【作者】 孟庆勇；

【导师】 李安春；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 环境科学， 2006， 硕士

【摘要】 本论文旨在分析东菲律宾海帕里西维拉海盆柱样沉积物的磁性特征,以磁学参数的测量为手段,了解沉积物中所含磁性矿物的种类和含量,并分析其成因和意义,探讨研究区沉积物磁性矿物的来源,以及其所反映的古环境和古气候的演变,提供环境磁学方面的证据。对研究区内七个柱样进行了古地磁测试,通过系统的交变退磁,得到特征磁磁倾角,据此进行磁极性期和事件划分,通过与标准极性年表比对,发现大多数柱样有清晰的高斯正极性期/松山反极性期界限,能显示到松山反极性期,并可识别出哈拉米洛正极性事件,大体判定柱样沉积物底界的年龄。根据岩芯极性带界线产出深度,参照极性年代表推算了柱样沉积物的平均沉积速率。柱样磁化率值不高,随深度变化的曲线表现出一定的韵律性,相邻柱样的曲线特征也具有相似性。对帕里西维拉海盆西侧F090102柱样进行了系统的岩石磁学研究,测量了天然剩磁倾角、磁化率、等温剩磁、非磁滞剩磁、饱和等温剩磁等磁学参数,并进行了热磁分析。识别出松山反极性期内的哈拉米洛和奥都威正极性事件。对磁学参数及其有关比值的研究发现,岩芯磁性矿物以低矫顽力磁铁矿为主,含有少量高矫顽力磁性矿物。热磁分析发现,柱样顶段和底段沉积物除了主要的磁铁矿,可能含有一定量的钛磁铁矿,而中间部分冷却曲线位于加热曲线下方,居里点在550℃左右,可能是钛铁矿,并含有较多的富铁相钛赤铁矿。柱样沉积物中磁性矿物主要是陆源碎屑成因,岩芯底段受到海底火山作用的影响。根据磁学参数随深度的变化将岩芯分为三段,反映出沉积环境和古气候的变化。更多还原

【Abstract】 This paper presents the results of systemic paleomagnetism investigation anddetailed rock magnetic investigation of the marine sediments from the East PhilippineSea on the basis of the application of the newly developed environmental magnetictechniques. The research of multiple magnetic parameters shows the sorts and contentof magnetic minerals in sediments. The source of magnetic mineral, the paleoclimaticvariation and sedimentary environmental changes were discussed, and theenvironmental magnetic evidence was provided.A systemic alternating field demagnetization has been done on the seven cores.We have got the characteristic remnant magnetism of all the samples. A comparisionof geomagnetic polarity of marine sediments with the geomagnetic polarity time-scaleby A.Cox has been made, we discovered the clear boundary between Bruhnes normalepoch and Matuyama reversed epoch in most cores, the Jaramillo event during theMatuyama period was identified. The age and rate of accumulation of the sedimentshave been estimated.The susceptibility value of marine sediments is relatively low and its curvefluctuates rhythmically. A detailed magnetic analysis has been done on the coreF090102 from the Parece Vela Basin, the following magnetic parameters weremeasured: susceptibility (χ), anhysteretic remnant magnetization (ARM), isothermalremnant magnetization (IRM), saturation isothermal remnant magnetization (SIRM),IRM-300mT (induced in a field of -300mT) and typical temperature dependence ofmagnetic susceptibility curves (χ-T). First, a magnetostratigraphic record wasobtained. The Bruhnes-Matuyama reversal, the Jaramillo event, as well as the Olduvaievent during the Matuyama period, were identified. Analyses of magnetic parametersdemonstrated that magnetic minerals in the sequence were dominated bylow-coercivity ferromagnetic minerals with subordinate high-coercivityantiferromagnetic minerals. The χ-T curves results indicate that the magneticmineralogy of the upside and bottom of the core is dominated by magnetite, maybesome titanomagnetites are included, but for the middle parts of core sediments, thecooling curves are under the heating curves, the Curie temperature is about 550℃,maybe ilmenite and some iron-enriched titanohaematite are included. The resultsshow that the rock-magnetic parameters well correspond to the paleoclimaticvariations and sedimentary environmental changes.更多还原