东马努斯海盆PACMANUS热液区Si-Fe-Mn氧化物的形成机制及其对热液活动的指示
发布时间：2018-11-02 18:38
【摘要】：在东马努斯海盆PACMANUS(巴布亚新几内亚 澳大利亚 加拿大 马努斯)热液区拖网取得了部分Si-Fe-Mn氧化物样品。通过分析Si-Fe-Mn氧化物的主量、微量和稀土元素含量,Sr、Nd、Pb同位素组成,探讨了Si-Fe-Mn氧化物的成因及元素含量的限制因素,研究了热液区Si-Fe-Mn氧化物的物质来源。利用PACMANUS热液流体端元组分的Si、Fe、Mn含量,分别绘制了300°C和25°C的Si-Fe-Mn-H2O系统热力学图解——布拜图。阐明了随温度降低,喷口流体中沉淀的Si-Fe-Mn氧化物种类和沉淀顺序,以及各类产物稳定存在的区域。根据光学显微镜下观察、扫描电镜、电子探针分析识别了样品中细菌作用形成的典型细丝结构,并探讨了生物作用与非生物作用在Si-Fe-Mn氧化物形成过程中的竞争机制、分析了无定形硅的沉淀作用。样品具有复杂的成因,以热液成因为主,受海水的影响较小。几乎没有深海远洋沉积物和火山碎屑物质的贡献。Sr和Nd同位素组成具有两个端元的物质来源。海水对样品贡献的Sr含量占总量的76.7%~83.1%。所有样品的Nd主要来自热液流体并保存了热液的信息。Pb同位素组成变化范围较小,主要来自东马努斯海盆的基底岩石。热力学图解布拜图显示当温度降低到25°C时,从热液流体中形成的Si、Fe、Mn氧化物种类主要为SiO2、Fe(OH)3、Fe3(OH)8、Mn3O4、Mn2O3。在热液流体与海水的混合过程中,由于SiO2的稳定区边界较低,因此SiO2会在Fe-Mn氧化物形成之前沉淀。然后Fe(OH)2先沉淀,Fe3(OH)8和Fe(OH)3随后沉淀,Mn3O4和Mn2O3最后沉淀。计算得到PACMANUS热液区Fe2+氧化为Fe3+的无机氧化速率为0.012 g/min,喷口周围一年内将形成约3.2 kg铁氧化物。网状细丝结构是生物作用的结果,这种疏松的结构既保证了充足的Fe2+供应,又阻止了海水中过量氧气的侵害,为嗜中性铁氧化细菌的生存提供了良好环境。同时,生物作用与非生物作用之间保持着既互相竞争,又互相促进的作用。样品中二氧化硅的沉淀过程主要分为两个阶段。第一个阶段是二氧化硅在富Fe的细丝状结构中生长,此时形态上基本由细丝状结构组成。当富Fe和Si的细丝结构成壳时,才会出现第二阶段的二氧化硅。此阶段细丝的尺寸增大,并且在细丝周围开始大量沉淀富Fe、Si的球状结构的集合体。
[Abstract]:Some samples of Si-Fe-Mn oxides were obtained by trawl in the PACMANUS (Papua New Guinea Australia) hydrothermal zone of the East Manus Basin. By analyzing the main amount of Si-Fe-Mn oxide, trace and rare earth element content and Sr,Nd,Pb isotopic composition, the origin of Si-Fe-Mn oxide and the limiting factors of element content are discussed. The source of Si-Fe-Mn oxides in hydrothermal region was studied. Based on the Si,Fe,Mn content of the end component of the PACMANUS hydrothermal fluid, the thermodynamic diagrams of the Si-Fe-Mn-H2O system of 300 掳C and 25 掳C have been drawn respectively. The species and order of Si-Fe-Mn oxides precipitated in nozzle fluid with the decrease of temperature, and the regions where the products exist stably are explained. According to the observation under optical microscope, scanning electron microscope and electron probe analysis, the typical filaments formed by bacterial interaction in the sample were identified, and the competitive mechanism between biological and abiotic interactions in the formation of Si-Fe-Mn oxide was discussed. The precipitation of amorphous silicon was analyzed. The samples are of complex origin, mainly hydrothermal origin, but less affected by seawater. There are almost no contributions from deep-sea pelagic sediments and pyroclastic materials. Sr and Nd isotopic compositions have two end-member material sources. The content of Sr contributed by seawater to the sample was 76.7% and 83.1% of the total. The Nd of all samples was mainly from hydrothermal fluid and kept hydrothermal information. The variation range of Pb isotopic composition was relatively small, mainly from the basement rocks of the East Manus basin. The thermodynamic diagram shows that when the temperature is reduced to 25 掳C, the main types of Si,Fe,Mn oxides formed from hydrothermal fluids are SiO2,Fe (OH) _ 3 Fe _ 3, (OH) _ 8, mn _ 3O _ 4 and mn _ 2O _ 3. In the process of mixing hydrothermal fluid with seawater, SiO2 precipitates before the formation of Fe-Mn oxides due to the lower boundary of the stable region of SiO2. Then Fe (OH) 2 precipitated, Fe3 (OH) 8 and Fe (OH) 3 precipitated, and Mn3O4 and Mn2O3 finally precipitated. The inorganic oxidation rate of Fe2 to Fe3 in the PACMANUS hydrothermal region is calculated to be 0.012 g / min, and about 3.2 kg iron oxides will be formed around the nozzle within one year. The reticular filament structure is the result of biological action. This loose structure not only guarantees sufficient supply of Fe2, but also prevents the damage of excessive oxygen in seawater, and provides a good environment for the survival of neutral iron oxidizing bacteria. At the same time, biological action and abiotic action maintain the role of competition and mutual promotion. The precipitation process of silica in the sample is divided into two stages. The first stage is the growth of silica in the filamentous structure rich in Fe, which is basically composed of filamentous structures. When the filaments rich in Fe and Si are formed into shells, the second stage silica will appear. At this stage, the size of the filaments increases and a large number of aggregates of Fe,Si rich spherical structures begin to precipitate around the filaments.
