南海北部沉积物中黄铁矿分布特征及其对天然气水合物的指示意义

发布时间：2018-06-05 01:45

本文选题：自生黄铁矿 + 扫描电镜　；参考：《厦门大学》2014年硕士论文

【摘要】：本论文通过对采自南海北部的柱状沉积物样品的总硫含量、总有机碳含量进行实验分析以及借助带能谱仪的扫描电镜(SEM)对保存在沉积物中的黄铁矿的亚微结构特征,进行初步探讨研究。查明在天然气水合物赋存区的黄铁矿的垂向分布特征以及在平面上的变化特征,同时对黄体矿的晶体形貌特征和成因机制进行了研究,并对早期成岩过程中黄铁矿的发育与甲烷气体之间的相互作用进行了有益探讨。得到了以下几个方面的主要认识： (1)2B、3B、5A、6B4个站位在平面上黄铁矿总量的变化特征为神狐海域的5A站位含量最高,东沙海域的3B、2B站位黄铁矿含量次之。4个站位的黄铁矿垂向上的分布特征为,多数集中在300cm～700cm层段处。3B站位的黄铁矿含量的最大值区域位于350cm层段,次峰值区位于560cm层段；2B站位的黄铁矿峰值区在405cm层位,5A站位的黄铁矿峰值区在360cm层位,2B站位和5A站位次峰值区都分布在705cm～710cm层位。 (2)2B、3B、5A、6B站位浅表层柱状沉积物中的总有机碳(TOC)含量为0.37%～1.18%,平均值为0.71,总硫(TS)含量为0.04%～0.81%,平均值为0.30%,黄铁矿(FeS2)含量为0～0.71%,平均含量为0.23%,TOC、TS和黄铁矿含量随着沉积物埋藏深度增加逐渐增大,达到峰值后逐渐减少,三者的分布趋势基本一致。黄铁矿是沉积物中硫化物的主要形式,甲烷的厌氧氧化作用(AOM作用)对黄铁矿的形成起主要的贡献作用。 (3)在扫描电镜(SEM)下观察到黄铁矿,其产出形式大部分为莓球状集合体和八面体微晶形貌。正八面体的单体黄铁矿粒径较大,形成的集合体粒径也较大,在局部层位还发现少量的管状的、生物内膜状的以及立方体状的黄铁矿晶体。有机质含量在很大程度上影响了黄铁矿的含量分布,在TS含量的高值区,黄铁矿含量亦处于峰值,少部分层位的相关性不明显,为其他硫化物对TS含量的影响。3B、5A、6B站位均位于南海北部陆坡天然气水合物远景区,地层中深大断裂发育,浅表层环境为极端还原环境,甲烷厌氧氧化作用活跃,陆源物质带来的铁源与该环境中的硫源易形成自生黄铁矿。黄铁矿的莓球状产出,亦指示该背景为充气富氧和局部的缺氧环境。
[Abstract]:In this paper, the total sulfur content and total organic carbon content of the columnar sediments collected from the northern part of the South China Sea were analyzed experimentally, and the submicrostructural characteristics of pyrite preserved in the sediments were studied by means of scanning electron microscope (SEM) with energy spectrometer. A preliminary study was carried out. The vertical distribution of pyrite in the gas hydrate region and its variation on the plane are investigated. The crystal morphology and genetic mechanism of the luteinite are also studied. The interaction between the development of pyrite and methane gas during the early diagenesis is also discussed. The following key aspects were recognized: The variation characteristics of the total amount of pyrite in the plane are that the content of pyrite at 5A station is the highest in Shenhu area, followed by the pyrite content at 3BX 2B station in Dongsha Sea area. The vertical distribution characteristics of pyrite in 4 stations are as follows. Most of the pyrite content at station. 3B of 300cm~700cm is located in the 350cm layer. The sub-peak area is located in the pyrite peak area of the 560cm section and the pyrite peak area at the 405cm level and 5A station. The pyrite peak area in the 360cm layer is located at the 360cm layer and the sub-peak area at the 5A station is located in the 705cm~710cm layer. The total organic carbon (TOC) content in the shallow surface columnar sediments at the station No. 2B2B2BC5A5A6B was 0.370.18 with an average value of 0.71, the total sulfur content was 0.040.81, the average value was 0.30, the content of pyrite FeS2 was 0.0.71, and the average content of 0.23TOCnTS and pyrite gradually increased with the increase of the depth of burial of the sediments, and the total organic carbon (TOC) in the columnar sediments of the shallow surface was 0.371.The average content of TOC was 0.371.The average value of TOC was 0.71, and the content of TSC was 0.040.81, the average was 0.30. After reaching the peak value, the distribution trend of the three is basically the same. Pyrite is the main form of sulfides in sediments, and the anaerobic oxidation of methane (AOM) plays a major role in the formation of pyrite. (3) Pyrite was observed under scanning electron microscope (SEM), and most of the pyrite was produced in the form of globular aggregate and octahedral microcrystalline morphology. The size of pyrite monomers of octahedron is larger and the particle size of formed aggregates is larger. A small number of tubular, biofilm and cubic pyrite crystals are also found in local layers. The content of organic matter affects the distribution of pyrite content to a great extent. In the high value region of TS content, the content of pyrite is also at the peak, and the correlation of a few layers is not obvious. For the influence of other sulfides on TS content. The stations. 3B- 5AY6B are located in the natural gas hydrate area on the northern slope of the South China Sea. The deep faults in the strata are developed, the shallow surface environment is an extreme reduction environment, and the anaerobic oxidation of methane is active. Tie Yuan from land-based sources and sulfur sources from the environment are prone to form authigenic pyrite. The raspberry globular production of pyrite also indicates that the background is aerated oxygen-rich and partially anoxic.
【学位授予单位】：厦门大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P744;P618.31

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