【作者】 周渭；

【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， 硕士

【摘要】 本论文依托国家“908”海洋底质调查专项项目,以CJ19区块（环海南岛海域,琼州海峡一带除外,下文相同）190个海底表层沉积物样品和7组柱状沉积物样品为对象,针对其中特征性的11个海底表层沉积物样品中的链状硅酸盐矿物中辉石和角闪石进行了成因及物源研究。具体研究工作主要借助光学显微镜、电子探针成分分析和扫描电镜微形貌观察技术手段和方法展开。首先对CJ19区块海底表层沉积物中涉及矿物的种属与颗粒百分含量进行了分析研究,进行了研究区域内碎屑矿物中重矿物的颗粒百分含量填图,同时通过对辉石与角闪石颗粒百分含量的矿物学填图,认为研究区辉石和角闪石含量分布趋势不尽相同,在海南岛东部海域辉石与角闪石均呈近岸富集远岸缺失的趋势,而在岛西部角闪石依旧符合近岸富集远岸缺失的分布,辉石则出现近岸缺失远岸富集的情况。综合认为在环海南岛近海海域,辉石与角闪石的物源情况基本统一,仅在岛西部海域存在一定差异。对辉石和角闪石做了双目镜下宏观形貌的观察和记录,发现该海域内表层沉积物中的辉石和角闪石颗粒均遭受不同程度的搬运剥蚀;通过借助电子探针测定的辉石和角闪石矿的化学成分,结合前人对辉石和角闪石成分标型的研究成果,认为该海域表层碎屑沉积物中的辉石主要为产自深成岩中的普通辉石;角闪石主要为透闪石-阳起石-镁角闪石类,其中透闪石-阳起石主要产自与热液有关的区域变质岩中而镁角闪石系列主要产于酸性岩浆岩中。并对辉石角闪石颗粒进行了扫描电镜微形貌的观察,并同时对电镜下观察到的矿物颗粒的侵蚀情况进行了矿物成分变化的能谱分析,发现在辉石和角闪石中,矿物遭受侵蚀的现象经常伴随Na⁺、K⁺、Ca²⁺、Mg²⁺等离子的流失。最后综合研究环海南岛近海海底地形地貌、洋流与季风风力等因素以及海南岛上相关入海河流流域的地质背景情况,对研究区域内碎屑矿物的物源进行了深入的探讨得出结论,认为环海南岛海域近海沉积物中碎屑矿物尤其是其中的辉石和角闪石,其主要物源是海南岛本土,物源物质迁移的方式主要有风沙沉积、河流带入和海岸侵蚀三类。更多还原

【Abstract】 The dissertation is supported by the Chinese Offshore Investigation and Assessment, the 908 Sub-project. In this project, the study area is around Hainan Island except Qiongzhou Strait and takes 190 surface sediments and 7 groups’sediments cores as researching samples.In this dissertation, inosilicate minerals: pyroxenes and hornblende which locate in 11 surface sediments samples have been chose for the research about its genesis and sediment source in the area. The microstructure and the compositional classification of the pyroxenes and hornblende in the chose samples have been examined by using optical microscope, scanning electronic microscope （SEM） and quantitative electron probe microanalysis （EPMA）.Firstly, all the minerals in surface sediments have been analyzed and map which involved the minerals classification and the grain’s percent, then the mineralogical mapping for the grain’s percent about pyroxenes and hornblende has been used to figure out the tendency of spatial distribution of them. Under binocular stereoscope, the particle morphology of pyroxenes and hornblende has been observed and recorded and found that in the research area, both of them have suffered denudation during the sedimentation process. The chemical composition of the pyroxenes and hornblende in samples has been tested by EPMA. Combing the existed conclusions about the typomorphic chemical composition of minerals, the result of EPMA indicate that, in this area the most of pyroxenes are augite, coming from plutonic rock and hornblende are in the type of tremolite, actinolite and magnesio-hornblende, among them the tremolite, actinolite is from regional metamorphic rocks which is relate to hydrothermalism and accompanying metasomatism and the magnesio-hornblende is from acid magmatic rocks.The microstructure pyroxenes and hornblende has been observed from SEM, meanwhile combining the Energy Spectrum Analysis, it is found that following thedenudation process, the ions like Na⁺、K⁺、Ca²⁺、Mg²⁺ are corroded from pyroxenes and hornblende.In the end, given all the facts like the bottom geomorphology of offshore around Hainan Island, the ocean current and monsoon, and also the flood events in the Hainan Island on the sediment flux to the sea with its geology background, the sources of the sediments in this area has been deeply discussed and concluded. The conclusion is that the sediments in the offshore around Hainan Island especially the pyroxene and hornblende mostly come from the Hainan Island and the transportation includes sandy wind deposit, fluxing by river and coastline erosion.更多还原