【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P736.3
本文编号：2306631
[Abstract]:Some samples of Si-Fe-Mn oxides were obtained by trawl in the PACMANUS (Papua New Guinea Australia) hydrothermal zone of the East Manus Basin. By analyzing the main amount of Si-Fe-Mn oxide, trace and rare earth element content and Sr,Nd,Pb isotopic composition, the origin of Si-Fe-Mn oxide and the limiting factors of element content are discussed. The source of Si-Fe-Mn oxides in hydrothermal region was studied. Based on the Si,Fe,Mn content of the end component of the PACMANUS hydrothermal fluid, the thermodynamic diagrams of the Si-Fe-Mn-H2O system of 300 掳C and 25 掳C have been drawn respectively. The species and order of Si-Fe-Mn oxides precipitated in nozzle fluid with the decrease of temperature, and the regions where the products exist stably are explained. According to the observation under optical microscope, scanning electron microscope and electron probe analysis, the typical filaments formed by bacterial interaction in the sample were identified, and the competitive mechanism between biological and abiotic interactions in the formation of Si-Fe-Mn oxide was discussed. The precipitation of amorphous silicon was analyzed. The samples are of complex origin, mainly hydrothermal origin, but less affected by seawater. There are almost no contributions from deep-sea pelagic sediments and pyroclastic materials. Sr and Nd isotopic compositions have two end-member material sources. The content of Sr contributed by seawater to the sample was 76.7% and 83.1% of the total. The Nd of all samples was mainly from hydrothermal fluid and kept hydrothermal information. The variation range of Pb isotopic composition was relatively small, mainly from the basement rocks of the East Manus basin. The thermodynamic diagram shows that when the temperature is reduced to 25 掳C, the main types of Si,Fe,Mn oxides formed from hydrothermal fluids are SiO2,Fe (OH) _ 3 Fe _ 3, (OH) _ 8, mn _ 3O _ 4 and mn _ 2O _ 3. In the process of mixing hydrothermal fluid with seawater, SiO2 precipitates before the formation of Fe-Mn oxides due to the lower boundary of the stable region of SiO2. Then Fe (OH) 2 precipitated, Fe3 (OH) 8 and Fe (OH) 3 precipitated, and Mn3O4 and Mn2O3 finally precipitated. The inorganic oxidation rate of Fe2 to Fe3 in the PACMANUS hydrothermal region is calculated to be 0.012 g / min, and about 3.2 kg iron oxides will be formed around the nozzle within one year. The reticular filament structure is the result of biological action. This loose structure not only guarantees sufficient supply of Fe2, but also prevents the damage of excessive oxygen in seawater, and provides a good environment for the survival of neutral iron oxidizing bacteria. At the same time, biological action and abiotic action maintain the role of competition and mutual promotion. The precipitation process of silica in the sample is divided into two stages. The first stage is the growth of silica in the filamentous structure rich in Fe, which is basically composed of filamentous structures. When the filaments rich in Fe and Si are formed into shells, the second stage silica will appear. At this stage, the size of the filaments increases and a large number of aggregates of Fe,Si rich spherical structures begin to precipitate around the filaments.
【学位授予单位】：中国科学院研究生院(海洋研究所)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P736.3
【参考文献】
相关期刊论文 前2条
1 姜学钧;林学辉;姚德;郭卫东;;稀土元素在水成型海洋铁锰结壳中的富集特征及机制[J];中国科学:地球科学;2011年02期
2 曾志刚;陈帅;王晓媛;欧阳荷根;殷学博;李兆学;;东马努斯海盆PACMANUS热液区Si-Fe-Mn羟基氧化物的矿物学和微形貌特征[J];中国科学:地球科学;2013年01期
，本文编号：2306631
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