒度分析、轻重矿物分析和聚类分析对厦门港表层沉积物的粒度类型、粒度分布特征、矿物组分及轻、重矿物的水平变化特征进行研究,探讨了研究区表层沉积泥沙的分布、物质来源及其与沉积环境的关系,为合理地开发利用海湾资源、保护航道稳定、发展厦门特区的海运事业从而促进周边地区的经济建设提供科学依据。1.利用激光粒度仪(Mastersizer2000)对研究区36个海底表层沉积物样品进行粒度测试,并根据各粒级百分含量和粒度参数绘制等值线分布图,结合水动力条件对厦门港的粒度分布趋势进行分析。结果表明,港内底质类型主要有四种:粘土质粉砂(YT)、砂-粉砂-粘土(STY)、粉砂质砂(TS)、砂质粉砂(ST)。其中粘土质粉砂(YT)为区内分布最广泛的沉积物类型。沉积物分布特征主要受水动力条件和泥沙来源影响。径流、潮流相互作用强烈的地方,水动力减弱有利于泥沙的沉降,是砂粒组分和矿物富集区。2.利用体式和偏光显微镜对36个样品的碎屑矿物特征进行鉴定,并对重矿物进行R型和Q型聚类分析。分析表明厦门港内表层沉积物中碎屑矿物种类较多,多为陆源碎屑矿物,其中轻矿物9种,重矿物49种。轻矿物含量较高,以长石、石英、片状云母类为主;重矿物以磁铁矿、褐铁矿、帘石类、云母类、闪石类为主。根据聚类分析结果,结合主要重矿物含量及其分布特征可将研究区划分为四个矿物区,各区的重矿物含量不相上下,区别各个分区的主要因素是次级矿物钛铁矿、角闪石、片状矿物和自生黄铁矿的颗粒百分含量。3.计算并分析重矿物特征指数,结合水动力环境、粒度分布特征,认为研究区沉积物主要为近源物质,物源区为九龙江流域及其河口区包括港湾周缘陆地广泛分布的燕山期不同期次的酸性、中酸性侵入岩和火山岩及动力变质岩。4.从研究区整体的粒度组成来看,粉砂级粒组含量占优势地位,而砂组分的含量明显偏低,说明研究海区水动力较弱,处于一个低能环境。在重矿物中,指示还原环境的自生黄铁矿出现机率较高,也证明了研究海区大环境是弱还原、低能环境。更多还原

【Abstract】 The analysis of marine sediments is a fundamental content of marine geology, and also one of the core problems in deposition researches nowadays. As the foundation of deposit classification, it not only embodies sediment’ s essence of the physical and chemical characteristics, but also dominates the historical evolution. The research of marine sediments is almost involving analysises of the particle size and mineral. Among these, the character of particle size in surface is the basis of trace sediment provenance and sedimentary environment analysis. Each deposition system can be regarded as a complicated function of some factors: the sediment environment (including hydrodynamic conditions, sediment supply, biological activity, etc.) and the sediment composition (physics and chemistry), and so on. At the same time, the study of fragmentary mineral can resolve some problems about marine sediments such as the composition of fragmentary mineral、distribution characteristic、sediment source and so on, so as to expound the component about parent rock and the difference of the mineral when they dissolve into the sea further. It has importantly scientific meanings in the study of the marine environment changes, oceanic mineral resources exploitation、marine environment protection、port construction and renovation、adjacent coastal continental shelves and the sea sedimentology theory development , and it is a important content of marine sedimentology.This article relies on the Fujian Province fund project and transverse direction problem cooperating with Taiwan, choosing Xiamen harbor where has the complex hydrodynamic force as the study area. To explain two above-mentioned aspects, use the laser grain size analyzer, light and heavy mineral analysis and cluster analysis to study, and discuss sediment’ s distribution, source and the relationship whit sedimentary environment. Provide the basis for the reasonable exploitation and to utilize bay resource, and to protect channel stability、to develop Xiamen’ s marine transportation enterprise, and to promote periphery area economic development.1. Grain size analysis of the 36 suficial samples from the study area was carried out by using the laser grain size analyzer. Isoline distributing chart is protracted according to percents of each level and parameters of granularity .Combination the chart and hydrodynamic conditions analysizes granularity distributing trends of Xiamen port . The result is following: Sediments in the area could be divided into 4 types: clayer silt、sand-silt-clay、silty sand and sandy silt, and clayer silt take the majority. Distribution of sediment is mainly affected by hydrodynamic conditions and sediment sources. The area where runoff and tidal current interact strongly and the hydrodynamic force becomes weak in favor of sediment subsidence, is enriched area of sand and heavy mineral.2. Clusters of 36 samples are identified by using microscopes, and heavy minerals are analyzed according to R and Q types clustering. The results show that there are 9 kinds of light minerals, 49 kinds of heavy minerals. Light minerals take the majority. The dominant and characteristic minerals are magnetite、limonite、epidote、mica and amphibole. Four mineral assemblage zones can be divided based on the result of clustering analysis and heavy mineral contents and the distribution characteristics.3. According to Computing and analyzing characteristic index of heavy mineral, combining dynamic conditions and granularity distributing characters , deem that the source of sediment is nearby harbor and the source regions include Jiulong River watershed and peripheral land, where distribute acidic intrusive rocks、neutral intrusive rocks、volcanic and dynamo-metamorphic rock in Yanshanian.4. From the size composition in study area, the content of silt is dominate. Relatively, the content of sandy is lower. The result shows that the hydrodynamic force is weak. In the result of heavy mineral identification shows that the chance of occurrence of autogenic pyrite which indicates reducing environment is higher, and proves the study area is a weak reducing and low-energy environment.更多还原